lithography equipment

Abstract

A lithographic apparatus comprises: a clamping surface for supporting a substrate, wherein a property of the clamping surface is defined by at least one clamping surface parameter, and wherein the property of the clamping surface has been selected to exhibit low wear; a clamping apparatus for actuating a clamping operation between the clamping surface and the substrate, wherein the clamping operation is defined at least in part by at least one interface property between the clamping surface and the substrate; and a processing station operable to apply an adjustment to a first property of the substrate based on the clamping surface parameter and at least one substrate surface parameter defining a second property of the substrate to optimize the at least one interface property for a particular clamping operation.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 19184960.3, filed on July 8, 2019, which is incorporated herein by reference. Technical Field

[0003] The present invention relates to a lithographic apparatus. In particular, the present invention relates to a lithographic apparatus having a processing station operable to apply a condition to a substrate. Background Art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern to a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus can project a pattern, for example at a patterning device (e.g., a mask), onto a layer of radiation-sensitive material (resist) disposed on a substrate.

[0005] To project a pattern onto a substrate, a lithographic apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on the substrate. Typical wavelengths currently used are 365nm (i-line), 248nm, 193nm, and 13.5nm. Compared to lithographic apparatuses using, for example, radiation with a wavelength of 193nm, lithographic apparatuses using extreme ultraviolet (EUV) radiation with a wavelength in the range of 4 to 20nm (e.g., 6.7nm or 13.5nm) can be used to form smaller features on a substrate.

[0006] The patterning device and / or substrate are typically held in position in the lithographic apparatus by clamping them to a clamping surface, for example, using a vacuum or electrostatic forces. The clamping strength must be sufficient to hold the patterning device and / or substrate in position. It is known that clamping can cause deformation of the patterning device and / or substrate.

[0007] It may be desirable to provide a method and apparatus for improved clamping operations to overcome one of the disadvantages associated with clamping a patterning device or substrate, be they the above or other disadvantages.It may be desirable to provide an alternative method or apparatus for clamping a patterning device or substrate. Summary of the Invention

[0008] According to a first aspect of the present invention, there is provided a lithographic apparatus comprising: a clamping surface for supporting a substrate, wherein a property of the clamping surface is defined by at least one clamping surface parameter; a clamping apparatus for actuating a clamping operation between the clamping surface and the substrate, wherein the clamping operation is defined at least in part by at least one interface property between the clamping surface and the substrate; and a processing station operable to apply an adjustment to a first property of the substrate based on the clamping surface parameter and at least one substrate surface parameter defining a second property of the substrate to optimize the at least one interface property for a particular clamping operation. The property of the clamping surface may have been selected to exhibit low wear.

[0009] The substrate can be, for example, a wafer, a mask, a reticle, or other substrate within a lithographic apparatus. Previous attempts to optimize interface properties have primarily focused on controlling clamping surface parameters, for example because the user has relatively free choice regarding the substrate used in the clamping operation. Instead, it has been recognized that interface properties can be optimized more effectively by applying adjustments to the substrate than by considering only the clamping surface.

[0010] Advantageously, by applying adjustments to the substrate based on the clamping surface parameters, the interface properties can be optimized while retaining the low-wear properties of the clamping surface. The clamping surface exhibiting properties desirable for low wear (e.g., smoothness and / or stiffness and / or hardness) often results in other interface properties being suboptimal. By providing a processing station to apply adjustments to the substrate, the low-wear clamping surface can be retained while optimizing other interface properties. The interface properties to be optimized can vary depending on the user's requirements.

[0011] Optimizing interface properties can include reducing deformation of the substrate during loading operations. Thus, optimizing interface properties can minimize stress and / or deformation of the substrate, subsequently mitigating optical issues such as overlay issues. Mitigating optical issues can be beneficial in improving the quality and yield of photolithography processes.

[0012] Optimizing interface properties can include increasing the strength of the clamping operation. For example, after a substrate has been clamped to a clamping surface, such as during a scanning operation in a lithographic apparatus, it can be accelerated. In applications with high acceleration, increasing the clamping strength can be beneficial, for example to improve positional control of the substrate during a scanning operation.

[0013] Optimizing interface properties can include increasing the efficiency of the unloading operation (ie, releasing the substrate from the clamping surface).

[0014] Optimizing the interface properties may include further reducing wear on the clamping surfaces. Thus, optimizing the interface properties may increase the lifespan of the clamping surfaces. Typically, each substrate undergoes far fewer clamping operations than the clamping surfaces (e.g., each substrate undergoes approximately 100 clamping operations, compared to approximately 10 million clamping operations per clamping surface). Increasing the lifespan of the clamping surfaces may be beneficial in reducing costs, reducing maintenance frequency, and increasing the reliability of the lithographic apparatus.

[0015] Different optimization requirements can conflict with each other. For example, high friction between the clamping surface and the substrate may be beneficial for increasing clamping strength but detrimental to reducing substrate deformation and wear on the clamping surface. Furthermore, user requirements can change, for example during different lithography processes. This specification describes an apparatus and method by which interface properties can be optimized for a range of requirements while maintaining low-wear properties on the clamping surface.

[0016] The substrate can be a reticle, mask, or wafer, such as a reticle or wafer associated with a lithographic exposure, or any other substrate within a lithographic apparatus. The first property of the substrate and the second property of the substrate can be the same property. The substrate surface parameter(s) can be measured, or they can be known.

[0017] The lithographic apparatus may further comprise a processing apparatus configured to determine a surface parameter of the substrate defining a second property of the substrate. The processing station may comprise the processing apparatus. The processing apparatus may be, for example, a metrology apparatus. The processing apparatus may be any measuring device.

[0018] The first property and / or the second property may be selected from the group consisting of hardness, stiffness, roughness, geometry, work function, chemical surface state, surface energy, surface charge, wettability, hydrophobicity, surface particle density, and lubricity.

[0019] The adjustment may also be based on at least one clamping parameter that at least partially defines the clamping operation.

[0020] The clamping parameters may be, for example, speed, force, or acceleration associated with the clamping operation. The clamping parameters may refer to a loading operation (i.e., the substrate first contacts the clamping surface and is clamped together), a scanning acceleration (i.e., the substrate is moved in response to movement of the clamping surface, such as in a scanning movement associated with a lithographic exposure), or an unloading operation (i.e., the substrate is released from the clamping surface).

[0021] Different clamping operations may have different clamping parameters, for example they may advantageously have different speeds.By applying adjustments in view of the clamping parameters, the interface properties between the substrate and the clamping surface may be further optimized.

[0022] The properties of the clamping surface may include at least one of the following: a hardness greater than 20 GPa, a stiffness greater than 200 GPa, a surface roughness less than 3 nm RMS, a strength less than 25 mJ / m 2 surface energy.

[0023] Advantageously, the clamping surface can be hard and / or smooth and / or rigid and / or have low surface energy. It may be desirable to select the properties of the clamping surface to exhibit lower wear than typical substrates (e.g., silicon substrates). The properties of the clamping surface can be defined by clamping surface parameters. Stiffness can be measured as Young's modulus.

[0024] Advantageously, a hardness greater than 20 GPa can reduce wear on the clamping surface. Alternatively, the hardness can be greater than 40 GPa. The hardness can be measured, for example, using the Vickers hardness scale. Advantageously, a Young's modulus greater than 200 GPa can reduce wear on the clamping surface. Alternatively, the Young's modulus can be greater than 250 GPa. For example, boron nitride can have a hardness of 48 GPa and a Young's modulus of 865 GPa. Boron-carbon-nitrogen ternary compounds can have a hardness in the range of 30 to 76 GPa and a Young's modulus in the range of 200 to 700 GPa. Diamond can have a hardness between 70 and 150 GPa and a Young's modulus of 1220 GPa.

[0025] The clamping surface may comprise an array of first ridges.

[0026] The ridges can at least partially define the geometry of the clamping surface. A clamping surface comprising the first ridges can advantageously reduce the effective surface area of the clamping surface. The reduced effective surface area can reduce adhesion between the clamping surface and the substrate. The reduced effective surface area, combined with a clamping surface selected to exhibit low wear, can further reduce wear on the clamping surface.

[0027] The ridges may be elongated, for example, elongated in the plane of the clamping surface. The ridges may be substantially parallel to one another. The ridges may be regularly arranged, for example, each ridge may be approximately equidistant from each of its adjacent ridges. The ridges may comprise a wavy pattern on the surface of the clamping surface.

[0028] The clamping surface may comprise a base forming the overall global geometry of the surface and a patterned structure adjacent to the base, wherein the patterned structure is adjacent to the substrate when receiving the substrate.The ridge may comprise the patterned structure.

[0029] The ridge can have a width. The width can decrease from a maximum width near the base to a minimum width away from the base. The width can vary linearly from the maximum width to the minimum width. The width can vary nonlinearly from the maximum width to the minimum width. That is, the structure can have a curved profile. These width profiles can advantageously allow the effective surface area to vary depending on the applied pressure. For example, when the substrate is received by the clamping surface under low pressure, only the distal portion of the ridge can contact the substrate. When the substrate is received by the clamping surface under high pressure (e.g., with a heavy load or a high applied force such as static electricity), the ridge and / or substrate can deform (e.g., elastically) so that the ridge is compressed and the contact area increases. The contact area can vary from zero to a maximum value, where the maximum value indicates that the ridge and / or substrate are fully deformed.

[0030] The processing station may also include a patterning device.

[0031] The patterning device may include any device operable to apply a pattern to a substrate. The pattern may include surface texture. The pattern may include roughness. The pattern may contribute to the geometry of the substrate. The patterning device may include an ion beam. The patterning device may include a chemical processing device. The patterning device may include an etching device.

[0032] The processing station may be operated to form an array of second ridges on the substrate.

[0033] The ridges may be formed on the proximal surface of the substrate. The ridges may at least partially define the geometry of the substrate. A substrate including the second ridges may advantageously reduce the effective surface area of the substrate. The reduced effective surface area may reduce adhesion between the clamping surface and the substrate. The reduced effective surface area, combined with a clamping surface selected to exhibit low wear, may further reduce wear on the clamping surface.

[0034] The ridges may be elongated, for example elongated in the plane of the clamping surface. The ridges may be substantially parallel to one another. The ridges may be regularly arranged, for example each ridge may be approximately equidistant from each of its adjacent ridges. The ridges may comprise a wavy pattern on the surface of the clamping surface.

[0035] For a given clamping force, a substrate comprising the second ridge can advantageously reduce the effective surface area of the substrate. The reduced effective surface area can reduce adhesion between the clamping surface and the substrate. The ridges can also advantageously allow the effective area of the substrate to be controlled, for example by increasing the clamping force.

[0036] The ridges may comprise a wavy pattern on the surface of the substrate. After being adjusted, the substrate may comprise a base forming the overall global geometry of the substrate, and a patterned structure adjacent to the base, wherein the patterned structure is adjacent to the clamping surface when received by the clamping surface. The ridges may comprise the patterned structure.

[0037] The ridge can have a width. The width can decrease from a maximum width near the base to a minimum width away from the base. The width can vary linearly from the maximum width to the minimum width. The width can vary nonlinearly from the maximum width to the minimum width. That is, the structure can have a curved profile. These width profiles can advantageously allow the effective surface area to vary depending on the applied pressure. For example, when the substrate is received by the clamping surface under low pressure, only the distal portion of the ridge can contact the clamping surface. When the substrate is received by the clamping surface under high pressure (e.g., with a heavy load or a high applied force such as static electricity), the ridge can deform (e.g., elastically) so that the ridge is compressed and the contact area increases. The contact area can vary from zero to a maximum value, where the maximum value indicates that the ridge is fully deformed.

[0038] The clamping apparatus is further operable to arrange the substrate and the clamping surface in a clamping operation such that the first ridges and the second ridges cooperate to form a grid.

[0039] The clamping device can be operated to arrange the substrate and the clamping surface so that when in a clamping operation, the second ridges are aligned at a non-zero angle relative to the first ridges. The first and second ridges cooperating to form a grid can result in a discrete number of contact points between the substrate and the clamping surface. The discrete number of contact points can reduce the contact area between the substrate and the clamping surface.

[0040] The first and second ridges can be substantially perpendicular. By perpendicular, it should be understood that the first and second ridges are elongated within the same plane (i.e., the plane of the substrate), but are substantially vertically aligned within that plane. Aligning the ridges in this manner provides a substantially square grid shape. Aligning the ridges in this manner can advantageously minimize the contact area between the clamping surface and the substrate.

[0041] The processing station may also include cleaning equipment for removing particles from the substrate.

[0042] The cleaning device can be operated to clean the substrate. The cleaning device can be operated to remove particles from the substrate. That is, the processing station can be operated to apply a condition, wherein the condition includes removing particles from the substrate.

[0043] Advantageously, cleaning the substrate can reduce wear on the clamping surface and the substrate. Advantageously, cleaning the substrate can reduce deformation of the substrate during the clamping operation. Cleaning equipment can include ultrasonic jet cleaners, CO2 dry ice cleaners, or electrostatic brush cleaners. Removing large particles (e.g., 1 micron or larger) to reduce local deformation can be beneficial. Retaining smaller particles (e.g., less than 1 micron) can be beneficial. Retaining smaller particles can be beneficial, for example, for lubricity and / or hydrophobicity.

[0044] The processing station may also include a dehumidifier.

[0045] The dehumidifier can be operated to reduce the humidity of the substrate and / or the vicinity of the substrate. Reducing the humidity of the substrate can advantageously reduce wear of the clamping surface. Reducing the humidity can reduce the occurrence of oxidation reactions that occur at the interface between the clamping surface and the substrate.

[0046] The dehumidifier may include, for example, an infrared heater, an ultraviolet radiation source, an active thermal conditioning system, a plasma exposure system, or any other suitable device.

[0047] The processing station may also include equipment for applying the film to the substrate.

[0048] The film can contact the clamping surface as an intermediate layer between the substrate and the clamping surface. The film can have a lower hardness than the clamping surface and the substrate. The film can advantageously reduce wear on the clamping surface. The film can advantageously reduce wear on the substrate. The film can advantageously wear or deform under pressure. The film can be selected so as not to produce loose debris under pressure. The film can include a metal oxide. Single or multilayer films (of comparable or varying hardness) can be used.

[0049] The film can increase lubrication between the clamping surface and the substrate. The film can include molecular substances (such as alkanes and / or alcohols, silanes, hexamethyldisilazane (HDMS)) or foils. The film can include carbon, such as a thin (a few nanometers) carbon film or a carbon nanotube film.

[0050] The film can reduce or increase the roughness of the surface. For example, a smoothing film can be applied to reduce the roughness of the surface.

[0051] The film can modify the surface chemistry of the substrate. The film can terminate loose bonds on the surface. The film can include a molecular surface layer. The molecular surface layer can be applied. Terminating loose bonds on the surface can advantageously reduce adhesion between the clamping surface and the substrate. The molecular surface layer can include, for example, hydrogen or fluorine.

[0052] The membrane can reduce material transfer to the substrate surface during clamping operations or general maintenance of the device. The membrane can include a molecular surface layer. The surface layer can be adsorbed onto the surface. The surface layer can be selected to have sufficient vapor pressure to not leave the surface under vacuum, such as long-chain hydrocarbons or adhesive-based hydrocarbons. The surface layer can include, for example, water, hydrocarbons, HDMS, alcohols, or oils.

[0053] Films can increase the hydrophobicity of a substrate. For example, films can include a surface layer of molecules (e.g., alkanes, alcohols, long-chain carbon molecules, hydrophobic silanes, self-assembled monolayers (e.g., HDMS)). Hydrophobicity can also be tuned using plasma exposure. For example, by varying the type of gas used during plasma exposure (e.g., tetrafluoromethane (CF4), silicon tetrafluoride (SiF4)), the hydrophobicity of the substrate can be altered.

[0054] The processing station may also include charging equipment.

[0055] The charging device can be any device operable to apply an electric charge to the substrate. Applying an electric charge to the substrate can advantageously reduce wear on the clamping surface. Applying an electric charge can reduce the occurrence of oxidation reactions occurring at the interface between the clamping surface and the substrate. The charge can be positive, negative, or zero. The applied charge can reduce the net charge on the substrate. The charging device can include, for example, an ion gun, an electron gun, an ion generator, and / or a biased counter electrode, and / or any other suitable device.

[0056] According to a second aspect, a method for optimizing at least one interface property of a clamping operation between a substrate and a clamping surface is provided, the method comprising: adjusting a first property of the substrate based on a clamping surface parameter defining a property of the clamping surface and a substrate surface parameter defining a second property of the substrate. The property of the clamping surface may be selected to exhibit low wear.

[0057] The clamping operation is defined at least in part by at least one interface characteristic.

[0058] Previous attempts to optimize interface properties have primarily focused on controlling clamping surface parameters, for example because users have relatively freer choices regarding the substrate used in the clamping operation. Instead, it has been recognized that by applying adjustments to the substrate, interface properties can be optimized more effectively than by considering only the clamping surface.

[0059] Advantageously, by applying adjustments to the substrate based on the clamping surface parameters, the interface properties can be optimized while retaining the low-wear properties of the clamping surface. The clamping surface exhibiting properties desirable for low wear (e.g., smoothness and / or stiffness and / or hardness) often results in other interface properties being suboptimal. By providing a processing station to apply adjustments to the substrate, the low-wear clamping surface can be retained while optimizing other interface properties. The interface properties to be optimized can vary depending on the user's requirements.

[0060] Optimizing interface properties can include reducing deformation of the substrate during loading operations. Thus, optimizing interface properties can minimize stress and / or deformation of the substrate, subsequently mitigating optical issues such as overlay issues. Mitigating optical issues can be beneficial in improving the quality and yield of photolithography processes.

[0061] Optimizing interface properties can include increasing the strength of the clamping operation. For example, after a substrate has been clamped to a clamping surface, such as during a scanning operation in a lithographic apparatus, it can be accelerated. In applications with high acceleration, increasing the clamping strength can be beneficial, for example to improve positional control of the substrate during a scanning operation.

[0062] Optimizing interface properties can include increasing the efficiency of the unloading operation (ie, releasing the substrate from the clamping surface).

[0063] Optimizing the interface properties may include further reducing wear on the clamping surfaces. Thus, optimizing the interface properties may increase the lifespan of the clamping surfaces. Typically, each substrate undergoes far fewer clamping operations than the clamping surfaces (e.g., each substrate undergoes approximately 100 clamping operations, compared to approximately 10 million clamping operations per clamping surface). Increasing the lifespan of the clamping surfaces may be beneficial in reducing costs, reducing maintenance frequency, and increasing the reliability of the lithographic apparatus.

[0064] Different optimization requirements can conflict with each other. For example, high friction between the clamping surface and the substrate may be beneficial for increasing clamping strength but detrimental to reducing substrate deformation and wear on the clamping surface. Furthermore, user requirements can change, for example during different lithography processes. This specification describes an apparatus and method by which interface properties can be optimized for a range of requirements while maintaining low-wear properties on the clamping surface.

[0065] The substrate can be a reticle, mask, or wafer, such as a reticle or wafer associated with a lithographic exposure, or any other substrate within a lithographic apparatus. The adjustment can be determined based on substrate surface parameters. Determining the substrate surface parameters can include, for example, measuring properties of the substrate using metrology equipment.

[0066] The clamping surface parameters may include at least one clamping surface parameter selected from the group consisting of: hardness, stiffness, roughness, geometry, work function, chemical surface state, surface energy, surface charge, wetness, hydrophobicity, surface particle density, and lubrication.

[0067] The clamping surface parameters may be considered as a set of tribological parameters associated with the clamping surface. The clamping surface parameters may define properties of the clamping surface, for example expressed numerically.

[0068] The substrate may be defined by a corresponding set of substrate surface parameters. The substrate surface parameters may define properties of the substrate, for example, in numerical form.

[0069] The interface properties between the clamping surface and the substrate may be defined by the relationship between clamping surface parameters and corresponding substrate surface parameters.

[0070] The first property and / or the second property may be selected from the group consisting of hardness, stiffness, roughness, geometry, work function, chemical surface state, surface energy, surface charge, wettability, hydrophobicity, surface particle density, and lubricity.

[0071] The first property of the substrate may be adjusted according to at least one clamping parameter that at least partially defines the clamping operation.

[0072] The clamping parameters may be, for example, speed, force, or acceleration associated with the clamping operation. The clamping parameters may refer to a loading operation (i.e., the substrate first contacts the clamping surface and is clamped together), a scanning acceleration (i.e., the substrate is moved in response to movement of the clamping surface, such as in a scanning movement associated with a lithographic exposure), or an unloading operation (i.e., the substrate is released from the clamping surface).

[0073] Different clamping operations may have different clamping parameters, for example they may advantageously have different speeds.By applying adjustments in view of the clamping parameters, the clamping operation may be further optimized.

[0074] The conditioning may include at least one of: forming an array of ridges on the substrate; removing particles from the substrate; applying surface texture to the substrate; applying a soft film to the substrate; applying an electric charge to the substrate; and reducing humidity of the substrate.

[0075] The ridges can be elongated in the plane of the substrate. The ridges can be parallel. The ridges can form an array. A substrate including ridges can advantageously reduce the effective surface area of the substrate. The reduced effective surface area can reduce adhesion between the clamping surface and the substrate.

[0076] The ridges may comprise a wavy pattern on the surface of the substrate.After being adjusted, the substrate may comprise a base forming an overall global geometry of the substrate and a patterned structure adjacent the base, wherein the patterned structure is adjacent to the clamping surface when received by the clamping surface.

[0077] The ridge can have a width. The width can decrease from a maximum width near the base to a minimum width away from the base. The width can vary linearly from the maximum width to the minimum width. The width can vary nonlinearly from the maximum width to the minimum width. That is, the structure can have a curved profile. These width profiles can advantageously allow the effective surface area to vary depending on the applied pressure. For example, when the substrate is received by the clamping surface under low pressure, only the distal portion of the ridge can contact the clamping surface. When the substrate is received by the clamping surface under high pressure (e.g., with a heavy load or a high applied force such as static electricity), the ridge can deform (e.g., elastically) so that the ridge is compressed and the contact area increases. The contact area can vary from zero to a maximum value, where the maximum value indicates that the ridge is fully deformed.

[0078] Advantageously, the substrate can be arranged such that when received by a clamping surface having a first array of ridges, the second ridges are aligned substantially perpendicular to the first ridges. The orthogonal surface geometry of the first and second ridges can produce a discrete number of contact points between the substrate and the clamping surface. The discrete number of contact points can reduce the contact area between the substrate and the clamping surface.

[0079] Advantageously, cleaning the substrate can reduce wear on the clamping surface and the substrate. Advantageously, cleaning the substrate can reduce deformation of the substrate during the clamping operation. Cleaning equipment can include ultrasonic jet cleaners, CO2 dry ice cleaners, or electrostatic brush cleaners. Removing large particles (e.g., 1 micron or larger) to reduce local deformation can be beneficial. Retaining smaller particles (e.g., less than 1 micron) can be beneficial. Retaining smaller particles can be beneficial, for example, for lubricity or hydrophobicity.

[0080] Applying surface texture to the substrate can provide high local roughness. High local roughness can advantageously represent a higher local roughness than the roughness of the clamping surface, thereby reducing wear on the clamping surface. High local roughness can increase adhesion between the clamping surface and the substrate, thereby increasing clamping strength. The local roughness can, for example, be greater than 3 nm RMS. For example, the local roughness can be 5 nm RMS.

[0081] Roughness can be measured in terms of amplitude (deviations from the mean profile, e.g. measured as RMS) and frequency (related to the size of each deviation, e.g. measured as reverse distance). Each deviation can be considered a roughness feature. -7 m -1 An average frequency greater than about 10 -7 m -1 The average frequency of can allow similar clamping behavior across the surface. -7 m -1 The average frequency can produce higher local friction. -7 m -1 The average frequency can reduce the deformation of the substrate.

[0082] The frequencies can be uniform (i.e., each roughness feature has a similar frequency) or irregular (i.e., adjacent roughness features can have different frequencies). Uniform and irregular frequencies can have the same average frequency. Uniform frequencies can result in higher deformation and / or higher wear. Uniform frequencies can be beneficial for low-pressure loads. Irregular frequencies can result in lower deformation and / or reduced wear. A compromise between irregular and uniform frequencies may be desirable.

[0083] The film can contact the clamping surface as an intermediate layer between the substrate and the clamping surface. The film can have a lower hardness than the clamping surface and the substrate. The film can advantageously reduce wear on the clamping surface. The film can advantageously reduce wear on the substrate. The film can advantageously wear or deform under pressure. The film can be selected so as not to produce loose debris under pressure. The film can include a metal oxide. A single layer or a multilayer film (of comparable or varying hardness) can be used.

[0084] The film can increase lubrication between the clamping surface and the substrate. The film can include molecular substances (such as alkanes and / or alcohols, silanes, hexamethyldisilazane (HDMS)) or foils. The film can include carbon, such as a thin (a few nanometers) carbon film or a carbon nanotube film.

[0085] The film can modify the surface chemistry of the substrate. The film can terminate loose bonds on the surface. The film can include a molecular surface layer. The molecular surface layer can be applied. Terminating loose bonds on the surface can advantageously reduce adhesion between the clamping surface and the substrate. The molecular surface layer can include, for example, hydrogen or fluorine.

[0086] The film can reduce material transfer to the substrate surface during clamping operations or general maintenance of the device. The film can include a molecular surface layer. The surface layer can be adsorbed onto the surface. The surface layer can be selected to have sufficient vapor pressure to not leave the surface under vacuum, such as long-chain hydrocarbons or adhesive-based hydrocarbons. The surface layer can include, for example, water, hydrocarbons, HDMS, alcohols, or oils.

[0087] The film can increase the hydrophobicity of the substrate. For example, the film can include a surface layer of molecules such as alkanes, alcohols, long-chain carbon molecules, hydrophobic silanes, or self-assembled monolayers (e.g., HDMS). Hydrophobicity can also be tuned using plasma exposure. For example, by varying the type of gas used during plasma exposure (e.g., tetrafluoromethane (CF4), silicon tetrafluoride (SiF4)), the hydrophobicity of the substrate can be altered.

[0088] Applying an electric charge to the substrate can advantageously reduce wear on the clamping surface. Applying an electric charge can reduce the occurrence of oxidation reactions at the interface between the clamping surface and the substrate. The charge can be positive, negative, or zero. The applied charge can reduce the net charge on the substrate. The charge can be removed by ionization. The charge can be applied using an ion gun, an electron gun, an ion generator, and / or a biased counter electrode, and / or any other suitable method.

[0089] Reducing the humidity of the substrate can advantageously reduce wear on the clamping surface. Reducing humidity can reduce the occurrence of oxidation reactions that occur at the interface between the clamping surface and the substrate. Moisture can be removed by, for example, infrared heating, ultraviolet irradiation, active thermal conditioning (e.g., introducing the substrate to the system below the desired operating temperature and then allowing the substrate to reach the correct and uniform operating temperature), and / or plasma exposure, or any other suitable method.

[0090] The method may further include receiving a clamping surface parameter; receiving a substrate surface parameter; and determining an adjustment in view of the clamping surface parameter and the substrate surface parameter.

[0091] According to a third aspect of the present invention, there is provided a computer-readable medium comprising instructions, which, when executed by a computer, cause a substrate processing apparatus to perform any one of the above methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0093] Figure 1 schematically illustrates a lithographic system comprising a lithographic apparatus and a radiation source;

[0094] Figure 2 A mask and a mask support are schematically shown;

[0095] Figure 3 shows the process of an example clamping operation;

[0096] Figure 4 A process is shown for an example method of applying conditioning to a substrate;

[0097] Figure 5 The substrate after conditioning is schematically shown. DETAILED DESCRIPTION

[0098] In this document, the terms "radiation" and "beam" are used to cover all types of electromagnetic radiation, including ultraviolet radiation (e.g., having a wavelength of 365, 248, 193, 157 or 126 nm) and EUV (extreme ultraviolet radiation, e.g., having a wavelength in the range of about 5 to 100 nm).

[0099] The terms "reticle," "mask," or "patterning device," as used herein, should be broadly interpreted to refer to a general patterning device that can be used to impart an incident radiation beam with a patterned cross-section that corresponds to the pattern to be produced in a target portion of the substrate. The term "light valve" may also be used herein. In addition to classical masks (transmissive or reflective, binary, phase-shifting, hybrid, etc.), other examples of such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0100] Figure 1A lithographic apparatus LA is schematically shown. The lithographic apparatus LA comprises an illumination system (also called illuminator) IL configured to condition a radiation beam B (e.g., UV radiation, DUV radiation, or EUV radiation), a mask support (e.g., mask table) MT configured to support a patterning device (e.g., mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA according to certain parameters, a substrate support (e.g., wafer stage) WT configured to support a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate support according to certain parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0101] To illustrate the present invention, a Cartesian coordinate system is used. A Cartesian coordinate system has three axes: the x-axis, the y-axis, and the z-axis. Each of the three axes is orthogonal to the other two. The x-axis and the y-axis define a horizontal plane, while the z-axis is in the vertical direction. The Cartesian coordinate system does not limit the present invention and is provided for illustration only. Alternatively, another coordinate system, such as a cylindrical coordinate system, can be used to illustrate the present invention. The Cartesian coordinate system can be oriented differently, for example, so that the z-axis has a component along the horizontal plane.

[0102] In operation, the illumination system IL receives a radiation beam from a radiation source SO, for example, via a beam delivery system BD. The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for directing, shaping, and / or controlling the radiation. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross-section at the plane of the patterning device MA.

[0103] The term "projection system" PS as used herein should be broadly interpreted as including various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, as appropriate to the exposure radiation used, and / or to other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system" PS.

[0104] The lithographic apparatus LA may be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index, such as water, so as to fill the space between the projection system PS and the substrate W, which is also known as immersion lithography. More information on immersion technology is given in US6952253, which is incorporated herein by reference.

[0105] The lithographic apparatus LA may also be of a type having two or more substrate supports WT (also referred to as "dual stage"). In such a "multi-stage" machine, the substrate supports WT may be used in parallel, and / or preparatory steps for subsequent exposure of a substrate W on one of the substrate supports WT may be performed while another substrate W on another substrate support WT is being used to expose a pattern on the other substrate W.

[0106] In addition to the substrate support WT, the lithographic apparatus LA can include a measurement stage. The measurement stage is configured to hold sensors and / or cleaning equipment. The sensors can be arranged to measure properties of the projection system PS or properties of the radiation beam B. The measurement stage can accommodate multiple sensors. The cleaning equipment can be configured to clean a portion of the lithographic apparatus, such as a portion of the projection system PS or a portion of a system for providing immersion liquid. The measurement stage can be moved beneath the projection system PS when the substrate support WT is away from the projection system PS.

[0107] The lithographic apparatus LA may further comprise a processing station P operable to apply a conditioning to the substrate W or the mask MA. The conditioning may alter one or more properties of the substrate W or the mask MA, such as surface properties, such as surface charge or lubricity. The conditioning may optimize the substrate W or the mask MA prior to a lithographic process or a portion of a lithographic process.

[0108] In operation, a radiation beam B is incident on a patterning device (e.g. a mask) MA supported on a mask support MT and is patterned by a pattern (design layout) present on the patterning device MA. After passing through the mask MA, the radiation beam B passes through a projection system PS which focuses the radiation beam onto a target portion C of the substrate W. With the aid of a second positioner PW and a position measurement system IF, the substrate support WT can be accurately moved, for example in order to position different target portions C in the path of the radiation beam B in a focused and aligned position. Similarly, a first positioner PM and possibly another position sensor ( Figure 1The patterning device MA may be precisely positioned relative to the path of the radiation beam B using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2 are shown occupying dedicated target portions, they may be located in spaces between target portions. When the substrate alignment marks P1, P2 are located between target portions C, they are referred to as scribe-lane alignment marks.

[0109] The mask MA can be held on the mask support MT by clamping. The substrate W can be held on the substrate support WT by clamping. Any suitable type of clamping can be used, such as electrostatic clamping or vacuum clamping. Clamping can be actuated by a clamping device. Clamping can be referred to as a clamping operation.

[0110] The clamping operation may be at least partially defined by one or more clamping parameters. A clamping parameter may be, for example, a speed, a force or an acceleration associated with the clamping operation.

[0111] In some embodiments below, clamping may be discussed with reference to clamping a substrate W to a substrate support WT. In some embodiments below, clamping may be discussed with reference to clamping a mask MA to a mask support MT. It will be understood that the apparatus and processes described herein are also applicable to clamping any item to a portion of a lithographic apparatus or similar apparatus.

[0112] The process of clamping one item to another item can be called a clamping operation. The processing station P of the lithographic equipment LA can be used to apply adjustments to the substrate W or the mask MA (or to another item to be clamped) to achieve or improve the clamping operation. The processing station P can optionally include one or more positioning systems (for example, including a positioner that can be operated to move the substrate W or the mask MA to or towards the active area, and optionally including a position monitoring system to monitor the position of the substrate W or the mask MA). The processing station P may include one or more processing mechanisms / equipment (for example, cleaning equipment, heaters, ionizers, etc.), and optionally include one or more measurement and / or measurement systems. Example processing mechanisms / equipment are described in more detail below.

[0113] Clamping can be considered to include fixing an item in place. For example, the mask MA can be fixed in place relative to the mask support MT by clamping. That is, given Figure 1In the Cartesian coordinate system of FIG, the mask support MT can support the mask MA in the z-direction, while the clamp can fix the mask MA in the x-direction and the y-direction relative to the mask support MT. In other system configurations, the clamp can also fix the mask MA in the z-direction. It should be noted that when the mask M is clamped to the mask support MT, the mask M can be moved in the x-direction, the y-direction, and the z-direction by moving at least a portion of the mask support MT.

[0114] Figure 2 A schematic illustration of a portion of a lithographic apparatus is shown in which a mask MA is to be clamped to a mask support MT. In operation, a force (e.g., static electricity or vacuum) may bring the mask MA and the mask support MT into contact. The portion of the mask support MT that is operable to contact a portion of the mask MA during the clamping operation may be referred to as a clamping surface 20. It should be noted that although in Figure 2 In the embodiment of the present invention, the clamping surface 20 and the mask support MT are integral, but they may also be separate elements. The portion of the mask MA that is operable to contact a portion of the mask support MT may be referred to as a proximal surface 22, i.e., it is the surface of the mask MA that is close to the clamping surface 20. The proximal surface 22 may be referred to as a substrate surface.

[0115] During the clamping operation, an interaction occurs between the clamping surface 20 and the proximal surface 22. This interaction may be referred to as an interface interaction or surface interaction. The interaction may be defined, at least in part, by one or more interface characteristics. The interface characteristics may depend on the properties of the clamping surface 20 and the proximal surface 22, as described in more detail below. As described in more detail below, the interface characteristics may be optimized based on the needs of the user. A single interface characteristic may be optimized, or multiple interface characteristics may be optimized.

[0116] The clamping surface 20 may be flat, or alternatively, it may include additional structure, such as Figure 2 The protrusion 24 is shown. The protrusion 24 can be provided to reduce the contact area between the clamping surface 20 and the proximal surface 20 under certain clamping conditions (e.g., relatively weak clamping). The protrusion 24 can be any shape, such as, but not limited to, an arched, wavy, or conical shape. The protrusion 24 can also be referred to as a burl or pin.

[0117] The clamping surface 20 can be considered to have a base and a patterned portion or patterned structure. The base defines the overall overall geometry of the clamping surface 20 (which is Figure 2 The patterned portion defines smaller scale features or smaller scale geometries on the base (e.g., Figure 2 In the knob 24). Figure 2In the embodiment shown, the burls 24 are separate but connected to the base. However, it should be understood that the clamping surface 20 can be formed so that the burls 24 are integral with the base, such as by creating a molded surface or an etched surface.

[0118] There can be multiple stages in the clamping operation. Figure 3 A clamping operation 30 is shown, which includes a loading operation 32, a scanning operation 34, and an unloading operation 36. The mask MA can undergo a loading operation 32, in which it is loaded onto the clamping surface 20, for example by applying a force so that the mask MA adheres to the clamping surface 20. The mask MA can then undergo a scanning operation 34, for example by moving the mask support MT so that the mask MA moves. The scanning operation can be the same as described above with reference to FIG. Figure 1 The described lithographic exposure is combined with a lithographic scanning operation. The scanning operation may include, for example, acceleration and deceleration in the x-direction and the y-direction. The mask MA may then undergo an unloading operation 36, in which the mask MA is released from the clamping surface 20. Each of these stages may have different requirements regarding the interface properties between the clamping surface 20 and the proximal surface 22.

[0119] The interface characteristics can depend on the properties of the mask MA (i.e., the proximal surface 22) and the properties of the clamping surface 20. These properties can be referred to as surface properties or surface characteristics. These properties can be defined by surface parameters. That is, each property can be defined by a corresponding parameter. These properties can represent a set of physical properties of the surface, including but not limited to: hardness, stiffness, roughness, geometry, work function, chemical surface state, surface energy, surface charge, wetness, hydrophobicity, surface particle density, and lubricity.

[0120] The interface characteristics may also depend on the properties of the clamping operation. That is, the clamping operation may be defined, at least in part, by clamping parameters. The clamping parameters may refer to a loading operation (i.e., the substrate first contacts the clamping surface and is clamped together), a scanning acceleration (i.e., the substrate moves in response to movement of the clamping surface, such as in a scanning movement associated with a lithographic exposure), or an unloading operation (i.e., the substrate is released from the clamping surface).

[0121] The clamping surface 20 may have one or more properties defined by one or more clamping surface parameters θ. The proximal surface 22 may have one or more properties defined by one or more substrate surface parameters Φ. The interaction between the clamping surface 20 and the proximal surface 22 (i.e., the interface properties) depends at least in part on the relationship between the properties of the clamping surface (and the clamping surface parameters θ) and the properties of the substrate (and the substrate surface parameters Φ). The interface properties between the clamping surface 20 and the proximal surface 22 can be described by a set of tribological properties (e.g., wear, adhesion, and friction).

[0122] These properties of the clamping surface 20 and the proximal surface 22 can affect the interface characteristics in a variety of ways. Adjusting one or more properties to change the interface characteristics can be beneficial. The surface parameters can affect the interface characteristics in the following ways:

[0123] Hardness - If two surfaces have different hardnesses, the harder surface may cause the softer surface to wear and / or become smooth due to repeated contact between the two surfaces. This may reduce the life of the softer surface. In some cases, the softer surface may produce loose debris when in contact with the harder surface (i.e., small portions of the softer surface may be removed from the softer surface). Debris in the lithographic apparatus may reduce the image quality of the lithographic apparatus or require more regular maintenance to clean the apparatus. Hardness can be measured with reference to a hardness scale (e.g., the Vickers hardness scale).

[0124] Stiffness - If a rigid surface is involved in a clamping operation, it may break when in contact with another surface. Reducing the stiffness of the clamping surface can be beneficial. Stiffness can be measured, for example, with reference to Young's modulus.

[0125] Roughness - Roughness (or surface roughness) is a measure of the small-scale texture of a surface. Small scale can be considered to be on the order of nanometers to micrometers. A rough surface can include multiple small features on a surface that protrude from the surface. Roughness can be measured based on amplitude (i.e., the vertical deviation of the roughness features) and frequency (related to the size of each roughness feature). A large average amplitude can represent high roughness. High roughness can result in higher friction between two surfaces. High roughness can result in higher wear of the rough surface. Roughness can also affect the contact area between the two surfaces, i.e., the area where the first surface contacts the second surface. A reduced contact area can result in increased wear and / or reduced friction. It should be noted that the contact area can depend on the applied load (e.g., force) that pushes the two surfaces together. The contact area can depend on the deformation of one or both surfaces (see stiffness above).

[0126] Geometry - Geometry (or surface geometry) can be considered a macro-scale property compared to roughness. Geometry measures the larger scale structure of the surface, i.e., on the order of microns and larger. The clamping surface can have small-scale geometry (e.g., surface features), as well as larger-scale geometry (e.g., knobs 24) and the overall shape of the mask MA. The geometry can affect the contact area between the two surfaces, i.e., the area where the first surface contacts the second surface. A reduced contact area can lead to increased wear and / or reduced friction. It should be noted that the contact area can depend on the applied load (e.g., force) that pushes the two surfaces together. The contact area can depend on the deformation of one or both surfaces (see stiffness above).

[0127] Work Function - If two surfaces have different work functions, there may be charge transfer between the two surfaces. To minimize or avoid charging, it can be beneficial to reduce the difference in work function between the two surfaces. Surface charge can affect surface wear. For example, surface charge can inhibit or promote redox reactions. Reactions such as these can degrade the clamping surface and increase wear on the clamping surface.

[0128] Chemical surface state or surface energy - The chemical surface state can depend on the surface energy of a surface (or, respectively, the interfacial energy between two surfaces). The surface energy can depend on chemical interactions, such as free atomic bonds on a surface (i.e., unsatisfied valences on atoms, also known as dangling bonds or unterminated bonds). The surface energy can affect the adhesion between two surfaces. The chemical composition of a surface can also affect the surface energy of the surface.

[0129] Surface charge - Surface charge can affect the wear of a surface. For example, surface charge can inhibit or promote redox reactions. Reactions such as these can degrade the surface.

[0130] Humidity - Humidity can affect the wear of a surface. For example, humidity can promote redox reactions. Reactions such as these can degrade the surface.

[0131] Hydrophobicity - Hydrophobicity can reduce the surface energy of a surface (or correspondingly, the interfacial energy between two surfaces). Surface energy can affect the adhesion between two surfaces.

[0132] Surface Particle Density - Large particles on a surface can cause the surface to deform when interacting with another surface. Deformation can result in optical aberrations, which can reduce imaging quality and / or throughput. Deformation can also reduce overlay control. However, surface particles can also reduce adhesion between two surfaces by reducing the effective contact area. Reducing adhesion between two surfaces can be beneficial in reducing friction. Surface particles can be considered contamination.

[0133] Lubrication - Lubrication reduces friction between two surfaces.

[0134] Further references Figure 3During the loading operation 32, it may be beneficial to have low friction between the surfaces 20, 22. Low friction during the loading operation can minimize deformation of the mask MA. However, during the scanning operation 34, it may be beneficial to have high friction between the surfaces 20, 22. During the scanning operation 34, the mask MA is accelerated and subjected to forces due to its changing velocity. To provide greater positional control over the mask MA while it is accelerated, it may be beneficial to increase the strength of the interaction between the surfaces 20, 22, for example by having high friction between the surfaces 20, 22.

[0135] The desired interface properties defining the interaction between the surfaces 20, 22 may be different at different stages of the clamping operation 30, leading to potentially conflicting requirements in the selection of the clamping surface parameters θ and the substrate surface parameters Φ.

[0136] Furthermore, reducing wear on the clamping surface can be beneficial. The user can select any one of multiple substrates or masks to use in the clamping operation. For example, the user can use substrates / masks with different substrate surface parameters Φ. The user can use substrates / masks from a variety of different suppliers, where the supplier may not be the manufacturer of the lithographic equipment. Therefore, previous attempts to optimize the interaction have focused on controlling the properties of the clamping surface, in particular, selecting clamping surface parameters that are applicable to a wide range of substrates / masks.

[0137] However, it is expected that the clamping surface 20 may be used for a large number of clamping cycles during its lifetime (perhaps on the order of 10 million or more). The exemplary arrangements described herein provide for an increased lifetime of the clamping surface, thereby reducing costs, reducing maintenance frequency, and increasing the reliability of the lithographic apparatus. In some exemplary arrangements described herein, the properties of the substrate are controlled or adjusted in view of a predetermined clamping surface parameter θ, which may be selected, for example, to improve wear. In this way, the interface properties may be optimized more effectively than considering only the clamping surface parameters. In particular, by applying adjustments to the substrate based on the clamping surface parameter θ and the substrate surface parameters, the interaction may be optimized. Optimizing the interaction may include optimizing one or more interface properties. A processing station (see Figure 1 ) to make adjustments.

[0138] As previously mentioned, conflicting requirements can lead to significant design compromises. For example, previous attempts to optimize the interaction between the clamping surface 20 and the proximal surface 22 have focused on prioritizing friction requirements, which can lead to increased wear. Specifically, this can lead to increased wear of the clamping surface 20.

[0139] In the exemplary arrangements discussed herein, the clamping surface 20 is optimized for low wear (ie, so it exhibits low wear). Low wear may include reduced damage, degradation, erosion, and / or destruction during a clamping operation or throughout repeated clamping operations.

[0140] By optimizing the clamping surface 20 for low wear, the interaction between the clamping surface 20 and the proximal surface 22 may be suboptimal for a given clamping operation (in some cases, a clamping operation may be impossible). In the exemplary arrangement described herein, the proximal surface 22 is adjusted to optimize the interaction characteristics between the clamping surface 20 and the proximal surface 22 for a given clamping operation, given the properties of the clamping surface 20. In this case, the optimization of the interaction characteristics can be used to indicate an improvement in the effectiveness of a given clamping operation.

[0141] Advantageously, the clamping surface 20 can be manufactured or processed to exhibit low wear and thus increase its life. The clamping surface 20 with low wear can be manufactured or processed to have properties corresponding to low wear. The properties corresponding to low wear can be defined by a clamping surface parameter θ corresponding to low wear. For example, the clamping surface 20 can be substantially hard (e.g., having a hardness of >20 GPa or >40 GPa), substantially rigid (e.g., having a Young's modulus of >200 GPa or >250 GPa), substantially smooth (e.g., having a roughness amplitude of <3 nm RMS), and having a relatively low surface energy (<25 mJ / m2). The clamping surface 20 can be selected to have a relatively low surface energy compared to a typical body (e.g., a substrate W) that can be clamped to the clamping surface 20.

[0142] A hardness greater than 20 GPa can reduce wear on the clamping surface. Alternatively, the hardness can be greater than 40 GPa. The hardness can be measured, for example, using the Vickers hardness scale. Advantageously, a Young's modulus greater than 200 GPa can reduce wear on the clamping surface. Alternatively, the Young's modulus can be greater than 250 GPa. For example, boron nitride can have a hardness of 48 GPa and a Young's modulus of 865 GPa. Boron-carbon-nitrogen ternary compounds can have a hardness in the range of 30 to 76 GPa and a Young's modulus in the range of 200 to 700 GPa. Diamond can have a hardness in the range of 70 to 150 GPa and a Young's modulus of 1220 GPa. This list of materials should not be considered limiting, and any suitable material can be used.

[0143] The clamping surface 20 may optionally have properties that provide significantly lower wear than the properties of the proximal surface 22. That is, the clamping surface parameter θ defines a surface that exhibits significantly lower wear relative to the substrate surface parameter Φ. For example, a typical substrate W may have a hardness of approximately 10 GPa, a Young's modulus of approximately 140 GPa, and a surface roughness greater than 5 nm RMS. A typical substrate W may have a strength of up to approximately 100 mJ / m 2 surface energy.

[0144] Advantageously, by providing a processing station P and / or by applying conditioning to the substrate W or mask MA, a low-wear clamping surface 20 may be used while still allowing optimization of interface properties for other elements of the clamping operation (eg friction and adhesion).

[0145] Figure 4 An example method 40 is shown for determining an adjustment amount A and applying it to a substrate W. The method 40 and the adjustment A may additionally or alternatively be applied to a mask MA or the like. The method 40 includes determining 41 at least one substrate surface parameter Φ of the substrate W; receiving 42 the substrate surface parameter Φ; receiving 44 at least one clamping surface parameter θ; determining 46 the adjustment A based on the substrate surface parameter Φ and the clamping surface parameter θ; and processing 48 the substrate W to adjust the substrate surface parameter Φ.

[0146] Determining 41 at least one substrate surface parameter Φ of the substrate W may include, for example, measuring one or more substrate surface parameters Φ using a processing device. The processing device may be a metrology device. The processing device may form part of a processing station. In one example, an atomic force microscope may be used to determine the roughness of the substrate W. In another example, a Vickers hardness test may be used to determine the hardness of the substrate W.

[0147] Receiving 42 at least one substrate surface parameter Φ and receiving 44 at least one clamping surface parameter θ may include receiving one or more parameters via a portion of a processing device (e.g., a computer). For example, the clamping surface parameter θ may be measured similarly to that described above for determining 41 the substrate surface parameter Φ. Alternatively, these clamping surface parameters θ may be specified, for example, by a manufacturer or user, and subsequently provided to the processing device.

[0148] The processing device then determines 46 an adjustment A. The adjustment A depends on at least one property of the clamping surface and at least one property of the substrate. The adjustment is determined based on the received clamping surface parameter θ and the substrate surface parameter Φ. The adjustment A may typically include a change to the substrate so as to change the initial substrate surface parameter Φ to i Change to the adjusted substrate surface parameter Φ f Assuming the initial substrate surface parameters Φ iThe relationship between the clamping surface parameter θ and the adjusted substrate surface parameter Φ f and the clamping surface parameter θ, then the interface properties between the clamping surface 20 and the proximal surface 22 will be changed by the adjustment A. It will be appreciated that the adjustment A may take any of many possible forms, and a number of example adjustments A will be described in greater detail below.

[0149] The adjustment A can be determined using a processing station that can include a computer, for example. The adjustment A can be determined using a model. The model can model the surface interaction. For example, a model can be used where one or more clamping surface parameters θ are fixed and one or more substrate surface parameters Φ are varied or fitted. The model can attempt to optimize the interaction characteristics given a set of predetermined constraints.

[0150] Finally, the processing station applies 48 the adjustment A, ie, processes the substrate W given the adjustment A. Applying 48 the adjustment A may include processing (eg, physically or chemically changing) the substrate W so as to change the substrate surface parameters from the initial substrate surface parameters Φ i Change to the updated substrate surface parameter Φ f The processing station may include multiple elements operable to apply multiple adjustments. The processing station may include one or more of the following: patterning equipment, cleaning equipment, dehumidifiers, equipment for applying a film, charging equipment, or any other equipment capable of applying adjustments to the substrate W. Some example processing techniques are described in more detail below.

[0151] It should be noted that the steps of determining 41 substrate surface parameters, receiving 42 substrate surface parameters, receiving 44 clamping surface parameters and / or determining 46 adjustment A may be performed off-line or outside the processing station. Thus, in some arrangements, the apparatus receives pre-calculated adjustments and applies the adjustments 48 without Figure 4 Previous steps shown.

[0152] Specific adjustments A and processing techniques are described below with reference to specific substrate surface parameters Φ and clamping surface parameters θ. The following list should not be considered limiting, and other adjustments may be made without departing from the scope of the claims, which adjust one or more properties of the substrate. These processing techniques can be performed using hardware, such as with reference to Figure 1 The processing station P is described. It should be understood that different processing techniques are not mutually exclusive and that multiple different processing techniques can be performed on the same substrate W.

[0153] Hardness-Adjustment A can reduce the hardness of the substrate W. For example, the hardness of the substrate W can be reduced so that it is lower than the hardness of the clamping surface 20. Advantageously, this can reduce the wear of the clamping surface 20. An example of a processing technique that can reduce the hardness of the substrate is to apply a material layer on the surface of the substrate W (for example, on the proximal surface 22). The material layer can be called a film. The hardness of the film can be lower than the hardness of the clamping surface 20. A single layer or a multilayer film can be applied. Preferably, the film is selected so that it does not generate loose particle fragments during use. The film can be an organic material or an oxide. Such an organic material or oxide can advantageously be softer than the clamping surface and will not generate loose particle fragments.

[0154] Stiffness-adjustment A can reduce the stiffness of the substrate W. The reduced stiffness of the substrate W can advantageously reduce damage to the substrate W when in contact with the clamping surface 20 exhibiting low wear. The reduced stiffness of the substrate W can advantageously reduce the risk of fracture of the substrate W. One processing technique that can reduce the hardness of the substrate is to add alloying elements to the proximal surface 22.

[0155] Roughness-adjustment A can increase the roughness amplitude of the substrate W. The increased roughness amplitude can advantageously increase friction between the surfaces 20, 22, which can increase clamping strength and thus positional accuracy during scanning operations. Adjustment A can include increasing the roughness amplitude of the substrate W to a roughness greater than the roughness amplitude of the clamping surface 20. Increasing the roughness amplitude to a greater than the roughness of the clamping surface 20 can increase the life of the clamping surface because rougher surfaces may experience higher wear than smoother surfaces, i.e., wear directed toward the substrate W. A clamping surface 20 having a roughness amplitude less than 3 nm RMS and a proximal surface 22 having a roughness amplitude between 2 and 5 nm RMS (and greater than the roughness amplitude of the clamping surface 20) can be beneficial.

[0156] Adjusting A can increase the number of high frequency roughness features on the substrate W. The high frequency roughness features can advantageously reduce the contact area between the two surfaces 20, 22. The reduced contact area is beneficial during loading and unloading operations because the reduced contact area can reduce friction and / or adhesion between the two surfaces. It has been found that more than 10 -7 m -1 The high frequency characteristics can be beneficial.

[0157] A processing technique for adjusting the roughness may be to apply a film having a certain roughness to the substrate W.

[0158] Another processing technique to adjust the roughness may be to use lithography, such as ion beam lithography, to impart a texture to the substrate W. Alternatively, chemical processing may be used to increase the roughness of the substrate W.

[0159] The geometry-adjustment A may change the geometry of the substrate W. Changing the geometry of the substrate W may reduce the contact area between the substrate W and the clamping surface 20 .

[0160] In one example, adjustment A may apply a corrugated structure to the proximal surface 22, such as Figure 5 As shown. The structure includes a series of ridges 50 extending perpendicularly from the proximal surface 22. In this case, the ridges 50 are linear and parallel. The ridges 50 can have a depth 52 (measured perpendicular to the proximal surface) on the nanometer scale. The distance 54 between adjacent ridges 50 can be on the micrometer scale. Imposing ridges on the proximal surface 22 can form a limited number of contact areas between the proximal surface 22 and the clamping surface 20, thereby providing a limited contact area between the two surfaces 20, 22.

[0161] The clamping surface 20 can be provided with a corresponding wavy structure having a clamping surface ridge similar to the proximal surface ridge 50. The proximal surface 22 can be received so that the clamping surface ridge is oriented at a non-zero angle to the proximal surface ridge 50. In this orientation, the ridges form a grid. In this orientation, a limited number of contact points are provided between the two surfaces 20, 22, thereby providing a further limited contact area between the two surfaces. These ridges can be arranged so that the proximal surface ridge 50 is generally perpendicular to the clamping surface ridge. In this orientation, the grid forms an array of contact points in the form of a roughly square grid.

[0162] The ridges 50 can be deformable so that they compress when a load is applied. Thus, compressing the ridges 50 can increase the contact area between the two surfaces 20, 22. In this way, the extent of the contact area can be controlled during the clamping operation to control the amount of friction between the surfaces 20, 22. For example, an increase in contact area and a corresponding increase in friction can be achieved by applying a greater clamping force.

[0163] In an alternative example, the proximal surface can be oriented such that the clamping surface ridges are parallel to the proximal surface ridges 50. In this orientation, the ridges can be offset from one another. The offset ridges can provide an increased contact area between the two surfaces. The offset ridges can increase the interface strength between the two surfaces 20, 22. The offset ridges can increase the adhesion between the two surfaces 20, 22.

[0164] The orientation of the clamping surface 20 and the proximal surface 22 may be changed using a clamping device operable to actuate a clamping operation.

[0165] It will be appreciated that the spine may be another shape than that depicted, such as having a triangular or box-shaped cross-section.

[0166] An example processing technique for applying ridges 50 is by ion beam lithography. The ion beam can be directed at a non-zero and non-perpendicular angle relative to proximal surface 22 to form a wavy structure. Another example processing technique for applying ridges 50 is by applying a resist to substrate W and creating an interference pattern in the resist, thereby producing the desired structure after an etching step. Another alternative example processing technique for applying ridges 50 is to etch the structure using a laser.

[0167] Work function adjustment A can be to change the work function of proximal surface 22 so that it is closer to or comparable to the work function of clamping surface 20. This can reduce or prevent charge transfer between the two surfaces 20, 22. A processing technique that can apply this adjustment A is to oxidize or reduce the surface. Another processing technique that can apply this adjustment A is to apply a surface layer with a different work function, such as an adsorbate layer, top layer, or membrane.

[0168] Chemical surface state or surface energy adjustment A can be to reduce the surface energy of proximal surface 22. Adjustment A can be to change the surface energy of proximal surface 22 so that it is closer to or comparable to the surface energy of clamping surface 20. Similar surface energies can reduce adhesion between the two surfaces 20, 22. Alternatively, the adjustment can be to increase the difference in surface energy between the two surfaces 20, 22. Such an adjustment can increase adhesion to clamping surface 22 and, therefore, increase clamping strength.

[0169] The treatment technique for applying this adjustment A is to apply a surface layer of molecules. For example, applying fluorine to both surfaces 20, 22 or applying hydrogen to both surfaces 20, 22 can reduce the adhesion between the two surfaces 20, 22. Alternatively, applying fluorine to one surface (e.g., the clamping surface 20) and applying hydrogen to the other surface (e.g., the proximal surface 22) can increase the adhesion between the two surfaces 20, 22.

[0170] Surface charge-adjustment A can be the removal of at least some charge from the proximal surface 22. Removing charge can advantageously reduce wear of the clamping surface 20. Exemplary processing techniques that can be used to apply this adjustment A are the use of an ionizer, an ion gun, an electron gun, or an ionizer in combination with a biased counter electrode.

[0171] Humidity adjustment A can be the reduction or removal of moisture from the proximal surface 22. Example processing techniques that can be used to apply this adjustment A include the use of infrared heating, ultraviolet radiation, or plasma exposure. Combinations of processing techniques can be used. These processing techniques can be combined with active thermal conditioning of the substrate W, whereby the substrate W is introduced into the lithographic apparatus at a temperature below the desired operating temperature and then reaches the correct and uniform operating temperature. The processing station can include a dehumidifier.

[0172] Hydrophobicity-Adjustment A can be increasing the hydrophobicity of the proximal surface 22. Exemplary processing techniques that can be used to apply this Adjustment A are using plasma exposure (e.g., tetrafluoromethane (CF4), silicon tetrafluoride (SiF4)), exposure to alkanes and / or alcohols (optionally with long carbon chain molecules, which can be beneficial because long carbon chain molecules are stable in a vacuum), exposure to hydrophobic silanes, or adding a self-assembled monolayer (e.g., hexamethyldisilazane (HMDS)).

[0173] Surface particle density - Adjustment A can be to reduce the number of large particles (e.g., >1 micron) on the proximal surface 22. Removing large particles is beneficial for reducing deformation of the substrate W when in contact with the clamping surface 20. Exemplary processing techniques for applying this adjustment are ultrasonic jet cleaning, carbon dioxide dry ice cleaning, non-contact electrostatic removal, or electrostatic brushing. Removing at least some large particles can be beneficial, but not removing smaller particles (e.g., because smaller particles can form a lubricating layer and / or form a barrier to inhibit strong bonds formed between the two surfaces 20, 22, which can thereby increase adhesion and / or wear). The processing technique can be optimized to preferentially remove large particles and retain small particles on the proximal surface 22. A method that can be used to preferentially remove large particles and retain small particles is to use carbon dioxide dry ice cleaning and select dry ice pellets of appropriate size.

[0174] Lubrication-Adjustment A can increase lubrication between the proximal surface 22 and the clamping surface 20. This can subsequently reduce friction between the surfaces 20, 22. A treatment technique for applying this adjustment A can be to apply a layer of material to the proximal surface 22. For example, such a thin film can be applied. Multiple layers or a single layer can be applied. The layer can contain, for example, alkanes and / or alcohols (optionally with long carbon chain molecules, which can be advantageous because long carbon chain molecules are stable in a vacuum), hydrophobic silanes, a single layer (e.g., hexamethyldisilazane (HDMS)), a carbon film, or a carbon nanotube film.

[0175] The adjustment A may also be determined as a function of at least one clamping parameter and at least one substrate surface parameter and at least one clamping surface parameter. For example, the adjustment A may be determined as a function of the applied clamping force or the scanning speed.

[0176] Although specific reference may be made herein to the use of lithographic apparatus in IC manufacturing, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include 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, and the like.

[0177] Although specific reference may be made herein to embodiments of the present invention in the context of lithographic equipment, embodiments of the present invention may be used in other equipment. Embodiments of the present invention may form part of mask inspection equipment, metrology equipment, or any equipment that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These equipment are generally referred to as lithographic tools. Such lithographic tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0178] Although specific reference has been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention is not limited to optical lithography and may be used in other applications, such as imprint lithography, where the context permits.

[0179] Where the context permits, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), etc. In addition, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only, and that such actions are actually generated by a computing device, processor, controller, or other device that executes the firmware, software, routines, etc., and in doing so, may cause an actuator or other device to interact with the physical world.

[0180] While specific embodiments of the present invention have been described above, it will be appreciated that the present invention may be practiced otherwise than as described. The foregoing description is intended to be illustrative and not limiting. Therefore, it will be apparent to those skilled in the art that modifications may be made to the described invention without departing from the scope of the claims set forth below.

Claims

1. A lithographic apparatus comprising: a clamping surface for supporting a substrate, wherein properties of the clamping surface are defined by at least one clamping surface parameter, and wherein the properties of the clamping surface have been selected to exhibit low wear; a clamping device for actuating a clamping operation between the clamping surface and the substrate, wherein the clamping operation is at least partially defined by at least one interface characteristic between the clamping surface and the substrate; as well as a processing station operable to apply an adjustment to a first property of the substrate to optimize at least one interface characteristic for a particular clamping operation, the adjustment being a function of the clamping surface parameter and at least one substrate surface parameter defining a second property of the substrate, The adjustments include one or more of the following: applying pattern features to the substrate; applying a surface texture to the substrate; removing particles from the substrate; applying an electric charge to the substrate; as well as The humidity of the substrate is reduced. 2 . The lithographic apparatus of claim 1 , further comprising a processing device arranged to determine a surface parameter of the substrate defining the second property of the substrate.

3. A lithographic apparatus according to claim 1 or 2, wherein the first property and / or the second property is selected from the group consisting of: hardness, stiffness, roughness, geometry, work function, chemical surface state, surface energy, surface charge, wetness, hydrophobicity, surface particle density and lubricity.

4. The lithographic apparatus of claim 1 or 2, wherein the adjusting is further based on at least one clamping parameter that at least partially defines the clamping operation.

5. The lithographic apparatus according to claim 1 , wherein the properties of the clamping surface include at least one of the following: a hardness greater than 20 GPa, a stiffness greater than 200 GPa, a surface roughness less than 3 nm RMS, a strength less than 25 mJ / m 2 surface energy.

6. The lithographic apparatus of claim 1 or 2, wherein the clamping surface comprises an array of first ridges.

7. The lithographic apparatus of claim 1 or 2, wherein the processing station further comprises a patterning apparatus.

8. The lithographic apparatus of claim 7, wherein the adjusting comprises applying the pattern feature to the substrate, and the processing station is configured to apply the pattern feature by forming an array of second ridges on the substrate.

9. The lithographic apparatus of claim 1 or 2, wherein the processing station further comprises a cleaning apparatus for removing particles from the substrate to thereby apply a conditioning to remove particles from the substrate.

10. The lithographic apparatus of claim 1 or 2, wherein the processing station further comprises a dehumidifier to thereby apply a regulation that reduces the humidity of the substrate.

11. The lithographic apparatus of claim 1 or 2, wherein the processing station further comprises an apparatus for applying a film to the substrate.

12. The lithographic apparatus of claim 1 or 2, wherein the processing station further comprises a charging device to thereby apply adjustment of the charge applied to the substrate.

13. A lithographic apparatus comprising: a clamping surface for supporting a substrate, the clamping surface comprising an array of first ridges, wherein properties of the clamping surface are defined by at least one clamping surface parameter, and wherein the properties of the clamping surface have been selected to exhibit low wear; a clamping device for actuating a clamping operation between the clamping surface and the substrate, wherein the clamping operation is at least partially defined by at least one interface characteristic between the clamping surface and the substrate; as well as a processing station comprising a patterning device operable to apply an adjustment to a first property of the substrate to optimize at least one interface characteristic for a particular clamping operation based on the clamping surface parameter and at least one substrate surface parameter defining a second property of the substrate, the patterning device being configured to form an array of second ridges on the substrate, Wherein the clamping apparatus is further operable to arrange the substrate and the clamping surface in a clamping operation such that the first ridges and the second ridges cooperate to form a grid. The lithographic apparatus of claim 13 , wherein the first ridge and the second ridge are substantially perpendicular.

15. A method for optimizing at least one interface characteristic of a clamping operation between a substrate and a clamping surface, wherein properties of the clamping surface have been selected to exhibit low wear, the method comprising: receiving clamping surface parameters defining said properties of said clamping surface; receiving a substrate surface parameter defining a second property of the substrate; determining an adjustment to a first property of the substrate based on the clamping surface parameter and the substrate surface parameter; as well as adjusting the first property of the substrate according to the determined adjustment, The adjustment includes at least one of the following: forming a ridge array on the substrate; removing particles from the substrate; applying a surface texture to the substrate; applying an electric charge to the substrate; as well as The humidity of the substrate is reduced.

16. The method of claim 15, wherein the clamping surface parameters comprise at least one clamping surface parameter selected from the group consisting of: hardness, stiffness, roughness, geometry, work function, chemical surface state, surface energy, surface charge, wetness, hydrophobicity, surface particle density, and lubrication.

17. The method of claim 15 or 16, wherein the first property and / or the second property is selected from the group consisting of: hardness, stiffness, roughness, geometry, work function, chemical surface state, surface energy, surface charge, wetness, hydrophobicity, surface particle density and lubricity.

18. The method of claim 15 or 16, wherein the first property of the substrate is adjusted in dependence on at least one clamping parameter which at least partially defines the clamping operation.

19. A computer-readable medium comprising instructions which, when executed by a computer, cause a substrate processing apparatus to perform the method according to any one of claims 15 to 18.

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