TECHNICAU FIEUD

[0001] Embodiments of the present disclosure relate to an apparatus for reducing deposition of contaminating molecules on a substrate, particularly a large area substrate. Embodiments relate to charged particle beam systems having such an apparatus. Aspects of the present disclosure relate to methods for reducing deposition of contaminating molecules on a substrate.

BACKGROUND

[0002] A current trend is the manufacture of an increasing number of electronic and particularly optoelectronic devices on substrates, e.g. in order to provide displays, circuit boards and/or solar cells. In particular, there is an increasing demand for flat display elements such as flat screens. The standards for liquid crystal displays (LCD) and other display elements, in which control elements, for example thin film transistors (TFTs), are used, increase. In addition, the increasing resolution of displays leads to decreasing structure dimensions (critical dimensions) and to a decreased layer thickness which raises the sensitivity for defects of such display devices.

[0003] Defects may be induced by the presence of contaminating molecules on a sample during manufacturing of electronic devices. Molecules adsorbed to a sample can change surface properties of the sample. In particular, the surface wettability may be reduced. Subsequent processing may be negatively affected. Accordingly, it would be beneficial to reduce the number of contaminating molecules deposited on samples. SUMMARY

[0004] According to an embodiment, an apparatus is provided for reducing deposition of contaminating molecules on a substrate positioned in a vacuum chamber on a stage. The stage has at least a first dimension. The apparatus includes an illumination module facing the stage from a first side and extending along at least 80% of the first dimension. The illumination module is positioned to illuminate a volume above the substrate and comprises a light source for emitting UV radiation. The apparatus further includes an absorption module facing the stage from a second side opposite the first side, and extending along at least 80% of the first dimension.

[0005] According to an embodiment, a charged particle beam system is provided. The charged particle beam system includes a charged particle beam microscope configured for imaging a portion of a substrate provided in a vacuum chamber. The charged particle beam system further includes an apparatus for reducing deposition of contaminating molecules on a substrate, according to embodiments described herein.

[0006] According to an aspect, a method is provided for reducing deposition of contaminating molecules on a substrate positioned on a stage in a vacuum chamber. The method includes illuminating a volume above the substrate with UV radiation, wherein the volume has a base of at least 80% of an area of the substrate and a height of at least 5 mm. The method further includes absorbing at least a part of the UV radiation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] So that the features recited above can be understood in detail, a more particular description of the subject matter briefly summarized above may be provided below by reference to embodiments. The accompanying drawings relate to embodiments and are described in the following:

FIG. 1 is a schematic side view of an apparatus for reducing deposition of contaminating molecules on a substrate according to embodiments of the present disclosure; FIG. 2 is a schematic top view of an apparatus for reducing deposition of contaminating molecules on a substrate according to embodiments of the present disclosure;

FIG. 3 shows a charged particle beam system according to embodiments of the present disclosure, including an apparatus for reducing deposition of contaminating molecules on a substrate; and

FIG. 4 shows a flowchart illustrating methods for reducing deposition of contaminating molecules on a substrate according to embodiments of the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0008] Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. The structures shown in the drawings serve for better understanding of the embodiments and are not necessarily depicted true to scale. Each example is provided as an explanation and is not meant as a limitation. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

[0009] The term “substrate” as used herein embraces both inflexible substrates, e.g., a glass substrate, or a glass plate, and flexible substrates, such as a web or a foil. The substrate may be a coated substrate, wherein one or more thin layers of materials are coated or deposited on the substrate, for example by a physical vapor deposition (PVD) process or a chemical vapor deposition process (CVD).

[0010] Embodiments described herein relate to large area substrates, in particular large area substrates for the display market. According to some embodiments, large area substrates or respective substrate supports may have a size of at least 1 m ² . The size may be from about 1.375 m ² (1100 mm x 1250 mm - GEN 5) to about 9 m ² , more specifically from about 2 m ² to about 9 m ² or even up to 12 m ² . The substrates or substrate receiving areas, for which the structures, apparatuses, and methods according to embodiments described herein are provided, can be large area substrates as described herein. For instance, a large area substrate or carrier can be GEN 5, which corresponds to about 1.375 m ² substrates (1.1 m x 1.25 m), GEN 7.5, which corresponds to about 4.39 m ² substrates (1.95 m x 2.25 m), GEN 8.5, which corresponds to about 5.7m ² substrates (2.2 m x 2.5 m), or even GEN 10, which corresponds to about 9 m ² substrates (2.88 m x 3130 m). Even larger generations such as GEN 11 and GEN 12 and corresponding substrate areas can similarly be implemented.

[0011] Embodiments of the present disclosure relate to an apparatus for reducing deposition of contaminating molecules on a substrate. The apparatus is configured for reducing deposition of contaminating molecules on a substrate positioned on a stage in a vacuum chamber, particularly a substrate positioned on a stage in a vacuum chamber. Particularly, an apparatus according to the present disclosure is suitable and configured for large area substrates, for example substrates having a size of 1.4 m ² or larger, such as 5 m ² or larger. For example, the vacuum chamber can have a slit valve, e.g. for vacuum tight sealing of the vacuum chamber, and configured for loading of a large area substrate.

[0012] An apparatus according to the present disclosure can be provided for display manufacturing, for example for LCD displays or OLED displays. Further, glass handling of large area substrates can be improved due to reduced risk of deposition of contaminating molecules. According to yet further embodiments, reduction of deposition of contaminating molecules on flexible substrates, such as webs or foils, can be provided. This may for example be used, according to some embodiments, for manufacturing flexible displays.

[0013] An apparatus for reducing deposition of contaminating molecules on a substrate can include a light source, such as a vacuum UV (VUV) light source. For example, a VUV light source can reduce deposition of contaminating molecules on a substrate in vacuum environments.

[0014] UV radiation is able to disassemble longer molecules, particularly hydrocarbons, into shorter fragments. The shorter fragments have a lower likelihood of sticking to surfaces. A UV radiation source can reduce the number of “sticky” long molecules and therefore the contamination of the substrate. [0015] FIG. 1 is a schematic side view of an apparatus for reducing deposition of contaminating molecules on a substrate. The apparatus 100 is positioned in a vacuum chamber 140. The substrate 150 is positioned on a stage 142 having at least a first dimension. The first dimension may be a distance between two opposite edge segments of the stage 142.

[0016] In the case of a rectangular stage, the first dimension may be a length of a short edge of the stage. In the case of a round stage, particularly for a wafer, the first dimension may be a diameter of the stage. The substrate may be for example a rectangular substrate or a round wafer. The substrate may be a large area substrate.

[0017] The apparatus includes an illumination module 110 facing the stage 142 from a first side. The illumination module 110 is positioned to illuminate a volume above the substrate 150. The illumination module includes a light source for emitting UV radiation. In embodiments, the light source may be configured to emit a radiation having a wavelength larger than 145 nm and smaller than 175 nm. The wavelength may be for example 155, 160 or 165 nm. The apparatus includes an absorption module 120 facing the stage 142 from a second side opposite the first side. In embodiments, the absorption module may extend along at least 70, 80 or 90% of the first dimension.

[0018] Generally, UV radiation can damage substrates, particularly at high intensities or energy doses. Irradiation of the substrate is to be avoided. The absorption module can aid in mitigating or eliminating substrate exposure to UV radiation.

[0019] In embodiments, the illumination module 110 extends along at least 70, 80 or 90% of the first dimension. The UV radiation may be directed parallel to a surface of the stage 142. In embodiments, the illuminated volume may have a base corresponding to at least the substrate area or corresponding to at least the stage area. The illuminated volume may have a height of for example 15, 20, or 25 mm.

[0020] The illumination module 110 may be configured to illuminate the volume above the substrate 150 such that the substrate is substantially free from the UV radiation. In embodiments, the light source may have a length of at least 70, 80 or 90% of the first dimension. The light source may be an elongated light source. [0021] A volume above the substrate and spanning the whole surface of the substrate is illuminated with UV radiation without irradiating the substrate. The whole volume is irradiated simultaneously. The volume to be illuminated is located in proximity to the substrate. Long molecules, particularly hydrocarbons, may be disassembled by the UV radiation within the illuminated volume.

[0022] In embodiments, the illumination module 110 may include a beam guiding unit 112 for distribution of the UV radiation over at least 80% of the first dimension. The beam guiding unit 112 may be configured to modify at least one of a beam width or a beam direction of the UV radiation emitted by the light source. The beam guiding unit 112 may include a beam expander. The beam guiding unit may include a collimator. The beam guiding unit 112 may be configured to direct the UV radiation into a volume above the substrate 150, particularly only into the volume above the substrate 150.

[0023] In embodiments, the apparatus may include a beam blanking element 115 positioned between the illumination module 110 and the stage 142 for protection of the substrate 150 against the UV radiation. The beam blanking element is configured to block a portion of the UV radiation. The portion to be blocked reduces the intensity of UV radiation impinging on the substrate.

[0024] In embodiments, a maximum intensity of the UV radiation in the volume above the substrate 150 may be lower than for example 3750, 3000, or 2250 pW/cm ² . A minimum intensity of the UV radiation in the volume above the substrate may be higher than for example 75, 100 or 125 pW/cm ² .

[0025] The UV radiation can reduce deposition of contaminating molecules, particularly of long contaminating molecules. A change of the surface properties of the substrate may be avoided. In particular, a reduction of the surface wettability of the substrate may be avoided. Negative effects on subsequent processing may be prevented.

[0026] Generally, substrates exposed to vacuum on a timescale of for example several minutes up to several hours may be contaminated by residual gas molecules in the vacuum environment. The contaminating molecules can be hydrocarbons. Longer molecules stick to the substrate surface due to the Van der Waals force. For shorter molecules, the Van der Waals force is generally lower. Shorter molecules have a shorter residence time and are more volatile. Accordingly, shorter molecules can be pumped away.

[0027] Longer molecules in the vacuum environment can hit the substrate surface and immediately adsorb due to a high sticking coefficient and long desorption times. The adsorbed molecules change the surface properties, reducing the surface wettability. Subsequent processing may be negatively affected. Particularly negative effects can be expected if the subsequent processing is wet processing such as photo resist coating. UV radiation is able to disassemble longer molecules into shorter fragments. A UV radiation source can reduce the number of “sticky” long molecules and therefore the contamination of the substrate.

[0028] Irradiating mainly or only a volume above the substrate, as opposed to irradiating the substrate, has the advantage that damage to the substrate may be prevented. Generally, UV radiation can damage substrates, particularly at high intensities or energy doses.

[0029] The problems mentioned above may be solved by an apparatus for reducing deposition of contaminating molecules on a substrate positioned in a vacuum chamber on a stage, the stage having at least a first dimension. The apparatus includes an illumination module facing the stage from a first side and extending along at least 80% of the first dimension, wherein the illumination module is positioned to illuminate a volume above the substrate and comprises a light source for emitting UV radiation. The apparatus further includes an absorption module facing the stage from a second side opposite the first side, and extending along at least 80% of the first dimension.

[0030] In other words, an illumination module may be configured to emit UV radiation into a volume located above the substrate such that a plane having an area of for example at least 70, 80 or 90% of the substrate’s area is simultaneously traversed by the UV radiation. The absorption module may be configured to absorb for example at least 70, 80, or 90% of the radiation emitted by the illumination module.

[0031] In embodiments, the apparatus includes a controller configured to induce the illumination module 110 to continuously illuminate the volume above the substrate 150 for as long as the substrate is on the stage. [0032] The substrate 150 may be movable within the vacuum chamber by a drive 160. Additionally or alternatively, the drive 160 can be utilized to move the substrate 150 into the vacuum chamber 140 or out of the vacuum chamber 140. According to other modifications, a substrate may be loaded with a robot having a robot arm into the vacuum chamber or out of the vacuum chamber.

[0033] In the context of the present disclosure, a stage may be understood for example as a substrate support or a substrate support table. According to some embodiments, which can be combined with other embodiments described herein, a substrate support can be a vacuum chuck or an electrostatic chuck. For example, an electrostatic chuck can hold the substrate due to electrostatic attracting forces and may be used for systems for display manufacturing.

[0034] According to some embodiments, a substrate 150 may be stationary, for example on a stage 142, as shown in FIG. 1, while a volume above the substrate 150 is illuminated by the apparatus 100 for reducing deposition of contaminating molecules. According to further embodiments, which can be combined with other embodiments of the present disclosure, the substrate 150 can be moved through a vacuum chamber 140 during illumination of a volume above the substrate 150 with an apparatus 100 for reducing deposition of contaminating molecules. This is indicated by arrow 170 in FIG. 2. For example, a substrate can be moved continuously or quasi-continuously through a vacuum chamber 140 while a volume above the substrate is illuminated with UV radiation. The UV radiation can be generated with an apparatus according to embodiments described herein or can be generated via methods according to aspects described herein.

[0035] FIG. 2 is a schematic top view of an apparatus for reducing deposition of contaminating molecules on a substrate. The apparatus corresponds at least substantially to the apparatus shown in FIG. 1. In the view depicted in FIG. 2, the substrate 150 positioned on the stage 142 can be seen from above. The illumination module 110 faces the stage 142 from a first side. The absorption module 120 faces the stage 142 from a second side opposite the first side. On the remaining two sides of the exemplary stage shown in FIG. 2, two edges of the stage 142 can be seen. A distance between the two edges of the stage may be a first dimension of the stage. [0036] Generally, an illumination module may extend along at least 80% of the first dimension. As can be seen in the example shown in FIG. 2, the illumination module 110 extends along more than 100% of the first dimension. Similarly, an absorption module may extend along at least 80% of the first dimension. The absorption module 120 shown in FIG. 2 extends along more than 100% of the first dimension.

[0037] FIG. 3 shows a charged particle beam system according to embodiments of the present disclosure, including an apparatus 100 for reducing deposition of contaminating molecules on a substrate. The apparatus 100 may correspond at least substantially to the apparatus described with regard to FIG. 1. The charged particle beam system includes a charged particle beam microscope 300 configured for imaging a portion of a substrate 150 provided in a vacuum chamber 140.

[0038] Without limiting the scope of the present disclosure, in the following a charged particle beam system, e.g. a charged particle beam microscope, or components thereof will exemplarily be referred to as a charged particle beam system including the detection of secondary or backscattered particles, such as electrons. Embodiments can still be applied for apparatuses and components detecting corpuscles, such as secondary and/or backscattered charged particles in the form of electrons or ions, photons, X-rays or other signals in order to obtain a specimen image. When referring to corpuscles, the corpuscles are to be understood as light signals in which the corpuscles are photons as well as particles, in which the corpuscles are ions, atoms, electrons or other particles. As described herein, discussions and descriptions relating to the detection are exemplarily described with respect to electrons in scanning electron microscopes. Other types of charged particles, e.g. positive ions, could be utilized by the device in a variety of different instruments.

[0039] According to embodiments herein, which can be combined with other embodiments, a signal (charged particle) beam, or a signal (charged particle) beamlet is referred to as a beam of secondary and/or backscattered particles. Typically, the signal beam or secondary beam is generated by the impingement of the primary beam or primary beamlet on a specimen. A primary charged particle beam or a primary charged particle beamlet is generated by a particle beam source and is guided and deflected on a specimen to be inspected or imaged. [0040] Charged particle beam systems such as SEM based inspection systems use vacuum test chambers to inspect or test samples. The samples may be exposed to vacuum on a timescale of for example several minutes up to several hours. During the vacuum exposure time, the samples may be contaminated by residual gas molecules in the vacuum environment, mostly hydrocarbons. Providing a charged particle beam system with an apparatus for reducing deposition of contaminating molecules as described herein may be particularly beneficial. In addition to the advantages detailed in the description of FIG. 1, carbonization effects during inspection may be reduced. In this context, inspection may particularly be understood as an electron beam scan. Generally, hydrocarbons can interact with the charged particle beam, particularly electron beam, to produce a carbonization layer. A measurement of critical dimensions may be negatively affected.

[0041] An electron beam (not shown) may be generated by the electron beam source 312. Within the gun chamber 310, further devices for beam shaping like a suppressor, an extractor, and/or an anode may be provided. The electron beam source can include a TFE emitter. The gun chamber may be evacuated to a pressure of 10 ⁸ mbar to 10 ⁹ mbar. In embodiments, the charged particle beam microscope may be an electron beam prober or an electron beam tester. The charged particle beam microscope may be for electron beam testing or electron beam review of a substrate.

[0042] In a further vacuum chamber 320 of the column of the charged particle beam microscope 300, a condenser lens can be provided. Further electron optical elements can be provided in the further vacuum chamber. The further electron optical elements can be selected from the group consisting of: a stigmator, correction elements for chromatic and/or spherical aberrations, and alignment deflectors for aligning the primary charged particle beam to an optical axis of the objective lens 340.

[0043] The primary electron beam can be focused on the substrate 150 by the objective lens 340. The substrate 150 is positioned on a substrate position on the stage 142. On impingement of the electron beam onto the substrate 150, signal electrons, for example, secondary and/or backscattered electrons, and/or x-rays, are released from the substrate 150, which can be detected by a detector 339. [0044] In the exemplary embodiments described with respect to FIG. 3, a condenser lens 323 is provided. A two-stage deflection system (not shown) can be provided between the condenser lens and e.g. a beam limiting aperture, e.g. a beam shaping aperture, for alignment of the beam to the aperture. As shown in FIG. 3, the objective lens 340 can have a magnetic lens component having pole pieces, and having a coil. The objective lens focuses the primary electron beam on the substrate 150. Further, an upper electrode 352 and a lower electrode 354 form an electrostatic lens component of the objective lens 340. The lower electrode 354 is connected to a voltage supply (not shown). The lower electrode being the deceleration electrode of the immersion lens component, i.e. a retarding field lens component, of the objective lens is typically at a potential to provide a landing energy of the charged particles on the substrate of 2 keV or below, e.g. 500 V or 1 keV. The objective lens can be an electrostatic-magnetic compound lens having e.g. an axial gap or a radial gap, or the objective lens can be an electrostatic retarding field lens.

[0045] Further, a scanning deflector assembly can be provided. The scanning deflector assembly can, for example, be a magnetic, but preferably an electrostatic scanning deflector assembly, which is configured for high pixel rates. The scanning deflector assembly may be a single stage assembly. Alternatively, also a two-stage or even a three-stage deflector assembly can be provided for scanning. Each stage may be provided at a different position along the optical axis.

[0046] The charged particle beam microscope 300 shown in FIG. 3 includes a detector 339 in a detection vacuum area 330. The detector 339 includes a scintillator arrangement. The scintillator arrangement has an opening (not shown), for example an opening in the center of the scintillator arrangement. The opening serves for having the primary charged particle beam path through the detector. The scintillator arrangement can be segmented to have two or more scintillator segments.

[0047] FIG. 4 shows a flowchart illustrating methods for reducing deposition of contaminating molecules on a substrate, particularly a large area substrate, according to aspects of the present disclosure. The flowchart further illustrates methods of operating an apparatus for reducing deposition of contaminating molecules, according to embodiments of the present disclosure. [0048] The exemplary illustrated method is for reducing deposition of contaminating molecules on a substrate positioned on a stage in a vacuum chamber. The method includes illuminating a volume above the substrate with UV radiation, indicated by block 402. The UV radiation may be directed at least substantially parallel to a surface of the stage.

[0049] According to an aspect of the present disclosure, the volume may have a base of at least 70, 80, or 90% of an area of the substrate. The volume may have a base of at least 70, 80, or 90% of an area of the stage. The volume may have a height of at least 5, 15, or 20 mm. The volume may have a height of less than 30, 50, or 70 mm.

[0050] As indicated by block 404, the method further includes absorbing at least a part of the UV radiation, particularly with an absorption module. For example, at least 60, 75, or 90% of the UV radiation may be absorbed.

[0051] According to an aspect of the present disclosure, the method may include protecting the substrate against the UV radiation with a beam blanking element. The beam blanking element may be positioned between an illumination module and the stage.

[0052] The present disclosure has several advantages including a reduction of deposition of contaminating molecules, with the capability to operate in vacuum and/or a capability to operate for large area substrates, particularly for substrates having a size of 1.4 m ² or above or substrates having a size of 5.7 m ² or above. Reducing a deposition of contaminating molecules as described herein can be particularly advantageous for imaging with a charged particle microscope, such as an SEM based inspection system.

[0053] While the foregoing is directed to some embodiments, other and further embodiments may be devised without departing from the basic scope of the disclosure. The scope is determined by the claims that follow.