Systems, apparatus and methods for selective surface treatment

Abstract

Disclosed herein is a shielding system for use in a surface treatment process, the shielding system comprising a first disk and a second disk, the first disk and the second disk being disposed substantially parallel to one another, the first disk having a slit-shaped opening, the second disk having a plurality of openings, and the first disk and the second disk being disposed to move relative to one another about a common axis, such that the slit can be positioned in one or more of the plurality of openings to form a passageway through the shielding system.

Description

[Technical Field]

[0001] The present invention relates to a system, apparatus and method for selective surface treatment of a support surface, and in particular to a system for selectively treating one or more burls on a surface adapted to support an object. [Background technology]

[0002] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus can, for example, project a pattern (often referred to as a "design layout" or "design") in a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate (e.g., a wafer).

[0003] As semiconductor manufacturing processes continue to advance, following a trend commonly referred to as "Moore's Law," the dimensions of circuit elements are continually shrinking, and the amount of functional elements, such as transistors, per device has steadily increased for decades. To keep up with Moore's Law, the semiconductor industry is seeking technologies that enable the creation of increasingly smaller features. To project patterns onto a substrate, lithography equipment can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Lithography equipment using extreme ultraviolet (EUV) radiation, with wavelengths in the 4 nm to 20 nm range, e.g., 6.7 nm or 13.5 nm, can be used to form smaller features on a substrate than lithography equipment using radiation with a wavelength of, e.g., 193 nm.

[0004] In a lithography apparatus, a substrate is clamped to a substrate support when transferring a pattern from a patterning device. The substrate support conventionally has a number of burls that support the substrate. The total area of the burls that contact the substrate is small compared to the total area of the substrate. This reduces the chance that contaminant particles randomly located on the surface of the substrate of the substrate support will be trapped between the burls and the substrate. Furthermore, in manufacturing the substrate support, the tops of the burls can be made more precisely flush than making a large surface precisely flat.

[0005] Additionally, the patterning device may be clamped to a mask support that comprises a plurality of burls on a clamping surface.

[0006] Manufacturing tolerances, contamination, and / or wear on the top surface of the burrs can result in inaccurate burr heights. Inaccurate burr heights can cause undesirable local distortions in an object (e.g., a substrate or patterning device) clamped to a support (e.g., a substrate support or a mask support). Such local distortions can contribute to inaccuracies in IC manufacturing. Therefore, there is a general need to provide systems and methods suitable for improving the surface properties of support surfaces. Summary of the Invention

[0007] According to a first aspect of the present invention, there is provided a shielding system for use in a surface treatment process, the shielding system comprising a body for shielding a first region of a surface from an environment, e.g., a plasma, during the surface treatment process, and an opening through the body of the system for exposing a second region of the surface during the surface treatment process. The shielding system may also be referred to as a plasma shielding system.

[0008] According to a second aspect of the present invention, there is provided a shielding system comprising a first disk and a second disk, the first disk and the second disk being substantially parallel to each other and having a common axis of rotation, the first disk having a slit-shaped opening, and the second disk having a plurality of openings, the first disk and the second disk being adapted to move relative to each other about the common axis, such that the slit can be positioned in one or more of the plurality of openings.

[0009] When disposed between a radiation source, e.g., a plasma radiation source, and a surface of an object and provided in a system configured to perform a surface treatment process on the surface of the object, a well-defined passage for the plasma can be defined to treat selected areas of the surface and shield the remainder of the surface.

[0010] According to a third aspect of the present invention there is provided a system configured to perform a plasma treatment process on a portion of a surface, the system comprising a plasma environment, for example a plasma source configured to generate the plasma environment, and an arrangement according to the first and / or second aspects.

[0011] According to a fourth aspect of the present invention there is provided a method of performing a plasma treatment process on a portion of a surface, the method comprising shielding a first region of the surface from a plasma environment and exposing a second region of the surface to the plasma environment and using a plasma shielding system according to the first and / or second aspects. [Brief explanation of the drawings]

[0012] [Figure 1] 1 depicts a schematic diagram of a lithographic apparatus; [Figure 2] 1 depicts a schematic representation of a substrate holder for use in a lithographic apparatus; [Figure 3] 1A and 1B are schematic diagrams illustrating a removable shielding system and a plurality of burls provided on a substrate holder according to an embodiment; [Figure 4]4A and 4B are schematic diagrams illustrating a shielding system according to one embodiment. [Figure 5] 5A and 5B are schematic diagrams of a shielding system according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] In this document, the terms "radiation" and "beam" are used to encompass 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).

[0014] The terms "reticle," "mask," or "patterning device," as used herein, may 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 created in a target portion of a substrate. The term "light valve" may also be used in this context. In addition to traditional masks (transmissive or reflective; binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0015] Figure 1 shows a schematic diagram of a lithographic apparatus LA. The lithographic apparatus LA includes an illumination system (also called an 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) T constructed 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 table) WT constructed to hold a substrate (e.g. resist-covered 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. 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 of the substrate W (e.g. comprising one or more dies).

[0016] In operation, the illumination system IL receives a radiation beam from the radiation source SO, for example via the 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 so that it has a desired spatial and angular intensity distribution in its cross-section in the plane of the patterning device MA.

[0017] The term "projection system" PS as used herein should be interpreted broadly to encompass various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, that are appropriate for the exposure radiation used and / or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein can be considered as synonymous with the more general term "projection system" PS.

[0018] 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 a space between the projection system PS and the substrate W, which is also known as immersion lithography. Details of immersion techniques are described in US6952253, which is incorporated herein by reference.

[0019] The lithographic apparatus LA may be of a type having two or more substrate supports WT (also known as "dual stage"). In such a "multiple stage" machine, the substrate supports WT can be used in parallel and / or can be used to perform preparatory steps for a subsequent exposure on a substrate W placed on one of the substrate supports WT, while simultaneously exposing a pattern on another substrate W on the other substrate support WT.

[0020] In addition to the substrate support WT, the lithographic apparatus LA may comprise a measurement stage. The measurement stage is configured to hold a sensor and / or a cleaning device. The sensor is configured to measure a property of the projection system PS or a property of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning device is configured to clean part of the lithographic apparatus, for example part of the projection system PS or part of the system for providing immersion liquid. The measurement stage may be moved below the projection system PS when the substrate support WT is spaced apart from the projection system PS.

[0021] In operation, radiation beam B is incident on a patterning device MA, e.g., a mask, held on a mask support T, and is patterned by a pattern (design layout) present on the patterning device MA. After passing through the mask MA, radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of a substrate W. With the aid of a second positioner PW and a position measurement system IF, the substrate support WT can be precisely moved, e.g., to position various target portions C in the path of radiation beam B at focused and aligned positions. Similarly, the first positioner PM and possibly further position sensors (not explicitly shown in FIG. 1 ) can be used to precisely position the patterning device MA with respect to the path of radiation beam B. The patterning device MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. As shown, substrate alignment marks P1, P2 occupy dedicated target portions, although they may also be located in spaces between the target portions. When the substrate alignment marks P1, P2 are located between target portions C, they are known as scribe-lane alignment marks.

[0022] For clarity of the invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes: X, Y, and Z. Each of the three axes is orthogonal to the other two. Rotation about the X axis is called Rx rotation. Rotation about the Y axis is called Ry rotation. Rotation about the Z axis is called Rz rotation. The X and Y axes define the horizontal plane, and the Z axis defines the vertical direction. The Cartesian coordinate system is not limiting of the invention and is used for illustration purposes only. Alternatively, another coordinate system, such as a cylindrical coordinate system, can be used to clarify the invention. The orientation of the Cartesian coordinate system may be different, for example, the Z axis has a component along the horizontal plane.

[0023] The substrate support WT, sometimes referred to as a substrate holder, is designed to accurately position the substrate during exposure. The substrate holder typically comprises a solid body formed of a rigid material with in-plane XY dimensions similar to those of the production substrate W to be supported. The surface of the solid body facing the substrate is provided with a number of protrusions or projections called burls. The distal surfaces of the burls conform to a substantially flat plane and support the substrate W. The burls offer several advantages: Contamination particles on the substrate holder or the substrate are likely to fall between the burls, preventing deformation of the substrate. Machining the ends of the burls to conform to a flat plane is easier than flattening the surface of the solid body. Additionally, the height of some of the burls can be reduced. Reducing the height of some of the burls can improve the overall height profile of the burls, potentially improving the clamping method for the substrate W.

[0024] 2 schematically shows a substrate holder 60, which may be a substrate support WT used in the lithographic apparatus LA. The substrate holder 60 is for supporting a substrate W. The substrate holder 60 includes a body 21. The body 21 has a body surface 22. A plurality of burls 20 are provided protruding from the body surface 22. The distal end surface of each burl 20 engages with the substrate W. The distal end surfaces of each burl 20 are substantially coplanar, i.e., the distal end face of each burl 20 substantially coincides with the support plane and supports the substrate W. The body 21 may be formed of ceramic, for example, SiC or SiSiC. The burr 20 may be formed of the same material as the body 21 or may comprise a different material, for example diamond-like carbon (DLC), diamond, boron-doped diamond (BDD), boron nitride, boron carbide, tungsten carbide, aluminum oxide, sapphire, titanium nitride, titanium carbonitride, titanium aluminum nitride, or titanium carbide, as disclosed in WO2020 / 135971, WO2020 / 221539, WO2021 / 249768.

[0025] The pitch of the burls 20 may be approximately in the range of 0.5 mm to 3 mm, for example, about 1.5 mm. The pitch of the burls 20 is the distance between the centers of two adjacent burls 20. The total area of the distal end faces of the burls 20 may be in the range of 1% to 3% of the total area of the substrate holder 60. The burls 20 may be frustoconical in shape, with the burl sides slightly sloping. Alternatively, the burl sides may be vertical or overhanging. The burls 20 may be circular in plan view. Alternatively, the burls 20 may be formed into other shapes as desired.

[0026] The body 21 may have a plurality of through holes 89 formed therein. The through holes 89 allow e-pins to protrude through the substrate holder 60 to receive the substrate W. The through holes 89 also allow the space between the substrate W and the substrate holder 60 to be evacuated. Evacuation of the space between the substrate W and the substrate holder 60 provides a clamping force, provided that the space above the substrate W is not also evacuated. The clamping force holds the substrate W in place. If the space above the substrate W is also evacuated, as is the case in lithographic apparatus using EUV radiation, the substrate holder 60 may be provided with an electrode to form an electrostatic clamp.

[0027] For example, other structures may be provided to control gas flow and / or thermal conductivity between the substrate holder 60 and the substrate W. The substrate holder 60 may be provided with electronic components. The electronic components may include heaters and sensors. The heaters and sensors may be used to control the temperature of the substrate holder 60 and the substrate W.

[0028] The burls 20 of the substrate holder 60 wear during use due to, for example, repeated loading and unloading of the substrate W. Furthermore, the burls 20 can become contaminated during use, for example, with particles or thin films of material. The wear and contamination of the burls 20 results in changes to the surface profile presented by the distal end faces of the burls 20.

[0029] Inaccuracies in the burl height can cause undesirable local distortions in the substrate W clamped to the substrate holder 60. Such local distortions can be a source of manufacturing inaccuracies.

[0030] The manufacture and / or maintenance of burrs 20 is known, comprising cleaning and polishing steps and ion beam figuring (IBF) steps, for example by systems and methods such as those disclosed in WO2018 / 224303.

[0031] A polishing step may be performed first.

[0032] A height profile of the distal end surface of the burls 20 may then be generated by measuring the height with a sensor. Such height measurements may be performed using any of a number of known techniques, for example, using a non-contact sensor, such as an optical sensor, or a contact sensor. The height profile may be determined, for example, by optical interferometry. A height profile map, also referred to as a hit map, may be generated, indicating the burls or areas requiring surface treatment. The determined height profile may be relative to measurements of a clamped substrate W of known thickness.

[0033] An IBF process may then be performed according to the determined height profile. The IBF process uses a high-energy ion beam, such as an argon ion beam, to remove material from the burrs. The IBF process may reduce the burr height variation determined by the height profile measurement.

[0034] The problem with the IBF process is that it is a global process. That is, the IBF process can be used to reduce the height of all burls 20 within the area of the substrate holder 60. The IBF process cannot reduce the height of only a single burl among the burls 20. Therefore, burls or areas that do not require surface treatment may be affected by the IBF process. The IBF process also affects the surface characteristics, such as roughness, of the burls 20 (not only those that should be treated but also those that should not be treated). The IBF process may create damaged or amorphous layers on the burls 20, which may accelerate wear of the burls 20.

[0035] The embodiments provide a new technique for surface treatment of an area, particularly for treatment of a selected area. The embodiments treat the surface using a plasma, for example a hydrogen plasma. Openings in a shielding system can define the area of the surface that is treated by the plasma.

[0036] An exemplary application of the embodiments is a technique for treating the surface of burls 20 or the support surface 22. The technique may be used to reduce the height of one or more burls 20. The embodiments may use a plasma to reduce the height of one or more burls 20 without substantially affecting the surface topology at or above the nanometer scale. In particular, the embodiments include using a shield to control the burs to which the hydrogen plasma is applied. The use of a shield may allow for the reduction of the height of only a single one of the burls 20. The embodiments may use the plasma to treat the areas of the support surface 22 between the burls 20 without substantially affecting the burls 20. This may be useful for removing contaminants on the areas of the support surface 22 between the burls 20.

[0037] Embodiments for altering the height profile of one or more of the burls 20 are described in more detail below with reference to Figures 3, 4A, 4B, 5A and 5B.

[0038] FIG. 3 shows a schematic cross-sectional view of a substrate holder comprising a number of burls 20, 303. The substrate holder may be the same as the substrate holder 60 / substrate support WT described above for use in the lithographic apparatus LA. The substrate holder is intended to support a substrate W. The substrate holder comprises a body 21 having a body surface 22 from which a number of burls 20, 303 protrude. FIG. 3 also shows a removable shield 301 according to one embodiment. The shield 301, i.e., a shielding system, is provided to cover at least a portion, and preferably most, of the burls 20. The shield 301 may be made of the same material as the substrate W. The shield 301 according to one embodiment will be described in more detail below.

[0039] A grinding step may first be performed to provide the desired height profile of the burls 20, 303. The grinding step may be performed when none of the burls 20, 303 are covered by the shield 301. The grinding step may be performed according to known techniques such as those used in extensive IBF processes.

[0040] The height profile of the distal end faces of the burls 20, 303 may then be determined according to known techniques used in large-area IBF processes, which may include determining the height profile relative to the optical interferometer measurements described above and / or measurements of a clamped substrate W of known thickness. Depending on the height profile, a decision may be made to reduce the height of one or more of the burls 20, 303.

[0041] The embodiment differs from known techniques in that a shield 301 is provided over the burls 20 of the substrate holder. The shield 301 may be selected and / or configured to include openings at the location of a single burl 303 where surface treatment, e.g., height reduction, is required, or at the location of selected surfaces in the support 22. The shield 301 may cover all distal end faces of the multiple burls 20 except for the distal end face of the single burl 303. Thus, the shield 301 shields the distal ends of all burls 20 and the areas 22 between the burls from the environment 302 above the shield 301, except for the single exposed burl 303.

[0042] If openings are provided in selected surface areas between the burls 20, the shield 301 therefore shields all distal ends of the burls 20 and the areas 22 between the burls from the environment 302 above the shield 301, except for the selected surface areas.

[0043] The shield 301 may include multiple coverable openings above the locations of the burls 20, 303. The shield 301 may be configured to cover all openings above the burls 20 where height reduction is not required, and not cover openings above one or more burls 303 where surface treatment, e.g., height reduction, is required.

[0044] A plasma treatment step may then be performed by providing a plasma environment above the shield 301. For example, a hydrogen plasma may be provided. Many known techniques can be used to generate the plasma environment. These include the use of ion generators, electrodes, hot filaments, and microwave generators. The plasma environment may be generated according to the techniques described in "Plasma generation and Plasma Sources," H. Conrads and M. Schmidt, Plasma Sources Science and Technology, vol. 9 (4) p. 441, 2000.

[0045] The object holder, e.g., the substrate support WT or the mask support T, may be moved into an apparatus for generating a plasma environment. The apparatus may include a plasma source, e.g., a hydrogen plasma source. The plasma source is preferably positioned directly above the center of the object holder so that deformation of the object caused by variations in etching rate due to the position of the plasma source is bowl-shaped and therefore easily correctable. During the plasma processing step, the object holder, e.g., the substrate support, may be grounded. The ion energy in the plasma processing step is preferably at least 2 eV to achieve an adequate etching rate. If the ion energy in the plasma processing step is too high, the ions may damage exposed structures. The ion energy in the plasma processing step is preferably less than 15 eV, more preferably less than 10 eV, and even more preferably less than 6 eV.

[0046] A control device or controller may be provided for setting and controlling the ion energy of the plasma, which may be the energy of a hydrogen plasma. Further, the controller may be configured to control the ratio of ions to radicals in the plasma, which may be the ratio of hydrogen ions to hydrogen radicals in the plasma. Control of the energy and ratio is advantageous for efficient treatment of the surface.

[0047] In the plasma treatment process, the plasma radiation can etch the distal end of a single exposed burl 303. The plasma radiation may be used to etch away a quantifiable amount of material. The etching process can reduce the height of the exposed burl 303 without substantially damaging the exposed burl 303. The etching process may reduce the height of the exposed burl 303 at a rate of approximately 5 nm to 25 nm per hour. The rate of the etching process can depend on the applied gas or ion pressure and the distance from the plasma source. The duration of the etching process can be used to control the applied surface treatment and, therefore, the reduction in the height of the burl 303. The exposed surface can remain uniform and clean. The etching process is independent of the roughness of the surface being etched, i.e., the etching process can be homogeneous. All burls 20 whose distal end faces are covered by the shield 301 can be substantially unaffected by the plasma environment.

[0048] All processes may be automatically controlled by a processing system. In particular, the processing system may receive a height profile map of the target surface. The processing system may be manually controlled or may operate automatically to determine which regions and / or burls require selective surface treatment. Furthermore, the processing system may (automatically) configure the shield 301 based on the selected regions and automatically control the plasma treatment process to treat the selected regions, e.g., burls 303.

[0049] Thus, embodiments allow for controlled processing of selected surfaces. In particular, embodiments allow for controlled reduction of the height of a single burl 303. By repeating the process on different burls 20 (or different selected areas), the height of multiple burls 20 can be reduced. The reduction of burl height can be performed precisely depending on the determined burr height profile. Embodiments thereby improve the burr 20 height profile. The use of plasma according to embodiments allows for the reduction of the height of one or more burls without substantially affecting the nanometer-scale or larger surface topology. This is an advantage over known IBF techniques, where high-energy sputtering causes surface sputtering.

[0050] Embodiments include other techniques for shielding or masking the burls 20 while leaving one or more burls 303 exposed for plasma processing. Alternatively, or additionally, a removable coating may be used to shield the burls 20.

[0051] Those skilled in the art will appreciate that the same plasma treatment using shields as disclosed above may be applicable to selective surface treatment of the mask support T. The mask support T may comprise burls for supporting the patterning device MA.

[0052] Those skilled in the art will understand that the shield 301 as disclosed above may be used in a system and / or process for selective surface treatment using radiation, where the radiation is provided as one of laser radiation, an electron beam, and an ion beam. The use of laser radiation in combination with the shield 301 enables selective surface treatment of an object by laser ablation. The laser radiation may be radiation having a wavelength within the visible and / or (extreme) ultraviolet spectral range. The wavelength may be selected depending on the material (e.g., contaminant material) deposited on the surface to be treated or the material composition of the surface's substrate, e.g., the burl 303.

[0053] Figures 4A and 4B schematically illustrate another shielding system 400 according to one embodiment. Figure 4A is an exploded perspective view of the shielding system 400. Figure 4B shows the shielding system 400 assembled.

[0054] The shielding device 400 includes a first plate 401 and a second plate 402. In this embodiment, the first plate 401 is described as a first disk 401, and the second plate 402 is described as a second disk 402. However, the embodiment also includes the first and second plates 401, 402 having shapes other than disks. For example, both the first and second plates 401, 402 may be substantially rectangular.

[0055] Both the first disk 401 and the second disk 402 are substantially planar. The diameters of the first disk 401 and the second disk 402 may be substantially the same as each other, and may be substantially the same as or slightly larger than the diameter of the area of the substrate holder that is covered by the burls.

[0056] The first disc 401 and the second disc 402 may be provided with mechanical means to stiffen the discs, which can prevent or limit deformation of one or both discs.

[0057] The first disk 401 may include a slit opening 404, i.e., a first opening. In FIGS. 4A and 4B, the slit opening 404 is shown as a wedge-shaped opening. However, the slit opening 404 may alternatively be rectangular or have an irregular shape. The slit opening 404 may be provided from the center of the disk toward the edge of the disk. Alternatively, the slit opening does not continue to the edge, but rather a portion of the disk material closes the slit opening at the edge of the disk. In this way, the disk forms a closed loop around the periphery of the disk. This is beneficial for preventing plasma from reaching the surface of the object to be shielded during the surface treatment process, especially in the surface area of the object's edge that is under the shielding system.

[0058] The second disk 402 includes a plurality of openings 403, i.e., second openings. Each opening 403 may be circular, square, rectangular, or elliptical. Preferably, each (second) opening 403 is circular. Each opening 403 may be located at a different radial and axial position from the center point of the second disk 402. The size of each opening 403 is appropriate for exposing only a single bur. The size of each opening 403 may be different. The sizes of the openings 403 may be similar. The diameter of each opening 403 is preferably larger than the diameter of each bur 20. When the bur 20 has a diameter of approximately 200 μm and a pitch of approximately 1.5 mm, the diameter of each opening 403 may be approximately 200 μm to 1300 μm, preferably approximately 400 μm to 1100 μm. If the burls 20 have a diameter of about 350 μm and a pitch of 2.5 mm, the diameter of each opening 403 may be about 350 μm to 2150 μm, preferably about 550 μm to 1950 μm.

[0059] A plurality of openings 403 (or second openings) may be provided in the second disc 402 along a spiral arrangement. The second disc 402 may include openings 403 arranged along one or more spirals. The openings 403 may be arranged according to a phyllotactic spiral.

[0060] 4B , when the shielding system 400 is assembled, the first disk 401 may be provided adjacent to or in contact with the second disk 402. The plane of the first disk 401 may be parallel to the plane of the second disk 402, with the distance between the first disk 401 and the second disk 402 being less than 100 μm. The center points of the first disk 401 and the second disk 402 may be aligned with each other on a line perpendicular to the planes of the first disk 401 and the second disk 402. When the shielding system 400 is provided on the burl 20 of the substrate holder, the second disk 402 is preferably closer to the substrate holder than the first disk 401.

[0061] The thickness of each of the first disk 401 and the second disk 402 may be less than 2 mm. The shielding system 400 is preferably as thin as possible. The thickness of the shielding system 400 is preferably less than twice the diameter of one (second) opening 403, more preferably less than the diameter of one opening 403, and even more preferably less than half the diameter of one opening 403.

[0062] The shielding system 400 may include a rotary joint 405 for supporting relative axial rotation between the first disk 401 and the second disk 402. The relative axial rotation between the first disk 401 and the second disk 402 may be controlled by operation of a motor. The motor may be configured to rotate the first disk 401 while keeping the second disk 402 stationary, or to rotate the second disk 401 while keeping the first disk 402 stationary, or to rotate both the first disk 401 and the second disk 402 in opposite directions. The motor may also be configured to rotate the entire shielding system 400 axially without relative axial rotation between the first disk 401 and the second disk 402. The motor may be provided above the shielding system 400 or to the side of the shielding system 400. The use of the rotary joint 405 is optional, and the rotary shaft does not have to be fixed, especially if the motor is mounted on the side of the shielding system 400. Also, the relative movement of the first and second disks 401, 402 may be linear only, with no rotational movement occurring.

[0063] When the first disk 401 and the second disk 402 are rotated relative to one another about their axes, the slit openings 404 (first openings) of the first disk 401 can be moved over any of the openings 403 (second openings). The slit openings 404 can be shaped such that all of the openings 403 are covered by the first disk 401 except for a single opening 406 over which the slit opening 404 is located. At all positions along its length, the width of the slit openings 404 can be smaller than the spacing between adjacent openings 403, so that no position of the slit opening 404 exposes multiple openings 403.

[0064] Thus, only a single opening 406 of the plurality of openings 403 can provide a passageway through the shielding system 400. The passageway through the shielding system 400 is defined by which opening 403 is covered by the slit opening 404. By rotating the first disk 401 relative to the second disk 402, a different one of the openings 403 can define a passageway through the shielding system 400.

[0065] The position of the slit in the first disk 401 and the orientation of the second disk 402 (whereby one of the openings 403 is located) may be set and controlled by a control unit, e.g., a controller, which may determine the position and orientation of both disks based on a height profile map or hit map.

[0066] All the burls 20 may be arranged on the substrate holder in multiple concentric circles with different radii. The radial position of each burl opening in the second disk 402 may be arranged such that when the shielding system 400 is provided above the burls 20, there is one opening 403 that can be aligned with each burl simply by rotating the second disk 402 about its axis. Thus, rotation of the first disk 401 relative to the second disk 402 and rotation of the shielding system 400 can be used to provide a passage through the shielding system 400 above any burl 20 (other than the central burl 20) on the substrate holder. In this way, the shielding system 400 may be configured to expose a specific one of the burls 20.

[0067] If the substrate holder includes a centrally located burl 20, the shielding system 400 may be moved horizontally to align the passage therethrough with the centrally located burl 20 in order to expose the centrally located burl 20. Alternatively, a separate shield may be used to expose the centrally located burl 20.

[0068] The shielding system 400 can be used in the above-described plasma processing steps according to embodiments. During a surface processing step, such as a plasma processing step, both the first disk 401 and the second disk 402 may be grounded. Preferably, during the surface processing step, the object being processed, such as a substrate support or a mask support, is grounded.

[0069] By controlling the relative rotation of the first disk 401 and the second disk 402 and / or the overall rotation of the shielding system 400, the shielding system 400 may be reconfigured during a plasma processing step, thereby exposing multiple burls 20, or selected areas between burls, during the same plasma processing step.

[0070] The shielding system 400 may be adapted to rest on the burls 20 during the plasma processing step. The shielding system 400 may be elevated so that it does not rest on the burls 20 during rotation to reconfigure the shielding system 400 to change the exposed burls 303 to avoid damaging the burls and / or the shielding system 400.

[0071] Alternatively, the shielding system 400 may be held slightly above the burls 20 during the plasma treatment process. The space between the shielding system 400 and the burls 20 must be large enough to avoid problems with sagging of the shielding system 400 causing collisions between the shielding system 400 and the burls 20. Mechanical means may be provided on one or both disks to prevent sagging. However, it is preferable to make the space between the shielding system 400 and the burls 20 as small as possible, taking into account the tolerance for sagging. The space between the shielding system 400 and the burls 20 is preferably smaller than the Debye length of the plasma (approximately 100 μm).

[0072] The determination of the height profile, the configuration of the shielding system 400, and the operation of the entire plasma processing process may be automatically controlled by one or more processing systems. In particular, the controller may receive data regarding one or more burs 20, or areas on the support surface, to be processed, and automatically configure the shielding system 400 depending on the received data.

[0073] Thus, embodiments provide techniques for improving the height profile of burls 20. The height of each burl 20 can be individually varied. The height of each burl can also be precisely varied. The exposure time to the plasma source can be controlled with millisecond precision. With the plasma process providing an etch rate of approximately 5 to 25 nm per hour, the reduction in burl 20 height can be controlled down to the picometer level.

[0074] The design of the substrate holder, and in particular the typical height of each burl 20 on the substrate holder, will vary depending on the process for which the substrate holder will be used. For example, typical burl heights for substrate holders designed for use in lithography processes may range from about 10 μm to about 200 μm. For burls having a height of about 10 μm, embodiments may be used to reduce their height to less than about 1 nm, or more than 1 nm if necessary. For burls having a height of about 200 μm, embodiments may be used to reduce their height to about 10 nm, or more than 10 nm if necessary.

[0075] The embodiments include many modifications and variations to the above-described techniques.

[0076] Embodiments include the use of a shield to expose multiple burls 20 simultaneously. For example, a shielding system may include a single opening large enough to expose multiple burls 20. The height of multiple burls 20 may be reduced simultaneously. Then, if desired, another shielding system may be used to individually reduce the height of one or more burls 20. This may be a faster process than only reducing the height of the burls 20 individually.

[0077] Embodiments also include the use of a shielding system with multiple openings to expose multiple burls 20 simultaneously.

[0078] It should be noted that the distal end faces of the burls 20 may be substantially flat and the preferred height profile of the burls 20 may be the same as the profile of the substrate W clamped to the substrate holder. Thus, if the substrate has a slight bowl-like deformation, the preferred profile provided by the distal end faces of the burls 20 will have a slight convex shape so that the end of each burl is flush with the surface of the substrate.

[0079] Embodiments include modifying the height profile provided by the distal end faces of the burls 20 to better match the general shape of the substrate W clamped to the substrate holder 60. The height profile provided by the distal end faces of the burls 20 need not be flat.

[0080] The embodiments are not limited to the specific application of reducing the height of burls, and more general embodiments include using a plasma to treat a surface, with openings in a shielding system defining areas of the surface to be treated.

[0081] Shielding systems according to embodiments are not limited to being disks, and embodiments include the use of shields of any shape, so long as the shield defines a first area of the surface that is not exposed to the plasma environment, and at least one opening in the shield defines a second area of the surface that is exposed to the plasma environment.

[0082] Those skilled in the art will understand that the shielding system 400 as disclosed above may be used in systems and / or processes for selective surface treatment using radiation, where the radiation is provided as one of laser radiation, an electron beam, and an ion beam. The use of laser radiation in combination with the shielding system 400 enables selective surface treatment of an object by laser ablation. The laser radiation may be radiation having a wavelength within the visible and / or (extreme) ultraviolet spectral range. The wavelength may be selected depending on the material (e.g., contaminant material) deposited on the surface to be treated or the material composition of the surface's substrate, e.g., burl.

[0083] An embodiment includes a shielding system 500 comprising a plurality of movable plates or blades. For example, the shielding system 500 may comprise a first layer having a first pair of substantially rectangular plates 501, as shown schematically in FIGS. 5A and 5B. FIG. 5A shows an exploded view of the shielding system 500. FIG. 5B shows an assembled view of the shielding system 500. The first pair of plates 501 may be spaced apart from one another such that a first linear opening 504, e.g., a first slit opening, is present therebetween. The shielding system 500 may also comprise a second layer having a second pair of substantially rectangular plates 502. The second pair of plates 502 may be spaced apart from one another such that a second linear opening 503, e.g., a second slit opening, is present therebetween. The first and second pairs of plates 501, 502 may be oriented such that the first and second linear openings 504, 503 (or slit openings) are substantially perpendicular to one another. This creates a rectangular or square opening 506 through the shield where the first and second linear openings overlap each other. The size and location of opening 506 can be varied by changing the position and spacing of the first and second pairs of plates 501, 502.

[0084] The opening 506 may be provided with an auxiliary element adapted to move with the opening. The auxiliary element may have a central circular opening such that the passageway through the shielding system 500 matches the bottom diameter of the burr. When cylindrically shaped burrs are being processed according to certain aspects of the present invention, it is preferred that the passageway 506 in the shielding system 500 be of a similar shape and size. This may minimize or prevent unintended processing of the area surrounding the intended burr.

[0085] The first and second pair of plates 501, 502 are sized to at least partially, preferably completely, shield the surface of an object that is to be selectively surface treated with plasma, and both the first and second plates 501, 502 are similar in size to a substrate support WT or a mask support T used in a lithographic apparatus.

[0086] The shielding device 500 comprising the first and second pair of plates can be preferably used for the surface treatment of an object comprising burrs arranged non-concentrically, for example, burrs arranged in a straight line.

[0087] The positions of the first slit opening 504 and the second slit opening 503, and thereby the placement of the opening or passage 506, may be set and controlled by a control unit, e.g., a controller. The controller may determine the positions of both slit openings based on a height profile map or hit map.

[0088] During a surface treatment process, for example during a plasma treatment process, both the first pair of plates 501 and the second pair of plates 502 may be grounded. Preferably, during a surface treatment process, the object to be treated, for example a substrate support or a mask support, is grounded.

[0089] According to one embodiment, an apparatus for adjusting components of a lithographic apparatus is provided. The apparatus comprises a housing configured to contain a plasma, e.g., a hydrogen plasma. The plasma is provided by a plasma generator. A support means is provided for supporting an object to be treated with the plasma. A shielding system 301, 400, 500 is disposed between the plasma source and the support means and shields at least a portion of the surface of the object. The apparatus is configured to control at least one of the ratio of ions (e.g., hydrogen ions) to radicals (e.g., hydrogen radicals) in the plasma, the energy of the plasma, and the position of a passage or opening through the shielding system for selective surface treatment of the object.

[0090] Embodiments include moving the substrate support to a specific apparatus for performing the plasma treatment process. Alternatively, the plasma treatment process may be performed in the same apparatus used for the lithography or metrology process (in-situ). The apparatus may already include a plasma source for generating a plasma environment with appropriate ion energy, e.g., hydrogen plasma. Alternatively, a new plasma source may be included in the apparatus.

[0091] Embodiments are not limited to surface treatment of substrate holders. Embodiments include treating the surface of any structure. Also, the applied surface treatment need not alter the surface profile, but may simply clean the surface, for example. In particular, embodiments include surface treatment of mask / reticle / patterning device support structures, which may comprise burls. Embodiments may be used to clean and / or alter the profile of the burls.

[0092] Embodiments are not limited to surface treatment with plasma, e.g., hydrogen plasma. Embodiments include treating surfaces with radiation, e.g., laser radiation, electron beams, or ion beams. For example, when using laser radiation, e.g., high-energy photons or high beam intensity, one skilled in the art can position a shielding system to select specific areas on the surface for treatment using laser radiation. Laser ablation can be initiated at selected surface areas or sites by laser radiation. This can, for example, treat the top surfaces of burls. That is, the height of the burls can be reduced by laser-induced surface treatment (e.g., laser ablation), or contamination of the burls can be removed.

[0093] The aforementioned shielding system allows precise selection of areas or sites that require treatment with radiation (plasma radiation, laser radiation, electron beam, ion beam).

[0094] The embodiment includes the following numbered sections: 1. A shield for use in a plasma treatment process of a surface, the shield comprising: a body for shielding a first area of the surface from the plasma treatment process; and an opening through the body of the shield for exposing a second area of the surface during the plasma treatment process. 2. The plasma treatment process is for reducing the height of at least one burr, and the body of the shield is configured to shield a plurality of burrs in the first region from the plasma treatment process; 10. The shield of claim 1, wherein the opening through the body of the shield is configured to expose at least one burl in the second region during the plasma treatment step. 3. The shield of clause 2, wherein the opening is configured to expose only a single burl of the plurality of burls. 4. The shield of clause 2 or 3, wherein the shield comprises a first plate having a slit opening and a second plate having a plurality of burl openings, the first plate and the second plate being rotatable relative to one another, the opening through the shield being one of the plurality of burl openings, and the burl opening providing the opening through the shield being dependent on the relative rotational positions of the slit opening and the plurality of burl openings. 5. A configuration comprising: a structure having a surface; and a shield according to any of clauses 1 to 4 for covering at least a portion of the surface. 6. The arrangement of clause 5, wherein the structure comprises a plurality of burls, and the shield is disposed to cover at least a portion of the plurality of burls. 7. The arrangement of clause 6, wherein the structure is a substrate holder. 8. A system configured to perform a plasma treatment process on a portion of a surface, the system comprising: a plasma source configured to generate a plasma environment; and the arrangement of any of clauses 5 to 7. 9. The system of clause 8, wherein the system is configured to perform a plasma treatment process on one or more of the plurality of burls. 10. The system of clause 8 or 9, wherein the plasma source is configured to generate ions having an energy of preferably at least 2 eV, and preferably less than 15 eV, more preferably less than 10 eV, and even more preferably less than 6 eV. 11. The system of any of clauses 8 to 10, wherein the system is further configured to perform a lithography process and / or a metrology process. 12. A method of performing a plasma treatment process on a portion of a surface, the method comprising: shielding a first region of the surface from a plasma environment; and exposing a second region of the surface to the plasma environment. 13. The method of clause 12, wherein the surface comprises a plurality of burls, and the plasma treatment step is for reducing a height of at least one burl, and wherein the plurality of burls in the first region are shielded from the plasma treatment step and at least one burr in the second region is exposed during the plasma treatment step. 14. The method of clause 13, further comprising determining a height profile of the plurality of burrs; and performing the shielding in dependence on the height profile. 15. The method of clause 13 or clause 14, wherein the shielding exposes only one crowbar. 16. The method of any of clauses 13 to 15, further comprising varying the exposed burrs during the exposure step by reconfiguring the shielding of the plurality of burrs during the exposure step, and / or repeating the exposure step with different shielding configurations to vary the exposed burrs for each exposure step. 17. A shield according to any one of clauses 1 to 4, or a system according to any one of clauses 8 to 11, or a method according to any one of clauses 12 to 16, wherein the plasma treatment step is a hydrogen plasma treatment step. 18. A shielding system for use in a surface treatment process, comprising a first disc and a second disc; the first disk and the second disk are disposed substantially parallel to each other, the first disk has a slit-shaped opening, and the second disk has a plurality of openings; A shielding system, wherein the first and second disks are configured to move relative to one another about a common axis, whereby a slit is positionable in one or more of the plurality of openings to form a passageway through the shielding system. 19. The shielding system of clause 18, wherein the passageway is configured to expose only selected areas on the surface of the object undergoing surface treatment. 20. The shielding system of clause 18 or 19, wherein the passage is configured to expose only one of a plurality of burls provided on the surface of the object undergoing surface treatment. 21. The shielding system of any of clauses 18 to 20, wherein the plurality of openings are provided in the second disk along one or more spiral arrangements. 22. A shielding system for use in a surface treatment process, comprising a first layer and a second layer, the first layer and the second layer being disposed substantially parallel to each other; the first layer comprises a first pair of plates and provides a first slit opening between the first pair of plates; the second layer comprises a second pair of plates providing a second slit opening between the second pair of plates, the first slit opening and the second slit opening being substantially perpendicular to one another to provide an opening through the shield depending on the relative positions of the first slit opening and the second slit opening. 23. A shielding system according to any of clauses 18 to 22, wherein the shielding system is configured to shield a first area of the object surface from radiation during the surface treatment process and expose a second area of the object surface to radiation through passages in the shielding system. 24. The shielding system of clause 23, wherein the radiation is a plasma, laser radiation, an electron beam, or an ion beam. 25. A shielding system as described in any of clauses 18 to 24, wherein the first disc and the second disc, or the first layer and the second layer, are grounded during the surface treatment process. 26. An apparatus for conditioning a component of a lithographic apparatus, comprising: a housing configured to contain a plasma; a plasma generator for supplying said plasma; support means arranged to support said component to be treated with said plasma; and a shielding system according to any of clauses 18 to 25 arranged between the plasma source and the support means to shield at least a part of a surface of said component; The apparatus is configured to control at least one of a ratio of ions to radicals in the plasma, an energy of the plasma, and a position of an opening through the shielding system for selective surface treatment of the component. 27. A method of performing a surface treatment process on a portion of a surface, the method comprising shielding a first area of the surface from radiation and exposing a second area of the surface to the radiation to perform selective surface treatment. 28. The method of clause 27, wherein the radiation is a plasma, laser radiation, an electron beam, or an ion beam. 29. The method of clause 27 or clause 28, wherein the surface comprises a plurality of burls, and the surface treatment step is for surface treatment of at least one burl, and wherein the plurality of burls in the first region are shielded from the surface treatment step and at least one burl in the second region is exposed during the surface treatment step. 30. The method of any of clauses 27 to 29, further comprising determining a height profile of the plurality of burrs and performing the shielding in dependence on the height profile. 31. The method of any of clauses 27 to 30, wherein the shielding system exposes only one crowbar. 32. The method of any of clauses 27 to 31, further comprising varying the exposed burrs during the exposure step by reconfiguring the shielding system of the plurality of burrs during the exposure step, and / or repeating the exposure step with different shielding configurations to vary the exposed burrs for each exposure step. 33. A shielding system according to any of clauses 18 to 25, wherein the position of the slit in the first disk and the orientation of the second disk, or the first slit opening and the second slit opening, are set and controlled by a controller.

[0095] Although specific reference may be made in this specification to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, including the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0096] Although specific reference may be made herein to embodiments of the invention in the context of lithography apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatus may be generally referred to as lithography tools. Such lithography tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0097] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be understood that, where the context permits, the invention is not limited to optical lithography and may be used in other applications, such as, for example, imprint lithography.

[0098] 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.), among others. Furthermore, firmware, software, routines, and instructions may be described herein as performing certain operations. However, it should be understood that such description is merely for convenience and that such operations actually result from a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc., which may cause actuators or other devices to interact with the physical world.

[0099] While specific embodiments of the present invention have been described above, it should be understood that the invention may be practiced otherwise than as described. The above description is intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the invention as described without departing from the scope of the claims set forth below.

Claims

1. A shielding system for use in a surface treatment process of an object, the shielding system comprising: a first disk and a second disk; the first disk and the second disk are disposed substantially parallel to each other; the first disk has a slit-shaped opening; the second disk includes a plurality of openings; the first and second disks are mounted to move relative to one another about a common axis whereby a slit is positionable in one or more of the plurality of openings to form a passageway through the shielding system; A shielding system, wherein the passageway is configured to expose only selected areas on the surface of the object that will undergo the surface treatment process.

2. The shielding system of claim 1 , wherein the passage is configured to expose only one of a plurality of burls on the surface of the object undergoing the surface treatment.

3. 3. The shielding system of claim 1 or 2, wherein the plurality of openings are disposed in the second disk along one or more spiral arrangements.

4. 4. The shielding system of claim 1, wherein the shielding system is configured to shield a first area of an object surface from radiation during the surface treatment process and expose a second area of the object surface to the radiation through the passage in the shielding system.

5. The shielding system of claim 4 , wherein the radiation is a plasma, laser radiation, an electron beam, or an ion beam.

6. The shielding system of claim 1 , wherein the first disk and the second disk are grounded during the surface treatment process.

7. The shielding system according to claim 1 , wherein the first disk and the second disk are positionally controlled by a controller.

8. 1. An apparatus for adjusting a component of a lithographic apparatus, comprising: a housing configured to contain the radiation; a radiation generator for providing said radiation; support means arranged to support said component to be treated with said radiation; a shielding system according to any one of claims 1 to 7 provided between the radiation source and the support means for shielding at least a part of a surface of the component; the radiation is a plasma; The apparatus is configured to control at least one of a ratio of ions to radicals in the plasma, an energy of the plasma, and a position of an opening through the shielding system for selective surface treatment of the component.

9. 1. A method of performing a surface treatment process on selected areas of a surface of an object, comprising: selecting the area of the surface of the object to be treated; Shielding a first area of the surface that is not the selected area of the surface from radiation using a shielding system according to any one of claims 1 to 7; exposing the selected areas of the surface to the radiation to perform selective surface treatment.

10. The method of claim 9 , wherein the radiation is a plasma, laser radiation, an electron beam, or an ion beam.

11. the surface comprises a plurality of burls; The surface treatment step is for surface treatment of at least one bar, 11. The method of claim 9 or 10, wherein a plurality of burls in the first region are shielded from the surface treatment process and at least one burl in the selected region is exposed during the surface treatment process.

12. determining a height profile of a plurality of burls; The method of any of claims 9 to 11, further comprising performing the occluding in dependence on a height profile map.

13. The method of any of claims 9 to 12, wherein the shielding system exposes only one crowbar.

14. Varying the exposed burrs during the surface treatment process by reconfiguring the shielding system for multiple burrs during the surface treatment process; and / or 14. The method of any of claims 9 to 13, further comprising repeating the surface treatment step with different shielding configurations to vary the exposed burrs for each surface treatment step.

15. The method of claim 10 , wherein the plasma is a hydrogen plasma.

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