Lithography apparatus, substrate table and method

Abstract

A substrate table for supporting a substrate includes a surface and a bulged stub. Each of the thick tabs includes a tab top surface and a thin tab. The thick tabs are disposed on a surface of the substrate table and the thin tabs are disposed on a top surface of the tabs. When the substrate table supports the substrate, the fine bumps are in contact with the substrate.

Description

[0001] This application is a divisional application of the original Chinese invention patent application with the invention name “Photolithography apparatus, substrate stage and method”, application number 202080038409.6 and application date May 5, 2020.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Provisional Patent Application No. 62 / 852,578, filed on May 24, 2019, which is hereby incorporated by reference in its entirety. Technical Field

[0004] The present disclosure relates to substrate tables, textured table surfaces, and methods of employing burls and nanostructures on substrate table surfaces. Background Art

[0005] A lithographic apparatus is a machine that applies a desired pattern to a substrate (usually, to a target portion of a substrate). A lithographic apparatus can be used, for example, in the manufacture of an integrated circuit (IC). In this example, a pattern forming device (optionally referred to as a mask or a reticle) can be used to generate a circuit pattern to be formed on a single layer of an IC. The pattern can be transferred to a target portion (e.g., including a portion of a die, a die, or multiple dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is usually performed via imaging on a radiation-sensitive material (resist) layer provided on the substrate. Typically, a single substrate will include a network of adjacent target portions that are patterned continuously. Known lithographic apparatuses include: a so-called stepper, in which each target portion is irradiated by exposing the entire pattern to the target portion at one time; and a so-called scanner, in which the pattern is scanned by a radiation beam along a given direction ("scanning" direction), while simultaneously scanning the substrate in parallel or antiparallel to the scanning direction to irradiate each target portion. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0006] Another lithography system is an interference lithography system in which there is no patterning device, but rather the beam is split into two beams and the two beams are caused to interfere at a target portion of the substrate using a reflection system. The interference causes a line to be formed at the target portion of the substrate.

[0007] During a lithography operation, different process steps may require that different layers be sequentially formed on a substrate. Therefore, it is necessary to position the substrate with high accuracy relative to a previous pattern formed thereon. Typically, alignment marks are placed on the substrate to be aligned and positioned with reference to a second object. The lithography apparatus may use an alignment device to detect the position of the alignment marks and align the substrate using the alignment marks to ensure accurate exposure from the mask. The misalignment between alignment marks of two different layers is measured as overlay error.

[0008] In order to monitor the lithography process, the parameters of the patterned substrate are measured. The parameters may include, for example, the overlay error between successive layers formed in or on the patterned substrate, and the critical line width of the developed photoresist. The measurement may be performed on a product substrate and / or on a dedicated metrology target. There are a variety of techniques for measuring the microstructures formed in the lithography process, including the use of scanning electron microscopes and various dedicated tools. A fast and non-invasive form of a dedicated inspection tool is a scatterometer, in which a radiation beam is directed to a target on the substrate surface, and the characteristics of the scattered or reflected beam are measured. By comparing the characteristics of the beam before and after being reflected or scattered by the substrate, the characteristics of the substrate can be determined. This can be done, for example, by comparing the reflected beam with data stored in a known measurement library associated with known substrate characteristics. A spectral scatterometer directs a broadband radiation beam onto a substrate and measures the spectrum (intensity as a function of wavelength) of the radiation scattered into a specific narrow angle range. In contrast, an angularly resolved scatterometer uses a monochromatic radiation beam and measures the intensity of the scattered radiation as a function of angle.

[0009] Such optical scatterometers can be used to measure parameters such as the critical dimension of a developed photoresist or the overlay error (OV) between two layers formed in or on a patterned substrate. The properties of a substrate can be determined by comparing the properties of an irradiated beam before and after the beam is scattered by reflection from the substrate.

[0010] It is desirable to specify and maintain tribological properties (e.g., friction, hardness, wear) on the surface of a substrate table. Due to the precise demands of lithography and metrology processes, substrate tables have surface level tolerances that are difficult to meet. Wafers (e.g., semiconductor substrates), which are relatively thin (e.g., <1 mm thick) compared to the width of their surface area (e.g., >100 mm), are particularly sensitive to unevenness of the substrate table. In addition, ultra-smooth surfaces in contact may become "sticky" together, which may cause problems when the substrate must be released from the substrate table. It is desirable to develop structures and methods for substrate tables that allow for increased wear resistance and tribological properties that facilitate engaging and releasing the substrate on command. Summary of the invention

[0011] In some embodiments, a substrate table for supporting a substrate includes a surface and a thick burl. Each of the thick burls includes a burl top surface and a thin burl. The thick burl is disposed on the surface of the substrate table. The thin burl is disposed on the burl top surface and is configured to contact the substrate when the substrate table supports the substrate.

[0012] In some embodiments, a lithographic apparatus comprises an illumination system, a support, a projection system, and a substrate table. The substrate table comprises a surface and a thick burl. Each of the thick burls comprises a burl top surface and a thin burl. The thick burl is disposed on the surface of the substrate table. The thin burl is disposed on the burl top surface and is configured to contact the substrate when the substrate table supports the substrate. The illumination system is configured to generate a radiation beam. The support is configured to support a pattern forming device to impart a pattern to the beam. The projection system is configured to project the patterned beam onto the substrate.

[0013] In some embodiments, a method for manufacturing a substrate table includes supporting the substrate table to receive a manufacturing process, and manufacturing thick burls and thin burls on the substrate table. Manufacturing the thick burls and thin burls includes providing the thin burls on the burl top surface of the thick burls.

[0014] Other features and beneficial effects of the present invention and the structure and operation of various embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are shown herein for illustrative purposes only. Based on the teachings contained herein, additional embodiments will be apparent to those skilled in the relevant art. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and enable one skilled in the relevant art to make and use the invention.

[0016] Figure 1A A schematic diagram of a reflective lithography apparatus according to some embodiments is shown.

[0017] Figure 1B A schematic diagram of a transmission lithography apparatus according to some embodiments is shown.

[0018] Figure 2 A more detailed schematic diagram of a reflective lithography apparatus according to some embodiments is shown.

[0019] Figure 3 A schematic diagram of a lithography cell according to some embodiments is shown.

[0020] Figure 4 A schematic diagram of a substrate platform is shown in accordance with some embodiments.

[0021] Figure 5 A schematic cross-sectional view of a region of a substrate table according to some embodiments is shown.

[0022] Figure 6 A graph showing burl top surface contact area versus clamping pressure according to some embodiments.

[0023] Figure 7 A schematic diagram showing a cross section of a substrate table region according to some embodiments is shown.

[0024] Figure 8 Method steps for manufacturing a substrate table according to some embodiments are shown.

[0025] Features and benefits of the present invention will become more apparent from the following detailed description in conjunction with the accompanying drawings, in which like reference symbols identify corresponding elements throughout the text. In the accompanying drawings, like reference numerals generally indicate identical, functionally similar, and / or structurally similar elements. In addition, generally, the leftmost digit of a reference numeral identifies the drawing in which the reference numeral first appears. Unless otherwise specified, the drawings provided throughout this disclosure should not be construed as drawings drawn to scale. DETAILED DESCRIPTION

[0026] This specification discloses one or more embodiments incorporating features of the present invention. The disclosed embodiments merely illustrate the present invention. The scope of the present invention is not limited to the disclosed embodiments. The present invention is defined by the appended claims.

[0027] The described embodiments and references in this specification to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiments may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it should be understood that it is within the knowledge of a person skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0028] Spatially relative terms, such as "beneath," "below," "lower," "above," "on," "upper," etc., may be used herein to describe the relationship of one element or feature to another element or feature as shown in the figures. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0029] As used herein, the term "approximately" indicates a value of a given quantity that may vary based on a particular technology. Based on a particular technology, the term "approximately" may represent a value of a given quantity that varies within, for example, 10%-30% of the value (e.g., ±10%, ±20%, or ±30% of the value).

[0030] However, before describing these embodiments in more detail, it is helpful to provide an example environment in which embodiments of the present disclosure may be implemented.

[0031] Example Lithography System

[0032] Figure 1A 1B and 1B show schematic illustrations of lithographic apparatus 100 and lithographic apparatus 100', respectively, in which embodiments of the present disclosure may be implemented. Each of lithographic apparatus 100 and lithographic apparatus 100' includes the following: an illumination system (illuminator) IL configured to condition a radiation beam B (e.g., deep ultraviolet or extreme ultraviolet radiation); a support structure (e.g., a mask stage) MT configured to support a pattern forming device (e.g., a mask, a reticle, or a dynamic pattern forming device) MA and connected to a first positioner PM configured to accurately position the pattern forming device MA; and a substrate stage (e.g., a wafer stage) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate W. The lithographic apparatus 100 and 100' also have a projection system PS configured to project a pattern imparted to the radiation beam B by the pattern forming device MA onto a target portion (e.g., including one or more dies) C of the substrate W. In lithographic apparatus 100, patterning device MA and projection system PS are reflective. In lithographic apparatus 100', patterning device MA and projection system PS are transmissive.

[0033] The illumination system IL may include different types of optical elements for directing, shaping or controlling the radiation beam B, such as refractive, reflective, catadioptric, magnetic, electromagnetic, electrostatic or other types of optical components or combinations thereof.

[0034] The support structure MT holds the patterning device MA in a manner that depends on the orientation of the patterning device MA relative to the reference frame, the design of at least one of the lithographic apparatuses 100 and 100', and other conditions (such as whether the patterning device MA is held in a vacuum environment). The support structure MT may use mechanical, vacuum, electromagnetic or other clamping techniques to hold the patterning device MA. The support structure MT may be, for example, a frame or table that may be fixed or movable, as desired. By using sensors, the support structure MT may ensure that the patterning device MA is in a desired position, for example relative to the projection system PS.

[0035] 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 so as to create a pattern in a target portion C of the substrate W. The pattern imparted to the radiation beam B may correspond to a specific functional layer in the device being created in the target portion C to form an integrated circuit.

[0036] The pattern forming device MA can be a transmissive type (such as Figure 1B ) or a reflective type (such as Figure 1A 100). Examples of pattern forming devices MA include reticles, masks, programmable mirror arrays, or programmable LCD panels. Masks are known in lithography and include mask types such as binary, alternating phase shift, or attenuated phase shift, as well as various hybrid mask types. Examples of programmable mirror arrays employ a matrix arrangement of small mirrors, each of which can be individually tilted to reflect an incident radiation beam in different directions. The tilted mirrors impart a pattern into a radiation beam B, which is reflected by the matrix of small mirrors.

[0037] The term "projection system" may cover 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 used and / 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 may be used for EUV or electron beam radiation, as other gases may absorb too much radiation or electrons. Therefore, a vacuum environment may be provided to the entire beam path by means of vacuum walls and a vacuum pump.

[0038] The lithographic apparatus 100 and / or lithographic apparatus 100' may be of a type having two (dual stage) or more substrate tables WT (and / or two or more mask tables). In such "multi-stage" machines, additional substrate tables may be used in parallel, or preparatory steps may be performed on one or more tables while one or more other substrate tables WT are being used for exposure. In some cases, the additional tables may not be substrate tables WT.

[0039] The lithographic apparatus may also be of a type in which at least a portion of the substrate may be covered by a liquid having a relatively high refractive index (e.g., water) to fill the space between the projection system and the substrate. Immersion liquid may also be applied to other spaces in the lithographic apparatus, for example, between the mask and the projection system. Immersion techniques are well known in the art to increase the numerical aperture of the projection system. The term "immersion" as used herein does not mean that a structure (such as a substrate) must be immersed in the liquid, but only means that the liquid is located between the projection system and the substrate during exposure.

[0040] refer to Figure 1A and 1B , the illuminator IL receives a radiation beam from a radiation source SO. For example, when the source SO is an excimer laser, the source SO and the lithographic apparatus 100, 100' may be separate physical entities. In this case, the source SO is not considered to form part of the lithographic apparatus 100 or 100', and the radiation beam B is delivered to the lithographic apparatus 100 or 100' by means of a beam delivery system BD (in Figure 1B The radiation is delivered from the source SO to the illuminator IL (including, for example, suitable guide mirrors and / or a beam expander). In other cases, for example, when the source SO is a mercury lamp, the source SO may be an integral part of the lithographic apparatus 100, 100'. The source SO and the illuminator IL (together with the beam delivery system BD, if necessary) may be referred to as a radiation system.

[0041] The illuminator IL may comprise an adjuster AD (at Figure 1B In general, 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. Furthermore, the illuminator IL may include various other components (in Figure 1B ), such as an integrator IN and a condenser CO. The illuminator IL may be used to condition the radiation beam B to have a desired uniformity and intensity distribution in its cross-section.

[0042] refer to Figure 1A, a radiation beam B is incident on and patterned by a patterning device (e.g., a mask) MA, which is held on a support structure (e.g., a mask table) MT. In the lithographic apparatus 100, the radiation beam B is reflected from the patterning device (e.g., a mask) MA. After reflection from the patterning device (e.g., a mask) MA, the radiation beam B passes through a projection system PS, which focuses the radiation beam B onto a target portion C of a substrate W. With the aid of a second positioner PW and a position sensor IF2 (e.g., an interferometric device, a linear encoder, or a capacitive sensor), the substrate table WT can be precisely moved (e.g., to position different target portions C in the path of the radiation beam B). Similarly, a first positioner PM and a further position sensor IF1 can be used to precisely position the patterning device (e.g., a mask) MA relative to the path of the radiation beam B. The patterning device (e.g., a mask) MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

[0043] refer to Figure 1B , the radiation beam B is incident on and patterned by a patterning device (e.g., mask MA), which is held on a support structure (e.g., mask table MT). After passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. The projection system has a pupil conjugate PPU to an illumination system pupil IPU. Part of the radiation emanates from the intensity distribution at the illumination system pupil IPU and passes through the mask pattern without being affected by diffraction at the mask pattern, and produces an image of the intensity distribution at the illumination system pupil IPU.

[0044] The projection system PS projects an image pattern MP' of the mask pattern MP onto a photoresist layer coated on a substrate W, wherein the image MP' is formed by a diffraction beam generated by radiation from an intensity distribution according to the mask pattern MP. For example, the mask pattern MP may include an array of lines and spaces. The diffraction of radiation at the array and different from the zero-order diffraction generates a diverted diffraction beam with a change in direction in a direction perpendicular to the lines. The non-diffracted beam (i.e., the so-called zero-order diffraction beam) passes through the pattern without changing the propagation direction. The zero-order diffraction beam passes through the upper lens or lower lens group of the projection system PS, upstream of the pupil conjugate PPU of the projection system PS, to reach the pupil conjugate PPU. A portion of the intensity distribution in the plane of the pupil conjugate PPU and associated with the zero-order diffraction beam is an image of the intensity distribution in the illumination system pupil IPU of the illumination system IL. The aperture device PD is, for example, arranged at or substantially at a plane including the pupil conjugate PPU of the projection system PS.

[0045] The projection system PS is arranged to capture not only the zero-order diffraction beam, but also the first-order or first-order and higher-order diffraction beams (not shown) by means of a lens or lens group L. In some embodiments, dipole illumination for imaging a line pattern extending in a direction perpendicular to the line can be used to exploit the resolution enhancement effect of dipole illumination. For example, the first-order diffraction beam interferes with the corresponding zero-order diffraction beam at the level of the wafer W to produce an image of the line pattern MP at the highest possible resolution and a process window (i.e., the available depth of focus combined with the allowable exposure dose deviation). In some embodiments, astigmatism aberrations can be reduced by providing radiation poles (not shown) in the opposite quadrants of the illumination system pupil IPU. In addition, in some embodiments, astigmatism aberrations can be reduced by blocking the zero-order beam in the pupil conjugate PPU of the projection system associated with the radiation poles in the opposite quadrant. This is described in more detail in U.S. Patent No. US 7,511,799 B2, issued on March 31, 2009, which is incorporated herein by reference in its entirety.

[0046] With the aid of a second positioner PW and a position sensor IF (e.g. an interferometric device, a linear encoder, or a capacitive sensor), the substrate table WT can be precisely moved (e.g. to position a different target portion C in the path of the radiation beam B). Similarly, a first positioner PM and another position sensor (not shown) can be used. Figure 1B ) can be used to accurately position the mask MA relative to the path of the radiation beam B (for example, after mechanical retrieval from a mask library or during scanning).

[0047] Typically, movement of the mask table MT can be achieved 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 achieved with the aid of a long-stroke module and a short-stroke module, which form part of the second positioner PM. In the case of a stepper (as opposed to a scanner), the mask table MT may be connected only to a short-stroke actuator or may be fixed. Mask MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks (as shown) occupy dedicated target portions, they may be located in the space between target portions (called scribe alignment marks). Similarly, in the case where more than one die is provided on the mask MA, the mask alignment marks may be located between the dies.

[0048] The mask table MT and the patterning device MA may be in the vacuum chamber V, where an in-vacuum robot IVR may be used to move the patterning device (such as a mask) into and out of the vacuum chamber V. Alternatively, when the mask table MT and the patterning device MA are outside the vacuum chamber, an out-of-vacuum robot may be used for various transport operations similar to the in-vacuum robot IVR. Both the in-vacuum robot and the out-of-vacuum robot need to be calibrated for smoothly transferring any payload (e.g., a mask) to a transfer station of a fixed kinematic mount.

[0049] The lithographic apparatuses 100 and 100' may be used in at least one of the following modes:

[0050] 1. In step mode, the support structure (e.g. mask table) MT and substrate table WT are held substantially static and the entire pattern imparted to the radiation beam B is projected simultaneously onto a target portion C (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.

[0051] 2. In scan mode, the support structure (e.g. mask table) MT and substrate table WT are scanned synchronously and 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 (e.g. mask table) MT may be determined by the (de-)magnification and image reversal characteristics of the projection system PS.

[0052] 3. In another mode, the support structure (e.g. mask table) MT remains essentially stationary, thereby holding the 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 may be employed, and the programmable patterning device updated as required after each movement of the substrate table WT or between successive radiation pulses during a scan. This mode of operation may be readily applied to maskless lithography which utilizes a programmable patterning device, such as a programmable mirror array.

[0053] Combinations and / or variations of the described modes of use or entirely different modes of use may also be employed.

[0054] In another embodiment, the lithographic apparatus 100 includes an extreme ultraviolet (EUV) source configured to generate an EUV radiation beam for EUV lithography. Typically, 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.

[0055] Figure 2The lithographic apparatus 100 is shown in more detail and includes a source collector device SO, an illumination system IL, and a projection system PS. The source collector device SO is constructed and arranged so that a vacuum environment can be maintained in a closed structure 220 of the source collector device SO. The EUV radiation emitting plasma can be formed by a discharge plasma source. EUV radiation can be generated by a gas or vapor (e.g., xenon, lithium vapor, or tin vapor), wherein an extremely hot plasma 210 is generated to emit radiation in the EUV range of the electromagnetic spectrum. For example, the extremely hot plasma 210 is generated by a discharge that causes at least partially ionized plasma. For effective generation of radiation, a partial pressure of, for example, 10 Pascals (Pa) of xenon, lithium, tin vapor, or any other suitable gas or vapor may be required. In some embodiments, an excited tin (Sn) plasma is provided to generate EUV radiation.

[0056] The radiation emitted by the hot plasma is transferred from the source chamber 211 to the collector chamber 212 via an optional gas barrier or contaminant trap 230 (also referred to as a contaminant barrier or foil trap in some cases) positioned in or behind an opening in the source chamber 211. The contaminant collector 230 may include a channel structure. The contaminant collector 230 may also include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant collector or contaminant barrier 230 further indicated herein includes at least a channel structure.

[0057] The collector chamber 212 may include a radiation collector CO, which may be a so-called grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation passing through the collector CO may be reflected by a grating spectral filter 240 to be focused in a virtual source point IF. The virtual source point IF is often referred to as an intermediate focus, and the source collector arrangement is arranged such that the intermediate focus IF is located at or near an opening 219 in the enclosed structure 220. The virtual source point IF is an image of the radiation emitting plasma 210. The grating spectral filter 240 is particularly useful for suppressing infrared (IR) radiation.

[0058] The radiation then passes through an illumination system IL which may include a faceted field mirror device 222 and a faceted pupil mirror device 224 which are arranged to provide a desired angular distribution of the radiation beam 221 at the patterning device MA and a desired uniformity of radiation intensity at the patterning device MA. When the radiation beam 221 is reflected at the patterning device MA held by the support structure MT, a patterned beam 226 is formed and the patterned beam 226 is imaged by the projection system PS via reflective elements 228, 229 onto a substrate W held by a wafer stage or substrate table WT.

[0059] There may typically be more elements than those shown in the illumination optics unit IL and the projection system PS. Depending on the type of lithographic apparatus, a grating spectral filter 240 may optionally be present. In addition, there may be more than Figure 2 The reflectors shown in FIG. 5 are more numerous than those in FIG. Figure 2 In the projection system PS shown in FIG. , one to six additional reflective elements may be present.

[0060] like Figure 2 The collector optics CO shown is depicted as an example of a collector (or collector mirror) with nested collectors having grazing incidence reflectors 253, 254 and 255. The grazing incidence reflectors 253, 254 and 255 are arranged axially symmetrically around the optical axis O, and this type of collector optics CO is preferably used in conjunction with a discharge plasma source (commonly referred to as a DPP source).

[0061] Exemplary Lithography Cell

[0062] Figure 3A lithography unit 300, sometimes also referred to as a lithography unit (lithocell) or cluster, according to some embodiments is shown. The lithography apparatus 100 or 100' may form a part of the lithography unit 300. The lithography unit 100 may also include one or more devices to perform pre-exposure processes and post-exposure processes on the substrate. Conventionally, these include: a spin coater SC for depositing a resist layer, a developer DE for developing the exposed resist, a chill plate CH, and a baking plate BK. The substrate handler or robot RO picks up the substrate from the input / output ports I / O1, I / O2, moves these substrates between different process devices, and delivers them to the feed station LB of the lithography apparatus 100 or 100'. These devices (generally referred to as tracks) are under the control of the track control unit TCU, which is itself controlled by the monitoring system SCS, which also controls the lithography apparatus via the lithography control unit LACU. Therefore, different devices can be operated to maximize production volume and processing efficiency.

[0063] Embodiments of the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present disclosure may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include a read-only memory (ROM), a random access memory (RAM); a disk storage medium; an optical storage medium; a flash memory device; electrical, optical, acoustic, or other forms of propagation signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. In addition, firmware, software, routines, and / or instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for simplicity only, and such actions are actually caused by a computing device, processor, controller, or other device that executes firmware, software, routines, instructions, etc.

[0064] Exemplary substrate stage

[0065] Figure 4A schematic diagram of a substrate platform 400 according to some embodiments is shown. In some embodiments, the substrate platform includes a substrate stage 402, a support block 404, and one or more sensor structures 406. In some embodiments, the substrate stage 402 includes a clamp to hold a substrate 408 (e.g., an electrostatic clamp). In some embodiments, each sensor structure 406 of the one or more sensor structures includes a transmission image sensor (TIS) board. The TIS board is a sensor unit that includes one or more sensors and / or markers used in a TIS sensing system, for accurately positioning a wafer W relative to a projection system (e.g., the projection system PS of FIG. 1 ) and accurately positioning a mask (e.g., the mask MA of FIG. 1 ) of a lithography apparatus (e.g., the lithography apparatus 100 of FIG. 1 ). Although a TIS board is shown here for illustration, the embodiments herein are not limited to any particular sensor. The substrate stage 402 is disposed on the support block 404. The one or more sensor structures 406 are disposed on the support block 404.

[0066] In some embodiments, the substrate 408 is disposed on the substrate stage 402 while the substrate platform 400 supports the substrate 408 .

[0067] The terms "flat," "flatness," and the like may be used herein to describe structures relative to the general plane of a surface. For example, a curved or uneven surface may be a surface that does not conform to a flat plate. Protrusions or depressions on a surface may also be characterized as deviations from a "flat" plane.

[0068] The terms "smoothness", "roughness", etc. may be used herein to refer to local variations, microscopic deviations, granularity or texture of a surface. For example, surface roughness may refer to microscopic deviations of a surface profile from a mean line or plane. Deviations are typically measured (in units of length) as amplitude parameters, such as root mean square (RMS) or arithmetic mean deviation (Ra) (e.g., 1 nm RMS).

[0069] In some embodiments, the surface of the substrate table (e.g. Figure 1A and Figure 1B Wafer stage WT, Figure 4 The substrate stage 402 in the wafer may be flat or knobby. When the surface of the substrate stage is flat, any particles or contaminants adhering between the substrate stage and the wafer will cause the contaminants to pass through the wafer and print, causing photolithography errors in its vicinity. Therefore, contaminants reduce the productivity of the equipment and increase production costs.

[0070] Providing a burl on the substrate table helps to reduce the undesirable effects of a flat substrate table. When a wafer is clamped to a substrate table with a burl, there is available space in the area where the wafer does not contact the substrate table. The empty space is used as a pocket for contaminants to prevent printing errors. Another beneficial effect is that the increased load caused by the burl makes it easier for contaminants on the burl to be crushed. Crushing contaminants also helps to reduce through-printing errors. In some embodiments, the common surface area of ​​the burl can be approximately 1%-5% of the surface area of ​​the substrate table. Here, the surface area of ​​the burl refers to the surface in contact with the wafer (for example, excluding the side walls). And, the surface area of ​​the substrate table refers to the span of the substrate table surface where the burl is located (for example, excluding the side or back of the substrate table). When a wafer is clamped to a substrate table with a burl, the load is increased by 100 times compared to a flat substrate table, which is enough to crush most contaminants. Although the example here uses a substrate table, the example is not intended to be limiting. For example, embodiments of the present disclosure may be implemented on reticle stages for various chucking structures (eg, electrostatic chucks, chuck membranes) and various lithography systems (eg, EUV, DUV).

[0071] Now, the burl-to-wafer interface controls the functional performance of the substrate table. When the surface of the substrate table is smooth, adhesion can be generated between the smooth surface of the substrate table and the smooth surface of the wafer. The phenomenon of two smooth surfaces contacting and sticking together is called wringing. Wringing can cause problems in device production, such as overlay problems due to high friction and in-plane stress in the wafer (it is preferred to let the wafer slide easily during alignment). A way to reduce the friction of the burl-to-wafer interface is to coat the burl with a low-friction coating (e.g., diamond-like carbon). However, in the presence of water (e.g., immersion lithography), the coating can be polished faster. Another way to reduce the friction of the burl-to-wafer interface is to roughen the surface of the burl top to reduce the contact surface area. However, a rough burl top cannot maintain its roughness for a long time. The rougher the initial roughness of the burl top, the faster it polishes and wears.

[0072] Furthermore, it has been observed that the surfaces of the substrate table's burls are susceptible to abnormally rapid wear, particularly at the edges away from the center of the substrate table (i.e., non-uniform wear). Non-uniform wear causes the wafer to bend when it is clamped to the substrate table, which in turn can reduce the accuracy of lithographic placement of device structures, overlay drift over time, etc. And overall wear can reintroduce twisting problems and lead to reduced imaging performance due to changes in the global shape of the clamping surface.

[0073] In order to prevent friction and wear of the surface, the surface features of the substrate stage can be manipulated. For example, a nanostructure (e.g., nanopillars or fine burls) is designed on the top surface of the burl. That is, from a random surface design (roughening) to a deterministic surface design. The term "fine burl" can be used herein to refer to the deterministic nanopillar design on the surface of the burl described previously. Embodiments of the present disclosure provide structures and methods for manipulating the tribological properties of the surface of a substrate stage.

[0074] Figure 5 A schematic cross-sectional view of a region of a substrate table 500 is shown in accordance with some embodiments. The substrate table 500 includes a surface 502 and thick burls 504. Each of the thick burls 504 includes a burl top surface 506 and thin burls 508, which are shown in inset 510. Inset 510 is a top view of the thick burls 504.

[0075] In some embodiments, thick burl 504 is disposed on surface 502. Thin burl 508 is disposed on burl top surface 506. Figure 5 While the thick burl 504 and thin burl 508 are depicted as having circular areas, it should be understood that the thick burl 504 and thin burl 508 may have other area geometries (e.g., square, oval, etc.). Figure 5 The burls 508 are depicted as having a circular and / or octagonal arrangement, but any number of burls 508 (including one) and any arrangement across the burl top surface 506 (eg, a grid or random distribution) may be used.

[0076] In some embodiments, each of the thick knobs in the group knobs 504 has a width or diameter (a dimension parallel to the plane of the surface 502) of about 100 microns to 1000 microns, and each of the thick knobs 504 has a height (a dimension perpendicular to the plane of the surface 502) of about 10 microns to 200 microns, 10 microns to 50 microns, or 10 microns to 100 microns. Each of the thin knobs 508 has a width or diameter of about 1 micron to 15 microns. Each of the thin knobs 508 has a height of about 10 nm to 50 nm, 20 nm to 40 nm, or 20 nm to 30 nm. The distance between two of the thin knobs 508 is about 50 microns to 200 microns, 50 microns to 150 microns, or 50 microns to 100 microns. Each of the thin knobs 508 includes a contact area (to contact the substrate 518) having a surface roughness of less than about 1 nm RMS.

[0077] Other dimensions may be selected for thick burl 504 and / or other dimensions for thin burl 508. For example, the dimensions for thick burl 504 may be based on the size of typical or expected contaminant particles in a lithographic apparatus.

[0078] The contact surface area is a parameter that affects friction. Therefore, the size for thick burl 504 and / or the size for thin burl 508 can be based on the contact area to achieve a specified friction.

[0079] In some embodiments, the substrate stage 500 is configured to support a substrate 518. The substrate stage 500 can be switched between two states: engaged (clamping the substrate) and disengaged (releasing the substrate). In the disengaged state, the load between the burl top surface 506 and the substrate 518 is primarily due to gravity acting on the substrate 518 (low load). In the low load state, the substrate 518 contacts the fine burl 508 rather than the burl top surface 506. The dimensions of the fine burl 508 described above improve the performance of the substrate stage 500 due to, for example, having a relatively small contact area to reduce friction and a height designed to reduce wear. That is, in some embodiments, the common surface area of ​​the fine burl 508 can be approximately 1%-5% of the surface area of ​​the burl top surface 506. When most wear is expected to occur at moderate loads, the effects of wear are reduced because the load is distributed over a larger burl area. The relationship between load / pressure and burl contact area is described below with reference to Figure 6 Discussion. In various comparisons, the collective surface area of ​​the burls 508 can be approximately 0.01%-0.25% of the surface area of ​​the substrate stage 500 (the span of the surface of the substrate stage where the burls are located, e.g., excluding the lateral or back sides of the substrate stage). The reduced friction allows the substrate 518 to be easily translated during alignment while also reducing in-plane stresses on the substrate 518. In addition, the burls 508 disrupt the plane of the burl top surface 506 sufficiently to prevent twisting. That is, in some embodiments, the burls 508 are configured to reduce twisting or (pulling / adhesion forces) between the substrate stage 500 and the substrate 518. As a result, the performance of the substrate stage 500 (e.g., overlay performance) can be enhanced. The reduction in twisting is due to the fact that the burls 508 act as springs that peel the substrate off the surface between the burls (burl top surface 506) when the clamping force is released.

[0080] Conversely, the engaged state of the substrate stage 500 creates an increased load between the burl top surface 506 and the substrate 518. At a sufficiently small scale, any surface of a material can be considered elastic, compressible, or deformable ( Figure 7 ). The load may cause the substrate 518 to deform and "sink" into the burl 508. If the height of the burl 508 is properly chosen, the substrate 518 may contact the burl top surface 506. The increased contact area greatly increases the friction between the substrate stage 500 and the substrate 518. Therefore, the substrate 518 may be securely held for photolithography processes.

[0081] In some embodiments, the height of the burl 508 is selected based on selected friction characteristics. The burl 508 can enhance the release of the substrate 518. The height difference between the burl top surface 506 and the burl 508 causes the burl 508 to act like a spring and push against the substrate 518. Therefore, the substrate 518 can avoid sticking to the substrate stage 500.

[0082] Figure 6 A graph 600 of burl top surface contact area versus clamping pressure is shown according to some embodiments. The vertical axis represents the burl top surface area that is actually in contact with the substrate (e.g., Figure 7 6, the percentage of the burl top surface 706 in contact with the substrate 718. The horizontal axis represents the clamping pressure or force applied to the substrate in arbitrary units (AU). The dashed line 602 represents a simulation of the measurement of the actual contact area as the clamping force varies (ignoring twisting effects). Adjusting the burl height allows adjustment of (a) the low pressure contact area (0-1.6 AU; region 604), (b) the starting pressure for the high contact area regime (1.6 AU; region 606), and (c) the contact area at full clamping pressure (>3 AU; region 608).

[0083] The discussion so far has focused on nanopillars or burls that help reduce twisting, and the many beneficial effects. However, in some cases, the presence of burls may not provide sufficient force to promote consistent separation of the substrate from the burl top surface. Embodiments of the present disclosure provide structures and methods for further manipulating the tribological properties of the surface of the substrate table.

[0084] Figure 7 A schematic cross-sectional view of a region of a substrate table 700 is shown in accordance with some embodiments. The substrate 700 includes a surface 702 and a thick burl 704. Each of the thick burls 704 includes a burl top surface 706 and a thin burl 704, as shown in inset 710. Inset 710 is a cross-sectional view of a region of the thick burl 704. Each of the thin burls 708 includes a contact surface 712. In some embodiments, the burl top surface 706 includes a rough region 714. In some embodiments, each of the thick burls 704 also includes an intermediate burl 716.

[0085] In some embodiments, thick burl 704 is disposed on surface 702. Thin burl 708 and intermediate burl 716 are disposed on burl top surface 706. For similar reasons, the arrangement, shape, and number of thin burl 708 and / or intermediate burl 716 may be as described with reference to thin burl 508 ( Figure 5) as described above. In addition, the middle burl 716 can have a height that is different from the height of the thin burl 708 (i.e., different height). The different heights or layered structures can achieve functions similar to the rough areas. The rough area 714 is set between the thin burls 708. The term "between" can be used in this article to refer to a location between, close to, near, and / or in a general surrounding area. Therefore, the rough area 714 can be set between two thin burls 708 or fill the entire burl top surface 706. In some embodiments, the rough area 714 can be divided into small patches (e.g., multiple rough areas 714) distributed between the thin burls 708, close to the thin burls 708, near the thin burls 708, and / or roughly adjacent to the thin burls 708.

[0086] In some embodiments, the substrate stage 700 is configured to support a substrate 718. The substrate surface 720 of the substrate 718 is Figure 7 700. For similar reasons, the function and interaction of the substrate stage 700 with the substrate 718 can be described as above for the substrate stage 500 and the substrate 518 ( Figure 5 Each of the thin protuberances 708 includes a contact area (to contact the substrate 718) having a surface roughness of less than about 1 nm RMS. The rough area 714 can have a surface roughness of approximately 2 nm-10 nm, 2 nm-8 nm, or 3 nm-5 nm RMS.

[0087] When the substrate stage 700 engages the substrate 718, the increased load can cause the substrate 718 to deform and "sink" into the burl 708. This is depicted by the substrate surface 720 in the inset 710. It is important that the substrate stage 700 successfully releases the substrate 718 when disengaging. Twisting can cause eventual wear of the burl 708, particularly toward the edge of the substrate stage 700 where the substrate movement during clamping / unclamping is greatest. Therefore, in some embodiments, when the substrate stage 700 engages the substrate 718, the rough area 714 can contact the substrate 718. In this case, the deformed substrate obtains the beneficial effect of having an increased contact area with the burl top surface 706. These beneficial effects are described in reference to Figure 5 and Figure 6 Described. Figure 5 In contrast to the burl top surface 506 , the roughened region 714 enhances separation of the substrate 718 from the burl top surface 706 during debonding.

[0088] In some embodiments, intermediate burls 716 may be used instead of or in addition to roughened regions 714 to enhance separation of substrate 718. Intermediate burls 716 are disposed between thin burls 708. The layered structure (height difference) created by intermediate burls 716 may enhance separation by further interrupting the plane of burl top surface 706 in the region between thin burls 708.

[0089] In some embodiments, each of the burls 704 further includes a modified surface 722. The modified surface 722 may be disposed between two burls 708 or fill the entire burl top surface 706. In some embodiments, the modified surface 722 may be divided into a plurality of small pieces (e.g., a plurality of modified surfaces 722) distributed between, between, near, and / or approximately near the burls 708.

[0090] In some embodiments, the modified surface 722 has a chemically modified low surface energy. The chemical modification can be achieved using, for example, a chemical bath or rinse. The low surface energy reduces the adhesion between the substrate stage 700 and the substrate 718. The reduced adhesion enhances the separation of the substrate 718 from the substrate stage 700 when detached. The modified surface 722 can be implemented instead of the rough area 714 and / or the middle ridge 716 or in addition to the rough area 714 and / or the middle ridge 716.

[0091] Figure 8 Method steps for manufacturing a substrate stage according to some embodiments are shown. In step 802, a substrate stage is supported to receive a manufacturing process. In step 804, thick and thin burls are manufactured on the substrate stage. Manufacturing the thick and thin burls includes setting the thin burls on the top surface of the burls of the thick burls. In step 806, rough areas and / or intermediate burls are manufactured on the substrate stage. Manufacturing the rough areas and / or intermediate burls also includes setting the rough areas and / or intermediate burls between the thin burls. Manufacturing the rough areas further includes using laser ablation, etching (e.g., reactive ion etching) and / or mechanical processes (e.g., rough polishing) to produce the rough areas. Manufacturing the thick burls, thin burls and / or intermediate burls further includes manufacturing via the photolithography process described herein. In step 808, the top surface of the burls is chemically treated to obtain a low surface energy (e.g., suppressed dangling bonds) of the top surface of the burls. The chemical treatment or modification can be achieved, for example, by immersing or rinsing the substrate stage with a chemical substance (e.g., an acid, a solvent, a base). The low surface energy reduces the adhesion between the substrate table and the substrate.

[0092] Figure 8The method steps can be performed in any conceivable order, and not all steps are required to be performed. For example, step 808 can be performed instead of step 806 or in addition to step 806. The thick burls, thin burls and / or intermediate burls and the rough areas can be manufactured simultaneously, at different times and / or in any order. In another example, step 806 can be optional (for example, the top surface of the burl can have the same roughness as the surface of the thin burl). The arrangement, shape and size of the structures on the substrate table (e.g., thick burls and thin burls, rough areas, etc.) can be as described above with reference to Figure 5 and 7 described.

[0093] In general, deterministically structured burl tops (e.g., fine burls) allow the traditional tradeoff between good wear performance and good friction performance to be broken. Low friction is required when loading the wafer to ensure that the wafer is stress-free when fully clamped. High friction is required when the wafer is fully clamped so that the wafer does not move during wafer stage acceleration (or due to wafer heating). It is desirable to have a stable surface that runs on a large number (e.g., thousands, tens of thousands) of wafer loads, where stability is related to the maintenance of friction characteristics and the overall flatness of the wafer stage. Low friction can be achieved by limiting the contact surface area. Limiting the contact surface area can be achieved by surface roughening or small diameter burls. Both can lead to higher peak loads and therefore accelerate material removal, changes in global shape and / or reduction in roughness (changing friction). The embodiments of the present disclosure have described how the area and height of the fine burls can be adjusted to achieve desired friction and wear resistance without compromise. By adjusting the area and height of the burl, it is possible to achieve low surface area and low friction at low loads, low to medium friction and low wear at medium loads (where most wear occurs), and high friction and stability at high loads by contacting the entire burl top surface.

[0094] The embodiments may be further described using the following terms:

[0095] 1. A substrate stage for supporting a substrate, the substrate stage comprising:

[0096] Surface; and

[0097] burls disposed on the surface, wherein each of the burls comprises:

[0098] a burl top surface; and

[0099] A thin burl is disposed on a top surface of the burl and is configured to contact the substrate when the substrate table supports the substrate.

[0100] 2. A substrate table according to clause 1, wherein:

[0101] Each of the burls includes a contact surface configured to contact the substrate; and the contact surface has a surface roughness of less than about 1 nm RMS.

[0102] 3. A substrate table according to clause 1, wherein each of the burls has a width of approximately 100 microns - 1000 microns and a height of approximately 10 microns to 200 microns.

[0103] 4. A substrate table according to clause 1, wherein each of the nubs has a width of approximately 1 micron to 10 microns.

[0104] 5. A substrate table according to clause 1, wherein the burls have a height of approximately 10 nm - 50 nm.

[0105] 6. A substrate table according to clause 1, wherein a distance between two of the nubs is approximately 50 microns to 200 microns.

[0106] 7. A substrate table according to clause 1, wherein the total surface area of ​​the contact regions of the burls is less than 0.1% relative to the total surface area of ​​the substrate table.

[0107] 8. A substrate table according to clause 1, wherein:

[0108] Each of the thick burls further includes an intermediate thin burl disposed between the thin burls on a top surface of the burl; and

[0109] The height of the thin process section is different from the height of the middle thin process section.

[0110] 9. A substrate table according to clause 1, wherein the burl top surface comprises a roughened region disposed between the fine burls.

[0111] 10. A substrate table according to clause 9, wherein the roughened region is configured to contact the substrate when the substrate table engages the substrate.

[0112] 11. A substrate table according to clause 9, wherein the rough region has a surface roughness of approximately 2 nm-8 nm RMS.

[0113] 12. A substrate table according to clause 1, wherein:

[0114] The burl top surface comprises a modified surface having a chemically modified low surface energy; and

[0115] The modified surface is configured to reduce adhesion between the substrate table and the substrate.

[0116] 13. A lithography apparatus comprising:

[0117] an irradiation system configured to generate a radiation beam;

[0118] a support configured to support a patterning device configured to impart a pattern to the beam;

[0119] a projection system configured to project the patterned beam onto a substrate; and

[0120] A substrate stage configured to support a substrate, the substrate stage comprising:

[0121] Surface; and

[0122] A rough knob is disposed on the surface, wherein each rough knob in the rough knob

[0123] The knobs include:

[0124] a burl top surface; and

[0125] A thin burl is disposed on a top surface of the burl and is configured to contact the substrate when the substrate table supports the substrate.

[0126] 14. The lithographic apparatus of clause 13, wherein the burls have a height of approximately 10 nm-50 nm.

[0127] 15. The lithographic apparatus of clause 13, wherein the burl top surface comprises a rough surface disposed between the fine burls.

[0128] 16. The lithographic apparatus of clause 13, wherein the roughened surface is configured to contact the substrate when the substrate table engages the substrate.

[0129] 17. The lithographic apparatus of clause 16, wherein the roughened surface has a surface roughness of approximately 2 nm-8 nm RMS.

[0130] 18. A method for manufacturing a substrate table, the method comprising:

[0131] supporting a substrate table to receive a manufacturing process; and

[0132] A thick burl and a thin burl are fabricated on the substrate table, wherein the fabricating of the thick burl and the thin burl includes providing a thin burl on a burl top surface of the thick burl.

[0133] 19. The method of clause 18, further comprising producing a rough surface on the substrate table, wherein producing the rough surface comprises producing rough areas between fine burls on the burl top surface.

[0134] 20. The method of clause 19, wherein said producing a roughened surface further comprises generating said roughened area using laser ablation.

[0135] Although specific reference may be made herein to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, such as the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, LCDs, thin film heads, etc. Those skilled in the art will understand that in the context of such alternative applications, any use of the terms "wafer" or "die" herein may be considered synonymous with the more general terms "substrate" or "target portion", respectively. The substrates referred to herein may be processed before or after exposure in, for example, a track unit (a tool that typically applies a resist layer to a substrate and develops the exposed resist), a metrology unit, and / or an inspection unit. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. In addition, a substrate may be processed more than once, for example to create a multi-layer IC, so the term substrate used herein may also refer to a substrate that already includes multiple processing layers.

[0136] Although specific reference has 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, such as imprint lithography, and that the invention is not limited to optical lithography where the context permits. In imprint lithography, the topography in the patterning device defines the pattern created on the substrate. The topography of the patterning device may be pressed into a resist layer provided to the substrate, whereby the resist is cured on the substrate by applying electromagnetic radiation, heat, pressure, or a combination thereof. After the resist is cured, the patterning device is removed from the resist to leave a pattern therein.

[0137] It should be understood that the phraseology or terminology herein is for the purpose of description rather than limitation, so that the phraseology or terminology of the present disclosure should be interpreted by those skilled in the relevant art in light of the teachings herein.

[0138] The term "substrate" as used herein describes a material on which a layer of material is added. In some embodiments, the substrate itself may be patterned, and the material added on top of it may also be patterned, or may remain unpatterned.

[0139] Although specific reference may be made herein to the use of the apparatus and / or system according to the present invention in IC manufacturing, it should be clearly understood that these apparatus and / or systems have many other possible applications. For example, they can be applied to the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, LCD panels, thin film magnetic heads, etc. Those skilled in the art will understand that in the context of such alternative applications, any use of the terms "reticle", "wafer" or "die" herein should be considered to be replaced by the more general terms "mask", "substrate" and "target portion", respectively.

[0140] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. This description is not intended to limit the invention.

[0141] It should be understood that the Detailed Description section, rather than the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention contemplated by the inventors, and thus are not intended to limit the present invention and the appended claims in any way.

[0142] The present invention has been described above with the aid of functional building blocks that illustrate the implementation of specific functions and their relationships. For ease of description, the boundaries of these functional building blocks have been arbitrarily defined herein. Alternative boundaries may be defined as long as the specific functions and their relationships are appropriately performed.

[0143] The foregoing description of the specific embodiments will fully reveal the general nature of the invention so that others can easily modify and / or adapt these specific embodiments by applying knowledge in the art and without undue experimentation without departing from the general concept of the invention. Therefore, based on the teachings and guidance presented herein, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments.

[0144] The breadth and scope of the present invention should not be limited by any of the above-described embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. A method for manufacturing a substrate table, the method comprising: include: supporting the substrate table to receive a manufacturing process; fabricating a thick burl on the substrate table; Making a thin burl on the burl top surface of the thick burl; as well as Intermediate burls are fabricated between the burls disposed on the burl top surface, wherein the height of the burls is different than the height of the intermediate burls.

2. The method according to claim 1, further comprising: include: A rough area is fabricated on the substrate table, wherein fabricating the rough area comprises: arranging the rough area between the fine burls on the burl top surface.

3. The method according to claim 2, wherein the rough surface is produced include: The roughened area is produced using laser ablation. The method of claim 2 , wherein the rough regions each have a surface roughness of 2 nm to 8 nm RMS.

5. The method of claim 1, wherein each of the burls comprises a contact surface configured to contact the substrate when the substrate is supported by the substrate table, the contact surface having a surface roughness of less than 1 nm RMS. 6 . The method of claim 1 , wherein each of the burls has a width of 100 to 1000 microns and a height of 10 to 200 microns. 7 . The method of claim 1 , wherein each of the burls has a width of 1 to 10 microns and a height of 10 to 50 microns. 8 . The method according to claim 1 , wherein a distance between two of the thin tubercles is 50 μm to 200 μm.

9. The method of claim 1, wherein the total surface area of ​​the contact regions of the burls relative to the total surface area of ​​the substrate table is less than 0.1%.

10. The method according to claim 1, further comprising: include: A modified surface is fabricated on a top surface of each burl, the modified surface having a chemically modified low surface energy and configured to reduce adhesion between the substrate stage and a substrate supported by the substrate stage.

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