NL2021464A

NL2021464A - Abrasion tool and method for removing contamination from an object holder

Info

Publication number: NL2021464A
Application number: NL2021464A
Authority: NL
Inventors: Sohrabibabaheidary Damoon; Michael Levy Keane; Wang Qingsong
Original assignee: Asml Holding Nv
Priority date: 2017-09-15
Filing date: 2018-08-14
Publication date: 2019-03-19
Also published as: CN111095113A; KR20200052299A; CN111095113B; WO2019052757A1

Abstract

A method of processing a support surface of an object holder using an abrasion tool comprising a substantially flat surface for positioning on and in contact With the object holder, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 1 nm Ra to about 100 nm Ra, has a flatness of less than or equal to about 3000 nm Within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 3000 nm Within the predetermined area of the substantially flat surface.

Description

FIELD [0001] The present description relates to an object holder and techniques of cleaning and/or abrading a surface of an object holder.

BACKGROUND [0002] A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs) or other devices. In such a case, a patterning device (e.g., a mask) may contain or provide a pattern corresponding to an individual layer of the device (“design layout’’), and this pattern can be transferred onto a target portion (e.g. comprising one or more dies) on a substrate (e.g., silicon wafer) that has been coated with a layer of radiation-sensitive material (“resist”), by methods such as irradiating the target portion through the pattern on the patterning device. In general, a single substrate contains a plurality of adjacent target portions to which the pattern is transferred successively by the lithographic apparatus, one target portion at a time. In one type of lithographic apparatus, the pattern on the entire patterning device is transferred onto one target portion in one go; such an apparatus is commonly referred to as a stepper. In an alternative apparatus, commonly referred to as a slep-and-scan apparatus, a projection beam scans over the patterning device in a given reference direction (the scanning direction) while synchronously moving the substrate parallel or anti-parallel to this reference direction. Different portions of the pattern on the patterning device are transferred to one target portion progressively. Since, in general, the lithographic apparatus will have a magnification factor M (generally < 1), the speed F at which the substrate is moved will be a factor M times that at which the projection beam scans the patterning device.

[0003] Prior to the device fabrication procedure of transferring the pattern from the patterning device to the substrate of the device manufacturing process, the substrate may undergo various device fabrication procedures of the device manufacturing process, such as priming, resist coating and a soft bake. After exposure, the substrate may be subjected to other device fabrication procedures of the device manufacturing process, such as a post-exposure bake (PEB), development, and a hard bake. This array of device fabrication procedures is used as a basis to make an individual layer of a device, e.g., an IC. The substrate may then undergo various device fabrication procedures of the device manufacturing process such as etching, ion-implantation (doping), metallization, oxidation, chemo-mechanical polishing, etc., all intended to finish off the individual layer of the device. If several layers are required in the device, then the whole process, or a variant thereof, is repeated for each layer. Eventually, a device will be present in each target portion on the substrate. If there is a plurality of devices, these devices are then separated from one another by a technique such as dicing or sawing, whence the individual devices can be mounted on a carrier, connected to pins, etc.

[0004] So, manufacturing devices, such as semiconductor devices, typically involves processing a substrate (e.g., a semiconductor wafer) using a number of fabrication processes to form various features and multiple layers of the devices. Such layers and features are typically manufactured and processed using, e.g., deposition, lithography, etch, chemical-mechanical polishing, and ion implantation. Multiple devices may be fabricated on a plurality of dies on a substrate and then separated into individual devices. This device manufacturing process may be considered a patterning process. A patterning process involves a patterning step, such as optical or nanoimprint lithography using a lithographic apparatus, to provide a pattern on a substrate and typically, but optionally, involves one or more related pattern processing steps, such as resist development by a development apparatus, baking of the substrate using a bake tool, etching using the pattern using an etch apparatus, etc. Further, one or more metrology processes are typically involved in the patterning process.

SUMMARY [0005] Because of, for example, imaging and overlay requirements as part of a patterning process, surfaces of object clamps and tables (or generally object holders) are often measured for accuracy. Such object holders can include the substrate support to hold the substrate onto which the pattern is projected, but can include other object holders such a patterning device support. [0006] Object holders can become contaminated. For example, object holders can have one or more projections on which the object is supported. These projections typically have the purpose of reducing the possibility of contamination occurring between the actual supporting surface of the object holder and the object since the object holder will have only a limited contact area with supporting surface of the object holder. These one or more projections can also be referred to as one or more burls or pimples.

[0007] But, even the projection top surfaces can suffer from contamination. Such contamination has been found to be not fully removable by standard cleaning methods (e.g., wipes, stamps, etc.). Additionally or alternatively, such standard cleaning methods can provide further problems (e.g., particles (e.g., fibers) or chemical residue) on the surface, cause damage or further contamination to the surface, present environmental concerns and/or require secondary to clean off particles and/or residue from a prior cleaning (which in some cases may not be able to be fully cleaned). In addition, stubborn contamination may not be able to be cleaned off with standard cleaning methods. A few nanometers of contamination can change the flatness and strongly influence specifications and performance.

[0008] Load grid error (sometimes referred to as wafer load grid (WLG) error) is another potential drawback in object holders arising from contamination. Load grid error is a shift in a direction generally parallel to a support plane / surface of the object holder. Where the object is supported by one or more projections, load grid error can be due to a relatively high friction between the object (e.g., radiation-sensitive substrate) and the top(s) of the one or more projections of the object holder. Contamination may be a cause for issues associated with load grid error, but load grid error can also arise from other causes (e.g., overly smooth surfaces). So, both the contamination itself and load grid error (which can be at least part due to contamination) may potentially cause errors, e.g., overlay errors, arising from the lithography process.

[0009] Accordingly, it would be advantageous, for example, to provide an improved method and tool to remove contamination off of an object holder, particularly an object holder having one or more projections, so that errors (e.g., load grid error, overlay error, etc.) can be reduced or substantially prevented. It would be advantageous, for example, to provide an improved method and tool to provide roughness to an object holder (e.g., to decrease the friction coefficient of a support surface and so help to reduce load grid error), particularly an object holder having one or more projections, so that errors (e.g., load grid error, overlay error, etc.) can be reduced or substantially prevented. So, in an embodiment, there is provided an apparatus for removing contamination and/or providing roughness to a surface of an object holder, in particular to sensitive or nanometer flat surfaces.

[0010] In an embodiment, there is provided a method of processing a support surface of a holder configured to hold an object, the object holder comprising a plurality of protrusions, the protrusions extending from a body of the holder and configured to provide a support surface for the object, the method comprising: providing an abrasion tool comprising a substantially flat surface for positioning on and in contact with the object holder; positioning the substantially flat surface of the abrasion tool in contact with the support surface of the object holder; and providing relative movement between the abrasion tool and at least part of the object holder while the abrasion tool is in contact with the support surface to remove contamination from the protrusions, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 15 nm Ra to about 50 nm Ra, has a flatness of less than or equal to about 500 nm within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface.

[0011] In an embodiment, there is provided an abrasion tool configured to be positioned on and in contact with an object holder comprising a plurality of protrusions providing a support surface for an object, the abrasion tool comprising a substantially flat surface arranged to abrade the support surface by relative movement between the substantially flat surface and the support surface to remove contamination from the support surface, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 15 nm Ra to about 50 nm Ra, has a flatness of less than or equal to about 500 nm within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface.

[0012] In an embodiment, there is provided an abrasion tool configured to be positioned on and in contact with an object holder comprising a plurality of protrusions providing a support surface for an object, the abrasion tool comprising a substantially flat surface arranged to abrade the support surface by relative movement between the substantially flat surface and the support surface to roughen the support surface, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 200 nm Ra to about 500 nm Ra.

[0013] In an embodiment, there is provided a lithographic apparatus comprising: a patterning device support configured to support a patterning device, the patterning device configured to pattern a beam of radiation to form a patterned beam of radiation; a projection system configured to project the patterned beam of radiation onto a target portion of a substrate; a substrate holder configured to hold a substrate; a system arranged to remove contamination from a support surface of an object holder comprising a plurality of protrusions to provide a support surface for an object, the system comprising an abrasion tool comprising a substantially flat surface for positioning on and in contact with the object holder, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 15 nm Ra to about 50 nm Ra, has a roughness selected from the range of about 200 nm Ra to about 500 nm Ra, has a flatness of less than or equal to about 500 nm within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface.

BRIEF DESCRIPTION OF THE DRAWINGS [0014] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0015] FIG. 1 schematically depicts a lithographic apparatus according to an embodiment of the disclosure;

[0016] Fig. 2 schematically depicts an embodiment of a lithographic cell or cluster according to an embodiment of the disclosure;

[0017] FIG. 3 schematically depicts a cross-sectional view of an object holder in accordance with an embodiment of this disclosure;

[0018] FIG. 4 is a schematic detailed, overhead view of projections on the object holder of FIG. 2 with contamination thereon;

[0019] FIG. 5 is a detailed, close up view of projections on the object holder after abrasion / cleaning in accordance with an embodiment of this disclosure;

[0020] FIG. 6 illustrates a schematic example of an abrasion tool used to abrade an object holder in accordance with an embodiment of this disclosure;

[0021] FIG. 7 schematically depicts movement of the abrasion tool across the object holder in accordance with a method of abrading the object holder as disclosed in accordance with an embodiment of this disclosure;

[0022] FIG. 8 is a detailed, close up view of a projection on the object holder with contamination thereon;

[0023] FIG. 9 is a detailed, close up view of the projection of FIG. 8 after abrasion / cleaning in accordance with an embodiment of this disclosure; and [0024] FIG. 10 is a block diagram of an example computer system according to an exemplary embodiment of the present disclosure.

[0025] The accompanying drawings have not necessarily been drawn to scale. Any values dimensions illustrated in graphs and figures are for illustration purposes only and may or may not represent actual or preferred values or dimensions. Where applicable, some or all features may not be illustrated to assist in the description of underlying features. In the drawings:

DETAIEED DESCRIPTION [0026] FIG. 1 schematically depicts a lithographic apparatus according to an embodiment of the invention. The apparatus comprises:

-an illumination system (illuminator) IL configured to condition a radiation beam B (e.g. UV radiation orDUV radiation);

-a support structure (e.g. a mask table) MT constructed to hold a patterning device (e.g. a mask) MA and connected to a first positioner PM configured to accurately position the patterning device in accordance with certain parameters;

-a substrate table (e.g. a wafer table) WT constructed to hold a substrate (e.g. a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate in accordance with certain parameters; and

-a projection system (e.g. a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by patterning device MA onto a target portion C (e.g. comprising one or more dies) of the substrate W.

[0027] The illumination system may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic or other types of optical components, or any combination thereof, for directing, shaping, or controlling radiation.

[0028] The support structure holds the patterning device in a manner that depends on the orientation of the patterning device, the design of the lithographic apparatus, and other conditions, such as for example whether or not the patterning device is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, which may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system. Any use of the terms “reticle” or “mask” herein may be considered synonymous with the more general term “patterning device.” [0029] The term “patterning device” used herein should be broadly interpreted as referring to any device that can be used to impart a radiation beam with a pattern in its cross-section such as to create a pattern in a target portion of the substrate. It should be noted that the pattern imparted to the radiation beam may not exactly correspond to the desired pattern in the target portion of the substrate, for example if the pattern includes phase-shifting features or so called assist features. Generally, the pattern imparted to the radiation beam will correspond to a particular functional layer in a device being created in the target portion, such as an integrated circuit. [0030] The patterning device may be transmissive or reflective. Examples of patterning devices include 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 to reflect an incoming radiation beam in different directions. The tilted mirrors impart a pattern in a radiation beam which is reflected by the mirror matrix.

[0031] The term “projection system” used herein should be broadly interpreted as encompassing 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 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”.

[0032] As here depicted, the apparatus is of a transmissive type (e.g. employing a transmissive mask). Alternatively, the apparatus may be of a reflective type (e.g. employing a programmable mirror array of a type as referred to above, or employing a reflective mask). [0033] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables (and/or two or more support structures). In such “multiple stage” machines the additional tables / support structure may be used in parallel, or preparatory steps may be carried out on one or more tables / support structure while one or more other tables / support structures are being used for exposure.

[0034] Referring to FIG. 1, the illuminator IL receives a radiation beam from a radiation source SO. The source and the lithographic apparatus may be separate entities, for example when the source is an excimer laser. In such cases, the source is not considered to form part of the lithographic apparatus and the radiation beam is passed from the source SO to the illuminator IL with the aid of a beam delivery system BD comprising, for example, suitable directing mirrors and/or a beam expander. In other cases the source may be an integral part of the lithographic apparatus, for example when the source is a mercury lamp. The source SO and the illuminator IL, together with the beam delivery system BD if required, may be referred to as a radiation system.

[0035] The illuminator IL may comprise an adjuster AD configured to adjust the angular intensity distribution of the radiation beam. Generally, at least the outer and/or inner radial extent (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution in a pupil plane of the illuminator can be adjusted. Tn addition, the illuminator IL may comprise various other components, such as an integrator IN and a condenser CO. The illuminator may be used to condition the radiation beam, to have a desired uniformity and intensity distribution in its cross section.

[0036] The radiation beam B is incident on the patterning device (e.g., mask) MA, which is held on the support structure (e.g., mask table) MT, and is patterned by the patterning device. 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 IF (e.g. an interferometric device, linear 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. Similarly, the first positioner PM and another position sensor (which is not explicitly depicted in FIG. 1) can be used to accurately position the patterning device MA with respect to the path of the radiation beam B, e.g. after mechanical retrieval from a mask library, or during a scan. In general, movement of the support structure MT may 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 may 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 support structure MT may be connected to a short-stroke actuator only, or may be fixed. Patterning device MA and substrate W may be aligned using patterning device alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks as illustrated occupy dedicated target portions, they may be located in spaces between target portions (these are known as scribe-lane alignment marks). Similarly, in situations in which more than one die is provided on the patterning device MA, the patterning device alignment marks may be located between the dies.

[0037] The depicted apparatus could be used in at least one of the following modes:

[0038] 1. In step mode, the support structure MT and the substrate table WT are kept essentially stationary, while an entire pattern imparted to the radiation beam 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. In step mode, the maximum size of the exposure field limits the size of the target portion C imaged in a single static exposure.

[0039] 2. In scan mode, the support structure MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam 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 MT may be determined by the (de-)rnagnification and image reversal characteristics of the projection system PS. In scan mode, the maximum size of the exposure field limits the width (in the non-scanning direction) of the target portion in a single dynamic exposure, whereas the length of the scanning motion determines the height (in the scanning direction) of the target portion.

[0040] 3. In another mode, the support structure MT is kept essentially stationary holding a programmable patterning device, and the substrate table WT is moved or scanned while a pattern imparted to the radiation beam is projected onto a target portion C. In this mode, generally a pulsed radiation source is 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 programmable patterning device, such as a programmable mirror array of a type as referred to above.

[0041] Combinations and/or variations on the above described inodes of use or entirely different inodes of use may also be employed.

[0042] As shown in FIG. 2, the lithographic apparatus LA may form part of a lithographic cell LC, also sometimes referred to as a lithocell or lithocluster, which also includes apparatus to perform one or more pre- and post-exposure processes on a substrate. Conventionally these include one or more spin coaters SC to deposit a resist layer, one or more developers DE to develop exposed resist, one or more chill plates CH and one or more bake plates BK. A substrate handler, or robot, RO picks up a substrate from input/output ports I/Ol, I/O2, moves it between the different process devices and delivers it to the loading bay LB of the lithographic apparatus. These devices, which are often collectively referred to as the track, are under the control of a track control unit TCU which is itself controlled by the supervisory control system SCS, which also controls the lithographic apparatus via lithographic control unit LACU. Thus, the different apparatus may be operated to maximize throughput (e.g., substrates processed per unit time) and processing efficiency. The lithographic cell LC may further comprises one or more etchers to etch a substrate, one or more measuring devices configured to measure a parameter of at substrate, and/or one or more chemical mechanical planarization (CMP) tools to smooth a surface of a substrate. The measuring device may comprise an optical measurement device configured to measure a physical parameter of the substrate, such as a scatterometer, a scanning electron microscope, etc. The measuring device may be incorporated in the lithographic apparatus LA. An embodiment of the present disclosure may be implemented in or with the supervisory control system SCS or the lithographic control unit LACU. For example, data from the supervisory control system SCS or the lithographic control unit LACU may be used by an embodiment of the present disclosure and one or more signals from an embodiment of the present disclosure may be provided to the supervisory control system SCS or the lithographic control unit LACU.

[0043] As noted above, an object holder can become contaminated. Accordingly, there is described herein, in an embodiment, a cleaning technique to clean at least part of the object holder. Further, as discussed further herein, it can be desirable to provide a roughness to a surface of an object holder. So, according to an embodiment, there is described herein a roughening technique to roughen at least of an object holder.

[0044] Embodiments herein focus on a substrate table WT as the object holder and a substrate W as the object. However, the description herein is applicable to other object holders, such as the patterning device support structure MT. Further, the description herein is applicable to object holders in an apparatus other than a lithographic apparatus. For example, the description herein can be applied to an object holder in a track tool, in an etcher tool, in a chemical mechanical planarization (CMP) tool, etc. Further, the description herein can be more generally applicable to structures used in a patterning process that are susceptible to contamination and/or that are desired to be roughened.

[0045] FIG. 2 is a schematic depiction of a substrate holder. In this example, a substrate table WT is depicted that supports a substrate chuck 22 which supports a substrate. However, such a substrate chuck is not necessary. As shown by the cross-sectional view in FIG. 2, the substrate chuck 22 may be part of the movable substrate table WT and directly support the substrate W. So, in an embodiment, the substrate chuck 22 may be the object holder. In this embodiment, the substrate chuck 22 is in or on a substrate stage base 24. In an embodiment, the substrate chuck 22 is removable from the substrate stage base 24. In an embodiment, the substrate table WT forms a recess into which the substrate W can be located. The recess can be formed by the substrate stage base 24, by another structure located on the substrate stage base 24 (not shown in FIG. 2), or a combination thereof.

[0046] As shown, the chuck 22 is configured to provide one or more support surfaces to directly contact and support the substrate W. In an embodiment, the substrate chuck 22 has one or more projections 20 (e.g., burls or protrusions) protruding or extending substantially perpendicularly from a surface of the chuck 22, Accordingly, in this situation, the substrate table WT may be referred to as a pimple table or a burl table. In particular, during operation, a lower surface or backside of the substrate W may be supported on upper face(s) of the one or more projections 20. Thus, the top(s) of the one or more projections define an effective support plane for the substrate.

[0047] So, the substrate table WT is configured such that, when the substrate W is positioned on the substrate chuck 22, i.e., at least on the one or more projections 20, an upper surface of the substrate W lies in a predetermined plane in relation to a propagation direction of the exposure radiation. In ail embodiment, the surface of the substrate W is oriented transverse to the propagation direction of the beam.

[0048] The arrangement of one or more projections 20 is not limiting. In an embodiment, the projections are arranged in an array, such as shown in the detailed, overhead view of at least part of the table surface in FIGS. 3-5 and 7. Also, the surface area of the substrate chuck 22 and/or its projection(s) that is in contact with the substrate W is not intended to be limiting.

[0049] In an embodiment, the substrate W may be held on the substrate chuck 22 using, e.g., a vacuum system or an electrostatic clamping arrangement (not shown). Thus, in the case of a vacuum system, the space around the burls, below the substrate, may be subject to a low pressure in order to draw the substrate W onto the substrate chuck 22. Accordingly, the substrate W may be vacuum clamped to the substrate chuck 22.

[0050] In an embodiment, where the substrate chuck 22 is removable, the substrate chuck 22 may be held on the substrate base 24 using, e.g., a vacuum system or an electrostatic clamping arrangement (not shown). Accordingly, in the case of a vacuum system, the substrate chuck 22 may be vacuum clamped to the substrate base 24.

[0051] The above-described arrangement of one or more projections 20 may minimize or reduce the total area of the substrate W in contact with the substrate table WT and so generally reduces the overall amount of contaminants between the substrate W and a corresponding surface of the substrate table WT contacting the substrate W. However, as noted previously, when contaminants are present on the one or more projections, they could undesirable consequences such as deformation of the substrate W in a direction substantially perpendicular to the radiation receiving surface of the substrate and/or cause load grid errors.

[0052] In some cases, contamination will remain even after using standard and known wipe and stamping processes on the substrate table WT. For example, FIGS. 4 and 5 illustrate examples of stubborn contaminants or debris at a micron sized level that is left on projections 20 of a substrate table WT and that cannot be cleaned by such normal cleaning approaches. Arrows are provided on FIG. 3 for emphasis of locations of contamination on projection. Such contaminants may be at a nanometer (nm) thickness or level on projections, but can cause significant errors when the substrate W is placed thereon and exposed to radiation.

[0053] Accordingly, this disclosure describes a method and tools configured for nm level surface cleaning and contamination/debris removal from at least the protrusions of the substrate table WT, so that it may preserve the surface of the substrate table without substantially affecting its performance.

[0054] In an embodiment, at least one abrasion tool with a substantially flat surface is provided for positioning on and in contact with an object holder such as the substrate table WT. In an embodiment, the abrasion tool removes contamination from the object holder, for example removes contamination at least from projections, such as projections 20, of an object holder. In an embodiment, the abrasion tool provides a roughness to a surface of the object holder (e.g., to decrease the friction coefficient of a support surface and so help to reduce load grid error), for example provides roughness to at least the projections, such as projections 20, of an object holder.

[0055] FIG. 6 illustrates an example of an abrasion tool 30 in the form of a disk, for example. However, the shape and form of the abrasion tool is not limited to this illustrated embodiment; for example, it can be rectangular shaped (or other shape) and doesn’t need to be plate-like as depicted. The tool 30 has at least one substantially flat abrasion surface 32. The substantially flat abrasion surface 32 is configured to be positioned against and/or in contact with a support surface of the object holder, during use. In an embodiment, the surface 32 is configured to be brought into contact with the upper surface of at least the object holder. In an embodiment, the surface 32 is configured to be brought into contact with the upper surface of at least the projections of an object holder.

[0056] The tool 30 is configured for movement across the object holder while in contact with a support surface of the object holder. In this context, movement “across” and “in contact” with the support surface refers to relative movement between the tool 30 and the support surface while the tool is in contact with the support surface; so, the tool 30 can be moved, the support surface can be moved, or both. In an embodiment, the support surface is at least an upper surface or top portion of a projection of the object holder. In an embodiment, the tool moves across the support surfaces provided by a plurality of projections of the object holder. Moving the tool across and in contact with the support surface causes an abrading against the support surface using the tool 30 in order to remove contamination from the support surface, e.g., from the support surface provided by projections, such as projections 20, of the object holder.

[0057] A body of the abrasion tool 30 and the substantially flat surface 32 may be integrally formed or be separate from one another. In an embodiment, both a body of the tool 30 and the surface 32 are formed from a single material. For example, in an embodiment, the abrasion tool 30 is formed from a homogeneous, non-natural (artificially made or man-made) material. In an embodiment, the material is sintered.

[0058] As previously noted, the shape and/or form of the body of the abrasion tool 30 (including the substantially flat surface thereof) is not intended to be limiting. The shape of the tool 30 and/or the substantially flat surface 32 may be, for example, circular, ovular, polygonal, triangular, or tear-drop shaped. The shape of the body of the tool 30 may be based on a design that sits within a person’s palm (if used manually), for example. In an embodiment, the body of the abrasion tool 30 has a different shape than the substantially flat surface 32. For explanatory and illustrative purposes only, the tool 30 and surface 32 are shown in FIG. 5 in integral form and as having a disk-like shape.

[0059] The tool 30 and/or surface 32 may have a cross-wise dimension D (e.g., diameter or width) of up to about 50 mm, for example. In an embodiment, the surface 32 has a cross-wise dimension selected from a range of about 20 mm to about 300 mm, selected from a range of about 20 mm to about 100 mm, or selected from a range of about 20 mm to about 50 mm. In an embodiment, the surface 32 has a cross-wise dimension of at least 50 mm.

[0060] The thickness of the surface 32 and/or the abrasion tool 30 may vary. In an embodiment, the thickness T of the surface 32 and/or the abrasion tool 30 is selected from a range of about 5 mm to about 100 mm. In an embodiment, the overall thickness T of the abrasion tool 30 with surface 32 is selected from a range of about 10 mm to about 50 mm, selected from a range of about 10 mm to about 25 mm, or is about 15 mm.

[0061] In an embodiment, the surface 32 of the abrasion tool 30 may have a roughness selected from the range of about 1 nm Ra to about 2000 nm Ra or from the range of about 1 nm Ra to about 1200 nm Ra. In an embodiment, the surface 32 of the abrasion tool 30 may have a roughness of at least about 15 nm Ra. In an embodiment, the roughness of the surface 32 is selected in the range of about 1 nm Ra to about 100 nm Ra or from the range of about 15 nm Ra to about 50 nm Ra.

[0062] In an embodiment, the surface 32 has a desired high flatness. The surface 32 has two general areas - a first predetermined area that is designed for consistent contact with a surface of the object holder (e.g., an area of the surface 32 that is designed for consistent with the projections of an object holder) and a second predetermined area that is a transition of the first determined area to another surface (e.g., an edge 36 of the surface 32 may have a chamfer or curve) and which area may have relatively infrequent contact with the surface of the object holder. In an embodiment, a central portion of the surface 32, minus the chamfer or curve of the edge 36, may be the first predetermined area used to have a particular flatness. In an embodiment, the flatness of the first predetermined area of the surface 32 is less than about 600 nm within that area. In an embodiment, the flatness of the first predetermined area of the surface 32 is less than about 300 nm within that area. In an embodiment, the flatness of the first predetermined area of the surface 32 is less than about 100 nm within that area. In an embodiment, the flatness may be greater than about 100 nm within the first predetermined area. [0063] In an embodiment, the flatness of the first predetermined area of the surface 32 is selected from the range of about 20 nm to about 3000 nm within that area for cleaning and/or roughening. In an embodiment, the flatness is lower for lower roughness and higher for higher roughness. So, in an embodiment, the flatness can be selected from the range of about 20 nm to about 400 nm for roughness from the range of about 1 nm Ra to 100 nm Ra (e.g., for cleaning). In an embodiment, the flatness can be selected from the range of about 400 nm to about 3000 nm for roughness from the range of about 100 nm Ra to 2000 nm Ra (e.g., for roughening).

[0064] In an embodiment, the surface 32 has a flatness per unit cross-wise dimension of the surface of about 150 nm/cm or less, about 100 nm/cm or less, about 75 nm/cm, about 50 nm/cm or less, or about 25 nm/cm or less, within the first predetermined area. So, for example, for a 5 cm crosswise dimension area and a flatness per unit cross-wise dimension of the surface of about 150 nm/cm, that area has a flatness of 750 nm or less.

[0065] In an embodiment, the hardness of the surface 32 is greater than about 10 GPa. In an embodiment, the hardness of surface 32 is selected from a range of about 10 GPa to about 30 GPa.

[0066] In an embodiment, at least the surface 32 of the tool 30 is made of a stone, granite, or ceramic material. In an embodiment, the surface 32 comprises or consists essentially of a material selected from: aluminum oxide (AI2O3), silicon carbide (SiC), silicon nitride (S13N4), aluminum nitride (AIN), and/or chromium nitride (CrN).

[0067] FIG. 7 schematically illustrates a method of relative movement between the abrasion tool 30 and an object holder such as substrate table WT. In an embodiment, after placing the abrasion tool 30 in contact with or onto an object support surface of the object holder, the abrasion tool 30 is moved across the surface by sliding the abrasion tool 30 back and forth across (e.g., left and right in Figure 7) the support surface in a series of successive passes. Each respective pass may be in an opposite direction to a previous pass. According to this disclosure, a pass is referred to as a relative movement between the tool 30 and the object holder from one edge or side (e.g., left) of a support surface or plane towards an opposite edge or side (e.g., right) of a support surface or plane. The number of passes is not limited, and may be dependent upon the material used to form the surface 32 and/or form a body of the tool 30 itself. In accordance with an embodiment, at least 6 passes using the tool 30 are used.

[0068] In an embodiment, the abrasion tool 30 may be moved in a substantially loop (e.g., circular) path along and across at least part of the support surface or plane of the object holder when the surface 32 is in contact therewith. For example, in an embodiment, the abrasion tool 30 can be moved in loops as it is translated in a pass. In an embodiment, the abrasion tool 30 is moved in a “Z”-like pattern (e.g., randomly) across the support surface or plane. In an embodiment, the abrasion tool 30 can be rotated on an axis passing through and generally perpendicular to a central portion of the surface 32. In an embodiment, the rotation can be a partial rotation about the axis such as a rotation of less than or equal to + about 90 degrees, less than or equal to ± about 60 degrees, less than or equal to ± about 45 degrees or less than or equal to + about 30 degrees. Tn an embodiment, the rotation (including partial rotation) is combined with a linear motion (e.g., the passes or “Z”-like pattern). In an embodiment, to clean an edge of the support surface or plane of the object holder, the abrasion tool 30 may be moved in a ring fashion (e.g., circular) around the edge (e.g., rotating to follow a contour of the edge). In an embodiment, the ring fashion movement can be repeated to create concentric ring movements. In an embodiment, various combinations of these movement techniques can be used. In an embodiment, in any of the movement techniques, a subsequent movement can overlap at least partially an area covered by a prior movement.

[0069] In an embodiment, the movement of the abrasion tool across the object holder can be performed manually by a person holding the abrasion tool 30. hi an embodiment, the movement of the abrasion tool 30 is performed by a machine, an automated system, or robot. For example, a robotic arm 34 (see FIG. 7) can be used to move the abrasion tool 30. The abrasion tool 30 may be positioned on an end of the robotic arm 34, placed thereon, or captured by a device at the end of the arm 34 in a manner such that the surface 32 can be positioned on and in contact with the object holder for movement across the object holder while in contact with the object holder. [0070] The amount of force or pressure applied onto the support surface using the abrasion tool 30 can vary, hi an embodiment, the abrasion tool 30 is self-weighted and only manual force is used to move the tool 30 across the surface of the object holder, without adding a normal force with respect to the support surface or plane of the object holder (e.g., zero normal force in the Zdirection; only force is used for lateral movement within the predetermined plane, e.g., in the X and/or Y directions). Thus, the force or pressure at surface 32 and the support surface or plane of the object holder (or at least the protrusions 20) may be proportional to the weight / mass of the abrasion tool 30. In an embodiment, a force or pressure is greater than or less than a force or pressure caused by the weight of the tool 30 multiplied by gravity. In an embodiment, the force or pressure is greater than a force or pressure caused by the weight of the tool 30 multiplied by gravity, e.g., more than or equal to about 1.5 times, more than or equal to about 2 times, more than or equal to about 3 times or more than or equal to about 4 times the amount of that force. In an embodiment, the force or pressure is less than a force or pressure caused by the weight of the tool 30 multiplied by gravity, e.g., more than about '/2 but less than the full amount of that force. In an embodiment, a person may manually apply force to the abrasion tool 30 when relative movement between the tool 30 and the support surface or plane of the object holder is provided. In the use of a machine or robot arm 34, for example, the machine or robot arm may be designed to apply force or pressure in the normal direction of the support surface or plane with the abrasion tool 30, thus positioning the surface 32 against a support surface of the object holder, while moving the abrasion tool 30 across the support surface of the object while in contact with the support surface.

[0071] The weight of the abrasion tool 30 may be dependent upon the material used to form the body of the tool and/or the substantially flat surface 32. In an embodiment, the weight of the abrasion tool 30 is selected from the range of about 80 grams to about 150 grams. In an embodiment, the weight of the abrasion tool 30 is selected from the range of about 100 grams to about 120 grams.

[0072] While embodiments above has focused mostly on moving the abrasion tool 30, the relative movement between the abrasion tool 30 and the object holder can be accomplished in different ways. For example, in an embodiment, the object holder is configured for movement relative to the abrasion tool 30 while the abrasion tool 30 is in contact with the object holder for an abrading action. In an embodiment, both the abrasion tool 30 and the object holder are configured for movement while the abrasion tool 30 is in contact with the object holder for an abrading action.

[0073] In an embodiment, a support surface of the object holder is wiped between a set of successive passes of the abrasion tool 30 with respect to the object holder.

[0074] In an embodiment, a solvent is used when removing contamination using the abrasion tool 30. Generally, the solvent may assist in improving cleaning efficiency, reducing friction by acting as a lubricant, and decreasing risk of damage to the object holder. Using a solvent tends to decrease forces on projections, allowing for smooth movement in the contact area between the surface 32 and a support surface of the object holder. It also acts as a carrier, in that the fluid may hold or suspend material dislodged by the surface 32 (instead of being re-deposited onto the object holder). The type of solvent used is not intended to be limiting. In an embodiment, the solvent is volatile. In an embodiment, the solvent is an alcohol. In an embodiment, the solvent is methanol, acetone, and/or isopropyl alcohol. In an embodiment, water is used.

[0075] For example, in an embodiment, a contact area between the substantially flat surface 32 of the abrasion tool 30 and a support surface of the object holder is wetted with a solvent. In an embodiment, the solvent is applied directly to the surface 32 of the abrasion tool before it is positioned in contact with the support surface. In an embodiment, the solvent is applied to the object holder, e.g., a support surface of the object holder, before the tool 30 and its surface 32 is positioned on and in contact with the support surface. In an embodiment, the solvent can be applied to tool 30 before application to the object holder and can be applied to the object holder before the tool 30 is contact with the object holder.

[0076] In addition to the above described use of the abrasion tool 30, the abrasion tool 30 or another similar abrasion tool can be used on the object holder to roughen at least part of a support surface of the object holder. In an embodiment, it is used to roughen a top or upper surface of a projection, such as a projection 20, of the object holder. In an embodiment, this use of an abrasion tool can be after contamination is removed from the support surface using, e.g., tool 30. Increasing the surface roughness decreases the contact area of the support surface with the supported object (e.g. decreasing the contact area of projections 20 in contact with the (bottom) surface of the substrate W), thus improving friction between an object placed on the surface and so, e.g., reducing or eliminating load grid error.

[0077] In an embodiment, the roughening can be accomplished using a different surface of the abrasion tool 30. For example, a backside surface (with respect to surface 32) of the abrasion tool 30 could be used, wherein the backside surface has the appropriate characteristics for the roughening. In an embodiment, a different abrasion tool 30 can be provided with appropriate characteristics for roughening of surface 32. Reference hereinafter will be to the use of a second abrasion tool, but the same considerations can be applied to a backside (or other surface) of an abrasion tool 32 used for cleaning.

[0078] The second abrasion tool for roughening may have similar characteristics and features as noted above with respect to the abrasion tool 30 for cleaning. For example, the second abrasion tool for roughening may have a substantially flat abrasion surface configured to be positioned on and in contact with the object holder, such that there can be relative movement between the second abrasion tool and a support surface of the object holder while in contact with the support surface to roughen at least part of the support surface (e.g., roughen a top surface of a projection). In an embodiment, the roughening surface of the second abrasion tool for roughening is configured to be brought into contact with the upper surface of at least the projections (e.g., the projections 20) of the object holder.

[0079] The second abrasion tool may have similar physical features as discussed in detail above with regards to the abrasion tool 30 for cleaning. For example, its body and surface may be integral or separate, and formed from homogeneous, non-natural (artificially made or manmade) material. The shape and form of the tool and/or its surface that contacts an object holder support surface (herein a contact surface of the tool), the cross-wise dimension and thickness (such as shown and described above with reference to FIG. 6) are also not limited and may be similar to the features noted above, and thus are not repeated here. Similarly, the second abrasion tool for roughening may be utilized in a similar manner as discussed in relation to FIG. 7, e.g., moved in a series of passes and/or wetted with solvent during use.

[0080] Further, in an embodiment, at least the contact surface of the tool 30 is made of a stone, granite, or ceramic material. In an embodiment, that surface comprises or consists essentially of a material selected from: aluminum oxide (AI2O3), silicon carbide (SiC), silicon nitride (S13N4), aluminum nitride (AIN), and/or chromium nitride (CrN).

[0081] But, in a difference from the abrasion tool 30 for cleaning, the roughness of the contact surface of the second abrasion tool is different from the roughness of the surface 32 of the abrasion tool 30. For example, in an embodiment, the surface of the second abrasion tool may have a roughness of at least about 100 nm Ra, or at least about 150 nm Ra or at least about 200 nm Ra. In an embodiment, the roughness of the contact surface of the second abrasion tool is selected from the range of about 100 nm Ra to about 3000 nm Ra, from the range of about 100 nm to about 1200 nm Ra, or from the range of about 150 nm to about 500 nm Ra.

[0082] In an embodiment, the contact surface of the second abrasion tool falls within the same general flatness criteria as surface 32 of abrasion tool 30. hi an embodiment, the flatness can be selected from the range of about 400 nm to about 3000 nm for roughness from the range of about 100 nm to 2000 nm. In an embodiment, the contact surface of the second abrasion tool falls within the same hardness criteria as surface 32 of abrasion tool 30.

[0083] Example [0084] For testing purposes, two AI2O3 stones of 30 nm Ra roughness and 200 nm Ra roughness respectively (50 mm dia., 15 mm thick) were obtained. Methanol was sprayed on top of a clamp or support table. The 30 nm stone was placed on the top of the clamp / table and without adding any normal force, it was moved from the left to right and back to front to cover the entire area of the clamp / table. The 30 nm stone was cleaned and kept wetted with methanol after each couple of passes. Overall the clamp / table was globally stoned for six times and between every stoning the clamp was wiped with tissue. FIG. 8 is a detailed, close up view of a projection on the clamp / table with contamination thereon, before moving the 30 nm Ra stone across the clamp / table. After cleaning with the 30 nm Ra stone as described above, a significant amount of the contamination was removed from the projection, as shown in FIG. 9. The 30 Ra nm stone thus removed stubborn contamination which cannot be removed by a standard cleaning method, and yet did not significantly change the flatness of the clamp / table.

[0085] Then, to roughening the projection tops, the 200 nm Ra stone was applied in the same manner as the 30 nm Ra stone. This increased the number of scratches on the support surfaces of the projection tops; thus, the contact area of the projection tops with the substrate will be smaller by effectively creating mini-projections on the projections, when the substrate is placed on the projections. Due to the lower contact area, the friction coefficient is lower and the load grid error can reduced and/or eliminated.

[0086] After completing these steps in this example, it was observed that a load grid error of 8 nm was decreased to 0.2 nm. Further, the friction after roughening with the 200 nm Ra stone was still sufficient to enable the projections to hold the substrate when moved in a direction essentially parallel to the plane of the support surfaces of the projections.

[0087] As such, this disclosure provides tools and a method for removing or cleaning stubborn nm or sub-micrometer contamination on an object holder surface, such as a projection top surface, without causing damage (e.g., rounding or breaking the projections) or significantly changing the flatness of the object holder. Additionally or alternatively, this disclosure provides tools and a method for roughening an object holder surface, such as a projection top surface, without causing damage (e.g., rounding or breaking the projections) or significantly changing the flatness of the object holder. The cleaning and/or roughening process is readily implemented in existing processes while also capable of producing consistent results.

[0088] In an embodiment, the disclosed method and tool(s) may be used after standard cleaning step(s) of the object holder are implemented, including, for example, after removal of large particles from the surface of the object holder, after wiping the object holder with a tissue or fibrous cloth, after stamping the object holder using, for example, a substrate (e.g., a substrate as typically used for device manufacture such as a silicon substrate and that can optionally be treated with, for example, a coating to promote adherence of contamination to the substrate), etc. [0089] Although not depicted in the Figures, it should be understood that the disclosed one or more tools and/or method may further be associated with one or more systems to be used concurrently or cooperatively with the cleaning method and devices disclosed herein. For example, in an embodiment, a contamination detection unit with one or more sensors therein may be provided to detect contamination on the surface of the object holder and/or its projections. Also, in an embodiment, a controller may be provided for communication with the contamination detection unit, e.g., to control a position of a detecting portion of the contamination detection unit and/or to sense or determine an amount of contamination, based on a result of the detection using the contamination detection unit.

[0090] In an embodiment, there is provided a method of processing a support surface of a holder configured to hold an object, the object holder comprising a plurality of protrusions, the protrusions extending from a body of the holder and configured to provide a support surface for the object, the method comprising: providing an abrasion tool comprising a substantially flat surface for positioning on and in contact with the object holder; positioning the substantially flat surface of the abrasion tool in contact with the support surface of the object holder; and providing relative movement between the abrasion tool and at least part of the object holder while the abrasion tool is in contact with the support surface to remove contamination from the protrusions, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 15 nm Ra to about 50 nm Ra, has a flatness of less than or equal to about 500 nm within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface.

[0091] In an embodiment, the substantially flat surface of the abrasion tool has a roughness selected from the range of about 15 nm Ra to about 50 nm Ra. In an embodiment, the substantially flat surface of the abrasion tool has a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface. In an embodiment, the predetermined area has flatness per unit crosswise dimension of the predetermined area of less than or equal to about 150 nm/cm within the predetermined area. In an embodiment, the method further comprises wetting a contact area of the substantially flat surface of the abrasion tool and the support surface with a solvent. In an embodiment, the wetting comprises applying the solvent to the substantially flat surface of the abrasion tool before the positioning of the abrasion tool in contact with the support surface and/or the wetting comprises applying the solvent to the support surface before the positioning of the abrasion tool in contact with the support surface. In an embodiment, the method further comprises positioning a contact surface of the abrasion tool that is other than the substantially flat surface or of another abrasion tool, in contact with the support surface of the object holder, wherein the contact surface is substantially flat; and providing relative movement between the contact surface and at least part of the object holder while the contact surface is in contact with the support surface to roughen a portion of the support surface, wherein the contact surface has a roughness of at least about 200 nm Ra. In an embodiment, the contact surface has a flatness of less than or equal to about 500 nm within a predetermined area of the contact surface. In an embodiment, the method further comprises wetting a contact area of the contact surface and the support surface with a solvent. In an embodiment, the wetting comprises applying the solvent to the contact surface before the positioning of the contact surface in contact with the support surface and/or the wetting comprises applying the solvent to the support surface before the positioning of the contact surface in contact with the support surface. In an embodiment, an abrasion tool surface in contact with the support surface comprises a material having a hardness greater than about 10 GPa. In an embodiment, the hardness is selected from a range of about 10 GPa to about 30 GPa. In an embodiment, the relative movement comprises sliding the abrasion tool back and forth across the support surface in a series of successive passes, each respective pass in the series being in an opposite direction to a previous pass in the series. In an embodiment, the method further comprises sliding the abrasion tool in a plurality of series of successive passes and wiping the support surface between each series of successive passes. In an embodiment, the relative movement is performed at least in part manually by a person. In an embodiment, the relative movement is performed at least part by a machine or robotic ami. In an embodiment, the abrasion tool comprises a stone or ceramic material.

[0092] In an embodiment, there is provided an abrasion tool configured to be positioned on and in contact with an object holder comprising a plurality of protrusions providing a support surface for an object, the abrasion tool comprising a substantially flat surface arranged to abrade the support surface by relative movement between the substantially flat surface and the support surface to remove contamination from the support surface, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 15 nm Ra to about 50 nm Ra, has a flatness of less than or equal to about 500 nm within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface.

[0093] In an embodiment, the substantially flat surface of the abrasion tool has a roughness selected from the range of about 15 nm Ra to about 50 nm Ra. In an embodiment, the substantially flat surface of the abrasion tool has a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface.

[0094] In an embodiment, there is provided an abrasion tool configured to be positioned on and in contact with an object holder comprising a plurality of protrusions providing a support surface for an object, the abrasion tool comprising a substantially flat surface arranged to abrade the support surface by relative movement between the substantially flat surface and the support surface to roughen the support surface, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 200 nm Ra to about 500 nm Ra.

[0095] In an embodiment, the substantially flat surface of the abrasion tool has a flatness of less than or equal to about 500 nm within a predetermined area of the substantially flat surface. [0096] In an embodiment, there is provided a lithographic apparatus comprising: a patterning device support configured to support a patterning device, the patterning device configured to pattern a beam of radiation to form a patterned beam of radiation; a projection system configured to project the patterned beam of radiation onto a target portion of a substrate; a substrate holder configured to hold a substrate; a system arranged to remove contamination from a support surface of an object holder comprising a plurality of protrusions to provide a support surface for an object, the system comprising an abrasion tool comprising a substantially flat surface for positioning on and in contact with the object holder, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 15 nm Ra to about 50 nm Ra, has a roughness selected from the range of about 200 nm Ra to about 500 nm Ra, has a flatness of less than or equal to about 500 nm within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface.

[00971 In an embodiment, the object holder is the substrate holder or the patterning device support.

[0098] FIG. 10 is a block diagram that illustrates a computer system 100 which can assist in implementing methods and flows disclosed herein. Computer system 100 includes a bus 102 or other communication mechanism to communicate information, and a processor 104 (or multiple processors 104 and 105) coupled with bus 102 to process information. Computer system 100 may also include a main memory 106, such as a random access memory (RAM) or other dynamic storage device, coupled to bus 102 to store or supply information and instructions to be executed by processor 104. Main memory 106 may be used to store or supply temporary variables or other intermediate information during execution of instructions to be executed by processor 104. Computer system 100 may further include a read only memory (ROM) 108 or other static storage device coupled to bus 102 to store or supply static information and instructions for processor 104. A storage device 110, such as a magnetic disk or optical disk, may be provided and coupled to bus 102 to store or supply information and instructions.

[0099] Computer system 100 may be coupled via bus 102 to a display 112, such as a cathode ray tube (CRT) or flat panel or touch panel display, to display information to a computer user. An input device 114, including alphanumeric and other keys, may be coupled to bus 102 to communicate information and command selections to processor 104. Another type of user input device may be cursor control 116, such as a mouse, a trackball, or cursor direction keys, to communicate direction information and command selections to processor 104 and to control cursor movement on display 112. This input device typically has two degrees of freedom in two axes, a first axis (e.g., x) and a second axis (e.g., y), that allows the device to specify positions in a plane. A touch panel (screen) display may also be used as an input device.

[00100] According to an embodiment, portions of a process described herein may be performed by computer system 100 in response to processor 104 executing one or more sequences of one or more instructions contained in main memory 106. Such instructions may be read into main memory 106 from another computer-readable medium, such as storage device 110. Execution of the sequences of instructions contained in main memory 106 causes processor 104 to perform the process steps described herein. One or more processors in a multi-processing arrangement may be employed to execute the sequences of instructions contained in main memory 106. In an alternative embodiment, hard-wired circuitry may be used in place of or in combination with software instructions. Thus, the description herein is not limited to any specific combination of hardware circuitry and software.

[00101] The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to processor 104 for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical or magnetic disks, such as storage device 110. Volatile media include dynamic memory, such as main memory 106. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise bus 102. Transmission media can also take the form of acoustic or light waves, such as those generated during radio frequency (RF) and infrared (IR) data communications. Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, any other magnetic medium, a CD-ROM, DVD, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read.

[00102] Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor 104 for execution. For example, the instructions may initially be borne on a disk or memory of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a communications path. Computer system 100 can receive the data from the path and place the data on bus 102. Bus 102 carries the data to main memory 106, from which processor 104 retrieves and executes the instructions. The instructions received by main memory 106 may optionally be stored on storage device 110 either before or after execution by processor 104. [00103] Computer system 100 may include a communication interface 118 coupled to bus 102. Communication interface 118 provides a two-way data communication coupling to a network link 120 that is connected to a network 122. For example, communication interface 118 may provide a wired or wireless data communication connection. In any such implementation, communication interface 118 sends and receives electrical, electromagnetic or optical signals that cany digital data streams representing various types of information.

[00104] Network link 120 typically provides data communication through one or more networks to other data devices. For example, network link 120 may provide a connection through network 122 to a host computer 124 or to data equipment operated by an Internet Service Provider (ISP) 126. ISP 126 in turn provides data communication services through the worldwide packet data communication network, now commonly referred to as the “Internet” 128. Network 122 and Internet 128 both use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network link 120 and through communication interface 118, which carry the digital data to and from computer system 100, are exemplary forms of carrier waves transporting the information. [00105] Computer system 100 can send messages and receive data, including program code, through the network(s), network link 120, and communication interface 118. In the Internet example, a server 130 might transmit a requested code for an application program through Internet 128, ISP 126, network 122 and communication interface 118. One such downloaded application may provide the code to implement, e.g., a method herein. The received code may be executed by processor 104 as it is received, or stored in storage device 110, or other non-volatile storage for later execution. Computer system 100 may obtain code in the form of a earner wave. [00106] Although specific reference may be made in this text to the manufacture of ICs, it should be explicitly 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, flat-panel displays, liquid-crystal displays (LCDs), micro-electro mechanical systems (MEMS), thin film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion, respectively.

[00107] The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), an etching tool, a chemical mechanical planarization (CMP) tool, a metrology tool and/or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains multiple processed layers.

[00108] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications, for example imprint lithography, and where the context allows, is not limited to optical lithography. In imprint lithography a topography in a patterning device defines the pattern created on a substrate. The topography of the patterning device may be pressed into a layer of resist supplied to the substrate whereupon the resist is cured by applying electromagnetic radiation, heat, pressure or a combination thereof. The patterning device is moved out of the resist leaving a pattern in it after the resist is cured.

[00109] The lithographic apparatus may also be of a type wherein a surface of the substrate is immersed in a liquid having a relatively high refractive index, e.g. water, so as to fill a space between a final element of the projection system and the substrate. Immersion liquid may be applied to other spaces in the lithographic apparatus, for example, between the patterning device and a first element of the projection system. Immersion techniques are known in the art for increasing the numerical aperture of projection systems.

[00110] The terms “radiation” and “beam” used herein encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g. having a wavelength of or about 365, 248, 193, 157 or 126 nm) and extreme ultra-violet (EUV) radiation (e.g. having a wavelength in the range of 5-20 nm), as well as particle beams, such as ion beams or electron beams.

[00111] The term “lens”, where the context allows, may refer to any one or combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components.

[00112] In block diagrams, illustrated components are depicted as discrete functional blocks, but embodiments are not limited to systems in which the functionality described herein is organized as illustrated. The functionality provided by each of the components may be provided by software or hardware modules that are differently organized than is presently depicted, for example such software or hardware may be intermingled, conjoined, replicated, broken up, distributed (e.g. within a data center or geographically), or otherwise differently organized. The functionality described herein may be provided by one or more processors of one or more computers executing code stored on a tangible, non-transitory, machine readable medium. In some cases, third party content delivery networks may host some or all of the information conveyed over networks, in which case, to the extent information (e.g., content) is said to be supplied or otherwise provided, the information may be provided by sending instructions to retrieve that information from a content delivery network.

[00113] Unless specifically stated otherwise, as apparent from the discussion, it is appreciated that throughout this specification discussions utilizing terms such as “processing,” “computing,” “calculating,” “determining” or the like refer to actions or processes of a specific apparatus, such as a special purpose computer or a similar special purpose electronic processing/computing device.

[00114] The reader should appreciate that the present application describes several inventions. Rather than separating those inventions into multiple isolated patent applications, these inventions have been grouped into a single document because their related subject matter lends itself to economies in the application process. But the distinct advantages and aspects of such inventions should not be conflated. In some cases, embodiments address all of the deficiencies noted herein, but it should be understood that the inventions are independently useful, and some embodiments address only a subset of such problems or offer other, unmentioned benefits that will be apparent to those of skill in the art reviewing the present disclosure. Due to costs constraints, some inventions disclosed herein may not be presently included in clauses and may be included in clauses in later filings, such as continuation applications or by amending the present clauses. Similarly, due to space constraints, neither the Abstract nor the Summary sections of the present document should be taken as containing a comprehensive listing of all such inventions or all aspects of such inventions.

[00115] It should be understood that the description and the drawings are not intended to limit the present disclosure to the particular form disclosed, but to the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the inventions as defined by the appended clauses.

[00116] Modifications and alternative embodiments of various aspects of the inventions will be apparent to those skilled in the art in view of this description. Accordingly, this description and the drawings are to be construed as illustrative only and are for the purpose of teaching those skilled in the art the general manner of carrying out the inventions. It is to be understood that the forms of the inventions shown and described herein are to be taken as examples of embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed or omitted, certain features may be utilized independently, and embodiments or features of embodiments may be combined, all as would be apparent to one skilled in the art after having the benefit of this description. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following clauses. Headings used herein are for organizational puiposes only and are not meant to be used to limit the scope of the description.

[00117] As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). The words “include”, “including”, and “includes” and the like mean including, but not limited to. As used throughout this application, the singular forms “a,” “an,” and “the” include plural referents unless the content explicitly indicates otherwise. Thus, for example, reference to “an” element or a” element includes a combination of two or more elements, notwithstanding use of other terms and phrases for one or more elements, such as “one or more.” The term or is, unless indicated otherwise, non-exclusive, i.e., encompassing both and and or. Terms describing conditional relationships, e.g., in response to X, Y, upon X, Y,, “if X, Y,” when X, Y, and the like, encompass causal relationships in which the antecedent is a necessary causal condition, the antecedent is a sufficient causal condition, or the antecedent is a contributory causal condition of the consequent, e.g., state X occurs upon condition Y obtaining is generic to X occurs solely upon Y and X occurs upon Y and Z. Such conditional relationships are not limited to consequences that instantly follow the antecedent obtaining, as some consequences may be delayed, and in conditional statements, antecedents are connected to their consequents, e.g., the antecedent is relevant to the likelihood of the consequent occurring. Statements in which a plurality of attributes or functions are mapped to a plurality of objects (e.g., one or more processors performing steps A, B, C, and D) encompasses both all such attributes or functions being mapped to all such objects and subsets of the attributes or functions being mapped to subsets of the attributes or functions (e.g., both all processors each performing steps A-D, and a case in which processor 1 performs step A, processor 2 performs step B and part of step C, and processor 3 performs part of step C and step D), unless otherwise indicated. Further, unless otherwise indicated, statements that one value or action is “based on” another condition or value encompass both instances in which the condition or value is the sole factor and instances in which the condition or value is one factor among a plurality of factors. Unless otherwise indicated, statements that “each” instance of some collection have some property should not be read to exclude cases where some otherwise identical or similar members of a larger collection do not have the property, i.e., each does not necessarily mean each and every. References to selection from a range includes the end points of the range.

[00118] In the above description, any processes, descriptions or blocks in flowcharts should be understood as representing modules, segments or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process, and alternate implementations are included within the scope of the exemplary embodiments of the present advancements in which functions can be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending upon the functionality involved, as would be understood by those skilled in the art.

[00119] While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the present disclosures. Indeed, the novel methods, apparatuses and systems described herein can be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods, apparatuses and systems described herein can be made without departing from the spirit of the present disclosures. The accompanying clauses and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the present disclosures. Other aspects of the invention are set out as in the following numbered clauses.

1. A method of processing a support surface of a holder configured to hold an object, the object holder comprising a plurality of protrusions, the protrusions extending from a body of the holder and configured to provide a support surface for the object, the method comprising:

providing an abrasion tool comprising a substantially flat surface for positioning on and in contact with the object holder;

positioning the substantially flat surface of the abrasion tool in contact with the support surface of the object holder; and providing relative movement between the abrasion tool and at least part of the object holder while the abrasion tool is in contact with the support surface to remove contamination from the protrusions, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 1 nm Ra to about 100 nm Ra, has a flatness of less than or equal to about 3000 nm within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 3000 nm within the predetermined area of the substantially flat surface.

2. The method of clause I, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 1 nm Ra to about 100 nm Ra.

3. The method of clause 1 or clause 2, wherein the substantially flat surface of the abrasion tool has a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface.

4. The method of any of clauses 1-3, wherein the predetermined area has flatness per unit crosswise dimension of the predetermined area of less than or equal to about 150 nm/cm within the predetermined area.

5. The method of any of clauses 1-4, further comprising wetting a contact area of the substantially flat surface of the abrasion tool and the support surface with a solvent.

6. The method of clause 5, wherein the wetting comprises applying the solvent to the substantially flat surface of the abrasion tool before the positioning of the abrasion tool in contact with the support surface and/or the wetting comprises applying the solvent to the support surface before the positioning of the abrasion tool in contact with the support surface.

7. The method of any of clauses 1-6, further comprising:

positioning a contact surface of the abrasion tool that is other than the substantially flat surface or of another abrasion tool, in contact with the support surface of the object holder, wherein the contact surface is substantially flat; and providing relative movement between the contact surface and at least part of the object holder while the contact surface is in contact with the support surface to roughen a portion of the support surface, wherein the contact surface has a roughness of at least about 100 nm Ra.

8. The method of clause 7, wherein the contact surface has a flatness of less than or equal to about 3000 nm within a predetermined area of the contact surface.

9. The method of clause 7 or clause 8, further comprising wetting a contact area of the contact surface and the support surface with a solvent.

10. The method of clause 9, wherein the wetting comprises applying the solvent to the contact surface before the positioning of the contact surface in contact with the support surface and/or the wetting comprises applying the solvent to the support surface before the positioning of the contact surface in contact with the support surface.

11. The method of any of clauses 1-10, wherein an abrasion tool surface in contact with the support surface comprises a material having a hardness greater than about 10 GPa.

12. The method of clause 11, wherein the hardness is selected from a range of about 10 GPa to about 30 GPa.

13. The method of any of clauses 1-12, wherein the abrasion tool comprises a stone or ceramic material.

14. An abrasion tool configured to be positioned on and in contact with an object holder comprising a plurality of protrusions providing a support surface for an object, the abrasion tool comprising a substantially flat surface arranged to abrade the support surface by relative movement between the substantially flat surface and the support surface to remove contamination from the support surface, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 1 nm Ra to about 100 nm Ra, has a flatness of less than or equal to about 3000 nm within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 3000 nm within the predetermined area of the substantially flat surface.

15. The abrasion tool of clause 14, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 15 nm Ra to about 50 nm Ra.

16. The abrasion tool of clause 14 or clause 15, wherein the substantially flat surface of the abrasion tool has a flatness of less than or equal to about 500 nm within the predetermined area of the substantially flat surface.

17. An abrasion tool configured to be positioned on and in contact with an object holder comprising a plurality of protrusions providing a support surface for an object, the abrasion tool comprising a substantially flat surface arranged to abrade the support surface by relative movement between the substantially flat surface and the support surface to roughen the support surface, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 100 nm Ra to about 2000 nm Ra.

18. The abrasion tool of clause 17, wherein the substantially flat surface of the abrasion tool has a flatness of less than or equal to about 3000 nm within a predetermined area of the substantially flat surface.

19. A lithographic apparatus comprising:

a patterning device support configured to support a patterning device, the patterning device configured to pattern a beam of radiation to form a patterned beam of radiation;

a projection system configured to project the patterned beam of radiation onto a target portion of a substrate;

a substrate holder configured to hold a substrate;

a system arranged to remove contamination from a support surface of an object holder comprising a plurality of protrusions to provide a support surface for an object, the system comprising an abrasion tool comprising a substantially flat surface for positioning on and in contact with the object holder, wherein the substantially flat surface of the abrasion tool has a roughness selected from the range of about 1 nm Ra to about 100 nm Ra, has a roughness selected from the range of about 200 nm Ra to about 2000 nm Ra, has a flatness of less than or equal to about 3000 nm within a predetermined area of the substantially flat surface, or has a roughness of at least about 15 nm Ra and a flatness of less than or equal to about 3000 nm within the predetermined area of the substantially flat surface.

20. The apparatus of clause 19, wherein the object holder is the substrate holder or the patterning device support.

Claims

CONCLUSION

A lithography apparatus comprising:

an illumination device adapted to provide a radiation beam;

5 a carrier constructed for supporting a patterning device, which patterning device is capable of applying a pattern in a section of the radiation beam to form a patterned radiation beam;

a substrate table constructed to support a substrate; and a projection device adapted to project the patterned radiation beam onto

10 is a target area of the substrate, characterized in that the substrate table is adapted to position the target area of the substrate in a focal plane of the projection device.