Substrate holder for use in lithographic apparatus

Abstract

Embodiments of the present disclosure relate to a substrate holder for use in a lithographic apparatus, in particular a substrate holder for use in a lithographic apparatus and configured to support a substrate, the substrate holder comprising: a body having a body surface; a plurality of main tabs protruding from the body surface, wherein each main tab has a distal surface configured to support a substrate; a first sealing member protruding from the body surface and having an upper surface, the first sealing member surrounding the plurality of main knots and configured to limit a passage of liquid between the substrate and the body surface radially inward through the first sealing member; and a plurality of small tabs protruding from an upper surface of the first sealing member, wherein each small tab has a distal surface configured to support a substrate.

Description

[0001] Case division theory bright

[0002] This application is a divisional application of the invention patent application with international application number PCT / EP2018 / 075293, international application date September 19, 2018, date of entry into the Chinese national phase April 10, 2020, Chinese national application number 201880066459.8, and invention name “Substrate holder for use in lithography equipment”. Technical Field

[0003] The present invention relates to a substrate holder for use in a lithographic apparatus. Background Art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern to a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus can, for example, project a pattern (also commonly referred to as a "design layout" or "design") of a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate (e.g., a wafer).

[0005] As semiconductor manufacturing processes continue to advance, the size of circuit elements continues to decrease, while the number of functional elements (e.g., transistors) per device has been growing steadily over the decades at a trend often referred to as "Moore's Law." In order to keep up with Moore's Law, the semiconductor industry is seeking technologies that can create smaller and smaller features. In order to project a pattern onto a substrate, a lithography device can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features patterned on the substrate. Typical wavelengths currently used are 365nm (i-line), 248nm, 193nm, and 13.5nm. Compared to lithography equipment using, for example, radiation with a wavelength of 193nm, lithography equipment using extreme ultraviolet (EUV) radiation with a wavelength in the range of 4nm to 20nm (e.g., 6.7nm or 13.5nm) can be used to form smaller features on a substrate.

[0006] In immersion lithography apparatus, an immersion liquid is placed in the space between the apparatus's projection system and the substrate. This immersion liquid can find its way past the edge of the substrate to the substrate's lower surface. This can be detrimental due to contamination of the substrate's lower surface by the immersion liquid and / or thermal loads applied to the substrate's lower surface near the substrate's edge due to evaporation of the immersion liquid. A substrate holder configured to support the substrate can include features that reduce the amount and / or distance that the immersion liquid moves radially inward along the substrate's lower surface. Such features can adversely affect the flatness and cleanliness achieved on the substrate, as well as ease of removal. Summary of the Invention

[0007] It is an object of the present invention to provide a substrate holder having an acceptable compromise between the performance of the substrate holder in terms of flatness and cleanliness of the substrate and the reduction of the passage of immersion liquid along the lower surface of the substrate.

[0008] In one embodiment of the present invention, a substrate holder for use in a lithography device and configured to support a substrate is provided, the substrate holder comprising: a body having a body surface; a plurality of main protrusions protruding from the body surface, wherein each main protrusion has a distal surface configured to support the substrate; a first sealing member protruding from the body surface and having an upper surface, the first sealing member surrounding the plurality of main protrusions and configured to limit the passage of liquid radially inward through the first sealing member between the substrate and the body surface; and a plurality of small protrusions protruding from the upper surface of the first sealing member, wherein each small protrusion has a distal surface configured to support the substrate.

[0009] In one embodiment of the present invention, a substrate holder for use in a lithography device and configured to support a substrate is provided, the substrate holder comprising: a body having a body surface; a plurality of main protrusions protruding from the body surface, wherein each main protrusion has a distal surface configured to support the substrate; a first sealing member protruding from the body surface and having an upper surface, the first sealing member surrounding the plurality of main protrusions and configured to limit the passage of liquid radially inward through the first sealing member between the substrate and the body surface; a second sealing member protruding from the body surface, the second sealing member surrounding the first sealing member and configured to limit the passage of liquid radially inward through the second sealing member between the substrate and the body surface; a plurality of extraction openings formed in the body between the first sealing member and the second sealing member for extracting fluid from between the body and the substrate into the body; and a plurality of outer protrusions protruding from the body surface between the first sealing member and the second sealing member, each outer protrusion having a distal surface configured to support the substrate; wherein the plurality of outer protrusions and the plurality of extraction openings are alternately arranged on a line around the first sealing member and the plurality of main protrusions.

[0010] In one embodiment of the present invention, a substrate holder for use in a lithographic apparatus and configured to support a substrate is provided, the substrate holder comprising: a body having a body surface; a plurality of main protrusions protruding from the body surface, wherein each main protrusion has a distal surface configured to support the substrate; a first sealing member protruding from the body surface and having an upper surface, the first sealing member surrounding the plurality of main protrusions and configured to restrict a passage of liquid radially inwardly through the first sealing member between the substrate and the body surface; a plurality of small protrusions protruding from the upper surface of the first sealing member, wherein each small protrusion has a distal surface configured to support the substrate; and a plurality of small protrusions protruding from the body surface. a second sealing member protruding from the surface of the body, the second sealing member surrounding the first sealing member and being configured to limit the passage of liquid radially inward through the second sealing member between the substrate and the surface of the body; a third sealing member protruding from the surface of the body, the third sealing member surrounding the first sealing member and the second sealing member and being configured to limit the passage of liquid radially inward through the third sealing member between the substrate and the surface of the body; a plurality of inlet openings formed in the body between the first sealing member and the second sealing member; and a plurality of extraction openings formed in the body between the second sealing member and the third sealing member for extracting fluid from between the body and the substrate into the body.

[0011] In one embodiment of the present invention, a substrate holder for use in a lithography device and configured to support a substrate is provided, the substrate holder comprising: a body having a body surface; a plurality of main protrusions protruding from the body surface, wherein each main protrusion has a distal surface configured to support the substrate; a sealing member protruding from the body surface and having an upper surface, the sealing member surrounding the plurality of main protrusions; a plurality of extraction openings formed in one or more first recesses in the upper surface of the sealing member; a plurality of inlet openings formed in one or more second recesses in the upper surface of the sealing member; and a barrier between the one or more first recesses and the one or more second recesses, the barrier being configured to limit the passage of liquid radially inward through the barrier between the substrate and the body surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0013] Figure 1 depicts a schematic overview of a lithographic apparatus;

[0014] Figure 2a and Figure 2b Depicted in cross-section are two different versions of a fluid handling structure having different features illustrated on the left and right hand sides, which may extend around a complete circumference;

[0015] Figure 3depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

[0016] Figure 4 depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

[0017] Figure 5 depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

[0018] Figure 6 depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

[0019] Figure 7 depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

[0020] Figure 8 depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

[0021] Figure 9 depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

[0022] Figure 10 depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

[0023] Figure 11 depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

[0024] Figure 12 A schematic overview depicting the edge of a substrate holder 200 according to the present invention; and

[0025] Figure 13 A schematic overview of the edge of a substrate holder 200 according to the present invention is depicted. DETAILED DESCRIPTION

[0026] In this document, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation including ultraviolet radiation (eg having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm or 126 nm).

[0027] As used herein, the terms "reticle," "mask," or "patterning device" should be broadly interpreted to refer to a general patterning device that can be used to impart a patterned cross-section (corresponding to the pattern to be created in a target portion of the substrate) to an incoming radiation beam. In this context, the term "light valve" may also be used. In addition to classical masks (transmissive or reflective, binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0028] Figure 1 A lithographic apparatus is schematically depicted. The lithographic apparatus comprises an illumination system (also referred to as illuminator) IL configured to condition a radiation beam B (e.g., UV radiation or DUV radiation); a mask support (e.g., mask table) MT configured to support a patterning device (e.g., mask MA) and connected to a first positioner PM configured to precisely position the patterning device MA according to certain parameters; a substrate support (e.g., wafer stage) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to precisely position the substrate support WT according to 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 via the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0029] In operation, the illumination system IL receives a radiation beam B from a radiation source SO, for example, via a beam delivery system BD. The illumination system IL may include various types of optical components (e.g., refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof) to guide, shape, and / or control the radiation. The illuminator IL may be used to condition the radiation beam B so that it has a desired spatial and angular intensity distribution in a cross-section at the plane of the patterning device MA.

[0030] The term "projection system" PS as used herein should be broadly interpreted as covering various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, as required by the exposure radiation used and / or other factors (e.g., the use of an immersion liquid or the use of a vacuum). Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system" PS.

[0031] The lithographic apparatus may be of a type in which at least a portion of the substrate may be covered by an immersion liquid having a relatively high refractive index (e.g., water) so as to fill the space 11 between the projection system PS and the substrate W, which is also known as immersion lithography. More information on immersion technology is given in US 6,952,253, which is incorporated herein by reference.

[0032] The lithographic apparatus may also be of a type having two or more substrate supports WT (also referred to as a "dual stage"). In such a "multi-stage" machine, the substrate supports WT may be used in parallel, and / or preparatory steps for subsequent exposure of a substrate W may be performed on a substrate W on one of the substrate supports WT while another substrate W on another substrate support WT is used to expose a pattern on another substrate W.

[0033] In addition to the substrate support WT, the lithographic apparatus can include a measurement stage. The measurement stage is arranged to hold sensors and / or cleaning equipment. The sensors can be arranged to measure properties of the projection system PS or properties of the radiation beam B. The measurement stage can hold multiple sensors. The cleaning equipment can be arranged to clean part of the lithographic apparatus, for example, part of the projection system PS or part of the system for providing immersion liquid. The measurement stage can be moved beneath the projection system PS when the substrate support WT is away from the projection system PS.

[0034] In operation, a radiation beam B is incident on a patterning device (e.g. a mask) MA held on a mask support MT and is patterned by a pattern (design layout) present on the patterning device MA. 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. With the aid of a second positioner PW and a position measurement system IF, the substrate support WT can be accurately moved, for example in order to position different target portions C in the path of the radiation beam B at focused and aligned positions. Similarly, a first positioner PM and possibly a further position sensor (in the Figure 1 The patterning device MA (not explicitly depicted in the figure) can be used to accurately position the patterning device MA relative to the path of the radiation beam B. The patterning device MA and the substrate W can be aligned using the mask alignment marks M1, M2 and the substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2 are shown as occupying dedicated target portions, they can be located in the space between target portions. When the substrate alignment marks P1, P2 are located between target portions C, they are referred to as scribe lane alignment marks.

[0035] To illustrate the present invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes, namely, the x-axis, the y-axis, and the z-axis. Each of the three axes is orthogonal to the other two axes. Rotation about the x-axis is called an Rx rotation. Rotation about the y-axis is called an Ry rotation. Rotation about the z-axis is called an Rz rotation. The x-axis and the y-axis define a horizontal plane, while the z-axis is in the vertical direction. The Cartesian coordinate system does not limit the present invention and is only used for illustration. On the contrary, another coordinate system such as a cylindrical coordinate system can be used to illustrate the present invention. The orientation of the Cartesian coordinate system can be different, for example, so that the z-axis has a component along the horizontal plane.

[0036] Immersion technology has been introduced into lithography systems to enable improved resolution of smaller features. In an immersion lithography apparatus, a layer of immersion liquid, having a relatively high refractive index, is inserted into the space 11 between the apparatus's projection system (through which a patterned beam is projected toward the substrate W) and the substrate W. The immersion liquid covers at least the portion of the substrate beneath the final element of the projection system PS. Thus, at least the portion of the substrate W that undergoes exposure is immersed in the immersion liquid. Because the wavelength of the exposure radiation in a liquid will be shorter than that in a gas, the effect of the immersion liquid is to enable imaging of smaller features. (The effect of the immersion liquid can also be viewed as increasing the effective numerical aperture (NA) of the system and increasing the depth of focus.)

[0037] In commercial immersion lithography, the immersion liquid is water. Typically, the water is high-purity distilled water (e.g., ultrapure water (UPW) commonly used in semiconductor manufacturing plants). In immersion systems, the UPW is often purified and may undergo additional processing steps before being supplied as the immersion liquid to the immersion space 11. In addition to water, other liquids with a high refractive index can be used as the immersion liquid, for example: hydrocarbons such as fluorocarbons; and / or aqueous solutions. Furthermore, it is contemplated that fluids other than liquids may be used in immersion lithography.

[0038] In this specification, reference will be made in the description to partial immersion in which immersion liquid is confined, in use, to a space 11 between a final element and a surface facing the final element. The facing surface is the surface of the substrate W or a surface of the support table (or substrate support WT) that is coplanar with the surface of the substrate W. (Note that, unless expressly stated otherwise, reference hereinafter to the surface of the substrate W also refers additionally or alternatively to the surface of the substrate support WT; and vice versa). A fluid handling structure 12 present between the projection system PS and the substrate support WT is used to confine the immersion liquid to the immersion space 11. The space 11 filled by the immersion liquid is smaller in plan than the top surface of the substrate W and remains substantially stationary relative to the projection system PS as the substrate W and substrate support WT move underneath.

[0039] Other immersion systems are contemplated, such as unconfined immersion systems (so-called "all-wet" immersion systems) and bath immersion systems. In unconfined immersion systems, the immersion liquid covers a greater area than the surface beneath the final component. The liquid outside the immersion space 11 is present as a thin film. The liquid may cover the entire surface of the substrate W or even the substrate W and the substrate support WT coplanar with the substrate W. In bath systems, the substrate W is completely immersed in a bath of immersion liquid.

[0040] The fluid handling structure 12 is a structure that supplies immersion liquid to the immersion space 11, removes immersion liquid from the space 11, and thereby confines the immersion liquid to the immersion space 11. It includes features that are part of the fluid supply system. The arrangement disclosed in PCT Patent Application Publication No. WO 99 / 49504 is an early fluid handling structure that includes conduits that supply or withdraw immersion liquid from the space 11 and operates based on the relative movement of the platform below the projection system PS. In more recent designs, the fluid handling structure extends along at least a portion of the boundary of the space 11 between the final element of the projection system PS and the substrate support WT or substrate W, thereby partially defining the space 11.

[0041] The fluid handling structure 12 may have a selection of different functions. Each function may be derived from corresponding features that enable the fluid handling structure 12 to perform that function. The fluid handling structure 12 may be referred to by a number of different terms, each referring to a function, such as a barrier member, a sealing member, a fluid supply system, a fluid removal system, a liquid confinement structure, etc.

[0042] As a barrier member, the fluid handling structure 12 is a barrier to the flow of immersion liquid from the space 11. As a liquid confinement structure, the structure confines the immersion liquid to the space 11. As a sealing member, the sealing features of the fluid handling structure form a seal that confines the immersion liquid to the space 11. The sealing features may include additional air flow from openings in the surface of the sealing member, such as an air knife.

[0043] In one embodiment, the fluid handling structure 12 may supply immersion fluid and is therefore a fluid supply system.

[0044] In one embodiment, the fluid handling structure 12 may at least partially confine immersion fluid and therefore be a fluid confinement system.

[0045] In one embodiment, the fluid handling structure 12 may provide a barrier to the immersion fluid and thus be a barrier member such as a fluid confinement structure.

[0046] In one embodiment, the fluid handling structure 12 may create or use a flow of air, for example to help control the flow and / or position of the immersion fluid.

[0047] The gas flow may form a seal that confines the immersion fluid, and thus the fluid handling structure 12 may be referred to as a sealing member; such a sealing member may be a fluid confinement structure.

[0048] In one embodiment, an immersion liquid is used as the immersion fluid. In this case, the fluid handling structure 12 may be a liquid handling system. With reference to the previous description, references in this paragraph to features defined relative to a fluid may be understood to include features defined relative to a liquid.

[0049] The lithographic apparatus has a projection system PS. During exposure of a substrate W, the projection system PS projects a patterned radiation beam onto the substrate W. To reach the substrate W, the path of the radiation beam B passes from the projection system PS through an immersion liquid confined between the projection system PS and the substrate W by a fluid handling structure 12. The projection system PS has a lens element at the end of the beam path, which is in contact with the immersion liquid. This lens element in contact with the immersion liquid may be referred to as the "last lens element" or "final element". The final element is at least partially surrounded by the fluid handling structure 12. The fluid handling structure 12 may confine the immersion liquid below the final element and above the facing surface.

[0050] Figure 2a and Figure 2b The different features that may be present in variations of the fluid handling structure 12 are shown. Unless otherwise described, these designs may share the same Figure 2a and Figure 2b Some of the same features. As shown or as needed, the features described herein can be selected individually or in combination.

[0051] Figure 2a A fluid handling structure 12 is shown surrounding the bottom surface of the final element 100. The final element 100 has an inverted truncated cone shape. The truncated cone has a flat bottom surface and a conical surface. The truncated cone protrudes from the flat surface and has a bottom flat surface. The bottom flat surface is an optically active part of the bottom surface of the final element 100, through which the radiation beam B can pass. The final element 100 can have a coating 30. The fluid handling structure 12 surrounds at least a portion of the truncated cone. The fluid handling structure 12 has an inner surface facing the conical surface of the truncated cone. The inner surface and the conical surface have complementary shapes. The top surface of the fluid handling structure 12 is substantially flat. The fluid handling structure 12 can fit around the truncated cone of the final element 100. The bottom surface of the fluid handling structure 12 is substantially flat and, in use, the bottom surface can be parallel to the facing surface of the substrate support WT and / or substrate W. The distance between the bottom surface and the facing surface may be in the range of 30 to 500 microns, desirably in the range of 80 to 200 microns.

[0052] The fluid handling structure 12 extends closer to the facing surfaces of the substrate W and substrate support WT than the final element 100. A space 11 is defined between the inner surface of the fluid handling structure 12, the flat surface of the frustoconical portion, and the facing surface. During use, the space 11 is filled with immersion liquid. The immersion liquid fills at least a portion of the buffer space between the complementary surfaces of the final element 100 and the fluid handling structure 12, and in one embodiment, fills at least a portion of the space between the complementary inner surface and the conical surface.

[0053] Immersion liquid is supplied to the space 11 through openings formed in the surface of the fluid handling structure 12. The immersion liquid may be supplied through supply openings 20 in the inner surface of the fluid handling structure 12. Additionally or alternatively, immersion liquid is supplied from lower supply openings 23 formed in the lower surface of the fluid handling structure 12. The lower supply openings 23 may surround the path of the radiation beam B and may be formed by a series of openings in an array. Immersion liquid is supplied to fill the space 11 so that the flow through the space 11 under the projection system PS is laminar. Supplying immersion liquid from the openings 23 below the fluid handling structure 12 additionally prevents air bubbles from entering the space 11. This supply of immersion liquid acts as a liquid seal.

[0054] The immersion liquid can be recovered from the recovery openings 21 formed in the inner surface. The recovery of the immersion liquid through the recovery openings 21 can be performed by applying an underpressure; by recovering the immersion liquid through the recovery openings 21 due to the speed at which the immersion liquid flows through the space 11; or by both. When viewed in plan, the recovery openings 21 can be located on the opposite side of the supply opening 20. Additionally or alternatively, the immersion liquid can be recovered through an overflow opening 24 located on the top surface of the fluid handling structure 12. In one embodiment, the supply and recovery openings 20, 21 can interchange their functions (i.e., the flow direction of the liquid is reversed). This allows the flow direction to be changed according to the relative movement of the fluid handling structure 12 and the substrate W.

[0055] Additionally or alternatively, the immersion liquid may be recovered from beneath the fluid handling structure 12 via a recovery opening 25 formed in its bottom surface. The recovery opening 25 may be used to hold (or "pin") a meniscus 33 of the immersion liquid to the fluid handling structure 12. The meniscus 33 is formed between the fluid handling structure 12 and the facing surface and serves as a boundary between the liquid space and the gaseous external environment. The recovery opening 25 may be a porous plate from which the immersion liquid may be recovered in a single-phase flow. The recovery opening in the bottom surface may be a series of pin holes 32 through which the immersion liquid is recovered. The pin holes 32 may recover the immersion liquid in a two-phase flow.

[0056] Optional radially outward relative to the inner surface of the fluid handling structure 12 is an air knife opening 26. Gas can be supplied through the air knife opening 26 at an increased rate to help confine the immersion liquid in the space 11. The supplied gas can be humidified and can substantially contain carbon dioxide. Radially outward of the air knife opening 26 is a gas recovery opening 28 for recovering the gas supplied through the air knife opening 26. Other openings (e.g., open to the atmosphere or a gas source) may be present in the bottom surface of the fluid handling structure 12. For example, other openings may be present between the air knife opening 26 and the gas recovery opening 28 and / or between the nail hole 32 and the air knife opening 26.

[0057] Figure 2b As shown in Figure 2a Like features share like reference numerals.The fluid handling structure 12 has an inner surface that is complementary to the conical surface of the frustoconical shape.The lower surface of the fluid handling structure 12 is closer to the facing surface than the bottom flat surface of the frustoconical shape.

[0058] Immersion liquid is supplied to the space 11 through supply openings 34 formed in the inner surface of the fluid handling structure 12. The supply openings 34 are located towards the bottom of the inner surface (possibly below the bottom surface of the frusto-conical shape). The supply openings 34 are located around the inner surface and are spaced around the path of the radiation beam B.

[0059] The immersion liquid is recovered from the space 11 through the recovery opening 25 in the lower surface of the fluid handling structure 12. When the facing surface moves under the fluid handling structure 12, the meniscus 33 can migrate above the surface of the recovery opening 25 in the same direction as the movement direction of the facing surface. The recovery opening 25 can be formed by a porous member. The immersion liquid can be recovered in a single phase. In one embodiment, the immersion liquid is recovered as a two-phase flow. The two-phase flow is received in a chamber 35 within the fluid handling structure 12, and the two-phase flow is separated into liquid and gas in the chamber 35. The liquid and gas are recovered from the chamber 35 through independent channels 36 and 38.

[0060] An inner periphery 39 of the lower surface of the fluid handling structure 12 extends away from the inner surface into the space 11 to form a plate 40. The inner periphery 39 forms an aperture sized to match the shape and size of the radiation beam B. The plate 40 can be used to isolate immersion liquid on either side thereof. The supplied immersion liquid flows inwardly toward the aperture, through the internal holes, and then flows radially outwardly beneath the plate 40 toward the surrounding recovery openings 25.

[0061] In one embodiment, the fluid handling structure 12 may be as follows Figure 2bThe right-hand side of FIG shows two parts: an inner part 12a and an outer part 12b. The inner part 12a and the outer part 12b can move relative to each other in a plane parallel to the facing surfaces. The inner part 12a can have a supply opening 34 and can have an overflow recovery member 24. The outer part 12b can have a plate 40 and a recovery opening 25. The inner part 12a can have an intermediate recovery member 42 for recovering immersion liquid flowing between the inner part 12a and the outer part 12b.

[0062] The substrate support WT includes a substrate holder 200 configured to support a substrate W. Figure 3 An edge region of a substrate holder 200 and an associated substrate W (at the top) are illustrated in cross section at the top and in plan view at the bottom according to one embodiment. The substrate holder 200 comprises a body 210 having a body surface 212. In use, the body surface 212 faces the lower surface of the substrate W.

[0063] In the central area of the main body surface 212 ( Figure 3 In the left-hand side of FIG, a plurality of main burls 220 protrude from the main body surface 212. Each main burl 220 has a distal surface configured to support a substrate W. The main burls 220 are arranged in a plane relative to one another in a pattern. This pattern supports the substrate W and reduces any bending of the substrate W toward the main body surface 212 to an acceptable amount.

[0064] The area in the plane of each main burl 220 is relatively small compared to the area in the plane of the substrate W. Therefore, the main burl 220 only contacts a small area of the lower surface of the substrate W. This reduces the chance of contaminants being transferred from the substrate holder 200 to the substrate W.

[0065] A pressure differential is established across the substrate W. For example, the space between the body 210 of the substrate holder 200 and the substrate W is connected to an underpressure that is lower than the higher pressure above the substrate W. The pressure differential causes a force that holds the substrate W to the substrate holder 200 .

[0066] In an immersion lithography apparatus, liquid will be present adjacent to the edge of the substrate W at least some of the time during exposure of the substrate W. Due to the underpressure between the body 210 of the substrate holder 200 and the lower surface of the substrate W, this liquid will be drawn around the edge of the substrate W and underneath the substrate W. To reduce the occurrence of liquid contact with the lower surface of the substrate W (particularly in the region where the main burls 220 contact the substrate W), a first sealing member 230 is provided that protrudes from the body surface 212 of the body 210. The first sealing member 230 surrounds a plurality of the main burls 212. The first sealing member 230 is configured to restrict the passage of liquid radially inwardly through the first sealing member 230 between the substrate W and the body surface 212. The first sealing member 230 is a continuous (although not necessarily uniform in cross-section) barrier surrounding the main burls 220.

[0067] One purpose of the first sealing member 230 is to restrict the flow of gas (which may not be ideally humid) radially inward toward the main burl 220. This enables the generation of an underpressure around the main burl 220, which is necessary to clamp the substrate W to the substrate holder 200. Advantageously, some flow of gas over the first sealing member 230 is allowed so that the substrate W can be quickly removed from the substrate holder 200 when the underpressure source generating the underpressure around the main burl 220 is turned off. If the rate of gas flow through the first sealing member 230 is too slow, the pressure around the main burl 220 will equalize with the pressure above the substrate W, and the substrate W will take too long to be released.

[0068] The first sealing member 230 has an upper surface 232 that, during use, is configured to form a gap between it and the lower surface of the substrate W. That is, the upper surface 232 is configured to be somewhat closer to the main body surface 212 than the distal surface of the main burl 220. This is advantageous because this arrangement allows gas to be drawn onto the first sealing member 230 (below the substrate W) just before removing the substrate W, while allowing liquid to pass in the same direction. This is achieved without large-area contact with the lower surface of the substrate W (which could adversely cause contaminants to be transferred from the first sealing member 230 to the substrate W). This would also make removing the substrate W from the substrate holder 200 more problematic.

[0069] In plan view, the cross-sectional area of first sealing member 230 is much larger than that of main burl 220. In plan view, the relatively large area of first sealing member 230 results in greater resistance to the passage of liquid radially inwardly through first sealing member 230 between substrate W and body surface 212.

[0070] As in Figure 3As can be seen in FIG, the radially outermost main burl 220 of the plurality of main burls 220 is at a considerable distance from the edge of the substrate W. Without any other features supporting the substrate W radially outward of the radially outermost main burl 220, the edge of the substrate W may bend downward. This is due to the underpressure below the substrate W compared to above the substrate W. In the present invention, a plurality of small burls 240 are provided to support the substrate W radially outward of the radially outermost main burl 220. The small burls 240 protrude from the upper surface 232 of the first sealing member 230. Each small burl 240 has a distal surface configured to support the substrate W.

[0071] A plurality of burls 240 are circumferentially arranged along the first sealing member 230. The burls 240 may be spaced apart. The burls 240 may all be at the same or different radial distances from the center of the substrate holder 200. The cross-sectional area of each burl 240 in plan view is significantly smaller than that of the first sealing member. For example, the sum of the cross-sectional areas of the burls 240 on the first sealing member 230 may be significantly smaller than the total cross-sectional area of the first sealing member 230, for example, at least 10 or 15 times smaller.

[0072] Radially outwardly of the first sealing member 230 are a plurality of extraction openings 250. The extraction openings 250 are formed in the body 210. The extraction openings 250 are connected to an underpressure source. Thus, any liquid that reaches the extraction openings 250 is extracted through the body 210. This means that liquid is restricted from further entering the space between the body surface 212 and the substrate W. For example, when no liquid is to be extracted, the extraction openings 250 can also be used to extract gas. A mixture of liquid and gas can be extracted through the extraction openings 250.

[0073] The extraction openings 250 are spaced apart from each other all the way around the first sealing member 230. Figure 3 2 is shown as a discrete opening in the body surface 212, but this may not be the case. For example, a groove may be formed in the body surface 212, and the extraction opening 250 may emerge from the body 210 at the bottom of the groove. The groove may be segmented with one or more openings in each segment. Each segment can be considered a plurality of recesses.

[0074] By connecting the extraction opening 250 to underpressure, liquid that does reach the edge of the substrate W can be removed through the extraction opening 250. Once the edge of the substrate W is no longer covered by liquid, the lower surface of the substrate W is dried as the liquid is removed.

[0075] Radially outward of the extraction opening 250 is a second sealing member 260. The second sealing member 260 surrounds the extraction opening 250. The second sealing member 260 also surrounds the first sealing member 230.

[0076] The second sealing member 260 may have an upper surface 262 similar to the first sealing member 230, with a plurality of small protrusions 270 protruding from the upper surface 262. An advantage of providing a plurality of small protrusions 270 on the upper surface 262 of the second sealing member 260 is that the substrate W is supported closer to its edge. This further reduces deformation of the substrate W due to its edge being unsupported.

[0077] Despite Figure 3 In the embodiment shown, the burls 240 and 270 are shown on both the first sealing member 230 and the second sealing member 260, but this may not be the case. For example, the burl 240 may protrude only from the upper surface 232 of the first sealing member 230, or the burl 270 may protrude only from the upper surface 262 of the second sealing member 260. In both cases, deformation of the substrate W is reduced compared to a case where the burls 240 and 270 are not present.

[0078] Despite Figure 3 , a first sealing member 230 and a second sealing member 260 are shown, but it is also possible that only the first sealing member 230 or only the second sealing member 260 is present. If only the second sealing member 260 is present, the arrangement can be regarded as a first sealing member having a plurality of extraction openings 250 radially inwardly of the first sealing member. If in such an arrangement the first sealing member 230 is present radially inwardly of the extraction openings 250, it can be regarded as the second sealing member.

[0079] exist Figure 3In the embodiment of the present invention, during use, an underpressure is provided in the central region of the substrate holder 200 between the main surface 212 and the substrate W. This underpressure is the reason why the substrate W is clamped to the substrate holder 200. Compared to the underpressure in the area adjacent to the extraction opening 250, this clamping underpressure can have a lower magnitude (i.e., a less severe vacuum). This arrangement causes gas to flow radially outward from locations surrounding the main burl 220 toward the extraction opening 250, and fluid to flow radially inward from the edge of the substrate W toward the extraction opening 250. In this way, as the gas flows radially outward to locations adjacent to the extraction opening 250, liquid and humidified gas are restricted from moving radially inward beyond the location of the extraction opening 250. This reduces the extent to which liquid penetrates beneath the substrate W. Since there is no liquid or no liquid on the first sealing member 230, it is easier to remove the substrate W from the substrate holder 200, resulting in less wear. Wear is harmful because it can lead to contamination of the substrate W and changes in the clamping characteristics of the substrate holder 200, which can cause deformation of the substrate W. The presence of liquid between the main burl 220 and the bottom side of the substrate W may also cause wear (if the substrate holder 200 is ceramic) and possible friction changes. Deformation of the substrate W may cause imaging errors (e.g., overlay errors and / or focus errors), and contamination may also cause imaging errors. The presence of liquid on the bottom side of the substrate W is generally detrimental because it may cause thermal stability problems of the substrate W or difficulties when droplets are lost during unloading of the substrate W. Therefore, Figure 3 The substrate holder 200 alleviates some of these difficulties by providing appropriate additional support for the substrate edge, taking measures to keep the first sealing member 230 dry, and preventing the ingress of liquid radially inward through the extraction opening 250. Furthermore, by preventing the ingress of liquid through the extraction opening 250, a humid atmosphere is avoided between the body surface 212 and the substrate W. A disadvantage of a humid atmosphere is that the main burls 220 may oxidize. Oxidation of the main burls 220 is detrimental because it reduces the achievable flatness of the substrate W supported by the main burls 220.

[0080] Figure 4 Another embodiment of a substrate holder 200 according to the invention is shown. The figure shows the edge region of the substrate holder 200 in cross section at the top and in plan view at the bottom. In addition to the following, Figure 4 Examples and Figure 3 The same reference numerals are used to illustrate corresponding features.

[0081] exist Figure 4In an embodiment, a plurality of inlet openings 280 are formed in the main body surface 212. The inlet openings 280 are radially inward of the extraction openings 250. The inlet openings 280 are open to the atmosphere or connected to a gas source. As a result, a radially outward gas flow is created from the plurality of inlet openings 280 toward the plurality of extraction openings 250. This gas flow forms a barrier that prevents liquid and humid gas from radially inwardly entering below the substrate W. Since an underpressure is formed in the center of the substrate holder 200 for clamping the substrate W to the substrate holder 200, a radially inward gas flow is also created from the plurality of inlet openings 280. The underpressure generated in the center of the substrate holder 200 in the region of the main burl 220 can be the same as the underpressure generated above the extraction openings 250. The underpressure at the extraction openings 250 can be deeper (i.e., have a greater magnitude) than the underpressure at the main burl 220, thereby also causing a radially outward flow above the upper surface 232.

[0082] Depending on the depth of the groove between the first and second sealing members 230 and 260 , the main burls 220 (and / or the small burls 270 ) may be arranged alternately with the inlet opening 280 or the extraction opening 250 or between the inlet opening 280 and the extraction opening 250 .

[0083] A plurality of inlet openings 280 can be formed in the bottom of a groove in the body surface 212. The groove can be in the form of a continuous or discontinuous circumferential channel. Alternatively, as shown, the plurality of inlet openings 280 can be formed as a plurality of discrete openings in the body surface 212. The number, size, and spacing of the inlet openings 280 can be selected as desired. As shown, the number, size, and spacing of the inlet openings 280 can be similar to the number, size, and spacing of the extraction openings 250.

[0084] Since the gas leaving the inlet opening 280 can be dehumidified gas, this further reduces the humidity of the gas present around the main burl 220. Alternatively, in the case where the gas leaving the inlet opening 280 is drawn towards the extraction opening 250, humidified gas can be provided from the inlet opening 280. This reduces the evaporation of liquid in the resulting gas flow, thereby reducing the evaporation heat load on the bottom side of the substrate W and / or in the extraction opening 250 and further downstream. Providing the inlet opening 280 also allows the underpressure connected to the extraction opening 250 to be the same as the underpressure around the main burl 220. This is advantageous because the underpressure does not need to be lower than the underpressure around the main burl 220, thereby drawing more liquid from the edge of the substrate W below the substrate W, such as at Figure 3 In the embodiment of .

[0085] In one embodiment, the radially inward airflow toward the extraction opening 250 causes the surface liquid flow and the surface gas flow to reach a balance. This means that the liquid will flow downward on the outside of the through-hole forming the extraction opening 250, and the gas will flow on the inside of the through-hole. If there is any liquid, this type of two-phase flow will occur, and a smooth flow can be achieved. Ideally, in the absence of liquid, the underpressure determined by the flow restriction of the inlet opening 280 and the second sealing member 260 should be higher than the maximum capillary underpressure of the second sealing member 260. That is, the airflow is large enough to overcome the capillary pressure of the liquid in the gap between the upper surface 262 and the substrate W. If this condition is met, the airflow above the second sealing member 260 should always be sufficient to remove any liquid between the upper surface 262 of the second sealing member 260 and the substrate W. This is desirable because it allows the substrate W to be removed without having to overcome the attraction to the substrate holder 200 caused by the presence of liquid between the second sealing member 260 and the substrate W. As described above, there is no liquid between the first sealing member 230 and the substrate W. The absence of liquid between the first and second sealing members 230 and 260 and the substrate W will also increase the flatness of the substrate W.

[0086] Figure 5 The diagram shows the following Figure 4 Another embodiment of the same embodiment.

[0087] exist Figure 5 In the embodiment of the present invention, the width of the second sealing member 260 in the radial direction is greater than the width of the first sealing member 230. The extraction opening 250 is formed in the upper surface 262 of the second sealing member 260. As shown in the figure, the groove 252 is formed in the upper surface 262 of the second sealing member 260, and the extraction opening 250 is formed in the bottom of the groove 252.

[0088] like Figure 5 As shown, two small protrusions 270 are formed on the upper surface 262 of the second sealing member 260, on either side of the extraction opening 250. These small protrusions 270 may or may not be present, and may be present only on the radially inner side or the radially outer side of the extraction opening 250. As shown, the radially inner and outer small protrusions 270 on the second sealing member 260 may be aligned in the radial direction, or may be staggered relative to each other in the radial direction.

[0089] In a sense, Figure 5The embodiment of FIG. 2 is shown as having three sealing members, a first sealing member 230, a sealing member located radially inwardly of the extraction opening 250, and a third sealing member located radially outwardly of the extraction opening 250. This is further apparent if the depth of the groove 252 is such that its bottom surface is substantially coplanar with the body surface 212 of the body 210. In this view, the intermediate sealing member can be seen between the inlet opening 280 and the extraction opening 250, and between the first sealing member 230 and the second sealing member 260.

[0090] The main burls 220 (and / or the small burls 270 ) may be arranged alternately with the inlet openings 280 or the extraction openings 250 .

[0091] Figure 5 An advantage of this embodiment is that the gas flow flowing radially outward from the inlet opening 280 to the extraction opening 250 passes over the constriction between the upper surface 262 of the radially inward portion of the second sealing member 260 and the substrate W. This results in an acceleration of the gas flow, thereby enhancing the sealing capability because, if the force generated by the gas flow is greater than the capillary force of the liquid between the upper surface 232 and the substrate W, any liquid that does flow radially inward from the extraction opening 250 will be pushed back radially outward toward the extraction opening 250 by the accelerated gas flow.

[0092] exist Figure 5 In the embodiment of the present invention, a plurality of inlet openings 280 may be located in the first sealing member 230 instead of or in addition to the extraction openings 250 located in the second sealing member 260. Figure 5 The arrangement shown has similar advantages in that the airflow flowing radially outwards from the inlet opening 280 towards the extraction opening 250 must pass through the narrow gap between the first sealing member 230 and the substrate W, causing the airflow to be accelerated, thereby enhancing the sealing capability of the arrangement.

[0093] In an alternative embodiment, the groove 252 may be formed by Figure 6 The recess 284 depicted is replaced by a similar plurality of recesses and inlet opening 280 .

[0094] In addition to the following, Figure 6 Examples and Figure 5 The same as the embodiment.

[0095] exist Figure 6 In the embodiment of the present invention, the arrangement of the extraction opening 250 in the bottom of the groove 252 formed in the upper surface 262 of the second sealing member 260 is similar to that of the embodiment of the present invention. Figure 5 However, instead of providing an inlet opening 280 in the bottom of the deep recess between the first sealing member 230 and the second sealing member 260, Figure 6The inlet openings 280 in the embodiment of FIG are provided at the bottom of each recess 284 formed in the upper surface 232 of the first sealing member 230. This embodiment can be viewed as having a first sealing member 230 with the inlet openings 280 formed therein, a second sealing member 260 with no inlet or opening formed therein, and a shallow recess 252 with the extraction opening 250 formed in the bottom of the recess 252 between the first sealing member 230 and the second sealing member 260.

[0096] The recess 284 is a pressure divider and makes the airflow more defined in position. In addition, the recess 284 creates a tangential flow between the inlet openings 280. This tangential flow can remove liquid from between the inlet openings 280. This effect can also be achieved by using the groove 252.

[0097] Although the illustrated arrangement shows each recess 284 having a corresponding inlet opening 280 , the arrangement may be different whereby one recess 284 has two or more associated inlet openings 280 .

[0098] In this and all other embodiments, the burls 240 may be arranged alternately with the inlet openings 280, as described below. Figure 9 In the embodiment of the present invention, the outer burls 300 are arranged alternately with the extraction openings 250. Additionally or alternatively, the small burls 240 can be positioned radially inside and / or outside the inlet opening 280 and in line with the inlet opening 280 at the same radial distance from the center of the substrate holder 200.

[0099] In addition to the following, Figure 7 Examples and Figure 5 or Figure 6 The same as the embodiment.

[0100] exist Figure 7 In the embodiment of the present invention, a groove 290 is formed in the upper surface 232 of the first sealing member 230. The groove 290 does not have any opening in the bottom surface thereof.

[0101] like Figure 7 As shown in the lower half of FIG, the groove 290 can be shaped to form a labyrinth seal for a first passage of gas from the radially outer side of the first sealing member 230 to the radially inner side of the first sealing member 230. That is, the groove 290 extends along a tortuous path from the radially inner side of the first sealing member 230 to the radially outer side of the first sealing member 230. As with all other embodiments, the main burls 220 and / or the small burls 240, 270 can be arranged alternately with (and / or located radially inwardly / outwardly of) the inlet opening 280 and / or the extraction opening 250.

[0102] Figure 8 The diagram shows the following Figure 5 The same embodiment as the embodiment of the present invention.

[0103] exist Figure 8 In the embodiment of the present invention, instead of having the extraction opening 250 formed in the upper surface 262 of the second sealing member 260 and the inlet opening 280 formed between the first sealing member 230 and the second sealing member 260, the extraction opening 250 is formed between the first sealing member 230 and the second sealing member 260, and the inlet opening 280 is formed in the upper surface 232 of the first sealing member 230. Figure 5 Similar to the embodiment of the present invention, this can be viewed as an embodiment of three sealing members. A continuous groove or individual recesses may or may not be provided in the upper surface 232 of the first sealing member 230, wherein an inlet opening 280 is formed in the bottom surface of the groove or individual recesses, as shown in FIG. Figure 5 As shown and described around the extraction opening 250. On the upper surface 232 of the first sealing member 230, small knobs 240 are provided on the radially inner side or the outer side (or alternately) or the radially inner side and the outer side of the extraction opening 280. Similar to Figure 5 With reference to the burls 270 on the second sealing member 260 of the embodiment of FIG. 1 , the burls 240 may or may not be radially aligned.

[0104] Figure 9 The diagram shows the following Figure 8 The same embodiment as the embodiment of the present invention.

[0105] exist Figure 9 In the embodiment of FIG. 2 , a meniscus pinning feature 291 is provided in the upper surface 232 of the first sealing member 230 . The meniscus pinning feature 291 extends around an area of the main burl 220 . The meniscus pinning feature 291 is radially inward of the extraction opening 250 .

[0106] The meniscus pinning feature 291 has features such as sharp edges 292 that effectively pin the meniscus of the liquid in place. The meniscus pinning feature 291 applies a force to the meniscus, which means that additional energy is required for the meniscus to move past the meniscus pinning feature 291. In this way, there is further resistance to the radially inward movement of the liquid.

[0107] like Figure 8 In the embodiment of the present invention, the burl 240 can be in any position on the upper surface 232 of the first sealing member 230. Additionally or alternatively, the burl 270 can be present on the upper surface 262 of the second sealing member 260.

[0108] exist Figure 9In one embodiment, the extraction opening 250 is maintained at an underpressure that is greater than the underpressure applied in the region of the main burl 220. In one embodiment, an underpressure is also applied to the inlet opening 280. The magnitude of the underpressure applied to the inlet opening 280 is intermediate between the underpressure applied in the region of the main burl 220 and the underpressure applied to the extraction opening 250. In this manner, a gas flow is generated radially outward through the inlet opening 280. This radial outward flow of gas exerts another force on the liquid meniscus between the substrate W and the substrate holder 200.

[0109] Although meniscus pinning feature 291 is illustrated as a groove with sharp edge 292, any feature may be used as meniscus pinning feature 290. An alternative feature may be a change in the contact angle of upper surface 262 with the immersion liquid at the location of meniscus pinning feature 291.

[0110] Such as Figure 9 The meniscus pinning feature 291 shown in FIG. 2 can be used in any other embodiment. The location of the meniscus pinning feature 291 is preferably located radially inward of the extraction opening 250.

[0111] In addition to the following, Figure 10 Examples and Figure 3 The same as the embodiment.

[0112] exist Figure 10 In embodiments of the present invention, the small burls 240 and 270 are optional features. Alternatively or additionally, to support the edge of the substrate W radially further outward than the outermost main burl 220, a plurality of outer burls 300 are provided radially outward of the first sealing member 230. The plurality of outer burls 300 protrude from the main body surface 212. Each of the plurality of outer burls 300 has a distal surface configured to support the substrate W. As shown, the plurality of outer burls 230 can be disposed radially inward of the second sealing member 260. In one embodiment, the plurality of outer burls 300 are arranged alternately with the extraction openings 250 in a line surrounding the first sealing member 230 and the main burls 220.

[0113] In this way, the edge of the substrate W has support. This can reduce deformation of the substrate W at its outer edge. In one embodiment, the outer protrusion 300 can be located radially outside the second sealing member 260. Figures 3 to 9 and Figures 11 to 13 In the described embodiments, it is optional to provide Figure 10 The outer knob 300 is shown.

[0114] Figure 11 The diagram shows the following Figure 10 The same embodiment as the embodiment of the present invention.

[0115] Figure 11 Variations in the geometries of the first sealing member 230 and / or the second sealing member 260 illustrated in and described below may be applied to the first sealing member 230 and / or the second sealing member 260 of any embodiment.

[0116] exist Figure 11 In the embodiment of FIG. 2 , as can be seen from the lower portion of the figure, the second sealing member 260 follows a tortuous path around the circumference of the substrate holder 200. Figure 11 As shown, small burls 240 are formed on the top surface 232 of the first sealing member 230. The small burls 240 are positioned at the apex, for example, at the position where adjacent concave curved portions 320 meet. Therefore, a plurality of small burls 240 protrude from a portion of the first sealing member 230 that extends further from the center of the substrate holder 200 than other portions of the first sealing member 230. The first sealing member 230 and the second sealing member 260 can have any shape. It is desirable that the small burls 240 located on the first sealing member 230 be positioned on a circumferential line that has equal areas of the groove between the first sealing member 230 and the second sealing member 260 in its radially inward and radially outward directions. Therefore, the underpressure generated between the first sealing member 230 and the second sealing member 260 is equal on both sides of the line of the burls 240, so that there is no large bending moment introduced due to the larger underpressure in the area between the first sealing member 230 and the second sealing member 260.

[0117] In one embodiment, the first sealing member 230 is formed of a plurality of concave curved portions 320 joined together. In one embodiment, the second sealing member 260 has an overall shape in a plane, the overall shape being defined by a plurality of curved portions 310 having a radius smaller than the overall shape, the plurality of curved portions 310 being joined together to form the overall shape. The second sealing member 260 is formed of a plurality of convex curved portions 310 (relative to a radial direction from the interior to the exterior of the substrate holder 200).

[0118] An inlet opening 280 may also be provided between the first sealing member 230 and the second sealing member 260 , for example radially inwardly of the extraction opening 250 .

[0119] Figure 12 The embodiments incorporate Figure 6 Examples and Figure 11 Features of the embodiments.

[0120] Figure 12 The embodiment has a single sealing member 230. The single sealing member 230 is Figure 12 In the central plan and in Figure 12 The left-hand side section is shown in cross section with the right-hand side. Figure 12 The plane view is taken along line AA shown in FIG. Figure 12 The right-hand side diagram shows the Figure 12 A cross section taken along line BB in the plan view of .

[0121] Sealing member 230 includes a plurality of inlet openings 280 in upper surface 232. Extraction openings 250 are also formed in upper surface 232 of sealing member 230. Inlet openings 280 may be connected to a source of ambient pressure or an underpressure having a magnitude less than that to which extraction openings 250 are connected.

[0122] exist Figure 12 In the embodiment of the present invention, one or more first recesses 510 are formed in the upper surface 232 of the sealing member 230. Each of the first recesses 510 has at least one associated extraction opening 250. However, there may be more than one extraction opening 250 in the or each first recess 510.

[0123] One or more second recesses 520 are formed in the upper surface 232 of the sealing member 230. Each of the second recesses 520 has one or more corresponding inlet openings 280 formed therein. However, there may be more than one inlet opening 280 in the or each second recess 520.

[0124] The first recess 510 and the second recess 520 are shaped and positioned to result in a barrier 550 formed therebetween. The barrier 550 is configured to restrict the passage of liquid between the substrate W and the body surface 212 radially inwardly past the barrier 550.

[0125] Due to the relatively high gas pressure in the inlet opening 280, gas is drawn from the inlet opening 280 above the barrier 550 towards the extraction opening 250. As the gas flow passes over the barrier 550, it is accelerated, thereby forming an effective gas seal between the barrier 550 and the bottom side of the substrate W. The gas flow advantageously has a tangential component from the inlet opening 280 towards the extraction opening 250 so as to direct radially incoming fluid towards the extraction opening 250.

[0126] The relative positions of the plurality of extraction openings 250 and the inlet opening 280 and the size and shape of the blocking member 550 result in Figure 12 That is, due to the underpressure applied to the extraction opening 250, the fluid is sucked into the extraction opening 250 from the radially outer side of the sealing member 230 and gathers toward the extraction opening 250 by tangential movement.

[0127] In one embodiment, first extension 560 extends radially outward from barrier 550. Second extension 570 extends radially inward from barrier 550. First extension 560 and second extension 570 effectively define sidewalls of first recess 510 and second recess 520, respectively. First extension 560 bridges from barrier 550 to a radially outer portion of sealing member 230. Second extension 570 bridges from barrier 550 to a radially inner portion of sealing member 230.

[0128] Inlet openings 280 and extraction openings 250 alternate in the circumferential direction so that gas drawn from inlet openings 280 flows to extraction openings 250 on both sides of inlet opening 280. In this way, a tangential flow of gas is achieved substantially around the entire circumference of sealing member 230, resulting in excellent sealing performance.

[0129] Since each extraction opening 250 is formed in the first recess 510 and the extraction openings 250 are closely spaced from one another around the circumference of the sealing member 230 , the force to which the substrate W is subjected due to the underpressure applied to the extraction openings 250 is uniform in the circumferential direction, resulting in less deformation of the substrate W.

[0130] Since the inlet openings 280 are located in the bottoms of the corresponding second recesses 520 , the gas flowing out of the inlet openings 280 is diffused over a larger area of the blocking member 550 compared to a case where no inlet openings 280 are formed in the second recesses 520 .

[0131] Optionally, the inlet opening 280 is spaced radially outward from the extraction opening 250. This helps to divide the radially incoming fluid flow into two flows toward adjacent extraction openings 250. This division of the fluid flow toward one of the two extraction openings 250 is also facilitated by the shape of the barrier 550 and the (optional) presence of the first extension 560, as will be explained further below.

[0132] In order to allow the extraction opening 250 to be radially inside the inlet opening 280, the one or more first recesses 510 extend radially inwardly so that the innermost portion of the first recess 510 is closer to the center of the substrate holder 200 than the outermost portion of the one or more second recesses 520. The shapes of the first recess 510 and the second recess 520 include shapes that narrow tangentially toward the center of the substrate W in the case of the first recess 510 and narrow tangentially away from the center of the substrate W in the case of the second recess 520.

[0133] The barrier 550 can be considered to form the sidewalls of the first recess 510 on one side (radially outward) and the second recess 520 on the other side (radially inward). The sidewalls are formed by the collection of the first portion 552 and the second portion 554 of the barrier 550.

[0134] As the first and second portions 552, 554 extend in a radially inward direction, the collected first and second portions 552, 554 converge toward each other toward a respective first vertex 556. By positioning one of the plurality of extraction openings 250 adjacent to the first vertex 556, fluid flow is directed radially inward through the first and second portions 552, 554 and through the flow of gas from the inlet opening 280 toward the extraction opening 250. This directing of the fluid flow toward the extraction opening 250 results in better extraction efficiency for the extraction opening 250. The first extension 510 also assists gas flow by forming a tangential barrier to the fluid flow.

[0135] Adjacent sets of first and second portions 552, 554 also converge toward respective second apexes 558 of barrier 550 as they extend in a radially outward direction. Advantageously, each of second apexes 558 has an associated inlet opening 280.

[0136] The first extension portion 560 extends from the second vertex 558. The second extension portion 570 extends from the first vertex 556.

[0137] Also contributing to directing the fluid flow towards the extraction opening 250 is the overall shape of the sealing member 230 in plan view. That is, the radially outermost portion of the sealing member 230 varies in distance from the center of the substrate holder 200. This results in Figure 12 The extraction opening 250 is positioned to be circumferentially aligned with a portion of the sealing member 230 that extends further from the center of the substrate holder 200 than other portions of the sealing member 230. That is, an imaginary line (such as line AA) passing through the center of the substrate holder 200 passes through the extraction opening 250 and through the radially outermost portion of the sealing member 230. As shown in the figure, a similar arrangement is optional on the inner surface of the sealing member 230, where the inlet opening 280 is radially aligned with a portion of the sealing member 230 that extends closer to the substrate holder 200 than other portions of the sealing member 230.

[0138] Although not shown, for example, as discussed in conjunction with other embodiments of the present invention, Figure 12 The sealing member 230 of the embodiment may include a plurality of burls 240. The burls 240 may be positioned radially inwardly and / or radially outwardly of the extraction opening 250 and / or the inlet opening 280, or may be positioned substantially in line with the inlet opening 280 and / or the extraction opening 250.

[0139] In addition to forming only a single first recess 510, Figure 13 Examples and Figure 12That is, the first extension portion 560 is missing. Alternatively or additionally, the second extension portion 570 may be missing.

[0140] 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. Other possible applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like.

[0141] Although specific reference may be made herein to embodiments of the present invention in the context of lithographic apparatus, embodiments of the present invention may be used in other apparatus. Embodiments of the present invention may form part of mask inspection equipment, metrology equipment, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatuses may generally be referred to as lithographic tools. Such lithographic tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0142] 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 is not limited to optical lithography and may be used in other applications (e.g., imprint lithography) where the context permits.

[0143] Although specific embodiments of the present invention have been described above, it should be understood that the present invention may be practiced in ways other than those described. The above description is intended to be illustrative rather than restrictive. Therefore, it will be apparent to those skilled in the art that modifications may be made to the described invention without departing from the scope of the claims set forth below.

Claims

1. A substrate holder for use in a lithographic apparatus and configured to support a substrate, the substrate holder comprising: a main body having a main body surface; a plurality of first main burls protruding from the main body surface, each first main burl having a distal surface configured to support the substrate; a first sealing member protruding from the main body surface and having an upper surface, the first sealing member surrounding the plurality of first main burls; a second sealing member protruding from the main body surface at an edge region of the main body and having an upper surface, the edge region being located radially outward of the first sealing member; as well as A plurality of burls protrude from at least the upper surface of the second sealing member, wherein each burl has a distal surface configured to support the substrate. 2 . The substrate holder according to claim 1 , further comprising a plurality of inlet openings formed in the body between the first sealing member and the second sealing member, the plurality of inlet openings being open to atmosphere or connected to a gas source.

3. The substrate holder according to claim 1, further comprising a plurality of extraction openings formed therein, the plurality of extraction openings being used to extract fluid from between the body and the substrate into the body, the plurality of extraction openings being arranged radially outward of the first seal. The substrate holder according to claim 1 , wherein a width of the second sealing member in a radial direction is greater than a width of the first sealing member.

5. The substrate holder according to any one of claims 1 to 4, further comprising a third seal protruding from the body surface at the edge region of the body, the edge region being located radially outward of the second sealing member, the third seal having an upper surface.

6. The substrate holder of claim 5, further comprising a plurality of extraction openings formed therein for extracting fluid from between the body and the substrate into the body, wherein the plurality of extraction openings are arranged between the second seal and the third seal. 7 . The substrate holder of claim 3 , wherein the plurality of extraction openings are formed in the upper surface of the second seal.

8. The substrate holder of claim 5, wherein the substrate holder further comprises a plurality of additional burls protruding from the upper surface of the first seal or the third seal, and each additional burl has a distal surface configured to support the substrate.

9. The substrate holder according to any one of claims 1 to 4, further comprising a plurality of second main burls protruding from the main body surface, wherein each second main burl has a distal surface configured to support the substrate, the second main burls being located radially outward of the first seal. 10 . The substrate holder according to claim 9 , wherein the plurality of second main burls are arranged between the first seal and the second seal or radially outside the second seal.

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