PCB support

Abstract

Disclosed herein is a substrate support (200) configured to support a substrate (W), the substrate support comprising: a top surface (255); a plurality of support members (241) extending above the top surface; an extraction trough (230) defined by a first circumferential wall and a second circumferential wall, the first and second circumferential walls extending above the top surface; an extraction opening (217) formed on the top surface within the extraction trough; and one or more fluid-retaining features (250) formed within the extraction trough.

Description

Technical Field

[0001] (Cross - reference to related applications)

[0001] This application claims the priority of European Application No. 23180090.5 filed on June 19, 2023, European Application No. 23204104.6 filed on October 17, 2023, and European Application No. 24159835.8 filed on February 27, 2024, and these applications are hereby incorporated by reference in their entirety into this specification.

[0002]

[0002] The present invention relates to a substrate support, a lithographic apparatus comprising the substrate support, a method of manufacturing the substrate support, and a method of manufacturing a device comprising supporting a substrate on the substrate support.

Background Art

[0003]

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. The lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). The lithographic apparatus can project, for example using a projection system, a pattern (often also 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). Known lithographic apparatuses include so - called steppers, where each target portion is irradiated by exposing the entire pattern once onto the target portion, and so - called scanners, where each target portion is irradiated by scanning the pattern in a given direction (the "scan" direction) with a radiation beam while synchronously scanning the substrate parallel or antiparallel to this direction.

[0004]

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continuously decreased, while the number of functional elements such as transistors per device has steadily increased over decades, following a trend commonly known as Moore's Law. To keep up with Moore's Law, the semiconductor industry is pursuing technologies that enable the creation of increasingly smaller features. To project patterns onto a substrate, lithography equipment can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the feature 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.

[0005]

[0005] Further improvement in the resolution of smaller features can be achieved by providing an immersion liquid with a relatively high refractive index, such as water, on the substrate during exposure. Since exposure radiation has shorter wavelengths in a fluid than in a gas, the effect of the immersion liquid is that it enables imaging of smaller features. The effect of the immersion liquid can also be seen as increasing the effective numerical aperture (NA) and depth of field of the system.

[0006]

[0006] The immersion liquid can be confined to a local area between the projection system of the lithography apparatus and the substrate by a fluid handling structure. [Overview of the project]

[0007]

[0007] As the gap between the substrate and the surrounding covering passes under the fluid handling structure, immersion fluid can enter the extraction trough between the substrate and the substrate support. When immersion fluid is present on the surface of the extraction trough, a thermal load, i.e., a cold load, can be applied to the surface of the extraction trough. After a period of time, the immersion fluid may completely evaporate. Once the immersion fluid has completely evaporated, no thermal load is applied to the surface of the extraction trough. This can lead to transient structural deformation, which can increase overlay error, specifically the wafer load grid (WLG).

[0008]

[0008] The present invention aims to provide a configuration in which the immersion liquid is held within the extraction trough. As a result, a consistent thermal load can be applied to the surface of the extraction trough, and the magnitude of transient thermal deformation can be reduced. The transient thermal load can be delayed until the effect is less pronounced. This can lead to an improvement in overlay error, specifically the wafer load grid (WLG).

[0009]

[0009] According to a first aspect of the present invention, a substrate support is provided which is configured to support a substrate, the substrate support comprising: a top surface; a plurality of support members extending above the top surface; an extraction trough defined by a first circumferential wall and a second circumferential wall, the first and second circumferential walls extending above the top surface; an extraction opening formed on the top surface within the extraction trough; and one or more fluid-retaining features formed within the extraction trough.

[0010]

[0010] According to a second aspect of the present invention, a lithography apparatus is provided that includes the substrate support described above.

[0011]

[0011] According to a third aspect of the present invention, a method is provided for manufacturing a substrate support as described above, the method comprising forming one or more recesses by removing material from the top surface using laser structuring.

[0012]

[0012] A fourth aspect of the present invention provides a method for manufacturing a device, comprising supporting a substrate on a substrate support as described above.

[0013]

[0013] Further embodiments, features and advantages of the present invention, as well as the structure and operation, features and advantages of various embodiments of the present invention, will be described in detail below with reference to the accompanying drawings. [Brief explanation of the drawing]

[0014]

[0014] Next, embodiments of the present invention will be described as merely examples with reference to the attached schematic drawings. In the drawings, corresponding reference symbols indicate corresponding parts.

[0015] [Figure 1] This shows a schematic overview of a lithography apparatus. [Figure 2] The substrate support is shown in cross-section. [Figure 3] The circuit board support is shown in a plan view. [Figure 4] This diagram illustrates the path of the fluid handling structure on the substrate during exposure. [Figure 5] A circumferential cross-sectional view of a substrate support not according to the present invention is shown, and the cutting plane of the cross-sectional view passes through the outermost crowbar ring in the radial direction within the extraction trough. [Figure 6] A circumferential cross-sectional view of a substrate support according to the first embodiment of the present invention is shown, and the cutting plane of the cross-sectional view passes through the outermost crowbar ring in the radial direction within the extraction trough. [Figure 7] An extraction trough for a substrate support according to a first embodiment of the present invention is shown. [Figure 8] A circumferential cross-sectional view of a substrate support according to a second embodiment of the present invention is shown, where the cutting plane of the cross-sectional view passes through the outermost crowbar ring in the radial direction within the extraction trough. [Figure 9] An extraction trough for a substrate support according to a second embodiment of the present invention is shown. [Figure 10] A circumferential cross-sectional view of a substrate support according to a third embodiment of the present invention is shown, where the cutting plane of the cross-sectional view passes through the outermost crowbar ring in the radial direction within the extraction trough. [Figure 11] An extraction trough for a substrate support according to a third embodiment of the present invention is shown. [Figure 12] A circumferential cross-sectional view of a substrate support according to a fourth embodiment of the present invention is shown, where the cutting plane of the cross-sectional view passes through the outermost crowbar ring in the radial direction within the extraction trough. [Figure 13] An extraction trough for a substrate support according to a fourth embodiment of the present invention is shown. [Figure 14] The substrate and the substrate support are illustrated. [Figures 15A-15B] The burr is illustrated. [Figure 16] The burr is illustrated. [Figure 17] A plan view of the substrate support in which a capillary bridge of the immersion liquid is formed between adjacent burrs is illustrated. [Figure 18A] A circumferential cross-sectional view of the substrate support provided with the bridging feature is illustrated, and the cutting plane of the cross-sectional view passes through the ring of the outermost burr in the extraction gutter in the radial direction. [Figure 18B] The extraction gutter of the substrate support illustrated in FIG. 18A is illustrated. [Figure 18C] A plan view of the substrate support illustrated in FIG. 18A is illustrated. [Figure 19A] A circumferential cross-sectional view of the substrate support provided with the bridging feature is illustrated, and the cutting plane of the cross-sectional view passes through the ring of the outermost burr in the extraction gutter in the radial direction. [Figure 19B] The extraction gutter of the substrate support illustrated in FIG. 19A is illustrated. [Figure 19C] A plan view of the substrate support illustrated in FIG. 19A is illustrated. [Figure 20A] A circumferential cross-sectional view of the substrate support provided with the bridging feature is illustrated, and the cutting plane of the cross-sectional view passes through the ring of the outermost burr in the extraction gutter in the radial direction. [Figure 20B] The extraction gutter of the substrate support illustrated in FIG. 20A is illustrated. [Figure 20C] A plan view of the substrate support illustrated in FIG. 20A is illustrated.

[0016] The features shown in the drawings are not necessarily to scale, and the sizes and / or arrangements shown are not limiting. It will be understood that the drawings may include optional features that may not be essential to the present invention. Further, not all features of the device are shown in each drawing, and only some of the components relevant to explaining a particular feature may be shown in some cases. [Modes for carrying out the invention]

[0017]

[0015] In this document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (for example, having wavelengths of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm).

[0018]

[0016] The terms “reticle,” “mask,” or “patterning device” as used herein may be interpreted broadly to refer to a general-purpose patterning device that can be used to give an incoming radiation beam a patterned cross-section corresponding to a pattern created on a target portion of a substrate. The term “light bulb” can also be used in this context. In addition to classic masks (transmissive or reflective masks, binary masks, phase-shift masks, hybrid masks, etc.), other examples of such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0019]

[0017] Figure 1 schematically illustrates a lithography apparatus. The lithography apparatus includes an illumination system (also called an illuminator) IL configured to adjust a radiation beam B (e.g., UV radiation or DUV radiation), a mask support (e.g., a mask table) MT connected to a first positioner PM constructed to support a patterning device (e.g., a mask) MA and configured to precisely position the patterning device MA according to specific parameters, a substrate support (e.g., a substrate table) WT connected to a second positioner PW constructed to hold a substrate (e.g., a resist-coated wafer) W and configured to precisely position the substrate support WT according to specific parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project the pattern applied to the radiation beam B by the patterning device MA onto a target portion C of the substrate W (e.g., comprising one or more dies).

[0020]

[0018] During operation, the illumination system IL receives the radiated beam B from the radiation source SO, for example, via the 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 inducing, shaping, and / or controlling the radiation. The illuminator IL may be used to adjust the radiated beam B so that its cross-section has a desired spatial and angular intensity distribution in the plane of the patterning device MA.

[0021]

[0019] As used herein, the term “projection system” PS should be interpreted broadly to encompass various types of projection systems, including refractive optical systems, reflective optical systems, reflective-refractory optical systems, anamorphic optical systems, magneto-optical systems, electromagnetic optical systems, and / or electrostatic optical systems, or any combination thereof, as appropriate in accordance with the exposure radiation used and / or other factors such as the use of immersion liquid or vacuum. Where the term “projection lens” is used herein, it can be considered synonymous with the more general term “projection system” PS.

[0022]

[0020] The lithography apparatus is of a type in which at least a portion of the substrate W is covered with an immersion liquid having a relatively high refractive index, such as water, so as to fill the immersion space between the projection system PS and the substrate W, and this is also called immersion lithography. Further information on immersion technology is described in U.S. Patent No. 6,952,253, which is incorporated herein by reference.

[0023]

[0021] The lithography apparatus may be of a type that has two or more substrate support WTs (also called a “dual-stage”). In such a “multi-stage” machine, the substrate support WTs may be used in parallel, and / or, while a substrate W on one substrate support WT is being used to expose a pattern onto that substrate W, a preparation step for subsequent exposure of the substrate W may be performed on a substrate W located on another substrate support WT.

[0024]

[0022] In addition to the substrate support WT, the lithography apparatus may include a measurement stage (not shown in the drawings). The measurement stage is positioned to hold sensors and / or cleaning devices. The sensors may be positioned to measure the characteristics of the projection system PS or the characteristics of the radiating beam B. The measurement stage may hold multiple sensors. The cleaning devices may be positioned to clean parts of the lithography apparatus, such as a part of the projection system PS or a part of the system that provides the immersion fluid. The measurement stage may move below the projection system PS when the substrate support WT is away from the projection system PS.

[0025]

[0023] During operation, the radiating beam B is incident on a patterning device MA, such as a mask held on a mask support MT, and a pattern is formed by the pattern (design layout) present on the patterning device MA. The radiating beam B, having crossed the mask MA, passes through a projection system PS, which focuses the beam onto a target portion C of the substrate W. Using a second positioner PW and a position measuring system IF, the substrate support WT can be precisely moved to position various target portions C, for example, in a focused and aligned position within the path of the radiating beam B. Similarly, using a first positioner PM and possibly another position sensor (not explicitly shown in Figure 1), the patterning device MA can be precisely positioned relative to the path of the radiating beam B. The patterning device MA and the substrate W can be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. The substrate alignment marks P1, P2 occupy dedicated target portions in the illustration, but may be located in the space between target portions. When substrate alignment marks P1 and P2 are located between target portions C, they are known as scribe line alignment marks.

[0026]

[0024] To clarify the present invention, the Cartesian coordinate system is used. The Cartesian coordinate system has three axes, namely the x-axis, y-axis, and z-axis. Each of the three axes is orthogonal to the other two axes. A rotation about the x-axis is called an Rx rotation. A rotation about the y-axis is called a Ry rotation. A rotation about the z-axis is called an Rz rotation. The x-axis and y-axis define the horizontal plane, while the z-axis is perpendicular. The Cartesian coordinate system is not limiting to the present invention and is used only for clarification. Alternatively, another coordinate system, such as a cylindrical coordinate system, may be used to clarify the present invention. The orientation of the Cartesian coordinate system may differ, for example, such as the z-axis having a component along the horizontal plane.

[0027]

[0025] Immersion technology has been introduced into lithography systems to enable improved resolution of smaller features. In an immersion lithography apparatus, a liquid layer of immersion fluid having a relatively high refractive index is interposed in the immersion space between the apparatus's projection system PS (the patterned beam is projected through the projection system PS toward the substrate W) and the substrate W. The immersion fluid covers at least the portion of the substrate W below the final element of the projection system PS. Thus, at least the portion of the substrate W that is exposed is immersed in the immersion fluid.

[0028]

[0026] In commercial immersion lithography, the immersion fluid is water. Typically, the water is highly purified distilled water, such as ultrapure water (UPW), which is commonly used in semiconductor manufacturing plants. In immersion systems, UPW is often purified and may undergo additional processing steps before being supplied to the immersion space as the immersion fluid. In addition to water, other liquids with a high refractive index, such as hydrocarbons including fluorinated hydrocarbons, and / or aqueous solutions, can be used as the immersion fluid. It is also conceivable that other fluids other than liquids may be used in immersion lithography.

[0029]

[0027] In this specification, local immersion refers to a system in which, during use, the immersion fluid is confined to an immersion space between the final element and the surface facing the final element. The opposing surface is the surface of the substrate W, or the surface of a support stage (or substrate support WT) that is coplanar with the surface of the substrate W. (Note that, in the following text, when referring to the surface of the substrate W, unless otherwise specified, the surface of the substrate support WT is also referred to, and vice versa.) A fluid handling structure IH located between the projection system PS and the substrate support WT is used to confine the immersion fluid to the immersion space. The immersion space, filled with the immersion fluid, is smaller than the top surface of the substrate W when viewed from above, and the immersion space remains substantially stationary with respect to the projection system PS while the substrate W and substrate support WT move beneath it.

[0030]

[0028] Other immersion systems are also envisioned, such as non-confined immersion systems (so-called "all-wet" immersion systems) and tank immersion systems. In non-confined immersion systems, the immersion liquid covers more than the surface beneath the final element. The liquid outside the immersion space exists as a thin liquid film. The liquid can cover the entire surface of the substrate W, or even the substrate W and the substrate support WT that is coplanar with the substrate W. In tank-type systems, the substrate W is completely immersed in a tank of immersion liquid.

[0031]

[0029] A fluid handling structure IH is a structure that supplies immersion fluid to an immersion space, removes immersion fluid from the immersion space, and thereby confines immersion fluid in the immersion space. It includes features that are part of a fluid supply system. A configuration disclosed in PCT Patent Application Publication WO99 / 49504 is an early fluid handling structure that includes a pipe that supplies or retrieves immersion fluid from the immersion space and operates in accordance with the relative motion of the stage below the projection system PS. In more recent designs, the fluid handling structure extends along at least a portion of the boundary of the immersion space between the final element of the projection system PS and the substrate support WT or substrate W so as to partially define the immersion space.

[0032]

[0030] The fluid handling structure IH may have a variety of functions. Each function may be derived from a corresponding feature that enables the fluid handling structure IH to achieve that function. The fluid handling structure IH may be referred to by several different terms, each referring to a single function, such as barrier members, sealing members, fluid supply systems, fluid removal systems, and liquid containment structures.

[0033]

[0031] The immersion liquid may be used as an immersion liquid. In that case, the fluid handling structure IH may be a liquid handling system. When referring to features defined in this paragraph in accordance with the preceding description, it can be understood that these features include features defined in relation to liquids.

[0034]

[0032] The lithography apparatus has a projection system PS. During exposure of the substrate W, the projection system PS projects a beam of patterned radiation onto the substrate W. To reach the substrate W, the path of the radiation beam B is from the projection system PS through an immersion liquid confined by a fluid handling structure IH between the projection system PS and the substrate W. The projection system PS has a lens element at the end of the beam path, which is in contact with the immersion liquid. This lens element in contact with the immersion liquid may be referred to as the "last lens element" or "final element". The final element is at least partially surrounded by the fluid handling structure IH. The fluid handling structure IH can confine the immersion liquid below and on the opposite surface of the final element.

[0035]

[0033] As shown in Figure 1, the lithography apparatus includes a controller 500. The controller 500 is configured to control the substrate support WT.

[0036]

[0034] Inside the lithography apparatus, the substrate W is held by a support body (e.g., a pimple or bar table). The support body may also be referred to as a substrate support.

[0037]

[0035] Figures 2 and 3 show the substrate support 20. Figure 2 shows a cross-sectional view of the substrate support 20 with the substrate W clamped to it. Figure 3 shows a plan view of the substrate support 20. The substrate support 20 shown in Figures 2 and 3 and described below can be used in the lithography apparatus described in relation to Figure 1.

[0038]

[0036] The substrate support 20 may be provided with one or more crowbars 41 (i.e., protrusions or projections from the surface). The crowbars 41 may also be referred to as support members. The crowbars 41 may protrude from the upper surface 25 of the substrate support 20. The distal end of the crowbar 41 forms a plane on which the lower side of the substrate W is supported. The lower side of the substrate W is in contact with the distal end of the crowbar 41.

[0039]

[0037] The substrate support 20 is an example of an object holder. Another example of an object holder is a mask holder. The negative pressure applied between the substrate W and the substrate support 20 helps to ensure that the substrate W is held firmly in place.

[0040]

[0038] In one embodiment, the substrate support 20 includes one or more control channels 61 of a thermal controller. A gap 5 exists between the edge of the substrate W and the edge of the substrate support 20. At other times, such as when the edge of the substrate W is imaged or when the substrate W first moves under the projection system PS (as described above), the immersion space, which is filled with immersion fluid by the fluid handling structure IH (for example), will pass over the gap 5 between the edge of the substrate W and the edge of the substrate support 20, at least partially. This may cause immersion fluid from the immersion space to enter the gap 5. If immersion fluid enters between the substrate W and the support body 21, it may lead to difficulties, particularly when unloading the substrate W.

[0041]

[0039] To deal with the immersion liquid entering the gap 5, at least one drain 10, 12 is provided on the edge of the substrate W to remove the immersion liquid entering the gap 5. In the example of Figure 2, two drains 10, 12 are shown, but there may be only one drain or more than two drains. In one embodiment, each of the drains 10, 12 is annular so as to surround the entire circumference of the substrate W.

[0042]

[0040] The primary function of the first drain 10 (located radially outward from the edge of the substrate W / support body 21) is to help prevent bubbles from entering the immersion space where the immersion liquid from the fluid handling structure IH is present. Such bubbles can adversely affect imaging of the substrate W. The first drain 10 is present to help prevent gas in the gap 5 from escaping from the fluid handling structure IH into the immersion space filled with the immersion liquid. If gas escapes into the immersion space, it can create bubbles floating in the immersion space. Such bubbles, if in the path of the projection beam, can lead to imaging errors. The first drain 10 is configured to remove gas from the gap 5 between the edge of the substrate W and the edge of the recess of the substrate support 20 on which the substrate W is placed. The edge of the recess of the substrate support 20 can be optionally defined by a separate covering 101 from the support body 21 of the substrate support 20. In the x / y plane, the covering 101 may be formed as a ring surrounding the outer edge of the substrate W. The first drain 10 extracts mainly gas and a very small amount of immersion liquid.

[0043]

[0041] The second drain 12 (located radially inward from the edge of the substrate W / support body 21) is provided to help prevent liquid advancing from the gap 5 under the substrate W from hindering the efficient release of the substrate W from the substrate support WT after imaging. Providing the second drain 12 reduces or eliminates problems that may arise due to immersion liquid advancing under the substrate W.

[0044]

[0042] In this disclosure, terms such as “radially inward,” “radially inward,” “radially outward,” and “radially outward” are used to define the radial position of various features relative to the center of the substrate support 20 in a horizontal plane, that is, relative to the center of the substrate support 20 in a plane parallel to the plane formed by the distal ends of the plurality of burrs 41.

[0045]

[0043] As shown in Figure 2, the lithography apparatus includes a first extraction channel 102 and a second extraction channel 113 for passing a two-phase flow. The first and second extraction channels 102 and 113 may be formed within the support body 21 or as separate components. The first and second drains 10 and 12 are each provided with their respective openings (first extraction opening 107 and second extraction opening 117) and their respective extraction channels (first extraction channel 102 and second extraction channel 113). The extraction channels 102 and 113 are in fluid communication with their respective openings 107 and 117 through their respective passages (first extraction passage 103 and second extraction passage 114).

[0046]

[0044] A second extraction opening 117 may be provided within an extraction trough 130. The extraction trough 130 may correspond to a portion of the radial region between the substrate support 20 and the substrate W. The entire extraction trough 130 may be located above the upper surface 25 of the substrate support 20. The extraction trough 130 may be defined by circumferential seals 131, 132. The circumferential seals 131, 132 may be walls that extend circumferentially around the substrate support 20 and project above the upper surface 25 of the support body 21 of the substrate support 20. The extraction trough 130 may be a radially extending portion between the inner circumferential seal 131 and the outer circumferential seal 132. The inner circumferential seal 131 may be referred to as the first circumferential wall, and the outer circumferential seal 132 may be referred to as the second circumferential wall. The extraction trough 130 may be substantially or completely beneath the substrate W when the substrate W is supported by the substrate support 20. In other words, the extraction trough 130 may be radially inward of the edge of the substrate W when the substrate W is supported by the substrate support 20.

[0047]

[0045] In the context of the term "extraction trough" 130, "tough" may be understood to mean an open channel or trough. The extraction trough 130 may be defined by the radially outer vertical wall of the inward circumferential seal 131, the radially inner vertical wall of the outward circumferential seal 132, and the upper surface 25 of the substrate support 20. When the substrate support 20 is considered separately, the extraction trough 130 may not have a top surface. Thus, the trough defined by the surfaces described above may be open. When the substrate W is supported by the substrate support 20 during use, the lower surface of the substrate W may form the upper surface of the extraction trough 130.

[0048]

[0046] When the substrate W is supported by the substrate support 20, the distance between the upper surfaces of the circumferential seals 131 and 132 and the lower surface of the substrate W may be such that a partial seal is formed. Thus, the fluid in the extraction trough 130 can be substantially prevented from moving radially inward or radially outward of the extraction trough 130.

[0049]

[0047] The extraction trough 130 described above is part of a substrate support 20 that may not be according to the present invention, but the description of the extraction trough 130 itself may apply to the substrate support 20 according to the present invention. For example, this description of the extraction trough 130 can be applied to the first, second, third, and fourth embodiments of the present invention described below.

[0050]

[0048] Multiple crowbars 41 may be distributed across the upper surface 25 of the substrate support 20. The circumferential ring of the radially outermost crowbars 41 may be provided within the extraction trough 130. Multiple second extraction openings 117 may be provided within the extraction trough 130. Multiple second extraction openings 117 may be distributed circumferentially along the extraction trough 130. The substrate support 20 may further include other openings. For example, the substrate support 20 may include a clamp opening 127. The clamp opening 127 may be provided in a region radially inward of the substrate support 20 relative to the extraction trough 130. The clamp opening 127 may be configured to extract fluid so that when the substrate W is supported by the substrate support 20, the clamp opening 127 can create a negative pressure in the region between the substrate support 20 and the substrate W so that the substrate W can be clamped to the substrate support 20.

[0051]

[0049] The gap 5 between the covering 101 and the substrate W is created because the central opening of the covering 101 has a larger diameter than the substrate W. In some places, the gap 5 may be about 200 μm. When the fluid handling structure IH passes through the gap 5, at least some of the immersion liquid flows through the gap 5. After flowing through the gap 5, some of the immersion liquid may enter the region corresponding to the extraction trough 130 and the first extraction opening 107.

[0052]

[0050] The immersion liquid entering the extraction trough 130 can be extracted by the second extraction opening 117. For example, the second extraction channel 113 may be connected to a vacuum pressure source, i.e., a device or component that can provide an extraction pressure lower than the environment surrounding the substrate support 20. This may cause the immersion liquid entering the extraction trough 130 to be pulled toward the second extraction opening 117. In this way, the immersion liquid can be made to flow through the second extraction passage 114 and out through the second extraction channel 113.

[0053]

[0051] Even after the immersion liquid has been extracted from the extraction trough 130, some of the immersion liquid may remain on the surface inside the extraction trough 130. For example, the immersion liquid may remain on the upper surface 25 of the substrate support 20 inside the extraction trough 130. The immersion liquid may also remain on the vertical surfaces of the circumferential seals 131, 132 that define the radial boundary of the extraction trough 130. When most of the immersion liquid has been removed from the extraction trough 130, dry air may enter the extraction trough 130 through the gap 5 between the covering 101 and the substrate W. In particular, dry air may be drawn into the extraction trough 130 by the extraction pressure provided to the second extraction channel 113 and drawn out through the second extraction channel 113.

[0054]

[0052] The flow of dry air within the extraction trough 130 can lead to the evaporation of the immersion liquid present on the surface of the extraction trough 130. The evaporation of the immersion liquid from the surface of the extraction trough 130 can cause a thermal load to be applied to the surface of the extraction channel 130. Specifically, a cold load can be applied to the surface of the extraction trough 130. This cold load can lower the temperature of the support body 21 of the substrate support 20 around the extraction trough 130.

[0055]

[0053] Once all of the immersion liquid has evaporated from the surface of the extraction trough 130, the application of a cooling load to the substrate support 20 may cease. This means that the temperature of the support body 21 of the substrate support 20 around the extraction trough 130 may rise. Thus, generally, the temperature of the support body 21 of the substrate support 20 around the extraction trough 130 may depend on whether or not the immersion liquid is present on the surface of the extraction trough 130. During use, there may be periods when the immersion liquid is present on the surface of the extraction trough 130 and periods when the immersion liquid is not present on the surface of the extraction trough 130. As a result, the temperature of the support body 21 of the substrate support 20 around the extraction trough 130 may fluctuate over time.

[0056]

[0054] Temperature fluctuations of the support body 21 over time can cause structural deformation. Specifically, when the temperature of the support body 21 rises, the support body 21 may expand. When the temperature of the support body 21 falls, the temperature of the support body 21 may contract. Therefore, the exact shape and size of the substrate support 20 (and consequently the flatness of the support plane formed by the multiple burrs 41) can fluctuate over time.

[0057]

[0055] If structural deformation of the substrate support 20 occurs during one or more critical periods of operation of the lithography apparatus, the overlay error may increase. Overlay error is a measure of misalignment between corresponding features in different layers of a device manufactured by lithography. Therefore, if the thermal load on the substrate support 20 changes during critical periods, the overlay error may increase. This can occur, for example, if immersion fluid is present in the extraction trough 130 at the start of a critical period, but all of the immersion fluid evaporates during the critical period (i.e., the extraction trough 130 dries out completely). Critical periods during the operation of the lithography apparatus may include (i) when the substrate W is loaded onto the substrate support 20, (ii) during the process in which the vertical displacement and in-plane deformation of the substrate W are measured and mitigated, and (iii) during the exposure of the substrate W.

[0058]

[0056] The overlay error may also increase if the conditions within the extraction trough 130 (i.e., the presence or absence of immersion liquid) differ for each of the series of operations performed on the substrate W. For example, the overlay error may increase if the extraction trough 130 is dry when the substrate W is exposed for the first layer, and at least partially wet when the substrate W is subsequently exposed.

[0059]

[0057] Figure 5 shows a circumferential cross-sectional view of a substrate support 20 not according to the present invention (i.e., a comparative example). The cross-sectional view is taken so as to pass through the outermost radial crowbar 41 ring in the extraction trough 130 of the substrate support 20. The substrate support 20 may have a structure similar to the substrate support 20 shown in Figures 2 and 3 and described above.

[0060]

[0058] As shown in Figure 5, the upper surface 25 of the substrate support 20 within the extraction trough 130 is substantially flat. That is, there are no features other than the extraction opening 117 and the multiple crowbars 41. Additional features may be present in some cases. However, the extraction trough 130 does not have any features configured to hold fluid.

[0061]

[0059] In such a substrate support 20, the time required for the extraction trough 130 to dry completely (i.e., the time required for the extraction trough 130 to transition from a state where it is filled with immersion liquid to a state where it is substantially free of immersion liquid) can be 10 to 30 seconds. For example, the time required for the extraction trough 130 to dry completely may be approximately 20 seconds. Such a drying time may mean that immersion liquid is present in the extraction trough 130 at the start of a critical period, but that the immersion liquid may have completely evaporated during that critical period. Furthermore, such a drying time may mean that the immersion liquid has completely dried between subsequent operations. Therefore, a substrate support 20 as illustrated in Figure 5 may exhibit a relatively high overlay error.

[0062]

[0060] The substrate support 20 may be configured to operate in a dry-edge mode in which the upper surface of the inward circumferential seal 131 remains dry when the substrate W is clamped to the substrate support 20 (i.e., the immersion liquid is not present on the upper surface of the inward circumferential seal 131). The substrate support 20 may also be configured to operate in a bypass mode in which the upper surface of the inward circumferential seal 131 is wet (i.e., the immersion liquid is present on the upper surface of the inward circumferential seal 131). In dry-edge mode, the pressure difference between the extraction trough 130 and the region between the substrate W and the substrate support 20 radially inward of the inward circumferential seal 131 may be greater than in bypass mode. A larger pressure difference in dry-edge mode may mean that the extraction trough 130 dries out particularly quickly.

[0063]

[0061] The presence (or absence) of immersion liquid in the extraction trough 130 also affects the characteristics of the contact between the outward circumferential ring of the crowbar 41 and the underside of the substrate W. When immersion liquid is present in the extraction trough 130 and the substrate W is clamped to the substrate support 20, capillary force means that the upper surface of the crowbar 41 (i.e., the surface of W that contacts the underside of the substrate) is kept wet by the immersion liquid. After the substrate W is removed from the substrate support 20, the upper surface of the crowbar may remain wet for a period of time, which may be approximately 0.1 to 10 seconds.

[0064]

[0062] The immersion liquid on the upper surface of the crowbar 41 lubricates the upper surface of the crowbar 41. Therefore, when immersion liquid is present on the upper surface of the crowbar 41, the coefficient of friction between the upper surface of the crowbar 41 and the underside of the substrate W is reduced compared to when immersion liquid is not present on the upper surface of the crowbar 41. The coefficient of friction between the upper surface of the crowbar 41 and the underside of the substrate W affects the in-plane deformation within the substrate W that occurs when the substrate W is loaded onto the substrate support W. If the crowbar 41 is dry when the substrate W is clamped to the substrate support 20 and a pattern for the first layer is projected onto the substrate W, but the crowbar 41 is wet when the substrate W is clamped to the substrate support 20 and a pattern for the second layer is projected onto the substrate W, the in-plane deformation of the substrate W will differ between the first and second layers. This may lead to an increase in overlay errors. A characteristic pattern of overlay errors resulting from such in-plane deformation is called a "wafer load grid" (WLG).

[0065]

[0063] Figure 4 illustrates a schematic representation of an example of the path taken by the fluid handling structure IH with respect to the substrate W as it moves during exposure of the substrate W. For ease of explanation, the substrate W is referred to as having a "north" portion N and a "south" portion S, where the north portion N and the south portion S are radially outward portions of the substrate W separated from each other by 180°. Although not shown in Figure 4, the substrate W is supported on a substrate support WT such as the substrate support 20 described above. Although the fluid handling structure IH is described as moving on the substrate W, as described above, the relative movement between the substrate W and the fluid handling structure IH may be provided by moving the substrate support 20 while keeping the fluid handling structure IH stationary.

[0066]

[0064] In the example of the path shown in Figure 4, the fluid handling structure IH begins at the southern portion S of the substrate W (t=t1). Specifically, the fluid handling structure IH begins at a position where the southern portion S of the substrate W overlaps with the edge of the substrate W (t=t1). As a result, the immersion liquid is introduced into the southern portion S of the extraction trough 130 of the substrate support 20 (i.e., the portion of the extraction trough 130 corresponding to the southern portion S of the substrate W).

[0067]

[0065] From t=t1 to t=t3, the fluid handling structure IH moves relative to substantially all of the substrate W such that substantially all of the surface of the substrate W can be exposed. The path of the fluid handling structure IH may be a zigzag path. In other words, the fluid handling structure IH may meander across the entire substrate W.

[0068]

[0066] At t=t2, the immersion liquid on the bar installed in the southern part S of the extraction trough is the dye (i.e., substantially free of immersion liquid). At t=t3, the fluid handling structure IH terminates at the northern part N of the substrate W (i.e., reaches the end of its path). Specifically, the fluid handling structure IH terminates at a position where it overlaps with the edge of the substrate W in the northern part N of the substrate W. As a result, the immersion liquid is introduced into the northern part N of the extraction trough 130 of the substrate support 20 (i.e., the part of the extraction trough 130 corresponding to the northern part N of the substrate W).

[0069]

[0067] At t=t4, the substrate W is unloaded (i.e., removed) from the substrate support 20. When the substrate W is unloaded from the substrate support 20, the time elapsed since the fluid handling structure IH introduced the immersion liquid into the southern portion S of the extraction trough 130 (i.e., t4-t1) is longer than the time elapsed since the fluid handling structure IH introduced the immersion liquid into the northern portion N of the extraction trough 130 (i.e., t4-t3). This may mean that when the substrate W is unloaded from the substrate support 20, the upper surface of the crowbar 41 in the southern portion S of the extraction trough 130 is dry (i.e., substantially free of immersion liquid), while the upper surface of the crowbar 41 in the northern portion N of the extraction trough 130 is wet (i.e., coated with immersion liquid).

[0070]

[0068] Mechanical wear (e.g., abrasive wear) on the upper surface of the crowbar 41 when unloading the substrate W from the substrate support 20 may occur to a greater extent when the upper surface of the crowbar 41 is dry compared to when the upper surface of the crowbar 41 is wet. Therefore, if the path of the fluid handling structure IH is as described above, the wear of the crowbar 41 in the extraction trough 130 may be asymmetrical. Specifically, the crowbar 41 in the southern part S of the extraction trough 130 may wear at a greater rate than the crowbar 41 in the northern part N of the extraction trough 130. Over time, this may lead to overlay errors. This may mean that the substrate support 20 may need to be replaced. Reading the substrate support 20 to reuse it in a way that compensates for asymmetrical wear may be difficult or expensive.

[0071]

[0069] The present invention relates to a substrate support 20 configured to mitigate the problems described above. Specifically, the present invention relates to a substrate support 20 configured to retain immersion liquid in the extraction trough 130 for a longer period of time. This ensures that the extraction trough 130 does not dry out during a critical period (or reduces the risk of the extraction trough 130 drying out during a critical period), and the conditions inside the extraction trough 130 (i.e., the presence of immersion liquid) can be made consistent over a series of operations. Furthermore, by retaining the immersion liquid in the extraction trough 130 for a longer period of time, it is possible to reduce the possibility that the crowbars 41 in one part of the extraction trough 130 will get wet and the crowbars 41 in another part of the extraction trough 130 will dry out when the substrate W is unloaded from the substrate support 20. Therefore, retaining the immersion liquid within the substrate support 20 means that (i) temporary thermal deformation of the substrate support 20 during and between critical periods, (ii) changes in the coefficient of friction between the upper surface of the crowbar 41 and the lower side of the substrate W during and between critical periods, and (iii) the occurrence of asymmetric wear of the crowbar 41 over time within the extraction trough 130 can be reduced. This means that overlay errors and, for example, the wafer load grid (WLG) can be improved.

[0072]

[0070] According to the present invention, the substrate support 20 comprises a support body 21 having an upper surface and a plurality of crowbars 41 (also referred to as support members). The plurality of crowbars 41 extend above the upper surface. The substrate support 20 further comprises an extraction trough 130 defined by a first circumferential wall and a second circumferential wall. Similar to the plurality of crowbars 41, the first circumferential wall and the second circumferential wall extend above the upper surface. The substrate support 20 further comprises an extraction opening formed on the upper surface within the extraction trough 130. The extraction opening referred to in relation to the present invention may be the same as the second extraction opening 117 referred to in relation to the substrate support 20 illustrated in Figures 2 and 3. The substrate support 20 further comprises one or more fluid-retaining features formed within the extraction trough 130. The one or more fluid-retaining features are defined by the support body 21. In this context, "defined by..." may mean that the outline (i.e., shape) of the fluid-retaining feature is formed by the support body 21. In other words, the surface defining the boundary of the fluid-retaining feature may be the surface of the support body 21. For example, the upper surface 25 of the support body 21 does not have to be flat and may have a contour so as to be able to retain the immersion fluid. By providing one or more fluid-retaining features within the extraction trough 130, the immersion fluid entering the extraction trough 130 can be retained within the extraction trough 130 for a longer period of time. As a result, the overlay error may be improved as described above.

[0073]

[0071] The substrate support according to the present invention may be the same as the substrate support 20 shown in Figures 2, 3, and 5 and described above. The main difference may be the provision of fluid retention features within the extraction troughs 230, 330, 430, and 530. Other features, for example, the structure of the extraction troughs 230, 330, 430, and 530 themselves may be the same as the substrate support 20 shown in Figures 2, 3, and 5 and described above in the substrate supports 200, 300, 400, and 500 according to the present invention.

[0074]

[0072] Figures 6 and 7 illustrate a substrate support 200 according to a first embodiment of the present invention. Figure 6 shows a circumferential cross-sectional view of the substrate support 200. The cross-sectional view passes through the radially outermost crowbar 241 ring within the extraction trough 230. Figure 7 illustrates the structure of the extraction trough 230, which may be the same as the extraction trough 130 described above. The extraction trough 230 is defined by an inward circumferential seal 231 (first circumferential wall), an outward circumferential seal 232 (second circumferential wall), and the upper surface 225 of the substrate support 200. In particular, the lower horizontal plane of the extraction trough 230 is defined by the upper surface 225 of the substrate support 200, and the vertical plane of the extraction trough 230 defining the radial boundary of the extraction trough 230 is the radially outward vertical surface 231a of the radially inward circumferential seal 231 and the radially inward inner surface 232a of the radially outward circumferential seal 232. The radially inward circumferential seal 231 may have an upper surface 231b, and the radially outward circumferential seal may have an upper surface 231a.

[0075]

[0073] The extraction trough 230 may contain a plurality of extraction openings 217 and a plurality of crowbars 241 distributed in the circumferential direction. The plurality of extraction openings 217 and the plurality of crowbars 241 may be uniformly distributed along the circumference of the extraction trough 230.

[0076]

[0074] In some cases, when the extraction trough 230 is completely dry, the immersion liquid may remain on the surface of the crowbar 241 longer than on other surfaces of the extraction trough 230 (for example, the upper surface 225 of the substrate support 200 within the extraction trough 230). The drying of the surface of the crowbar 241 may not be uniform along the circumference of the substrate support 200. Specifically, crowbars 241 positioned further away from the extraction opening 217 will dry faster than crowbars 241 positioned closer to the extraction opening 217. Therefore, when the extraction trough 230 is completely dry, crowbars 241 positioned around the midpoint between adjacent extraction openings 217 will dry first, and crowbars 241 positioned adjacent to the extraction opening 217 will dry last.

[0077]

[0075] Furthermore, in some cases, a crowbar 241 positioned further away from the extraction opening 217 (for example, a crowbar 241 located around the midpoint between adjacent extraction openings 217) may not get wet at all when the immersion liquid is present in the extraction trough 230. Whether or not a crowbar 241 positioned further away from the extraction opening 217 (for example, a crowbar 241 located around the midpoint between adjacent extraction openings 217) will get wet when the immersion liquid is present in the extraction trough 230 is unpredictable.

[0078]

[0076] Generally, a crowbar 241 that is close to the extraction opening 217 may have a longer and more consistent drying time than a crowbar 241 that is not close to the extraction opening 217. Therefore, a crowbar 241 that is close to the extraction opening 217 is likely to remain wet throughout the critical operation of the substrate support 200 and during subsequent operations of the substrate support 200.

[0079]

[0077] In consideration of the above, in order to improve the spatial homogeneity of the drying of the crowbars 241, it is preferable that each crowbar 241 is close to the extraction opening 217 (i.e., close enough to the extraction opening 217 so that the drying time is relatively consistent and relatively long). To achieve this, it is preferable to increase the number of extraction openings 217. For example, the number of extraction openings 217 may be more than 10, preferably more than 50, preferably more than 100, and even more preferably more than 200, for example, 220. In some cases, the preferred number of extraction openings 217 may depend on the radius of the extraction trough 230. The number of extraction openings 217 mentioned above may be particularly applicable to a substrate support 200 having a radius of approximately 150 mm.

[0080]

[0078] The distance between adjacent extraction openings 217 along the circumference in which multiple crowbars 241 are arranged in the extraction trough 230 may be called the separation distance. The separation distance may be measured between the center points of adjacent extraction openings 217. The separation distance between adjacent extraction openings 217 may be less than 90 mm, preferably less than 20 mm, and more preferably less than 10 mm. The number of crowbars 241 between adjacent extraction openings 217 in the extraction trough 230 (i.e., the number of crowbars 241 arranged along a single separation distance) may be less than 50, preferably less than 10, and more preferably 6 or less.

[0081]

[0079] A further advantage of increasing the number of extraction openings 217 is that the velocity of the airflow within the extraction trough 230 is reduced. This results in a decrease in the evaporation rate within the extraction trough 230 and a reduction in the drag applied to the immersion liquid by the airflow within the extraction trough 230. As a result, the extraction trough 230 (and any fluid-holding features within it) can hold a larger amount of immersion liquid for a longer period of time. In other words, the time it takes for the immersion liquid to dry completely within the extraction trough 230 is extended.

[0082]

[0080] Providing an excessive number of extraction openings 217 can unnecessarily complicate the design and manufacture of the substrate support 200. Therefore, the number of extraction openings 217 may be less than 1000, preferably less than 500, and more preferably less than 250. Additionally or alternatively, the spacing between adjacent extraction openings 217 may be greater than 2 mm, preferably greater than 6 mm. Additionally or alternatively, the number of crowbars 241 in the extraction trough 230 between adjacent openings 217 (i.e., the number of crowbars 241 arranged along a single spacing) may be greater than 1, preferably greater than 2, more preferably 4 or more, and optionally greater than 5.

[0083]

[0081] It will be understood that the configuration of the extraction opening 217 described above can be applied to any substrate support 200, regardless of whether the substrate support 200 includes other features described in this disclosure. For example, the configuration of the extraction opening 217 described above may be applied to a substrate support 20 that does not have any fluid retention features, such as the one shown in Figures 2 and 3.

[0084]

[0082] The height of each crowbar 241 may be approximately 100 μm to approximately 200 μm. The heights of the inward circumferential seal 231 and the outward circumferential seal 232 may be several μm lower than the height of the crowbar 241, so that when the substrate W is supported by the substrate support 200, a partial seal is formed between the circumferential seals 231, 232 and the underside of the substrate W, but the circumferential seals 231, 232 do not come into contact with the underside of the substrate W.

[0085]

[0083] As shown in Figures 6 and 7, the upper surface 225 of the substrate support 200 in the extraction trough 230 may have one or more fluid-retaining features. These fluid-retaining features may be recesses 250 in the upper surface 225 of the extraction trough 230, for example, indentations. The recess 250 may have a lower surface 252 and a side surface 251. The lower surface 252 and the side surface 251 of the recess 250 may define a reservoir. That is, the recess 250 may be configured to collect and store immersion fluid.

[0086]

[0084] The lower surface 252 of the recess 250 may be lower than the surface on which the extraction opening 217 is defined. For example, if the extraction opening 217 is formed on the upper surface 225 of the substrate support 200, the lower surface 252 of the recess 250 may be lower than the upper surface 225 of the substrate support 200. By providing a recess 250 having a lower surface 252 that is lower than the other surfaces 225 of the substrate support 200, the recess 250 may be able to prevent the extraction of immersion liquid through the extraction opening 217. In other words, the extraction opening 217 may not be able to extract the immersion liquid collected in the recess 250. Thus, the immersion liquid that collects in the recess 250 may remain in the extraction trough 230 for a longer period of time.

[0087]

[0085] The recess 250 may include a depression, recess, pit, or pocket in the upper surface 225 of the substrate support 200. Generally, the recess 250 can take any form that allows it to act as a reservoir. That is, the recess 250 can take any form that allows the immersion liquid to be collected and stored (even temporarily) in the extraction trough 230.

[0088]

[0086] The recess 250 can be manufactured using any suitable method. For example, the process used to manufacture the recess 250 may include drilling. Additionally or alternatively, the process used to manufacture the recess 250 may include laser structuring.

[0089]

[0087] Even if the immersion liquid collected in the recess 250 is substantially prevented from being extracted from the extraction trough 230 through the extraction opening 217, the immersion liquid can evaporate over time. Therefore, it would be preferable that the depth of the recess 250 be such that the recess 250 does not dry out before the end of a particular period (i.e., not all of the immersion liquid evaporates). The depth of the recess 250 may be the distance between the upper surface 225 of the substrate support 200 and the lowest point of the recess 250. The particular period may be longer than 10 seconds, preferably longer than 30 seconds, and even more preferably longer than 50 seconds. For example, the particular period may be 60 seconds. Ensuring that the immersion liquid remains in the extraction trough 230 over a particular period may mean that the extraction trough 230 does not dry out completely during a critical period, and that the conditions in the extraction trough 230 (i.e., the presence of immersion liquid) can be made consistent over a series of critical periods and between critical periods. Preferably, the specific period is longer than the length of time required to complete all exposures on the substrate W, or longer than the total duration spent by the substrate W on the substrate support 200 during the production process.

[0090]

[0088] In order to ensure that the immersion liquid remains in the recess 250 for a specific period of time, the depth of the recess 250 may be greater than 10 μm, preferably greater than 100 μm.

[0091]

[0089] Providing a recess 250 with excessive depth may mean that the flow in the extraction trough 230 will be affected. Also, providing a recess 250 with excessive depth may complicate the manufacturing process used to form the recess 250. For example, laser structuring may not be suitable for forming the recess 250 if the depth of the recess 250 is excessively large. Considering this, it would be preferable that the depth of the recess 250 be less than 500 μm, preferably less than 200 μm, and more preferably less than 120 μm.

[0092]

[0090] The size, shape, and arrangement of the recesses 250 are not particularly limited. However, it is preferable that the multiple recesses 250 be arranged as an array and distributed substantially uniformly in the circumferential and radial directions across the upper surface 225 of the extraction trough 230. This can ensure that the amount of immersion liquid held within the extraction trough 230 is substantially uniform along the extraction trough 230. This can ensure that the thermal load applied to the substrate support 200 is substantially uniform along the extraction trough 230, thereby reducing variable deformation around the extraction trough 230. Furthermore, uniform distribution of the recesses 250 can ensure that advantageous fluid retention characteristics and their technical effects are present throughout the extraction trough 230.

[0093]

[0091] The cross-sectional shape of the recess 250 (in a plane parallel to the support plane) may be circular, rectangular, or any other suitable shape. A circular recess 250 would be less complex to manufacture if the manufacturing process involves drilling. If the recess 250 has a rectangular cross-section, it would be possible to arrange the recess 250 spatially efficiently.

[0094]

[0092] The outer shape of the recess 250 below the level of the upper surface 225 of the substrate support 200 is not particularly limited. For example, when the cross-section of the recess 250 is circular, the overall outer shape of the recess 250 may be hemispherical, cylindrical, or conical. When the cross-section of the recess 250 is rectangular, the outer shape of the recess 250 may be cubic or pyramidal.

[0095]

[0093] The recesses 250 may have a maximum width. If the recesses 250 are circular, the maximum width may be the diameter of the circular cross-section. If the recesses 250 are rectangular, the maximum width may be the maximum dimension of the rectangle, i.e., the distance between the diagonals. The maximum width of the multiple recesses 250 may be greater than 10 μm, preferably greater than 100 μm, and more preferably greater than 150 μm. This may be to ensure that the immersion liquid can be effectively collected in the multiple recesses 250. The maximum width of the multiple recesses 250 may be less than 2,000 μm, preferably less than 1,000 μm, and more preferably less than 500 μm. If the maximum width of the multiple recesses 250 is too large, the immersion liquid flowing through the extraction trough 230 toward the extraction opening 217 will draw the immersion liquid collected in the recesses 250 out of the recesses 250 and into the flow of extracted immersion liquid in the extraction trough 230. This could result in all of the immersion liquid being extracted through the extraction opening 217. Therefore, by providing a recess 250 having a maximum width smaller than the value described above, the immersion liquid can be effectively retained within the extraction trough 230.

[0096]

[0094] Multiple recesses 250 can be arranged on the upper surface 225 such that the proportion of the upper surface 225 occupied by the recesses 250 is greater than 50%, preferably greater than 75%, and more preferably greater than 85%. By providing the recesses 250 to cover this size of the upper surface 225 of the substrate support 200, it is possible to ensure that the thermal load (cold load) applied to the substrate support 200 in the extraction trough 230 is substantially uniform. Furthermore, it is possible to ensure that the cold load applied to the substrate support 200 when the immersion liquid is present only in the recesses 250 is sufficiently similar to the cold load applied to the substrate support 200 when the immersion liquid is present throughout the entire extraction trough 230. As a result, the temporary structural deformation of the substrate support 200 can be substantially reduced.

[0097]

[0095] Generally, the size, shape, and density of the recesses 250 may be uniform along the extraction trough 230, but may not be in some embodiments. For example, at least one of the size, shape, and density of the recesses 250 may be adjusted according to their circumferential position within the extraction trough 230. This may be done if measurement and analysis determine that it is preferable for one or more parts of the extraction trough 230 to hold more immersion fluid than other parts of the extraction trough 230. For example, as shown in Figure 4, when the fluid handling structure IH moves relative to the substrate W, it may be preferable to provide a larger fluid holding capacity in the southern part S of the extraction trough 230 (i.e., the part of the extraction trough 230 where a longer time elapses between the time the immersion fluid is supplied to that part of the extraction trough 230 and the time until the substrate W is unloaded from the substrate support 200).

[0098]

[0096] In some embodiments, the recess 250 may comprise a plurality of grooves (not shown). In this context, a groove means a relatively long and / or relatively narrow notch or depression in the upper surface 225 of the substrate support 200 within the extraction trough 230. The function of the grooves may be the same as that described above in relation to other types of recesses 250.

[0099]

[0097] For example, the recess 250 may have a plurality of grooves extending circumferentially along the extraction channel 230. The plurality of grooves may be arranged radially and / or as an array. That is, subsequent circumferential grooves may be located at different radial positions.

[0100]

[0098] Figure 8 shows a circumferential cross-sectional view of a substrate support 500 according to a second embodiment of the present invention, where the cutting plane of the cross-sectional view passes through the ring of the radially outermost crowbar 541 in the extraction trough 530. Figure 9 shows the extraction trough 530 of the substrate support 500 according to a second embodiment of the present invention. In the second embodiment, the substrate support 500 compromises a plurality of radially extending grooves 550. Each of the grooves 550 may extend from a position close to the radially outer surface 531a of a radially inward circumferential seal 531 to a position close to the radially outer surface 532a of a radially outward circumferential seal 532. The radially inward circumferential seal 531 may have an upper surface 531b, and the radially outward circumferential seal 532 may have an upper surface 532b. Each of the grooves 550 may have a bottom surface 552 and a vertical surface 551. The lowest surface 552 of the groove 550 may be below the upper surface 525 of the substrate support 500.

[0101]

[0099] The grooves 550 may be arranged in the circumferential direction. That is, different grooves 550 may have different circumferential positions. The distance between adjacent grooves 550 in the circumferential direction (i.e., groove pitch p) may be greater than 25 μm, preferably greater than 50 μm. The distance between adjacent grooves 550 in the circumferential direction may be less than 150 μm, preferably less than 100 μm. The distance between adjacent grooves 550 may be the distance between the two closest edges of the grooves 550. For example, as shown in Figure 8, the distance between adjacent grooves 550 may be the distance between the right edge of the first groove 550 and the left edge of the second groove 550.

[0102]

[0100] The grooves 550 may be provided so as not to interfere with other features in the extraction trough 530. For example, the grooves 550 may be positioned so as not to interfere with (i.e., coincide with, intersect with, or touch) the crowbars 541 and / or the extraction openings 517. The grooves 550 may not be provided in the circumferential region of the substrate support 500 where the crowbars 541 and / or the extraction openings 517 are located (i.e., where the crowbars 541 and / or the extraction openings 517 are provided, the grooves 550 may be omitted). Thus, in these circumferential regions, the distance between adjacent grooves 550 may be greater than the spacing values ​​given above. Generally, in most of the extraction trough 530 (e.g., more than 50%, preferably more than 75%, and even more preferably more than 90% of the extraction trough 530), the distance between adjacent grooves 550 may be as described above (i.e., 25 μm to 150 μm, preferably 50 μm to 100 μm). In the remainder of the extraction trough 530, the distance between adjacent grooves 550 may be greater to allow for the presence of other features (e.g., crowbars 541 and / or extraction openings 517). Alternatively, the grooves 550 may be reoriented to bypass crowbars 541 and / or extraction openings 517.

[0103]

[0101] The values ​​given above for the depth of the recess 250 can also be applied to the groove 550. In the case of the groove 550, the maximum width may be a dimension perpendicular to the direction in which the groove 550 extends. The width of the groove 550 may be greater than 50 μm and less than 100 μm. Preferably, the width of the groove 550 may be greater than 85 μm and less than 100 μm. A groove 550 having a width in this range can exert a strong capillary force on the immersion liquid in the extraction trough 530, drawing the immersion liquid into the groove 550. Thus, when the immersion liquid is present in the extraction trough 530 (for example, while the immersion liquid is being extracted from between the substrate W and the substrate support 500 through the extraction opening 517), the groove 550 can be filled with the immersion liquid. A strong adhesive force will exist between the surfaces 551 and 552 of the groove 550. This may mean that there will be less immersion liquid available on the surface of the extraction trough 530. As a result, the evaporation rate of the immersion liquid in the extraction trough 530 can be reduced. Therefore, the immersion liquid is retained in the extraction trough 530 for a longer period of time.

[0104]

[0102] Figures 10 and 11 illustrate a substrate support 300 according to a third embodiment of the present invention. Figure 10 shows a circumferential cross-sectional view of the substrate support 300. The cross-sectional view passes through the radially outermost crowbar 341 ring within the extraction trough 330. Figure 11 illustrates the extraction trough 330 of the substrate support 300. Similar to the first embodiment, the extraction trough 330 may be as described in relation to the substrate support 20 shown in Figures 2 and 3.

[0105]

[0103] In the third embodiment, the extraction opening wall 351 may extend circumferentially around the extraction opening 317. The extraction opening wall 351 may project above the upper surface 325 of the substrate support 300.

[0106]

[0104] The extraction opening wall 351 may be configured to prevent the extraction of immersion liquid from the extraction trough 330. Specifically, the extraction opening wall 351 may be configured to prevent the extraction of immersion liquid below the level of the upper surface 352 of the extraction opening wall 351. Thus, once immersion liquid enters the extraction trough 330, it can be collected within the extraction trough 330 up to the level of the upper surface 352 of the extraction opening wall 351. In other words, the reservoir 350 (i.e., the area where immersion liquid can collect) may be defined by the radially outer surface 331b of the radially inner circumferential seal 331, the radially inner surface 332a of the radially outer circumferential seal 332, the upper surface 325 of the substrate support 300 in the extraction trough 330, and the extraction opening circumferential wall 351.

[0107]

[0105] In order to ensure that the immersion liquid remains in the extraction trough 330 for the specific period mentioned above, the height of the extraction opening wall 351 (i.e., the distance between the upper surface 325 of the substrate support 300 and the upper surface 352 of the extraction opening wall 351) may be greater than 10 μm, preferably greater than 100 μm, and more preferably greater than 150 μm. The height of the extraction opening circumferential wall 351 may be less than 2000 μm, preferably less than 1000 μm, and more preferably less than 500 μm. This may be to ensure that the extraction opening circumferential wall 351 does not obstruct the ability of the extraction opening 317 to extract most of the immersion liquid from the extraction trough 330.

[0108]

[0106] Similar to the recess 250, the proportion of the upper surface 325 within the extraction trough 330 that is covered by the reservoir 350 (at least partially defined by the extraction opening wall 351) is greater than 50%, preferably greater than 75%, and more preferably greater than 85%. The reservoir 350 may cover the entire extraction trough 330, except for the areas occupied by the bar 341 and the extraction opening circumferential wall 351.

[0109]

[0107] Figures 12 and 13 illustrate a substrate support 400 according to a fourth embodiment of the present invention. Figure 12 shows a circumferential cross-sectional view of the substrate support 400. The cross-sectional view passes through the circumferential ring of the radially outermost crowbar 441 in the extraction trough 430. Figure 13 shows the extraction trough 430 of the substrate support 400. According to the fourth embodiment of the present invention, trenches 450 may be provided around the bases of the multiple crowbars 441 in the extraction trough 430. In this context, trenches 450 may mean narrow channels cut into or otherwise formed in the upper surface 425. Trenches 450 may be referred to as moats.

[0110]

[0108] The trench 450 may have a lower surface 452. The lower surface 452 may be lower than the surface on which the extraction opening 417 is formed. For example, if the extraction opening 417 is formed on the upper surface 425 of the substrate support 400, the lower surface 452 of the trench 450 may be lower than the upper surface 425 of the substrate support 400. The trench 450 may be configured to collect and store the immersion liquid in the extraction trough 430. The immersion liquid collected in the trench 450 may not be extracted through the extraction opening 417.

[0111]

[0109] By providing circumferential trenches 450 around multiple crowbars 441 within the extraction trough 430, the period during which the immersion fluid is available to lubricate the upper surfaces of the crowbars 441 can be extended. Thus, it can be ensured that the immersion fluid is available to lubricate the crowbars 441 during a series of critical periods and between critical periods. As described above, this means that the coefficient of friction will be consistent during a series of critical periods and between critical periods. As a result, the overlay, specifically the wafer load grid (WLG), can be improved.

[0112]

[0110] The maximum width of the circumferential trench 450 around the bases of the multiple crowbars 441 may be the same as the maximum width described above in relation to the recess 250. The minimum and maximum depths of the circumferential trench 450 around the bases of the multiple crowbars 441 may be the same as those described above in relation to the multiple recess 250.

[0113]

[0111] The features of the first to fourth embodiments are not mutually exclusive. That is, some embodiments may include features of the first, second, third, and fourth embodiments. For example, the substrate support 200 according to the present invention may include a plurality of recesses 250 distributed over the upper surface 225 of the substrate support 200 within the extraction trough 230, and may also include an extraction opening circumferential wall 351. Such a substrate support 200 may additionally or alternatively include trenches 450 arranged circumferentially around the bases of a plurality of burrs 241 within the extraction trough 230.

[0114]

[0112] Fluid retention features may be provided within the portion of the substrate support 20 other than the extraction trough 130. For example, the fluid retention feature may be provided radially outward of the outer circumferential seal 132. For example, the fluid retention feature may be provided on the upper surface 25 of the substrate support 20 within the portion of the substrate support 20 in which the first extraction opening 107 is formed, as shown in Figure 14. Part or all of this portion of the substrate support 20 may be radially outward of the edge of the substrate W. The fluid retention feature may be located between the outer circumferential seal 132 and the first extraction opening 107. The fluid retention feature may be any of those described herein. For example, the fluid retention feature may be a groove such as the groove 550 described in relation to Figures 8 and 9.

[0115]

[0113] Figure 14 illustrates the substrate W and the substrate support 20. The substrate support 20 may be substantially the same as the substrate support 20 shown in Figure 2, except as described below. The substrate support 20 shown in Figure 14 may include any of the fluid retention features described above and illustrated in Figures 6 to 13.

[0116]

[0114] As described above, the substrate support 20 comprises a plurality of crowbars 41a, 41b. The ring of the radially outermost crowbar 41b may be located within the extraction trough 130. That is, the ring of the radially outermost crowbar 41b may be located radially outside the inner circumferential seal 131 and radially inside the outer circumferential seal 132. The remaining crowbars 41a may be located outside the extraction trough 130, i.e., radially inside the radially inner seal 131.

[0117]

[0115] The ring of the radially outermost crowbar 41b may have a different shape from the other crowbars 41a of the substrate support 20. Specifically, the shape of the ring of the radially outermost crowbar 41b may be configured so that the immersion liquid can be retained on the crowbar 41b. This may mean that the distal end of the ring of the radially outermost crowbar 41b is wet throughout the entire period during which the series of operations (e.g., clamping the substrate W to the substrate support 20) are performed. As a result, the coefficient of friction between the upper surface of the crowbar 41b and the lower side of the substrate W may remain substantially constant throughout the entire series of operations. Thus, as described above, overlay errors (specifically overlay errors resulting from in-plane deformation) can be reduced.

[0118]

[0116] Figures 15A and 15B illustrate a crowbar 41b configured to hold immersion liquid in its vicinity. The crowbar 41b illustrated in Figures 15A and 15B is a stepped crowbar. The crowbar 41b comprises a base and a tip. The proximal end 43 of the base is connected to the upper surface 25 of the substrate support 20. The base of the crowbar 41b extends distally (i.e., away from the upper surface 25) to the distal end of the base. The distal end of the base may be connected to the proximal end of the tip at interface I. The tip extends above the distal end of the base to the distal end 42 of the tip. The distal end 42 of the tip may be configured to contact the underside of the substrate W. That is, the distal end 42 of the tip may form the upper surface of the crowbar 41b, on which the substrate W is supported.

[0119]

[0117] As described above, the outer shape of the burrs of the circumferential ring of the radially outermost burr 41b may be frustoconical. That is, the diameter of the burr 41b may gradually decrease as the burr 41b extends distally. However, for one or more of the burrs of the circumferential ring of the radially outermost burr 41b, there may be an abrupt change in the diameter of the burr 41b at the interface I between the base and tip of the burr 41b. That is, there may be a stepped change in the diameter of the burr 41b. The diameter of the proximal end of the tip may be substantially smaller than the diameter of the distal end of the base.

[0120]

[0118] The tip may extend above the top surface 47 of the base. The top surface 47 may be the surface of the base at the distal end of the base, substantially parallel to the upper surface 25 of the substrate support 20. A portion of the top surface 47 of the base may be exposed. This exposed top surface 47 may extend circumferentially around the base of the tip.

[0121]

[0119] Generally, one or more of the burrs in the circumferential ring of the radially outermost burr 41b may have a stepped shape, the step consisting of a substantially vertical surface of the base, a top surface 47 of the base, and a substantially vertical surface 44 of the tip. This configuration may allow the immersion fluid to be retained around the distal end 42 of the tip. Thus, the distal end 42 of the burr 41b may remain wet throughout the entire series of operations performed by the lithography apparatus.

[0122]

[0120] The crowbar 41b may have a total height H. The total height H may consist of a base height h1 and a tip height h2. The diameter d2 of the distal end 42 of the tip may be substantially the same as the diameter of the distal end of the other crowbars 41a of the substrate support 20. The diameter d1 of the proximal end 43 of the base may be larger than the diameter of the proximal end of the other crowbars 41a of the substrate support 20, taking into account the stepped decrease in the diameter of the crowbar 41b at the interface I between the base and the tip.

[0123]

[0121] The crowbar 41b shown in Figure 15B may be substantially the same as the crowbar 41b shown in Figure 15A, except that the crowbar 41b shown in Figure 15B further comprises a trench 45. The trench 45 may be defined at the base of the crowbar 41b. The trench 45 may be recessed in the top surface 47 of the base of the crowbar 41b. The trench 45 may extend circumferentially around the proximal end of the tip. The trench 45 may allow immersion fluid to be collected therein. Thus, the trench 45 can act as an immersion fluid reservoir that can provide immersion fluid to the distal end 42 of the crowbar 41b, thereby keeping the distal end 42 of the crowbar wet during a series of operations of the lithography apparatus. The trench 45 may have a depth h3.

[0124]

[0122] Figure 16 illustrates an example of a crowbar 41b configured to collect immersion fluid at its distal end. The crowbar 41b may be the outermost crowbar 41b ring. The crowbar 41b extends from the proximal end 43 (where the crowbar 41b is connected to the body 21 of the substrate support 20) to the distal end 42. The distal end 42 of the crowbar 41b may provide the upper surface 48 of the crowbar 41b, on which the substrate W is supported.

[0125]

[0123] The crowbar 41b shown in Figure 16 further comprises a defined reservoir 49 therein. The reservoir 49 is formed at the distal end 42 of the crowbar 41b. The reservoir 49 may be a recess (otherwise it may be called a hole or depression) at the distal end 42 of the crowbar 41b. The reservoir 49 may be recessed in the upper surface 48 (i.e., the distal surface) of the crowbar 41b, and more specifically, it may be recessed in the radially inward portion (i.e., the central portion) of the upper surface 48 of the crowbar 41b. Thus, the shape of the portion of the upper surface 48 that contacts the substrate W when the substrate W is supported on the substrate support 20 may be annular, and the annulus surrounds the reservoir 49. The reservoir 49 may be configured to hold immersion fluid, and thus can provide immersion fluid to the upper surface 48 at the distal end 42 of the crowbar 41b, thereby keeping the upper surface 48 of the crowbar wet during a series of operations of the lithography apparatus.

[0126]

[0124] The depth (L4) of the reservoir 49 (i.e., the distance between the upper surface 48 of the bar 41b and the lowest surface of the reservoir 49) may be greater than 10 μm, preferably greater than 50 μm, and more preferably greater than 80 μm. The diameter of the reservoir 49 (i.e., the horizontal dimension of the reservoir 49) may be greater than 10 μm, preferably greater than 50 μm, and more preferably greater than 80 μm. Increasing the size of the reservoir 49 can increase the volume of immersion liquid that the reservoir 49 can store. With increased storage capacity, the bar 41b may be able to keep the upper surface 48 of the bar 41b wet for a longer period of time. The depth (L4) of the reservoir 49 may be less than 200 μm, preferably less than 150 μm, and more preferably less than 100 μm. The diameter of the reservoir 49 may be less than 200 μm, preferably less than 150 μm, and more preferably less than 100 μm. For example, the diameter of the reservoir may be 90 μm. In general, the diameter of the reservoir may be less than half, preferably less than one-third, of the diameter of the distal end 42 of the bar 41 on which the reservoir 49 is formed. In some cases, providing the reservoir 49 at the distal end 42 of the bar 41b may affect the structural integrity of the bar 41b. Ensuring that the size of the reservoir 49 is not excessive means that the effect of providing the reservoir 49 on the structural integrity of the bar 41b is not greater than necessary.

[0127]

[0125] In some embodiments, the burrs 41b of the circumferential ring of the outermost burr 41b may have a standard shape (e.g., a frustoconical shape) without any of the modifications illustrated in Figures 15A, 15B, and 16. In such embodiments, the asymmetric drift rate of the burrs 41b of the ring of the outermost burr 41b (i.e., the rate at which the asymmetry of the burrs 41b of the ring of the outermost burr 41b increases) can be reduced by increasing the surface area of ​​the upper surface of the burr 41b (i.e., the flat surface at the distal end of the burr 41b, on which the lower side of the substrate W is supported). The surface area of ​​the upper surface of the burr 41b that is in direct contact with the lower side of the substrate W would preferably be greater than 20% of the nominal area of ​​the upper surface of the burr 41b, preferably greater than 30% of the nominal area of ​​the upper surface of the burr 41b, and more preferably greater than 40% of the nominal area of ​​the upper surface of the burr 41b. The surface area of ​​the upper surface of the crowbar 41b that is in direct contact with the underside of the substrate W is preferably less than 60% of the nominal surface area of ​​the crowbar's upper surface. The nominal surface area of ​​the crowbar's upper surface may be the surface area of ​​the upper surface of a crowbar having a standard shape (i.e., not conforming to the geometry around the distal end 42 to improve fluid retention).

[0128]

[0126] In some embodiments, a substrate support 20 comprising one or more of the crowbars 41b described above with reference to Figures 15A, 15B, and 16 may also comprise any of the other fluid retention features described above. In other embodiments, the substrate support 20 may comprise one of the crowbars 41b described above with reference to Figures 15A, 15B, and 16, but may not comprise any of the other fluid retention features described above. In other words, the crowbars 41b described above with reference to Figures 15A, 15B, and 16 may be implemented within a substrate support 20 in the absence of the other features described in this disclosure.

[0129]

[0127] It has been observed that when the extraction trough 130 is completely dry, a region of immersion liquid may form between adjacent burrs 41. The region of immersion liquid may be capillary crosslinking of the immersion liquid. Capillary crosslinking may extend between adjacent burrs 41 so as to connect (i) the immersion liquid coating one burr 41 and (ii) the immersion liquid coating an adjacent burr 41.

[0130]

[0128] Figure 17 shows a plan view of the substrate support 600, in which a first capillary bridge of the immersion liquid IL is formed between the first crowbar 641A and the second crowbar 641B, and a second capillary bridge of the immersion liquid IL is formed between the second crowbar 641B and the third crowbar 641C. The first, second, and third crowbars 641A, 64B, and 641C are arranged in the extraction trough 630 between the radially inner wall 631 and the radially outer wall 632. As described above, the radially inner wall 631 has a radially outer surface 631a and an upper surface 631b, and the radially outer wall 632 has a radially inner surface 632a and an upper surface 632b (see Figures 18B, 19B, and 20B). The extraction trough 630 further comprises a plurality of extraction openings 617, each of which is in fluid communication with a second extraction passage 614 (see Figures 18A, 19A, and 20A). The bar 641A, 641B, and 641C protrude from the support body 621 of the substrate support 600 (see Figures 18B, 19B, and 20B). The shape of the capillary bridge may correspond to an area of ​​the extraction trough 630 with relatively low turbulence. Relatively low turbulence may mean that the drying time of the immersion liquid in the capillary bridge is longer than the drying time of the immersion liquid in other parts of the extraction trough 630.

[0131]

[0129] The first and second capillary bridges may be continuous (i.e., connected to each other). Similar capillary bridges may be formed between other of a plurality of burrs 641 distributed along the extraction trough 630 of the substrate support 600. Capillary bridges may not be formed where an extraction opening 617 is present. For example, if a fourth burr (not shown) is adjacent to a first burr 641A, but an extraction opening 617 is interposed between the fourth burr and the first burr 641A, then capillary bridges will not be formed between the first burr 641A and the fourth burr.

[0132]

[0130] Capillary bridges can follow an arch-shaped path between adjacent burrs. For example, a capillary bridge formed between a first burr 641A and a second burr 641B can follow an arch-shaped path between the first burr 641A and the second burr 641B. The arch-shaped path along which the capillary bridge extends between the first burr 641A and the second burr 641B can be referred to as the first arch-shaped path.

[0133]

[0131] The first arched path of the first capillary bridge between the first bar 641A and the second bar 641B may curve radially inward between the first bar 641A and the second bar 641B. In other words, when the capillary bridge between the first bar 641A and the second bar 641B is viewed from a position radially outward of the first bar 641A and the second bar 641B, the shape of the capillary bridge may appear concave. In other words, the midpoint of the first arched path may be located radially inward of the first bar 641A and the second bar 641B. The midpoint of the first arched path may be a point that bisects the first arched path.

[0134]

[0132] The radially outward edge of the capillary bridge may extend along a second arched path, and the radially inward edge of the capillary bridge may extend along a third arched path. The degree of curvature of the second arched path may be greater than the degree of curvature of the third arched path. The degree of curvature is inversely proportional to the radius of curvature. In some embodiments, the second and third arched paths may be circular or elliptical arched paths, or approximate them. In such embodiments, the radius of the third arched path (r3) may be greater than the radius of the second arched path (r2). In the context of arched paths, the terms “radially inward” and “radially outward” are used as in the remainder of this disclosure. That is, the terms “radially inward” and “radially outward” are used to refer to the position of the arched path relative to the center of the substrate support 600. Generally, the first arched path may represent the overall shape of the capillary bridge between adjacent bars 641A and 641B, while the second and third arched paths represent the inner and outer edges of the capillary bridge. Therefore, the first arched path may be positioned between the second and third arched paths.

[0135]

[0133] The formation of a first capillary bridge between the first bar 641A and the second bar 641B can increase the time required for the upper surfaces of the first bar 641A and the second bar 641B to dry completely, for example, to about 20 seconds. Therefore, the formation of a capillary bridge is desirable because it reduces the risk of the upper surfaces of the bars drying out completely during critical periods. As a result, the coefficient of friction between the upper surfaces of the bars and the underside of the substrate W can remain substantially constant during critical periods. Thus, as described above, overlay errors (specifically, overlay errors arising from in-plane deformation of the substrate W) can be reduced.

[0136]

[0134] In some cases, capillary bridges may form spontaneously (i.e., without external influence). However, whether or not capillary bridges form between adjacent burrs is inconsistent and unpredictable (spatially and temporally). For example, in some cases, capillary bridges may form spontaneously between some burrs (e.g., between the first burr 641A and the second burr 641B) but not between other burrs (e.g., between the second burr 641B and the third burr 641C). In some cases, capillary bridges may form between burrs 641 when the immersion liquid is supplied to the extraction trough 630 at a first time, but not when the immersion liquid is supplied to the extraction trough 630 at a second time (the first and second times refer to any time when the immersion liquid is supplied to the extraction trough 630). Whether or not capillary bridges form spontaneously may depend on the surface properties of the substrate support 600 between the burrs.

[0137]

[0135] In order to improve (spatial and temporal) the consistency of capillary bridging between the burrs 641 in the extraction trough 630, one or more bridging features may be provided on the substrate support 600. A bridging feature may be any feature provided on or defined by the substrate support 600 that facilitates the formation of capillary bridging between adjacent burrs. A bridging feature may extend between adjacent burrs in the extraction trough 630. For example, a first bridging feature may be between a first burr 641A and a second burr 641B, and a second bridging feature may be between a second burr 641B and a third burr 641C. Specific examples of such bridging features are illustrated in Figures 18A to 20C.

[0138]

[0136] A bridging feature (for example, the location and shape of the bridging feature) can follow a path along which capillary bridging is naturally formed. That is, a bridging feature can follow an arched path between adjacent burrs. For example, a first bridging feature formed between a first burr 641A and a second burr 641B can follow an arched path between the first burr 641A and the second burr 641B. The arched path between the first burr 641A and the second burr 641B along which the first bridging feature extends can be referred to as the first arched path of the first bridging feature.

[0139]

[0137] The first arched path of the first bridge feature between the first crowbar 641A and the second crowbar 641B may curve radially inward between the first crowbar 641A and the second crowbar 641B. In other words, when the bridge feature between the first crowbar 641A and the second crowbar 641B is viewed from a position radially outward of the first crowbar 641A and the second crowbar 641B, the first bridge feature may appear concave. In other words, the midpoint of the first arched path of the first bridge feature may be located radially inward of the first crowbar 641A and the second crowbar 641B.

[0140]

[0138] The radially outward edge of the bridge feature may extend along the second arched path, and the radially inward edge of the bridge feature may extend along the third arched path. Similar to the first arched path, the midpoints of the second and third arched paths of the first bridge feature may be located radially inward of the first crowbar 641A and the second crowbar 641B. The degree of curvature of the second arched path may be greater than the degree of curvature of the third arched path.

[0141]

[0139] Figures 18A to 18C illustrate one embodiment of a substrate support 600 having bridging features 6501AB and 6501BC. Figure 18A shows a circumferential cross-sectional view of the substrate support 600 having bridging features 6501AB and 6501BC. The cutting plane of the cross-sectional view passes through the ring of the radially outermost crowbar 641 in the extraction trough 630. Figure 18B shows the extraction trough 630 of the substrate support 600 shown in Figure 18A. Figure 18C shows a plan view of the substrate support 600 shown in Figure 18A.

[0142]

[0140] In the embodiments shown in Figures 18A to 18C, the crosslinking features 6501AB and 6501BC are recesses formed on the upper surface 625 of the substrate support 600, and each recess extends between two or more support members or burrs. For example, the first crosslinking feature 6501AB (which is a recess in the embodiments shown in Figures 18A to 18C) may extend between the first burr 641A and the second burr 641B, and the second crosslinking feature 6501BC (which is a recess in the embodiments shown in Figures 18A to 18C) may extend between the second burr 641B and the second burr 641C. During operation of the lithography apparatus, the immersion liquid collects in the recesses, which can promote the formation of capillary crosslinks.

[0143]

[0141] The recesses may extend between adjacent burrs and around adjacent burrs. For example, the recess corresponding to the first bridging feature 6501AB may extend between the first burr 641A and the second burr 641B, as well as around the first burr 641A and around the second burr 641B. In other words, the burrs may be arranged within the recesses corresponding to the bridging features. The immersion liquid collected within the first bridging feature 6501AB may move to the upper surfaces of the first burr 641A and the second burr 641B by capillary action.

[0144]

[0142] The recesses corresponding to different bridge features 6501AB and 6501BC may be connected to each other. For example, the recess corresponding to the first bridge feature 6501AB may be connected to the recess corresponding to the second bridge features 6501AB and BC. For example, in the embodiment shown in Figures 18A to 18C, a single recess forms the first bridge feature 6501AB and the second bridge feature 6501BC, and the first crowbar 641A, the second crowbar 641B, and the third crowbar 641C are arranged within that single recess.

[0145]

[0143] In the embodiments shown in Figures 18A to 18C, the second arched path may follow the radially outer edge of the recess corresponding to the first bridging feature 6501AB, and the third arched path may follow the radially inner edge of the recess corresponding to the first bridging feature 6501AB.

[0146]

[0144] Figures 19A to 19C illustrate another embodiment of the substrate support 600 having bridging features 6502AB and 6502BC. Figure 19A shows a circumferential cross-sectional view of the substrate support 600 having bridging features 6502AB and 6502BC. The cutting plane of the cross-sectional view passes through the radially outermost crowbar ring in the extraction trough 630. Figure 19B shows the extraction trough 630 of the substrate support 600 shown in Figure 19A. Figure 19C shows a plan view of the substrate support 600 shown in Figure 19A.

[0147]

[0145] In the embodiments shown in Figures 19A to 19C, the bridging feature is an elongated projection. The elongated projection may extend between two or more support members or burrs. For example, the first bridging feature 6501AB (which is an elongated projection in the embodiments shown in Figures 19A to 19C) may extend between the first burr 641A and the second burr 641B, and the second bridging feature 6501BC (which is an elongated projection in the embodiments shown in Figures 19A to 19C) may extend between the second burr 641B and the second burr 641C.

[0148]

[0146] The elongated projections may be referred to as ridges, for example, ridges extending between adjacent burs. The elongated projections may protrude from the upper surface 625 of the substrate support 600. For example, the elongated projections may protrude upward from the upper surface 625 of the substrate support 600. During the operation of the lithography apparatus, the immersion fluid adheres to the surface of the elongated projections, thereby promoting the formation of capillary crosslinks.

[0149]

[0147] In the embodiments shown in Figures 19A to 19C, the second arch-shaped path may follow the radial outer surface of the elongated projection corresponding to the first bridging feature 6501AB, and the third arch-shaped path may follow the radial inner surface of the elongated projection corresponding to the first bridging feature 6501AB.

[0150]

[0148] Figures 20A to 20C illustrate another embodiment of the substrate support 600 having bridging features 6503AB and 6503BC. Figure 20A shows a circumferential cross-sectional view of the substrate support 600 having bridging features 6503AB and 6503BC. The cutting plane of the cross-sectional view passes through the ring of the radially outermost crowbar 641 in the extraction trough 630. Figure 20B shows the extraction trough 630 of the substrate support 600 shown in Figure 20A. Figure 20C shows a plan view of the substrate support 600 shown in Figure 20A.

[0151]

[0149] In the embodiments illustrated in Figures 20A to 20C, the crosslinking feature is a reservoir. The reservoir extends between two or more adjacent burrs. The reservoir is formed by a wall protruding from the upper surface 625 of the substrate support 600. The reservoir may extend between two or more support members or burrs. For example, the first crosslinking feature 6501AB (which is a reservoir in the embodiments illustrated in Figures 20A to 20C) may extend between the first burr 641A and the second burr 641B, and the second crosslinking feature 6501BC (which is a reservoir in the embodiments illustrated in Figures 19A to 19C) may extend between the second burr 641B and the second burr 641C. During operation of the lithography apparatus, the immersion liquid is collected in the reservoir, which can thus facilitate the formation of capillary crosslinks.

[0152]

[0150] In the embodiments illustrated in Figures 20A to 20C, the second arched path may follow the radially outward edge of the reservoir corresponding to the first bridge feature 6501AB (i.e., the inner surface of the wall defining the radially outward boundary of the reservoir), and the third arched path may follow the radially inward edge of the reservoir corresponding to the first bridge feature 6501AB (i.e., the inner surface of the wall defining the radially inward boundary of the reservoir). In this context, the inner surface of the wall means the surface of the wall facing the internal volume of the reservoir.

[0153]

[0151] In some embodiments, a substrate support 600 having one or more bridging features may also have any of the other fluid retention features described above. In other embodiments, a substrate support 600 may have one or more bridging features, but may not have any of the other fluid retention features described above. A bridging feature may have features similar to or corresponding to the fluid retention features described above. For example, if a bridging feature is a recess extending between adjacent bars, the depth of the recess may be the same as, for example, the recess 250 shown in Figure 7.

[0154]

[0152] The material on which the substrate supports 200, 300, and 400 are formed may comprise at least one of SiSiC, lithium aluminosilicate glass ceramic (e.g., Zerodur®), cordierite, SiC, or diamond SiSiC. However, the material on which the substrate supports 200, 300, and 400 are formed is not limited to these examples.

[0155]

[0153] In some embodiments, the support bodies of the substrate supports 200, 300, and 400 may be formed of SiSiC. The SiSiC layer may have a diamond-like carbon (DLC) coating thereon. The DLC coating may have a thickness of approximately 100 nm to 1,000 nm, for example, 500 nm. The DLC coating may be less hydrophilic than the SiSiC forming the support body. Therefore, for example, if a plurality of recesses 250 are formed on the upper surface 225 in the extraction trough 230, the surfaces 251 and 252 forming the interior of the recesses 250 may be more hydrophilic than the surrounding surfaces. As a result, the recesses 250 may be able to effectively collect and hold the immersion liquid.

[0156]

[0154] The roughness of the surfaces within the extraction troughs 230, 330, and 430 can also be adapted to retain more immersion liquid within the extraction troughs 230, 330, and 430. For example, the roughness of the upper surfaces 225, 325, and 425 of the extraction troughs 230, 330, and 430 may be increased. Increasing the surface roughness can lead to those surfaces trapping more immersion liquid on the rougher surfaces. Other surface treatments to make the surfaces within the extraction troughs 230, 330, and 430 more hydrophilic may also allow the treated surfaces to retain more immersion liquid.

[0157]

[0155] Surface area roughness (S) of one or more surfaces within the extraction troughs 230, 330, and 430 (for example, the upper surfaces 225, 325, and 425 within the extraction troughs 230, 330, and 430) a) may be greater than 5 μm, preferably greater than 10 μm, preferably greater than 30 μm, and preferably greater than 50 μm. In general, the roughness may be large enough so that the surfaces within the extraction troughs 230, 330, and 430 can retain fluid over the specific periods described above. Surface area roughness (S a Roughness can be a measure of the average distance between the height of a point on the surface and the average height of the surface. The value of roughness can be determined using white light interferometry.

[0158]

[0156] The surface roughness within the extraction troughs 230, 330, and 430 can be increased by any suitable method. This method may involve selecting an alternative manufacturing process that naturally brings about higher surface roughness when forming the surfaces of the extraction troughs 230, 330, and 430. Additionally or alternatively, a texturing process may be performed on the surfaces within the extraction troughs 230, 330, and 430 after they have been formed. The texturing process may comprise polishing or sandblasting.

[0159]

[0157] Instead of adapting the surface roughness within the extraction troughs 230, 330, and 430, a hydrophilic coating (not shown) may be applied to the surfaces within the extraction troughs 230, 330, and 430 to enhance their ability to retain the immersion liquid. The hydrophilic coating may be, for example, a glass-based coating. Additionally or alternatively, the hydrophilic coating may comprise SiO2.

[0160]

[0158] In order to further increase the retention of the immersion liquid in the extraction troughs 230, 330, 430, the circumferential rings of the outermost crowbars 241, 341, 441 located within the extraction troughs 230, 330, 430 can be positioned close enough to the outer circumferential seals 232, 332, 432 so that the capillary effect between the circumferential rings of the outermost crowbars 241, 341, 441 and the outer circumferential seals 232, 332, 432 is more significant than the pulling of the immersion liquid by the extraction openings 217, 317, 417. As a result, the immersion liquid can collect in the space between the circumferential rings of the outermost crowbars 241, 341, 441 and the outer circumferential seals 232, 332, 432. This may further allow the substrate supports 200, 300, and 400 to retain fluid within the extraction troughs 230, 330, and 430 for longer periods of time.

[0161]

[0159] In another aspect of the present disclosure, a method is provided for reducing asymmetric wear of the burrs 41 of the circumferential ring of the outermost burrs 41b by increasing the uniformity of the presence of immersion fluid in the extraction trough 130 before unloading the substrate W from the substrate support 20. The method comprises using the fluid handling structure IH to provide immersion fluid to the extraction trough 130 after the fluid handling structure IH has moved relative to substantially the entire substrate W (i.e., after exposure of the substrate W has been completed). Specifically, the fluid handling structure IH may provide immersion fluid to the portion of the extraction trough 130 in which the immersion fluid has dried by the time the substrate W is unloaded from the substrate support 20. In this way, the immersion fluid is present throughout the extraction trough 130 when the substrate W is unloaded from the substrate support 20.

[0162]

[0160] Next, a specific example will be given of the case where the lithography apparatus is configured such that the fluid handling structure IH moves relatively over the substrate W, as shown in Figure 4. As explained above, when the fluid handling structure IH moves relatively over the substrate W as shown in Figure 4, at the time when the substrate W is unloaded from the substrate support 20 (i.e., t=t4), the northern part N of the extraction trough 130 is wet (i.e., immersion liquid is present in the northern part N of the extraction trough 130), but the southern part S of the extraction trough 130 is not wet (i.e., immersion liquid is not present in the southern part S of the extraction trough 130). Therefore, this method may include a rewetting step in which the southern part S of the extraction trough 130 is rewetted with immersion liquid after the fluid handling structure IH has moved relatively over substantially the entire substrate W (i.e., t=t3) and before the substrate W is unloaded from the substrate support 20 (i.e., t=t4).

[0163]

[0161] The rewetting step may include moving the fluid handling structure IH relative to the substrate W so that the fluid handling structure IH moves over the southern portion S of the substrate W, and thereby provides the immersion fluid to the southern portion S of the extraction trough 130. By performing this step, the uniformity of the presence of the immersion fluid in the extraction trough 130 is increased between the northern portion N of the extraction trough 130 and the southern portion S of the extraction trough 130. As a result, when the substrate W is unloaded from the substrate support 20, the crowbars 41b in the northern portion N of the extraction trough 130 are worn to the same extent as the crowbars 41b in the southern portion S of the extraction trough 130. Thus, the increase in asymmetric wear of the crowbars 41b is suppressed. It will be understood that the rewetting step may include rewetting any other portion of the extraction trough 130 where the immersion fluid is no longer present by the time the substrate W is unloaded from the substrate support 20.

[0164]

[0162] As described above, implementing the step of re-wetting a portion of the extraction trough 130 may increase the length of time required to process the substrate W. Therefore, implementing the step of re-wetting a portion of the extraction trough 130 may reduce the throughput of the lithography apparatus. However, in some cases, the suppression of asymmetric wear of the bar 41b may be limited to an extent that justifies the impact on throughput.

[0165]

[0163] It will be understood that the method comprising the step of re-wetting a portion of the extraction trough 130 can be implemented for substrate supports 20, 200, 400, 300, 500, and 600 having features described herein (e.g., fluid retention features, bridge features, etc.). However, this is not mandatory, and the method comprising the step of re-wetting a portion of the extraction trough 130 can be successfully implemented for any substrate support 20 having an extraction trough 130.

[0166]

[0164] The present invention may provide a lithography apparatus. The lithography apparatus may have any / all of the other features or components of the lithography apparatus described above. For example, the lithography apparatus may optionally include at least one of the following: a radiation source SO, an illumination system IL, a projection system PS, a substrate support WT, etc.

[0167]

[0165] Specifically, the lithography apparatus may include a projection system PS configured to project a radiation beam B toward a region of the surface of the substrate W. The lithography apparatus may further include substrate supports 300, 400, 500 as described in any of the above embodiments and modifications.

[0168]

[0166] Although this text specifically refers to the use of lithography equipment in the manufacture of ICs, it should be understood that lithography equipment described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, and the like.

[0169]

[0167] Where permitted by context, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented by instructions stored in a machine-readable medium which can be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM), random access memory (RAM), magnetic storage media, optical storage media, flash memory devices, electrical, optical, acoustic or other forms of propagating signals (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Furthermore, firmware, software, routines, and instructions may be described herein as performing specific actions. However, it should be understood that such descriptions are merely for convenience, and that such actions actually result from a computing device, processor, controller, or other device that executes the firmware, software, routines, instructions, etc., and that in execution, actuators or other devices may interact with the material world.

[0170]

[0168] Although embodiments of the present invention are referred to in the context of lithography apparatus in this text, embodiments of the present invention may be used in other apparatuses. Embodiments of the present invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus for measuring or processing objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatuses may generally be referred to as lithography tools.

[0171]

[0169] Although the above has specifically referred to the use of embodiments of the present invention in the context of photolithography, it will be understood that the present invention is not limited to photolithography where permitted in the context.

[0172]

[0170] Although specific embodiments of the present invention have been described above, it will be understood that the present invention may be put into practice in ways different from those described. The above description is for illustrative purposes only and is not limiting. Therefore, it will be obvious to those skilled in the art that modifications to the described invention can be made without departing from the claims described later.

Claims

1. A substrate support configured to support a substrate, A support body having a top surface, Multiple support members extending above the aforementioned upper surface, An extraction trough defined by a first circumferential wall and a second circumferential wall, wherein the first circumferential wall and the second circumferential wall extend above the upper surface, The extraction opening formed on the upper surface within the extraction trough, One or more fluid-holding features formed within the extraction trough, defined by the support body, A circuit board support equipped with a board support.

2. The substrate support according to claim 1, wherein one or more fluid-retaining features are configured to prevent the extraction of the fluid collected by the fluid-retaining feature through the extraction opening, and / or the fluid-retaining feature is a reservoir, and / or the fluid-retaining feature is a recess formed on the upper surface, and / or the one or more fluid-retaining features is an array of depressions distributed across the upper surface within the extraction trough.

3. The substrate support according to claim 2, wherein the depth of the fluid-retaining feature is greater than 10 μm, preferably greater than 100 μm, less than 500 μm, preferably less than 200 μm, and even more preferably less than 120 μm, and / or the recess is cylindrical, hemispherical, conical, or cubic, and / or the maximum width of the recess is greater than 10 μm, preferably greater than 100 μm, even more preferably greater than 150 μm, less than 2000 μm, preferably less than 1000 μm, and even more preferably less than 500 μm.

4. The substrate support according to claim 1 or 2, wherein the fluid-retaining feature comprises a plurality of grooves formed on the upper surface, preferably the size of the plurality of grooves is such that the grooves are capillary grooves, and / or preferably the plurality of grooves have a width greater than 50 μm and less than 100 μm, preferably greater than 85 μm and less than 100 μm, and / or preferably one or more grooves extend radially, preferably one or more grooves are distributed circumferentially around the substrate support, and the distance between adjacent grooves in the circumferential direction is greater than 25 μm, preferably greater than 50 μm and less than 150 μm, preferably less than 100 μm, and / or preferably one or more grooves extend circumferentially around the substrate support.

5. The substrate support according to claim 1 or 2, wherein the one or more fluid-retaining features is a trench further comprising an extraction opening wall extending circumferentially around the base of one or more of the plurality of support members or disposed along the circumference of the extraction opening, preferably a single fluid-retaining feature at least partially defined by the extraction opening wall, the first circumferential wall, and the second circumferential wall, and / or preferably a plurality of extraction openings distributed circumferentially along the extraction trough, the substrate support comprising an extraction opening wall for each of the extraction openings, and thus the fluid-retaining feature is defined by the plurality of extraction opening walls, the first circumferential wall, and the second circumferential wall, and / or preferably the height of the extraction opening wall is greater than 10 μm, preferably greater than 100 μm, more preferably greater than 150 μm, less than 2000 μm, preferably less than 1000 μm, and more preferably less than 500 μm.

6. The substrate support according to any one of claims 1 to 5, wherein the fluid-holding features are present in more than 50%, preferably more than 75%, and more preferably more than 85% of the surface area of ​​the upper surface within the extraction trough.

7. The substrate support according to claim 1 or 2, wherein the fluid-retaining feature comprises one or more bridging features, each of which extends between two or more support members, optionally between two or more support members of the circumferential ring of the outermost support member, preferably one or more of the bridging features comprises a recess formed on the upper surface of the substrate support, the recess extends between the two or more support members, or preferably one or more of the bridging features comprises an elongated projection protruding from the upper surface of the substrate support, the elongated projection extends between the two or more support members, or preferably one or more of the bridging features comprises a reservoir extending between the two or more support members, the reservoir being formed by a wall protruding from the upper surface of the substrate support.

8. The substrate support according to claim 7, wherein the bridging feature extends along a first arched path between a first support member and a second support member, preferably the midpoint of the first arched path is located radially inward of the first and second support members, and / or the radially outward edge of the bridging feature extends along a second arched path, and the radially inward edge of the bridging feature extends along a third arched path, and the degree of curvature of the second arched path is greater than the degree of curvature of the third arched path.

9. The second circumferential wall is located radially outside the first circumferential wall, and the radial distance between one or more radially outermost support members and the second circumferential wall is less than 500 μm, preferably less than 250 μm, more preferably less than 200 μm, greater than 10 μm, preferably greater than 50 μm, preferably greater than 100 μm, and / or comprises a plurality of extraction openings distributed circumferentially along the extraction trough, optionally the plurality of extraction openings being uniformly distributed along the extraction trough, preferably the number of extraction openings being greater than 10, preferably greater than 50, and more preferably greater than 75. The substrate support according to any one of claims 1 to 8, wherein the number of extractors is more than, more preferably more than 100, less than 1000, preferably less than 500, more preferably less than 150, and / or preferably the distance between adjacent extractors is less than 90 mm, preferably less than 20 mm, more preferably less than 10 mm, greater than 2 mm, preferably greater than 6 mm, and / or preferably the number of support members between adjacent extractors in the extractor trough is less than 50, preferably less than 10, more preferably 6 or less, more than 1, preferably more than 2, more preferably 4 or more.

10. The surface area of ​​the upper surface of the support member in the extraction trough that is in direct contact with the lower side of the substrate is greater than 20% of the nominal area of ​​the upper surface of the support member, preferably greater than 30% of the nominal area of ​​the upper surface of the support member, more preferably greater than 40% of the nominal area of ​​the upper surface of the support member, and / or the lowest horizontal plane of the extraction trough is the upper surface of the substrate support, and therefore substantially the entire extraction trough is above the upper surface, and / or the plurality of support members The distal end is configured to support the bottom surface of the substrate, and / or the first circumferential wall and the second circumferential wall are less than the height of the plurality of support members so as to form at least a partial seal with the bottom surface of the substrate when the substrate is supported by the substrate support, and / or the substrate support is formed of at least one of SiSiC, lithium aluminosilicate glass ceramic, Zerodur, cordierite, SiC, or diamond SiSiC, the substrate support according to any one of claims 1 to 9.

11. A lithography apparatus including a substrate support according to any one of claims 1 to 10.

12. A method for manufacturing a substrate support according to any one of claims 1 to 10, comprising forming one or more recesses by removing material from the upper surface using laser structuring.

13. A method for manufacturing a device, comprising supporting a substrate on a substrate support according to any one of claims 1 to 10.

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