Substrate holder for use in lithography equipment

Abstract

A substrate holder for use in a lithography device and configured to support a substrate, the substrate holder comprising: a body having a body surface; a plurality of main burls protruding from the body surface, wherein each main burl 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 burls and configured to limit a passage of liquid radially inwardly through the first sealing member between the substrate and the body surface; and a plurality of small burls protruding from the upper surface of the first sealing member, wherein each small burl has a distal surface configured to support the substrate.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 17196086.7 filed on October 12, 2017 and EP application 18163985.7 filed on March 26, 2018, the entire contents of which are incorporated herein by reference. 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 onto a substrate. A lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, 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 the 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 devices using, for example, radiation with a wavelength of 193nm, lithography devices 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 an immersion lithographic apparatus, an immersion liquid is placed in the space between the projection system of the apparatus and the substrate. The immersion liquid may find its way past the edge of the substrate to the lower surface of the substrate. This may be detrimental due to contamination of the lower surface of the substrate caused by the immersion liquid and / or thermal loads applied to the lower surface of the substrate at a location close to the edge of the substrate due to evaporation of the immersion liquid. A substrate holder configured to support the substrate may have features that reduce the amount and / or distance that the immersion liquid moves radially inward along the lower surface of the substrate. Such features may adversely affect the flatness and cleanliness of the substrate achieved and the 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 a channel for liquid to pass 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 being configured to limit a 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 being configured to limit a 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 surrounding 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 lithography device and configured to support a substrate is provided, the substrate holder comprising: a body having a body surface; a plurality of main protuberances protruding from the body surface, wherein each main protuberance 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 protuberances and configured to limit a passage of liquid radially inwardly through the first sealing member between the substrate and the body surface; a plurality of small protuberances protruding from the upper surface of the first sealing member, wherein each small protuberance has a distal surface configured to support the substrate; and a plurality of small protuberances protruding from the upper surface of the first sealing member. 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 A schematic overview of a lithographic apparatus is depicted;

[0014] Figure 2a and Figure 2b Depicted in cross-section are two different versions of a fluid handling structure with 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] Fig. 9 depicts a schematic overview of the edge of a substrate holder 200 according to the present invention;

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

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

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

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

[0026] In this document, the terms "radiation" and "beam" are used to cover 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] The terms "reticle", "mask" or "patterning device" as used herein may be broadly interpreted as referring 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.), other examples of 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 an illuminator) IL configured to condition a radiation beam B (e.g., UV radiation or DUV radiation), a mask support (e.g., a mask stage) MT configured to support a patterning device (e.g., a 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., a wafer stage) WT configured to hold a substrate (e.g., a wafer coated with a resist) 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 onto a target portion C (e.g., comprising one or more dies) of the substrate W through the patterning device MA.

[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., use of immersion liquid or use of 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 (e.g. water) having a relatively high refractive index so as to fill a 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 located 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 may comprise a measuring table. The measuring table is arranged to hold sensors and / or cleaning means. The sensors may be arranged to measure properties of the projection system PS or properties of the radiation beam B. The measuring table may hold a plurality of sensors. The cleaning means may be arranged to clean a part of the lithographic apparatus, for example a part of the projection system PS or a part of a system for providing immersion liquid. The measuring table may be moved under 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 precisely moved, for example in order to position different target portions C in the path of the radiation beam B at focus and alignment positions. Similarly, a first positioner PM and possibly another position sensor (in 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 as shown occupy dedicated target portions, they can be located in the space between target portions. When the substrate alignment marks P1, P2 are located between the target portions C, they are called scribe alignment marks.

[0035] In order to illustrate the present invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes, i.e., an x-axis, a y-axis, and a z-axis. Each of the three axes is orthogonal to the other two axes. The rotation around the x-axis is called an Rx rotation. The rotation around the y-axis is called an Ry rotation. The rotation around 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 a 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 liquid layer of an immersion liquid having a relatively high refractive index is inserted in the space 11 between the projection system of the apparatus (through which a patterned beam is projected towards the substrate W) and the substrate W. The immersion liquid covers at least the portion of the substrate below the final element of the projection system PS. Thus, at least the portion of the substrate W that is subjected to exposure is immersed in the immersion liquid. Because the wavelength of the exposure radiation in the liquid will be shorter than that in the gas, the effect of the immersion liquid is to enable smaller features to be imaged. (The effect of the immersion liquid can also be seen 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 an immersion system, the UPW is often purified and it may undergo additional processing steps before being supplied to the immersion space 11 as an immersion liquid. In addition to water being used as an immersion liquid, other liquids with a high refractive index may be used, for example: hydrocarbons such as fluorinated hydrocarbons; and / or aqueous solutions. Furthermore, it has been envisioned that other fluids besides liquids may be used for immersion lithography.

[0038] In this specification, reference will be made in the description to partial immersion in which the 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 a support table (or substrate support WT) which 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 additionally or alternatively refers 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 with 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 have been envisaged, for example, unconfined immersion systems (so-called "all-wet" immersion systems) and bath immersion systems. In an unconfined immersion system, the immersion liquid covers a greater area than the surface beneath the final component. The liquid outside the immersion space 11 is present in the form of a thin liquid film. The liquid may cover the entire surface of the substrate W or even the substrate W and a substrate support WT coplanar with the substrate W. In a bath system, 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 immersion liquid to the immersion space 11. It includes features that are part of a fluid supply system. The arrangement disclosed in PCT Patent Application Publication No. WO99 / 49504 is an early fluid handling structure that includes conduits that supply or withdraw immersion liquid from the space 11 and that operate in accordance with 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, so as to partially define the space 11.

[0041] The fluid handling structure 12 may have a selection of different functions. Each function may be derived from a corresponding feature that enables the fluid handling structure 12 to perform that function. The fluid handling structure 12 may be referred to by many different terms, each referring to a function, for example, 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 gas 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 thus 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 gas flow, 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 the substrate W, the projection system PS projects a patterned radiation beam onto the substrate W. In order to reach the substrate W, the path of the radiation beam B passes from the projection system PS through an immersion liquid confined by a fluid handling structure 12 between the projection system PS and the substrate W. The projection system PS has a lens element at the end in 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 a "last lens element" or a "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 1 and 2 illustrate different features that may be present in variations of the fluid handling structure 12. Unless otherwise described, these designs may share similarities to those of FIG. Figure 2a and Figure 2b Some of the same features. The features described herein may be selected individually or in combination as shown or as desired.

[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. 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 portion of the bottom surface of the final element 100, through which the radiation beam B can pass. The final element 100 may 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 the 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 part of the buffer space between the complementary surfaces between the final element 100 and the fluid handling structure 12 and, in an embodiment, fills at least part 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, the 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. The supply of immersion liquid acts as a liquid seal.

[0054] The immersion liquid can be recovered from the recovery opening 21 formed in the inner surface. The recovery of the immersion liquid through the recovery opening 21 can be performed by applying an underpressure; recovering through the recovery opening 21 due to the speed of the immersion liquid flowing through the space 11; or recovering by both. When viewed in a plan view, the recovery opening 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 speed 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 which 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 frustoconical bottom surface). 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, 38.

[0060] The 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, the size of which may match the shape and size of the radiation beam B. The plate 40 may be used to isolate immersion liquid at either side thereof. The supplied immersion liquid flows inwardly towards the aperture, through the internal aperture, and then flows radially outwardly under the plate 40 to the surrounding recovery openings 25.

[0061] In one embodiment, the fluid handling structure 12 may be Figure 2bThe right hand side of the is shown in 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 it 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) according to an embodiment is illustrated in cross section at the top and in plan view at the bottom. The substrate holder 200 comprises a body 210 having a body surface 212. The body surface 212 faces a lower surface of a substrate W in use.

[0063] In the central area of ​​the main body surface 212 ( Figure 3 2 ), 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 another burl in a pattern. The pattern is such that the substrate W is supported and any bending of the substrate W toward the main body surface 212 is reduced 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 a 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, at least some of the time during exposure of the substrate W, liquid will be present adjacent to the edge 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. In order to reduce the occurrence of liquid contacting the lower surface of the substrate W (particularly at the area 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 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 around 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 inwards towards the main burl 220. This enables the generation of an underpressure around the main burl 220, which is necessary for clamping 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 source of the underpressure generating the underpressure around the main burl 220 is turned off. If the speed of the gas flow through the first sealing member 230 is too low, it takes too long for the pressure around the main burl 220 to equalize with the pressure above the substrate W, thereby releasing the substrate W.

[0068] The first sealing member 230 has an upper surface 232, which is configured to form a gap between it and the lower surface of the substrate W in use. That is, the upper surface 232 is configured to be closer to the main body surface 212 to some extent than the distal surface of the main protuberance 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 the liquid to pass in the same direction. This is achieved without large-area contact with the lower surface of the substrate W (harmfully causing contaminants to be transferred from the first sealing member 230 to the substrate W). This will also make it more problematic to remove the substrate W from the substrate holder 200.

[0069] In plan view, the cross-sectional area of ​​first sealing member 230 is much larger than the cross-sectional area 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 320, the most radially outer main burl 220 is at a considerable distance from the edge of the substrate W. Without any other features supporting the substrate W radially outside the most radially outer main burl 220, downward bending of the edge of the substrate W may occur. This is due to the underpressure below the substrate W compared to above the substrate W. In the present invention, in order to support the substrate W radially outside the most radially outer main burl 220, a plurality of small burls 240 are provided. 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 small protuberances 240 are arranged circumferentially along the first sealing member 230. The plurality of small protuberances 240 may be spaced apart. The plurality of small protuberances 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 small protuberance 240 in a plan view is much smaller than that of the first sealing member. For example, the sum of the cross-sectional areas of the plurality of small protuberances 240 on the first sealing member 230 is much smaller than the total cross-sectional area of ​​the first sealing member 230, for example, at least 10 times 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 reaching the extraction openings 250 is extracted through the body 210. This means that the liquid is restricted from further entering the space between the body surface 212 and the substrate W. For example, when there is no liquid to be extracted, the extraction openings 250 can also 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 3 212, 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 may be considered a plurality of recesses.

[0074] By connecting the extraction opening 250 to an 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 protuberances 270 protruding from the upper surface 262. An advantage of providing a plurality of small protuberances 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 not being supported.

[0077] Despite Figure 3 In the embodiment of the present invention, the small protuberances 240, 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 small protuberances 240 may protrude only from the upper surface 232 of the first sealing member 230, or the small protuberances 270 may protrude only from the upper surface 262 of the second sealing member 260. In both cases, the deformation of the substrate W is reduced compared to the case where the small protuberances 240, 270 are not present.

[0078] Despite Figure 3 2 shows a first sealing member 230 and a second sealing member 260, 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 inside the first sealing member. If in such an arrangement there is a first sealing member 230 radially inside the extraction openings 250, it can be regarded as a second sealing member.

[0079] exist Figure 3In the embodiment of the invention, in use, an underpressure is provided in the central region of the substrate holder 200 between the main surface 212 and the substrate W. The underpressure is the reason why the substrate W is clamped to the substrate holder 200. Compared with the underpressure at the region adjacent to the extraction opening 250, the clamped underpressure can have a lower amplitude (i.e., a less severe vacuum). The arrangement causes the gas to flow radially outward from the position around the main protrusion 220 toward the extraction opening 250, and the fluid flows radially inward from the edge of the substrate W toward the extraction opening 250. In this way, since the gas flows radially outward to the position adjacent to the extraction opening 250, the liquid and the humidified gas are restricted from moving radially inward further than the position of the extraction opening 250. Thus, the degree of liquid penetration below the substrate W is reduced. 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, thereby generating less wear. Wear is harmful because it can cause contamination of the substrate W and changes in the clamping characteristics of the substrate holder 200, thereby causing 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. Deformations of the substrate W may cause imaging errors (e.g., overlay errors and / or focus errors), as may contamination. The presence of liquid on the bottom side of the substrate W is generally detrimental, as it may cause thermal stability problems for the substrate W or difficulties when droplets are lost during unloading of the substrate W. Therefore, Figure 3 The substrate holder 200 of the present invention alleviates some of these difficulties by providing additional support for the substrate edge as appropriate, taking measures to keep the first sealing member 230 dry, and preventing the ingress of liquid radially inward through the extraction opening 250. In addition, a humid atmosphere between the body surface 212 and the substrate W is avoided by preventing the ingress of liquid through the extraction opening 250. A disadvantage of a humid atmosphere is that the main burls 220 may be oxidized. 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 of the present invention, 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 gas flow radially outward from the plurality of inlet openings 280 toward the plurality of extraction openings 250 is created. The gas flow forms a barrier that blocks liquid and humid gases from entering radially inward below the substrate W. Since an underpressure for clamping the substrate W to the substrate holder 200 is formed in the center of the substrate holder 200, a gas flow radially inward from the plurality of inlet openings 280 is also created. 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 amplitude) 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 sealing member 230 and the second sealing member 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, a 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 may be dehumidified gas, this further reduces the humidity of the gas present around the main burl 220. Alternatively, in case the gas leaving the inlet opening 280 is drawn towards the extraction opening 250, humidified gas may be provided from the inlet opening 280. This reduces 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 gas flow 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 inner side 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 gas flow 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 gas flow above the second sealing member 260 should always be enough 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 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 sealing member 230 and the second sealing member 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 protuberances 270 are formed on the upper surface 262 of the second sealing member 260, on either side of the extraction opening 250. These small protuberances 270 may be present or absent, 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 protuberances 270 on the second sealing member 260 may be arranged in the radial direction, or may be staggered relative to each other in the radial direction.

[0089] In a sense, Figure 5250 and a third sealing member located radially outward from the extraction opening 250. This will be more 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 the 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. This arrangement has the same Figure 5 The arrangement shown has similar advantages in that the gas flow flowing radially outwards from the inlet opening 280 to the extraction opening 250 must pass through the narrow gap between the first sealing member 230 and the substrate W, causing the gas flow to be accelerated, thereby enhancing the sealing ability of the arrangement.

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

[0094] Except as described below, 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 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 opening 280 in the embodiment of is disposed 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 an inlet opening 280 formed therein, a second sealing member 260 with no inlet or opening formed therein, and a shallow recess 252 with an 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. The tangential flow can remove liquid from between the inlet openings 280. This effect can also be achieved 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. Fig. 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 may 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] Except as described below, 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 the figure, the groove 290 can have a shape to form a labyrinth seal for the 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 the inlet opening 280 and / or the extraction opening 250 (and / or located radially inside / outside thereof).

[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 , which 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 reference 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] Fig. 9 The diagram shows the following Figure 8 The same embodiment as the embodiment of the present invention.

[0105] exist Fig. 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 a region 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 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 Fig. 9In an embodiment of the invention, the extraction opening 250 is kept under an underpressure which is greater than the underpressure applied in the region of the main burl 220. In an embodiment, an underpressure is also applied to the inlet opening 280. The magnitude of the underpressure applied to the inlet opening 280 is between the underpressure applied in the region of the main burl 220 and the underpressure applied to the extraction opening 250. In this way, 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 for 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 in Fig. 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] Except as described below, Fig.10 Examples and Figure 3 The same as the embodiment.

[0112] exist Fig.10 In an embodiment of the present invention, the small protuberances 240, 270 are optional features. Alternatively or additionally, in order to support the edge of the substrate W radially further outward than the outermost main protuberance 220, a plurality of outer protuberances 300 are provided radially outside the first sealing member 230. The plurality of outer protuberances 300 protrude from the main body surface 212. Each of the plurality of outer protuberances 300 has a distal surface configured to support the substrate W. As shown in the figure, the plurality of outer protuberances 230 can be disposed radially inside the second sealing member 260. In one embodiment, the plurality of outer protuberances 300 are alternately arranged with the extraction openings 250 on a line around the first sealing member 230 and the main protuberances 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 burl 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 possible to optionally provide Fig.10 The outer burl 300 is shown.

[0114] Fig.11 The diagram shows that in addition to the Fig.10 The same embodiment as the embodiment of the present invention.

[0115] Fig.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 Fig.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. Fig.11 As shown, a small burl 240 is formed on the top surface 232 of the first sealing member 230. The small burl 240 is positioned at the vertex, for example, at the position where the 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 farther 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 may have any shape. It is desirable that the small burl 240 located on the first sealing member 230 is positioned on a circumferential line that has an equal area of ​​a groove between the first sealing member 230 and the second sealing member 260 radially inward and radially outward therefrom. 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 small burl 240, so that there is no large bending moment introduced due to the larger underpressure in the region 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 (with respect to a radial direction from the inside to the outside 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] Fig.12 The embodiments incorporate Figure 6 Embodiments and Fig.11 Features of an embodiment.

[0120] Fig.12 The embodiment has a single sealing member 230. The single sealing member 230 is Fig.12 In the central plan and in Fig.12 The left-hand side cross section is shown in Figure 1. Fig.12 The plane view is taken along line AA. Fig.12 The right-hand side diagram shows the Fig.12 A cross section taken along line BB in the plan view of .

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

[0122] exist Fig.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 being formed between the first recess 510 and the second recess 520. The barrier 550 is configured to restrict the passage of liquid between the substrate W and the body surface 212 radially inwardly through 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. The gas flow is accelerated as it passes over the barrier 550, 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 Fig.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, the first extension 560 extends radially outward from the barrier 550. The second extension 570 extends radially inward from the barrier 550. The first extension 560 and the second extension 570 effectively define the sidewalls of the first recess 510 and the second recess 520, respectively. The first extension 560 bridges from the barrier 550 to the radially outer portion of the sealing member 230. The second extension 570 bridges from the barrier 550 to the radially inner portion of the 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 openings 280. In this way, 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 each other 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 opening 280 is located in the bottom of the corresponding second recess 520 , the gas flowing out from the inlet opening 280 is diffused over a larger area of ​​the blocking member 550 compared to a case where the inlet opening 280 is not formed in the second recess 520 .

[0131] Optionally, the inlet opening 280 is spaced radially outward of the extraction opening 250. This helps to split the radially incoming fluid flow into two flows towards adjacent extraction openings 250. This splitting of the fluid flow towards 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 a shape that narrows tangentially toward the center of the substrate W in the case of the first recess 510 and narrows tangentially away from the center of the substrate W in the case of the second recess 520.

[0133] The stopper 550 can be considered to form the sidewall of the first recess 510 on one side (radially outward) and the sidewall of the second recess 520 on the other side (radially inward). The sidewall is formed by the collection of the first part 552 and the second part 554 of the stopper 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 inwardly 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 of the extraction opening 250. The first extension 510 also assists the gas flow because it forms 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 fluid flow toward 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 Fig.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, on the inner surface of the sealing member 230, a similar arrangement is optional, wherein 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, Fig.12 The sealing member 230 of the embodiment may include a plurality of burls 240. The burls 240 may be positioned radially inward and / or radially outward 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, Fig.13 Examples and Fig.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 embodiments of the invention may be specifically referenced herein in the context of lithographic equipment, embodiments of the invention may be used in other equipment. Embodiments of the invention may form part of a mask inspection device, a metrology device, or any device that measures or processes an object such as a wafer (or other substrate) or a mask (or other patterning device). These devices 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 (eg 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 a manner other than that 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 support for use in a lithographic apparatus and configured to support a substrate, the substrate support comprising: a main body having a main body surface; a plurality of first burls protruding from the body surface, each first burl having a distal surface configured to support the substrate; a first sealing member protruding from a surface of the body at an edge region of the body and having an upper surface arranged to be spaced apart from the substrate by a first gap when the substrate is supported by the plurality of first protrusions, the first sealing member surrounding the plurality of first protrusions; a plurality of second burls arranged radially outward of the first sealing member, each second burl having a distal surface configured to support the substrate; a second sealing member protruding from the body surface at the edge region of the body and having an upper surface arranged to be spaced apart from the substrate by a second gap when the substrate is supported by the plurality of first burls, the second sealing member surrounding the first sealing member and the plurality of second burls and arranged below the substrate, and the first gap being arranged to be fluidically connected to the second gap when the substrate is supported by the plurality of first burls; as well as At least one extraction opening for extracting fluid from between the body and the substrate into the body, the at least one extraction opening being arranged between the first sealing member and the second sealing member or in the upper surface of the second sealing member. 2 . The substrate holder according to claim 1 , further comprising at least one third burl disposed radially outward of the second sealing member, the at least one third burl having a distal surface configured to support the substrate. 3 . The substrate holder of claim 1 , wherein the at least one extraction opening comprises a plurality of extraction openings formed in the body for extracting fluid from between the body and the substrate into the body. 4 . The substrate holder according to claim 3 , wherein the plurality of extraction openings are arranged between the first sealing member and the second sealing member. 5 . The substrate holder according to claim 3 , wherein the plurality of extraction openings and at least one second burl of the plurality of second burls are alternately arranged on a line surrounding the first sealing member and the plurality of first burls. 6 . The substrate holder of claim 3 , wherein the plurality of extraction openings are in the upper surface of the second sealing member. 7 . The substrate holder according to claim 6 , wherein each extraction opening is formed at a bottom surface of an extraction groove formed in the second sealing member. 8 . The substrate holder according to claim 6 , wherein each extraction opening is formed at a bottom surface of a corresponding recess formed in the upper surface of the second sealing member.

9. The substrate holder of claim 3, further comprising a plurality of inlet openings formed in the body radially inwardly of the plurality of extraction openings, the plurality of inlet openings being open to atmosphere or connected to a gas source.

10. The substrate holder of claim 9, wherein the plurality of inlet openings are formed in the body surface radially outwardly of the first sealing member.

11. The substrate holder of claim 9, wherein the plurality of inlet openings are in the upper surface of the first sealing member. 12 . The substrate holder according to claim 9 , wherein the plurality of inlet openings are provided at the bottoms of respective recesses formed in the upper surface of the first sealing member.

13. The substrate holder according to any one of claims 1 to 12, further comprising a plurality of burls, wherein at least one of the burls protrudes from the upper surface of the first sealing member, and each burl has a distal surface configured to support the substrate. 14 . The substrate holder of claim 13 , wherein at least one of the burls protrudes from the upper surface of the second sealing member. 15 . The substrate holder according to claim 14 , wherein at least one of the burls of the first sealing member and at least one of the burls of the second sealing member are aligned in a radial direction or staggered relative to each other in the radial direction, respectively.

16. The substrate holder according to any one of claims 1 to 12, further comprising a groove formed in the upper surface of the first sealing member, wherein the groove provides a tortuous path for gas from a radially outer side of the first sealing member to a radially inner side of the first sealing member.

17. A substrate holder according to claim 13, wherein the first sealing member has an overall shape in a plane so that the distance of the radially outermost portion of the first sealing member from the center of the substrate holder varies around the periphery of the substrate holder, and wherein the plurality of small protrusions protrude from a portion of the first sealing member that extends farther from the center of the substrate holder than other portions of the first sealing member.

18. The substrate holder according to any one of claims 1 to 12, further comprising a meniscus pinning feature on the upper surface of the first sealing member.

19. A substrate support for use in a lithographic apparatus and configured to support a substrate, the substrate support comprising: a main body having a main body surface; a plurality of burls protruding from the body surface, wherein each burl has a distal surface configured to support the substrate; a first sealing member protruding from a surface of the body at an edge region of the body and having an upper surface arranged to be spaced apart from the substrate by a first gap when the substrate is supported by the plurality of burls, the first sealing member surrounding the plurality of burls; a plurality of burls protruding from the upper surface of the first sealing member, wherein each burl has a distal surface configured to support the substrate; a second sealing member protruding from the body surface at the edge region of the body and having an upper surface arranged to be spaced apart from the substrate by a second gap when the substrate is supported by the plurality of burls, the second sealing member surrounding the first sealing member and arranged below the substrate, and the first gap being arranged to be fluidically connected to the second gap when the substrate is supported by the plurality of burls; as well as At least one extraction opening for extracting fluid from between the body and the substrate into the body, the at least one extraction opening being arranged between the first sealing member and the second sealing member or in the upper surface of the second sealing member.

20. The substrate holder of claim 19, wherein the at least one extraction opening comprises a plurality of extraction openings formed in the body for extracting fluid from between the body and the substrate into the body.

21. The substrate holder of claim 20, wherein the plurality of extraction openings are arranged radially outside the first sealing member. 22 . The substrate holder of claim 19 , wherein the substrate holder further comprises a plurality of second burls protruding from the upper surface of the second sealing member, and each second burl has a distal surface configured to support the substrate.

23. The substrate holder of claim 20, wherein the plurality of extraction openings are in the upper surface of the second sealing member. 24 . The substrate holder according to claim 23 , wherein each extraction opening is formed at a bottom surface of an extraction groove formed in the second sealing member. 25 . The substrate holder according to claim 23 , wherein each extraction opening is formed at a bottom surface of a corresponding recess formed in the upper surface of the first sealing member.

26. The substrate holder of claim 21, wherein the plurality of extraction openings are in the body surface between the first sealing member and the second sealing member.

27. The substrate holder of claim 20, further comprising a plurality of inlet openings formed in the body radially inwardly of the plurality of extraction openings, the plurality of inlet openings being open to atmosphere or connected to a gas source.

28. The substrate holder of claim 27, wherein the plurality of inlet openings are formed in the body surface radially outwardly of the first sealing member.

29. The substrate holder of claim 27, wherein the plurality of inlet openings are in the upper surface of the first sealing member.

30. The substrate holder of claim 27, wherein the plurality of inlet openings are disposed at the bottom of respective recesses formed in the upper surface of the first sealing member.

31. The substrate holder according to any one of claims 19 to 30, further comprising a plurality of external protrusions protruding from the body surface, wherein each external protrusion has a distal surface configured to support the substrate, the external protrusions being radially outward of the first sealing member.

32. The substrate holder of claim 31, wherein the outer burls and the extraction openings are alternately arranged on a line surrounding the first sealing member and the plurality of burls.

33. The substrate holder according to any one of claims 19 to 30, further comprising a groove formed in the upper surface of the first sealing member, wherein the groove provides a tortuous path for gas from the radially outer side of the first sealing member to the radially inner side of the first sealing member.

34. A substrate holder according to any one of claims 19 to 30, wherein the first sealing member has an overall shape in a plane such that a radially outermost portion of the first sealing member varies in distance from a center of the substrate holder around the periphery of the substrate holder, and wherein the plurality of small protrusions protrude from a portion of the first sealing member that extends further from the center of the substrate holder than other portions of the first sealing member.

35. The substrate holder of any one of claims 19 to 30, further comprising a meniscus pinning feature on the upper surface of the first sealing member.

36. A substrate support for use in a lithographic apparatus and configured to support a substrate, the substrate support comprising: a main body having a main body surface; a plurality of burls projecting from the main body surface, wherein each main burl has a distal surface configured to support the substrate; a first sealing member protruding from a surface of the body at an edge region of the body and having an upper surface arranged to be spaced apart from the substrate by a first gap when the substrate is supported by the plurality of burls, the first sealing member surrounding the plurality of burls; a second sealing member, protruding from the body surface at an edge region of the body and having an upper surface arranged to be spaced apart from the substrate by a second gap when the substrate is supported by the plurality of burls, the second sealing member surrounding the first sealing member, the second sealing member being arranged below the substrate, and the first gap being arranged to be fluidically connected to the second gap when the substrate is supported by the plurality of burls; a third sealing member protruding from the main body surface, the third sealing member surrounding the first sealing member and the second sealing member; a plurality of inlet openings formed in the body between the first sealing member and the second sealing member; as well as A plurality of extraction openings are 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.

37. A lithographic apparatus comprising a substrate holder according to any one of claims 1 to 36.

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