Substrate restraint system

Abstract

The substrate constraint system comprises a substrate table and a plurality of circumferentially arranged constraints, each comprising a spring, the spring having a proximal end and a distal end, the distal end of the spring being radially displaceable, and a base of the proximal end of the spring being fixed to the substrate table at a fixed point.

Description

Technical Field

[0001] [Cross - reference to Related Applications] This application claims the benefit of priority of European Application No. 21160262.8, filed on March 2, 2021, the entire content of which is incorporated herein by reference.

[0002] [Technical Field] The present invention relates to a substrate clamping system, and more particularly to a substrate clamping system suitable for a lithographic apparatus.

Background Art

[0003] A lithographic apparatus is an apparatus for forming a desired pattern on a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus can project the pattern of a patterning device (e.g., a mask) onto a layer of radiation - sensitive material (resist) provided on a substrate.

[0004] To project a pattern onto a substrate, a lithographic apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features that can be formed on the substrate. A lithographic apparatus using extreme ultraviolet (EUV) having a wavelength in the range of 4 - 20 nm, for example 6.7 nm or 13.5 nm, can be used to form smaller features on a substrate than a lithographic apparatus using radiation having a wavelength of 193 nm.

[0005] Such a lithography apparatus may be provided with one or more clamps for clamping the substrate to the substrate table. The clamps may be, for example, mechanical clamps, vacuum clamps, or electrostatic clamps. An electrostatic clamp comprises electrodes (e.g., at least one electrode) and several barbs. The barbs protrude above the electrodes, and when the electrodes are switched on, the electrodes clamp the substrate to the barbs. Since the area of ​​the EUV lithography apparatus necessarily operates under near-vacuum conditions (meaning vacuum clamps cannot be used), electrostatic clamps may be particularly suitable for operation at EUV wavelengths.

[0006] While the substrate covers the top surface of the electrodes, the dielectric properties of the substrate prevent high-voltage discharge from the switched-on electrodes to adjacent modules of the lithography apparatus. However, if the substrate does not completely cover the electrodes, undesirable passchen-induced electrostatic discharge may occur, potentially causing high-voltage discharge from the switched-on electrodes to adjacent modules. Therefore, it may be desirable to ensure that the substrate always covers the electrodes when they are switched on.

[0007] A substrate restraint system may be used to prevent the substrate from covering the switched-on electrodes. The substrate restraint system comprises a plurality of restraints that function to prevent the substrate from not covering the electrodes by acting as a physical barrier. The substrate restraint system may restrict access to components on the substrate table, which may make it difficult to clean the substrate table in place. An object of at least one embodiment of at least one aspect of the present invention is to eliminate or at least mitigate at least one of the drawbacks of the prior art identified above. [Overview of the project] [Means for solving the problem]

[0008] According to a first aspect of the present invention, a substrate restraint system is provided comprising a substrate table and a plurality of restraints arranged circumferentially, each having a spring. The spring has a proximal end and a distal end. The distal end of the spring is radially displaceable. The base of the proximal end of the spring is fixed to the substrate table at a fixed location. The spring functions to prevent the substrate from not covering an electrode that has been switched on.

[0009] Advantageously, the substrate restraint system may provide the spring with enough travel to allow cleaning of the substrate table (for example, so that the restraint can move away from the bar on the substrate table) without the substrate failing to cover the switched electrodes directly beneath it. In other words, the substrate restraint system resolves the conflict between restraint requirements and cleaning requirements.

[0010] The spring may be a cantilever spring. For example, the spring may be fixed at its proximal end and freely displaceable at its distal end. Having a cantilever spring can improve the cleaning of the restraining part compared to, for example, a coil spring. This is because the area in which contaminating particles are trapped is reduced.

[0011] A cantilever spring may have at least one bent portion. A spring with at least one bent portion can reduce the rotational force applied to the substrate by the restraining portion. This is because, for example, the radial displacement of the spring more closely matches the displacement of the substrate.

[0012] Each restraint may be provided with an end stop for the distal end of the spring. The radial spacing of the end stops is greater than the radial spacing of the distal ends of the spring (i.e., measured from the center of the substrate table). This allows for setting the maximum radial displacement of the spring. For example, the maximum radial displacement of the spring may be such that it becomes impossible to prevent the substrate from covering the electrodes of the substrate table.

[0013] The radial displacement distance between the distal end of the spring and the end stop may be 1 mm or more. The radial displacement distance between the distal end of the spring and the end stop may be at least 0.5 mm. The radial displacement distance between the distal end of the spring and the end stop may be less than 5 mm.

[0014] The end stop may be the base of the proximal end of the spring. By having the base function as the end stop, the ease of mounting the restraint can be improved compared to when the spring and end stop are separate parts. This is because precise positioning of the spring is not required compared to when the end stop is used. Having the base function as the end stop can also improve the cleanability of the restraint because there are fewer parts to which contaminants can accumulate.

[0015] The end stop may be provided as a separate element on the substrate table. Having a separate end stop can reduce the number of contact points between the substrate and the restraint. This can reduce substrate contamination because there are fewer surfaces in contact with the substrate, and therefore fewer opportunities for contamination. Having a separate end stop can reduce the rotational force applied to the substrate because the end stop aligns with the radial displacement direction of the spring.

[0016] The endstop may be radially deformable. A radially deformable endstop can reduce the deceleration of the substrate when the endstop is used. Reducing the deceleration of the substrate can reduce damage to the substrate, substrate restraint system, or lithography apparatus compared to an endstop that is deformable in directions other than radially.

[0017] The spring may have a stiffness of 200 N / m or less. Having a spring stiffness of 200 N / m or less allows the cleaning stone to displace the spring radially during the cleaning process. The spring stiffness may be sufficiently low so as not to generate excessive contaminant particles due to friction between the outer edge of the cleaning stone and the restraining part during the cleaning process.

[0018] The spring may have a stiffness of 50 N / m or more. Having a spring stiffness of 50 N / m or more allows the spring to prevent the substrate from shifting and failing to cover the electrodes.

[0019] Multiple restraints may comprise three or more restraints. Having at least three restraints allows the substrate to be centered in two dimensions on the substrate table. The centering force may be applied to the substrate from each restraint. Providing more restraints may allow for a more consistent centering force to be applied to the substrate, for example, because for any direction of displacement of the substrate, there are restraints near the direction of the displaced substrate.

[0020] Each restraint may be made of metal. The metal may be, for example, stainless steel or Inconel for compatibility with EUV radiation. If EUV radiation compatibility of the restraint is not required, the restraint may be made of other materials, such as titanium or other metals.

[0021] According to a second aspect of the present invention, a lithography tool is provided comprising the substrate restraint system of the first aspect. The lithography tool may form part of a substrate handling tool used in a chemical vapor deposition (CVD) apparatus, an atomic layer deposition (ALD) apparatus, or other wafer (or other substrate) or mask (or other patterning device) processing apparatus. The lithography tool may be used under vacuum conditions or under atmospheric (non-vacuum) conditions.

[0022] The lithographic apparatus may comprise a cleaning stone having a friction reducing coating on its outer edge. During the cleaning process, the outer edge of the cleaning stone may rub against the restraint. The friction reducing coating may reduce contamination particles generated by the friction between the cleaning stone and the restraint. During the cleaning process, the substrate is not present on the electrostatic chuck and the electrostatic chuck is switched off. The cleaning stone is arranged, for example by an actuator, on the bar and rubs the upper surface of the bar to remove contamination particles.

[0023] The features described above in accordance with any aspect of the present disclosure, or the following features related to any particular embodiment of the present disclosure, may be used alone or in combination with other defined features in any other aspect or embodiment, or to form further aspects or embodiments of the present disclosure.

Brief Description of the Drawings

[0024] Embodiments of the invention are described below by way of example only, with reference to the accompanying schematic drawings. [Figure 1] FIG. shows a lithographic apparatus and a lithographic system comprising a radiation source. [Figure 2a] FIG. shows a top view of the substrate restraint system. [Figure 2b] FIG. shows a cross-sectional view of the substrate restraint system of FIG. 2a along the diameter of the substrate restraint system of FIG. 2a. [Figure 3] FIG. shows a top view of the restraint of the substrate restraint system of FIG. 2. [Figure 4] FIG. shows a top view of a first alternative restraint of the substrate restraint system of FIG. 2. [Figure 5] FIG. shows a top view of a second alternative restraint of the substrate restraint system of FIG. 2.

Embodiments for Carrying Out the Invention

[0025] Figure 1 shows a lithography system comprising a radiation source SO and a lithography apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and supply the EUV radiation beam B to the lithography apparatus LA. The lithography apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, a substrate table WT, and a cleaning stone CS. The substrate table WT comprises a plurality of restraints and an electrostatic clamp WB that functions to clamp the substrate. The electrostatic clamp WB further comprises a crowbar (not shown) and an electrode (not shown). The crowbar is configured to support the substrate W. The crowbar may have a curved top surface to reduce the area in contact with the substrate. The electrode functions to clamp the substrate W to the crowbar. The restraints R are configured to prevent the substrate from covering the electrode. The cleaning stone CS functions to clean the crowbar of the electrostatic clamp WB during the cleaning process. The cleaning stone may be cylindrical and may have a diameter of about 50 mm. The cleaning stone may have a thickness of approximately 10 mm.

[0026] During the cleaning process, the substrate W is not present on the electrostatic clamp WB, and the electrostatic clamp WB is switched off. The cleaning stone CS is positioned on a crowbar, for example by an actuator, and rubs against the top surface of the crowbar to remove contaminating particles. During the cleaning process, the outer edge of the cleaning stone CS may rub against the restraint. To reduce contamination caused by friction between the outer edge of the cleaning stone CS and the restraint R, the outer edge of the cleaning stone CS may be coated with a friction-reducing coating.

[0027] The illumination system IL is configured to adjust the EUV radiation beam B before it is incident on the patterning device MA. Furthermore, the illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. The faceted field mirror device 10 and the faceted pupil mirror device 11 cooperate to provide the EUV radiation beam B having a desired cross-sectional shape and a desired intensity distribution. In addition to, or instead of, the illumination system IL may include other mirrors or devices.

[0028] After being adjusted in this manner, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B' is produced. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. For this purpose, the projection system PS may include several mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W, which is held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thereby forming an image with features smaller than the corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is shown in Figure 1 to have only two mirrors 13, 14, the projection system PS may include a different number of mirrors (e.g., six or eight mirrors).

[0029] The substrate W may already contain a pattern. In this case, the lithography apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pattern already formed on the substrate W.

[0030] A small amount of gas (e.g., hydrogen) at a relative vacuum, i.e., a pressure considerably lower than atmospheric pressure, may be provided within the radiation source SO, the illumination system IL, and / or the projection system PS.

[0031] The radiation source SO shown in Figure 1 is of a type called, for example, a laser-generated plasma (LPP) source. The laser system 1, which may include, for example, a CO2 laser, is configured to energize a fuel, such as tin (Sn), supplied from, for example, a fuel emitter 3, via a laser beam 2. In the following description, we will refer to tin, but any suitable fuel may be used. The fuel may be, for example, in liquid form, or it may be, for example, a metal or alloy. The fuel emitter 3 may include a nozzle configured to eject, for example, tin. The laser beam 2 exists in the form of droplets along a trajectory toward the plasma-forming region 4. The laser beam 2 is incident on the tin in the plasma-forming region 4. As the laser energy accumulates in the tin, a tin plasma 7 is generated in the plasma-forming region 4. Radiation, including EUV radiation, is emitted from the plasma 7 during the de-excitation and recombination of ions and electrons in the plasma.

[0032] EUV radiation from the plasma is collected and focused by a collector 5. The collector 5 comprises, for example, a per-normal incident radiation collector 5 (sometimes more commonly called a normal incident radiation collector). The collector 5 may have a multilayer mirror structure configured to reflect EUV radiation (e.g., EUV radiation having a desired wavelength such as 13.5 nm). The collector 5 may have an ellipsoidal shape with two foci. As described below, the first of the foci may be in the plasma-forming region 4, and the second of the foci may be in the intermediate focus 6.

[0033] The laser system 1 may be spatially separated from the radiation source SO. In this case, the laser beam 2 may pass from the laser system 1 to the radiation source SO with the help of a beam delivery system (not shown) that includes, for example, a suitable guide mirror and / or beam expander and / or other optical systems. The laser system 1, the radiation source SO, and the beam delivery system may together be considered as a radiation system.

[0034] The radiation reflected by collector 5 forms EUV radiation beam B. EUV radiation beam B is focused at intermediate focus 6, forming an image at intermediate focus 6 of the plasma present in the plasma-forming region 4. The image at intermediate focus 6 functions as a virtual radiation source for the illumination system IL. Radiation source SO is positioned such that intermediate focus 6 is located at or near the aperture 8 of the surrounding structure 9 of radiation source SO.

[0035] Figure 1 shows the SO radiation source as a laser-generated plasma (LPP) source, but EUV radiation may be generated using any suitable radiation source such as a discharge-generated plasma (DPP) source or a free-electron laser (FEL).

[0036] Figure 2a shows a top view of the substrate restraint system. Figure 2b shows a cross-sectional view corresponding to cross-section X of the substrate restraint system in Figure 2a.

[0037] Figures 2a and 2b include a substrate table WT, a plurality of restraints R, and an electrostatic clamp WB. The electrostatic clamp comprises electrodes 23 and a plurality of crowbars 21, which are shown in the enlarged area of ​​Figure 2b. The crowbars 21 protrude above the electrodes 23.

[0038] The substrate W is provided on the substrate table WT. The lower surface of the electrostatic clamp WB is connected to the upper surface of the substrate table WT. The substrate W is positioned so that its lower surface is in contact with the crowbar 21.

[0039] Each restraining portion R is equipped with a spring that functions to apply a centering force to the substrate W when the substrate W is displaced radially toward the restraining portion R beyond the engagement distance from the center of the electrostatic clamp WB. The engagement distance is the distance between the outer edge of the substrate W and the nearest surface of the restraining portion R.

[0040] The substrate may slide across the bar 21, for example, during a levitation phenomenon. During the levitation phenomenon, the substrate W temporarily floats on a layer of gas above the bar 21, for example, on hydrogen gas. In other words, the levitation phenomenon can temporarily prevent the electrostatic clamp WB from clamping the substrate W, allowing the substrate W to not cover the switched-on electrode 23. To prevent the substrate from not covering the electrode 23, the restraint portion R should be within the effective restraint radius (when relaxed or in equilibrium). The effective restraint radius is the maximum radius from the center of the electrostatic clamp WB and is small enough to prevent the substrate W from not covering the electrode 23 for any displacement of the substrate W from the center of the electrostatic clamp WB. To prevent the substrate W from not covering the electrode 23, the restraint portion R provides a physical barrier to the outer edge of the substrate W.

[0041] Particles that may be present on the substrate W may be received on the crowbar (although most will fall between the crowbars). This will create an undesirable, so-called adhesion effect between the crowbar and the substrate W. These particles are removed during the cleaning process. The cleaning process may involve removing particles from the crowbar 21 using a cleaning stone CS. During the cleaning process, the cleaning stone CS may move across the edge of the electrostatic clamp WB, and it may be necessary that there are no obstacles, such as a restraining part R, within the effective cleaning radius.

[0042] The effective cleaning radius may be greater than the effective restraint radius. In other words, there is a conflict between the restraint requirements and the cleaning requirements in a substrate restraint system, which is addressed by embodiments of the present invention.

[0043] The substrate table WT, electrostatic clamp WB, and substrate W are shown as multiple axially aligned discs. The substrate table WT has a larger radius than the substrate W. The substrate W has a larger radius than the electrostatic clamp WB. Multiple restraints R are arranged circumferentially around the substrate W.

[0044] Each restraining part R is positioned such that its engagement distance is greater than zero, but small enough to keep the substrate within the effective restraining radius. When the substrate W is displaced radially from the center of the electrostatic clamp WB toward the restraining part R by at least the engagement distance (for example, during levitation), the outer edge of the substrate W will come into contact with the restraining part R. The restraining part R that the substrate W contacts will be displaced outward due to the spring properties of the restraining part R, and will apply a centering force to the substrate W.

[0045] The spring stiffness may function to apply a centering force to the substrate W that is large enough to prevent the substrate W from covering the electrode 23. Alternatively, the spring stiffness may function to apply a centering force to the substrate W that is large enough to decelerate the substrate W before the spring reaches its maximum displacement, with the maximum displacement of the spring being limited by the endstop. The endstop may apply the centering force directly to the substrate W. The endstop may also apply the centering force to the spring, and as a result, the centering force may be applied to the substrate W. Decelerating the substrate W before the spring reaches its maximum displacement can reduce damage to the substrate W, the substrate restraint system, or the lithography apparatus compared to a restraint R without a spring.

[0046] The spring stiffness is small enough that, during the cleaning process, the cleaning stone CS can displace the restraining part R, allowing the entire surface of the electrostatic clamp WB to be cleaned.

[0047] The spring stiffness is small enough to prevent the generation of excessive contaminating particles during the cleaning process due to friction between the outer edge of the cleaning stone CS and the restraining part R.

[0048] The radius of the substrate W may be 150 mm (i.e., a diameter of 300 mm). The thickness of the substrate W may be 1.0 ± 0.1 mm. The outermost bar may be positioned at a radius of at least 145 mm from the center of the electrostatic clamp. The outermost bar may be positioned at a radius of up to 149 mm. The engagement distance between the outer edge of the substrate W and the nearest surface of the restraint R may be at least 1 mm. The spring may be radially displaceable by at least 0.5 mm from its equilibrium position. The spring may be radially displaceable up to 5 mm from its equilibrium position.

[0049] The restraining portion R allows for precise centering of the substrate on the substrate table and may also allow the outermost crowbar to be cleaned (for example, by a cleaning stone during the cleaning process). This may allow for an increase in the maximum outer radius of the clamped electrode 23 without increasing the risk of the electrode 23 being uncovered. For example, the maximum outer radius range of the electrode 23 may increase from approximately 146 mm to approximately 148 mm.

[0050] The restraint portion R extends substantially perpendicularly from the substrate table WT. The upper surface of the restraint portion R may be sufficiently higher than the centerline of the substrate W, for example, in the case of a 1 mm thick substrate W, in order to prevent the substrate W from sliding on the upper surface of the restraint portion R. For example, the upper surface of the restraint portion R may be 0.4 mm or more above the upper surface of the crowbar, and is usually 0.5 mm or more above the upper surface of the crowbar.

[0051] The upper surface of the restraint portion R may be lower than the upper surface of the substrate W, for example, in a substrate W with a thickness of 1 mm. The upper surface of the restraint portion R may also be lower so as to be 0.8 mm or less above the upper surface of the crowbar. This can prevent the restraint portion R from colliding with a module adjacent to the substrate table WT in the lithography apparatus.

[0052] Figure 2a shows eight constraints R, but any number of constraints R, three or more, may be used. Having at least three constraints R allows the substrate to be centered in two dimensions on the substrate table.

[0053] The restraint portion R may be formed of a metal such as stainless steel or Inconel, for example, for compatibility with EUV radiation. If EUV radiation compatibility of the restraint portion R is not required, the restraint portion may be formed of another material, such as titanium or other metals.

[0054] Figure 3 shows a top view of the restraint portion R of the substrate restraint system. For example, the restraint portion R in Figure 3 may be used in the substrate restraint system of Figure 2. The restraint portion R comprises a spring 35. The spring 35 has a proximal end 33 and a distal end 37. The distal end 37 of the spring 35 is radially displaceable, for example, when the substrate W is pressed against the distal end 37 of the spring 35.

[0055] The proximal end 33 of the spring 35 is connected to the base 31. The base 31 is fixed to the upper surface of the circuit board table WT at a fixing point directly below the base 31. The length of the base 31 may be 20 mm or more. The width of the base 31 may be 20 mm or more. The area of ​​the base 31 is 400 mm². 2 The above is also acceptable. For example, the adhesive covering the area of ​​the base 31 is made strong enough to withstand the maximum load applied to the restraint R (as detailed below).

[0056] The length of the base 31 may be 50 mm or less. The width of the base 31 may be 50 mm or less. The area of ​​the base 31 is 2500 mm². 2 The following is also possible: For example, the base portion 31 may be made small enough to fit within the limited space on the substrate table WT.

[0057] These length, width, and area dimensions may apply to the base 31 of other embodiments of the present disclosure, as shown in Figures 4 and 5.

[0058] The fixing points are located on a radial line extending from the center of the electrostatic clamp WB through the base 31.

[0059] The spring 35 is a cantilever spring having one bend. The spring 35 is roughly U-shaped. The spring 35 is configured to extend from the base 31 in a first direction perpendicular to (i.e., across) the radial line before the spring 35 bends inward, and to extend along a second direction antiparallel to the first direction. Due to the bend, the distal end 37 and the proximal end 33 of the spring 35 are closer to each other than the length of the spring 35.

[0060] While the distal end 37 of the spring 35 is displaced radially, the base 31 functions as an end stop 31 to prevent radial displacement of the distal end 37 of the spring 35 that is greater than a desired maximum displacement. The desired maximum displacement may be at least 0.5 mm. The desired maximum displacement may be less than 5 mm. For example, the desired maximum displacement may be 1 mm.

[0061] The fact that the base portion 31 also functions as an end stop 31 can improve the ease of mounting the restraint portion R compared to when the spring 35 and the end stop 31 are separate parts. This is because precise positioning of the spring 35 is not required as much as that of the end stop 31.

[0062] The maximum applied load may occur while the end stop 31 is loading the cleaning stone CS. In other words, the maximum applied load occurs when the spring 35 is displaced to its maximum extent (i.e., at the end stop 31), at which point the end stop 31 prevents further radial displacement of the cleaning stone CS. The end stop 31 and the adhesive that secures the base area 31 to the substrate table WT may have sufficient strength to withstand the maximum applied force.

[0063] The thickness of spring 35 is selected so that the spring can elastically deform while providing the required stiffness. The required stiffness may be at least 50 N / m. The required stiffness may be 200 N / m or less. The spring stiffness may be 100 ± 10 N / m.

[0064] The distal end 37 of the spring 35 is shaped so that the substrate W contacts only a small area of ​​the distal end 37. For example, the distal end 37 of the spring 35 may have a surface that is convex in a plane parallel to the substrate table WT. The distal end may have a surface that is convex in a direction facing inward toward the substrate table WT. The convex shape can reduce friction between the substrate W and the distal end 37 of the spring 35. For example, the contact surface area between the spring and the substrate is reduced (compared to a flat or concave surface), resulting in less generation of contaminating particles.

[0065] Although one bend is mentioned, the spring may have any number of bends. The bends may be U-shaped, or they may be less U-shaped. Less U-shaped bends may increase the maximum displacement of the distal end 33 of the spring 35 compared to U-shaped bends.

[0066] The restraining portion R may consist only of a curved surface. In other words, in one embodiment, the restraining portion R does not have sharp edges. Sharp edges can provide corners from which contaminating particles cannot be removed (or are more difficult to remove), thus improving the cleanability of a restraining portion R with a curved surface.

[0067] Figure 4 shows a top view of a first alternative restraint R of the substrate restraint system. For example, the restraint R of Figure 4 may be used in the substrate restraint systems of Figures 2a and 2b. The restraint R comprises a spring 45. The spring 45 has a proximal end 43 and a distal end 47. The distal end 47 of the spring 45 is radially displaceable, for example, when the substrate W is pressed against the distal end 47 of the spring 45.

[0068] The proximal end 43 of the spring 45 is connected to the base 41. The base 41 is fixed to the upper surface of the substrate table WT at a fixing point directly below the base 41. The fixing point is located on a radial line extending from the center of the electrostatic clamp WB through the base 41.

[0069] The base portion 41 may function as an end stop 41. While the distal end 47 of the spring 45 is displaced radially, the end stop 41 may function to prevent radial displacement of the substrate W from exceeding a desired maximum displacement. The desired maximum displacement may be at least 0.5 mm. The desired maximum displacement may be less than 5 mm. For example, the desired maximum displacement may be 1 mm.

[0070] The maximum applied load may occur while the end stop 41 is loading the cleaning stone CS. In other words, the maximum applied load occurs when the spring 45 is displaced to its maximum extent (i.e., at the end stop 41), at which point the end stop 41 prevents further radial displacement of the cleaning stone CS. The end stop 41 and the adhesive that secures the base area 41 to the substrate table WT may have sufficient strength to withstand the maximum force applied.

[0071] The spring 45 is a flat, cantilevered spring. The spring 45 is configured to extend from the base 41 in a direction perpendicular to (i.e., across) the radial line. The length of the spring 45, and the distance between the distal end 47 and the proximal end 43 of the spring 45, may be a maximum of 10 mm. The length of the spring 45, and the distance between the distal end 47 and the proximal end 43 of the spring 45, may be at least 2 mm.

[0072] Using a flat, cantilevered spring can improve the cleanability of the restraint section R, for example, because it reduces the area from which contaminating particles can be trapped. Conversely, the inner region of a U-shaped spring may be difficult to clean of contaminating particles. Allowing the base 41 to function as an end stop can also improve the cleanability of the restraint section because it reduces the number of parts from which contaminating particles can adhere.

[0073] The thickness of spring 45 is selected so that the spring can elastically deform while providing the required stiffness. The required stiffness may be at least 50 N / m. The required stiffness may be 200 N / m or less. Specifically, the spring stiffness may be 100 ± 10 N / m.

[0074] The distal end 47 of the spring 45 is shaped so that the substrate W contacts only a small area of ​​the distal end 47. For example, the distal end 47 of the spring 45 may have a surface that is convex in a plane parallel to the substrate table WT. The distal end may have a surface that is convex in a direction facing inward toward the substrate table WT. The convex shape can reduce friction between the substrate W and the distal end 47 of the spring 45. For example, the contact surface area between the spring and the substrate is reduced (compared to a flat or concave surface), resulting in less generation of contaminating particles.

[0075] The restraining portion R may consist only of a curved surface. In other words, the restraining portion R does not have sharp edges. Sharp edges can provide corners from which contaminating particles cannot be removed (or are more difficult to remove), thus improving the cleanability of a restraining portion R with a curved surface.

[0076] Figure 5 shows a top view of a second alternative restraint R of the substrate restraint system. For example, the restraint R of Figure 5 may be used in the substrate restraint systems of Figures 2a and 2b. Figure 5 is identical to Figure 4, except that the substrate table WT of Figure 5 also includes a separate endstop 59 (i.e., an endstop formed as a separate element).

[0077] The end stop 59 may be a rounded column projecting vertically upward from the top surface of the substrate table WT. The end stop 59 may be cylindrical, a rounded cuboid, or another rounded shape. The rounding of the end stop 59 may reduce contact stress between the end stop and the spring. The rounding of the end stop may reduce the generation of contaminating particles. The rounding of the end stop 59 may improve cleaning performance, for example, by reducing the area over which contaminating particles can be trapped.

[0078] The length of the end stop 59 may be 20 mm or more. The width of the end stop 59 may be 20 mm or more. The area of ​​the end stop 59 is 400 mm². 2 The above may also be the case. For example, the adhesive covering the area of ​​the end stop 59 may have sufficient strength to withstand the maximum load applied to the restraint R.

[0079] The length of the end stop 59 may be 50 mm or less. The width of the end stop 59 may be 50 mm or less. The area of ​​the end stop 59 is 2500 mm². 2 The following may also be the case: for example, the end stop 59 may be made small enough to fit within the limited space on the PCB table WT.

[0080] The maximum applied load may occur while the end stop 59 is loading the cleaning stone CS. In other words, the maximum applied load occurs when the spring 45 is displaced to its maximum extent (i.e., at the end stop 59), at which point the end stop 59 prevents further radial displacement of the cleaning stone CS. The end stop 59 and the adhesive that secures the area of ​​the end stop 59 to the substrate table WT may have sufficient strength to withstand the maximum force applied.

[0081] In this embodiment, it is a separate end stop 59, not the base 41, that withstands the maximum applied load. Therefore, the area of ​​the base 41 may be smaller than in the embodiments of Figures 3 and 4. For example, the base 41 only needs to be large enough so that the adhesive fixing the area of ​​the base 41 to the substrate table WT is strong enough to withstand the force applied to the base 41 by the spring 45, rather than by the cleaning stone CS at its maximum displacement.

[0082] While the distal end 47 of the spring 45 is displaced radially, the end stop 59 functions to prevent radial displacement of the distal end 47 of the spring 45 greater than a desired maximum displacement. The desired maximum displacement may be at least 0.5 mm. The desired maximum displacement may be less than 5 mm. For example, the desired maximum displacement may be 1 mm.

[0083] Having a separate end stop 59 can reduce the number of contact points between the substrate W and the restraint. This reduces the surface area that the substrate W contacts, and therefore reduces the chance of contamination, thus reducing contamination of the substrate. Having a separate end stop 59 can reduce the rotational force applied to the substrate W because the end stop is aligned with the radial displacement direction of the spring.

[0084] While this document specifically refers to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described in this document may have other applications. Possible other applications include the manufacture of integrated optical systems, guide and detection patterns for magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), and thin-film magnetic heads.

[0085] While this document may specifically refer to embodiments of the present invention in the context of lithography apparatus, embodiments of the present invention may be used in other apparatuses. Embodiments of the present invention may form parts of mask inspection apparatuses, measuring apparatuses, or any apparatus for measuring or processing objects such as wafers (or other substrates) or masks (or other patterning devices). Embodiments of the present invention may form parts of substrate handling tools used in chemical vapor deposition (CVD) apparatuses, atomic layer deposition (ALD) apparatuses, or other wafer (or other substrate) or mask (or other patterning device) processing apparatuses. These apparatuses may generally be called lithography tools. Such lithography tools may operate under vacuum conditions or atmospheric (non-vacuum) conditions.

[0086] While the above may have specifically mentioned the use of embodiments of the present invention in the context of photolithography, it will be understood that, to the extent the context allows, the present invention is not limited to photolithography and can be used in other applications, such as imprint lithography.

[0087] While specific embodiments of the present invention have been described above, it will be understood that the present invention may be carried out in ways other than those described. The above description is intended to be illustrative and not limiting. Accordingly, it will be apparent to those skilled in the art that modifications to the described invention may be made without departing from the following claims.

Claims

1. The substrate table comprises a crowbar configured to support the substrate, and a plurality of restraining parts, each equipped with a spring and arranged circumferentially, The spring has a proximal end and a distal end, The distal end of the spring is displaceable in the radial direction. The base of the proximal end of the spring is fixed to the substrate table at a fixed location. Substrate restraint system.

2. The aforementioned spring is a cantilever spring. The substrate restraint system according to claim 1.

3. The cantilever spring has at least one bent portion. The substrate restraint system according to claim 2.

4. Each restraint portion is provided with an end stop for the distal end of the spring, The radial distance of the end stops, measured from the center of the substrate table, is greater than the radial distance of the distal ends of the springs, measured from the center of the substrate table. A substrate restraint system according to any one of claims 1 to 3.

5. The radial displacement distance between the distal end of the spring and the end stop is 1 mm or more. The substrate restraint system according to claim 4.

6. The end stop is the base of the proximal end of the spring. The substrate restraint system according to claim 4 or claim 5.

7. The end stop is provided as a separate element on the substrate table. The substrate restraint system according to claim 4 or claim 5.

8. The end stop is deformable in the radial direction. A substrate restraint system according to any one of claims 4 to 7.

9. The spring has a rigidity of 200 N / m or less. A substrate restraint system according to any one of claims 1 to 8.

10. The spring has a rigidity of 50 N / m or more. A substrate restraint system according to any one of claims 1 to 9.

11. The aforementioned plurality of restraining parts comprises three or more restraining parts. A substrate restraint system according to any one of claims 1 to 10.

12. Each restraining part is made of metal. A substrate restraint system according to any one of claims 1 to 11.

13. A lithography apparatus or semiconductor manufacturing apparatus comprising a substrate restraint system according to any one of claims 1 to 12.

14. The lithography apparatus or semiconductor manufacturing apparatus includes a cleaning stone. The lithography apparatus or semiconductor manufacturing apparatus according to claim 13.

15. The lithography apparatus or semiconductor manufacturing apparatus has a friction-reducing coating on the outer edge of the cleaning stone, The lithography apparatus or semiconductor manufacturing apparatus according to claim 14.

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