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Title:
A CLEANING DEVICE, A LITHOGRAPHY APPARATUS, A METHOD OF REMOVING WATER OR OTHER CONTAMINANT AND A DEVICE MANUFACTURING METHOD
Document Type and Number:
WIPO Patent Application WO/2021/063722
Kind Code:
A1
Abstract:
A cleaning device (10) for a lithography apparatus, the cleaning device comprising: a radiation source (2) configured to supply decontamination radiation (8) capable of removing water or other contaminant from the surface of an optical component (IL; PS) or other component of the lithography system; wherein the cleaning device is configured to be clamped by a clamp (7) that clamps a patterning device during exposure processes performed by the lithography apparatus.

Inventors:
SAFINOWSKI, Pawel (5500 AH Veldhoven, NL)
VAN DE KERKHOF, Marcus, Adrianus (5500 AH Veldhoven, NL)
ZDRAVKOV, Alexandar, Nikolov (5500 AH Veldhoven, NL)
Application Number:
EP2020/076283
Publication Date:
April 08, 2021
Filing Date:
September 21, 2020
Export Citation:
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Assignee:
ASML NETHERLANDS B.V. (5500 AH Veldhoven, NL)
International Classes:
G03F7/20; B08B7/00; H05G2/00
Attorney, Agent or Firm:
FILIP, Diana (P.O. Box 324, 5500 AH Veldhoven, NL)
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Claims:
CLAIMS

1. A cleaning device for a lithography apparatus, the cleaning device comprising: a radiation source configured to supply decontamination radiation capable of removing water or other contaminant from a surface of an optical component or other component of the lithography apparatus; wherein the cleaning device is configured to be clamped by a clamp that clamps a patterning device during exposure processes performed by the lithography apparatus.

2. The cleaning device of claim 1, wherein the lithography apparatus is an EUV lithography apparatus, wherein the clamp is an electrostatic clamp and wherein the cleaning device has the standard dimensions of a patterning device for EUV lithography.

3. The cleaning device of claim 1, wherein the cleaning device has a square shape.

4. The cleaning device of claim 3, wherein the square shape has a side length of 152mm.

5. The cleaning device of claim 3 or 4, wherein the cleaning device has a thickness of 6.35mm.

6. The cleaning device of any preceding claim, comprising: an energy source configured to supply energy to the radiation source to supply the decontamination radiation.

7. The cleaning device of claim 6, wherein the energy source is a battery.

8. The cleaning device of any of claims 1 to 5, comprising: an induction coil configured to receive power from an electromagnetic field, wherein the induction coil is electrically connected to the radiation source so as to supply energy to the radiation source to supply the decontamination radiation.

9. The cleaning device of any preceding claim, comprising: a controller configured to control the supply of decontamination radiation by the radiation source.

10. The cleaning device of any preceding claim, comprising: a gas release module configured to supply a gas out from the cleaning device.

11. The cleaning device of any preceding claim, comprising: an optical element configured to focus and direct the decontamination radiation supplied by the radiation source.

12. A lithography apparatus comprising: a radiation system configured to provide a projection beam of radiation; a support structure configured to support a patterning device serving to pattern the projection beam according to a desired pattern; a substrate table configured to hold a substrate; a projection system configured to project the patterned beam onto a target portion of the substrate; and the cleaning device of any preceding claim, wherein the support structure is configured to support the cleaning device.

13. The lithography apparatus of claim 12, comprising: the patterning device, wherein the patterning device and the cleaning device have substantially the same shape as each other.

14. The lithography apparatus of claim 13, comprising: a library for storing the patterning device and the cleaning device.

15. The lithography apparatus of claim 14, wherein the library comprises a charging station configured to charge a battery of the cleaning device.

16. The lithography apparatus of claim 14 or 15, wherein the library stores a plurality of cleaning devices of any of claims.

17. The lithography apparatus of claim 16, wherein the cleaning devices are configured to supply decontamination radiation of different characteristics from each other.

18. A method of removing water or other contaminant from a surface of an optical component or other component of a lithography apparatus, the method comprising the steps of: clamping a cleaning device onto a support structure that is configured to support a patterning device that serves to pattern a projection beam according to a desired pattern; and supplying decontamination radiation from the cleaning device so as to remove water or other contaminant from the surface of the optical component or other component of the lithography apparatus.

19. A device manufacturing method comprising the steps of: removing water or other contaminant from a surface of an optical component or other component of a lithography apparatus by irradiation from a cleaning device with radiation capable of removing said water or other contaminant; replacing the cleaning device with a patterning device; providing a substrate that is at least partially covered by a layer of radiation-sensitive material; providing a projection beam of radiation using a radiation system; using the patterning device to endow the projection beam with a pattern in its cross-section; and projecting the patterned beam of radiation onto a target portion of the layer of radiation- sensitive material.

Description:
A CLEANING DEVICE. A LITHOGRAPHY APPARATUS. A METHOD OF REMOVING WATER OR OTHER CONTAMINANT AND A DEVICE MANUFACTURING METHOD

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 19200715.1 which was filed on

October 1, 2019 and which is incorporated herein in its entirety by reference.

FIELD

[0002] The present invention relates to a cleaning device, a lithography apparatus, a method of removing water or other contaminant and a device manufacturing method.

BACKGROUND

[0003] A lithography apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithography apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that instance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (e.g., comprising part of, one, or several dies) on a substrate (e.g., a silicon wafer). Transfer of the pattern is typically via imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned. [0004] Lithography is widely recognized as one of the key steps in the manufacture of ICs and other devices and/or structures. However, as the dimensions of features made using lithography become smaller, lithography is becoming a more critical factor for enabling miniature IC or other devices and or structures to be manufactured.

[0005] A theoretical estimate of the limits of pattern printing can be given by the Rayleigh criterion for resolution as shown in equation (1): where l is the wavelength of the radiation used, NA is the numerical aperture of the projection system used to print the pattern, kl is a process dependent adjustment factor, also called the Rayleigh constant, and CD is the feature size (or critical dimension) of the printed feature. It follows from equation (1) that reduction of the minimum printable size of features can be obtained in three ways: by shortening the exposure wavelength l, by increasing the numerical aperture NA or by decreasing the value of kl.

[0006] In order to shorten the exposure wavelength and, thus, reduce the minimum printable size, it has been proposed to use an extreme ultraviolet (EUV) radiation source. EUV radiation is electromagnetic radiation having a wavelength within the range of 10-20 nm, for example within the range of 13-14 nm. It has further been proposed that EUV radiation with a wavelength of less than 10 nm could be used, for example within the range of 5-10 nm such as 6.7 nm or 6.8 nm. Such radiation is termed extreme ultraviolet radiation or soft x-ray radiation. Possible sources include, for example, laser-produced plasma sources, discharge plasma sources, or sources based on synchrotron radiation provided by an electron storage ring.

[0007] EUV radiation may be produced using a plasma. A radiation system for producing

EUV radiation may include a laser for exciting a fuel to provide the plasma, and a source collector module for containing the plasma. The plasma may be created, for example, by directing a laser beam at a fuel, such as particles of a suitable material (e.g., tin), or a stream of a suitable gas or vapor, such as Xe gas or Li vapor. The resulting plasma emits output radiation, e.g., EUV radiation, which is collected using a radiation collector. The radiation collector may be a mirrored normal incidence radiation collector, which receives the radiation and focuses the radiation into a beam. The source collector module may include an enclosing structure or chamber arranged to provide a vacuum environment to support the plasma. Such a radiation system is typically termed a laser produced plasma (LPP) source.

[0008] The lithography apparatus comprises optical elements, for example for producing the radiation beam and projecting the radiation beam to the substrate. After service interventions water and hydrocarbon contamination can deposit on the optical elements. Additionally, the transmission and reflection properties of the optical elements can degrade over time due to water and possibly contaminant particles on the optical elements. The optical elements can be cleaned using the scanner. [0009] It is desirable to provide a cleaning device that can clean the optical elements more effectively and/or in a less costly manner.

SUMMARY OF THE INVENTION

[0010] According to an aspect of the invention, there is provided a cleaning device for a lithography apparatus, the cleaning device comprising: a radiation source configured to supply decontamination radiation capable of removing water or other contaminant from a surface of an optical component or other component of the lithography apparatus; wherein the cleaning device is configured to be clamped by a clamp that clamps a patterning device during exposure processes performed by the lithography apparatus.

[0011] According to an aspect of the invention, there is provided a lithography apparatus comprising: a radiation system configured to provide a projection beam of radiation; a support structure configured to support a patterning device serving to pattern the projection beam according to a desired pattern a substrate table configured to hold a substrate; a projection system configured to project the patterned beam onto a target portion of the substrate; and the cleaning device mentioned above, wherein the support structure is configured to support the cleaning device. [0012] According to an aspect of the invention, there is provided a method of removing water or other contaminant from a surface of an optical component or other component of a lithography apparatus, the method comprising the steps of: clamping a cleaning device onto a support structure that is configured to support a patterning device that serves to pattern a projection beam according to a desired pattern; and supplying decontamination radiation from the cleaning device so as to remove water or other contaminant from a surface of an optical component or other component of the lithography apparatus.

[0013] According to an aspect of the invention, there is provided a device manufacturing method comprising the steps of: removing water or other contaminant from a surface of an optical component or other component of a lithography apparatus by irradiation from a cleaning device with radiation capable of removing said water or other contaminant; replacing the cleaning device with a patterning device; providing a substrate that is at least partially covered by a layer of radiation- sensitive material; providing a projection beam of radiation using a radiation system; using the patterning device to endow the projection beam with a pattern in its cross-section; and projecting the patterned beam of radiation onto a target portion of the layer of radiation-sensitive material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] 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:

[0015] Figure 1 depicts a lithography apparatus according to an embodiment of the invention;

[0016] Figure 2 is a more detailed view of the lithography apparatus;

[0017] Figure 3 is a more detailed view of the source collector module SO of the apparatus of Figures 1 and 2; and

[0018] Figure 4 is a schematic diagram of a cleaning device in an EUV lithography apparatus according to an embodiment of the invention.

[0019] The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.

DETAIFED DESCRIPTION

[0020] Figure 1 schematically depicts a lithography apparatus 100 including a source collector module SO according to one embodiment of the invention. The apparatus comprises: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., EUV radiation). a support structure (e.g., a mask table) MT constructed to support a patterning device (e.g., a mask or a reticle) MA and connected to a first positioner PM configured to accurately position the patterning device; a substrate table (e.g., a wafer table) WT constructed to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate; and a projection system (e.g., a reflective projection 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) of the substrate W.

[0021] 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.

[0022] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device, the design of the lithography apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure can 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.

[0023] The term “patterning device” should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. The pattern imparted to the radiation beam may correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

[0024] The 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 so as 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.

[0025] The projection system, like 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, as appropriate for the exposure radiation being used, or for other factors such as the use of a vacuum. It may be desired to use a vacuum for EUV radiation since other gases may absorb too much radiation. A vacuum environment may therefore be provided to the whole beam path with the aid of a vacuum wall and vacuum pumps. [0026] As here depicted, the apparatus is of a reflective type (e.g., employing a reflective mask).

[0027] The lithography apparatus may be of a type having two (dual stage) or more substrate tables (and/or two or more mask tables). 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.

[0028] Referring to Figure 1, the illuminator IL receives an extreme ultra violet radiation beam from the source collector module SO. Methods to produce EUV light include, but are not necessarily limited to, converting a material into a plasma state that has at least one element, e.g., xenon, lithium or tin, with one or more emission lines in the EUV range. In one such method, often termed laser produced plasma (“LPP”) the required plasma can be produced by irradiating a fuel, such as a droplet, stream or cluster of material having the required line-emitting element, with a laser beam. The source collector module SO may be part of an EUV radiation system including a laser, not shown in Figure 1, for providing the laser beam exciting the fuel. The resulting plasma emits output radiation, e.g., EUV radiation, which is collected using a radiation collector, disposed in the source collector module. The laser and the source collector module may be separate entities, for example when a CO2 laser is used to provide the laser beam for fuel excitation.

[0029] In such cases, the laser is not considered to form part of the lithography apparatus and the radiation beam is passed from the laser to the source collector module with the aid of a beam delivery system comprising, for example, suitable directing mirrors and or a beam expander. In other cases the source may be an integral part of the source collector module, for example when the source is a discharge produced plasma EUV generator, often termed as a DPP source.

[0030] The illuminator IL may comprise an adjuster for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as □ -outer and □ -inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL may comprise various other components, such as facetted field and pupil mirror devices. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross-section.

[0031] 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. After being reflected from the patterning device (e.g., mask) 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 PS2 (e.g., an interferometric device, linear encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g., so as to position different target portions C in the path of the radiation beam B. Similarly, the first positioner PM and another position sensor PS1 can be used to accurately position the patterning device (e.g., mask) MA with respect to the path of the radiation beam B. Patterning device (e.g., mask) MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks PI, P2.

[0032] The depicted apparatus could be used in at least one of the following modes:

[0033] 1. In step mode, the support structure (e.g., mask table) MT and the substrate table WT are kept essentially stationary, while an entire 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.

[0034] 2. In scan mode, the support structure (e.g., mask table) 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 (e.g., mask table) MT may be determined by the (de- )magnification and image reversal characteristics of the projection system PS.

[0035] 3. In another mode, the support structure (e.g., mask table) 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.

[0036] Combinations and or variations on the above described modes of use or entirely different modes of use may also be employed.

[0037] Figure 2 shows the apparatus 100 in more detail, including the source collector module SO, the illumination system IL, and the projection system PS. The source collector module SO is constructed and arranged such that a vacuum environment can be maintained in an enclosing structure 220 of the source collector module SO. An EUV radiation emitting plasma 210 may be formed by a discharge produced plasma source. EUV radiation may be produced by a gas or vapor, for example Xe gas, Li vapor or Sn vapor in which the very hot plasma 210 is created to emit radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 is created by, for example, an electrical discharge causing an at least partially ionized plasma. Partial pressures of, for example, 10 Pa of Xe, Li, Sn vapor or any other suitable gas or vapor may be required for efficient generation of the radiation. In an embodiment, a plasma of excited tin (Sn) is provided to produce EUV radiation.

[0038] The radiation emitted by the hot plasma 210 is passed from a source chamber 211 into a collector chamber 212 via an optional gas barrier or contaminant trap 230 (in some cases also referred to as contaminant barrier or foil trap) that is positioned in or behind an opening in source chamber 211. The contaminant trap 230 may include a channel structure. Contamination trap 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 further indicated herein at least includes a channel structure, as known in the art.

[0039] The collector chamber 211 may include a radiation collector CO, which may be a so- called grazing incidence collector. Radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation that traverses collector CO can be reflected off a grating spectral filter 240 to be focused in a virtual source point IF. The virtual source point IF is commonly referred to as the intermediate focus, and the source collector module is arranged such that the intermediate focus IF is located at or near an opening 221 in the enclosing structure 220. The virtual source point IF is an image of the radiation emitting plasma 210.

[0040] Subsequently the radiation traverses the illumination system IL, which may include a facetted field mirror device 22 and a facetted pupil mirror device 24 arranged to provide a desired angular distribution of the radiation beam 21, at the patterning device MA, as well as a desired uniformity of radiation intensity at the patterning device MA. Upon reflection of the beam of radiation 21 at the patterning device MA, held by the support structure MT, a patterned beam 26 is formed and the patterned beam 26 is imaged by the projection system PS via reflective elements 28, 30 onto a substrate W held by the wafer stage or substrate table WT.

[0041] More elements than shown may generally be present in illumination optics unit IL and projection system PS. The grating spectral filter 240 may optionally be present, depending upon the type of lithography apparatus. Further, there may be more mirrors present than those shown in the Figures, for example there may be 1- 6 additional reflective elements present in the projection system PS than shown in Figure 2.

[0042] Collector optic CO, as illustrated in Figure 2, is depicted as a nested collector with grazing incidence reflectors 253, 254 and 255, just as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254 and 255 are disposed axially symmetric around an optical axis O and a collector optic CO of this type is preferably used in combination with a discharge produced plasma source, often called a DPP source.

[0043] Alternatively, the source collector module SO may be part of an LPP radiation system as shown in Figure 3. A laser LA is arranged to deposit laser energy into a fuel, such as xenon (Xe), tin (Sn) or lithium (Li), creating the highly ionized plasma 210 with electron temperatures of several 10’s of eV. The energetic radiation generated during de -excitation and recombination of these ions is emitted from the plasma, collected by a near normal incidence collector optic CO and focused onto the opening 221 in the enclosing structure 220.

[0044] The lithography apparatus 100 comprises optical elements such as lenses and mirrors.

For example, the projection system PS may comprise a combination of lenses and mirrors. In an embodiment the surfaces of the optical elements are provided with coatings. Over time, the transmission and/or reflection properties of the optical elements can degrade. In particular, transmission loss and/or reflection loss can increase. The degradation is at least partly caused by oxidation of the surfaces of the coatings.

[0045] The inventors have found that the oxidation is at least partly caused by water present on the optical surfaces. Water molecules can be deposited during use of the lithography apparatus 100. Such water molecules can stay on the surfaces in the vacuum environment, e.g. on surfaces of optical components such as mirrors or membranes or on the surface of other components of the lithography apparatus such as an internal surface of a vessel or housing of the lithography apparatus. EUV radiation incident on a surface with water causes the water molecules to turn into hydrogen and oxygen radicals. The oxygen radicals cause the optical coatings to oxidise.

[0046] Oxidation of mirrors is an irreversible and highly damaging process and leads to a very significant loss in mirror reflection. Due to the restrictively high cost of replacing the mirrors, this ultimately leads to the operation of the lithography apparatus with poor reflection levels and therefore a reduction in productivity. The reduction in lifetime of the mirrors also results in a further distinct economic disadvantage.

[0047] In an embodiment the lithography apparatus 100 comprises one or more transmissive membranes. For example, a membrane known as a pellicle may be used to prevent particles from reaching the patterning device MA.

[0048] In an embodiment the lithography apparatus 100 comprises a dynamic gas lock. The dynamic gas lock is configured to prevent a flow of gas between different sections of the lithography apparatus 100. The dynamic gas lock may comprise a hollow part covered by a pellicle (i.e. a transmissive membrane) located in the intervening space.

[0049] Water molecules can be present on the surface of the membrane (e.g. in a patterning device pellicle or in a dynamic gas lock). The water molecules can cause a reduction in transmissivity of the membrane for EUV radiation. The water molecules can lead to sagging of the membrane. The water molecules can increase the possibility of the membrane rupturing.

[0050] Figure 4 is a schematic diagram of a cleaning device 10 for an EUV lithography apparatus 100. The cleaning device 10 is configured to clean surfaces in the lithography apparatus 100. For example, in an embodiment the cleaning device 10 is configured to clean surfaces of optical elements (or their coatings). In an embodiment the cleaning device 10 is configured to clean a surface of one or more membranes used in the lithography apparatus 100.

[0051] As shown in Figure 4, in an embodiment the cleaning device 10 comprises a radiation source 2. The radiation source 2 is configured to supply decontamination radiation 8. The type of radiation source 2 is not particularly limited. In an embodiment the radiation source 2 is a VCSEF.

In an alternative embodiment, the radiation source 2 is an edge-emitting infra-red diode.

[0052] The decontamination radiation 8 is capable of removing water or other contaminant adhered to a surface of an optical component or other component of the lithography apparatus. The water contaminates the optical component. In an embodiment the decontamination radiation 8 is capable of removing other contaminants such as hydroxyl groups. Water molecules and hydroxyl groups can help other contaminants including contaminant particles stick to the optical component (e.g. by capillary force). Such contaminant particles may be introduced into the system from external sources or they may be generated from within the lithography apparatus 100. For example, the contaminant particles may include debris and by-products that are sputtered loose from the substrate W, for example by an EUV radiation beam B. By removing water and/or hydroxyl groups from the optical component, it is easier to remove contaminant particles, for example by a flushing process. By using the cleaning device 100, the water collected on the optical elements can be removed before exposing the optics to the EUV radiation. An embodiment of the invention is expected to reduce the probability the oxidation mechanism (such that fewer water molecules can be cracked). An embodiment of the invention is expected to shorten the EUV scanner stabilization time during and after scanner recovery.

[0053] In an embodiment the decontamination radiation 8 has a wavelength range around about 3pm. However, other wavelengths (e.g. other infra-red wavelengths can be used). Suitable wavelengths or ranges of wavelengths for the decontamination radiation 8 fall within the range 2pm to 300mm. In an embodiment the decontamination radiation 8 has a wavelength in the range of from about 100pm to about 300mm (microwave radiation). In an embodiment the decontamination radiation 8 has a wavelength in the range of from about 2pm to about 30pm (infra-red radiation). The wavelength of the decontamination radiation 8 is not particularly limited.

[0054] In an embodiment the cleaning device 10 is configured to be clamped by an electrostatic clamp that clamps a patterning device MA during exposure processes performed by the EUV lithography apparatus 100.

[0055] In an embodiment, a chuck 7 is provided for holding the patterning device MA via electrostatic force onto the support structure MT of the lithography apparatus 100. Such a chuck may be referred to as an electrostatic clamp. A similar electrostatic clamp can be used to hold the substrate W. In an embodiment the chuck comprises a dielectric member.

[0056] During exposure processes the electrostatic clamp clamps the patterning device MA to the support structure MT. When it is desired to clean the optical elements, for example, the electrostatic clamp is used to clamp the cleaning device 10 to the support structure MT. Hence, the cleaning device 10 has the same position as the patterning device MA would have in an exposure process.

[0057] The cleaning device 10 can be handled in the same way as the patterning device MA.

For example, the same robot can be used to move the cleaning device 10 in the lithography apparatus 100. In an embodiment, the cleaning device 10 has the same shape, volume and clamping functionality as a standard EUV patterning device MA.

[0058] The cleaning device 10 is a separate component from the rest of the lithography apparatus 100. The cleaning device 10 can be used with an existing lithography apparatus 100 to improve its cleaning function. An existing lithography apparatus 100 can be retrofitted with the cleaning device 10.

[0059] By providing that the cleaning device 10 is configured to be clamped to the support structure MT, the cleaning device 10 can clean surfaces from the normal position of the patterning device MA. From this position, the cleaning device 10 can reach both the illumination system IL and the projection system PS with the decontamination radiation 8. A single cleaning device 10 can clean optical elements in both the illumination system IL and the projection system PS without needing to be moved.

[0060] In an embodiment the cleaning device 10 has the standard dimensions of a patterning device MA for EUV lithography. Patterning devices come in standard sizes and shapes.

[0061] A first nominal size for a patterning device MA is 6.0” x 6.0” x 0.25”. In an embodiment the cleaning device 10 has a side length of about 152mm. In an embodiment the cleaning device 10 has a side length of at least 151.6mm. In an embodiment the cleaning device 10 has a side length at most 152.4mm. In an embodiment the cleaning device 10 has a thickness of about 6.35mm. In an embodiment the cleaning device 10 has a thickness of at least 6.25mm. In an embodiment the cleaning device 10 has a thickness of at most 6.45mm.

[0062] A second nominal size of a patterning device MA is 6.0” x 6.0” x 0.15”. In an embodiment a cleaning device 10 has a thickness of about 3.80mm. In an embodiment the cleaning device 10 has a thickness of at least 3.70mm. In an embodiment the cleaning device 10 has a thickness of at most 3.90mm.

[0063] A third nominal size for a patterning device MA is 7.0” x 7.0” x 0.25”. In an embodiment the cleaning device 10 has a side length of about 177.4mm. In an embodiment the cleaning device 10 has a side length of at least 177.0mm. In an embodiment the cleaning device 10 has a side length or at most 177.8mm.

[0064] A fourth nominal size of a patterning device MA is 230mm x 230mm x 9mm. In an embodiment the cleaning device 10 has a side length of about 230mm. In an embodiment the cleaning device 10 has a side length of at least 229.6mm. In an embodiment the cleaning device 10 has a side length of at most 230.0mm. In an embodiment the cleaning device 10 has a thickness of about 9mm. In an embodiment the cleaning device 10 has a thickness of at least 8.90mm. In an embodiment the cleaning device 10 has a thickness of at most 9.10mm.

[0065] In an embodiment the cleaning device 10 has the same weight as a standard patterning device MA for EUV lithography. In an embodiment the cleaning device 10 weighs at least about 200g, and at most about lOOOg, for example about 300g or about 500g. In an embodiment the cleaning device 10 has a mass of at least about lOOg, and at most about 200g. In an embodiment the cleaning device 10 has a mass of at least lOOOg, and at most 2000g, for example about 1050g. [0066] In an embodiment the cleaning device 10 has a square shape in plan view. Of course, the sides of the cleaning device 10 may not have exactly the same length such that the cleaning device 10 does not have a perfectly square shape.

[0067] As depicted in Figure 4, in an embodiment the cleaning device 10 comprises an energy source 4. The energy source 4 is configured to supply energy to the radiation source 2 to supply the decontamination radiation 8. The energy source 4 is configured to power the cleaning device 10. In an embodiment the cleaning device 10 can power itself independently of the rest of the lithography apparatus 100.

[0068] In an embodiment the energy source 4 is a battery. For example, the energy source may be a lithium ion battery. In an embodiment the energy source 4 is rechargeable. For example, the energy source 4 may be charged by contact points between every usage. Alternatively, the energy source 4 may be recharged by contactless charging between every usage.

[0069] In an embodiment the lithography apparatus 100 comprises a library. The library is for storing the cleaning device 10. In an embodiment the library is configured to store one or more patterning devices MA in addition to the cleaning device 10. The library may store a plurality of the cleaning devices 10. This allows one cleaning device 10 to be used whilst the other is being recharged. This helps if, for example, the energy source 4 of a cleaning device 10 runs out before an optical element is fully cleaned.

[0070] In an embodiment the library comprises a charging station configured to charge the energy source 4 of the cleaning device 10. For example, the library may comprise contact points for charging the energy source 4. Additionally or alternatively the library may comprise a contactless charging station for charging the energy source 4.

[0071] Different cleaning devices 10 may be provided for supplying different types of decontamination radiation. For example, cleaning devices 10 may provide decontamination radiation 8 of different wavelengths or wavelength ranges. Additionally or alternatively different cleaning devices 10 may be configured to supply different doses of contamination radiation 8. Different cleaning devices 10 may be configured for supplying decontamination radiation 8 of different characteristics which may be suited for cleaning different elements. For example, one cleaning device 10 may be optimised for cleaning optical elements of the illumination system IL whilst another cleaning device 10 is optimised for cleaning optical elements of the projection system PS.

[0072] It is not essential for the energy source 4 to be a battery. For example, in an embodiment the cleaning device 10 comprises an induction coil. The induction coil is configured to receive power from an electromagnetic field. The induction coil is electrically connected to the radiation source 2 so as to supply energy to the radiation source 2 to supply the decontamination radiation 8. Inductive charging can be used for the energy source 4.

[0073] In an embodiment, the electrostatic clamp is provided with an induction coil configured to supply power to the cleaning device 10. The induction coil of the cleaning device 10 can couple to an induction coil in the electrostatic clamp. This allows the cleaning device 10 to be powered whilst the cleaning device 10 is supply decontamination radiation 8 for cleaning the optical elements.

[0074] As depicted in Figure 4, in an embodiment the cleaning device 10 comprises a focusing element 3. The focusing element 3 is configured to focus and direct the decontamination radiation 8 supplied by the radiation source 2. The decontamination radiation 8 is directed towards one or both of the illumination system IL and the projection system PS.

[0075] As shown in Figure 4, in an embodiment the cleaning device 10 comprises a controller 5. The controller 5 is configured to control the supply of decontamination radiation 8 by the radiation source 2. The light emission may be triggered automatically by the built-in controller 5. Alternatively, the light emission may be triggered manually.

[0076] As shown in Figure 4, in an embodiment the cleaning device 10 comprises a gas release module 6. The gas release module 6 is configured to supply a gas 9 out from the cleaning device 10. The cleaning device 10 is equipped with the gas release module 6 to spray a gas 9 in a controlled way. The gas 9 may be an active gas or a passive gas. In an embodiment the gas release module 6 is configured to release one or more of hydrogen, nitrogen and argon. The gas release module 6 can help to create a specific environment around the cleaning device 10. The gas 9 can be used to help clean or purge the lithography apparatus 100. The gas can help to pump away the desorbed water molecules.

[0077] However, it is not essential for the cleaning device 10 to be provided with the gas release module 6. For example, a cleaning or purging gas can be supplied by another part of the lithography apparatus 100.

[0078] Although specific reference may be made in this text to the use of lithography apparatus in the manufacture of ICs, it should be understood that the lithography apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion,” respectively. 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), a metrology tool and/or an 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 contains multiple processed layers. [0079] The term “lens,” where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

[0080] Although specific reference may be made in this text to EUV lithography apparatuses, it should be understood that the invention may also be used in other lithography apparatuses, e.g. in lithography apparatuses using deep ultraviolet (DUV) radiation or in e-beam lithography apparatuses.

[0081] Although specific reference may be made in this text to electrostatic clamping, it should be understood that the invention is not limited thereto and can also be used with other clamping methods, e.g. vacuum clamping or capillary clamping.

[0082] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the cleaning device 10 may have a shape other than square, such as circular or rectangular. In particular the shape of the cleaning device 10 may be selected depending on the shape of the patterning device MA.