Substrate support and lithographic apparatus

Abstract

A substrate support configured to support a substrate in a lithographic apparatus, comprising: a first circumferential wall (31) having a first height; a first drain (12) radially outward of the first circumferential wall and configured to draw fluid; a second circumferential wall (32) having a second height and radially outward of the first opening; a second drain (119) radially outward of the second circumferential wall and configured to draw fluid; a flow limiting device (33) having a third height and radially outward of the second opening; and a third drain (10) radially outward of the flow restricting device and the substrate and configured to draw the fluid; wherein the first opening, the second opening, and the third opening are distributed around a perimeter of the substrate support; and the third height is less than the first height and the second height.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to EP application 22206863.7, filed on November 11, 2022, which is incorporated herein by reference in its entirety. Technical field

[0003] The present invention relates to a substrate support configured to support a substrate in a lithographic apparatus, a lithographic apparatus comprising the substrate support, and a method of manufacturing a device using the substrate support. Background art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern onto a substrate. For example, a lithographic apparatus can be used to manufacture integrated circuits (ICs). For example, a lithographic apparatus projects a pattern of a patterning device (e.g., a mask), often also referred to as a “design layout” or “design,” onto a layer of radiation - sensitive material (resist) disposed on a substrate (e.g., a wafer). Known lithographic apparatuses include: so - called steppers, in which each target portion is irradiated by exposing the entire pattern at once to the target portion; and so - called scanners, in which each target portion is irradiated by scanning the pattern via a radiation beam in a given direction (the “scanning” direction) while synchronously scanning the substrate parallel or anti - parallel to this direction.

[0005] With the continuous progress of the semiconductor manufacturing process, the size of circuit elements has been continuously decreasing, and the number of functional elements (such as transistors) per device has been steadily increasing for decades, following a trend commonly known as “Moore's Law.” To keep up with Moore's Law, the semiconductor industry has been pursuing technologies capable of creating ever - smaller features. To project a pattern onto a substrate, a lithographic apparatus can use electromagnetic radiation. The wavelength of this radiation determines the minimum size of the features patterned on the substrate. Currently used typical wavelengths are 365 nanometers (i - line), 248 nanometers, 193 nanometers, and 13.5 nanometers.

[0006] Further improvement in the resolution of smaller features can be achieved by providing an immersion fluid having a relatively high refractive index (such as water) on the substrate during exposure. The effect of the immersion fluid is to enable imaging of smaller features because the exposure radiation will have a shorter wavelength in the fluid compared to in a gas. The effect of the immersion fluid can also be regarded as increasing the effective numerical aperture (NA) of the system and also increasing the depth of focus.

[0007] The immersion fluid can be confined by a fluid handling structure to a local region between the projection system of the lithographic apparatus and the substrate. Summary of the invention

[0008] During semiconductor manufacturing, a substrate is supported on a substrate support. Specifically, the substrate is supported on a plurality of protrusions protruding from the surface of the substrate support. A backside coating is typically provided on the surface of the substrate that contacts the protrusions. The backside coating can be used to control the friction between the substrate and the protrusions and / or assist in the dicing and packaging processes after manufacturing the device. The backside coating can have a variable thickness near the edge of the substrate, resulting in a change in the size of the gap between the wall for controlling fluid flow on the substrate support and the backside of the substrate. The change in the size of this gap results in a change in the time taken to remove the immersion liquid from beneath the edge of the substrate. This in turn results in a change in the thermal load (due to evaporative cooling) on the substrate and thus causes an overlay error. Therefore, it is desirable to increase the speed and consistency of removing the immersion liquid from beneath the edge of the substrate.

[0009] According to the present invention, there is provided a substrate support configured to support a substrate in a lithographic apparatus, the substrate support comprising:

[0010] A first circumferential wall having a first height; a first discharge portion that is radially external to the first circumferential wall and is configured to extract fluid; a second circumferential wall having a second height and being radially external to a first opening;

[0011] A second discharge portion that is radially external to the second circumferential wall and is configured to extract fluid;

[0012] A flow limiting device having a third height and being radially external to the second opening; and

[0013] A third discharge portion that is radially external to the flow limiting device and the substrate and is configured to extract fluid;

[0014] Wherein the first opening, the second opening, and the third opening are distributed around the perimeter of the substrate support; and

[0015] The third height is less than the first height and the second height.

[0016] According to the present invention, there is also provided a lithographic apparatus comprising a substrate support.

[0017] According to the present invention, there is also provided a method of manufacturing a device using a substrate support.

[0018] Other embodiments, features, and advantages of the present invention, as well as the structure and operation of each embodiment, feature, and advantage of the present invention, are described in detail below with reference to the accompanying drawings. Description of the Drawings

[0019] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which corresponding reference numerals indicate corresponding parts, and in which:

[0020] Figure 1 A schematic overview of a lithographic apparatus is depicted;

[0021] Figure 2 and Figure 3 Two different versions of a fluid handling system for a lithographic projection apparatus are depicted in cross-section;

[0022] Figure 4 A cross-sectional view of a part of a substrate support according to the present invention is depicted;

[0023] Figure 5 A cross-sectional view of the substrate support during extraction of the immersion liquid is depicted; Figure 5 of the substrate support;

[0024] Figure 6 A cross-sectional view of the substrate when extraction of the immersion liquid has stopped in the external discharge section is depicted; Figure 4 of the substrate;

[0025] Figure 7 A cross-sectional view of a variant of the substrate support is depicted; Figure 4 of the substrate support;

[0026] Figure 8 A cross-sectional view of a variant of the substrate support is depicted; Figure 4 of the substrate support; and

[0027] Figure 9 A cross-sectional view of a part of another substrate support is depicted.

[0028] The features shown in the drawings are not necessarily drawn to scale, and the sizes and / or arrangements depicted are not restrictive. It should be understood that the drawings include optional features that may not be necessary for the present invention. In addition, not all features of the apparatus are depicted in each drawing, and the drawings may only show some parts relevant to the description of specific features. Detailed Description

[0029] In this document, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g., having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm).

[0030] As used herein, the terms “reticle”, “mask” or “patterning device” can be broadly interpreted as referring to a general patterning device that can be used to endow an incident radiation beam with a patterned cross-section corresponding to a pattern to be created in a target portion of a substrate. The term “light valve” can also be used in this context. Examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays, in addition to classical masks (transmission or reflection masks, binary masks, phase-shifting masks, hybrid masks, etc.).

[0031] Figure 1 A lithographic apparatus is schematically depicted. The lithographic apparatus includes: an illumination system (also referred to as an illuminator) IL configured to condition a radiation beam B (e.g., UV radiation or DUV radiation); a mask support (e.g., a mask table) MT configured to support a patterning device (e.g., a mask) MA and connected to a first positioning device PM configured to accurately position the patterning device MA according to certain parameters; a substrate support (e.g., a substrate table) WT configured to hold a substrate (e.g., a wafer coated with resist) W and connected to a second positioning device PW configured to accurately position the substrate support WT according to certain parameters; and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., including one or more dies) of the substrate W.

[0032] In operation, the illumination system IL receives the radiation beam B from a radiation source SO, e.g., via a beam delivery system BD. The illumination system IL can include various types of optical components for directing, shaping, and / or controlling the radiation, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components or any combination thereof. The illuminator IL can be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in the plane of the patterning device MA in its cross-section.

[0033] As used herein, the term “projection system” PS should be broadly interpreted as encompassing various types of projection systems, including refractive, reflective, refractive-reflective, anamorphic, magnetic, electromagnetic, and / or electrostatic optical systems or any combination thereof, depending on the exposure radiation used, and / or other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein can be considered synonymous with the more general term “projection system” PS.

[0034] The lithographic apparatus belongs to the type in which at least a portion of the substrate W can be covered by an immersion liquid (e.g., water) having a relatively high refractive index so as to fill the immersion space 11 between the projection system PS and the substrate W, which is also referred to as immersion lithography. More information about immersion techniques is given in US6,952,253, which is incorporated herein by reference.

[0035] The lithographic apparatus can be of the type having two or more substrate supports WT (also known as "dual platforms"). In such a "multi-platform" machine, the substrate supports WT can be used in parallel, and / or the steps of preparing the substrate W for a subsequent exposure of the substrate W located on one of the substrate supports WT can be carried out while another substrate W on another substrate support WT is being used for exposing a pattern on another substrate W.

[0036] In addition to the substrate support WT, the lithographic apparatus can include a measurement platform (not depicted in the figures). The measurement platform is arranged to hold sensors and / or cleaning devices. The sensors can be arranged to measure properties of the projection system PS or the radiation beam B. The measurement platform can hold multiple sensors. The cleaning device can be arranged to clean a part of the lithographic apparatus, such as a part of the projection system PS or a part of the system providing the immersion liquid. The measurement platform can move under the projection system PS when the substrate support WT is away from the projection system PS.

[0037] In operation, the radiation beam B is incident on a patterning device (e.g., mask MA) held on a mask support MT and is patterned by the pattern (design layout) present on the patterning device MA. After passing through the mask MA, the radiation beam B is transmitted through the projection system PS, which focuses the beam onto a target portion C of the substrate W. By means of the second positioning device PW and the position measurement system IF, the substrate support WT can be accurately moved, for example, to position different target portions C in the path of the radiation beam B in a focused and aligned position. Similarly, the first positioning device PM and possibly another position sensor (the other position sensor is not explicitly depicted in Figure 1 are used to accurately position the patterning device MA relative to the path of the radiation beam B. Mask alignment marks M1, M2 and substrate alignment marks P1, P2 can be used to align the patterning device MA and the substrate W. Although the substrate alignment marks P1, P2 as illustrated occupy dedicated target portions, the substrate alignment marks P1, P2 can be located in the space between the target portions. When the substrate alignment marks P1, P2 are located between the target portions C, the substrate alignment marks P1, P2 are referred to as scribe alignment marks.

[0038] To clearly illustrate the present invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes, namely, the x-axis, the y-axis, and the z-axis. Each of the three axes is orthogonal to the other two axes. A rotation about the x-axis is referred to as an Rx rotation. A rotation about the y-axis is referred to as an Ry rotation. A rotation about the z-axis is referred to as an Rz rotation. The x-axis and the y-axis define a horizontal plane, while the z-axis is in the vertical direction. The Cartesian coordinate system does not limit the present invention but is only used for illustration. Alternatively, another coordinate system (such as a cylindrical coordinate system) can be used to illustrate the present invention. The orientation of the Cartesian coordinate system can be different, for example, such that the z-axis has a component along the horizontal plane.

[0039] Immersion technology has been introduced into lithography systems to achieve improved resolution of smaller features. In an immersion lithography apparatus, a liquid layer of an immersion liquid having a relatively high refractive index is interposed in the immersion space 11 between the projection system PS of the apparatus (through which a patterned beam is projected onto a substrate W) and the substrate W. The immersion liquid covers at least a portion of the substrate W under the final element of the projection system PS. Thus, at least a portion of the substrate W that is undergoing exposure is immersed in the immersion liquid.

[0040] In commercial immersion lithography, the immersion liquid is water. Generally, the water is highly purified distilled water, such as ultrapure water (UPW) commonly used in semiconductor fabrication plants. In an immersion system, the UPW is often purified, and the UPW may undergo additional processing steps before being supplied as the immersion liquid to the immersion space 11. In addition to water, other liquids having a high refractive index can also be used as the immersion liquid, for example: hydrocarbons (such as fluorocarbons); and / or aqueous solutions. Furthermore, it has been envisioned to use other fluids than liquids for immersion lithography.

[0041] In this specification, localized immersion will be mentioned in the description, in which the immersion liquid is restricted in use to the immersion space 11 between the final element and the surface facing the final element. The facing surface is the surface of the substrate W, or the surface of the support platform (or substrate support WT) that is coplanar with the surface of the substrate W. (Note that references to the surface of the substrate W hereinafter also refer, additionally or alternatively, to the surface of the substrate support WT, unless otherwise explicitly stated, and vice versa). The fluid handling structure IH between the projection system PS and the substrate support WT serves to confine the immersion liquid to the immersion space 11. The immersion space 11 filled with the immersion liquid is smaller in area than the top surface of the substrate W, and the immersion space 11 remains substantially stationary relative to the projection system PS while the substrate W and the substrate support WT move therebelow.

[0042] Other immersion systems have been envisioned, such as non - restrictive immersion systems (so - called "fully wet" immersion systems) and bathtub - type immersion systems. In non - restrictive immersion systems, the immersion liquid covers an area larger than the surface under the final element. The liquid outside the immersion space 11 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 coplanar with the substrate W. In bathtub - type systems, the substrate W is completely immersed in a bath of immersion liquid.

[0043] The fluid handling structure IH is a structure that supplies immersion liquid to the immersion space 11, removes immersion liquid from the immersion space 11, and thus confines the immersion liquid to the immersion space 11. The fluid handling structure IH includes a plurality of features as part of the fluid supply system. The arrangement disclosed in PCT patent application WO99 / 49504 is an early fluid handling structure, which includes pipes that supply immersion liquid to the immersion space 11 or recover immersion liquid from the immersion space 11, and the pipes operate depending on the relative movement of the platform under the projection system PS. In the most recent designs, the fluid handling structure extends along at least a portion of the boundary of the immersion space 11 between the final element of the projection system PS and the substrate support WT or the substrate W, so as to partially define the immersion space 11.

[0044] The fluid handling structure IH can have a series of different functions. Each function can be derived from a corresponding feature that enables the fluid handling structure IH to achieve the function. The fluid handling structure IH can be referred to by many different terms, each term referring to a function, such as a barrier member, a sealing member, a fluid supply system, a fluid removal system, a liquid confinement structure, and so on.

[0045] As a barrier member, the fluid handling structure IH is a barrier to the flow of immersion liquid from the immersion space 11. As a liquid confinement structure, the structure confines the immersion liquid to the immersion space 11. As a sealing member, the sealing feature of the fluid handling structure IH forms a seal for confining the immersion liquid to the immersion space 11. The sealing feature can include an additional gas flow (such as an air knife) from an opening in the surface of the sealing member.

[0046] The fluid handling structure IH can supply immersion fluid and is thus a fluid supply system.

[0047] The fluid handling structure IH can at least partially restrict immersion fluid and is thus a fluid restriction system.

[0048] The fluid handling structure IH can provide a barrier to immersion fluid and is thus a barrier member, such as a fluid restriction structure.

[0049] The fluid handling structure IH can create or use a gas flow, for example to assist in controlling the flow and / or position of the immersion fluid.

[0050] The gas flow can form a seal for confining the immersion fluid, and thus, the fluid handling structure IH can be referred to as a sealing member; this sealing member can be a fluid confinement structure.

[0051] An immersion liquid can be used as the immersion fluid. In this case, the fluid handling structure IH can be a liquid handling system. In the context of referring to the foregoing description, references in this paragraph to features defined with respect to the fluid can be understood to include features defined with respect to the liquid.

[0052] A lithographic apparatus has a projection system PS. During exposure of a substrate W, the projection system PS projects a patterned radiation beam onto the substrate W. In order to reach the substrate W, the path of the radiation beam B passes from the projection system PS through an immersion liquid, which is confined between the projection system PS and the substrate W by the fluid handling structure IH. The projection system PS has a lens element that is in contact with the immersion liquid, and this lens element is the last element in the path of the beam. This lens element in contact with the immersion liquid can 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 the final element and above the facing surface.

[0053] As Figure 1 shown, the lithographic apparatus includes a controller 500. The controller 500 is configured to control the substrate table WT.

[0054] Figure 2 A local liquid supply system or fluid handling system is schematically depicted. The liquid supply system is provided with a fluid handling structure IH (or liquid confinement structure) that extends along at least a part of the boundary of a space 11 between the last element of the projection system PS and the support table WT or the substrate W. The fluid handling structure IH is substantially stationary relative to the projection system PS in the XY plane, but there may be some relative movement in the Z direction (the direction of the optical axis). In an example, a seal is formed between the fluid handling structure IH and the surface of the substrate W, and it can be a non-contact seal, such as a gas seal (such a system with a gas seal is disclosed in EP1,420,298) or a liquid seal.

[0055] The fluid handling structure IH at least partially confines the immersion liquid in the space 11 between the last element of the projection system PS and the substrate W. The space 11 is at least partially formed by the fluid handling structure IH located below and surrounding the final element of the projection system PS. The immersion liquid is brought into the space 11 below the projection system PS and within the fluid handling structure IH through one of the liquid openings 13. The immersion liquid can be removed through another liquid opening 13. The immersion liquid can enter the space 11 through at least two liquid openings 13. Which of the liquid openings 13 is used for supplying the immersion liquid and optionally which is used for removing the immersion liquid can depend on the direction of movement of the support table WT.

[0056] The immersion liquid can be confined in the space 11 by a non-contact seal such as a gas seal 16 formed by gas, which is formed between the bottom of the fluid handling structure IH and the surface of the substrate W during use. The gas in the gas seal 16 is supplied under pressure via the inlet 15 into the gap between the fluid handling structure IH and the substrate W. The gas is withdrawn via the outlet 14. The overpressure on the gas inlet 15, the vacuum level on the outlet 14, and the geometry of the gap are arranged such that there is an inward high-speed gas flow that confines the immersion liquid. Such a system is disclosed in US2004 / 0207824, the entire content of which is incorporated herein by reference. In an example, the fluid handling structure IH does not have a gas seal 16.

[0057] Figure 3 is a side cross-sectional view depicting another liquid supply system or fluid handling system. Figure 3 The arrangements shown and described below can be applied to the lithographic apparatus described above and Figure 1 shown. The liquid supply system is provided with a fluid handling structure IH (or liquid confinement structure) that extends along at least a portion of the boundary of the space 11 between the last element of the projection system PS and the support table WT or the substrate W.

[0058] The fluid handling structure IH at least partially confines the immersion liquid in the space 11 between the last element of the projection system PS and the substrate W. The space 11 is at least partially formed by the fluid handling structure IH located below and surrounding the final element of the projection system PS. In an example, the fluid handling structure IH includes a body member 53 and a porous member 33. The porous member 33 is plate-shaped and has a plurality of holes (i.e., openings or orifices). The porous member 33 can be a wire mesh plate, in which many small holes 84 are formed in the mesh. Such a system is disclosed in US2010 / 0045949 A1, the entire content of which is incorporated herein by reference.

[0059] The main member 53 includes a supply port 72 capable of supplying immersion liquid to the space 11 and a recovery port 73 capable of recovering the immersion liquid from the space 11. The supply port 72 is connected to a liquid supply device 75 via a passage 74. The liquid supply device 75 can supply the immersion liquid to the supply port 72 through the corresponding passage 74. The recovery port 73 can recover the immersion liquid from the space 11. The recovery port 73 is connected to a liquid recovery device 80 via a passage 79. The liquid recovery device 80 recovers the immersion liquid recovered via the recovery port 73 through the passage 29. A porous member 33 is provided in the recovery port 73. Performing a liquid supply operation using the supply port 72 and a liquid recovery operation using the porous member 33 forms the space 11 between the projection system PS and the fluid handling structure IH on one side and the substrate W on the other side.

[0060] Figure 4 A part of a substrate support for a lithographic apparatus according to the present invention is shown. Figure 4 The arrangement shown and described below can be part of a substrate table WT and can be applied to the lithographic apparatus described above and Figure 1 shown. Figure 4 is a cross-sectional view of the substrate support 20 and the substrate W. In an embodiment, the substrate support 20 includes one or more adjustment channels (not shown) of a thermal regulator. The substrate W is held by a support body 21 (e.g., a protrusion table or a nodule table) including one or more nodules 41 (i.e., protrusions from the surface). The support body 21 is an example of an object holder. Another example of an object holder is a mask holder. A negative pressure applied between the substrate W and the substrate support 20 helps to ensure that the substrate W is firmly held in place.

[0061] A gap 5 exists between the edge of the substrate W and the edge of the recess in the substrate support 20. The edge of the recess in the substrate support 20 can be defined by a cover ring 101, which is optionally separated from the support body 21 of the substrate support 20. The cover ring 101 can be formed as a ring in a plane and surrounds the outer edge of the substrate W. When the edge of the substrate W is imaged or at other times (such as when the substrate W first moves under the projection system PS (as described above)), the immersion space 11 filled with liquid (such as) through the fluid handling structure IH will at least partially pass through the gap 5 between the edge of the substrate W and the edge of the substrate support 20. This may cause the liquid to enter the gap 5 from the immersion space 11.

[0062] If the immersion liquid enters between the substrate W and the support body 21, this may cause problems, especially when unloading the substrate W. To handle the immersion liquid entering the gap 5, two discharge portions 10, 12 are provided at the edge of the substrate W to remove the immersion liquid entering the gap 5. In an embodiment, each of the discharge portions 10, 12 is annular, such that the entire outer periphery of the substrate W is surrounded.

[0063] The main function of the outer discharge portion 10 (which is radially outside the edge of the substrate W / support 21) is to help prevent gas bubbles from entering the immersion space 11 of the liquid in which the fluid handling structure IH is present. Such bubbles can detrimentally affect the imaging of the substrate W. The outer discharge portion 10 is provided to help prevent gas in the gap 5 from escaping into the immersion space 11 in the fluid handling structure IH. If gas does escape into the immersion space 11, this can cause bubbles to float within the immersion space 11. Such bubbles, if in the path of the radiation beam B, can cause imaging errors. The outer discharge portion 10 is configured to remove gas from the gap 5 between the edge of the substrate W and the edge of the recess in the substrate support 20 in which the substrate W is placed. The outer discharge portion 10 mainly extracts gas and only extracts a small amount of the immersion liquid.

[0064] The inner discharge portion 12 (which is radially inside the edge of the substrate W / support 21) is provided to help prevent the liquid that reaches below the substrate W from interfering with the effective release of the substrate W from the substrate support 20 after imaging. Providing the inner discharge portion 12 reduces or eliminates any problems that may occur due to the liquid reaching below the substrate W.

[0065] As Figure 4 shown, in an embodiment, the lithographic apparatus includes a first extraction channel 102 and a second extraction channel 113. The first extraction channel 102 and the second extraction channel 113 may be adapted for two-phase flow through the passageways therein. The first extraction channel 102 may be formed in the support body 21 or in a separate block. The outer discharge portion 10 and the inner discharge portion 12 are each provided with corresponding openings 107, 117. The extraction channels 102, 113 are in fluid communication with the corresponding openings 107, 117 through corresponding passageways 103, 114.

[0066] As Figure 4 shown, the cover ring 101 has an upper surface. This upper surface extends around the perimeter of the substrate W on the support 21. During the use of the lithographic apparatus, the substrate support 20 moves relative to the fluid handling structure IH. During this relative movement, the fluid handling structure IH moves across the gap 5 between the cover ring 101 and the substrate W. In an embodiment, this relative movement is caused by the substrate support 20 moving below the fluid handling structure IH. In an alternative embodiment, this relative movement is caused by the fluid handling structure IH moving above the substrate support 20. In another alternative embodiment, the relative movement is provided by the movement of the substrate support 20 below the fluid handling structure IH and the movement of the fluid handling structure IH above the substrate support 20. In the following description, the movement of the fluid handling structure IH will be used to denote the relative movement of the fluid handling structure IH relative to the substrate support 20.

[0067] The support body 21 includes a plurality of protrusions 41. When the substrate W is supported by the support body 21, the substrate W is in direct contact with the protrusions 41 of the support body 21. The support body 21 is the part of the substrate support 20 that physically supports the lower side of the substrate W. The distal ends of the protrusions 41 define a support plane for supporting the lower side of the substrate W. The lower side of the substrate W is in contact with the distal ends of the protrusions 41. The protrusions 41 are located on the upper side of the support body 21.

[0068] When the substrate W is loaded onto the substrate support 20, the substrate W is first received by a plurality of e-pins (not shown) in their extended positions. Then the e-pins are retracted so that the substrate W descends toward the substrate support 20. When the lower side of the substrate W comes into contact with the plurality of protrusions 41, the e-pins continue to retract so that the substrate W is no longer in contact with the e-pins, and the substrate W is fully supported by the plurality of protrusions 41.

[0069] During the loading process, the gas pressure between the substrate W and the substrate support 20 can be controlled to control the loading process. For example, a relatively high pressure can be established during the loading process to generate an upward force to deform the edge of the substrate W upward. This can reduce or completely eliminate the umbrella-shaped deformation of the substrate W. After the loading is completed, gas can be extracted through one or more fixture openings (not shown) so that a low pressure (a pressure less than the ambient pressure) is established below the substrate W. Accordingly, a force is applied to the substrate W in the direction toward the substrate support 20 so that the substrate W is clamped to the substrate support 20.

[0070] To unload the substrate W from the substrate support 20 after the exposure of the substrate W is completed, the pressure below the substrate W is gradually increased toward the ambient pressure so that the clamping force applied to the substrate W is reduced. The e-pins (not shown) protrude from their retracted positions. As the e-pins protrude, their distal portions come into contact with the lower side of the substrate W. As the e-pins continue to protrude, the substrate W is lifted off the plurality of protrusions 41.

[0071] As Figure 4 shown, the substrate support 20 further includes a plurality of seals 31, 32. The seals 31, 32 are circumferential walls protruding from the substrate support 20. In this example, there are at least two seals: an inner seal 31 and an outer seal 32 radially outward of the inner seal 31. The inner discharge portion 12 is between the inner seal 31 and the outer seal 32. When the substrate W is supported by the substrate support 20, the top surfaces of the plurality of seals 31, 32 (i.e., the surfaces of the plurality of seals 31, 32 that are substantially parallel to the substrate W and closest to the substrate W) do not contact the lower side of the substrate W. However, the distance between the top surfaces of the plurality of seals 31, 32 and the lower side of the substrate W is such that at least a partial seal is formed between the top surfaces of the seals 31, 32 and the lower side of the substrate W. That is, the plurality of seals 31, 32 inhibit, but do not completely prevent, the flow of fluid.

[0072] The distance between the top surfaces of the seals 31, 32 and the lower side of the substrate W is preferably less than 10 μm, and more preferably less than 5 μm, and preferably greater than 1 μm, and more preferably greater than 3 μm. In an embodiment, for each of the seals 31, 32, the distance between the top surface of the seal 31, 32 and the lower side of the substrate W may be different.

[0073] For the substrate support 20 configured to support a substrate W having a diameter of 300 mm, the following dimensions are preferred. For a substrate W having a diameter other than 300 mm, the dimensions may be similar or scaled according to the diameter of the substrate W. The distance between the outer seal 32 and the peripheral edge of the substrate W is preferably less than 5 mm, more preferably less than 3 mm, and more preferably less than 2.5 mm. The distance between the outer seal 32 and the peripheral edge of the substrate W is preferably greater than 1 mm.

[0074] The width of each of the plurality of seals 31, 32 (i.e., the distance in the radial direction between the inner peripheral edge and the outer peripheral edge of the seal) is preferably greater than 0.1 mm, and more preferably greater than 0.2 mm. The width of each of the plurality of seals 31, 32 is preferably less than 1 mm, and more preferably less than 0.6 mm.

[0075] The width of each of the plurality of seals 31, 32 may be different. The width of one of the seals 31, 32 may be made larger to ensure that the ring of the protrusion 42 can be located on the top surface (not shown) of the seal 32. In an embodiment, the width of the outer seal 32 is greater than the width of the inner seal 31. Preferably, the width of the outer seal 32 is greater than 0.4 mm and less than 0.6 mm, such as 0.5 mm. The width of the inner seal 31 is preferably less than 0.3 mm and greater than 0.2 mm, such as 0.25 mm.

[0076] In an embodiment, the plurality of protrusions 41 are arranged in a circumferential ring. The radially outermost circumferential ring of the protrusion 42 may be located between the inner seal 31 and the outer seal 32. When the substrate support 20 supports the substrate W, it is preferred that the outer circumferential ring of the protrusion 42 remains dry, i.e., does not contact the immersion fluid. This is to prevent wear of the outer circumferential ring of the protrusion 42.

[0077] In an embodiment, when a substrate W with a diameter of 300 mm is clamped onto the substrate support 20, the radially outermost circumferential ring of the protrusions 42 is preferably less than 10 mm from the peripheral edge of the substrate W, more preferably less than 5 mm from the peripheral edge of the substrate W, even more preferably less than 4 mm from the peripheral edge of the substrate W, and even more preferably less than 3.5 mm from the peripheral edge of the substrate W. When a substrate W with a diameter of 300 mm is clamped onto the substrate support 20, the radially outermost circumferential ring of the protrusions 42 is preferably more than 1 mm away from the peripheral edge of the substrate W.

[0078] The diameters of each of the protrusions 41, 42 may be different. For example, each circumferential ring of the protrusions 41, 42 may have a different diameter. The diameters of the protrusions 41, 42 in the circumferential rings may depend on the radial distance from the center of the substrate support 20. This is because the contact stiffness of the protrusions is proportional to the diameter of the protrusions. Therefore, by changing the diameters of the protrusions 41, 42, the amount of deformation at the protrusion - substrate interface can be adjusted. This means that despite the complex pressure distribution on the lower side of the substrate W, the diameters of the protrusions 41, 42 can be controlled to ensure that the substrate W remains within the required flatness tolerance. The required diameter of each ring of the protrusions 41, 42 can be determined by experimental or simulation optimization.

[0079] Preferably, the diameter of the protrusions 42 in the radially outermost circumferential ring (or rings) is between 200 μm and 350 μm, and the diameter of the protrusions 41 in the innermost ring is between 150 μm and 250 μm. More preferably, the diameter of the protrusions 42 in the (multiple) radially outermost circumferential rings is between 250 μm and 330 μm, and the diameter of the protrusions 41 in the other circumferential rings is between 190 μm and 240 μm. Even more preferably, the diameter of the protrusions 42 in the (multiple) radially outermost circumferential rings is between 260 μm and 280 μm (such as 270 μm), and the diameter of the protrusions 41 in the other rings is between 200 μm and 220 μm (such as 210 μm).

[0080] Protrusions with smaller diameters may wear faster, which would mean that the substrate support 20 (or the support body 21) would need to be replaced more frequently. To avoid the protrusions 41, 42 wearing too fast, the diameters of all the protrusions 41, 42 should be greater than 150 μm.

[0081] Other techniques can be used to adjust the stiffness of the protrusions 41, 42, such as changing the material or applying a coating, such as diamond and DLC. However, the substrate W generally has a lower stiffness than the protrusions 41, 42, so the protrusion material or coating will not significantly affect the deformation at the substrate - protrusion interface. Therefore, these techniques are not particularly effective for controlling the flatness of the substrate W.

[0082] In the above-described embodiments, the pitch of the protrusions (the distance between the protrusions 41 and 42) is preferably greater than 0.5 mm, more preferably greater than 1 mm, and even more preferably greater than 1.4 mm. The pitch of the protrusions is preferably less than 3 mm, more preferably less than 2 mm, and even more preferably less than 1.6 mm, such as 1.5 mm.

[0083] The protrusion 41 may have a height of about 150 μm (i.e., the dimension from the surface of the support body 21 to the distal end of the protrusion). However, the protrusion 41 may have any suitable height.

[0084] The material of the substrate support 20 is not particularly limited and may be any suitable material known in the art. Preferably, the substrate support 20 may be made of silicon carbide (SiSiC).

[0085] The manufacture of the substrate support 20 may include standard techniques known in the art. For methods such as electrical discharge machining (EDM), some of the openings may be too small. In such cases, laser drilling may be utilized.

[0086] In an embodiment of the present invention, an intermediate discharge portion 119 is provided outside the outer seal 32 and within the outer discharge portion 10. Desirably, the intermediate discharge portion 119 is inside the outer periphery of the substrate W. A flow limiting device 33 is provided between the intermediate discharge portion 119 and the outer discharge portion 12. The intermediate discharge portion 119 and the flow limiting device 33 work together to increase the pumping rate of the immersion liquid and to make the pumping of the immersion liquid more consistent even when the thickness variation of the back coating on the substrate W causes a change in the size of the gap between the back surface of the substrate W and the upper surface of the substrate support 20.

[0087] The intermediate discharge portion 119 includes an opening 121 in the upper surface of the support body 21, which opening 121 is connected to a source of negative pressure (under pressure), such as a pumping channel 102, via a passage 118. The first pumping channel 102 is desirably connected to a low pressure source in order to effect an efficient pumping of the immersion liquid via the intermediate discharge portion 119 and the outer discharge portion 10.

[0088] The flow limiting device 33 may include a raised portion that supports the main body 21 or a porous member mounted on the main body 21. Desirably, the height of the flow limiting device 33 is less than the height of the inner seal 31 and the outer seal 32, such that the gap between the substrate W and the top of the flow limiting device 33 is greater than the gap between the substrate W and the top surfaces of the inner seal 31 and the outer seal 32. Desirably, the gap between the substrate W and the flow limiting device 33 is at least 10 μm, preferably at least 20 μm, more preferably at least 30 μm. Desirably, the distance between the support plane and the top surface of the flow limiting device 33 is less than 100 μm, preferably less than 70 μm, more preferably less than 50 μm. Desirably, the width of the flow limiting device 33 in the radial direction is at least 0.1 mm, preferably at least 0.25 mm. Desirably, the width of the flow limiting device 33 in the radial direction is less than 2 mm, more desirably less than 0.25 mm. The flow limiting device 33 may have several functions. For example, the flow limiting device 33 can ensure that the extraction flow rate through the intermediate discharge portion 119 is not too high, so as to prevent excessive evaporation and the resulting cooling load that may occur at high gas flow rates. The flow limiting device 33 can help to make the pressure near the intermediate discharge portion 119 more uniform and provide a more uniform extraction of the immersion liquid. The flow limiting device 33 can prevent the situation where only air is extracted and liquid is left in certain positions.

[0089] Desirably, the flow limiting device 33 is the outermost feature of the support main body 21, and the outermost feature is within the outer periphery of the substrate W. In other words, the flow limiting device 33 is a feature of the upper surface of the substrate main body 21 that is within the coverage area of the substrate W and closest to the edge of the substrate W. Therefore, the flow limiting device 33 can be positioned opposite the portion of the back surface of the substrate W where the thickness of the back coating varies the most. On the other hand, the inner seal 31 and the outer seal 32 can be located at positions where the thickness of the back coating of the substrate W is relatively uniform. Since the flow limiting device 33 is relatively wide and the gap between the top of the flow limiting device 33 and the back surface of the substrate W is relatively large compared to the variation in the thickness of the back coating, the effect of the flow limiting device 33 is sufficiently uniform regardless of the variation in the thickness of the back coating of the substrate W. It should be noted that in the outermost portion of the substrate W, the thickness of the back coating can vary between substrates and around the perimeter of the substrate. The thickness of the back coating of the substrate W at the position of the flow limiting device 33 can vary due to changes in the coverage of the back surface of the substrate W. The dimensions of the flow limiting device 33 (especially the height and width of the flow limiting device 33) can be optimized based on simulation or empirical evidence, especially in view of the expected variation in the thickness of the back coating of the substrate W in the outer portion of the substrate W.

[0090] Figure 4 、 5 Figures 5 and 6 illustrate the operation of the substrate support 20 when removing the immersion liquid. Figure 4Depicts the situation when the immersion space 11 containing the immersion liquid is located above the gap 5 between the substrate W and the substrate support 20. The gap 5 and the space below the substrate W outside the internal discharge portion 12 are rapidly filled with the immersion liquid. Since the first extraction channel 102 and the second extraction channel 113 are connected to a negative pressure, the immersion liquid will be extracted through the first extraction channel 102 and the second extraction channel 113. After the immersion space 11 has moved away from above the gap 5, the immersion liquid in the gap 5 and near the external discharge portion 10 is rapidly removed, as Figure 5 depicted in. However, the immersion liquid may still remain near the intermediate discharge portion 119 and the internal discharge portion 12. Therefore, the extraction of the immersion liquid will continue until Figure 6 the situation shown in is reached. As Figure 6 shown, only a thin film of the immersion liquid remains in most of the various conduits and passages of the substrate support 20. If the extraction of the external discharge portion 10 is turned off when exposure is not performed, the immersion liquid may remain in the first extraction channel 102. It is desirable that any remaining thin film of the immersion liquid be minimized in order to minimize the cooling load caused by the evaporation of the immersion liquid. Compared with a similar substrate support lacking the intermediate discharge portion 119 and the flow limiting device 33, in an embodiment of the present invention, the process of extracting the immersion liquid is faster and more consistent.

[0091] The internal discharge portion 12, the intermediate discharge portion 119, and the external discharge portion 10 may include grooves or trenches formed in the upper surface of the support body 21. In each case, the openings 107, 117, 121 through which the immersion liquid is extracted may include a continuous slit or a series of discrete openings around the entire circumference of the body 21. Such discrete openings may include circular holes (which are convenient for manufacturing), or elongated slits (which may provide higher fluid flow).

[0092] Figure 8 Depicts a top plan view of the substrate support 20. As depicted, desirably, the internal discharge portion 12, the intermediate discharge portion 119, and the external discharge portion 10 extend continuously around the perimeter of the support body 21. Any one or all of the internal discharge portion 12, the intermediate discharge portion 119, and the external discharge portion 10 may be segmented into separate sections that can be independently and selectively connected to a negative pressure so that fluid is extracted only from a selected area of the outer periphery of the substrate W. By not extracting fluid from positions where there is no immersion liquid, power consumption can be reduced, and the capacity of the pump that generates the negative pressure can be reduced. In some cases, it may not be necessary to provide the intermediate discharge portion 119 continuously around the outer periphery of the support body 21. For example, if the edge across which the immersion liquid occurs will occur only at certain positions, it may be sufficient to provide the intermediate discharge portion 119 only near the positions where the edge across which the immersion liquid occurs will occur.

[0093] Figure 7 Depiction Figure 4 A variant of the substrate support 21 depicted in. In Figure 7 the arrangement, the middle discharge portion 119 is connected to the middle extraction channel 120 instead of the first extraction portion 102. In this variant, the pressure in the middle extraction channel 120 can be controlled independently of the pressures in the first extraction channel 102 and the second extraction channel 113, thereby providing additional control over the rate of fluid extraction from beneath the substrate W.

[0094] Figure 9 An alternative substrate support 200 is depicted in. The substrate support 200 includes three main parts: a support body 221 that supports the substrate W but has a slightly smaller diameter; a cover ring 211 that provides an upper surface coplanar with the upper surface of the substrate W; and an extraction ring 231 that surrounds the support body 221 and supports the cover ring 211. The cover ring 211 is optionally separated from the extraction ring 231. In the substrate support 200, the functions of supporting the substrate W and removing the immersion liquid are separated between the support body 221 and the extraction ring 231. The support body 221 and the extraction ring 231 can be thermally isolated and / or mechanically isolated from each other by a gap 240. The gap 240 can include a vacuum or a gas. A seal (not shown) can be optionally provided to seal the gap 240.

[0095] The support body 221 has protrusions 41, 42 on its upper surface, as described above with respect to Figures 4 to 7 . Additional protrusions (not shown) can be optionally provided on the extraction ring 231 to support the substrate W. The support body 221 also has the internal seal 31 and the external seal 32 as described above. Gas supply / extraction channels 222, 223 are provided to control the pressure beneath the substrate W, thereby for clamping during operation and controlling the shape of the substrate W during loading and unloading operations. For example, the gas openings can be configured to supply gas during the unloading operation. The extraction ring 231 includes an external discharge portion 232 beneath the cover ring 211 and an internal discharge portion 233 beneath the substrate W. In other words, the internal discharge portion 233 is inside the gap 5 between the substrate W and the cover ring 211, while the external discharge portion 232 is outside the gap 5. The internal discharge portion 233 and the external discharge portion 232 are connected to corresponding extraction channels 234, 235. A flow control structure 236 can be provided near the internal discharge portion 233. Desirably, the pressures in the extraction channels 234 and 235 are arranged to maximize the speed of extracting the immersion fluid from the gap 5 and prevent any immersion fluid from reaching the support body 221.

[0096] The present invention can provide a lithographic apparatus. The lithographic apparatus can have any / all other features or components of the lithographic apparatus described above. For example, the lithographic apparatus can optionally include at least one or more of a source SO, an illumination system IL, a projection system PS, a substrate table WT, etc.

[0097] Specifically, a lithographic apparatus may include a projection system PS configured to project a radiation beam B onto an area of the surface of a substrate W. The lithographic apparatus may also include a substrate support 20 as described in any of the above embodiments and variations.

[0098] Although specific mention may be made herein of the use of a lithographic apparatus in IC manufacture, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like.

[0099] Embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof, as circumstances may allow. Embodiments of the invention may also be implemented by instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine, such as 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 propagated signals (such as carrier waves, infrared signals, digital signals, etc.), and the like. Additionally, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be understood that such descriptions are for convenience only and that such actions are in fact caused by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc., and performing such operations may cause an actuator or other device to interact with the physical world.

[0100] Although embodiments of the invention may be specifically mentioned herein in the context of a lithographic apparatus, embodiments of the invention may be used in other devices. Embodiments of the invention may form part of a mask inspection device, a metrology device, or any device for measuring or processing an object such as a wafer (or other substrate) or a mask (or other patterning device). These devices may be collectively referred to as lithographic tools.

[0101] Although specific mention may have been made above of the use of embodiments of the invention in the context of optical lithography, it should be understood that the invention is not limited to optical lithography as circumstances may allow.

[0102] Although specific embodiments of the present invention have been described above, it should be understood that the present invention can be practiced in other ways different from the described manner. The above description is intended to be illustrative, not restrictive. Therefore, those skilled in the art will understand that the described invention can be modified without departing from the scope of the claims set forth below.

Claims

1. A substrate support configured to support a substrate in a lithographic apparatus, the substrate support comprising: The first circumferential wall (31), the first circumferential wall having a first height; The first discharge portion (12), the first discharge portion being radially outside the first circumferential wall and configured to extract fluid; The second circumferential wall (32), the second circumferential wall having a second height and being located radially outside the first opening; The second discharge portion (119), the second discharge portion being radially outside the second circumferential wall and configured to extract fluid; The flow limiting device (33), the flow limiting device having a third height and being located radially outside the second opening; And The third discharge portion (10), the third discharge portion being radially outside the flow limiting device and the substrate and configured to extract fluid; Wherein the first opening, the second opening and the third opening are distributed around the perimeter of the substrate support; and The third height is less than the first height and the second height.

2. The substrate support according to claim 1, wherein the second discharge portion is distributed around at least 80%, desirably at least 90%, of the perimeter of the substrate support.

3. The substrate support according to claim 1 or 2, wherein the second discharge portion is distributed around the entire portion of the perimeter of the substrate support through which the immersion liquid limited by the liquid handling system of the lithographic apparatus passes.

4. The substrate support according to claim 1, 2 or 3, wherein the flow limiting device extends around the perimeter of the substrate support over the same extent as the second discharge portion.

5. The substrate support according to any one of the preceding claims, further comprising a plurality of protrusions defining a support plane for supporting the substrate, and wherein the distance between the support plane and the top surface of at least one of the first circumferential wall and the second circumferential wall is between 1 μm and 10 μm, preferably between 1 μm and 5 μm, and more preferably between 3 μm and 5 μm, and / or further comprising a plurality of protrusions defining a support plane for supporting the substrate, and wherein the distance between the support plane and the top surface of the flow limiting device is between 10 μm and 100 μm, preferably between 20 μm and 70 μm, and more preferably between 30 μm and 50 μm.

6. The substrate support according to any one of the preceding claims, wherein the flow limiting device comprises a third circumferential wall, and / or wherein the flow limiting device comprises a porous member, and / or wherein the width of the flow limiting device is in the range of 0.1 mm to 2 mm, preferably in the range of 0.25 mm to 0.5 mm.

7. The substrate support according to any one of the preceding claims, wherein the distance between the second discharge portion and the outer edge of the substrate is less than 3 mm.

8. The substrate support according to any one of the preceding claims, wherein the second discharge portion is within the outer perimeter of the substrate.

9. A substrate support according to any one of the preceding claims, wherein the first discharge portion is in fluid communication with a first extraction channel via at least one first passage, the second discharge portion is in fluid communication with a second extraction channel via at least one second passage, and the third discharge portion is in fluid communication with the second extraction channel via at least one third passage, or wherein the first discharge portion is in fluid communication with a first extraction channel via at least one first passage, the second discharge portion is in fluid communication with a second extraction channel via at least one second passage, and the third discharge portion is in fluid communication with a third extraction channel via at least one third passage.

10. The substrate support according to claim 9, wherein the second passage is within the body of the substrate support.

11. A substrate support according to any one of the preceding claims, wherein at least one of the first discharge portion and the second discharge portion comprises: Grooves in the surface of the substrate support facing the substrate and a plurality of openings in the grooves.

12. A substrate support according to any one of the preceding claims, wherein at least one of the first discharge portion and the second discharge portion comprises a first section and a second section.

13. The substrate support according to claim 12, wherein the first section and the second section are selectively connected to the extraction channel separately.

14. A lithographic apparatus comprising a substrate support according to any one of claims 1-13.

15. A method of manufacturing a device using a substrate support according to any one of claims 1-13.

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