Photolithography object stage and method for forming the same

Abstract

An object stage and method thereof having reduced mass for use in photolithography and comprises a support surface that is configured to support an object, a fin network comprising a plurality of fins that provide rigidity to the support surface, and a coating material provided on at least some of the fins to add stiffness to the fins.

Description

PHOTOLITHOGRAPHY OBJECT STAGE AND METHOD FOR FORMING THE SAMECROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Application No. 63 / 531,790, filed August 9, 2023, and which is incorporated herein in its entirety by reference.FIELD

[0002] The present disclosure relates to systems and methods for object stages for use in photolithography.BACKGROUND

[0003] During photolithography exposure, the object stage is subjected to high speeds. During scanning exposure, the reticle stage and the wafer stage are moved synchronously with each other in order to scan the pattern of the reticle onto the wafer. Further, these stages are subject to very fast movements and accelerations to increase wafer throughput. To achieve these movements and acceleration, it is beneficial to have a stage that is light in weight, yet sufficiently strong to serve its purpose. The present disclosure addresses these ends.SUMMARY

[0004] In an embodiment, the present disclosure pertains to an object stage for use in photolithography and comprises a support surface that is configured to support an object, a fin network comprising a plurality of fins that provide rigidity to the support surface, and a coating material provided on at least some of the fins to add stiffness to the fins.

[0005] In an embodiment, the object stage is a reticle stage or a wafer stage.

[0006] In an embodiment, the plurality of fins are made from a SiSiC (siliconized silicon carbide) material.

[0007] In an embodiment, the plurality of fins are made from a glass-ceramic material. In an embodiment, the glass-ceramic material is a lithium-aluminosilicate material.

[0008] In an embodiment, the plurality of fins are made from a cordierite material.

[0009] In an embodiment, the plurality of fins are made from aluminum.

[0010] In an embodiment, the coating material comprises a diamond material.

[0011] In an embodiment, the coating material is provided on only one side of the fins. In an embodiment, the coating material is provided on both sides of the fins.

[0012] In an embodiment, some portions of the fins are thinner than other portions.

[0013] In an embodiment, at least some of the fins have grooves formed therethrough.

[0014] In an embodiment, the support surface and the fin network are formed as a unitary, integral structure.

[0015] In an embodiment, the object stage comprises a mirror block.

[0016] In an embodiment, the thicker portions of the fins have a thickness between 5-15 mm, and wherein the thinner portions of the fins have a thickness between 1-4 mm.

[0017] In an embodiment, a method is described for forming an object stage and comprises providing an object stage initial structure comprising a support surface configured to support an object, and a fin network comprising a plurality of fins that provide rigidity to the support surface, machining at least one side of the fins to reduce a mass of the fins, and coating the fins of reduced mass with a coating material to increase the stiffness of the fins.

[0018] In an embodiment, the coating comprises chemical vapor deposition.

[0019] In an embodiment, the coating material is a diamond material.

[0020] In an embodiment, the plurality of fins are made from a SiSiC (siliconized silicon carbide) material.

[0021] In an embodiment, the plurality of fins are made from a glass-ceramic material.

[0022] In an embodiment, the plurality of fins are made from a cordierite material.

[0023] In an embodiment, the plurality of fins are made from aluminum.

[0024] In an embodiment, the machining comprises reducing a thickness of the fins.

[0025] In an embodiment, the coating is applied to only one side of the fins. In an embodiment, the machining is performed on a side of the fins opposite the one side, after the one side has been coated. In an embodiment, the coating is applied to the opposite side of the fins, after the machining.

[0026] In an embodiment, some portions of the fins are thinner than other portions.

[0027] In an embodiment, at least some of the fins have grooves formed therethrough.

[0028] In an embodiment, the support surface and the fin network are formed as a unitary, integral structure.

[0029] In an embodiment, the object stage comprises a mirror block.

[0030] In an embodiment, the fins have a thickness between 5-15 mm prior to the machining, and wherein the post-machined portions of the fins have a reduced thickness of between 1-4 mm after the machining, although some embodiments of the invention are not limited to these dimensions, as in can be appreciated that other dimensions are also feasible.

[0031] In an embodiment, the machining comprises a CNC milling process.

[0032] In an embodiment, the coating is applied to a thickness of between 1-16 um on any given side of the fins.BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 A is a schematic illustration of a reflective lithographic apparatus, according to an embodiment of the present disclosure.

[0034] FIG. IB is a schematic illustration of a transmissive lithographic apparatus, according to an embodiment of the present disclosure.

[0035] FIG. 1C is a more detailed schematic illustration of the reflective lithographic apparatus, according to an embodiment of the present disclosure.

[0036] FIGS. 2A-2B are schematic illustrations of a reticle stage mirror block.

[0037] FIGS. 3A-3B are schematic illustrations of a top side of a wafer stage mirror block.

[0038] FIGS. 3C-3D are schematic illustrations of a bottom side of a wafer stage mirror block.

[0039] FIG. 4 is a schematic illustration of a fin in a fin network.

[0040] FIG. 5 is a schematic illustration of a machined fin.

[0041] FIGS. 6A-6B are schematic illustrations of a fin with machined grooves.

[0042] FIGS. 7A-7B are schematic illustrations of a fin with a machined hole.DETAILED DESCRIPTION

[0043] In photolithography, a pattern on a reticle is transferred to a wafer in a scanning exposure method. This is accomplished by moving the reticle stage and the wafer stage relative to each other. Once the reticle pattern is exposed onto the wafer surface, the process is repeated over and over until the wafer surface is fully patterned. The object stage, which can be a reticle stage or a wafer stage, includes a mirror block, a stage chuck, an object, drive motors, and more. During exposure, the object stages are accelerated and decelerated rapidly to perform the exposure. The object stages are subjected to substantial g-forces (for example, in the range up to 20 g or greater).

[0044] By increasing the stiffness of the object stages, higher accelerations and machine throughput can be achieved. Such object stages often have a fin network on the back side thereof, providing rigidity to the stage structure. The stiffness can be improved by applying a coating to the fins. By increasing the rigidity of the object stages, they can be subjected to even higher accelerations and thus increase throughput.

[0045] Another application of this technology is bringing lower quality - and hence lower cost - material into stiffness specifications to compete on the lower end of the market. For example, a lower end material such as aluminum can be machined and then coated to satisfy the stiffness requirements of the object stage fins.

[0046] Furthermore, it is possible to decrease the force required to drive an object stage. One way to achieve this would be to decrease the weight of the object stage.

[0047] In one embodiment of the present disclosure, the weight of the stage can be made lighter than otherwise possible by using less material for the fin network, while maintaining its structural integrity by use of a structural coating provided on at least some of the fins. In one embodiment, the fins are originally formed to be thin and then coated with the coating. In another embodiment, the fins are made with a mass or thickness that can be reduced (e.g., though machining) prior to application of the coating.

[0048] Example Reflective and Transmissive Lithographic Systems

[0049] FIGS. 1A and IB are schematic illustrations of a lithographic apparatus 100 and lithographic apparatus 100’, in or for which embodiments of the present disclosure may be implemented. Lithographic apparatus 100 and lithographic apparatus 100’ each include the following: an illumination system (illuminator) IL configured to condition a radiation beam B (for example, deep ultra violet or extreme ultra violet radiation); a support structure (for example, a mask table) MT configured to support a patterning device (for example, a mask, a reticle, or a dynamic patterning device) MA and connected to a first positioner PM configured to accurately position the patterning device MA; and, a substrate table (for example, a wafer table) WT configured to hold a substrate (for example, a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. Lithographic apparatus 100 and 100’ also have a projection system PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion (for example, comprising one or more dies) C of the substrate W. In lithographic apparatus 100, the patterning device MA and the projection system PS are reflective. In lithographic apparatus 100’, the patterning device MA and the projection system PS are transmissive.

[0050] The illumination system IL may include various types of optical components, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for directing, shaping, or controlling the radiation beam B.

[0051] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA with respect to a reference frame, the design of at least one of the lithographic apparatus 100 and 100’, and other conditions, such as whether or not the patterning device MA is held in a vacuum environment. The support structure MT may use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT can be a frame or a table, for example, which can be fixed or movable, as required. By using sensors, the support structure MT can ensure that the patterning device MA is at a desired position, for example, with respect to the projection system PS.

[0052] The term “patterning device” MA should be broadly interpreted as referring to any device that can be used to impart a radiation beam B with a pattern in its cross-section, such as to create a pattern in the target portion C of the substrate W. The pattern imparted to the radiation beam B can correspond to a particular functional layer in a device being created in the target portion C to form an integrated circuit.

[0053] The patterning device MA may be transmissive (as in lithographic apparatus 100’ of FIG. IB) or reflective (as in lithographic apparatus 100 of FIG. 1A). Examples of patterning devices MA include reticles, masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary, alternating phase shift, and attenuated phase shift, as well as various hybrid mask types. An example of a programmable mirror array employs a matrix arrangement of small mirrors, each of which can be individually tilted so as toreflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in the radiation beam B which is reflected by a matrix of small mirrors.

[0054] The term “projection system” PS can encompass any type of projection system, including refractive, reflective, catadioptric, magnetic, electromagnetic and electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, or for other factors, such as the use of an immersion liquid on the substrate W or the use of a vacuum. A vacuum environment can be used for EUV or electron beam radiation since other gases can absorb too much radiation or electrons. A vacuum environment can therefore be provided to the whole beam path with the aid of a vacuum wall and vacuum pumps.

[0055] Lithographic apparatus 100 and / or lithographic apparatus 100’ can be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such “multiple stage” machines, the additional substrate tables WT can be used in parallel, or preparatory steps can be carried out on one or more tables while one or more other substrate tables WT are being used for exposure. In some situations, the additional table may not be a substrate table WT.

[0056] Referring to FIGS. 1 A and IB, the illuminator IL receives a radiation beam from a radiation source SO. The source SO and the lithographic apparatus 100, 100’ can be separate physical entities, for example, when the source SO is an excimer laser. In such cases, the source SO is not considered to form part of the lithographic apparatus 100 or 100’ , and the radiation beam B passes from the source SO to the illuminator IL with the aid of a beam delivery system BD (in FIG. IB) including, for example, suitable directing mirrors and / or a beam expander. In other cases, the source SO can be an integral part of the lithographic apparatus 100, 100’ — for example when the source SO is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD, if required, can be referred to as a radiation system.

[0057] The illuminator IL can include an adjuster AD (in FIG. IB) for adjusting the angular intensity distribution of the radiation beam. Generally, at least the outer and / or inner radial extent (commonly referred to as “o-outer” and “o-inner,” respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. In addition, the illuminator IL can comprise various other components (in FIG. IB), such as an integrator IN and a condenser CO. The illuminator IL can be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross section.

[0058] Referring to FIG. 1 A, the radiation beam B is incident on the patterning device (for example, mask) MA, which is held on the support structure (for example, mask table) MT, and is patterned by the patterning device MA. In lithographic apparatus 100, the radiation beam B is reflected from the patterning device (for example, mask) MA. After being reflected from the patterning device (for example, mask) MA, the radiation beam B passes through the projection system PS, which focuses the radiation beam B onto a target portion C of the substrate W. With the aid of the second positioner PW and position sensor IF2 (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT can be moved accurately (for example, so as to position differenttarget portions C in the path of the radiation beam B). Similarly, the first positioner PM and another position sensor IF1 (for example, an interferometric device, linear encoder, or capacitive sensor) can be used to accurately position the patterning device (for example, mask) MA with respect to the path of the radiation beam B. Patterning device (for example, mask) MA and substrate W can be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2.

[0059] Referring to FIG. IB, the radiation beam B is incident on the patterning device (for example, mask MA), which is held on the support structure (for example, mask table MT), and is patterned by the patterning device. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil PPU conjugate to an illumination system pupil IPU. Portions of radiation emanate from the intensity distribution at the illumination system pupil IPU and traverse a mask pattern without being affected by diffraction at a mask pattern and create an image of the intensity distribution at the illumination system pupil IPU.

[0060] With the aid of the second positioner PW and position sensor IF2 (for example, an interferometric device, linear encoder, or capacitive sensor), the substrate table WT can be moved accurately (for example, so as to position different target portions C in the path of the radiation beam B). The position sensor IF2 measures the substrate table WT in three dimensions. In this example, the position sensor IF2 is an interferometric device. The z-direction interferometers are positioned to the side of the substrate table WT. The interferometric mirrors have 45-degree angled surfaces attached to the left and the right side of the substrate table WT. The interferometric lasers are mounted such that the laser light is incident upon the interferometric mirrors. FIG. IB shows the relationship between the interferometric lasers and the mirrors of the position sensor IF2. Similarly, the first positioner PM and another position sensor IF1 (shown in FIG. 1 A) can be used to accurately position the mask MA with respect to the path of the radiation beam B (for example, after mechanical retrieval from a mask library or during a scan). The position sensor IF1 measures the mask table MT in three dimensions. In this example, the position sensor IF1 is an interferometric device. The z- direction interferometers are positioned to the side of the mask table MT. The interferometric mirrors have 45-degree angled surfaces attached to the left and the right side of the mask table MT. The interferometric lasers are mounted such that the laser light is incident upon the interferometric mirrors.

[0061] In general, movement of the mask table MT can be realized with the aid of a long-stroke module (coarse positioning) and a short-stroke module (fine positioning), which form part of the first positioner PM. Similarly, movement of the substrate table WT can be realized using a long-stroke module and a short-stroke module, which form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the mask table MT can be connected to a short-stroke actuator only or can be fixed. Mask MA and substrate W can be aligned using mask alignment marks Ml, M2, and substrate alignment marks Pl, P2. Although the substrate alignment marks (as illustrated) occupydedicated target portions, they can be located in spaces between target portions (known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the mask MA, the mask alignment marks can be located between the dies.

[0062] Mask table MT and patterning device MA can be in a vacuum chamber, where an in-vacuum robot IVR can be used to move patterning devices such as a mask in and out of vacuum chamber. Alternatively, when mask table MT and patterning device MA are outside of the vacuum chamber, an out-of- vacuum robot can be used for various transportation operations, similar to the in- vacuum robot IVR. Both the in-vacuum and out-of- vacuum robots need to be calibrated for a smooth transfer of any payload (e.g., mask) to a fixed kinematic mount of a transfer station.

[0063] The lithographic apparatus 100 and 100’ can be used in at least one of the following modes:

[0064] 1. In step mode, the support structure (for example, mask table) MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam B is projected onto a target portion C at one time (i.e., a single static exposure). The substrate table WT is then shifted in the X and / or Y direction so that a different target portion C can be exposed.

[0065] 2. In scan mode, the support structure (for example, mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam B is projected onto a target portion C (i.e., a single dynamic exposure). The velocity and direction of the substrate table WT relative to the support structure (for example, mask table) MT can be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0066] 3. In another mode, the support structure (for example, mask table) MT is kept substantially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam B is projected onto a target portion C. A pulsed radiation source SO can be employed and the programmable patterning device is updated as required after each movement of the substrate table WT or in between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes a programmable patterning device, such as a programmable mirror array.

[0067] Combinations and / or variations on the described modes of use or entirely different modes of use can also be employed.

[0068] In some embodiments, lithographic apparatus 100 includes an extreme ultraviolet (EUV) source, which is configured to generate a beam of EUV radiation for EUV lithography. In general, the EUV source is configured in a radiation system, and a corresponding illumination system is configured to condition the EUV radiation beam of the EUV source.

[0069] FIG. 1C shows the lithographic apparatus 100 in more detail, including the source collector apparatus SO, the illumination system IL, and the projection system PS. The source collector apparatus SO is constructed and arranged such that a vacuum environment can be maintained in an enclosing structure 120 of the source collector apparatus SO. An EUV radiation emitting plasma 110 may be formed by a discharge produced plasma source. EUV radiation may be produced by a gas orvapor, for example Xe gas, Li vapor or Sn vapor in which the hot plasma 110 is created to emit radiation in the EUV range of the electromagnetic spectrum. The hot plasma 110 is created by, for example, an electrical discharge causing an at least partially ionized plasma. Partial pressures of, for example, 10 Pa of Xe, Li, Sn vapor or any other suitable gas or vapor may be required for efficient generation of the radiation. In an embodiment, a plasma of excited tin (Sn) is provided to produce EUV radiation.

[0070] The radiation emitted by the hot plasma 110 is passed from a source chamber 111 into a collector chamber 112 via an optional gas barrier or contaminant trap 113 (in some cases also referred to as contaminant barrier or foil trap) which is positioned in or behind an opening in source chamber 111. The contaminant trap 113 may include a channel structure. Contamination trap 113 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap 113 further indicated herein at least includes a channel structure, as known in the art.

[0071] The collector chamber 112 may include a radiation collector CO which may be a so-called grazing incidence collector. Radiation collector CO has an upstream radiation collector side 151 and a downstream radiation collector side 152. Radiation that traverses collector CO can be reflected off a grating spectral filter 140 to be focused in a virtual source point IFP. The virtual source point IFP is commonly referred to as the intermediate focus, and the source collector apparatus is arranged such that the intermediate focus IFP is located at or near an opening 119 in the enclosing structure 120. The virtual source point IFP is an image of the radiation emitting plasma 110. Grating spectral filter 140 is used in particular for suppressing infra-red (IR) radiation.

[0072] Subsequently the radiation traverses the illumination system IL, which may include a facetted field mirror device 122 and a facetted pupil mirror device 124 arranged to provide a desired angular distribution of the radiation beam 121, at the patterning device MA, as well as a desired uniformity of radiation intensity at the patterning device MA. Upon reflection of the radiation beam 121 at the patterning device MA, held by the support structure MT, a patterned beam 126 is formed and the patterned beam 126 is imaged by the projection system PS via reflective elements 128, 130 onto a substrate W held by the wafer stage or substrate table WT.

[0073] More elements than shown may generally be present in illumination optics unit IL and projection system PS. The grating spectral filter 140 may optionally be present, depending upon the type of lithographic apparatus. Further, there may be more mirrors present than those shown in the FIGS., for example there may be 1-6 additional reflective elements present in the projection system PS than shown in FIG. 1C.

[0074] Collector optic CO, as illustrated in FIG. 1C, is depicted as a nested collector with grazing incidence reflectors 153, 154 and 155, just as an example of a collector (or collector mirror). The grazing incidence reflectors 153, 154 and 155 are disposed axially symmetric around an optical axis O and a collector optic CO of this type is preferably used in combination with a discharge produced plasma source, often called a DPP source.

[0075] Object Stages

[0076] Next, the object stages will be described. The object stage can be the reticle stage (or mask table) MT and / or the wafer stage (or substrate table) WT. Either of these stages, or both of them, may have a fin network to add rigidity to the stage. The fin networks is located on a side thereof that does not carry the object (i.e., the reticle or wafer), e.g., the back side. In one embodiment, the fins are formed to be thinner or smaller than what would be ideal to provide sufficient structural integrity to the stage. The structural integrity is then enhanced to meet the structural requirements by application of one or more coating materials as described herein. The material of the coating is lighter in weight (less dense) that the material of the fins, thus the overall mass of the stage can be made less without reducing structural integrity thereof.

[0077] In another embodiment, one or more of the fins (or all of the fins) are made a bit larger to support its structure during manufacture and handling, and then one or more of the fins subsequently machined to decrease the weight of the fins and hence the object stage. The coating can then be applied after such machining. In another embodiment, the fins can be machined after application of the coating.

[0078] FIGS. 2A-2B illustrate a mirror block MTMB of the reticle stage MT. FIG. 2A is a side cross- sectional view of the reticle stage mirror block MTMB, and FIG. 2B is a bottom view of the mirror block MTMB. The patterning device MA is positioned on a top surface of the mirror block MTMB (see FIGS. 1 A-1C). The top surface of the mirror block MTMB is a support surface MTSS. FIG. 2B shows a mask holder MH for holding the patterning device MA. The patterning device MA is held in the rectangular cut-out of the mask holder MH. Light travels through the patterning device MA on its way to expose the wafer W. FIGS. 2A-2B show that a fin network FN extends out downward from the bottom side of the mirror block MTMB. It should be appreciated that the fin network FN shown in FIGS. 2A-2B is only one example of a fin network. In other embodiments, the fin network FN could include any configuration and / or orientation of any number of fins. In one example, the support surface MTSS and the fin network FN are formed as a unitary, integral structure. The fin network FN includes a plurality of fins FI. The fins FI extend outward from the bottom side of the mirror block MTMB. The fins FI are all the same height, and the height of the fins FI is in the range of (i-j). In one embodiment, the fins FI have a thickness in the range of 1-15 mm. In one embodiment, the fins can have maximum thickness of 15 mm.

[0079] In FIG. 2B, only a small number of the fins FI have been labeled.

[0080] The fin network FN maintains the structural integrity of the mirror block MTMB and the support surface MTSS. The fin network FN comprises a plurality of fins FI that protrude out from the bottom side of the support surface MTSS. These fins FI are spaced out on the entirety of the bottom side of the support surface MTSS as shown. The fins FI are rigid to maintain the integrity and shape of the mirror block MTMB. The fin network FN prevents the support surface MTSS of the mirrorblock MTMB from bending. The fin network FN also helps to precisely mount components on the bottom side of the mirror block MTMB.

[0081] FIGS. 3A-3B illustrate a top side of a mirror block WTMB of the wafer stage WT. FIG. 3 A shows a top view, and FIG. 3B shows an angled top view. The top side of the wafer stage mirror block WTMB has a wafer holder WH to hold the wafer W (see FIGS. 1A-1C). The top surface of the mirror block WTMB is a support surface WTSS. Three electrostatic pin holes EPH apply vacuum forces to securely clamp the wafer W to the wafer holder WH. Three handling inserts HIN are positioned on the top surface of the mirror block WTMB to handle the wafer W. Four corner cubes CC are positioned at the corners of the mirror block WTMB. The comer cubes CC are prisms that reflect the interferometric laser light. Electrostatic chuck connections ECC are positioned at opposite sides of the mirror block WTMB. Three electrostatic chuck mounts ECM are positioned on the mirror block WTMB. Finally, docking pole hole DPH is positioned near the edge of the mirror block WTMB.

[0082] FIGS. 3C-3D illustrate a bottom side of the mirror block WTMB of the wafer stage WT. FIG. 3C shows a bottom view, and FIG. 3D shows an angled bottom view. The bottom side of the wafer stage mirror block WTMB includes a fin network FN having a plurality of fins FI. It should be appreciated that the fin network FN shown in FIGS. 3C-3D is only one example of a fin network. In other embodiments, the fin network FN could include any configuration and / or orientation of any number of fins. In one example, the wafer stage support surface WTSS and the fin network FN are formed as a unitary, integral structure. The fins FI have a maximum thickness of 3 mm. The fins FI extend downwards from the underside of the wafer stage mirror block WTMB. In FIGS. 3C-3D, only a small number of the fins FI have been labeled. Further, FIGS. 3C-3D show short stroke yokes SSY used to finely drive the mirror block WTMB in the x-, y-, and z-directions. In the illustrated example, there are 6 short stroke yokes SSY, 2 drive yokes for each direction. In the illustrated example, four long stroke Z yokes ZYO are positioned on the bottom side of the mirror block WTMB to move the wafer stage WT in the Z direction. Four end of stroke Z ESZ positioned at the corners of the mirror block WTMB are shown in the illustrated example. In other embodiments, any number of short stroke yokes SSY, long stroke Z yokes ZYO, and end of strokes Z ESZ may be present in any configuration. FIG. 3C shows the bottom side of the three electrostatic pin holes EPH. The three handling inserts HIN are also shown from the bottom side. The docking pole hole DPH is shown from the bottom side of the mirror block WTMB in FIG. 3C.

[0083] Similar to the reticle stage MT, the fin network FN maintains the structural integrity of the mirror block WTMB and the support surface WTSS of the wafer stage WT. The fin network FN comprises a plurality of fins FI that protrude out from the bottom side of the support surface WTSS. These fins FI are spaced out on the entirety of the bottom side of the support surface WTSS. The fins FI are rigid to maintain the integrity and shape of the mirror block WTMB. The fin network FNprevents the support surface WTSS of the mirror block WTMB from bending. The fin network FN also helps to precisely mount components on the bottom side of the mirror block WTMB.

[0084] FIG. 4 is a cross-sectional view of the fin FI in the fin network FN. FIG. 4 shows the fin FI prior to any processing or machining. The fin FI has a manufactured thickness in the range of 5-15 mm prior to machining.

[0085] FIG. 5 is a cross-sectional view of the fin FI after machining and coating. Prior to any processing, the fin FI starts out as the fin FI of FIG. 4. The fin FI is first subjected to a machining process. In one embodiment, the originally formed thickness of the fins FI can be reduced via a machining process. The machining process can be performed using a planar grinder, such as a 5 axis CNC mill. The CNC (computer numerical control) mill machine uses rotary cutters to cut and shape the fin material. Other types of grinders can also be used to shave off the sides of the fin material. In one embodiment, the fins FI have a thickness between 5-15 mm prior to the machining, and the machined portions of the fins FI have a reduced thickness in at least some areas thereof between 1-4 mm after the machining.

[0086] In one embodiment only some of the fins FI in the fin network FN are machined or grinded. Other fins FI can optionally be left untouched. Further, some portions of the fins FI are thinner than other portions. The fins FI do not need to have uniform thickness. For example, the thicker portions of the fins FI have a thickness between 5-15 mm, and the thinner portions of the fins FI have a thickness between 1-4 mm.

[0087] In one embodiment, the mirror block (and hence the fin material) can be made of ZERODUR®, which is a lithium-aluminosilicate glass-ceramic. In another embodiment, the mirror black and fin material can be comprised of SiSiC (silicon infiltrated silicon carbide). Another material that can be used is cordierite, which is a magnesium iron aluminum cyclosilicate. For low end applications, the mirror block may be made from aluminum. Other materials can also be used. Materials suitable to be used for the fin network FN should have a predetermined stiffness and rigidity.

[0088] Once the fins are of a desired thickness (e.g., as a result of their original formation or after a machining process to reduce the mass or thickness thereof in at least some locations), the fins FI undergo a coating process with a coating material CT. The coating process increases the rigidity and stiffness of the fins FI. The coating material CT bonds with the fin FI to create a stronger and stiffer fin network FN. By coating the coating material CT to the fins FI, the fin network FN can withstand higher forces without breaking.

[0089] In one embodiment, the coating is performed on one side of the fins FI, and that one side of the fins FI is coated with the coating material, while the other side is left untreated. In another embodiment, both sides of the fins FI are coated. FIG. 5 shows that both sides of the fin FI are coated with the coating material CT.

[0090] The coating process can be performed using chemical vapor deposition (CVD), dip coating, or other coating methods. Further, the coating material applied to the fins FI can be CVD diamond, diamond, DLC (diamond-like carbon), carbon nanotubes, c-BN (cubic boron nitride), BC2N (boroncarbonitride), SiC (silicon carbide), or other coating materials. The thickness of the coating material on the fins FI depends on the material used. The limiting factor is the in-plane stress created. In one embodiment, a CVD diamond coating with a thickness of between 1 to 16 pm is used. In one embodiment that CVD diamond coating is up to 16 pm thick. For DLC, in one embodiment the coating can have a thickness of as little as 1 pm, but may be as high as 14 pm or higher.

[0091] In one embodiment, any coating is applied to a thickness of between 1-16 pm on any given side of the fins FI. In one embodiment, the fin machining process (e.g., grinding process) is first performed, and then the coating process is performed. Other embodiments of this process are possible. For example, in another embodiment the coating process takes place prior to the machining process.

[0092] In one embodiment, one side of one or more fins FI is coated, then the opposite side of the one or more fins is machined, and then coating is applied to the just-machined opposite side. As a result, only one side is machined, while both sides are coated.

[0093] FIGS. 6A-6B are cross-sectional views of a fin FI with grooves GR. The grooves GR can be formed using a machining process such as milling. FIG. 6A shows the fin FI of FIG. 4 after grooves GR have been milled into one side of the fin FI. The grooves GR can be created using the CNC mill of the above machining process. The grooves GR are shown to be rectangular, but any other shape can be used. Grooves GR reduce the weight of the fin FI yet maintain the original thickness of the fin FI at its edges. Further, FIG. 6B shows that the fin FI having milled grooves GR can be coated with a coating material CT to improve the rigidity of the fin FI. The coating material CT is coated on the same side as the grooves GR.

[0094] Another embodiment involves milling grooves into the surface of the fins FI, then filling the grooves with a rigid coating (e.g., using one of the coating materials described above), and subsequently coating both the coated grooves and the rest of the fins FI with a softer material for protection.

[0095] FIGS. 7A-7B are cross-sectional views of a fin FI with a hole HO. The hole HO can be formed using a machining process such as milling. FIG. 7A shows the fin FI of FIG. 4 after a hole HO has been milled into the fin FI. The hole HO travels through the entire thickness of the fin FI. The hole HO is formed in the center of the fin FI but can be at another location. FIG. 7A shows one hole HO, but it is possible to have a plurality of holes. FIG. 7B shows the fin FI including the milled hole HO in which one side of the fin Fl is coated with a coating material CT to improve the rigidity of the fin FI. The coating material CT is coated on only one side of the fin FI, but in an alternative embodiment, the coating material CT is coated on both sides of the fin FI.

[0096] Various embodiments of the present apparatuses, systems and methods are disclosed in the subsequent list of numbered clauses:1. An object stage for use in lithography, wherein the object stage comprises: a support surface that is configured to support an object; a fin network comprising a plurality of fins that provide rigidity to the support surface; and a coating material provided on at least one of the fins to add stiffness to the at least one fin.2. The object stage of clause 1, wherein the object stage is a reticle stage or a wafer stage.3. The object stage of clauses 1 or 2, wherein the plurality of fins are made from a SiSiC (siliconized silicon carbide) material.4. The object stage of clause 1 or 2, wherein the plurality of fins are made from a glass-ceramic material.5. The object stage of clause 4, wherein the glass-ceramic material is a lithium-aluminosilicate material.6. The object stage of clause 1 or 2, wherein the plurality of fins are made from a cordierite material.7. The object stage of clause 1 or 2, wherein the plurality of fins are made from aluminum.8. The object stage of any of the preceding clauses, wherein the coating material comprises a diamond material.9. The object stage of any of the preceding clauses, wherein the coating material is provided on only one side of the at least one fin.10. The object stage of clauses 1-8, wherein the coating material is provided on both sides of the at least one fin.11. The object stage of any of the above clauses, wherein some portions of the at least one fin are thinner than other portions.12. The object stage of any of the above clauses, wherein the at least one fin has grooves formed therethrough.13. The object stage of any of the preceding clauses, wherein the support surface and the fin network are formed as a unitary, integral structure.14. The object stage of any of the preceding clauses, wherein the object stage comprises a mirror block.15. The object stage according to clause 11, wherein the thicker portions of the at least one fin have a thickness between 5-15 mm, and wherein the thinner portions of the fins have a thickness between 1-4 mm.16. A method of forming an object stage, comprising: providing an object stage initial structure comprising a support surface configured to support an object, and a fin network comprising a plurality of fins that provide rigidity to the support surface; machining at least one side of the fins to reduce a mass of the fins; and coating the fins of reduced mass with a coating material to increase the stiffness of the fins.17. The method of clause 16, wherein the coating comprises chemical vapor deposition.18. The method of clauses 16 or 17, wherein the coating material is a diamond material.19. The method of any of clauses 16-18, wherein the plurality of fins are made from a SiSiC (siliconized silicon carbide) material.20. The method of any of clauses 16-18, wherein the plurality of fins are made from a glass-ceramic material.21. The method of any of clauses 16-18, wherein the plurality of fins are made from a cordierite material.22. The method of any of clauses 16-18, wherein the plurality of fins are made from aluminum.23. The method of any of clauses 16-22, wherein the machining comprises reducing a thickness of the fins.24. The method of any of clauses 16-23, wherein the coating is applied to only one side of the fins.25. The method of clause 24, wherein the machining is performed on a side of the fins opposite the one side, after the one side has been coated.26. The method of clause 25, wherein the coating is applied to the opposite side of the fins, after the machining.27. The method of any of clauses 16-26, wherein some portions of the fins are thinner than other portions.28. The method of any of clauses 16-27, wherein at least some of the fins have grooves formed therethrough.29. The method of any of the clauses 16-28, wherein the support surface and the fin network are formed as a unitary, integral structure.30. The method of any of clauses 16-29, wherein the object stage comprises a mirror block.31. The method of any of clauses 16-30, wherein the fins have a thickness between 5-15 mm prior to the machining, and wherein the machined portions of the fins have a reduced thickness of between 1-4 mm after the machining.32. The method of any of clauses 16-31, wherein the machining comprises a CNC milling process.33. The method of any of clauses 16-32, wherein the coating is applied to a thickness of between 1-16 um on any given side of the fins.

[0097] Although specific reference may be made in this text to the manufacture of integrated circuits (ICs), it should be understood that the description herein has many other possible applications. For example, it may be employed in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, liquid-crystal display panels, thin-film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “reticle”, “wafer” or “die” in this text should be considered as interchangeable with the more general terms “mask”, “substrate” and “target portion”, respectively. In addition, any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.”

[0098] The concepts disclosed herein may be associated with any generic imaging system for imaging sub-wavelength features and may be especially useful with emerging imaging technologies capable of producing increasingly shorter wavelengths. Emerging technologies already in use include EUV (extreme ultraviolet), DUV lithography that is capable of producing a 193nm wavelength with the use of an ArF laser, and even a 157nm wavelength with the use of a Fluorine laser. Moreover, EUV lithography is capable of producing wavelengths within a range of 20-5nm by using a synchrotron or by hitting a material (either solid or a plasma) with high energy electrons in order to produce photons within this range.

[0099] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. An object stage for use in lithography, wherein the object stage comprises: a support surface that is configured to support an object; a fin network comprising a plurality of fins that provide rigidity to the support surface; and a coating material provided on at least one of the fins to add stiffness to the at least one fin.

2. The object stage of claim 1, wherein: the object stage is a reticle stage or a wafer stage; the object stage comprises a mirror block; and the plurality of fins are made from a SiSiC (siliconized silicon carbide) material, a glassceramic material that is a lithium-aluminosilicate material, a cordierite material, or aluminum.

3. The object stage of any of the preceding claims, wherein the coating material comprises a diamond material.

4. The object stage of any of the preceding claims, wherein the coating material is provided on only one side of the at least one fin or is provided on both sides of the at least one fin.

5. The object stage of any of the preceding claims, wherein: some portions of the at least one fin are thinner than other portions; the at least one fin has grooves formed therethrough; and the support surface and the fin network are formed as a unitary, integral structure.

6. The object stage according to claim 5, wherein the thicker portions of the at least one fin have a thickness between 5-15 mm, and wherein the thinner portions of the fins have a thickness between 1-4 mm.

7. A method of forming an object stage, comprising: providing an object stage initial structure comprising a support surface configured to support an object, and a fin network comprising a plurality of fins that provide rigidity to the support surface; machining at least one side of the fins to reduce a mass of the fins; and coating the fins of reduced mass with a coating material to increase the stiffness of the fins.

8. The method of claim 7, wherein the coating comprises chemical vapor deposition and wherein the coating material is a diamond material.

9. The method of any of claims 7-8, wherein the plurality of fins are made from a SiSiC (siliconized silicon carbide) material, a glass-ceramic material, a cordierite material, or aluminum.

10. The method of any of claims 7-9, wherein: the machining comprises reducing a thickness of the fins; the coating is applied to only one side of the fins; and the machining is performed on a side of the fins opposite the one side, after the one side has been coated.

11. The method of claim 10, wherein the coating is applied to the opposite side of the fins, after the machining.

12. The method of any of claims 7-11, wherein: some portions of the fins are thinner than other portions; at least some of the fins have grooves formed therethrough; and the support surface and the fin network are formed as a unitary, integral structure.

13. The method of any of claims 7-12, wherein: the object stage comprises a mirror block; and the machining comprises a CNC milling process.

14. The method of any of claims 7-13, wherein the fins have a thickness between 5-15 mm prior to the machining, and wherein the machined portions of the fins have a reduced thickness of between 1-4 mm after the machining.

15. The method of any of claims 7-14, wherein the coating is applied to a thickness of between 1-16 um on any given side of the fins.

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