Substrate holder for use in lithography device

Abstract

To provide a substrate holder having acceptable compromise between performance of the substrate holder at a viewpoint of surface smoothness and cleanliness of a substrate and reduction of movement of an immersion liquid along an undersurface of the substrate.SOLUTION: The substrate holder is configured to support the substrate for use in a lithography device. The substrate holder includes: a main body having a body surface; a plurality of main bars protruding from the body surface, each main bar of which has a distal end face configured to support the substrate; a first seal member which protrudes from the body surface, has a top face, and is configured so as to surround the plurality of the main bars and suppress passing of a liquid existing between the substrate and the body surface past the first seal member and flowing to the inside in a radial direction; and a plurality of minor bars protruding from the top face of the first seal member, each minor bar of which has a distal end face configured to support the substrate.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS)

[0001] This application claims priority to EP Application No. 17196086.7, filed October 12, 2017, and EP Application No. 18163985.7, filed March 26, 2018, which are incorporated herein by reference in their entireties.

[0002] The present invention relates to a substrate holder for use in a lithographic apparatus. [Background technology]

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus can, for example, project a pattern (often called a "design layout" or "design") in a patterning device (e.g. mask) onto a layer of radiation-sensitive material (resist) provided on the substrate (e.g. wafer).

[0004]

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements are constantly shrinking while the amount of functional elements, such as transistors, per device has been steadily increasing for decades, following a trend commonly referred to as "Moore's Law". To keep up with Moore's Law, the semiconductor industry is seeking technologies that can produce smaller and smaller features. To project a pattern onto a substrate, a lithography apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features that can be patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm. Using lithography apparatus using extreme ultraviolet (EUV) radiation with wavelengths in the range of 4 nm to 20 nm, e.g., 6.7 nm or 13.5 nm, smaller features can be formed on a substrate than lithography apparatus using radiation with a wavelength of, e.g., 193 nm.

[0005]

[0005] In an immersion lithography apparatus, immersion liquid is present in a space between the projection system of the apparatus and the substrate. This immersion liquid may reach beyond the edge of the substrate to the underside of the substrate. This may be harmful due to contamination of the underside of the substrate by the immersion liquid and / or due to thermal loads imposed on the underside of the substrate at locations near the edge of the substrate due to evaporation of the immersion liquid. A substrate holder configured to support a substrate may have features that reduce the amount and / or distance that the immersion liquid travels radially inwards along the underside of the substrate. Such features may adversely affect the flatness and cleanliness achieved on the substrate, as well as the ease of removal. Summary of the Invention

[0006]

[0006] The object of the present invention is to provide a substrate holder that has an acceptable compromise between substrate holder performance in terms of substrate flatness and cleanliness and reduction of immersion liquid movement along the underside of the substrate.

[0007]

[0007] In one embodiment of the present invention, there is provided a substrate holder for use in a lithographic apparatus, 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, each main burl having a distal end face configured to support a substrate, a first seal member protruding from the body surface and having an upper surface, the first seal member surrounding the plurality of main burls and configured to inhibit liquid between the substrate and the body surface from flowing radially inwardly past the first seal member, and a plurality of minor burls protruding from the upper surface of the first seal member, each minor burl having a distal end face configured to support a substrate.

[0008] In one embodiment of the present invention, there is provided a substrate holder configured to support a substrate, for use in a lithographic apparatus. The substrate holder comprises a body having a body surface, a plurality of main burls protruding from the body surface, each main burl having a distal end face configured to support a substrate, a first seal member protruding from the body surface and having an upper surface, the first seal member surrounding the plurality of main burls and configured to inhibit a liquid between the substrate and the body surface from flowing radially inwardly past the first seal member, a second seal member protruding from the body surface, the second seal member surrounding the first seal member and configured to inhibit a liquid between the substrate and the body surface from flowing radially inwardly past the second seal member, a plurality of extraction openings formed in the body between the first seal member and the second seal member for extracting fluid from between the body and the substrate into the body, and a plurality of outer burls protruding from the body surface between the first seal member and the second seal member, each outer burl having a distal end face configured to support a substrate. The outer burls and extraction openings are alternately arranged in a line surrounding the first seal member and the main burls.

[0009]

[0009] In one embodiment of the present invention, there is provided a substrate holder for use in a lithographic apparatus, 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, each main burl having a distal end face configured to support a substrate, a first seal member protruding from the body surface and having an upper surface, the first seal member surrounding the plurality of main burls and configured to inhibit liquid between the substrate and the body surface from flowing radially inwardly past the first seal member, a plurality of minor burls protruding from the upper surface of the first seal member, each minor burr having a distal end face configured to support a substrate, and a second seal member protruding from the body surface, the first seal member surrounding the plurality of main burls and configured to inhibit liquid between the substrate and the body surface from flowing radially inwardly past the first seal member. a second seal member surrounding the seal member and configured to inhibit liquid between the substrate and the body surface from flowing radially inwardly past the second seal member, a third seal member protruding from the body surface, the third seal member surrounding the first seal member and the second seal member and configured to inhibit liquid between the substrate and the body surface from flowing radially inwardly past the third seal member, a plurality of inlet openings formed in the body between the first seal member and the second seal member, and a plurality of extraction openings formed in the body between the second seal member and the third seal member for extracting fluid from between the body and the substrate into the body. In one embodiment of the invention there is provided a substrate holder configured to support a substrate for use in a lithographic apparatus.The substrate holder comprises a body having a body surface, a plurality of main burls protruding from the body surface, each main burl having a distal end face configured to support a substrate, a sealing member protruding from the body surface and having an upper surface, the sealing member surrounding the plurality of main burls, 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 configured to inhibit liquid between the substrate and the body surface from flowing radially inward past the barrier. [Brief description of the drawings]

[0010]

[0010] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0011]

[0011] [Figure 1] 1 depicts a schematic diagram of a lithographic apparatus; [Figure 2a] 1 shows in cross section a version of a fluid handling structure that may extend around the circumference, with various features shown on the right and left. [Figure 2b] 1 shows in cross section a version of a fluid handling structure that may extend around the circumference, with various features shown on the right and left. [Diagram 3] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Figure 4] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Diagram 5] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Figure 6] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Figure 7] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Figure 8]2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Figure 9] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Figure 10] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Figure 11] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Figure 12] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. [Figure 13] 2 shows a schematic view of an edge of a substrate holder 200 according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In this document, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (eg, wavelengths of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm).

[0013]

[0012] The terms "reticle", "mask" or "patterning device" as used herein may be broadly interpreted to refer to a general purpose patterning device that can be used to impart a patterned cross-section to an incoming radiation beam, corresponding to the pattern to be created in a target portion of a substrate. The term "light valve" can also be used in this context. Besides the classical mask (transmissive or reflective mask, binary mask, phase-shifting mask, hybrid mask, etc.), examples of other such patterning devices include programmable mirror arrays and / or programmable LCD arrays.

[0014]

[0013] Figure 1 illustrates diagrammatically a lithographic apparatus comprising an illumination system (also referred to as illuminator) IL configured to condition a radiation beam B (e.g. UV 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 accurately position the patterning device MA according to certain parameters, a substrate support (e.g. wafer table) WT configured to hold a substrate (e.g. resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate support WT according to certain parameters, and a projection system (e.g. refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g. comprising one or more dies) of the substrate W.

[0015]

[0014] 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, such as refractive, reflective, magnetic, electromagnetic, electrostatic and / or other types of optical components, or any combination thereof, for directing, shaping or controlling the radiation. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross section in a plane of the patterning device MA.

[0016]

[0015] The term "projection system" PS as used herein should be interpreted broadly to encompass various types of projection systems including refractive optical systems, catadioptric optical systems, anamorphic optical systems, magnetic optical systems, electromagnetic optical systems, and / or electrostatic optical systems, or any combination thereof, as appropriate to the exposure radiation used and / or other factors such as the use of an immersion liquid or the use of a vacuum. When the term "projection lens" is used herein, this can be considered as synonymous with the more general term "projection system" PS.

[0017]

[0016] The lithographic apparatus may be of a type in which at least a part of the substrate may be covered with an immersion liquid having a relatively high refractive index, e.g. water, so as to fill a space 11 between the projection system PS and the substrate W. This is also called immersion lithography. More information about immersion techniques is given in US 6,952,253, which is incorporated herein by reference.

[0018]

[0017] The lithographic apparatus may also be of a type having two or more substrate supports WT (also known as "dual stage"). In such a "multi-stage" machine, the substrate supports WT may be used in parallel and / or a substrate W on one substrate support WT may be used for exposing a pattern thereon while a preparation step for a subsequent exposure of the substrate W is performed on a substrate W arranged on another substrate support WT.

[0019]

[0018] In addition to the substrate support WT, the lithographic apparatus may include a measurement stage. The measurement stage is arranged to hold a sensor and / or a cleaning device. The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam B. The cleaning device may be arranged to clean a part of the lithographic apparatus, such as for example a part of the projection system PS or a part of a system for providing immersion liquid. When the substrate support WT is remote from the projection system PS, the measurement stage may be moved below the projection system PS.

[0020] In operation, the radiation beam B is incident on the patterning device MA, e.g. a mask, which is held on the mask support MT and is patterned by a pattern (design layout) present on the patterning device MA. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. Using the second positioner PW and the position measurement system IF, the substrate support WT can be accurately moved, e.g. to position the various target portions C at focused and aligned positions in the path of the radiation beam B. Similarly, the patterning device MA can be accurately positioned with respect to the path of the radiation beam B using the first positioner PM and possibly further position sensors (not explicitly shown in FIG. 1). The patterning device MA and substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the illustrated substrate alignment marks P1, P2 occupy dedicated target portions, it is also possible that they may be located in spaces between the target portions. When the substrate alignment marks P1, P2 are located between target portions C, they are known as scribe-line alignment marks.

[0021]

[0020] To clarify the 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 referred to as the Rx rotation. Rotation about the y-axis is referred to as the Ry rotation. Rotation about the z-axis is referred to as the Rz rotation. The x-axis and the y-axis define a horizontal plane, and the z-axis defines a vertical direction. The Cartesian coordinate system does not limit the invention and is used merely for clarity. Alternatively, another coordinate system, such as a cylindrical coordinate system, can be used to clarify the invention. The orientation of the Cartesian coordinate system may be different, for example the z-axis has a component along the horizontal plane.

[0022]

[0021] To enable improved resolution of smaller features, immersion techniques have been introduced into lithography systems. In an immersion lithography apparatus, a layer of immersion liquid having a relatively high refractive index is disposed in a space 11 between the projection system of the apparatus (through which the patterned beam is projected towards the substrate W) and the substrate W. The immersion liquid covers at least the part of the substrate that is below the final element of the projection system PS. Thus, at least the part of the substrate W where exposure takes place is immersed in the immersion liquid. The effect of the immersion liquid is that the exposure radiation has a shorter wavelength in liquid than in gas, allowing smaller features to be imaged. (It can also be considered that the effect of the immersion liquid is to increase the effective numerical aperture (NA) of the system, and to increase the depth of focus.)

[0023]

[0022] In commercial immersion lithography, the immersion liquid is water. Typically, this water is highly pure distilled water, such as ultrapure water (UPW), which is commonly used in semiconductor manufacturing plants. In an immersion system, the UPW is often purified and may undergo additional processing steps before being supplied to the immersion space 11 as the immersion liquid. Besides water, other liquids with a high refractive index can be used as the immersion liquid. Examples include hydrocarbons, such as fluorocarbons, and / or aqueous solutions. Furthermore, other fluids other than liquids are also envisaged for use in immersion lithography.

[0024]

[0023] In the present description, reference is made to localized immersion, where in use the immersion liquid is confined to a space 11 between the final element and a surface facing the final element. The facing surface is either the surface of the substrate W or a surface of the support stage (or substrate support WT) that is flush with the surface of the substrate W. (Please note that in the following text, references to the surface of the substrate W may also or instead refer to the surface of the substrate support WT and vice versa, unless otherwise stated.) The immersion liquid is confined to the immersion space 11 by means of a fluid handling structure 12 that is between the projection system PS and the substrate support WT. The space 11 filled by the immersion liquid is smaller in plan than the top surface of the substrate W, and the space 11 is kept substantially stationary relative to the projection system PS while the substrate W and the substrate support WT are moving underneath.

[0025]

[0024] Other immersion systems are also envisaged, such as unconfined immersion systems (so-called "All Wet" immersion systems) and bath-based immersion systems. In an unconfined immersion system, the immersion liquid covers an area larger than the surface beneath the final element. The liquid outside the immersion space 11 is present as a thin film. The liquid covers either the entire surface of the substrate W or also covers the substrate W and a substrate support WT coplanar with the substrate W. In a bath-based system, the substrate W is completely immersed in a bath of immersion liquid.

[0026]

[0025] The fluid handling structure 12 is a structure which supplies immersion liquid to and removes immersion liquid from the immersion space 11, thereby confining the immersion liquid to the immersion space 11. It includes features which are part of a fluid supply system. The mechanism disclosed in PCT Patent Application Publication No. WO 99 / 49504 is an early fluid handling structure which includes pipes which supply or remove immersion liquid from the space 11 and which operate in response to relative movement of a stage below the projection system PS. More recent designs involve the fluid handling structure extending along at least part 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 partly define this space 11.

[0027]

[0026] The fluid handling structure 12 may have a variety of selected functions, each resulting from corresponding features that enable the fluid handling structure 12 to achieve that function. The fluid handling structure 12 may be referred to by a number of different terms, each describing a function, for example a barrier member, a seal member, a fluid supply system, a fluid removal system, liquid confinement structure, etc.

[0028] The fluid handling structure 12 as a barrier member 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 seal member the sealing feature of the fluid handling structure forms a seal that confines the immersion liquid to the space 11. The sealing feature may comprise an additional gas flow from an opening in the surface of the seal member, such as a gas knife.

[0029] In an embodiment, the fluid handling structure 12 supplies immersion fluid and may therefore be a fluid supply system.

[0030] In an embodiment, the fluid handling structure 12 at least partially confines the immersion fluid and so may be a fluid confinement system.

[0031] In an embodiment, the fluid handling structure 12 provides a barrier to the immersion fluid and so may be a barrier member, such as a fluid confinement structure.

[0032] In an embodiment, the fluid handling structure 12 may generate or use a gas flow, for example to facilitate controlling the flow and / or position of the immersion fluid.

[0033]

[0032] Because the flow of gas may form a seal to contain the immersion fluid, the fluid handling structure 12 may be referred to as a seal member. Such a seal member may be a fluid confinement structure.

[0034] In an embodiment, an immersion liquid is used as the immersion fluid. In that case, the fluid handling structure 12 may be a liquid handling system. With reference to the above description, references in this paragraph to features defined in terms of a fluid may be understood to include features defined in terms of a liquid.

[0035]

[0034] The lithographic apparatus comprises 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 by a fluid handling structure 12 between the projection system PS and the substrate W. The projection system PS comprises 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 a fluid handling structure 12. The fluid handling structure 12 may confine immersion liquid below the final element and above a facing surface.

[0036]

[0035] Figures 2a and 2b show various features that may be present in variations of the fluid handling structure 12. The designs may share some of the same features as Figures 2a and 2b unless stated otherwise. The features described herein may be selected individually or in combination as shown or as required.

[0037]

[0036] Figure 2a shows the fluid handling structure 12 around the bottom surface of the final element 100. The final element 100 has an inverted frusto-conical shape. The frusto-conical shape has a flat bottom surface and a conical surface. The frusto-conical shape protrudes from the plane and has a flat bottom surface. The flat bottom surface is the optically active part of the bottom surface of the final element 100 through which the radiation beam B can transmit. The final element 100 may have a coating 30. The fluid handling structure 12 surrounds at least a part of the frusto-conical shape. The fluid handling structure 12 has an inner surface facing the conical surface of the frusto-conical shape. The inner surface and the conical surface have complementary shapes. The top surface of the fluid handling structure 12 is substantially planar. The fluid handling structure 12 may fit around the frusto-conical shape of the final element 100. The bottom surface of the fluid handling structure 12 is substantially planar and, in use, may be parallel to a 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 30 to 500 micrometers, desirably in the range 80 to 200 micrometers.

[0038] 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 therefore defined between an inner surface of the fluid handling structure 12, the plane of the frustoconical portion and the facing surface. In 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, which in an embodiment is at least part of the space between the complementary inner surface and the conical surface.

[0039]

[0038] Immersion liquid is supplied to the space 11 via openings formed in a surface of the fluid handling structure 12. Immersion liquid may be supplied via supply openings 20 in an inner surface of the fluid handling structure 12. Alternatively or additionally, immersion liquid is supplied from a lower supply opening 23 formed in the lower surface of the fluid handling structure 12. The lower supply opening 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 below the projection system PS is laminar. Furthermore, the supply of immersion liquid from the lower opening 23 of the fluid handling structure 12 prevents the ingress of bubbles into the space 11. This supply of immersion liquid acts as a liquid seal.

[0040]

[0039] The immersion liquid can be recovered from a recovery opening 21 formed on the inner surface. Recovery of the immersion liquid via the recovery opening 21 can be performed by applying a negative pressure, as a result of the velocity of the immersion liquid flow through the space 11, or as a result of both. The recovery opening 21 can be located opposite the supply opening 20 in plan view. Additionally or alternatively, the immersion liquid may be recovered via an overflow opening 24 located on the top surface of the fluid handling structure 12. In an embodiment, the supply and recovery openings 20, 21 can be swapped in function (i.e. the liquid flow direction is reversed). This allows the flow direction to be changed depending on the relative movement of the fluid handling structure 12 and the substrate W.

[0041] Additionally or alternatively, immersion liquid may be collected from below the fluid handling structure 12 via collection openings 25 formed in the bottom surface of the fluid handling structure 12. The collection openings 25 may function 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 acts as a boundary between the liquid space and the gaseous external environment. The collection openings 25 may be a porous plate capable of collecting immersion liquid in a single phase flow. The bottom collection openings may be a series of fixed openings 32 through which immersion liquid is collected. The fixed openings 32 may collect immersion liquid in a two-phase flow.

[0042]

[0041] Optionally, there is a gas knife opening 26 radially outward relative to the inner surface of the fluid handling structure 12. Gas may be supplied at high velocity through the gas knife opening 26 to assist liquid confinement of the immersion liquid in the space 11. The supplied gas is humidified and may substantially comprise carbon dioxide. Radially outward of the gas knife opening 26 there is a gas recovery opening 28 for recovering the gas supplied through the gas knife opening 26. There may be further openings in the bottom surface of the fluid handling structure 12, for example open to atmosphere or a gas source. For example there may be further openings between the gas knife opening 26 and the gas recovery opening 28 and / or between the fixed opening 32 and the gas knife opening 26.

[0043]

[0042] Features shown in Figure 2b in common with Figure 2a use the same reference numerals. The fluid handling structure 12 has an inner surface complementary to the conical surface of the frustoconical shape. The underside of the fluid handling structure 12 is closer to the facing surface than the base plane of the frustoconical shape.

[0044] Immersion liquid is supplied to the space 11 via supply openings 34 formed in the inner surface of the fluid handling structure 12. The supply openings 34 are located near a lower portion of the inner surface, possibly below the base of the frusto-conical shape. The supply openings 34 are located on the inner surface at spaced intervals around the path of the radiation beam B.

[0045]

[0044] Immersion liquid is recovered from the space 11 via recovery openings 25 on the underside of the fluid handling structure 12. As the facing surface moves beneath the fluid handling structure 12, the meniscus 33 may move on the surface of the recovery openings 25 in the same direction as the movement of the facing surface. The recovery openings 25 may be formed of a porous member. The immersion liquid may be recovered in a single phase. In an embodiment, the immersion liquid is recovered in a two-phase flow. The two-phase flow is received in a chamber 35 in the fluid handling structure 12 where it is separated into liquid and gas. The liquid and gas are recovered from the chamber 35 via separate channels 36, 38.

[0046]

[0045] An inner periphery 39 of the underside of the fluid handling structure 12 extends into the space 11 away from the inner surface to form a plate 40. The inner periphery 39 forms a small aperture which can be sized to match the shape and size of the radiation beam B. The plate 40 can act to isolate immersion liquid on either side. The supplied immersion liquid flows inwards towards the aperture and, after passing through the inner aperture, flows radially outwards beneath the plate 40 towards the surrounding collection openings 25.

[0047] In an embodiment, the fluid handling structure 12 may be in two parts, an inner part 12a and an outer part 12b, as shown on the right hand side of Fig. 2b. The inner part 12a and the outer part 12b are relatively movable in a plane parallel to the facing surfaces. The inner part 12a has a supply opening 34 and may have an overflow collection part 24. The outer part 12b may have a plate 40 and a collection opening 25. The inner part 12a may have an intermediate collection part 42 for collecting immersion liquid flowing between the inner part 12a and the outer part 12b.

[0048] The substrate support WT includes a substrate holder 200 configured to support a substrate W. Figure 3 illustrates the substrate holder 200 and associated edge region of a substrate W (top) according to one embodiment in cross section at the top of the figure and in plan at the bottom of the figure. The substrate holder 200 includes a body 210 having a body surface 212. In use, the body surface 212 faces the underside of the substrate W.

[0049]

[0048] In a central region of the body surface 212 (left side in FIG. 3), a plurality of main burls 220 protrude from the body surface 212. Each main burl 220 has a distal end face configured to support a substrate W. The main burls 220 are arranged relative to one another in a pattern in a plan view. The pattern is such as to support the substrate W and reduce curvature of the substrate W toward the body surface 212 to an acceptable amount.

[0050]

[0049] The area in plan view of each main burl 220 is relatively small compared to the area in plan view of the substrate W. Thus, the main burl 220 contacts only a small area of ​​the underside of the substrate W. This reduces the possibility of contamination transferring from the substrate holder 200 to the substrate W.

[0051]

[0050] A pressure difference is generated on both sides of the substrate W. For example, the space between the body 210 of the substrate holder 200 and the substrate W is connected to a negative pressure that is lower than the high pressure on the upper side of the substrate W. This pressure difference generates a force that holds the substrate W to the substrate holder 200.

[0052]

[0051] In an immersion lithography apparatus, at least at some time during the exposure of the substrate W, liquid is present adjacent to the edge of the substrate W. Due to negative pressure between the body 210 of the substrate holder 200 and the underside of the substrate W, this liquid is drawn under the substrate W around the edge of the substrate W. To reduce the occurrence of liquid contacting the underside of the substrate W, particularly in the area where the main burls 220 are in contact with the substrate W, a first seal member 230 is provided that protrudes from the body surface 212 of the body 210. The first seal member 230 surrounds the plurality of main burls 212. The first seal member 230 is configured to inhibit liquid between the substrate W and the body surface 212 from flowing radially inwards past the first seal member 230. The first seal member 230 is a continuous barrier (not necessarily uniform in cross section) surrounding the main burls 220.

[0053]

[0052] One purpose of the first seal member 230 is to limit the radially inward gas flow (which may be unnecessarily humid) towards the main burl 220. This allows the necessary negative pressure to be generated around the main burl 220 to clamp the substrate W to the substrate holder 200. It is advantageous to allow some gas flow over the first seal member 230 to allow a quick removal of the substrate W from the substrate holder 200 when the negative pressure source generating the negative pressure around the main burl 220 is switched off. If the gas flow through the first seal member 230 is too small, it takes too long for the pressure around the main burl 220 to equalize with the pressure above the substrate W, releasing it.

[0054]

[0053] The first seal member 230 has an upper surface 232 that is configured to form a gap with the underside of the substrate W during use. That is, the upper surface 232 is configured to be slightly closer to the body surface 212 than the distal end surface of the main burl 220. This arrangement is advantageous because it allows gas to be drawn onto the first seal member 230 (below the substrate W) just prior to removal of the substrate W, while inhibiting the passage of liquid in the same direction. This is achieved without contacting a large area of ​​the underside of the substrate W. Such contact would be detrimental as it would cause contamination to be transferred from the first seal member 230 to the substrate W. Also, such contact would cause more problems in removing the substrate W from the substrate holder 200.

[0055]

[0054] The cross-sectional area, in plan, of the first seal member 230 is much larger than that of the main burl 220. The relatively large cross-sectional area, in plan, of the first seal member 230 provides greater resistance to radially inward movement of liquid between the substrate W and the body surface 212 through the first seal member 230.

[0056]

[0055] As seen in Fig. 3, the radially outermost main burl 220 of the plurality of main burls 220 is at a considerable distance away from the edge of the substrate W. Since there are no other features supporting the substrate W radially outward from the radially outermost main burl 220, downward bending of the edge of the substrate W may occur. This is due to the negative pressure of the underside of the substrate W relative to the upper side of the substrate W. In the present invention, a plurality of minor burls 240 are provided to support the substrate W radially outward from the radially outermost main burl 220. The minor burls 240 protrude from the upper surface 232 of the first seal member 230. Each minor burl 240 has a distal end surface configured to support the substrate W.

[0057]

[0056] The minor burls 240 are disposed circumferentially along the first seal member 230. The minor burls 240 may be spaced apart from one another. The minor burls 240 may all be at the same radial distance from the center of the substrate holder 200 or at different radial distances. The cross-sectional area of ​​each minor burl 240 in plan view is much smaller than that of the first seal member 220. For example, the sum of the cross-sectional areas of the minor burls 240 on the first seal member 230 is much smaller than the total cross-sectional area of ​​the first seal member 230, for example at least one tenth or one fifteenth.

[0058]

[0057] There are a number of extraction openings 250 radially outward of the first seal member 230. The extraction openings 250 are formed in the body 210. The extraction openings 250 are connected to a negative pressure source. Thus, any liquid that reaches the extraction openings 250 is extracted through the body 210. This means that the liquid is prevented from penetrating further into the space between the body surface 212 and the substrate W. The extraction openings 250 can also extract gas, for example when there is no liquid to be extracted. It is also possible to extract a mixture of liquid and gas through the extraction openings 250.

[0059]

[0058] The extraction openings 250 are spaced apart from one another around the entire circumference of the first seal member 230. Although the extraction openings 250 are illustrated in Figure 3 as discrete openings in the body surface 212, this may not be the case. For example, a groove could be formed in the body surface 212, with the extraction openings 250 emerging from the body 210 at the bottom of the groove. The groove could be segmented, with one or more openings in each segment. The segments could be considered as multiple recesses.

[0060]

[0059] By connecting the extraction openings 250 to a negative pressure, liquid advancing to the edge of the substrate W can be removed via the extraction openings 250. Once the edge of the substrate W is no longer covered with liquid, the underside of the substrate W is dry since the liquid has been removed.

[0061]

[0060] Radially outward of the extraction opening 250 is a second seal member 260. The second seal member 260 surrounds the extraction opening 250. The second seal member 260 also surrounds the first seal member 230.

[0062] The second seal member 260 may be similar to the first seal member 230 and has a plurality of minor burls 270 protruding from an upper surface 262. An advantage of providing a plurality of minor burls 270 on the upper surface 262 of the second seal member 260 is that the substrate W is supported near its edges. This further reduces deformation of the substrate W due to unsupported edges.

[0063] 3 illustrates minor burls 240, 270 on both the first seal member 230 and the second seal member 260, this may not be the case. For example, minor burls 240 may only protrude from the top surface 232 of the first seal member 230, or minor burls 270 may only protrude from the top surface 262 of the second seal member 260. In both cases, deformation of the substrate W is reduced compared to when the minor burls 240, 270 are not present.

[0064] 3 shows both the first and second seal members 230, 260, it is possible that only the first seal member 230 or only the second seal member 260 is present. If only the second seal member 260 is present, this configuration can be considered to have a first seal member with a plurality of extraction openings 250 radially inwardly therefrom. In such a configuration, if the first seal member 230 is present radially inwardly of the extraction openings 250, it can be considered to be a second seal member.

[0065] In the embodiment of Fig. 3, in use, a negative pressure is applied to the central region of the substrate holder 200 between the body surface 212 and the substrate W. Due to this negative pressure, the substrate W is clamped to the substrate holder 200. This clamping negative pressure can be less (i.e. a small vacuum) than the negative pressure in the region adjacent to the extraction opening 250. This configuration results in a gas flow radially outward from a position around the main burl 220 toward the extraction opening 250, and a fluid flow radially inward from the edge of the substrate W toward the extraction opening 250. In this way, the gas flow flows radially outward to a position adjacent to the extraction opening 250, thereby inhibiting liquid and humidified gas from moving further radially inward beyond the position of the extraction opening 250. This reduces the degree of liquid penetration beneath the substrate W. As there is no liquid or no first seal member 230 above, removal of the substrate W from the substrate holder 200 is more easily achieved, resulting in reduced wear. Wear is detrimental as it causes contamination of the substrate W and deforms the substrate W by changing the clamping properties of the substrate holder 200. The presence of liquid between the main burl 220 and the underside of the substrate W can also cause wear (if the substrate holder 200 is ceramic) and possibly frictional variations. As with contamination, deformation of the substrate W can lead to imaging errors (e.g. overlay errors and / or focus errors). The presence of liquid on the underside of the substrate W is generally detrimental as it can cause problems with the thermal stability of the substrate W and problems if droplets are lost during unloading of the substrate W. The substrate holder 200 of FIG. 3 therefore mitigates some of these problems by having additional support for the substrate edge in place, as well as measures to keep the first seal member 230 dry and measures to prevent liquid from entering radially inwards through the extraction openings 250. Furthermore, by preventing liquid from entering through the extraction openings 250, a humid atmosphere between the body surface 212 and the substrate W is avoided. The disadvantage of a humid atmosphere is that it can oxidize the main bar 220 .Oxidation of the main burls 220 is detrimental as it reduces the flatness that can be achieved for the substrate W supported by the main burls 220 .

[0066]

[0065] Figure 4 shows another embodiment of a substrate holder 200 according to the present invention. The figure shows the edge region of the substrate holder 200 in cross section at the top of the figure and in plan view at the bottom of the figure. The embodiment of Figure 4 is identical to Figure 3 except as described below. Similar reference numbers are used to indicate corresponding features.

[0067] In the embodiment of FIG. 4, the body surface 212 is formed with a number of inlet openings 280. 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. This results in a radially outward gas flow from the inlet openings 280 towards the extraction openings 250. This gas flow forms a barrier against liquid and humidified gases entering radially inward under the substrate W. A radially inward gas flow is also generated from the inlet openings 280 due to the negative pressure generated at the center of the substrate holder 200 to clamp the substrate W to the substrate holder 200. The negative pressure generated at the center of the substrate holder 200 in the region of the main burl 220 can be as large as the negative pressure generated above the extraction openings 250. It is also possible to make the negative pressure at the extraction openings 250 deeper (i.e. larger) than the negative pressure at the main burl 220, generating a flow radially outward over the top surface 232.

[0068]

[0067] Depending on the depth of the groove between the first seal member 230 and the second seal member 260, the main burls 220 (and / or minor burls 270) can be positioned alternately with the inlet opening 280 or the extraction opening 250, or between the inlet opening 280 and the extraction opening 250.

[0069]

[0068] The plurality of inlet openings 280 may be formed in the bottom of a groove in the body surface 212. The groove may be in the form of a continuous or discontinuous circumferential channel. Alternatively, the plurality of inlet openings 280 may be formed as a plurality of discrete openings in the body surface 212, as shown. The number, size, and spacing of the inlet openings 280 may be selected as appropriate. The number, size, and spacing of the inlet openings 280 may be similar to the extraction openings 250, as shown.

[0070]

[0069] The gas exiting the inlet opening 280 can be dehumidified gas, which further reduces the humidity of the gas present around the main burl 220. Alternatively, it is also possible to provide humidified gas from the inlet opening 280, if the gas exiting the inlet opening 280 is drawn towards the extraction opening 250. This reduces the evaporation of liquid in the resulting gas flow, thus reducing the evaporative heat load on the underside of the substrate W and / or in the extraction opening 250 and further downstream. Also, the provision of the inlet opening 280 allows the negative pressure connected to the extraction opening 250 to be the same as the negative pressure around the main burl 220. This is advantageous, as the negative pressure does not need to be lower than the negative pressure around the main burl 220, and draws more liquid from the edge of the substrate W below the substrate W, similar to the embodiment of FIG. 3.

[0071] In one embodiment, the gas flow radially inward toward the extraction opening 250 produces a balanced surface liquid flow and a surface gas flow. This means that the liquid flows outside the through-hole forming the extraction opening 250, and the gas flows inside the through-hole. When liquid is present, this type of two-phase flow occurs and a smooth flow can be achieved. Desirably, when no liquid is present, the negative pressure determined by the inlet opening 280 and the flow restriction of the second seal member 260 must be greater than the maximum capillary negative pressure of the second seal 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 seal member 260 should always be sufficient to remove the liquid present between the upper surface 262 of the second seal member 260 and the substrate W. This is desirable as it allows the substrate W to be removed without having to overcome the attraction to the substrate holder 200 due to liquid present between the second seal member 260 and the substrate W. As discussed above, no liquid is present between the first seal member 230 and the substrate W. Additionally, the absence of liquid between the first and second seal members 230, 260 and the substrate W increases the flatness of the substrate W.

[0072] FIG. 5 shows another embodiment which is identical to the embodiment of FIG. 4 except as described below.

[0073] 5, the second seal member 260 has a wider radial width than the first seal member 230. The second seal member 260 has an extraction opening 250 formed in its upper surface 262. As shown, the second seal member 260 has a groove 252 formed in its upper surface 262 with the extraction opening 250 formed at its bottom.

[0074] 5, two minor burls 270 are formed on the upper surface 262 of the second seal member 260 on either side of the extraction opening 250. Such minor burls 270 may or may not be present, and may be present only radially inward or only radially outward of the extraction opening 250. The radially inner and outer minor burls 270 on the second seal member 260 may be radially aligned as shown, or may be radially alternating with one another.

[0075] 5 can be considered to have three seal members: a first seal member 230, a seal member radially inward of the extraction opening 250, and a third seal member radially outward of the extraction opening 250. This becomes even more evident when the groove 252 is deep such that its bottom surface is substantially flush with the body surface 212 of the body 210. In this respect, the central seal member can be considered to be positioned between the inlet opening 280 and the extraction opening 250, and further between the first seal member 230 and the second seal member 260.

[0076]

[0075] The main burls 220 (and / or the minor burls 270) may be arranged alternately with the inlet openings 280 or the extraction openings 250.

[0077] 5 embodiment is that the gas flow radially outward from the inlet openings 280 to the extraction openings 250 passes over the constriction between the top surface 262 of the radially inner part of the second seal member 260 and the substrate W. This results in an acceleration of the gas flow, which improves the sealing function, because if the force generated by the gas flow is greater than the capillary force of the liquid between the top surface 232 and the substrate W, any liquid proceeding radially inward of the extraction openings 250 will be pushed radially outward by the accelerating gas flow back towards the extraction openings 250.

[0078]

[0077] In the embodiment of Figure 5, instead of or in addition to the extraction openings 250 positioned in the second seal member 260, multiple inlet openings 280 can be positioned in the first seal member 230. This configuration has similar advantages to the configuration shown in Figure 5. As the gas flow radially outward from the inlet openings 280 towards the extraction openings 250 has to pass through a narrow gap between the first seal member 230 and the substrate W, the gas flow accelerates, thereby improving the sealing function of the configuration.

[0079] In an alternative embodiment, the groove 252 may be replaced by a plurality of recesses similar to the recess 284 described below with reference to FIG. 6, and an inlet opening 280.

[0080] The embodiment of FIG. 6 is identical to the embodiment of FIG. 5 except as described below.

[0081] In the embodiment of Figure 6, the configuration of the extraction opening 250 at the bottom of the groove 252 formed in the upper surface 262 of the second seal member 260 is the same as in the embodiment of Figure 5. However, rather than providing the inlet opening 280 at the bottom of a deep recess between the first seal member 230 and the second seal member 260, the inlet opening 280 in the embodiment of Figure 6 is provided at the bottom of a separate recess 284 formed in the upper surface 232 of the first seal member 230. This embodiment can be thought of as having a first seal member 230 with an inlet opening 280 formed therein, a second seal member 260 with no inlet or opening formed therein, and a shallow groove 252 with an extraction opening 250 formed at the bottom of the groove 252 between the first seal member 230 and the second seal member 260.

[0082]

[0081] The recesses 284 are pressure dividers and more clearly define the gas flow at a predetermined location. Furthermore, the recesses 284 create a tangential flow between the inlet openings 280. This tangential flow can remove liquid from between the inlet openings 280. This effect is also achieved by the grooves 252.

[0083]

[0082] Although the illustrated configuration shows each recess 284 having a corresponding inlet opening 280, the configuration may differ and a single recess 284 may have two or more associated inlet openings 280.

[0084]

[0083] In this, and all other embodiments, the minor burls 240 may be interleaved with the entrance openings 280, similar to how the outer burls 300 are interleaved with the extraction openings 250 in the embodiment of Fig. 9 described below. Additionally or alternatively, the minor burls 240 may be positioned radially inward and / or outward of the entrance openings 280, and even in line at the same radial distance from the centre of the substrate holder 200 as the entrance openings 280.

[0085]

[0084] The embodiment of Figure 7 is identical to the embodiment of Figure 5 or Figure 6 except as described below.

[0086]

[0085] In Fig. 7, a groove 290 is formed in the upper surface 232 of the first seal member 230. The bottom surface of the groove 290 has no opening.

[0087] 7, the groove 290 may have a shape that forms a labyrinth seal for the first gas passage from the radially outer side of the first seal member 230 to the radially inner side of the first seal member 230. That is, the groove 290 extends from the radially inner side of the first seal member 230 to the radially outer side of the first seal member 230 following a tortuous path. As in all other embodiments, the main burls 220 and / or the minor burls 240, 270 may be arranged alternately with (and / or radially inward / outward of) the inlet openings 280 and / or the extraction openings 250.

[0088] FIG. 8 shows an embodiment that is identical to that of FIG. 5 except as described below.

[0089]

[0088] In the embodiment of Fig. 8, rather than the extraction opening 250 being formed in the upper surface 262 of the second seal member 260 and the inlet opening 280 being formed between the first seal member 230 and the second seal member 260, the extraction opening 250 is formed between the first seal member 230 and the second seal member 260, and the inlet opening 280 is formed in the upper surface 232 of the first seal member 230. As with the embodiment of Fig. 5, this can be considered a three-seal member embodiment. As shown and described with reference to Fig. 5 about the periphery of the extraction opening 250, the upper surface 232 of the first seal member 230 may or may not be provided with a continuous groove or separate depressions, and the inlet opening 280 may be formed at the bottom of the groove or separate depression. The upper surface 232 of the first seal member 230 may be provided with minor burrs 240 radially inward and / or outward from the extraction opening 280 (or alternately). Like the minor burls 270 on the second seal member 260 of the embodiment of FIG. 5, the minor burls 240 may or may not be radially aligned.

[0090] FIG. 9 shows an embodiment that is identical to that of FIG. 8 except as described below.

[0091] 9, the top surface 232 of the first seal member 230 is provided with a meniscus pinning feature 290. The meniscus pinning feature 290 extends around the area of ​​the main burl 220. The meniscus pinning feature 290 is radially outward of the inlet opening 280. The meniscus pinning feature 290 is radially inward of the extraction opening 250.

[0092]

[0091] The meniscus pinning feature 290 has features that are effective to pin the meniscus of the liquid in place, such as a sharp edge 292. The meniscus pinning feature 290 exerts a force on the meniscus, which means that additional energy is required for the meniscus to move past the meniscus pinning feature 290. Thus, there is yet another barrier to radially inward movement of the liquid.

[0093] 8, the minor burrs 240 may be located anywhere on the upper surface 232 of the first seal member 230. Additionally or alternatively, minor burrs 270 may be present on the upper surface 262 of the second seal member 260.

[0094] 9, the extraction openings 250 are held at a negative pressure greater than the negative pressure applied in the region of the main burr 220. In an embodiment, a negative pressure is also applied to the inlet openings 280. The negative pressure applied to the inlet openings 280 has a magnitude between the negative pressure applied in the region of the main burr 220 and the negative pressure applied to the extraction openings 250. This creates a radially outward gas flow past the inlet openings 280. This radially outward gas flow represents another force on the liquid meniscus between the substrate W and the substrate holder 200.

[0095]

[0094] Although the meniscus pinning feature 290 is illustrated as a groove with sharp edges 292, any feature may be used that functions as the meniscus pinning feature 290. An alternative feature may be a change in the contact angle between the top surface 262 and the immersion liquid at the location of the meniscus pinning feature 290.

[0096]

[0095] A meniscus pinning feature 290 such as the one shown in Figure 9 may be used in any of the other embodiments. The location of the meniscus pinning feature 290 is best positioned radially inward of the extraction opening 250.

[0097] The embodiment of FIG. 10 is identical to the embodiment of FIG. 3 except as described below.

[0098]

[0097] In the embodiment of Fig. 10, the minor burls 240, 270 are optional features. Alternatively or additionally, a plurality of outer burls 300 are provided radially outward of the first seal member 230 to support the edge of the substrate W radially outward from the outermost main burls 220. The plurality of outer burls 300 protrude from the body surface 212. Each of the plurality of outer burls 300 has a distal end face configured to support the substrate W. As shown, the plurality of outer burls 230 can be provided radially inward of the second seal 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 seal member 230 and the main burls 220.

[0099]

[0098] In this way, the edge of the substrate W has support. This can reduce deformation of the substrate W at the outer edge. In one embodiment, the outer burls 300 can be positioned radially outward of the second seal member 260. The outer burls 300, such as the one shown in Figure 10, may be optionally provided in the embodiments described with reference to Figures 3 to 9 and 11 to 13.

[0100] FIG. 11 shows an embodiment that is identical to that of FIG. 10 except as described below.

[0101] [000100] The variations in the geometry of the first seal member 230 and / or the second seal member 260 shown in FIG. 11 and described below may be applied to the first seal member 230 and / or the second seal member 260 of any of the embodiments.

[0102] [000101] In the embodiment of FIG. 11, as seen at the bottom of this figure, the second seal member 260 extends in a serpentine path around the circumference of the substrate holder 200. Also shown in FIG. 11 are minor burls 240 formed on the top surface 232 of the first seal member 230. The minor burls 240 are positioned, for example, at vertices where adjacent concave curved portions 320 meet. Thus, a plurality of minor burls 240 protrude from portions of the first seal member 230 that extend farther from the center of the substrate holder 200 than other portions of the first seal member 230. The first seal member 230 and the second seal member 260 can have any shape. What is desired is that the minor burls 240 positioned on the first seal member 230 are positioned on a circumferential line such that the groove between the first seal member 230 and the second seal member 260 has equal areas radially inward and radially outward. Therefore, since the negative pressure generated between the first seal member 230 and the second seal member 260 is equal on both sides of the line of the minor crowbar 240, no large bending moment due to the large negative pressure occurs in the area between the first seal member 230 and the second seal member 260.

[0103] [000102] In one embodiment, the first seal member 230 is formed by joining a plurality of concave curved portions 320. In one embodiment, the second seal member 260 has an overall shape defined by a plurality of curved portions 310 having a smaller radius than the overall shape in a plan view, and the overall shape is formed by joining the plurality of curved portions 310. The second seal member 260 is formed by a plurality of convex curved portions 310 (with respect to a radial direction from the radial inner side to the radial outer side of the substrate holder 200).

[0104] It is also possible to provide an inlet opening 280 radially inward of the extraction opening 250 , for example between the first seal member 230 and the second seal member 260 .

[0105] [000104] The embodiment of FIG. 12 incorporates features of the embodiment of FIG. 6 and the embodiment of FIG.

[0106] [000105] The embodiment of Figure 12 has a single seal member 230. The single seal member 230 is shown in plan in the center of Figure 12 and in cross section on the left and right sides of Figure 12. The left side of Figure 12 is a cross section through line AA shown in the plan view of Figure 12. The right side of Figure 12 shows a cross section through line BB in the plan view of Figure 12.

[0107] [000106] The seal member 230 includes a plurality of inlet openings 280 in the upper surface 232. Also formed in the upper surface 232 of the seal member 230 are extraction openings 250. The inlet openings 280 may be connected to an ambient pressure source or to a negative pressure that is less than the negative pressure to which the extraction openings 250 are connected.

[0108] 12, one or more first recesses 510 are formed in the upper surface 232 of the seal member 230. Each of the first recesses 510 has at least one extraction opening 250 associated with it. However, there may be more than one extraction opening 250 in or each of the first recesses 510.

[0109] [000108] One or more second recesses 520 are formed in the upper surface 232 of the seal 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 or each of the second recesses 520.

[0110] [000109] The first and second recesses 510, 520 are shaped and positioned such that a barrier 550 is formed between the first recess 510 and the second recess 520. The barrier 550 is configured to inhibit liquid between the substrate W and the body surface 212 from passing radially inwardly past the barrier 550.

[0111] [000110] Due to the relatively high gas pressure at the inlet opening 280, gas is drawn from the inlet opening 280 over the barrier 550 towards the extraction openings 250. This gas flow is accelerated as it passes through the barrier 550, which forms an effective gas seal between the barrier 550 and the underside of the substrate W. Advantageously, the gas flow has a tangential component from the inlet opening 280 towards the extraction openings 250 so as to direct the radially incoming fluid towards the extraction openings 250.

[0112] [000111] The relative positioning of the plurality of extraction openings 250 and the inlet opening 280, and the size and shape of the barrier 550, creates a fluid flow as shown by the arrows in the plan view of Figure 12. That is, negative pressure applied to the extraction openings 250 draws fluid from the radially outside of the seal member 230 into the extraction openings 250 and is focused towards the extraction openings 250 by tangential movement.

[0113] [000112] 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 are effective to define sidewalls of the first recess 510 and the second recess 520, respectively. The first extension 560 extends from the barrier 550 to a radially outer portion of the seal member 230. The second extension 570 extends from the barrier 550 to a radially inner portion of the seal member 230.

[0114] [000113] The inlet openings 280 and extraction openings 250 are circumferentially alternating such that gas drawn through the inlet openings 280 flows towards the extraction openings 250 on either side of the inlet opening 280. In this manner, tangential gas flow is achieved substantially around the entire circumference of the seal member 230, resulting in excellent sealing properties.

[0115] [000114] Since each extraction opening 250 is formed in the first recess 510 and further, the extraction openings 250 are in close proximity to one another along the circumference of the seal member 230, the force exerted on the substrate W by the negative pressure applied to the extraction openings 250 is uniform in the circumferential direction, resulting in reduced deformation of the substrate W.

[0116] [000115] Because the inlet openings 280 are positioned at the bottom of the corresponding second recesses 520, the area of ​​the barrier 550 over which gas flow from the inlet openings 280 spreads is greater than if the inlet openings 280 were not formed in the second recesses 520.

[0117] [000116] Optionally, the inlet openings 280 are spaced radially outwardly from the extraction openings 250. This facilitates splitting 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 further explained below.

[0118] [000117] The one or more first recesses 510 extend radially inward such that an innermost portion of the first recess 510 is closer to a center of the substrate holder 200 than an outermost portion of the one or more second recesses 520 such that the extraction opening 250 can be positioned radially inward from the entrance opening 280. The shapes of the first recess 510 and the second recess 520 include a tangential narrowing towards the center of the substrate W in the case of the first recess 510 and away from the center of the substrate W in the case of the second recess 520.

[0119] [000118] The barrier 550 can be considered to form a sidewall of the first recess 510 on one side (radially outer) and a sidewall of the second recess 520 on the other side (radially inner). The sidewalls are formed by a set of first and second portions 552 and 554 of the barrier 550.

[0120] [000119] As the first and second portions 552, 554 in a set extend in a radially inward direction, they converge to a respective first apex 556. By positioning one of the extraction openings 250 adjacent the first apex 556, a radially inward fluid flow is guided by the first and second portions 552, 554 and by the gas flow from the inlet opening 280 towards the extraction opening 250. This guidance of the fluid flow towards the extraction opening 250 results in an increased extraction efficiency of the extraction opening 250. Additionally, the first extension 510 forms a tangential barrier to the fluid flow, which also promotes gas flow.

[0121] [000120] Additionally, adjacent sets of first portions 552 and second portions 554 extend in a radially outward direction so as to converge to respective second vertices 558 of the barrier 550. Advantageously, each of the second vertices 558 has an inlet opening 280 associated therewith.

[0122] [000121] A first extension 560 extends from the second apex 558. A second extension 570 extends from the first apex 556.

[0123] [000122] The guidance of fluid flow towards the extraction openings 250 is also aided by the overall shape of the seal member 230 in plan view. That is, the radially outermost portions of the seal member 230 are at different distances from the center of the substrate holder 200. This results in the wave pattern shown in the plan view of FIG. 12. The extraction openings 250 are positioned in circumferential alignment with the portions of the seal member 230 that extend further from the center of the substrate holder 200 than the other portions of the seal member 230. That is, an imaginary line (such as line AA) passing through the center of the substrate holder 200 passes through the extraction openings 250 and through the radially outermost portions of the seal member 230. Optionally, a similar configuration is made on the inner surface of the seal member 230 as shown, with the inlet openings 280 being radially aligned with the portions of the seal member 230 that extend closer to the center of the substrate holder 200 than the other portions of the seal member 230.

[0124] 12 embodiment may include a plurality of minor burls 240 as discussed in connection with other embodiments of the invention. The minor burls 240 may be positioned radially inward and / or outward from the extraction openings 250 and / or the inlet openings 280, or may be positioned substantially in-line with the inlet openings 280 and / or the extraction openings 250.

[0125] [000124] The embodiment of Figure 13 is the same as that of Figure 12 except that only a single first recess 510 is formed, i.e. there is no first extension 560. Alternatively or additionally, there may be no second extension 570.

[0126] [000125] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it will be appreciated that the lithographic apparatus described herein may have other applications, including 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, etc.

[0127] [000126] Although particular reference has been made herein to embodiments of the invention in the context of lithographic apparatus, embodiments of the invention may also be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatus may be generally referred to as lithography tools. Such lithography tools may use vacuum or ambient (non-vacuum) conditions.

[0128] [000127] Although specific reference has been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that, where the context permits, the invention is not limited to optical lithography and may be used in other applications, such as, for example, imprint lithography.

[0129] [000128] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The above description is intended to be illustrative and not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

1. 1. A substrate holder for use in a lithographic apparatus, configured to support a substrate, comprising: a body having a body surface; a plurality of main burls protruding from the body surface, each main burr having a distal end surface configured to support the substrate; a first seal member protruding from the body surface and having an upper surface, the first seal member surrounding the plurality of main burls and configured to inhibit liquid between the substrate and the body surface from flowing radially inward past the first seal member; a plurality of minor burrs protruding from the top surface of the first seal member, each minor burr having a distal end surface configured to support the substrate; A substrate holder comprising:

2. The substrate holder of claim 1 , further comprising a plurality of extraction openings formed in the body for extracting fluid into the body from between the body and the substrate.

3. 3. The substrate holder of claim 2, wherein the plurality of extraction openings are arranged radially outward of the first seal member, and / or the substrate holder further comprises a second seal member protruding from the body surface, the second seal member having an upper surface, surrounding the plurality of main burls, and configured to suppress liquid between the substrate and the body surface from flowing radially inward past the second seal member.

4. 4. The substrate holder of claim 3, wherein the second seal member surrounds the first seal member, preferably the substrate holder further comprising a plurality of second minor burls protruding from the top surface of the second seal member, each second minor burr having a distal end face configured to support the substrate, and preferably the plurality of extraction openings are in the top surface of the second seal member.

5. 5. The substrate holder of claim 4, wherein each extraction opening is formed in a bottom surface of an extraction groove formed in the second seal member, or each extraction opening is formed in a bottom surface of a corresponding recess formed in the top surface of the second seal member.

6. The substrate holder of claim 2 , wherein the plurality of extraction openings are disposed radially inward of the first seal member.

7. 7. The substrate holder of claim 2, further comprising a second seal member protruding from the body surface, the second seal member surrounding the plurality of main burls and configured to inhibit liquid between the substrate and the body surface from flowing radially inward past the second seal member.

8. 8. The substrate holder of claim 7, wherein the first seal member surrounds the second seal member and / or the second seal member has a top surface, and the substrate holder further comprises a plurality of second minor burls protruding from the top surface of the second seal member, each second minor burr having a distal end surface configured to support the substrate.

9. A substrate holder according to claim 4 and any of claims 6 to 8, wherein the plurality of extraction openings are in the body surface between the first seal member and the second seal member.

10. 10. A substrate holder as claimed in any one of claims 2 to 9, further comprising a plurality of outer burls protruding from the body surface, each outer burl having a distal end face configured to support the substrate, the outer burls being radially outward of the first seal member, and preferably the outer burls and the extraction openings being alternately arranged in a line surrounding the first seal member and the plurality of main burls.

11. 11. A substrate holder as described in any one of claims 2 to 10, further comprising a plurality of inlet openings formed in the body for drawing gas into the space between the substrate and the body, preferably the substrate holder further comprising a plurality of inlet openings formed in the body for drawing gas into the space between the substrate and the body.

12. 12. The substrate holder of claim 11, wherein the multiple inlet openings are formed in the body surface radially outward of the first seal member, or the multiple inlet openings are in the upper surface of the first seal member, preferably the multiple inlet openings are provided at the bottoms of respective recesses formed in the upper surface of the first seal member.

13. 13. The substrate holder of claim 1, further comprising a groove formed in the top surface of the first seal member, the groove providing a tortuous path for gas from a radially outer side of the first seal member to a radially inner side of the first seal member, and / or the first seal member having an overall shape in a plan view such that a radially outermost portion of the first seal member has a distance from a center of the substrate holder that varies in a circumferential direction, and the plurality of minor burrs protruding from a portion of the first seal member that extends farther from a center of the substrate holder than other portions of the first seal member.

14. A substrate holder according to any preceding claim, further comprising a meniscus pinning feature on the top surface of the first seal member.

15. A lithographic apparatus comprising a substrate holder according to any one of the preceding claims.

Images