APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of U.S. Provisional Patent Application No. 63/032,935, which was filed on June 1 , 2020, and which is incorporated herein in its entirety by reference.

TECHNICAL FIELD

[0002] The description herein relates generally to a cleaning tool and method for cleaning a portion of a lithography apparatus.

BACKGROUND

[0003] A lithography (e.g., projection) apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device (e.g., a mask) may contain or provide a pattern corresponding to an individual layer of the IC (“design layout”), and this pattern can be transferred onto a target portion (e.g. comprising one or more dies) on a substrate (e.g., silicon wafer) that has been coated with a layer of radiation-sensitive material (“resist”), by methods such as irradiating the target portion through the pattern on the patterning device. In general, a single substrate contains a plurality of adjacent target portions to which the pattern is transferred successively by the lithographic projection apparatus, one target portion at a time. In one type of lithographic projection apparatus, the pattern on the entire patterning device is transferred onto one target portion in one operation. Such an apparatus is commonly referred to as a stepper. In an alternative apparatus, commonly referred to as a step-and-scan apparatus, a projection beam scans over the patterning device in a given reference direction (the “scanning” direction) while synchronously moving the substrate parallel or anti-parallel to this reference direction. Different portions of the pattern on the patterning device are transferred to one target portion progressively. Since, in general, the lithographic projection apparatus will have a reduction ratio M (e.g., 4), the speed F at which the substrate is moved will be 1/M times that at which the projection beam scans the patterning device. More information with regard to lithographic devices as described herein can be gleaned, for example, from US 6,046,792, incorporated herein by reference.

[0004] Prior to transferring the pattern from the patterning device to the substrate, the substrate may undergo various procedures, such as priming, resist coating and a soft bake. After exposure, the substrate may be subjected to other procedures (“post-exposure procedures”), such as a post-exposure bake (PEB), development, a hard bake and measurement/inspection of the transferred pattern. This array of procedures is used as a basis to make an individual layer of a device, e.g., an IC. The substrate may then undergo various processes such as etching, ion-implantation (doping), metallization, oxidation, chemical mechanical polishing, etc., all intended to finish an individual layer of the device. If several layers are required in the device, then the whole procedure, or a variant thereof, is repeated for each layer. Eventually, a device will be present in each target portion on the substrate. These devices are then separated from one another by a technique such as dicing or sawing, whence the individual devices can be mounted on a carrier, connected to pins, etc.

[0005] Manufacturing devices, such as semiconductor devices, typically involves processing a substrate (e.g., a semiconductor wafer) using a number of fabrication processes to form various features and multiple layers of the devices. Such layers and features are typically manufactured and processed using, e.g., deposition, lithography, etch, chemical mechanical polishing, ion implantation, and/or other processes. Multiple devices may be fabricated on a plurality of dies on a substrate and then separated into individual devices. This device manufacturing process may be considered a patterning process. A patterning process involves a patterning step, such as optical and/or nanoimprint lithography using a patterning device in a lithographic apparatus, to transfer a pattern on the patterning device to a substrate and typically, but optionally, involves one or more related pattern processing steps, such as resist development by a development apparatus, baking of the substrate using a bake tool, etching using the pattern using an etch apparatus, etc. One or more metrology processes are typically involved in the patterning process.

[0006] Lithography is a step in the manufacturing of device such as ICs, where patterns formed on substrates define functional elements of the devices, such as microprocessors, memory chips, etc. Similar lithographic techniques are also used in the formation of flat panel displays, micro-electro mechanical systems (MEMS) and other devices.

[0007] As semiconductor manufacturing processes continue to advance, the dimensions of functional elements have continually been reduced while the number of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as “Moore’s law”. At the current state of technology, layers of devices are manufactured using lithographic projection apparatuses that project a design layout onto a substrate using illumination from a deep-ultraviolet illumination source, creating individual functional elements having dimensions well below 100 nm, i.e. less than half the wavelength of the radiation from the illumination source (e.g., a 193 nm illumination source).

[0008] This process in which features with dimensions smaller than the classical resolution limit of a lithographic projection apparatus are printed, is commonly known as low-ki lithography, according to the resolution formula CD = kixk/NA, where l is the wavelength of radiation employed (currently in most cases 248nm or 193nm), NA is the numerical aperture of projection optics in the lithographic projection apparatus, CD is the “critical dimension”-generally the smallest feature size printed-and ki is an empirical resolution factor. In general, the smaller ki the more difficult it becomes to reproduce a pattern on the substrate that resembles the shape and dimensions planned by a designer in order to achieve particular electrical functionality and performance. To overcome these difficulties, sophisticated fine- tuning steps are applied to the lithographic projection apparatus, the design layout, or the patterning device. These include, for example, but not limited to, optimization of NA and optical coherence settings, customized illumination schemes, use of phase shifting patterning devices, optical proximity correction (OPC, sometimes also referred to as “optical and process correction”) in the design layout, or other methods generally defined as “resolution enhancement techniques” (RET). The term “projection optics” as used herein should be broadly interpreted as encompassing various types of optical systems, including refractive optics, reflective optics, apertures and catadioptric optics, for example. The term “projection optics” may also include components operating according to any of these design types for directing, shaping or controlling the projection beam of radiation, collectively or singularly. The term “projection optics” may include any optical component in the lithographic projection apparatus, no matter where the optical component is located on an optical path of the lithographic projection apparatus. Projection optics may include optical components for shaping, adjusting and/or projecting radiation from the source before the radiation passes the patterning device, and/or optical components for shaping, adjusting and/or projecting the radiation after the radiation passes the patterning device. The projection optics generally exclude the source and the patterning device.

SUMMARY

[0009] According to an embodiment, there is provided a cleaning tool for cleaning a portion of a lithography apparatus. The cleaning tool includes a body configured to be inserted into the lithography apparatus; and a cleaning film, a first side of the cleaning film being configured to attach to a surface of the cleaning tool and a second side of the cleaning film being at least partially covered by a cleaning material, the second side being opposite to the first side. The cleaning film is configured to prevent the cleaning material from contacting the surface of the cleaning tool, and the cleaning material is configured to clean, upon contact, the portion of the lithography apparatus.

[0010] According to another embodiment, there is provided a method for cleaning a portion of a lithography apparatus with a cleaning tool for cleaning a portion of a lithography apparatus. The cleaning tool includes a body configured to be inserted into the lithography apparatus; and a cleaning film, a first side of the cleaning film being configured to attach to a surface of the cleaning tool and a second side of the cleaning film being at least partially covered by a cleaning material, the second side being opposite to the first side. The cleaning film comprises a transparent portion through which one or more features on the surface of the cleaning tool are readable, and the cleaning material is configured to clean, upon contact, the portion of the lithography apparatus.

[0011] According to an embodiment, there is provided a method for cleaning a portion of a lithography apparatus with a cleaning tool comprising one or more cleaning films. The method including: inserting, via a tool handler, the cleaning tool into the lithography apparatus; contacting, via the tool handler, the one or more cleaning films of the cleaning tool with the portion of the lithography apparatus to be cleaned; and cleaning, via the tool handler, the portion of the lithography apparatus with the one or more cleaning films of the cleaning tool. The cleaning step includes moving the cleaning tool relative to the portion of the lithography apparatus for a specified scrub time or cycles.

[0012] According to another embodiment, there is provided a computer program product comprising a non-transitory computer readable medium having instructions recorded thereon, the instructions when executed by a computer implementing any of the methods described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0014] Fig. 1 schematically depicts a lithography apparatus, according to an embodiment.

[0015] Fig. 2 schematically depicts an embodiment of a lithographic cell or cluster, according to an embodiment.

[0016] Fig. 3A illustrates a lithographic apparatus including a cleaning tool, a reticle handler turret gripper, reticle stage reticle clamps, and/or other components, according to an embodiment.

[0017] Fig. 3B is an enlarged view of a portion of the lithographic apparatus shown in Fig. 3A, according to an embodiment.

[0018] Fig. 4 illustrates overhead views of a reticle stage, reticle clamps, and/or associated membranes, according to an embodiment.

[0019] Figs. 5 A and 5B illustrate different types of contaminants (e.g., Chrome particles from a reticle, hard particles such as molybdenium silicide (MoSE) on the membranes of the reticle clamp, according to an embodiment.

[0020] Fig. 5C illustrates a cracked membrane that is cracked due to contaminants deposited on the membrane that was not cleaned, according to an embodiment.

[0021] Fig. 6 illustrates an example of a body of the cleaning tool (e.g., reticle), according to an embodiment.

[0022] Fig. 7 illustrates an example of the cleaning tool (e.g., reticle) with a film attached to the body of the cleaning tool, the film to be used for cleaning a portion of the lithography apparatus (e.g., membrane), according to an embodiment.

[0023] Fig. 8 illustrates an example structure of the film, according to an embodiment.

[0024] Fig. 9 is a flow chart of a method for cleaning a portion of a lithography apparatus, according to an embodiment.

[0025] Fig. 10 illustrate example bodies of two cleaning tools, a first set of cleaning strips, and a second set of cleaning strips, according to an embodiment.

[0026] Fig. 11 A illustrate a first cleaning tool attached with the first set of cleaning strips carrying a first cleaning material, the first tool is used for a specified dwell time, according to an embodiment.

[0027] Fig. 1 IB illustrate a second cleaning tool attached with the second set of cleaning strips carrying a second cleaning material, the second tool is used for a specified scrub time, according to an embodiment.

[0028] Fig. 12 is a block diagram of an example computer system, according to an embodiment.

[0029] Fig. 13 is a schematic diagram of a lithographic projection apparatus similar to Fig. 1, according to an embodiment.

DETAILED DESCRIPTION

[0030] In general, a mask or reticle may be a transparent block of material that is covered with a pattern defined by a different, opaque material. Various masks are fed into a lithographic apparatus and used to form layers of a semiconductor device. The pattern defined on a given mask or reticle corresponds to features produced in one or more layers of the semiconductor device. Often, a plurality of masks or reticles are automatically fed into a lithographic apparatus during manufacturing and used to form corresponding layers of a semiconductor device. Clamps (e.g., reticle stage reticle clamps) in the lithographic apparatus are used to secure the masks or reticles during processing. These clamps need periodic cleaning. Typically, cleaning requires stopping the lithographic apparatus and the manufacturing process. The cleaning is performed manually by a technician and requires several hours to complete. [0031] Advantageously, the present systems and methods provide a cleaning tool configured to be used to clean the clamps and/or associated membranes of a lithographic apparatus in-situ, while the lithographic apparatus continues to operate. The clamps comprise several components that are configured to support and provide a connection to a chuck body. The membranes are the portions of the clamps that are in contact with a reticle. The cleaning tool is configured to be automatically inserted into, and handled by, the lithographic apparatus just as any other mask or reticle is automatically inserted into, and handled by, the lithographic apparatus. Cleaning the lithographic apparatus with the present cleaning tool saves hours of downtime associated with prior cleaning methods. In addition, in some embodiments, the present system is configured to avoid contaminating other parts of the lithographic apparatus (e.g., a reticle handler robot gripper) with material removed from the cleaned (reticle stage reticle) clamps and/or their associated membranes, as described below.

[0032] In some embodiments, the cleaning tool comprises a cleaning reticle configured with an internal illumination source. The illumination source is configured to illuminate internal cleaning reticle identification features. The identification features are used by a camera of the lithographic apparatus to identify and track the position of the cleaning reticle. Advantageously, the illumination source and the internal identification features allow cleaning material to fully cover a cleaning surface of the cleaning reticle, without obscuring the identification features from the camera. In addition, an outer surface of the cleaning reticle opposite the cleaning surface may remain smooth for gripping by the lithographic apparatus.

[0033] Although specific reference may be made in this text to the manufacture of integrated circuits (ICs), it should be understood that the description herein has many other possible applications. For example, it may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle”, “wafer” or “die” in this text should be considered as interchangeable with the more general terms “mask”, “substrate” and “target portion”, respectively. In addition, any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

[0034] As an introduction, Fig. 1 schematically depicts an embodiment of a lithographic apparatus LA that may be included in and/or associated with the present systems and/or methods. The apparatus comprises: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation, DUV radiation, or EUV radiation); a support structure (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and connected to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters; a substrate table (e.g. a wafer table) WT (e.g., WTa, WTb or both) configured to hold a substrate (e.g. a resist-coated wafer) W and coupled to a second positioner PW configured to accurately position the substrate in accordance with certain parameters; and a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. comprising one or more dies and often referred to as fields) of the substrate W. The projection system is supported on a reference frame (RF).

[0035] As depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask).

[0036] The illuminator IL receives a beam of radiation from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD comprising for example suitable directing mirrors and/or a beam expander. In other cases, the source may be an integral part of the apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0037] The illuminator IL may alter the intensity distribution of the beam. The illuminator may be arranged to limit the radial extent of the radiation beam such that the intensity distribution is non-zero within an annular region in a pupil plane of the illuminator IL. Additionally or alternatively, the illuminator IL may be operable to limit the distribution of the beam in the pupil plane such that the intensity distribution is non-zero in a plurality of equally spaced sectors in the pupil plane. The intensity distribution of the radiation beam in a pupil plane of the illuminator IL may be referred to as an illumination mode.

[0038] The illuminator IL may comprise adjuster AD configured to adjust the (angular / spatial) intensity distribution of the beam. Generally, at least the outer and/or inner radial extent (commonly referred to as s-outer and s-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. The illuminator IL may be operable to vary the angular distribution of the beam. For example, the illuminator may be operable to alter the number, and angular extent, of sectors in the pupil plane wherein the intensity distribution is non-zero. By adjusting the intensity distribution of the beam in the pupil plane of the illuminator, different illumination modes may be achieved. For example, by limiting the radial and angular extent of the intensity distribution in the pupil plane of the illuminator IL, the intensity distribution may have a multi-pole distribution such as, for example, a dipole, quadrupole or hexapole distribution. A desired illumination mode may be obtained, e.g., by inserting an optic which provides that illumination mode into the illuminator IL or using a spatial light modulator.

[0039] The illuminator IL may be operable to alter the polarization of the beam and may be operable to adjust the polarization using adjuster AD. The polarization state of the radiation beam across a pupil plane of the illuminator IL may be referred to as a polarization mode. The use of different polarization modes may allow greater contrast to be achieved in the image formed on the substrate W. The radiation beam may be unpolarized. Alternatively, the illuminator may be arranged to linearly polarize the radiation beam. The polarization direction of the radiation beam may vary across a pupil plane of the illuminator IL. The polarization direction of radiation may be different in different regions in the pupil plane of the illuminator IL. The polarization state of the radiation may be chosen in dependence on the illumination mode. For multi-pole illumination modes, the polarization of each pole of the radiation beam may be generally perpendicular to the position vector of that pole in the pupil plane of the illuminator IL. For example, for a dipole illumination mode, the radiation may be linearly polarized in a direction that is substantially perpendicular to a line that bisects the two opposing sectors of the dipole. The radiation beam may be polarized in one of two different orthogonal directions, which may be referred to as X- polarized and Y-polarized states. For a quadrupole illumination mode, the radiation in the sector of each pole may be linearly polarized in a direction that is substantially perpendicular to a line that bisects that sector. This polarization mode may be referred to as XY polarization. Similarly, for a hexapole illumination mode the radiation in the sector of each pole may be linearly polarized in a direction that is substantially perpendicular to a line that bisects that sector. This polarization mode may be referred to as TE polarization.

[0040] In addition, the illuminator IL generally comprises various other components, such as an integrator IN and a condenser CO. The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation. Thus, the illuminator provides a conditioned beam of radiation B, having a desired uniformity and intensity distribution in its cross section.

[0041] The support structure MT supports the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure may use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device.

The support structure may be a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system.

[0042] The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a pattern in a target portion of the substrate. In an embodiment, a patterning device is any device that can be used to impart a radiation beam with a pattern in its cross- section to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in a target portion of the device, such as an integrated circuit. [0043] A patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase-shift, and attenuated phase-shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam, which is reflected by the mirror matrix.

[0044] The term “projection system” used herein should be broadly interpreted as encompassing any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system”.

[0045] The projection system PS has an optical transfer function which may be non-uniform, which can affect the pattern imaged on the substrate W. For unpolarized radiation such effects can be fairly well described by two scalar maps, which describe the transmission (apodization) and relative phase (aberration) of radiation exiting the projection system PS as a function of position in a pupil plane thereof. These scalar maps, which may be referred to as the transmission map and the relative phase map, may be expressed as a linear combination of a complete set of basis functions. A convenient set is the Zernike polynomials, which form a set of orthogonal polynomials defined on a unit circle. A determination of each scalar map may involve determining the coefficients in such an expansion. Since the Zernike polynomials are orthogonal on the unit circle, the Zernike coefficients may be determined by calculating the inner product of a measured scalar map with each Zernike polynomial in turn and dividing this by the square of the norm of that Zernike polynomial.

[0046] The transmission map and the relative phase map are field and system dependent. That is, in general, each projection system PS will have a different Zernike expansion for each field point (i.e. for each spatial location in its image plane). The relative phase of the projection system PS in its pupil plane may be determined by projecting radiation, for example from a point-like source in an object plane of the projection system PS (i.e. the plane of the patterning device MA), through the projection system PS and using a shearing interferometer to measure a wavefront (i.e. a locus of points with the same phase). A shearing interferometer is a common path interferometer and therefore, advantageously, no secondary reference beam is required to measure the wavefront. The shearing interferometer may comprise a diffraction grating, for example a two dimensional grid, in an image plane of the projection system (i.e. the substrate table WTa or WTb) and a detector arranged to detect an interference pattern in a plane that is conjugate to a pupil plane of the projection system PS. The interference pattern is related to the derivative of the phase of the radiation with respect to a coordinate in the pupil plane in the shearing direction. The detector may comprise an array of sensing elements such as, for example, charge coupled devices (CCDs).

[0047] The projection system PS of a lithography apparatus may not produce visible fringes and therefore the accuracy of the determination of the wavefront can be enhanced using phase stepping techniques such as, for example, moving the diffraction grating. Stepping may be performed in the plane of the diffraction grating and in a direction perpendicular to the scanning direction of the measurement. The stepping range may be one grating period, and at least three (uniformly distributed) phase steps may be used. Thus, for example, three scanning measurements may be performed in the y-direction, each scanning measurement being performed for a different position in the x-direction. This stepping of the diffraction grating effectively transforms phase variations into intensity variations, allowing phase information to be determined. The grating may be stepped in a direction perpendicular to the diffraction grating (z direction) to calibrate the detector.

[0048] The diffraction grating may be sequentially scanned in two perpendicular directions, which may coincide with axes of a co-ordinate system of the projection system PS (x and y) or may be at an angle such as 45 degrees to these axes. Scanning may be performed over an integer number of grating periods, for example one grating period. The scanning averages out phase variation in one direction, allowing phase variation in the other direction to be reconstructed. This allows the wavefront to be determined as a function of both directions.

[0049] The transmission (apodization) of the projection system PS in its pupil plane may be determined by projecting radiation, for example from a point-like source in an object plane of the projection system PS (i.e. the plane of the patterning device MA), through the projection system PS and measuring the intensity of radiation in a plane that is conjugate to a pupil plane of the projection system PS, using a detector. The same detector as is used to measure the wavefront to determine aberrations may be used.

[0050] The projection system PS may comprise a plurality of optical (e.g., lens) elements and may further comprise an adjustment mechanism configured to adjust one or more of the optical elements to correct for aberrations (phase variations across the pupil plane throughout the field). To achieve this, the adjustment mechanism may be operable to manipulate one or more optical (e.g., lens) elements within the projection system PS in one or more different ways. The projection system may have a co-ordinate system wherein its optical axis extends in the z direction. The adjustment mechanism may be operable to do any combination of the following: displace one or more optical elements; tilt one or more optical elements; and/or deform one or more optical elements. Displacement of an optical element may be in any direction (x, y, z or a combination thereof). Tilting of an optical element is typically out of a plane perpendicular to the optical axis, by rotating about an axis in the x and/or y directions although a rotation about the z axis may be used for a non-rotationally symmetric aspherical optical element. Deformation of an optical element may include a low frequency shape (e.g. astigmatic) and/or a high frequency shape (e.g. free form aspheres). Deformation of an optical element may be performed for example by using one or more actuators to exert force on one or more sides of the optical element and/or by using one or more heating elements to heat one or more selected regions of the optical element. In general, it may not be possible to adjust the projection system PS to correct for apodization (transmission variation across the pupil plane). The transmission map of a projection system PS may be used when designing a patterning device (e.g., mask) MA for the lithography apparatus LA. Using a computational lithography technique, the patterning device MA may be designed to at least partially correct for apodization.

[0051] The lithographic apparatus may be of a type having two (dual stage) or more tables (e.g., two or more substrate tables WTa, WTb, two or more patterning device tables, a substrate table WTa and a table WTb below the projection system without a substrate that is dedicated to, for example, facilitating measurement, and/or cleaning, etc.). In such “multiple stage” machines, the additional tables may be used in parallel, or preparatory steps may be carried out on one or more tables while one or more other tables are being used for exposure. For example, alignment measurements using an alignment sensor AS and/or level (height, tilt, etc.) measurements using a level sensor LS may be made.

[0052] The lithographic apparatus may also be of a type wherein at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, e.g. water, to fill a space between the projection system and the substrate. An immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the patterning device and the projection system. Immersion techniques are well known in the art for increasing the numerical aperture of projection systems. The term “immersion” as used herein does not mean that a structure, such as a substrate, must be submerged in liquid, but rather only means that liquid is located between the projection system and the substrate during exposure.

[0053] In operation of the lithographic apparatus, a radiation beam is conditioned and provided by the illumination system IL. The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF (e.g. an interferometric device, linear encoder, 2-D encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in Fig. 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the support structure MT may be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT may be realized using a long-stroke module and a short- stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected to a short-stroke actuator only, or may be fixed. Patterning device MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks PI, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0054] The depicted apparatus may be used in at least one of the following modes: 1. In step mode, the support structure MT and the substrate table WT are kept essentially stationary, while a pattern imparted to the radiation beam is projected onto a target portion C at one time (i.e. a single static exposure). The substrate table WT is then shifted in the X and/or Y direction so that a different target portion C can be exposed. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure. 2. In scan mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (i.e. a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure MT may be determined by the (de-) magnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion. 3. In another mode, the support structure MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is employed, and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

[0055] Combinations and/or variations on the above-described modes of use or entirely different modes of use may also be employed.

[0056] The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist) or a metrology or inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already includes multiple processed layers.

[0057] The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) or deep ultraviolet (DUV) radiation (e.g. having a wavelength of 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[0058] Various patterns on or provided by a patterning device may have different process windows i.e., a space of processing variables under which a pattern will be produced within specification.

Examples of pattern specifications that relate to potential systematic defects include checks for necking, line pull back, line thinning, CD, edge placement, overlapping, resist top loss, resist undercut and/or bridging. The process window of the patterns on a patterning device or an area thereof may be obtained by merging (e.g., overlapping) process windows of each individual pattern. The boundary of the process window of a group of patterns comprises boundaries of process windows of some of the individual patterns. In other words, these individual patterns limit the process window of the group of patterns.

These patterns can be referred to as “hot spots” or “process window limiting patterns (PWLPs),” which are used interchangeably herein. When controlling a part of a patterning process, it is possible and economical to focus on the hot spots. When the hot spots are not defective, it is most likely that other patterns are not defective.

[0059] As shown in Fig. 2, the lithographic apparatus LA may form part of a lithographic cell LC, also sometimes referred to a lithocell or cluster, which also includes apparatuses to perform pre- and post exposure processes on a substrate. Conventionally these include one or more spin coaters SC to deposit one or more resist layers, one or more developers to develop exposed resist, one or more chill plates CH and/or one or more bake plates BK. A substrate handler, or robot, RO picks up one or more substrates from input/output port I/Ol, 1/02, moves them between the different process apparatuses and delivers them to the loading bay LB of the lithographic apparatus. These apparatuses, which are often collectively referred to as the track, are under the control of a track control unit TCU which is itself controlled by the supervisory control system SCS, which also controls the lithographic apparatus via lithography control unit LACU. Thus, the different apparatuses can be operated to maximize throughput and processing efficiency.

[0060] In order that a substrate that is exposed by the lithographic apparatus is exposed correctly and consistently and/or in order to monitor a part of the patterning process (e.g., a device manufacturing process) that includes at least one pattern transfer step (e.g., an optical lithography step), it is desirable to inspect a substrate or other object to measure or determine one or more properties such as alignment, overlay (which can be, for example, between structures in overlying layers or between structures in a same layer that have been provided separately to the layer by, for example, a double patterning process), line thickness, critical dimension (CD), focus offset, a material property, etc. For example, contamination on reticle clamps (e.g., as described herein) may adversely affect overlay because clamping a reticle over such contamination will distort the reticle. Accordingly, a manufacturing facility in which lithocell LC is located also typically includes a metrology system that measures some or all of the substrates W (Fig. 1) that have been processed in the lithocell or other objects in the lithocell. The metrology system may be part of the lithocell LC, for example it may be part of the lithographic apparatus LA (such as alignment sensor AS (Fig. 1)).

[0061] The one or more measured parameters may include, for example, alignment, overlay between successive layers formed in or on the patterned substrate, critical dimension (CD) (e.g., critical linewidth) of, for example, features formed in or on the patterned substrate, focus or focus error of an optical lithography step, dose or dose error of an optical lithography step, optical aberrations of an optical lithography step, etc. This measurement may be performed on a target of the product substrate itself and/or on a dedicated metrology target provided on the substrate. The measurement can be performed after-development of a resist but before etching, after-etching, after deposition, and/or at other times. [0062] There are various techniques for making measurements of the structures formed in the patterning process, including the use of a scanning electron microscope, an image-based measurement tool and/or various specialized tools. As discussed above, a fast and non-invasive form of specialized metrology tool is one in which a beam of radiation is directed onto a target on the surface of the substrate and properties of the scattered (diffracted/reflected) beam are measured. By evaluating one or more properties of the radiation scattered by the substrate, one or more properties of the substrate can be determined. This may be termed diffraction-based metrology. One such application of this diffraction- based metrology is in the measurement of feature asymmetry within a target. This can be used as a measure of overlay, for example, but other applications are also known. For example, asymmetry can be measured by comparing opposite parts of the diffraction spectrum (for example, comparing the -1st and +l ^st orders in the diffraction spectrum of a periodic grating). This can be done as described above and as described, for example, in U.S. patent application publication US 2006-066855, which is incorporated herein in its entirety by reference. Another application of diffraction-based metrology is in the measurement of feature width (CD) within a target.

[0063] Thus, in a device fabrication process (e.g., a patterning process, a lithography process, etc.), a substrate or other objects may be subjected to various types of measurement during or after the process. The measurement may determine whether a particular substrate is defective, may establish adjustments to the process and apparatuses used in the process (e.g., aligning two layers on the substrate or aligning the patterning device to the substrate), may measure the performance of the process and the apparatuses, or may be for other purposes. Examples of measurement include optical imaging (e.g., optical microscope), non-imaging optical measurement (e.g., measurement based on diffraction such as the ASML YieldStar metrology tool, the ASML SMASH metrology system), mechanical measurement (e.g., profiling using a stylus, atomic force microscopy (AFM)), and/or non-optical imaging (e.g., scanning electron microscopy (SEM)). The SMASH (SMart Alignment Sensor Hybrid) system, as described in U.S. Pat. No. 6,961,116, which is incorporated by reference herein in its entirety, employs a self-referencing interferometer that produces two overlapping and relatively rotated images of an alignment marker, detects intensities in a pupil plane where Fourier transforms of the images are caused to interfere, and extracts the positional information from the phase difference between diffraction orders of the two images which manifests as intensity variations in the interfered orders.

[0064] Metrology results may be provided directly or indirectly to the supervisory control system SCS. If an error is detected, an adjustment may be made to exposure of a subsequent substrate (especially if the inspection can be done soon and fast enough that one or more other substrates of the batch are still to be exposed) and/or to subsequent exposure of the exposed substrate. Also, an already exposed substrate may be stripped and reworked to improve yield, or discarded, thereby avoiding performing further processing on a substrate known to be faulty. In a case where only some target portions of a substrate are faulty, further exposures may be performed only on those target portions which meet specifications.

[0065] Within a metrology system MET, a metrology apparatus is used to determine one or more properties of the substrate, and in particular, how one or more properties of different substrates vary, or different layers of the same substrate vary from layer to layer. As noted above, the metrology apparatus may be integrated into the lithographic apparatus LA or the lithocell LC or may be a stand-alone device. [0066] To enable the metrology, one or more targets can be provided on the substrate. In an embodiment, the target is specially designed and may comprise a periodic structure. In an embodiment, the target is a part of a device pattern, e.g., a periodic structure of the device pattern. In an embodiment, the device pattern is a periodic structure of a memory device (e.g., a Bipolar Transistor (BPT), a Bit Line Contact (BLC), etc. structure).

[0067] In an embodiment, the target on a substrate may comprise one or more 1-D periodic structures (e.g., gratings), which are printed such that after development, the periodic structural features are formed of solid resist lines. In an embodiment, the target may comprise one or more 2-D periodic structures (e.g., gratings), which are printed such that after development, the one or more periodic structures are formed of solid resist pillars or vias in the resist. The bars, pillars, or vias may alternatively be etched into the substrate (e.g., into one or more layers on the substrate).

[0068] In an embodiment, one of the parameters of interest of a patterning process is overlay. Overlay can be measured using dark field scatterometry in which the zeroth order of diffraction (corresponding to a specular reflection) is blocked, and only higher orders processed. Examples of dark field metrology can be found in PCT patent application publication nos. WO 2009/078708 and WO 2009/106279, which are hereby incorporated in their entirety by reference. Further developments of the technique have been described in U.S. patent application publications US2011-0027704, US2011-0043791 and US2012- 0242970, which are hereby incorporated in their entirety by reference. Diffraction-based overlay using dark-field detection of the diffraction orders enables overlay measurements on smaller targets. These targets can be smaller than the illumination spot and may be surrounded by device product structures on a substrate. In an embodiment, multiple targets can be measured in one radiation capture.

[0069] As lithography nodes keep shrinking, more and more complicated wafer designs may be implemented. Various tools and/or techniques may be used by designers to ensure complex designs are accurately transferred to physical wafers. These tools and techniques may include mask optimization, source mask optimization (SMO), OPC, design for control, and/or other tools and/or techniques. For example, a source mask optimization process is described in United States Patent No. 9,588,438 titled “Optimization Flows of Source, Mask and Projection Optics”, which is incorporated in its entirety by reference.

[0070] The present systems, and/or methods may be used as stand-alone tools and/or techniques, and/or or used in conjunction with other semiconductor manufacturing processes, to enhance the accurate transfer of complex designs to physical wafers.

[0071] As described above, the present system includes a cleaning tool configured to be used to clean a portion of a lithographic apparatus in-situ, while the lithographic apparatus continues to operate. For example, the cleaning tool may simply replace a typical reticle inserted into the lithographic apparatus. The lithographic apparatus may move the cleaning tool through typical movements and/or positions of the replaced reticle such that the lithographic apparatus does not require special adjustments for the cleaning tool during operation. In some embodiments, the portion of the lithography apparatus to be cleaned comprises reticle stage reticle clamps, associated membranes, and/or other portions of the lithographic apparatus. The cleaning tool is configured to be automatically inserted into, and handled (e.g., moved, rotated, etc.) by, the lithographic apparatus just as any other mask or reticle is automatically inserted into, and handled by, the lithographic apparatus. Cleaning the lithographic apparatus with the present cleaning tool saves hours of downtime associated with prior cleaning methods. In addition, the present system is configured to avoid contaminating other parts of the lithographic apparatus (e.g., a reticle handler robot gripper) with material removed from the cleaned (reticle stage reticle) clamps, as described below. The cleaning tool is configured to be inserted into the lithography apparatus. In an embodiment, the cleaning tool is inserted in a container to prevent contaminants from spreading to other parts of the lithography apparatus during/after cleaning. In an embodiment, It is the cleaning tool is blocked, (e.g., via software based instructions) based on e.g., a cleaning reticle identifier (ID) from entering other parts of the reticle handler or lithography apparatus to avoid contamination of e.g., an internal reticle library (IRL) and IRIS (e.g., an automated inspection system). An example of another cleaning tool, a tool handler, and the reticle handler robot gripper are discussed in U.S. Application number 62/931,864, filed on November 7, 2019, which is incorporated herein in its entirety by reference.

[0072] By way of a non-limiting example, Fig. 3A and 3B illustrate (a portion of) a lithographic apparatus 300 (e.g., similar to or the same as the lithographic apparatus shown in Fig. 1). Fig. 3A illustrates present system 301 comprising a cleaning tool 302 and/or other components; and various components of lithographic apparatus 300 including a tool handler 306, 307, 308, reticle stage 310 reticle clamps 312 (only one side is visible in Fig. 3A), and/or other components. In an embodiment, the lithography apparatus comprise a pod configured to store one or more instances of the cleaning tool 302. For example, the pod may have a plurality of slots, each slot carrying a cleaning tool 302. In some embodiments, lithographic apparatus 300 is configured for deep ultraviolet (DUV) lithography.

[0073] In some embodiments, cleaning tool 302 comprises a cleaning reticle and/or other components. In some embodiments, tool handler 306, 307, 308 comprises a reticle handler turret gripper 306, a reticle handler robot gripper 307 (having associated clamps, etc. 308 for gripping a reticle), and/or other components. Reticle handler robot gripper 307 may, for example, move a reticle from a pod 320 (e.g., after a user places a reticle in pod 320). Tool handler 306 may, for example, move a reticle from reticle handler robot gripper 307 to reticle clamps 312. Lithographic apparatus 300 may include various other mechanical components 322 (translation mechanisms, elevation mechanisms, rotational mechanisms, motors, power generation and transmission components, structural components, etc.) configured to facilitate movement and control of cleaning tool 302 through lithographic apparatus 300. An example of tool handler is further discussed in detail in U.S. Application number 62/931,864, filed on November 7, 2019, which is incorporated herein in its entirety by reference.

[0074] Cleaning tool 302 is configured to be used to clean clamps 312 and/or associated membranes (e.g., membranes of the clamps that make contact with the underside of the reticle) of lithographic apparatus 300 in-situ, while lithographic apparatus 300 continues to operate. Cleaning tool 302 is configured to be automatically inserted into, and handled by, lithographic apparatus 300 just as any other mask or reticle 316 is automatically inserted into, and handled by, lithographic apparatus 300. For example, cleaning tool 302 is sized and shaped to be inserted into lithographic apparatus 300 at a typical insertion point 318 using a typical insertion method, just as any other reticle 316 would be inserted into apparatus 300.

[0075] Fig. 3B is an enlarged view of a portion of apparatus 300. Fig. 3B shows cleaning tool 302 tool handler 306, reticle stage 310, reticle stage reticle clamps 312 (only one side is visible in Fig. 3B), mechanical components 322, reticle handler robot gripper 307, and/or other components. As shown in Fig. 3B, tool handler 306 is configured to move cleaning tool 302 from reticle handler robot gripper 307 to reticle stage 310 reticle clamps 312 so cleaning tool 302 can be used to clean clamps 312 in situ. Moving cleaning tool 302 may comprise moving cleaning tool toward or away from clamps 312 in horizontal, vertical, and/or other directions. Tool handler 306 and/or reticle handler robot gripper 307 may include various motors, translators, rotational components, clamps, clips, power sources, power transmission components, vacuum mechanisms, and/or other components that facilitate the movement of cleaning tool 302.

[0076] Fig. 4 illustrates overhead views of a reticle stage 310, reticle clamps 312, and/or associated membranes 410, according to an embodiment. In some embodiments, clamps 312 and/or associated membranes 410 may be the target surfaces cleaned by cleaning tool 302, for example. Typically, the membranes 410 are in contact with the bottom of a reticle, in the areas where a barcode (and/or other identification data) is printed. The printing is applied with chrome, MoSi, or other materials. When the reticle is clamped via vacuum and then scanned (e.g., for identification purposes), the high contact pressure can initiate molecular level bonding between the reticle material and the clamp 312 material. When separated, small portions of the reticle material are pulled out and remain on the surface of the membrane 410. Flence the need for cleaning. In practice, reticle handler turret gripper 306 (not shown in Fig. 4) would lower (e.g., into the page) cleaning tool (reticle) 302 over clamps 312, associated membranes 410.

[0077] In an embodiment, the reticle clamping mechanism can be a vacuum clamp, an electrostatic clamp, or other known clamping mechanisms. In a vacuum clamp mechanism, the membranes 410 may include vacuum pads 415 at one or more locations on the surface of the membrane 410. When a reticle R1 is clamped, the reticle R1 makes direct contact with and sitting on these vacuum pads 415. When the reticle R1 contacts and then removed, reticle material may be deposited on the vacuum pads 415. The vacuum pads 415 have a nano-bump topography, or nano-bump or nano-wave topography, as shown in the enlarged view, but at the nano scale. In an embodiment, the nano-bump topography is placed to avoid optical contacting issue that arises when two very, very flat surfaces contact each other. The optical contacting causes the surfaces to stick together and optically contact. Such optical contact or optical bonding is not desired between the reticle R1 and reticle clamps and/or associated membranes. Flowever, such nano-bumps results in increased contact stress. So, when the reticle is clamped with the little nano bump or nano-wave pattern of the vacuum pads 415, there is an increased contact stress due to less area. This contact stress causes transfer of chrome coating on the body of the cleaning tool to the vacuum pads 415. In an embodiment, the cleaning tool 302 can be configured as discussed herein, to clean the Chrome contamination. However, the present disclosure is not limited to cleaning a particular contaminants. Based on the contaminants to be cleaned, the cleaning tool 302, particularly film (e.g., FI and F2 in Fig. 7) can be configured with cleaning solutions, and used in an automatic cleaning process (e.g., in Fig. 9).

[0078] In an embodiment, the cleaner material on the cleaning tool 302 (e.g., shown in Fig. 7) contacts with the clamps 312 and/or membranes 410, or vacuum pads 415 located on the membranes 410. Further, the cleaning tool 302 can be configured to move (e.g., using the tool handler) in a single dimension (e.g., an “x” or horizontal dimension according to the orientation of Fig. 4) to perform the cleaning of the vacuum pads 415. However, in some embodiments, the cleaning tool 302 may be configured to move in more than one dimension (e.g., in “x” and “y” dimensions) to appropriately engage target cleaning surfaces.

[0079] Figs. 5A and 5B illustrate different types of contaminants deposited on the pads 415. The contaminants can be e.g., Chrome particles (e.g., white particles in Fig. 5A) from the reticle, hard particles such as molybdenium disilicide (MoSF) (e.g., white particles in Fig. 5B) on the membranes of the reticle clamp, according to an embodiment. In an embodiment, the contaminants such as hard particles that are large enough e.g., 5 to 10 micron in size may cause overlay errors in a substrate printed using the lithography apparatus discussed herein, and further overlay degradation upon repeated printing process. [0080] In an embodiment, when the contaminants stay on the membranes 410 or pads 415 thereon, the reticle may stick to the membranes 410 and/or pads 415 and cause a cracked membrane. Fig. 5C illustrates an example of cracked membrane 410 that is cracked at CRK1, CRK2 and CRK3 due to contaminants deposited on the vacuum pads that were not cleaned between repeated use of reticles during the patterning process, according to an embodiment. Fig. 5C also shows a vacuum hole 420 in the membrane 410 that is used during clamping the reticle placed on the pads 415. To avoid the contamination related issues, typically manual membrane cleaning is performed that may cost at least four plus hours of downtime and substantial costs. The present cleaning tool 302 automates the cleaning process and can reduce the downtime to less than 20 mins. The cleaning tool 302 and its various features that enable the automation are discussed in detail below that will reduce downtime and increase availability of the lithography apparatus.

[0081] Fig. 6 and 7 illustrate an example of a body 302’ of cleaning tool (e.g., reticle) 302 and the cleaning tool 302 with a film carrying a cleaner material can be attached. In an example, a side of the body 302’at which the film (e.g., FI and F2 in Fig. 7) with the cleaner material is attached may be referred as a cleaning surface. In an embodiment, the body 302’ of the cleaning tool 302 is a single block of material shaped as a rectangular prism. This is not intended to be limiting. The principles and/or features described below may be applied to the embodiments of cleaning tool 302 shown in Fig. 3 A, 3B, 4, and 7-1 IB, and/or may be included in a separate embodiment of cleaning tool 302.

[0082] In some embodiments, one or more portions of the cleaning tool 302 may be formed from transparent or nearly transparent material such as ultra-low thermal-expansion quartz (SFS) and/or other materials. However, this requirement is for use in lithography. Fabrication of cleaning reticle (tool) 302 can utilize any number of materials, providing the external dimension and mass conform to the "SEMI standard PI for Hard Surface Photomask Substrates." In some embodiments, the cleaning tool 302 (as shown in Fig. 6) comprises a cleaning surface 1100 (bottom Bl) at which the film (e.g., see FI and F2 in Fig. 7 and 8) carrying the cleaner material is attached, one or more side surfaces 1104, and/or other components. In some embodiments, the cleaning tool 302 also includes one or more identification features 1106, 1108. Identification features 1106 and 1108 may include pre-alignment marks 1106, a barcode 1108, and/or other identification features. In some embodiments, identification features 1106 and 1108 may be located on cleaning surface 1100 as shown in Fig. 6.

[0083] Fig. 7 illustrates an example of the cleaning tool 302 for cleaning a portion of a lithography apparatus. For example, the portion (e.g., membranes and/or vacuum pads thereon) of the reticle clamp of a reticle stage. The cleaning tool 302 is configured to be inserted into the lithography apparatus and comprises a cleaner material configured to clean a portion of the lithography apparatus upon contact therewith; and a film (e.g., FI and/or F2) carrying the cleaner material. The film is configured to attached to the body 302’ (also see Fig. 6) and prevent the cleaner material from contacting a surface of the body 302’. In an embodiment, the film (e.g., FI and/or F2) is removably attached to the surface of the cleaning tool. In an embodiment, the film (e.g., FI and/or F2) comprises a transparent portion through which one or more features on the surface of the cleaning tool are readable via an optical sensor (e.g., camera, and barcode reader). For example, the transparent portion may be a transparent tape.

[0084] Fig. 8 illustrates an example structure of the film, according to an embodiment. The film (e.g., FI) may have a single layered structure, a 2-layer structure, or a 3-layers structure. The present disclosure is not limited to a particular layered structure. In a preferred embodiment, the film FI comprises: a first layer LI at least partially covered with the cleaner material, and a second layer L3 configured to attach to the surface of the body and prevent the cleaner material from contacting the surface of the cleaning tool. The second layer L3 configured to be disposed between the first layer LI and the surface of the body of the cleaning tool 302. In an embodiment, the first layer LI material is a cleanroom microfiber wipe with features enabling efficient removal of particle contamination and enhanced absorbency of cleaning solution. Also, the first layer can be made of a material that does not release fibers, resists shedding or tearing during/after cleaning. For example, the first layer LI can be MiraWIPE®. For example, the cleaning solution applied to the first layer LI is Chromium etchant, deionized water, isopropyl alcohol, or methanol. In an embodiment, the second layer L3 is transparent to allow one or more features on the cleaning to be readable via a tool handler (or optical sensors associated with the tool handler). For example, the second layer L3 can be a clean room tape. In an embodiment, the clean room tape may be replaced with a clear (e.g., optically-transparent) protective reticle coating, instead of a Cr etchant, over a standard / default Cr reticle coating. In another embodiment, a non-chrome reticle coating may be used instead of the standard / default Cr reticle coating. In yet another embodiment, no reticle coating may be applied instead of the standard / default Cr reticle coating

[0085] In an embodiment, the film FI and/or F2 further comprises an adhesive layer L2 applied on a portion of the film. The adhesive layer L2 is provided between the first layer LI and the second layer L3. The adhesive layer L2 is at least partially covered with adhesive material on both the sides of the adhesive layer L2. The adhesive keeps the second layer L3 adhered to the first layer LI even when the film FI and/or F2 is removed from the body of the cleaning tool 302. For example, the adhesive layer L2 can be a double-sided adhesive coated layer (e.g., 3M™ Double Coated Paper Tape 410M). In an embodiment, the adhesive layer is applied uniformly under the first layer LI. Hence, during the cleaning process, the cleaner material on the first layer LI will uniformly contact with the portion being cleaned. In an embodiment, having a separate adhesive layer L2 may be preferred. Alternatively, the first layer LI may be adhesive-backed.

[0086] In an embodiment, the film include one or more cutout portions associated with one or more features of at least one of: a tool handler used to engage with the cleaning tool; one or more clamp elements at the portion of the lithography apparatus; or one or more identification features on the surface of the cleaning tool. Examples of cutout portions are further illustrated and discussed with respect to Fig. 7. In an embodiment, the one or more cutout portions are within the first layer LI (and the adhesive layer L2, in an embodiment), and not in the second layer L3. As discussed herein, the one or more identification features comprise one or both of a bar code and an alignment mark that are readable (e.g., via an optical sensor) through the second layer L3. In an embodiment, the one or more clamp elements comprise one or more vacuum holes provided on the portion of the lithography apparatus to clamp a reticle via vacuum clamps. Thus, the second layer L3 can prevent cleaning material and contaminants from contacting the cleaning tool 302 thereby preserving the bar code or identification feature from being contaminated.

[0087] In an embodiment, e.g., in Fig. 7 and 11 A-l IB, the film FI is attached over the one or more identification features at a first edge of the surface of the cleaning tool, the one or more identification features being readable (e.g., via an optical sensor) through the second layer of the film; and another of the film F2 is attached at a second edge of the surface of the cleaning tool, the second edge being distant and parallel to the first edge. [0088] Referring back to Fig. 7, the body 302’ of the cleaning tool 302 (e.g., reticle) comprises two films FI and/or F2 attached at the edges. The films FI and F2 are used for cleaning a portion of the lithography apparatus (e.g., membrane). In an embodiment, the cleaning surface 1100 of the cleaning tool 302 is partially covered by the film FI and F2 that carries the cleaning material. In some embodiments, the cleaning material comprises one or more different materials. The material used for cleaning the membranes can vary, depending on the contamination to be removed. The cleaning material is configured to contact and clean reticle stage 310 (Fig. 3A and 3B) reticle clamps 312 (Fig. 3A and 3B), and/or associated membranes as described above.

[0089] As shown in Fig. 7, the film FI and/or F2 with the cleaning material includes cutouts such as RC1, VC1, VC2, BC1, PAC1, PAC2 in the cleaning material that correspond to the locations of identification features 1106 and 1108, the tool handler gripping location, a clamp element, for example. For example, cutouts RC1 may be at the corners corresponding to the tool handler gripping location. Cutouts VC1 and VC2 correspond to vacuum holes at the membranes (e.g., 410). Cutouts BC1 correspond to a barcode. Cutout PAC1 and PAC2 correspond to position alignment marks that may be used for aligning the cleaning tool 302 with the reticle stage and/or reticle clamp. The cutouts may be created by cutting and/or otherwise removing cleaning material in the areas that correspond to the locations of identification features 1106 and 1108, the tool handler gripping locations, and the clamp element locations Cl and C2. The cutouts in the cleaning material may be left because the cleaning material is generally opaque or nearly opaque, and identification features 1106 and 1108 are configured to be read by a camera in lithographic apparatus 300 (Fig. 3A and 3B) using illumination that passes into cleaning tool 302 from the cleaning surface 1100 side of cleaning tool 302 and out of cleaning tool 302 through identification surface 1102.

[0090] In an embodiment, the cutouts RC1 (e.g., at four corners) at the corners where a tool handler interfaces prevents contamination of the tool handler. For example, the cutouts RC1 prevents Cr etchant contamination of the tool handler interface. The cutouts VC1 and VC2 corresponding to the vacuum holes at the reticle prevents e.g., Cr etchant contamination of Z-support or reticle stage chuck vacuum lines. The cutout BC1, and PAC1 and PAC2 (corresponding to identifying features such as a barcode and alignment marks on the cleaning tool) enables reticle identification (ID) and alignment to reticle stage chuck. Furthermore, as mentioned earlier, the film e.g., via the second layer L3 can prevent cleaning material, e.g., some residual chrome cleaning fluid from getting into the windows and attacking the features (e.g., bar codes, alignment features) on the surface of the cleaning tool 302. Thus, the film serves several purposes including cleaning the desired portion of the lithography apparatus, allow readability of features on the cleaning tool 302, and preventing contamination, etching, or erosion of features of the cleaning tool 302. [0091] In an embodiment, the cleaning tool 302 is configured to contact the cleaner material with a target surface (e.g. vacuum pads) of the portion of the lithography apparatus, and move relative to the portion of the lithography apparatus when cleaning the portion of the lithography apparatus by the film. In an embodiment, the film is configured to be parallel to the target surface. In an embodiment, the cleaner material on the film contacts the target portion for a specified dwell time. During the dwell time, the cleaner material stays in contact with the target portion while the tool handler is disengaged from the cleaning tool 302. In an embodiment, e.g., when vacuum clamps are used, the cleaning tool although disengaged may be vacuum-clamped to (or engaged with) a reticle handler turret gripper. As such, the target portion is exerted by only the weight of the cleaning tool and the reticle handler turret gripper that allows the cleaner material to spread over the contaminated target surface. In an embodiment, the cleaning tool 302 is configured to move relative to the target portion under weak vacuum clamping force causing the cleaning material to scrub the target portion for a specified scrub time or cycles. The cleaning tool 302 may be configured to move relative to the target portion under the weak vacuum clamping force after the cleaning tool 302 is disengaged from the reticle handler turret gripper. The tool handler 306 is configured to engage with the cleaning tool 302, and move and orient the cleaning tool 302 such that the film to face the portion of the lithography apparatus to be cleaning.

[0092] In some embodiments, the cleaning tool 302 is engaged with (e.g., vacuum-clamped to) the reticle handler turret gripper and the reticle handler gripper turret is disengaged from the tool handler while a scrubbing action is performed. For example, the reticle handler turret gripper may be configured to move relative to the target portion while the cleaning tool 302 is engaged with (e.g., vacuum-clamped to) the reticle handler turret gripper. As a result, the cleaning material scrubs the target portion under a normal force of the reticle handler turret gripper and the cleaning tool 302 due to motion of the reticle handler gripper turret. The reticle handler gripper turret may be moved back-and-forth with high acceleration and low range of motion. In some embodiments, the reticle handler gripper turret may perform the described scrubbing action without applied vacuum forces and/or without post-scrub/pre- unload reticle re-alignment. By keeping the reticle handler gripper turret engaged with the cleaning tool 302 during the described scrubbing action, problems associated with unloading the cleaning tool 302 from the reticle handler gripper turret are mitigated. The described scrubbing action may also allow scrubbing without the application of additional vacuum forces on the cleaning tool 302, resulting in a lesser normal force between the cleaning tool 302 and the target portion in some embodiments.

[0093] In an embodiment, the lithography apparatus further comprises a pod (not illustrated) configured to hold one or more cleaning tools and fit into the lithography apparatus. The cleaning tool 302 is configured to be inserted in the pod, moved from the pod by the tool handler 306 for the cleaning, and returned to the pod by the tool handler 306 after the cleaning. In an embodiment, the pod comprises a plurality of slots, each slot configured to hold a cleaning tool of the one or more cleaning tools. In an embodiment, the pod comprises a non-reactive material that does not react with the cleaner material carried on the film that is the body attached to the cleaning tool. In such an embodiment, the non-reactive material is a high density polyethylene. In an embodiment, process of cleaning can be implemented via a processor configured to operate the tool handler when operations stored in the processors are executed. In an embodiment, an example operations are discussed below.

[0094] Fig. 9 is a flow chart of a method 900 for cleaning a portion of a lithography apparatus, according to an embodiment. The method 900 may be performed with a cleaning tool 302, for example. The operations of method 900 presented below are intended to be illustrative. In an embodiment, the method 900 may be accomplished with one or more additional operations not described, and/or without one or more of the operations discussed. Additionally, the order in which the operations of method 900 are illustrated in Fig. 9 and described below is not intended to be limiting.

[0095] In some embodiments, one or more portions of method 900 may be implemented in and/or controlled by one or more processing devices (e.g., a digital processor, an analog processor, a digital circuit designed to process information, an analog circuit designed to process information, a state machine, and/or other mechanisms for electronically processing information). The one or more processing devices may include one or more devices executing some or all of the operations of method 900 in response to instructions stored electronically on an electronic storage medium. The one or more processing devices may include one or more devices configured through hardware, firmware, and/or software to be specifically designed for execution of one or more of the operations of method 900 (e.g., see discussion related to Fig. 12 below). For example, the one or more processing devices may run (e.g., ASML Twinscan) software configured to run a cleaning program that causes one or more of the operations described herein to be performed.

[0096] In an embodiment, operation P901 includes inserting, via a tool handler, the cleaning tool (e.g., the tool 302 of Fig. 7) into the lithography apparatus. In an embodiment, the lithography apparatus is configured for deep ultra violet (DUV) radiation. In an embodiment, operation P903 includes contacting, via the tool handler, the cleaner material on the one or more films with the portion of the lithography apparatus to be cleaned.

[0097] In an embodiment, operation P905 includes cleaning, via the tool handler, the portion of the lithography apparatus with cleaner material on the one or more films of the cleaning tool, the cleaning comprises moving the cleaning tool relative to the portion of the lithography apparatus for a specified scrub time or cycles.

[0098] In an embodiment, the cleaning of the portion of the lithography apparatus comprises repeatedly moving the second cleaning tool parallel to and in a back-and-forth direction with respect to the portion of the lithography apparatus. In an embodiment, the back-and-forth movement is restricted by the geometry of the portion being cleaned, or proximate distance to neighboring component. For example, the back-and-forth movement is restricted to a range ± 2mm.

[0099] In an embodiment, the cleaning operation P905 further comprises: maintaining the one or more films in contact with the portion of the lithography apparatus for a specified dwell time. During the specified dwell time, the cleaning tool is stationary. In an embodiment, during the dwell time, the cleaning tool is disengaged from the tool handler.

[00100] In an embodiment, the method 900 further comprising: selecting, based on a contaminant being cleaning, the cleaning tool from a pod, moving the cleaning tool from the pod with the tool handler for cleaning the portion of the lithography apparatus, removing the one or more films from the cleaning tool after cleaning, and returning the cleaning tool to the pod with the tool handler after the cleaning. In an embodiment, the contaminant on the portion of the lithography apparatus comprises: a first contaminant or a second contaminant deposited on the portion of the lithography apparatus. The first contaminant is for example, chrome (Cr) particles deposited on the portion of the lithography apparatus. The second contaminant is for example, hard particles, residual chromium etchant, or organic material deposited on the portion of the lithography apparatus.

[00101] When cleaning the first contaminant, the cleaning process comprises: applying an first cleaning solution as the cleaner material to the one or more films attached to a first cleaning tool; leaving the first cleaning solution in contact with the portion of the lithography apparatus for a specified dwell time, the first cleaning solution reacting with the first contaminant during the specified dwell time; removing the first cleaning tool and placing the first cleaning tool in the pod; applying a second cleaning solution as the cleaner material to the one or more films attached to a second cleaning tool; and moving the second cleaning tool relative to the portion of the lithography apparatus for a specified scrub time, while the cleaner material is in contact with the portion of the lithography apparatus. The moving of the second cleaning tool comprises moving the second cleaning tool parallel to and in a back-and-forth direction with respect to the portion of the lithography apparatus.

[00102] In an embodiment, to enable movement in the back-and-forth direction, a friction between the portion of the lithography apparatus and the cleaning material should be sufficiently low. Hence, in an embodiment, an ‘extra-weak’ vacuum (e.g., a lower vacuum level than used for gripping or clamping a reticle during pattern) may be provided. Hence, a normal force is reduced thereby reducing the friction force component at the contact between the cleaning material and the portion being cleaned. This reduced vacuum level enables parallel back-and-forth scrubbing action between the cleaning material and the portion being cleaned. In some embodiments, the ‘extra-weak’ vacuum may be removed in case of cleaning more-sensitive or delicate membranes (e.g., burled reticle stage chuck membranes). For example, the scrub action (e.g., in back and forth direction) may be performed with rip ‘extra-weak’ vacuum or at atmospheric pressure.

[00103] In some embodiments, method 900 comprises (e.g., as described above related to Figs. 6-8) providing a film on the cleaning tool (removable attached, in an embodiment) that is at least partially covered by cleaning material; providing one or more identification features on the cleaning tool; and providing the film that allows a camera to read the identification features through the film.

[00104] Fig. 10, 11A and 11B illustrate example two cleaning tools, a first set of cleaning strips, and a second set of cleaning strips, according to an embodiment. Fig. 11 A shows that the first cleaning tool A includes the first set of cleaning strips A. The first cleaning strips A carries the Cr etchant, for example to clean the Cr contaminants. According to the method 900, the tool handler may be in communication with a processor (e.g. process 104 of Fig. 12 that is configured to execute a cleaning routine/software code/operations of Fig. 9). The processor may instruct the tool handler to insert the cleaning tool A in the lithographic apparatus over the target surface (e.g., vacuum pads). The cleaning strips A are placed in contact with the target surface via the tool handler. Further, the process may instruct the tool handler to be disengaged so that the cleaning strips A stay in contact with the target surface for a specified dwell time. For example, a default dwell time can be set as 10 minutes or the dwell time can be specified in a range 7.5-12.5 minutes. Then, the tool handler may reengage and move the cleaning tool A to a pod. In an embodiment, the cleaning strips A may be removed before moving the cleaning tool A to the pod.

[00105] Further, the processor may instruct the tool handler to select the cleaning tool B. The cleaning tool B comprises the cleaning strips B carrying deionized (DI) water (or isopropyl alcohol), for example. The tool handler can then transport the cleaning tool B over the target surface and move the cleaning tool B relative to the target surface to perform scrubbing action of the target surface with the cleaning strips B for a specified scrub time. For example, a default scrub time can be set as 20 cycles or can be specified as any number of cycles in a range 0 to 50 cycles. After the scrubbing, the cleaning tool is re-aligned with e.g., reticle holder via asymmetric moves and adjustments with high or low accuracy to safely remove the cleaning tool. Thereafter, the cleaning tool can be unloaded from e.g., the reticle stage and the tool handler may return the cleaning tool to the pod. In an embodiment, the cleaning strips B may be disposed. In an embodiment, single-reticle pods may be employed such that each cleaning tool can be returned to the cleaning tool’s original pod slot after a cleaning action (e.g., after dwell, after scrub).

[00106] The cleaning tool A and B can be reused by attaching fresh cleaning strips A and B with desired cleaner material (e.g., cleaning solution) in a next cleaning process e.g., after 1 month.

[00107] In an embodiment, there is provided a computer readable medium that is configured to store instructions of method 900. These stored instructions when executed causes the cleaning tool to performed the operations of method 900, as discussed above. For example, the non-transitory computer- readable media causes cleaning related operations, when executed, to communicate with one or more systems such as tool handler, systems related to reticle handling, or other systems of the lithography apparatus.

[00108] For example, in an embodiment, a non-transitory computer-readable media comprising instructions for cleaning a portion of a lithography apparatus with a cleaning tool comprising one or more cleaning films, the instructions when executed by one or more processors, cause operations comprising: inserting, via a tool handler, the cleaning tool into the lithography apparatus; contacting, via the tool handler, the one or more cleaning films of the cleaning tool with the portion of the lithography apparatus to be cleaned; and cleaning, via the tool handler, the portion of the lithography apparatus with the one or more cleaning films of the cleaning tool, the cleaning comprises moving the cleaning tool relative to the portion of the lithography apparatus for a specified scrub time or cycles.

[00109] In an embodiment, the cleaning the portion of the lithography apparatus comprises repeatedly moving the second cleaning tool parallel to and in a back-and-forth direction with respect to the portion of the lithography apparatus. In an embodiment, the back-and-forth movement is restricted to a range +2mm. [00110] In an embodiment, the cleaning operation further includes maintaining the one or more cleaning films in contact with the portion of the lithography apparatus for a specified dwell time. In an embodiment, during the specified dwell time, the cleaning tool is stationary. In an embodiment, during the specified dwell time the cleaning tool is disengaged from the tool handler and is vacuum-clamped to the RH turret gripper.

[00111] In an embodiment, the operations further includes selecting, based on a contaminant being cleaned, the cleaning tool from a container, moving the cleaning tool from the container with the tool handler for cleaning the portion of the lithography apparatus, removing the one or more cleaning films from the cleaning tool after cleaning, and returning the cleaning tool to the container with the tool handler after the cleaning. In an embodiment, the contaminant on the portion of the lithography apparatus comprises: a first contaminant or a second contaminant deposited on the portion of the lithography apparatus. In an embodiment, the first contaminant is chrome (Cr) particles deposited on the portion of the lithography apparatus. In an embodiment, the second contaminant is hard particles, a residual chromium etchant, or organic material deposited on the portion of the lithography apparatus.

[00112] In an embodiment, when cleaning the first contaminant, the cleaning process includes applying an etchant to the one or more cleaning films attached to a first cleaning tool; leaving the one or more cleaning films in contact with the portion of the lithography apparatus for a specified dwell time, the etchant reacting with the first contaminant during the specified dwell time; removing the first cleaning tool and placing the first cleaning tool in the container; applying a cleaning solution to the one or more cleaning films attached to a second cleaning tool; and moving the second cleaning tool relative to the portion of the lithography apparatus for a specified scrub time, while the one or more cleaning films are in contact with the portion of the lithography apparatus.

[00113] In an embodiment, the instructions for the moving of the second cleaning tool includes moving the second cleaning tool parallel to and in a back-and-forth direction with respect to the portion of the lithography apparatus. In an embodiment, the moving of the second cleaning tool includes reducing a clamping force exerted on the cleaning tool by adjusting a vacuum level to allow moving of the second tool while maintaining contact between the cleaning material of the film and the portion of the lithography apparatus.

[00114] In an embodiment, the portion of the lithography apparatus comprises a reticle clamp of a reticle stage. In an embodiment, the cleaning tool comprises a cleaning reticle. In an embodiment, the non-transitory computer-readable media causes communication with the tool handler that comprises a reticle handler turret gripper. In an embodiment, the non-transitory computer-readable media is part of the lithography apparatus is configured for deep ultra violet (DUV) radiation, and configured to clean the portion of the DUV lithography apparatus.

[00115] Fig. 12 is a block diagram that illustrates a computer system 100 that can assist in implementing the methods, flows, or the system(s) disclosed herein. Computer system 100 includes a bus 102 or other communication mechanism for communicating information, and a processor 104 (or multiple processors 104 and 105) coupled with bus 102 for processing information. Computer system 100 also includes a main memory 106, such as a random access memory (RAM) or other dynamic storage device, coupled to bus 102 for storing information and instructions to be executed by processor 104. Main memory 106 also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 104. Computer system 100 further includes a read only memory (ROM) 108 or other static storage device coupled to bus 102 for storing static information and instructions for processor 104. A storage device 110, such as a magnetic disk or optical disk, is provided and coupled to bus 102 for storing information and instructions.

[00116] Computer system 100 may be coupled via bus 102 to a display 112, such as a cathode ray tube (CRT) or flat panel or touch panel display for displaying information to a computer user. An input device 114, including alphanumeric and other keys, is coupled to bus 102 for communicating information and command selections to processor 104. Another type of user input device is cursor control 116, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor 104 and for controlling cursor movement on display 112. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. A touch panel (screen) display may also be used as an input device. [00117] According to one embodiment, portions of one or more methods described herein may be performed by computer system 100 in response to processor 104 executing one or more sequences of one or more instructions contained in main memory 106. Such instructions may be read into main memory 106 from another computer-readable medium, such as storage device 110. Execution of the sequences of instructions contained in main memory 106 causes processor 104 to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory 106. In an alternative embodiment, hard-wired circuitry may be used in place of or in combination with software instructions. Thus, the description herein is not limited to any specific combination of hardware circuitry and software.

[00118] The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to processor 104 for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device 110. Volatile media include dynamic memory, such as main memory 106. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise bus 102. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read.

[00119] Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor 104 for execution. For example, the instructions may initially be borne on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system 100 can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus 102 can receive the data carried in the infrared signal and place the data on bus 102. Bus 102 carries the data to main memory 106, from which processor 104 retrieves and executes the instructions. The instructions received by main memory 106 may optionally be stored on storage device 110 either before or after execution by processor 104.

[00120] Computer system 100 may also include a communication interface 118 coupled to bus 102. Communication interface 118 provides a two-way data communication coupling to a network link 120 that is connected to a local network 122. For example, communication interface 118 may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, communication interface 118 may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented. In any such implementation, communication interface 118 sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.

[00121] Network link 120 typically provides data communication through one or more networks to other data devices. For example, network link 120 may provide a connection through local network 122 to a host computer 124 or to data equipment operated by an Internet Service Provider (ISP) 126. ISP 126 in turn provides data communication services through the worldwide packet data communication network, now commonly referred to as the “Internet” 128. Local network 122 and Internet 128 both use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network link 120 and through communication interface 118, which carry the digital data to and from computer system 100, are exemplary forms of carrier waves transporting the information.

[00122] Computer system 100 can send messages and receive data, including program code, through the network(s), network link 120, and communication interface 118. In the Internet example, a server 130 might transmit a requested code for an application program through Internet 128, ISP 126, local network 122 and communication interface 118. One such downloaded application may provide all or part of a method described herein, for example. The received code may be executed by processor 104 as it is received, and/or stored in storage device 110, or other non-volatile storage for later execution. In this manner, computer system 100 may obtain application code in the form of a carrier wave.

[00123] Fig. 13 schematically depicts an exemplary lithographic projection apparatus 1000 similar to and/or the same as the apparatus shown in Fig. 1 , Fig. 3 A, and/or Fig. 3B that can be used in conjunction with the techniques described herein. Apparatus 1000 may generally represent a DUV apparatus, for example, with a twin scan setup (this example is not intended to be limiting). The apparatus comprises:

- an illumination system IL, to condition a beam B of radiation. In this particular case, the illumination system also comprises a radiation source SO;

- a first object table (e.g., patterning device table) MT provided with a patterning device holder to hold a patterning device MA (e.g., a reticle), and connected to a first positioner to accurately position the patterning device with respect to item PS;

- a second object table (substrate table) WT provided with a substrate holder to hold a substrate W (e.g., a resist-coated silicon wafer), and connected to a second positioner to accurately position the substrate with respect to item PS;

- a projection system (“lens”) PS (e.g., a refractive, catoptric or catadioptric optical system) to image an irradiated portion of the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[00124] As depicted herein, the apparatus is of a transmissive type (i.e., has a transmissive patterning device). However, in general, it may also be of a reflective type, for example (with a reflective patterning device). The apparatus may employ a different kind of patterning device to classic mask; examples include a programmable mirror array or LCD matrix.

[00125] The source SO (e.g., a mercury lamp or excimer laser, LPP (laser produced plasma) EUV source) produces a beam of radiation. This beam is fed into an illumination system (illuminator) IL, either directly or after having traversed conditioning means, such as a beam expander Ex, for example. The illuminator IL may comprise adjusting means for setting the outer and/or inner radial extent (commonly referred to as s-outer and s-inner, respectively) of the intensity distribution in the beam. In addition, it will generally comprise various other components, such as an integrator and a condenser. In this way, the beam B impinging on the patterning device MA has a desired uniformity and intensity distribution in its cross-section.

[00126] It should be noted with regard to Fig. 13 that the source SO may be within the housing of the lithographic projection apparatus (as is often the case when the source SO is a mercury lamp, for example), but that it may also be remote from the lithographic projection apparatus, the radiation beam that it produces being led into the apparatus (e.g., with the aid of suitable directing mirrors); this latter scenario is often the case when the source SO is an excimer laser (e.g., based on KrF, ArF or F2 lasing). [00127] The beam subsequently intercepts the patterning device MA, which is held on a patterning device table MT. Having traversed the patterning device MA, the beam B passes through the lens PL, which focuses the beam B onto a target portion C of the substrate W. With the aid of the second positioning means (and interferometric measuring means), the substrate table WT can be moved accurately, e.g. to position different target portions C in the path of the beam. Similarly, the first positioning means can be used to accurately position the patterning device MA with respect to the path of the beam B, e.g., after mechanical retrieval of the patterning device MA from a patterning device library, or during a scan. In general, movement of the object tables MT, WT will be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which are not explicitly depicted. However, in the case of a stepper (as opposed to a step-and-scan tool) the patterning device table MT may just be connected to a short stroke actuator, or may be fixed.

[00128] The depicted tool can be used in two different modes:

- In step mode, the patterning device table MT is kept essentially stationary, and an entire patterning device image is projected in one operation (i.e., a single “flash”) onto a target portion C. The substrate table WT is then shifted in the x and/or y directions so that a different target portion C can be irradiated by the beam;

- In scan mode, essentially the same scenario applies, except that a given target portion C is not exposed in a single “flash”. Instead, the patterning device table MT is movable in a given direction (the so-called “scan direction”, e.g., the y direction) with a speed v, so that the projection beam B is caused to scan over a patterning device image; concurrently, the substrate table WT is simultaneously moved in the same or opposite direction at a speed V = Mv, in which M is the magnification of the lens PL (typically, M = 1/4 or 1/5). In this manner, a relatively large target portion C can be exposed, without having to compromise on resolution.

[00129] While the concepts disclosed herein may be used for wafer manufacturing on a substrate such as a silicon wafer, it shall be understood that the disclosed concepts may be used with any type of manufacturing system, e.g., those used for manufacturing on substrates other than silicon wafers. In addition, the combination and sub-combinations of disclosed elements may comprise separate embodiments. For example, the expanding and contracting cleaning tool (Fig. 3A-10), and the internally illuminated cleaning too (e.g., Fig. 11-13) may comprise separate embodiments, and/or these features may be used together in the same embodiment.

[00130] The embodiments may further be described using the following clauses:

1. A cleaning tool for cleaning a portion of a lithography apparatus, the cleaning tool comprising: a body configured to be inserted into the lithography apparatus; and a cleaning film, a first side of the cleaning film being configured to attach to a surface of the cleaning tool and a second side of the cleaning film being at least partially covered by a cleaning material, the second side being opposite to the first side, wherein the cleaning film is configured to prevent the cleaning material from contacting the surface of the cleaning tool, and the cleaning material is configured to clean, upon contact, the portion of the lithography apparatus.

2. The cleaning tool of clause 1, wherein the cleaning film is removably attached to the surface of the cleaning tool.

3. The cleaning tool of any of clauses 1-2, wherein the cleaning film comprises: a first layer at least partially covered with the cleaning material, and a second layer configured to attach to the surface of the cleaning material and prevent the cleaning material from contacting the surface of the cleaning tool.

4. The cleaning tool of clause 3, wherein the second layer is transparent to allow one or more features on the cleaning tool to be readable via a tool handler.

5. The cleaning tool of any of clauses 1-4, wherein the cleaning film include one or more cutout portions associated with one or more features of at least one of: a tool handler used to engage with the cleaning tool; one or more clamp elements at the portion of the lithography apparatus; or one or more identification features on the surface of the cleaning tool.

6. The cleaning tool of clause 5, wherein the one or more cutout portions are within the first layer and not on the second layer.

7. The cleaning tool of any of clauses 5-6, wherein the one or more identification features comprise one or both of a bar code and an alignment mark that are readable via an optical sensor through the second layer.

8. The cleaning tool of any of clauses 5-7, wherein the one or more clamp elements comprise one or more vacuum holes provided on the portion of the lithography apparatus to clamp a reticle via vacuum clamps.

9. The cleaning tool of clause 5-8, wherein the cleaning tool comprises: a first cleaning film attached over the one or more identification features at a first edge of the surface of the cleaning tool, the one or more identification features being readable through the second layer of the first cleaning film; and a second cleaning film attached at a second edge of the surface of the cleaning tool, the second edge being distant and parallel to the first edge.

10. The cleaning tool of any of clauses 1-9, wherein the cleaning film further comprises an adhesive layer disposed between the first layer and the second layer, wherein the adhesive layer keeps the second layer adhered to the third layer even when the cleaning film is removed from the cleaning tool.

11. The cleaning tool of any clauses 1-10, wherein the cleaning tool is configured to contact the cleaning film with a target surface of the portion of the lithography apparatus, and move relative to the portion of the lithography apparatus when cleaning the portion of the lithography apparatus by the cleaning film.

12. The cleaning tool of clause 11, wherein the cleaning film is configured to be parallel to the target surface.

13. The cleaning tool of any of clauses 11-12, wherein the one or more cleaning films contact the target portion for a specified dwell time.

14. The cleaning tool of any of clauses 11-13, wherein the one or more cleaning films moves relative to the target portion for a specified scrub time or cycles.

15. The cleaning tool of any of clauses 11-14, wherein the target surface comprise one or more membrane surfaces of the lithography apparatus.

16. The cleaning tool of any of clauses 1-15, wherein the cleaning tool is configured to be engaged by a tool handler of the lithography apparatus, the tool handler being configured to engage with the cleaning tool, and move and orient the cleaning tool such that the cleaning film to face the portion of the lithography apparatus to be cleaning.

17. The cleaning tool of any of clauses 1-16, further comprising: a container configured to hold the cleaning tool and fit into the lithography apparatus, wherein the cleaning tool is configured to be inserted into the lithography apparatus in the container, moved from the container by the tool handler for the cleaning, and returned to the container by the tool handler after the cleaning.

18. The cleaning tool of clause 17, wherein the container comprises a plurality of slots, each slot configured to hold a cleaning tool of the one or more cleaning tool.

19. The cleaning tool of any of clauses 17-18, wherein the container comprises a non-reactive material that does not react with the cleaning material of the one or more cleaning films attached to the cleaning tool.

20. The cleaning tool of clause 19, wherein the non-reactive material is a high density polyethylene.

21. The cleaning tool of any of clauses 1-20, wherein the portion of the lithography apparatus comprises a portion of a reticle clamp of a reticle stage.

22. The cleaning tool of clause 21, wherein the portion of the reticle clamp contacts with and supports a reticle during a patterning process.

23. The cleaning tool of clause 21-22, wherein the portion of the reticle clamp is at least one vacuum pad attached to the reticle clamp.

24. The cleaning tool of any of clauses 1-23, wherein the cleaning tool comprises a cleaning reticle.

25. The cleaning tool of any of clauses 5-25, wherein the tool handler comprises a reticle handler turret gripper.

26. The cleaning tool of any of clauses 1-25, wherein the lithography apparatus is configured for deep ultra violet (DUV) radiation.

27. The cleaning tool of any of clauses 1-26, wherein the cleaning material of the one or more cleaning films is at least one of: Chrome etchant, isopropyl alcohol solution, deionized water, or methanol.

28. A cleaning tool for cleaning a portion of a lithography apparatus, the cleaning tool comprising: a body configured to be inserted into the lithography apparatus; and a cleaning film, a first side of the cleaning film being configured to attach to a surface of the cleaning tool and a second side of the cleaning film being at least partially covered by a cleaning material, the second side being opposite to the first side, wherein the cleaning film comprises a transparent portion through which one or more features on the surface of the cleaning tool are readable, and the cleaning material is configured to clean, upon contact, the portion of the lithography apparatus.

29. The cleaning tool of clause 28, wherein the cleaning film is removably attached to the surface of the cleaning tool.

30. The cleaning tool of any of clauses 28-29, wherein the cleaning film comprises: a first layer at least partially covered with the cleaning material, and a second layer configured to attach to the surface of the cleaning material and prevent the cleaning material from contacting the surface of the cleaning tool, and is transparent to allow one or more features on the cleaning to be readable via a tool handler.

31. The cleaning tool of any of clauses 28-30, wherein the cleaning film include one or more cutout portions associated with one or more features of at least one of: a tool handler used to engage with the cleaning tool; one or more clamp elements at the portion of the lithography apparatus; or one or more identification features on the surface of the cleaning tool.

32. The cleaning tool of clause 31, wherein the one or more cutout portions are within the first layer and not on the second layer.

33. The cleaning tool of any of clauses 31-32, wherein the one or more identification features comprise one or both of a bar code and an alignment mark that are readable through the second layer.

34. The cleaning tool of any of clauses 31-33, wherein the one or more clamp elements comprise one or more vacuum holes provided on the portion of the lithography apparatus to clamp a reticle via vacuum clamps.

35. The cleaning tool of clause 31-34, wherein the cleaning tool comprises: a first cleaning film attached over the one or more identification features at a first edge of the surface of the cleaning tool, the one or more identification features being readable through the second layer of the first cleaning film; and a second cleaning film attached at a second edge of the surface of the cleaning tool, the second edge being distant and parallel to the first edge.

36. The cleaning tool of any of clauses 28-35, wherein the cleaning film further comprises an adhesive layer disposed between the first layer and the second layer, wherein the adhesive layer keeps the second layer adhered to the third layer even when the cleaning film is removed from the cleaning tool.

37. A method for cleaning a portion of a lithography apparatus with a cleaning tool comprising one or more cleaning films, the method comprising: inserting, via a tool handler, the cleaning tool into the lithography apparatus; contacting, via the tool handler, the one or more cleaning films of the cleaning tool with the portion of the lithography apparatus to be cleaned; and cleaning, via the tool handler, the portion of the lithography apparatus with the one or more cleaning films of the cleaning tool, the cleaning comprises moving the cleaning tool relative to the portion of the lithography apparatus for a specified scrub time or cycles.

38. The method of clause 37, wherein the cleaning the portion of the lithography apparatus comprises repeatedly moving the second cleaning tool parallel to and in a back-and-forth direction with respect to the portion of the lithography apparatus.

39. The method of clause 38, wherein the back-and-forth movement is restricted to a range +2mm.

40. The method of any of clauses 37-39, wherein the cleaning further comprises: maintaining the one or more cleaning films in contact with the portion of the lithography apparatus for a specified dwell time.

41. The method of clause 40, wherein during the specified dwell time, the cleaning tool is stationary.

42. The method of clause 41, wherein during the specified dwell time the cleaning tool is disengaged from the tool handler and is vacuum-clamped.

43. The method of any of clauses 37-42, further comprising: selecting, based on a contaminant being cleaned, the cleaning tool from a container, moving the cleaning tool from the container with the tool handler for cleaning the portion of the lithography apparatus, removing the one or more cleaning films from the cleaning tool after cleaning, and returning the cleaning tool to the container with the tool handler after the cleaning.

44. The method of clause 43, wherein the contaminant on the portion of the lithography apparatus comprises: a first contaminant or a second contaminant deposited on the portion of the lithography apparatus.

45. The method of clause 44, wherein the first contaminant is chrome (Cr) particles deposited on the portion of the lithography apparatus.

46. The method of clause 44, wherein the second contaminant is hard particles, a residual chromium etchant, or organic material deposited on the portion of the lithography apparatus.

47. The method of clause 44-46 wherein when cleaning the first contaminant, the cleaning process comprises: applying an etchant to the one or more cleaning films attached to a first cleaning tool; leaving the one or more cleaning films in contact with the portion of the lithography apparatus for a specified dwell time, the etchant reacting with the first contaminant during the specified dwell time; removing the first cleaning tool and placing the first cleaning tool in the container; applying a cleaning solution to the one or more cleaning films attached to a second cleaning tool; and moving the second cleaning tool relative to the portion of the lithography apparatus for a specified scrub time, while the one or more cleaning films are in contact with the portion of the lithography apparatus.

48. The method of clause 47, wherein the moving of the second cleaning tool comprises moving the second cleaning tool parallel to and in a back-and-forth direction with respect to the portion of the lithography apparatus.

49. The method of clause 48, wherein the moving of the second cleaning tool comprises: reducing a clamping force exerted on the cleaning tool by adjusting a vacuum level to allow moving of the second tool while maintaining contact between the cleaning material of the film and the portion of the lithography apparatus.

50. The method of any of clauses 37-49, wherein the portion of the lithography apparatus comprises a reticle clamp of a reticle stage.

51. The method of any of clauses 37-50, wherein the cleaning tool comprises a cleaning reticle.

52. The method of any of clauses 37-51, wherein the tool handler comprises a reticle handler turret gripper.

53. The method of any of clauses 37-52, wherein the lithography apparatus is configured for deep ultra violet (DUV) radiation.

54. A non-transitory computer-readable media comprising instructions for cleaning a portion of a lithography apparatus with a cleaning tool comprising one or more cleaning films, the instructions when executed by one or more processors, cause operations comprising: inserting, via a tool handler, the cleaning tool into the lithography apparatus; contacting, via the tool handler, the one or more cleaning films of the cleaning tool with the portion of the lithography apparatus to be cleaned; and cleaning, via the tool handler, the portion of the lithography apparatus with the one or more cleaning films of the cleaning tool, the cleaning comprises moving the cleaning tool relative to the portion of the lithography apparatus for a specified scrub time or cycles.

55. The non-transitory computer-readable media of clause 54, wherein the cleaning the portion of the lithography apparatus comprises repeatedly moving the second cleaning tool parallel to and in a back- and-forth direction with respect to the portion of the lithography apparatus.

56. The non-transitory computer-readable media of clause 55, wherein the back-and-forth movement is restricted to a range +2mm. 57. The non-transitory computer-readable media of any of clauses 54-56, wherein the cleaning further comprises: maintaining the one or more cleaning films in contact with the portion of the lithography apparatus for a specified dwell time.

58. The non-transitory computer-readable media of clause 57, wherein during the specified dwell time, the cleaning tool is stationary.

59. The non-transitory computer-readable media of clause 58, wherein during the specified dwell time the cleaning tool is disengaged from the tool handler and is vacuum-clamped.

60. The non-transitory computer-readable media of any of clauses 54-59, further comprising: selecting, based on a contaminant being cleaned, the cleaning tool from a container, moving the cleaning tool from the container with the tool handler for cleaning the portion of the lithography apparatus, removing the one or more cleaning films from the cleaning tool after cleaning, and returning the cleaning tool to the container with the tool handler after the cleaning.

61. The non-transitory computer-readable media of clause 60, wherein the contaminant on the portion of the lithography apparatus comprises: a first contaminant or a second contaminant deposited on the portion of the lithography apparatus.

62. The non-transitory computer-readable media of clause 61, wherein the first contaminant is chrome (Cr) particles deposited on the portion of the lithography apparatus.

63. The non-transitory computer-readable media of clause 61, wherein the second contaminant is hard particles, a residual chromium etchant, or organic material deposited on the portion of the lithography apparatus.

64. The non-transitory computer-readable media of clause 61-63 wherein when cleaning the first contaminant, the cleaning process comprises: applying an etchant to the one or more cleaning films attached to a first cleaning tool; leaving the one or more cleaning films in contact with the portion of the lithography apparatus for a specified dwell time, the etchant reacting with the first contaminant during the specified dwell time; removing the first cleaning tool and placing the first cleaning tool in the container; applying a cleaning solution to the one or more cleaning films attached to a second cleaning tool; and moving the second cleaning tool relative to the portion of the lithography apparatus for a specified scrub time, while the one or more cleaning films are in contact with the portion of the lithography apparatus. 65. The non-transitory computer-readable media of clause 64, wherein the moving of the second cleaning tool comprises moving the second cleaning tool parallel to and in a back-and-forth direction with respect to the portion of the lithography apparatus.

66. The non-transitory computer-readable media of clause 65, wherein the moving of the second cleaning tool comprises: reducing a clamping force exerted on the cleaning tool by adjusting a vacuum level to allow moving of the second tool while maintaining contact between the cleaning material of the film and the portion of the lithography apparatus.

67. The non-transitory computer-readable media of any of clauses 54-66, wherein the portion of the lithography apparatus comprises a reticle clamp of a reticle stage.

68. The non-transitory computer-readable media of any of clauses 54-67, wherein the cleaning tool comprises a cleaning reticle.

69. The non-transitory computer-readable media of any of clauses 54-68, wherein the tool handler comprises a reticle handler turret gripper. 70. The non-transitory computer-readable media of any of clauses 54-69, wherein the lithography apparatus is configured for deep ultra violet (DUV) radiation.

[00131] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims set out below.