Object holder, stage, optical element and method of controlling surface flatness, and their use in lithographic methods or devices

Abstract

There is provided an object holder configured to support an object, the object holder comprising a support surface having a plurality of support elements, the support elements comprising a metal-Si multilayer, a metal-Ge multilayer, and / or a chromium nitride layer, the metal-Si multilayer, the metal-Ge multilayer, and / or the chromium nitride layer are thermally treated to provide a selectively alterable height of the respective support elements, via a thermal treatment of the metal-Si multilayer, the metal-Ge multilayer, and / or the chromium nitride layer. Also provided are a stage comprising such an object holder, an apparatus for controlling the flatness of a surface comprising such an object holder, an optical element for a lithographic apparatus, an apparatus for controlling the flatness of a surface, a lithographic apparatus or tool comprising such an object holder, and a method of manufacturing the same. A method of controlling the shape of a surface, a method of manufacturing an object holder, a method of correcting the flatness of an object holder or an optical element, and the use of such an apparatus or method in a lithographic apparatus or process.

Description

Cross-reference to related applications

[0001] This application claims priority to EP application 23183500.0, filed on July 5, 2023, which is incorporated herein by reference in its entirety. Technical Field

[0002] This disclosure relates to object holders, stages, optical elements, and lithography apparatuses or tools that include such object holders, optical elements, or stages. This disclosure also relates to methods for controlling surface flatness. The use of such object holders, stages, lithography apparatuses, or methods in lithography methods or apparatuses is also described. The object holder may be part of the stage of a lithography apparatus or tool. This disclosure is particularly, but not exclusively, applicable to EUV and DUV lithography apparatuses and methods. Background Technology

[0003] A photolithography apparatus is a machine configured to apply a desired pattern onto a substrate. Photolithography apparatuses can be used, for example, in the manufacture of integrated circuits (ICs). A photolithography apparatus can project a pattern from a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) disposed on a substrate.

[0004] To project patterns onto a substrate, a photolithography apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature that can be formed on the substrate. Compared to a photolithography apparatus using radiation with a wavelength of, for example, 193 nm, a photolithography apparatus using extreme ultraviolet (EUV) radiation with wavelengths in the range of 4 to 20 nm (e.g., 6.7 nm or 13.5 nm) can be used to form smaller features on the substrate.

[0005] The substrate to be exposed can be supported by a substrate holder (i.e., the object directly supporting the substrate), which in turn is supported by a substrate stage. The substrate holder may have an array of protrusions or support elements called nodes projecting from at least one side. When the substrate rests on the top of a node on at least one side of the substrate holder, the substrate can be spaced apart from the body of the substrate holder. This helps prevent particles (i.e., contaminant particles, such as dust particles) that may be present on the substrate holder from deforming the substrate holder or the substrate. The total surface area of ​​the nodes may be only a small fraction of the total area of ​​the substrate or the substrate holder. Thus, it is more likely that any particles will be located between the nodes and their presence will have no effect. The top of the node defines a plane on which the object lies when engaged.

[0006] Because of the high accelerations that substrates may experience when using high-throughput lithography equipment, it may be insufficient to allow the substrate to simply rest on the protrusions of the substrate holder. It must be clamped in place. Two methods can be used to clamp the substrate in place—vacuum clamping and electrostatic clamping. In vacuum clamping, the space between the substrate holder and the substrate, and optionally between the substrate stage and the substrate holder, is partially extracted, so that the substrate is held in place by a higher-pressure gas or liquid above it. However, when the environment near the beam path and / or the substrate or substrate holder is maintained at low or very low pressure, such as for extreme ultraviolet (EUV) lithography, vacuum clamping may not be used. In this case, a sufficiently large pressure difference may not be generated across the substrate (or substrate holder) to clamp it. Therefore, electrostatic clamping can be used. In electrostatic clamping, a potential difference is established between the substrate and the substrate stage and / or substrate holder. This potential difference generates a clamping force.

[0007] It is important to control the flatness of the substrate, which can be, for example, a wafer. While a substrate can have within-specification flatness when it is not in situ within the lithography apparatus, its flatness can change when it is held in place within the apparatus due to forces acting upon it, such as those from electrostatic or vacuum clamping. In this way, the so-called functional flatness of the substrate (i.e., flatness in its intended position) needs to be controlled because, while a free substrate may be within specifications, an in-situ substrate may not. Similarly, it is desirable to provide optical elements (such as mirrors) with optimal surface shapes to achieve best results and accuracy.

[0008] During use, the surface is subjected to wear, tearing, and contamination, and its smoothness may be negatively affected. Uneven wear and tear can limit performance and component lifespan. Replacement of worn components also results in significant downtime for associated equipment, thereby reducing productivity.

[0009] This disclosure has been designed to attempt to solve at least some of the problems identified above. Summary of the Invention

[0010] According to a first aspect of the invention, an object holder configured to support an object is provided, the object holder including a support surface having a plurality of support elements, wherein the plurality of support elements include a metal-Si multilayer, a metal-Ge multilayer, and / or a chromium nitride layer, the metal-Si multilayer, the metal-Ge multilayer, and / or the chromium nitride layer being configured to provide selectively variable heights of the respective support elements via heat treatment of the metal-Si multilayer, the metal-Ge multilayer, and / or the chromium nitride layer. The metal may be selected from titanium, molybdenum, or any combination thereof.

[0011] The flatness of object holders, such as wafer stages and wafer jigs, is adjusted using one of two methods. First, ion beam regrinding (IBF) adjusts flatness by etching the surface of the object holder with ion bombardment in an offline setting. This offline setting is understood to be outside of the photolithography apparatus used for imaging wafers. The height of individual protrusions can be corrected, and the ability to do so is determined by the spot size of the ion beam. IBF cannot be performed inside a photolithography scanner because it requires an ion source, and the removal of material would cause contaminant material to diffuse within the scanner, leading to contamination problems. During operation, flatness can drift due to various reasons, including wear, indentation, and contamination. Flatness makes a strong contribution to on-product overlay (OPO), and the need to replace jigs (which involve long downtimes) is driven by flatness degradation. Similarly, for optical components, such as mirrors or mirror blocks, flatness correction is performed using IBF after the application of a mirror coating, and surface flatness can no longer be corrected. Laser ablation can be used to remove material from a target, but it has a minimum height removal of about 40 to 60 nm per pulse, which limits its applicability because the height difference of the support elements of the die, which causes focusing problems and wear, is less than this value. Thus, laser ablation will remove too much material and may also generate unwanted contaminants.

[0012] This disclosure addresses the shortcomings of the prior art by providing a material that can be heated to change the height of individual support elements. While it will be appreciated that the material contracts and expands with temperature changes, this does not allow for stable changes in the height of support elements (such as protrusions), whereas using a material undergoing a phase transition allows such changes in height to be stable. By stabilizing, it can be understood that the phase does not change at the operating temperature experienced in nominal use and on the time scale of the object holder in nominal use. In this way, this disclosure allows for adjustment of individual support elements, such as protrusions. Since the height of the protrusions can be adjusted without removing the material, the adjustment can be achieved within the scanner. This is more advantageous because the functional flatness of the substrate may differ between scanners and it is not possible to correct it externally to the scanner. This disclosure allows the support surface to be made flat or uneven to correct for differences between individual scanners and ultimately to provide functional flatness for correcting overlay and / or focusing errors in other parts of the system, such as correcting non-ideal focusing planes and focusing a particular wafer. When Ti-Si multilayers are heated, the formation of TiSi and / or TiSi2 leads to dimensional changes. A similar effect is seen with metal-germanium multilayers. Similarly, it has been found that chromium nitride layers can be densified by selective heating, thereby reducing their volume. This volume reduction can be used to adjust the height of support elements. The chemical formula of the Ti-Si multilayer can be TiSi. xWhere 0.3 ≤ x ≤ 2. Ti-Si multilayers can include any number of alternating layers of Ti and Si. Similarly, for Mo-Si multilayers, this can include any number of alternating layers of Mo and Si. Similarly, for metal-Ge multilayers, any number of alternating layers of Ge and metal can be used. The chemical formula of a metal-Ge multilayer can be MGe. x Where 0.3 ≤ x ≤ 2. It will be understood that the multilayer can comprise different metals, which may be in the same layer and / or in different layers. The thickness of each individual layer in the multilayer can be from about 2 nm to about 100 nm, and preferably from about 10 nm to about 20 nm. The layers can be provided by sputtering (optionally geomagnetic sputtering). It will be understood that not all support elements must comprise multilayers. Preferably, support elements that undergo most of the wear during operation are provided with multilayers.

[0013] For example, a protrusion with an increased height of 12 nm or more, potentially caused by indentation or contamination, can lead to focusing problems and die loss. At the edges of the support surface, the support element undergoes wear, potentially by approximately 20 to 50 nm during use, which limits performance. Both of these effects limit the lifespan of the support surface and can lead to premature replacement and associated downtime. By being able to adjust the height of the support element, the desired shape of the support surface can be tailored, thereby extending its lifespan.

[0014] Multiple support elements may be protrusions. It will be understood that not all support elements or protrusions need to include metal-Si multilayers, metal-Ge multilayers, and / or chromium nitride layers. In embodiments, all support elements include metal-Si multilayers, metal-Ge multilayers, and / or chromium nitride layers. In other embodiments, only some of the support elements include metal-Si multilayers, metal-Ge multilayers, and / or chromium nitride layers. Preferably, in embodiments where only some of the support elements include metal-Si multilayers, metal-Ge multilayers, and / or chromium nitride layers, the metal-Si multilayers, metal-Ge multilayers, and / or chromium nitride layers are provided to the support elements subjected to the greatest wear and tear.

[0015] Object holders can be substrate holders. Object holders can be wafer holders such as wafer stages or wafer clamps such as electrostatic wafer chucks. Object holders can also be mask holders, such as mask clamps or mask stages. In fact, substrate holders can be any holder requiring micron or nanometer accuracy in flatness.

[0016] Multiple support elements may include a top coating. It will be appreciated that the material including the top coating may be, but preferably is different from metal-Si multilayers and / or metal-Ge multilayers and / or chromium nitride layers, such as Ti-Si multilayers, Mo-Si multilayers, Ti-Ge multilayers, Mo-Ge multilayers, chromium nitride layers, or any combination thereof. The top coating material can be any known top layer material. The top coating material may be selected from chromium nitride, diamond-like carbon, or combinations thereof. It will be appreciated that, in the case where the top coating includes chromium nitride, portions of the top coating may be heat-treated to densify the material and thereby adjust the surface shape of the top surface.

[0017] The thickness of the metal-Si multilayer, metal-Ge multilayer, and / or chromium nitride layer can be up to approximately 1400 nm, approximately 1300 nm, approximately 1200 nm, approximately 1100 nm, approximately 1000 nm, approximately 900 nm, approximately 800 nm, approximately 700 nm, approximately 600 nm, approximately 500 nm, approximately 400 nm, approximately 300 nm, approximately 200 nm, or approximately 100 nm. The thickness of the metal-Si multilayer, metal-Ge multilayer, or chromium nitride layer can be selected to provide a highly tunable range of the desired range required for a given application.

[0018] According to a second aspect of this disclosure, a stage is provided that includes an object holder according to the first aspect.

[0019] According to a third aspect of this disclosure, an optical element for a photolithography apparatus is provided, comprising a metal-Si multilayer, a metal-Ge multilayer, or a chromium nitride layer, wherein the metal-Si multilayer, metal-Ge multilayer, or chromium nitride layer is configured to selectively change shape via heat treatment of the metal-Si multilayer, metal-Ge multilayer, and / or chromium nitride layer. Similar to the first aspect, the metal of the metal-Si multilayer and / or metal-Ge multilayer can be selected from titanium, molybdenum, or any combination thereof. The optical element can be a mirror block, which typically has a mirror surface on its side for the purposes of an interferometric stage positioning system.

[0020] Previously, it was impossible to correct deformations in the mirror surface after IBF correction and the application of the mirror layer. Such deformations could occur in the mirror layer itself or originate from the assembly process. This disclosure allows for the correction of deformations by selectively heating metal-Si multilayers, metal-Ge multilayers, and / or chromium nitride layers, even after the mirror surface has been provided.

[0021] According to a fourth aspect of this disclosure, an apparatus for controlling the flatness of a surface is provided, the apparatus comprising an object holder or optical element according to this disclosure, and components for changing the phase configuration of a metal-Si multilayer, a metal-Ge multilayer, and / or a chromium nitride layer.

[0022] It will be understood that controlling flatness does not necessarily mean making the surface as flat as possible, because it may be necessary to provide uneven surfaces to correct for errors in other parts of the system to which the device is applied, so that when the substrate is bonded to the surface, the substrate is deformed into the desired shape.

[0023] The component used to change the phase configuration can be any kind of heater, such as an electric heater or a laser. A laser may be preferred due to its high accuracy.

[0024] According to a fifth aspect of this disclosure, a photolithography apparatus or tool is provided, the photolithography apparatus or tool including an object holder according to a first aspect, a stage according to a second aspect, an optical element according to a third aspect, or a device according to a fourth aspect of this disclosure.

[0025] According to a sixth aspect of this disclosure, a method is provided for correcting the flatness of the surface of an object holder or optical element of a photolithography apparatus, the method comprising: providing a surface comprising at least one material capable of undergoing volume change upon heating, and controlling the flatness of the surface by heat treatment of the at least one material capable of undergoing volume change upon heating, optionally wherein the at least one material capable of undergoing volume change upon heating is a multilayer, optionally a chromium nitride multilayer or a metal-Si multilayer or a metal-Ge multilayer, optionally wherein the metal is selected from titanium, molybdenum, or any combination thereof.

[0026] As described above, the shape of a surface can be corrected by providing it with a phase change material (i.e., metal-Si multilayers and / or chromium nitride layers and / or metal-Ge multilayers) that allows control over the height of the surface region. Previously, this was not possible to do in situ.

[0027] Surface flatness can be corrected by selectively heating the material to a predetermined temperature and annealing it, optionally by laser heating.

[0028] Controlling the flatness of the surface preferably occurs within the photolithography apparatus.

[0029] Previously, it was impossible to adjust the surface shape within a photolithography apparatus due to the risk of particulate contamination. This disclosure overcomes this drawback by allowing in-situ adjustment of the surface shape by selectively heating metal-Si multilayers, metal-Ge multilayers, and / or chromium nitride layers.

[0030] According to the seventh aspect of this disclosure, there are uses in a photolithography method or apparatus according to the first aspect, the stage according to the second aspect, the optical element according to the third aspect, the device according to the fourth aspect, the photolithography apparatus or tool according to the fifth aspect, or the method according to the sixth aspect of this disclosure.

[0031] As will be apparent to those skilled in the art, the various aspects and features of the invention set forth above or below can be combined with various other aspects and features of the invention. All such combinations are expressly contemplated and disclosed herein. Attached Figure Description

[0032] Embodiments of the invention will now be described by way of example only with reference to the accompanying schematic diagrams, in which:

[0033] - Figure 1 A lithography system including a lithography apparatus and a radiation source is described;

[0034] - Figure 2 It is a schematic depiction of a cross-section of the surface according to this disclosure;

[0035] - Figure 3 This is a schematic depiction of the optical element 18 according to the present disclosure;

[0036] - Figure 4 a to Figure 4 c depicts a white light interferometry (WLI) image showing the variation in the height of the chromium nitride stack and the associated data; and

[0037] - Figure 5a and Figure 5b Comparative atomic force microscopy (AFM) images depicting the chromium nitride surface outside annealed spot (5a) and inside annealed spot (5b). Detailed Implementation

[0038] Figure 1 A lithography system including a radiation source SO and a lithography apparatus LA is illustrated. 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 includes an irradiation system IL, a support structure MT configured to support a patterning apparatus MA (e.g., a mask), a projection system PS, and a stage WT. The stage WT may include an object holder WH configured to support an object W. The object W may be provided in the form of a substrate. The stage WT may be provided in the form of a substrate stage. The object holder WH may be provided in the form of a substrate fixture. The substrate may be a wafer.

[0039] The irradiation system IL is configured to adjust the EUV radiation beam B before it is incident on the patterning apparatus MA. Furthermore, the irradiation system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. Together, the faceted field mirror device 10 and the faceted pupil mirror device 11 provide the EUV radiation beam B with a desired cross-sectional shape and a desired intensity distribution. The irradiation system IL may include other mirrors or devices besides or replacing the faceted field mirror device 10 and the faceted pupil mirror device 11.

[0040] After being adjusted in this way, the EUV radiation beam B interacts with the patterning apparatus MA. As a result of this interaction, a patterned EUV radiation beam B' is generated. 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 a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate stage WT. The projection system PS can apply a reduction factor to the patterned EUV radiation beam B', thus forming an image with features smaller than the corresponding features on the patterning apparatus MA. For example, a reduction factor of 4 or 8 can be applied. Although the projection system PS in Figure 1 The diagram is shown with only two reflectors 13 and 14, but the projection system PS can include a different number of reflectors (e.g., six or eight reflectors).

[0041] The substrate W may include a previously formed pattern. In this case, the photolithography apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pattern previously formed on the substrate W.

[0042] A relative vacuum, i.e., a small amount of gas (e.g., hydrogen) at a pressure much lower than atmospheric pressure, can be provided in the radiation source SO, the irradiation system IL, and / or the projection system PS.

[0043] Figure 1The radiation source SO shown is, for example, of the type that can be referred to as a laser-generated plasma (LPP) source. A laser system LS, which may include, for example, a CO2 laser, is arranged to deposit energy into a fuel, such as tin (Sn) supplied, for example, from a fuel emitter 3, via a laser beam LB. Although tin is mentioned in the description below, any suitable fuel can be used. The fuel may be, for example, in liquid form and may be, for example, a metal or alloy. The fuel emitter 3 may include a nozzle configured to guide tin, for example, in droplet form, along a trajectory toward the plasma formation region 4. The laser beam LB is incident on the tin at the plasma formation region 4. The laser energy is deposited into the tin, generating a tin plasma 7 at the plasma formation region 4. During the de-excitation and recombination of electrons and ions in the plasma, radiation, including EUV radiation, is emitted from the plasma 7.

[0044] EUV radiation from the plasma is collected and focused by collector 5. Collector 5 includes, for example, a near-vertical incident radiation collector 5 (sometimes more generally referred to as a vertical incident radiation collector). Collector 5 may have a multi-layered mirror structure arranged to reflect EUV radiation (e.g., EUV radiation with a desired wavelength such as 13.5 nm). Collector 5 may have an elliptical configuration with two focal points. The first focal point may be located at plasma formation region 4, and the second focal point may be located at intermediate focal point 6, as discussed below.

[0045] The laser system LS can be spatially separated from the radiation source SO. In this case, the laser beam LB can be transmitted from the laser system LS to the radiation source SO by means of a beam delivery system (not shown), which includes, for example, suitable directional mirrors and / or beam expanders and / or other optical devices. The laser system LS, the radiation source SO, and the beam delivery system can be considered together as a radiation system.

[0046] The radiation reflected by collector 5 forms an EUV radiation beam B. The EUV radiation beam B is focused at intermediate focus 6 to form an image of the plasma present in plasma formation region 4 at intermediate focus 6. The image at intermediate focus 6 acts as a virtual radiation source for illuminating system IL. Radiation source SO is arranged such that intermediate focus 6 is located at or near opening 8 in the enclosed structure 9 of radiation source SO.

[0047] although Figure 1 The radiation source SO is described as a laser-generated plasma (LPP) source, but EUV radiation can be generated using any suitable source such as a discharge-generated plasma (DPP) source or a free-electron laser (FEL).

[0048] Figure 2This is a schematic depiction of a cross-section of a surface according to the present disclosure. A single protrusion 15 is depicted, although it will be appreciated that multiple protrusions may be present on the surface. The protrusion 15 comprises a metal-Si multilayer, such as a Ti-Si multilayer or a Mo-Si multilayer 16, which is covered by a covering material 17 such as chromium nitride and / or diamond-like carbon. Alternatively or additionally, a metal-Ge multilayer may be provided. It will be appreciated that the reference to the metal-Si multilayer also applies to the metal-Ge multilayer and / or chromium nitride layer. Although the covering material 17 is depicted surrounding the metal-Si multilayer 16, it will be appreciated that the covering material 17 may be disposed only on top of the metal-Si multilayer 16.

[0049] In use, the height of each protrusion 15 is controlled by selectively heating and annealing the metal-Si multilayer 16 forming at least a portion of the protrusion 15. Any suitable heating method can be used, but lasers are preferred due to their accuracy and precision. Pulsed lasers can be used. The heat source can be concentrated on a single protrusion or a group of protrusions. The degree of heating and the cooling rate can be controlled by adjusting the intensity and duration of the laser pulse. By adjusting the intensity and duration of the laser pulse, the desired surface shape can be provided by adjusting the height of the protrusion 15. The height variation of the protrusions is stable within the normal operating temperature range of the substrate holder WH, which can range from 0°C to 100°C, such that changes in phase and physical properties are caused only by the intended heat source.

[0050] Figure 3 This is a schematic depiction of an optical element 18 according to the present disclosure. The optical element includes a base layer 19 supporting a metal-Si multilayer 16. In embodiments, a chromium nitride layer and / or a metal-Ge multilayer may be present in addition to or instead of a metal-Si multilayer. The metal-Si multilayer support is configured as a mirror layer 20 to reflect incident light. The provision of the metal-Si multilayer 16, which can be adjusted by selective heating, allows the overlying mirror layer 20 to be adjusted as needed. Without the metal-Si multilayer 16, there is no way to change the shape of the mirror layer 20 within the photolithography apparatus because other techniques generate contaminants and / or other techniques are not feasible to implement within the photolithography apparatus.

[0051] Figure 4 a to Figure 4c depicts white light interferometry (WLI) images illustrating variations in the height of a chromium nitride stack. Each image shows how the surface of a chromium nitride stack, from top to bottom, comprising a standard density chromium nitride layer, a porous chromium nitride layer, a densified chromium nitride layer, and a glass layer, can be locally exposed to infrared laser light at several locations to withstand varying amounts of heat load, and shows the corresponding decrease in surface height. Associated graphs show cross-sections along horizontal axis 1 and vertical axis 2. In each graph, three regions of lower height can be seen via corresponding dips in the lines on the graph. Similarly, moving a single dip across the vertical axis corresponds to a single decrease in height along this axis. As can be seen, the degree of height variation depends on exposure, with additional exposure units resulting in larger variations in height.

[0052] Figure 5a and Figure 5b Comparative atomic force microscopy (AFM) images of the chromium nitride surface outside annealed spot (5a) and inside annealed spot (5b) are depicted. As can be seen, annealing via selective heating does not affect the surface morphology and roughness, and the differences in mean roughness and skewness are within the natural variability of the surface.

[0053] It will be understood that optical elements used in photolithography apparatus may already include a chromium nitride layer. It was previously not recognized that the surface shape of optical elements could be adjusted by densifying the chromium nitride. Thus, the method according to the invention can be used to repair existing optical elements that were previously thought impossible without using less sensitive processes that could generate unwanted particles. Since no particles are generated by the method described herein, they are suitable for in-situ use, which was previously impossible. Furthermore, in the case where the heat source is a laser, the laser can also be used to clean surfaces contaminated with particles and / or organic contaminants.

[0054] This disclosure can be used to control the shape of the surface of electrostatic wafer jigs, mask jigs, vacuum wafer chucks, and mirror blocks, etc.

[0055] It will be understood that references to multiple features can be used interchangeably with references to the singular forms of those features (such as, for example, "at least one" and / or "each"). The singular forms of features (such as, for example, "at least one" or "each") can be used interchangeably.

[0056] Although embodiments of the invention have been described in conjunction with a substrate, a substrate holder, and a substrate stage, in other embodiments, the invention can be used to clamp a mask MA (or other patterning apparatus) to a support structure MT of a photolithography apparatus (see [link to documentation]). Figure 1 ( ), or clamping another object.

[0057] While specific references are made to the use of photolithography apparatus in IC manufacturing in this document, it should be understood that the photolithography apparatus described herein can have other applications. Possible other applications include the fabrication of integrated optical systems, patterning for guiding and detecting magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, etc.

[0058] Although embodiments of the invention may be specifically referred to herein in the context of a lithography apparatus, embodiments of the invention can be used in other apparatuses. Embodiments of the invention can form part of a mask inspection apparatus, a metrology apparatus, or any apparatus for measuring or processing objects such as wafers (or other substrates) or masks (or other patterning equipment). These apparatuses may generally be referred to as lithography tools. Such lithography tools can use vacuum conditions or ambient (non-vacuum) conditions. An object holder according to embodiments of the invention can form part of a lithography tool.

[0059] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced in other ways different from those described. The description above is intended to be illustrative and not limiting. Therefore, it will be apparent to those skilled in the art that modifications can be made to the described invention without departing from the scope of the set forth claims.

[0060] Aspects of this disclosure are described in the following numbered clauses:

[0061] 1. An object holder configured to support an object, the object holder including a support surface having a plurality of support elements, wherein the plurality of support elements include a metal-Si multilayer, a metal-Ge multilayer, and / or a chromium nitride layer, the metal-Si multilayer, the metal-Ge multilayer, and / or the chromium nitride layer being configured to provide a selectively variable height for each support element via heat treatment of the metal-Si multilayer, the metal-Ge multilayer, and / or the chromium nitride layer.

[0062] 2. The object holder according to Clause 1, wherein the metal is selected from molybdenum, titanium, or any combination thereof.

[0063] 3. The object retainer according to Clause 1 or Clause 2, wherein the plurality of support elements are protrusions.

[0064] 4. The object holder according to any of the preceding clauses, wherein the object holder is preferably a wafer holder, wafer stage, mask stage, or mask fixture of an electrostatic wafer chuck.

[0065] 5. The object retainer according to any of the preceding clauses, wherein the plurality of support elements includes a top coating material, optionally wherein the top coating material is selected from chromium nitride, diamond-like carbon, or a combination thereof.

[0066] 6. The object holder according to any of the preceding clauses, wherein the thickness of the metal-Si multilayer, metal-Ge multilayer and / or chromium nitride layer is up to about 1400 nm, up to about 1300 nm, up to about 1200 nm, up to about 1100 nm, up to about 1000 nm, up to about 900 nm, up to about 800 nm, up to about 700 nm, up to about 600 nm, up to about 500 nm, up to about 400 nm, up to about 300 nm, up to about 200 nm or up to about 100 nm.

[0067] 7. The object holder according to any of the preceding clauses, wherein the thickness of the layers in the multilayer is in the range of about 2 nm to about 100 nm, and optionally in the range of about 10 nm to about 20 nm.

[0068] 8. A stage comprising an object holder as described in any of the preceding clauses.

[0069] 9. An optical element for a photolithography apparatus, the optical element comprising a metal-Si multilayer, a metal-Ge multilayer, or a chromium nitride layer, the metal-Si multilayer, metal-Ge multilayer, or chromium nitride layer being configured to selectively change shape via heat treatment of the metal-Si multilayer, metal-Ge multilayer, and / or chromium nitride layer, wherein optionally the metal is selected from titanium, molybdenum, or any combination thereof, and wherein optionally the optical element is a mirror or a mirror block.

[0070] 10. An apparatus for controlling the flatness of a surface, the apparatus comprising an object holder or optical element as described in any of the preceding provisions, and components for changing the phase configuration of the metal-Si multilayer, metal-Ge multilayer, and / or chromium nitride layer, optionally wherein the components include a laser and / or an electric heater.

[0071] 11. A photolithography apparatus or tool, comprising an object holder according to any one of Clauses 1 to 7, a stage according to Clause 8, an optical element according to Clause 9, or a device according to Clause 10.

[0072] 12. A method for correcting the flatness of a surface of an object holder or optical element of a photolithography apparatus, the method comprising: providing a surface comprising a metal-Si multilayer, a metal-Ge multilayer, and / or a chromium nitride layer, and controlling the flatness of the surface via heat treatment of the metal-Si multilayer, the metal-Ge multilayer, and / or the chromium nitride layer, optionally wherein the metal is selected from titanium, molybdenum, or any combination thereof.

[0073] 13. The method according to Clause 12, wherein the flatness of the surface is corrected by selectively heating the material to a predetermined temperature and annealing, optionally by laser heating.

[0074] 14. The method according to any one of clauses 12 and 13, wherein controlling the flatness of the surface occurs within the photolithography apparatus.

[0075] 15. Use in a photolithography method or apparatus of any one of Clauses 1 to 7, a stage according to Clause 8, an optical element for a photolithography apparatus according to Clause 9, an apparatus according to Clause 10, a photolithography apparatus or tool according to Clause 11, or a method according to any one of Clauses 12 to 14.

Claims

1. An object holder configured to support an object, the object holder comprising a support surface having a plurality of support elements, wherein the plurality of support elements comprises a metal-Si multilayer, and / or a metal-Ge multilayer, and / or a chromium nitride layer, the metal-Si multilayer, and / or the metal-Ge multilayer, and / or the chromium nitride layer being configured to provide a selectively alterable height of individual support elements via a heat treatment of the metal-Si multilayer, the metal-Ge multilayer, and / or the chromium nitride layer.

2. The object holder according to claim 1, wherein the metal is selected from molybdenum or titanium, or any combination thereof.

3. The object holder according to claim 1 or claim 2, wherein the plurality of support elements are burls.

4. The object holder according to any of the preceding claims, wherein the object holder is a wafer holder, such as a wafer chuck, preferably an electrostatic wafer chuck, or a wafer table, or wherein the object holder is a reticle holder, such as a reticle table or a reticle chuck.

5. The object holder according to any of the preceding claims, wherein the plurality of support elements comprises a top coating material, optionally wherein the top coating material is selected from chromium nitride, diamond-like carbon, or a combination thereof.

6. The object holder according to any of the preceding claims, wherein the thickness of the metal-Si multilayer, metal-Ge multilayer, and / or chromium nitride layer is up to about 1400 nm, up to about 1300 nm, up to about 1200 nm, up to about 1100 nm, up to about 1000 nm, up to about 900 nm, up to about 800 nm, up to about 700 nm, up to about 600 nm, up to about 500 nm, up to about 400 nm, up to about 300 nm, up to about 200 nm, or up to about 100 nm.

7. The object holder according to any of the preceding claims, wherein the thickness of the layer or layers in the multilayer is in the range of about 2 nm to about 100 nm, optionally in the range of about 10 nm to about 20 nm.

8. A wafer table comprising an object holder according to any of the preceding claims.

9. An optical element for a lithographic apparatus, the optical element comprising a metal-Si multilayer and / or a metal-Ge multilayer and / or a chromium nitride layer, the metal-Si multilayer and / or the metal-Ge multilayer and / or the chromium nitride layer being configured to selectively change in shape via a heat treatment of the metal-Si multilayer, metal-Ge multilayer, and / or chromium nitride layer, optionally wherein the metal is selected from titanium, molybdenum, or any combination thereof, optionally wherein the optical element is a mirror block.

10. An apparatus for controlling flatness of a surface, the apparatus comprising an object holder or optical element according to any of the preceding claims, and a means for changing the phase configuration of the metal-Si multilayer, metal-Ge multilayer and / or chromium nitride layer, the means comprising a heater, optionally wherein the means comprises a laser and / or an electrical heater.

11. A lithographic apparatus or tool comprising an object holder according to any of claims 1 to 7, a object table according to claim 8, an optical element according to claim 9, or an apparatus according to claim 10.

12. A method of correcting the flatness of a surface of an object holder or optical element of a lithographic apparatus, the method comprising: providing a surface comprising at least one material capable of changing volume upon heating, and controlling the flatness of the surface via heat treatment of the at least one material capable of changing volume upon heating, wherein the at least one material capable of changing volume upon heating is a chromium nitride multilayer or a metal-Si multilayer or a metal-Ge multilayer, optionally wherein the metal is selected from titanium, molybdenum, or any combination thereof.

13. The method according to claim 12, wherein correcting the flatness of the surface is achieved by selectively heating the at least one material to a predetermined temperature and annealing, optionally by laser heating.

14. The method according to any of claims 12 to 13, the method being a method of correcting the flatness of a surface of an object holder according to any of claims 1 to 7, the surface being a support surface, the support surface having a plurality of support elements, wherein the change in volume is used to selectively adjust the height of a support element.

15. The method according to any of claims 12 to 14, wherein controlling the flatness of the surface takes place within a lithographic apparatus.

16. Use of an object holder according to any of claims 1 to 7, an object table according to claim 8, an optical element for a lithographic apparatus according to claim 9, an apparatus according to claim 10, a lithographic apparatus or tool according to claim 11, or a method according to any of claims 12 to 15 in a lithographic method or apparatus.

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