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

The substrate is clamped onto a substrate holder in the lithographic apparatus when transferring a pattern from the patterning device. The substrate holder conventionally has a plurality of burls to support the substrate. The total area of the burls that contact the substrate is small compared to the total area of the substrate. Therefore, the chance that a contaminant particle randomly located on the surface of the substrate or the substrate holder is trapped between a burl and the substrate is small. Also, in manufacture of the substrate holder, the tops of the burls can be made more accurately coplanar than a large surface can be made accurately flat.

When a substrate is first loaded onto the substrate holder in preparation for exposure, the substrate is supported by so-called e-pins which hold the substrate at three positions. While the substrate is being held by the e-pins, its own weight will cause the substrate to distort, e.g. becoming convex when viewed from above. To load the substrate onto the substrate holder, the e-pins are retracted so that the substrate is supported by burls of the substrate holder. As the substrate is lowered onto the burls of the substrate holder, the substrate will contact in some places, e.g. near the edge, before other places, e.g. near the center. Any friction between the burls and the lower surface of the substrate may prevent the substrate from fully relaxing into a flat unstressed state. This can lead to focus and overlay errors during exposure of the substrate.

The substrate holder is commonly made of a ceramic material such as silicon carbide (SiC) or SiSiC, a material having SiC grains in a silicon matrix. Such a ceramic material can readily be machined to a desired shape using conventional manufacturing methods. When substrates are loaded and unloaded from the substrate holder, the ceramic material can wear quickly. The comparably high frictional coefficient of the ceramic material may also prevent the substrate from relaxing into a flat unstressed state when loaded onto the substrate holder.

It has been proposed to provide a layer of diamond-like carbon (DLC), for example DLC a-C:H, a-C or ta-C, on the burls of the substrate holder. Such a layer is resistant to wear and reduces the friction between the substrate holder and the substrate. DLC may be deposited directly onto the burls of the substrate holder, because deposition of DLC is possible at temperatures below <NUM>. Temperatures exceeding <NUM> risk damage to the substrate holder.

The inventors have recognized that the performance of such DLC-coated substrate holders does not meet expectations. The DLC deposited on the substrate holder wears about <NUM> times faster than desirable, requiring re-polishing and re-conditioning of the substrate holder much sooner than the desired operational period.

It is thus desirable, for example, to provide on a body a wear-resistant material with improved wear-resistant properties compared to a DLC-coated body. The wear-resistant material may also have other desirable properties compared to a DLC-coated body, such as improved corrosion resistance, for example.

According to an aspect of the invention, there is provided a method for providing a wear-resistant material on a body, the method comprising the steps of: providing a body made of glass, ceramic or glass-ceramic, wherein the body comprises a main body having a main body surface and a plurality of unfinished burls projecting from the main body surface, each unfinished burl having a distal end surface; providing a wear-resistant material having a hardness of more than <NUM> GPa; brazing or laser welding the wear-resistant material to the body; and the wear-resistant material is provided on the distal end surface of each of the plurality of unfinished burls so as to form a support structure comprising a plurality of burls.

According to another aspect of the invention, there is provided a composite body comprising: a body made of glass, ceramic or glass-ceramic, wherein the body is an unfinished substrate holder comprising a main body having a main body surface and a plurality of unfinished burls projecting from the main body surface, each unfinished burl having a distal end surface, a wear-resistant material having a hardness of more than <NUM> GPa, an intermediate brazing layer or an interdiffusion layer connecting the body and the wear-resistant material, and the wear-resistant material is provided on the distal end surface of each of the plurality of unfinished burls, forming a support plane for supporting a substrate.

In the present document, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g. with a wavelength of <NUM>, <NUM>, <NUM>, <NUM> or <NUM>) and extreme ultraviolet (EUV) radiation (e.g. with a wavelength around <NUM>).

The term "reticle", "mask" or "patterning device" as employed in this text may be broadly interpreted as referring to a generic patterning device that can be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate. The term "light valve" can also be used in this context. Besides the classic mask (transmissive or reflective, binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include a programmable mirror array and a programmable LCD array.

<FIG> schematically depicts a lithographic apparatus LA of an embodiment. The lithographic apparatus LA comprises:.

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

The term "projection system" PS used herein should be broadly interpreted as encompassing various types of projection system, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and/or electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being 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 may be considered as synonymous with the more general term "projection system".

The lithographic apparatus LA may be of a type having two or more support tables, e.g., two or more support tables or a combination of one or more support tables and one or more cleaning, sensor or measurement tables. For example, the lithographic apparatus LA is a multi-stage apparatus comprising two or more tables located at the exposure side of the projection system PS, each table comprising and/or holding one or more objects. In an example, one or more of the tables may hold a radiation-sensitive substrate. In an example, one or more of the tables may hold a sensor to measure radiation from the projection system. In an example, the multi-stage apparatus comprises a first table configured to hold a radiation-sensitive substrate (i.e., a support table) and a second table not configured to hold a radiation-sensitive substrate (referred to hereinafter generally, and without limitation, as a measurement, sensor and/or cleaning table). The second table may comprise and/or may hold one or more objects, other than a radiation-sensitive substrate. Such one or more objects may include one or more selected from the following: a sensor to measure radiation from the projection system, one or more alignment marks, and/or a cleaning device (to clean, e.g., the liquid confinement structure).

In operation, the radiation beam B is incident on the pattern (design layout) present on patterning device (e.g., mask) MA, which is held on the patterning device support structure (e.g., mask table) T, and is patterned by the patterning device MA. Having traversed the patterning device MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor PMS (e.g. an interferometric device, linear encoder, <NUM>-D encoder or capacitive sensor), the substrate table WT can be moved accurately, e.g. so as to position different target portions C in the path of the radiation beam B at a focused and aligned position. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in <FIG>) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B. Patterning device MA and substrate W may be aligned using patterning device alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2 as illustrated occupy dedicated target portions C, they may be located in spaces between target portions C (these are known as scribe-lane alignment marks).

The substrate table WT comprises a substrate holder <NUM>. <FIG> depicts a substrate holder <NUM> for use in the lithographic apparatus LA according to an embodiment. The substrate holder <NUM> is for supporting the substrate W. The substrate holder <NUM> comprises a main body <NUM>. The main body <NUM> has a main body surface <NUM>. A plurality of burls <NUM> are provided projecting from the main body surface <NUM>. The distal end surface of each burl <NUM> engages with the substrate W. The distal end surfaces of the burls <NUM> are coplanar, i.e. the distal end surfaces of the burls <NUM> substantially conform to a support plane SP and support the substrate W. The main body <NUM> may be formed of a ceramic, for example SiC or SiSiC. The burls <NUM> may be formed of the same material as the main body <NUM>, or may be formed of a different material.

Burls <NUM> may have a height in the range of from <NUM> to <NUM>, e.g. about <NUM>. The diameter of the distal end surface of burl <NUM> may be in the range from <NUM> to <NUM>, e.g. about <NUM>. The pitch of the burls <NUM> may be in the range from about <NUM> to <NUM>, e.g. about <NUM>. The pitch of the burls <NUM> is the distance between the centers of two adjacent burls <NUM>. The total area of the distal end surfaces of all the burls <NUM> may be in the range of from <NUM>% to <NUM>% of the total area of the substrate holder <NUM>. Burls <NUM> may be frusto-conical in shape, with burl side surfaces being slightly inclined. Alternatively, the burl side surfaces may be vertical or even overhanging. Burls <NUM> may be circular in plan. Alternatively, burls <NUM> can also be formed in other shapes if desired.

A plurality of through-holes <NUM> may be formed in the main body <NUM>. Through-holes <NUM> allow the e-pins to project through the substrate holder <NUM> to receive the substrate W. Through-holes <NUM> may also allow the space between the substrate W and the substrate holder <NUM> to be evacuated. Evacuation of the space between the substrate W and the substrate holder <NUM> can provide a clamping force, if 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 would be the case in a lithographic apparatus using EUV radiation, electrodes can be provided on the substrate holder <NUM> to form an electrostatic clamp.

Other structures, for example to control gas flow and/or thermal conductivity between the substrate holder <NUM> and the substrate W, can be provided. The substrate holder <NUM> can be provided with electronic components. Electronic components may comprise heaters and sensors. Heaters and sensors may be used to control the temperature of the substrate holder <NUM> and substrate W.

To reduce the wear and the friction of the burls <NUM>, it has been proposed to deposit a layer of DLC on at least the distal end surfaces of the burls <NUM> of the substrate holder <NUM>. However, the inventors have found that such a layer of DLC wears quicker than expected. This can be attributed to the presence of sp2 hybridized carbon in the DLC. Typically, DLC has an sp2:sp3 carbon ratio in the range from <NUM>:<NUM> to <NUM>:<NUM>, and may include trapped hydrogen to form so-called H-DLC or a-C:H. While ta-C comprises carbon only, and so is not hydrogenated, it also contains sp2 carbon in lower concentrations. Sp2 hybridized carbon behaves similarly to graphite, and so is mechanically weak and electrically conducting, and may be subject to contact wear, tribo-charging induced wear and oxidation. This leads to a faster than expected degradation of the DLC, especially in humid environments such as immersion lithographic apparatuses.

It is thus desirable to provide the substrate holder <NUM> with a wear-resistant material that withstands wear better than DLC. The inventors have found that such a wear-resistant material should have a hardness of more than <NUM> GPa, as determined by the Vickers hardness test. A hardness of more than <NUM> GPa ensures that the wear-resistant material is suitable for use on a body such as the substrate holder <NUM> or other support structure (e.g. a support structure comprised by support tables other than the substrate table WT, a substrate clamp, a reticle holder or reticle clamp for holding the patterning device MA) of the lithographic apparatus LA. The wear-resistant material is preferably a crystalline or at least nano-crystalline material, such as diamond, cubic boron nitride (c-BN), cubic silicon nitride (Si<NUM>N<NUM>), cubic carbon nitride (C<NUM>N<NUM>), AlMgB<NUM>, Al<NUM>O<NUM>, WB<NUM>, VyBx, TayBx, ZryBx, NbyBx, c-BC<NUM>N, other C-B-N ternary compounds, or any combination thereof. Alternatively, the wear-resistant material may be, for example, amorphous DLC containing equal to or more than <NUM>% sp3 carbon. Such a sp3 carbon content gives rise to internal mechanical stresses in the DLC, ensuring that the amorphous DLC has a hardness above <NUM> GPa. These materials are especially suitable for use as the wear-resistant material in the lithographic apparatus LA due to their very low wear and friction properties. Growing these materials on a growth substrate using enhanced vapour deposition (CVD, PVD, pulsed laser deposition) requires the growth substrate to be at an elevated temperature from <NUM> to <NUM>. Such a high temperature can lead to damage to the substrate holder <NUM> or other body to which the wear-resistant material is to be applied. Direct deposition of the wear-resistant material on the substrate holder <NUM> thus risks damage to the substrate holder <NUM>.

The inventors have identified a new method of providing the wear-resistant material on a body made of ceramic, glass or glass-ceramic in view of the method as, for example, disclosed in <CIT> and <CIT>. One example of such a body is an unfinished substrate holder <NUM>'. The invention is, however, not limited to applying the wear-resistant material on the unfinished substrate holder <NUM>', thereby creating the substrate holder <NUM> for use in the lithographic apparatus LA. The invention extends to applying the wear-resistant material to any other body made of glass, ceramic or glass-ceramic. Bodies made of glass, ceramic or glass-ceramic can be easily machined using conventional manufacturing methods, and are thus particularly useful to form the base material for components such as those used in the lithographic apparatus LA.

An embodiment of the method <NUM> for providing the wear-resistant material on the body is depicted in <FIG>. The method <NUM> comprises providing the body made of glass, ceramic or glass-ceramic (S210). The body may be made of SiC or SiSiC, for example. The method <NUM> further comprises providing the wear-resistant material having a hardness of more than <NUM> GPa (S220). Examples of the wear-resistant material are diamond (for example as disclosed in <CIT> and <CIT>) and c-BN, as well as the other wear-resistant materials mentioned above. Step S220 may include growing a material layer on a growth substrate (S221) and transferring portions of the material layer to a carrier film (S222), as depicted schematically in <FIG>.

The method <NUM> further comprises providing, between the wear-resistant material and the body, a braze forming material suitable for brazing the wear-resistant material to the body (S230). This may include coating the wear-resistant material and/or the body with the braze forming material (S231) and pressing the wear-resistant material and the body together (S232), as depicted schematically in <FIG>, and in <FIG>. The method <NUM> further comprises brazing the wear-resistant material to the body by heating the braze forming material (S240). This is schematically depicted in <FIG> and <FIG>. In a final step S250 of the method <NUM>, the carrier film may be removed. The composite body obtained by the method <NUM> is depicted schematically in <FIG> and <FIG>.

<FIG> depicts an alternative embodiment of a method <NUM> for providing the wear-resistant material on the body. The method <NUM> comprises providing the body made of glass, ceramic or glass-ceramic (S210) and providing the wear-resistant material having a hardness of more than <NUM> GPa (S220), as already discussed in relation to the method <NUM> of <FIG>. However, compared to the method <NUM> of <FIG>, in the method <NUM> of <FIG> a braze-forming material is not provided between the wear-resistant material and the body. Instead, the wear-resistant material <NUM> is in direct physical contact with the body. The method <NUM> comprises laser welding (or laser-induced welding) the wear-resistant material to the body (S260). This comprises bringing the wear-resistant material into direct physical contact with the body (S261) and exposing the interface between the wear-resistant material and the body using a ps- or fs-pulsed laser. The wear-resistant material and the carrier film may be transparent to the ps- or fs-laser, and the body may be opaque to the ps- or fs-laser. The interface between the wear-resistant material and the body may thus be exposed by the ps- or fs-pulsed laser through the wear-resistant material and the carrier film.

The methods <NUM> and <NUM> can be used to apply the wear-resistant material to the body without relying on growing the wear-resistant material directly on the body (which requires high temperatures), and so reduces the risk of damaging the body. Instead, the wear-resistant material can be grown under optimal conditions and at high temperatures on a growth substrate different from the body, allowing a high-quality wear-resistant material to be obtained. Subsequent brazing or laser welding of the wear-resistant material to the body ensures a strong connection between the body and the wear-resistant material. Such brazing may require lower temperatures that growing the wear-resistant material directly on the body, or may require only localized heating of the braze forming material and surrounding areas, thus reducing the risk of damage to the body compared to a situation in which the entire body is heated to high temperatures to grow the wear-resistant material on the body. Similarly, laser welding requires only highly localized heating of the interface between the wear-resistant layer and the body, thus also reducing the risk of damage.

<FIG> show one embodiment of the method <NUM> for providing the wear-resistant material <NUM> having a hardness of more than <NUM> GPa on the body. In this embodiment, the body is the unfinished substrate holder <NUM>'. The unfinished substrate holder <NUM>' comprises a main body <NUM> having the main body surface <NUM> and a plurality of unfinished burls <NUM>' projecting from the main body surface <NUM>.

As shown in <FIG>, the wear-resistant material <NUM> may be provided in form of a layer, and may thus be a wear-resistant layer. This makes use of the wear-resistant material <NUM> in a support structure (such as the substrate holder <NUM>) simple, as the wear-resistant layer is especially suitable to define a support plane SP for supporting an object without requiring excessive polishing after deposition of the wear-resistant layer on the support structure. The wear-resistant material <NUM> preferably has a thickness in the range from <NUM> to <NUM>.

The wear-resistant material <NUM> may be provided in a plurality of separated portions <NUM>'. It is desirable for the separated portions <NUM>' to have a diameter di or average lateral dimension, when viewed in plan, of less than <NUM>, or preferably less than <NUM>.

Providing the wear-resistant material <NUM> in a plurality of separated portions <NUM>' allows the wear-resistant material <NUM> to be provided on the distal end surfaces of the unfinished burls <NUM>' of the unfinished substrate holder <NUM>' (as in <FIG>). In this case, the wear-resistant material <NUM> preferably has a thickness ti (in a direction perpendicular to the main body surface <NUM>) from <NUM> to <NUM>. The pattern formed by the wear-resistant material <NUM>, and in particular by the separated portions <NUM>' of the wear-resistant material <NUM>, is preferably geometrically similar or identical to the pattern formed by the plurality of unfinished burls <NUM>'. Alternatively, the pattern formed by the (separated portions <NUM>' of the) wear-resistant material <NUM> may be geometrically similar or identical to the pattern formed by a subset of the plurality of unfinished burls <NUM>', for example every second or every third unfinished burl <NUM>'. This allows application of the wear-resistant material <NUM> to the plurality of unfinished burls <NUM>' in two or more stages, such that for example the first half of the unfinished burls <NUM>' is provided with the wear-resistant material <NUM> in a first stage and the second half of the unfinished burls <NUM>' is provided with the wear-resistant material <NUM> in a second stage. The diameter d<NUM> of each of the separated portions <NUM>' may be equal to or less than the diameter of the unfinished burls <NUM>', and for example be in the range from <NUM> to <NUM>, e.g. about <NUM>. The distance between the centers of two adjacent separated portions <NUM>' may be equal to the pitch of the unfinished burls <NUM>', and for example be about <NUM> to <NUM>, e.g. about <NUM>. The shape of the separated portions <NUM>' may be geometrically similar to the shape of the distal end surfaces of the unfinished burls <NUM>', and for example be circular in plan. The separated portions <NUM>' can also be formed in other shapes if desired.

As shown in <FIG>, providing the wear-resistant material <NUM> preferably comprises providing the wear-resistant material <NUM> on a carrier film <NUM>. This allows simple and accurate placement of the wear-resistant material on the body. When the wear-resistant material is provided in a plurality of separated portions <NUM>', the carrier film <NUM> also serves to define the relative position of the separated portions <NUM>' to each other and to the body to which the separated portions <NUM>' are to be applied. The carrier film <NUM> is preferably substantially flat. The carrier film <NUM> may be transparent, for example to a brazing laser used for brazing or a ps- or fs-pulsed laser used for laser welding. Preferably, the carrier film <NUM> is stiff compared to the wear-resistant material <NUM> and flexible compared to the body. Providing a carrier film <NUM> that is stiff compared to the wear-resistant material <NUM> ensures that good contact can be achieved between each of the separated portions <NUM>' of the wear-resistant material <NUM> and the body when placing the wear-resistant material <NUM> on the body. Optionally, an adhesive layer (not shown) may be provided between the wear-resistant material <NUM> and the carrier film <NUM> to stabilize the wear-resistant material <NUM> or the separated portions <NUM>' of the wear-resistant material <NUM> on the carrier film <NUM>. The adhesive properties of the adhesive layer may be reversible, for example by heating the adhesive layer, to allow detachment of the carrier film <NUM> from the wear-resistant material <NUM> when desired (e.g. after the step S240 of brazing). The adhesive layer may be transparent, to allow a laser to pass through the adhesive layer.

<FIG> schematically depict the step S220 of providing, between the wear-resistant material <NUM> and the body (which is the unfinished substrate holder <NUM>'), the braze forming material <NUM>. The braze forming material <NUM> is suitable for brazing the wear-resistant material <NUM> to the unfinished substrate holder <NUM>', i.e. the braze forming material <NUM> chemically reacts with the wear-resistant material <NUM> and the unfinished substrate holder <NUM>' upon heating so as to form an intermediate brazing layer <NUM>, <NUM> connecting the wear-resistant material <NUM> to the unfinished substrate holder <NUM>'. For example, when the unfinished substrate holder <NUM>' is made of SiC or SiSiC, the braze forming material <NUM> may form carbides or silicides with the SiC or SiSiC of the unfinished substrate holder <NUM>'. When the wear-resistant material <NUM> is made of diamond, the braze forming material <NUM> may also form carbides with the diamond.

The braze forming material <NUM> may be selected from the group of braze forming materials <NUM> consisting of Ti, Zr, Mo, Cr, Nb, V, Ta, Ni, Fe, Co, Al, Ag, Au, C, Si, B and combinations thereof. The choice of a suitable braze forming material <NUM> will depend on the specific wear-resistant material and on the specific glass, ceramic or glass-ceramic making up the body. For example, when the body is made of SiC or SiSiC and the wear-resistant material is diamond, the braze forming material <NUM> is preferably selected from the group of braze forming materials <NUM> consisting of Ti, Zr, Mo, Cr, Nb, V, Ta, C, Si and B, and combinations thereof. For example, the braze forming material <NUM> may be Ag-Cu-Ti. When the body is made of SiC or SiSiC and the wear-resistant material is c-BN, the braze forming material <NUM> is preferably selected from the group of braze forming materials <NUM> consisting of Mo, Ni, Fe, Co, Al, Si, Ti and Zr, and combinations thereof.

As shown in <FIG>, the step S230 of providing the braze forming material <NUM> may comprise the step S231 of coating the unfinished substrate holder <NUM>', and in particular at least the portions of the body to which the wear-resistant material is to be provided (such as the distal end surfaces of the unfinished burls <NUM>'), with the braze forming material <NUM>. Alternatively or additionally, at least the surface of the wear-resistant material <NUM> that is to be connected to the body may be coated with the braze forming material <NUM>. In an embodiment, the side of the carrier film <NUM> on which the wear-resistant material <NUM> is provided is also coated with the braze forming material <NUM>, avoiding the need for masking and making provision of the braze forming material <NUM> simpler. The thickness of the braze forming material <NUM> is preferably less than, more preferably less than half, of the thickness ti of the wear-resistant material <NUM>. This ensures that, after brazing, the desirable chemical and structural properties of the surface of the wear-resistant material <NUM> facing away from the unfinished substrate holder <NUM>' are preserved optimally.

As shown in <FIG>, the step S230 of providing the braze forming material <NUM> may further comprise the step S232 of pressing the body (i.e. the substrate holder <NUM>) and the wear-resistant material <NUM> (or the separated portions <NUM>' of the wear-resistant material <NUM>) together such that the braze forming material <NUM> is located between the body and the wear-resistant material <NUM>. When the braze forming material <NUM> is coated on the unfinished substrate holder <NUM>' as shown in <FIG>, the wear-resistant material <NUM> is pressed into the braze forming material <NUM>. Alternatively, when the braze forming material <NUM> is coated on the wear-resistant material <NUM>, the unfinished substrate holder <NUM>' (and in particular the plurality of unfinished burls <NUM>' of the unfinished substrate holder <NUM>') is pressed into the braze forming material <NUM>. The unfinished substrate holder <NUM>' and the wear-resistant material <NUM> are pressed together to ensure appropriate wetting by contact of the unfinished substrate holder <NUM>' and the separated portions <NUM>' of the wear-resistant material <NUM> with the braze forming material <NUM>.

<FIG> also schematically shows the step S240 of brazing the wear-resistant material <NUM> to the body by heating the braze forming material <NUM>. The braze forming material <NUM> may be heated, for example, to a temperature in the range from <NUM> to <NUM>. Alternatively, the braze forming material <NUM> may be heated to higher temperatures, for example when using <NUM> to <NUM> ns laser irradiation heating while providing a relatively cold body. When the braze forming material <NUM> is heated, the braze forming material <NUM> may chemically bind with and/or diffuse into the body and/or wear-resistant material <NUM>, thus forming an intermediate brazing layer <NUM>, <NUM>. As shown in <FIG>, the intermediate brazing layer <NUM>,<NUM> may comprise or consist of a first portion <NUM> formed by the braze forming material <NUM> diffusing into the wear-resistant material <NUM>, and a second portion <NUM> formed by the braze forming material <NUM> diffusing into the unfinished substrate holder <NUM>' or other body.

The portions of the braze forming material <NUM> that serve to connect the wear-resistant material <NUM> to the body are preferably heated locally, i.e. only these portions of the braze forming material <NUM> and the regions of the body and wear-resistant material <NUM> adjacent to these portions of the braze forming material <NUM> are heated. The unfinished substrate holder <NUM>' may be not heated entirely, thus reducing the risk of damage to the unfinished substrate holder <NUM>'.

Preferably, the braze forming material <NUM> is heated by a brazing laser <NUM>, thus laser-brazing the portion of the braze forming material <NUM> located between the wear-resistant material and the body. This is shown in <FIG>. The brazing laser <NUM> may illuminate and heat the braze forming material <NUM> through the carrier film <NUM> and the wear-resistant material <NUM> (for example when the wear-resistant material <NUM> is transparent, such as a diamond layer). Alternatively or additionally, the brazing laser <NUM> may illuminate and heat the braze forming material <NUM> through the body (not shown). The brazing laser <NUM> may illuminate the portion of the braze forming material <NUM> in one or multiple laser pulses. The wavelength of the brazing laser <NUM> may be chosen such that less than <NUM>%, preferably less than <NUM>%, of the power of the brazing laser <NUM> is absorbed in the wear-resistant material <NUM> (when the laser beam is transmitted through the wear-resistant material) or the body (when the laser beam is transmitted through the body). This ensures that most of the power of the brazing laser <NUM> is absorbed by the braze forming material. Typically, each laser pulse may have a duration from <NUM> to <NUM> ns and a fluence in the range from <NUM> to <NUM> J/cm<NUM>. Alternatively, each laser pulse may have a duration of less than <NUM> ns, with a reduced fluence in the range from <NUM> to <NUM> J/cm<NUM>. Using a brazing laser <NUM> allows rapid heating of the portion of the braze forming material <NUM> that is illuminated, reducing the heating impact on the area surrounding the illuminated portion and thus reducing the risk of damage to the unfinished substrate holder <NUM>'.

The brazing laser <NUM> may also be used to heat the wear-resistant material, for example when the wear-resistant material is c-BN (which is unstable at temperatures exceeding <NUM>). This heats the braze forming material through conductive heat transfer, because the wear-resistant material is in physical contact with the braze forming material <NUM>, thus brazing the wear-resistant material to the body.

Heating devices other than the brazing laser <NUM> may also be used to locally heat the braze forming material <NUM>. For example, the braze forming material <NUM> could be heated locally through conductive heat transfer by directly contacting the braze forming material <NUM> with a heating device (for example, by heating of the carrier film <NUM> and contact heating of the separated portions <NUM>' of the wear-resistant material <NUM>). Alternatively, for braze forming materials <NUM> that can chemically react with and/or diffuse into the unfinished substrate holder <NUM>' and the wear-resistant material <NUM> at temperatures below <NUM>, the entire unfinished substrate holder <NUM>' may be heated. This is because the unfinished substrate holder <NUM>' can withstand such low temperatures.

After the step S240 of brazing, the carrier film <NUM> may be separated from the wear-resistant material <NUM>. If the carrier film <NUM> is provided with the optional adhesive layer, this adhesive layer can be heated to facilitate separation of the wear-resistant material <NUM> from the carrier film <NUM>. Excessive braze forming material <NUM>, such as the braze forming material <NUM> provided on portions of the unfinished substrate holder <NUM>' that are not provided with the wear-resistant material <NUM>, may be removed. After brazing, the surface of the wear-resistant material <NUM> facing away from the unfinished substrate holder <NUM>' defines a support plane SP for supporting a planar surface of an object (such as the substrate W) that is to be supported. Optionally, the wear-resistant material <NUM> may be polished and planarized after brazing to ensure that the support plane SP defined by the wear-resistant material <NUM> meets the specifications required for use in the lithographic apparatus LA.

<FIG> shows the final composite body that is obtained by the method <NUM> depicted in <FIG>. The final composite body is the substrate holder <NUM>. The unfinished burls <NUM>' in combination with the intermediate brazing layer <NUM>,<NUM> and the wear-resistant material <NUM> make up the burls <NUM> of the substrate holder <NUM>.

<FIG> show another embodiment of the method <NUM> for providing the wear-resistant material on the body. This embodiment differs from the embodiment of <FIG> in that the wear-resistant material <NUM> is not provided on the pre-fabricated unfinished burls <NUM>' of the unfinished substrate holder <NUM>'. Instead, the wear-resistant material <NUM> forms the plurality of burls <NUM> projecting from the main body surface <NUM> of the main body <NUM> of a substrate holder blank or template.

In the embodiment of <FIG>, the body made of glass, ceramic or glass-ceramic is the substrate holder blank. The substrate holder blank may be made of SiC or SiSiC. The substrate holder blank comprises the main body <NUM> having the main body surface <NUM>. The main body surface <NUM> is substantially planar. The substrate holder blank does not comprise the plurality of burls <NUM>.

In the embodiment of <FIG>, the step S220 of providing the wear-resistant material is as described in relation to <FIG>. Providing the wear-resistant material <NUM> in a plurality of separated regions <NUM>' allows the wear-resistant material <NUM> to form the plurality of burls <NUM> on the substrate holder blank, thereby forming the substrate holder <NUM>. When the wear-resistant material <NUM> is used to form the plurality of burls <NUM>, the wear-resistant material <NUM> has a thickness t<NUM> (in a direction perpendicular to the main body surface <NUM>) that is equal to the height h<NUM> of the desired burls <NUM>, preferably from <NUM> to <NUM>. The diameter d<NUM> of the separated regions <NUM>' may be in the range from <NUM> to <NUM>, e.g. about <NUM>. The distance between the centers of two adjacent separated regions <NUM>' may be about <NUM> to <NUM>, e.g. about <NUM>. The shape of the separated regions <NUM>' may be circular in plan, so as to form circular burls <NUM>. The separated regions <NUM>' can also be formed in other shapes if desired.

In the embodiment of <FIG>, the braze forming material <NUM> is as described in relation to <FIG>. The entire main body surface <NUM> of the substrate holder blank, or at least the portions of the main body surface <NUM> to which the wear-resistant material <NUM> is to be applied, are coated with the braze forming material <NUM>. Alternatively or additionally, the surface of the wear-resistant material <NUM> that is to be connected to the substrate holder blank may be coated with the braze forming material <NUM>. The braze forming material <NUM> is then (locally) heated so as to form an intermediate brazing layer <NUM>,<NUM> connecting the wear-resistant material <NUM> to the substrate holder blank, for example in the manner already described in relation to <FIG>. The carrier film <NUM> and excessive braze forming material <NUM> may be removed, and optionally the braze forming material <NUM> may be polished and planarized, so as to form the composite body depicted in <FIG>.

<FIG> shows the final composite body that is obtained by the method <NUM> depicted in <FIG>. The final composite body is the substrate holder <NUM>. The first portion <NUM> of the intermediate brazing layer and the wear-resistant material <NUM> make up the burls <NUM> of the substrate holder <NUM>.

<FIG> and <FIG> schematically depict the steps of the method <NUM> of <FIG> for providing the wear-resistant material on the body. The method <NUM> of <FIG> may be carried out as described in relation to <FIG> and <FIG>, with the exception that no braze forming material <NUM> is provided between the wear-resistant material <NUM> and the body. Instead of the braze forming laser <NUM>, a ps- or fs-pulsed laser may be used to laser weld the wear-resistant material <NUM>, or each separated portion <NUM>' of the wear-resistant material <NUM>, to the body. Preferably, the wear-resistant material <NUM> is transparent (to the ps- or fs-pulsed laser) and the body is opaque (to the ps- or fs-pulsed laser), and the ps- or fs-pulsed laser exposes the interface between the body and the wear-resistant material <NUM> through the wear- resistant material <NUM>. The ps- or fs-pulsed laser may emit laser pulses having a duration of less than <NUM> ps, preferably less than <NUM> ps. Each laser pulse may have a fluence at its focus of more than <NUM> J/cm<NUM>, preferably <NUM> to <NUM> J/cm<NUM>. The ps- or fs-pulsed laser may be focused on at least a portion of the interface between each separated region <NUM>' of wear-resistant material <NUM> and the body, achieving highly localized heating to temperatures exceeding <NUM> at this interface. Such highly localized heating leads to diffusion of the wear-resistant material <NUM> into the glass, ceramic, or glass-ceramic material of the body, and/or vice versa. This creates an interdiffusion layer connecting the wear-resistant material <NUM> to the body, and results in a strong bond between the wear-resistant material <NUM> and the body.

The method <NUM> may be used to obtain the composite body according to an embodiment of the invention. <FIG> and <FIG> schematically depict two embodiments of such a composite body. In the embodiments of <FIG> and <FIG>, the composite body is the substrate holder <NUM> for use in the lithographic apparatus LA. Alternatively, the composite body may be any other support structure, such as the reticle clamp or reticle holder for use in the lithographic apparatus LA, a substrate clamp or any other support table for use in the lithographic apparatus LA. The composite body may also be a support structure for use in applications other than the lithographic apparatus LA, for example in a metrology apparatus or other substrate processing device. The composite body may also not be for the purpose of supporting an object, but for any other application that benefits from applying a highly wear-resistant material to a glass, ceramic or glass-ceramic body.

The composite body comprises the body made of glass, ceramic or glass-ceramic, such as the unfinished substrate holder <NUM>' (as in <FIG>), the substrate holder blank (as in <FIG>), a reticle clamp blank, or any other support structure blank. The composite body also comprises the wear-resistant material <NUM>, for example in form of a wear-resistant layer, having a hardness of more than <NUM> GPa. The composite body further comprises the intermediate brazing layer <NUM>, <NUM>. The intermediate brazing layer <NUM>, <NUM> connects the body and the wear-resistant material by brazing. The intermediate brazing layer <NUM>, <NUM> may comprise the braze forming material <NUM> that is diffused into the body and into the wear-resistant material. The intermediate brazing layer <NUM>, <NUM> can readily be detected when inspecting the composite body using focused ion beam (FIB) systems in transmission electron microscopes (TEM), Raman spectroscopy, or through visual inspection using an optical microscope.

The composite body may thus be used as a substrate holder <NUM> or other support structure in the lithographic apparatus LA or in other applications. If the intermediate brazing layer <NUM>, <NUM> of the composite body fatigues, for example after a predetermined number of load/unload cycles of the substrate W, mask MA or other object from the composite body, the intermediate brazing layer <NUM>, <NUM> can be repaired. This can be achieved by heating the intermediate brazing layer <NUM>, <NUM>. Such heating may be done using the brazing laser <NUM> using similar or lower irradiation compared to the original brazing step.

Method <NUM> can be used to obtain a composite body according to an alternative embodiment of the invention. This composite body may be as described above, with the exception that an interdiffusion layer is provided instead of the intermediate brazing layer <NUM>, <NUM>. The interdiffusion layer is formed by laser welding the wear-resistant material <NUM> to the body. The interdiffusion layer comprises a gradient in (elemental) composition from the glass, ceramic, or glass-ceramic material of the body to the wear-resistant material. The interdiffusion layer can be detected and/or repaired in the same way as the intermediate brazing layer <NUM>, <NUM>.

<FIG> schematically depict a preferable embodiment of the step S220 of providing the wear-resistant material. Step S220 preferably comprises growing a layer of material <NUM> having a hardness of more than <NUM> GPa, such as a layer of diamond, c-BN, C<NUM>N<NUM>, Si<NUM>N<NUM>, AlMgB<NUM>, Al<NUM>O<NUM>, WB<NUM>, VyBx, TayBx, ZryBx, NbyBx, c-BC<NUM>N, other C-B-N ternary compounds, or any combination thereof on a growth substrate <NUM> (S221). The growth substrate may, for example, be made of mono- or polycrystalline SiC, Si or sapphire. The layer of material <NUM> may be grown under optimal conditions, for example using enhanced vapour deposition at a growth substrate temperature from <NUM> to <NUM>. The optimal growth conditions will depend on the material to be grown. Other methods to grow or produce crystalline, hard films, such as high pressure, high temperature sintering/hot pressing, may also be used to provide the layer of material <NUM>. At least portions of the layer of material <NUM> may then be transferred from the growth substrate <NUM> to the carrier film <NUM> (S222), thereby forming the wear-resistant material <NUM> on the carrier film <NUM>. The portions of the layer of material <NUM> that are transferred to the carrier film <NUM> correspond to the separated portions <NUM>' of the wear-resistant material <NUM> that is to be applied to the body. The pattern of the portions of the layer of material <NUM> that are transferred is thus equal to the pattern of the wear-resistant material <NUM> that is to be applied to the body.

As shown in <FIG>, laser induced delamination may be used to transfer the portions of the layer of material <NUM> to the carrier film. A delamination laser <NUM> may illuminate the portions of the layer of material <NUM> that are to be transferred, for example using a femtosecond (fs) pulsed laser beam. The delamination laser <NUM> may emit laser pulses having a duration of less than <NUM> fs, preferable less than <NUM> fs. The fluence of these laser pulses may be greater than <NUM> J/cm<NUM>, preferably greater than <NUM> J/cm<NUM>. This causes ablation in the illuminated region at the interface between the growth substrate <NUM> and the layer of material <NUM>, such that the portion of the layer of material <NUM> is delaminated and sent towards the carrier film <NUM> or the optional adhesive layer on the carrier film <NUM>. The optional adhesive layer has the added benefit of reducing the risk of the delaminated portion bouncing off the carrier film <NUM> instead of adhering to the carrier film <NUM>.

The delamination laser <NUM> may illuminate the portions of the layer of material <NUM> through the carrier film <NUM> (as shown in <FIG>), for a so-called backward transfer of the portions of the layer of material <NUM> to the carrier film <NUM>. Alternatively, the delamination laser <NUM> may illuminate the portions of the layer of material <NUM> (e.g. c-BN) through the growth substrate <NUM> (as shown in <FIG>), for a so-called forward transfer of the portions of the layer of material <NUM> to the carrier film <NUM>. The transfer step should preferably be performed in low pressure or under vacuum. During the transfer step, the distance H between the carrier film <NUM> and the layer of material <NUM> is preferably less than <NUM>, more preferably less than <NUM>, to ensure accurate positioning of the separated portions <NUM>' on the carrier film <NUM>.

Optionally, prior to laser-induced delamination, the layer of material on the growth substrate <NUM> may be pre-patterned to assist transfer of the portions of the layer of material <NUM> to the carrier film <NUM>. This is schematically depicted in <FIG>. Such pre-patterning is especially useful for the transfer of portions of relatively thick layers of material <NUM>, such as a layer of material <NUM> with a thickness of more than <NUM>. For example, as shown in <FIG>, the portions of the layer of material <NUM> surrounding the portions to be transferred, or the entire part of the layer of material <NUM> that is not to be transferred, may be etched prior to laser-induced delamination. This ensures a delamination process that is more precise and leads to less damaged transferred portions. Alternatively, as shown in <FIG>, laser induced delamination may be used in a first step to delaminate and remove the portions of the layer of material <NUM> surrounding the portions to be transferred. The portions to be transferred can then be delaminated and transferred to the carrier film <NUM> in a second step using laser-induced delamination.

The present invention is not limited to providing the wear-resistant material on a carrier film <NUM> using the laser-induced delamination process of <FIG>. Instead of growing the layer of material <NUM> and then transferring portions of this layer of material <NUM> to the carrier film <NUM> to create the wear-resistant material, the wear-resistant material may be grown in a plurality of separated portions <NUM>', for example using a mask during enhanced vapour deposition on the growth substrate <NUM>. The wear-resistant material may also be grown directly on the carrier film <NUM>, or be transferred directly from the growth substrate <NUM> to the body.

Claim 1:
A method for providing a wear-resistant material (<NUM>) on a body, the method comprising the steps of:
providing a body made of glass, ceramic or glass-ceramic, wherein the body comprises a main body (<NUM>) having a main body surface (<NUM>) and a plurality of unfinished burls (<NUM>') projecting from the main body surface, each unfinished burl having a distal end surface;
providing a wear-resistant material having a hardness of more than <NUM> GPa;
brazing or laser welding the wear-resistant material to the body; and
characterized in that the wear-resistant material is provided on the distal end surface of each of the plurality of unfinished burls so as to form a support structure comprising a plurality of burls.