Substrate support

Abstract

A substrate support (1) configured to support a substrate. The substrate support comprises a main body (10) having a first side configured to support the substrate, and a second side opposite to the first side. The second side is formed with a plurality of grooves. The plurality of grooves includes a plurality of channels (50) and a plurality of conduits (60). The plurality of channels comprises a first channel (51) and a second channel (52) substantially surrounding the first channel. The plurality of conduits includes at least one first conduit (61) and at least one second conduit (62). The first channel is in fluid communication with the at least one first conduit, and the at least one first conduit extends towards the periphery of the substrate support, and the second channel is in fluid communication with the at least one second conduit, and the at least one second conduit extends towards the periphery of the substrate support.

Description

SUBSTRATE SUPPORTCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 23187490.0 which was filed on 25 July 2023 and which is incorporated herein in its entirety by reference.FIELD

[0002] The present invention relates to a substrate support configured to support a substrate, a substrate support system comprising the substrate support, and a metrology system comprising the substrate support system.BACKGROUND

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (also often referred to as “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).

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements have continually been reduced while the amount of functional elements, such as transistors, per device has been steadily increasing over decades, following a trend commonly referred to as “Moore’s law”. To keep up with Moore’s law the semiconductor industry is chasing technologies that enable to create increasingly smaller features. To project a pattern on a substrate a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features which are patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm and 13.5 nm.

[0005] A lithographic apparatus may include an illumination system for providing a projection beam of radiation, and a support structure for supporting a patterning device. The patterning device may serve to impart the projection beam with a pattern in its cross-section. The apparatus may also include a projection system for projecting the patterned beam onto a target portion of a substrate.

[0006] In a lithographic apparatus, the substrate to be exposed (which may be referred to as a production substrate) may be held on a substrate support (sometimes referred to as a wafer table). The substrate support may be supported on a stage. The substrate support includes a substrate-facing surface of a main body and a stage-facing surface opposite the substrate-facing surface. Grooves may be formed in the stage-facing surface of the main body of the substrate support. Fluid flow through the grooves may be used to provide negative pressure, for example such that the grooves act as vacuum channels, which may aid in securing the substrate support to the stage. There may be a plurality of through holes in the grooves extending to the substrate-facing side of the substratesupport. The plurality of through holes enable the flow to provide negative pressure to aid in securing the substrate to the substrate support.

[0007] There is a desire to more effectively and efficiently secure the substrate to the substrate support. Particularly, it there is a problem that substrates which are warped may be difficult to be secured to the substrate support. This can result in a great amount of flow and pressure being required to secure the substrate and possibly leading to high stress and damage of the substrate.SUMMARY

[0008] An object of the present invention is to provide a substrate support configured to support a substrate.

[0009] In accordance with the present invention is a substrate support configured to support a substrate. The substrate support comprises a main body having a first side configured to support the substrate, and a second side opposite to the first side. The second side is formed with a plurality of grooves. The plurality of grooves comprises a plurality of channels and a plurality of conduits. The plurality of channels comprises a first channel and a second channel substantially surrounding the first channel. The plurality of conduits comprises at least one first conduit and at least one second conduit. The first channel is in fluid communication with the at least one first conduit, and the at least one first conduit extends towards the periphery of the substrate support, and the second channel is in fluid communication with the at least one second conduit, and the at least one second conduit extends towards the periphery of the substrate support.

[0010] In accordance with another aspect of the present invention is a substrate support configured to support a substrate. The substrate support comprises a main body having a first side configured to support the substrate, and a second side opposite to the first side. The main body defines a plurality of through holes and a plurality of inlets. Each through hole extends from the second side to the first side. The plurality of inlets is for connection to one or more positive and / or negative pressure sources. Each through hole is in fluid communication with at least one inlet of the plurality of inlets. One or more through holes is in fluid communication with a corresponding check valve configured to restrict fluid flow through the corresponding through hole when the check valve is in a closed condition and to allow fluid flow through the corresponding through hole when the check valve is in an open condition. The check valve is configured to change from the closed condition to the open condition when a pressure difference between a first pressure, on an upstream side of the check valve, and a second pressure, on a downstream side of the check valve in a direction of fluid flow, is reduced below a predetermined opening pressure difference threshold.

[0011] Also in accordance with the present invention is a substrate support system comprising the substrate support.

[0012] Also in accordance with the present invention, a metrology system comprising the substrate support system.

[0013] Further embodiments, features and advantages of the present invention, as well as the structure and operation of the various embodiments features and advantages of the present invention, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Embodiments of the invention will now be described by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:Figure 1 schematically depicts an overview of a lithographic apparatus;Figure 2 depicts a plan view of a substrate support;Figure 3 depicts a cross-sectional view of the substrate support of Figure 2;Figure 4 depicts a view of the second side of a substrate support including a plurality of grooves including a first channel surrounded by a second channel and a plurality of conduits each extending between one of the channels and a periphery of the substrate support;Figure 5 depicts a view of the second side of a substrate support including a plurality of further channels and corresponding conduits;Figure 6 depicts a view of the second side of a substrate support having a plurality of clamping zones associated with a plurality of grooves;Figure 7 depicts a view of the first side of the substrate support of Figure 6;Figure 8 depicts a cross-sectional view through the substrate support of Figures 6 and 7;Figure 9A depicts a view of the first side of a substrate support having a plurality of seal structures defining a plurality of clamping zones on the first side of the substrate support;Figure 9B depicts a view of the first side of a substrate support having a plurality of seal structures defining a plurality of clamping zones distributed circumferentially around the first side of the substrate support;Figure 10 depicts a cross-sectional view through a substrate support having a different floor levels in different clamping zones on a first side of the substrate support;Figures 11 A-C depict alternative arrangements of a raised region on a first side of the substrate support in a region surrounding a loading pin hole.Figure 12A depicts a cross-sectional view through a substrate support comprising a main body defining a plurality of through holes;Figure 12B depicts a cross-sectional view through the substrate of Figure 12A further comprising check valves to restrict flow through corresponding through holes;Figure 13 depicts a cross-sectional view showing the bending torque applies to a warped substrate by a sample support comprising a plurality of check valves;Figure 14A depicts a check valve in a closed condition (configured to restrict fluid flow);Figure 14B depicts the check valve of Figure 14A in an open condition (configured to allow fluid flow).

[0016] The features shown in the figures are not necessarily to scale, and the size and / or arrangement depicted is not limiting. It will be understood that the figures include optional features which may not be essential to the invention. Furthermore, not all of the features of the substrate support are depicted in each of the figures, and the figures may only show some of the components relevant for describing a particular feature.DETAILED DESCRIPTION

[0017] In the present document, the terms “radiation” and “beam” are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (e.g. with a wavelength of 436, 405, 365, 248, 193, 157, 126 or 13.5 nm).

[0018] The term “reticle”, “mask” or “patterning device” as employed in this text may be broadly interpreted as referring to a generic patterning device that can be used to endow an incoming radiation beam with a patterned cross-section, corresponding to a pattern that is to be created in a target portion of the substrate. The term “light valve” can also be used in this context. Besides the classic mask (transmissive or reflective, binary, phase- shifting, hybrid, etc.), examples of other such patterning devices include a programmable mirror array and a programmable LCD array.

[0019] Figure 1 schematically depicts a lithographic apparatus LA. The lithographic apparatus includes an illumination system (also referred to as illuminator) IL configured to condition a radiation beam B (e.g., EUV radiation or DUV radiation), a mask support (e.g., a mask table) MT constructed to support a patterning device (e.g., a mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA in accordance with certain parameters, a substrate support (e.g., a substrate table or a substrate support) WT constructed to hold a substrate (e.g., a resist coated wafer) W and connected to a second positioner PW configured to accurately position the substrate support WT in accordance with 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 patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W.

[0020] 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 may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, and / or other types of optical components, or any combination thereof, for directing, shaping, and / or controlling radiation. The illuminator IL may be used to condition the radiation beam B to have a desired spatial and angular intensity distribution in its cross section at a plane of the patterning device MA.

[0021] The term “projection system” PS used herein should be broadly interpreted as encompassing various types of projection system, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, as appropriate for the exposure radiation being used, and / or for other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term “projection lens” herein may be considered as synonymous with the more general term “projection system” PS.

[0022] The lithographic apparatus may be of a type wherein at least a portion of the substrate W may be covered by an immersion liquid having a relatively high refractive index, e.g., water, so as to fill an immersion space between the projection system PS and the substrate W - which is also referred to as immersion lithography. More information on immersion techniques is given in US 6,952,253, which is incorporated herein by reference.

[0023] The lithographic apparatus may be of a type having two or more substrate supports WT (also named “dual stage”). In such “multiple stage” machine, the substrate supports WT may be used in parallel, and / or steps in preparation of a subsequent exposure of the substrate W may be carried out on the substrate W located on one of the substrate support WT while another substrate W on the other substrate support WT is being used for exposing a pattern on the other substrate W.

[0024] In addition to the substrate support WT, the lithographic apparatus may comprise a measurement stage (not depicted in Figure 1). The measurement stage is arranged to hold a sensor and / or a cleaning device. The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning device may be arranged to clean part of the lithographic apparatus, for example a part of the projection system PS or a part of a system that provides the immersion liquid. The measurement stage may move beneath the projection system PS when the substrate support WT is away from the projection system PS.

[0025] In operation, the radiation beam B is incident on the patterning device, e.g. mask, MA which is held on the mask support MT, and is patterned by the pattern (design layout) present on patterning device MA. Having traversed the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. With the aid of the second positioner PW and a position measurement system PMS, the substrate support WT can be moved accurately, e.g., so as to position different target portions C in the path of the radiation beam B at a focused and aligned position. Similarly, the first positioner PM and possibly another position sensor (which is not explicitly depicted in Figure 1) may be used to accurately position the patterning device MA with respect to the path of the radiation beam B. Patterning device MA and substrate W may be aligned using mask alignment marks Ml, M2 and substrate alignment marks Pl, P2. Although the substrate alignment marks Pl, P2 as illustrated occupy dedicated target portions, they may be located in spaces between target portions. Substrate alignment marks Pl, P2 are known as scribe-lane alignment marks when these are located between the target portions C.

[0026] In this specification, a Cartesian coordinate system is used. The Cartesian coordinate system has three axis, i.e., an x-axis, a y-axis and a z-axis. Each of the three axes is orthogonal to the other two axes. A rotation around the x-axis is referred to as an Rx-rotation. A rotation around the y-axis is referred to as an Ry -rotation. A rotation around about the z-axis is referred to as an Rz-rotation. The x-axis and the y-axis define a horizontal plane, whereas the z-axis is in a vertical direction. The Cartesian coordinate system is not limiting the invention and is used for clarification only. Instead, another coordinate system, such as a cylindrical coordinate system, may be used to clarify the invention. The orientation of the Cartesian coordinate system may be different, for example, such that the z-axis has a component along the horizontal plane.

[0027] In a lithographic apparatus it is necessary to position with great accuracy the upper surface of a substrate to be exposed in the plane of best focus of the aerial image of the pattern projected by the projection system. To achieve this, the substrate can be held on a substrate support. The surface of the substrate support that supports the substrate can be provided with a plurality of burls whose distal ends can be coplanar in a nominal support plane. The burls, though numerous, may be small in cross- sectional area parallel to the support plane so that the total cross-sectional area of their distal ends is a few percent, e.g. less than 5%, of the surface area of the substrate. The gas pressure in the space between the substrate support and the substrate may be reduced relative to the pressure above the substrate to create a force clamping the substrate to the substrate support.

[0028] A plan view of a substrate support 1 is shown in Figure 2. A partial cross section of the substrate support 1 is depicted in Figure 3. The substrate support 1 may comprise a main body 10 having an upper surface 11. The main body 10 may form a substantial portion of the substrate support 1. The upper surface 11 may be a top surface of the main body 10 when positioned as shown in Figure 3. That is, the upper surface 11 may be top surface in the Z-direction (the vertical direction).

[0029] The substrate support 1 may comprise a plurality of burls (or protrusions) 20 connected to, and protruding from, the upper surface 11 of the main body 10. Optionally, the substrate support 1 may comprise a plurality of burls (or protrusions) 20 connected to, and protruding from, the lower surface (opposite the upper surface 11) of the main body 10. The plurality of burls 20 may have proximal ends 21, which are situated near the main body 10 when in position, and distal ends 22. The distal ends 22 may be at opposite ends of the plurality of burls 20 to the proximal ends 21. That is, the distal ends 22 may be situated at an end of the burl 20 away from the main body 10.

[0030] The plurality of burls 20 may have a central longitudinal axis 23, with the proximal end 21 at one end of the burl 20 and the distal end 22 at the other end of the burl 20 along the central longitudinal axis 23. Thus, each of the plurality of burls 20 may have a central longitudinal axis 23 from the proximal end 21 to the distal end 22.

[0031] The distal ends 22 of the plurality of burls 20 form a support plane for a substrate W. Specifically, the distal ends 22 of the plurality of burls 20 may support a lower surface 31 of thesubstrate W. An upper surface 32 of the substrate W may be a surface opposite the lower surface 31. The upper surface 32 may be a surface which is configured to receive the radiation beam B.

[0032] The support plane may be formed in a substantially flat plane. Consequently, the substrate W can be positioned on the support plane to also be substantially flat, which can reduce errors in the pattern printed onto the substrate W (i.e., defectivity).

[0033] As shown in Figure 3, the plurality of burls 20 may be substantially frusto-conical, i.e. a truncated cone, or may be conical in shape. They may instead be substantially cylindrical. A frustoconical burl 20 may be stronger than a cylindrical burl 20 and thus have less likelihood of breaking. Preferably the plurality of burls 20 have the same shape as each other.

[0034] The plurality of burls 20 may be connected to the upper surface 11 of the main body 10 in any suitable way. The plurality of burls 20 may be separate components which are attached to the upper surface 11 of the main body 10. Alternatively, the plurality of burls 20 may be integral to the main body 10. In other words, the plurality of burls 20 may be formed as protrusions from the upper surface 11 of the main body 10, i.e. the plurality of burls 20 may be formed as a single part with the main body 10.

[0035] The substrate support 1 may be configured to enable fluid to be extracted from between the substrate W supported on the support plane and the upper surface 11. Fluid at the edge of the substrate W may be drawn under the substrate W. As fluid is extracted the pressure beneath the substrate W is reduced relative to pressure above the substrate W, and the edge of the substrate W will lower towards the substrate support 1. The substrate W can be clamped by extracting fluid in the space below the substrate W to provide a reduced relative pressure in the space between the substrate support 1 and the substrate W.

[0036] The main body 10 may comprise at least one extraction opening 12 through which the fluid is extracted. There may be a plurality of extraction openings 12.

[0037] It is beneficial to reduce leakage of fluid into the space between the substrate W and the main body 10 when the substrate W is clamped. Therefore, it may be beneficial to provide a physical boundary positioned near the edge of the substrate support 1. The physical boundary could be formed towards an edge of the main body 10 as shown in Figures 2 and 3. The physical boundary could be formed by a sealing member 40. The sealing member 40 may be a wall type protrusion formed around the edge of the main body 10, for example, around the circumference of the main body 10. The sealing member 40 may be formed to provide a seal between the lower side, e.g., lower surface 31, of the substrate W and the substrate support 1 around the edge of the substrate W. The seal provided by the sealing member 40 need not be a perfect seal but may be a partial seal that reduces but does not eliminate flow of fluid into the space between the substrate support 1 and substrate W.

[0038] The sealing member 40 may surround the plurality of burls 20. The sealing member 40 may protrude from the upper surface 11 of the main body 10. The sealing member 40 may be connected to the main body 10 in any way. The sealing member 40 may be integral with the main body 10.

[0039] A pressure sensor (not depicted in the drawings) may be used to measure the pressure between the substrate W and the upper surface 11 of the main body 10. Various sensors for measuring the pressure in the space below the substrate W are known. For example, a pressure sensor as disclosed in WO 2017 / 137129 Al, which is hereby incorporated by reference in its entirety, provides an example of an appropriate pressure sensor which might be used.

[0040] A flow rate sensor (not depicted in drawings) may be used to measure the flow rate of the fluid extracted via the extraction opening 12. Various sensors for measuring the flow rate from the space below the substrate W are known.

[0041] For the present invention, the exact arrangement of the substrate support 1 is not particularly limited. For example, the exact arrangement of burls 20, sealing member 40 and extraction openings 12 in the substrate support 1 is not particularly limited.

[0042] An arrangement of a substrate support 1 configured to support a substrate W is shown in Figures 4 to 10. The substrate support 1 comprises a main body 10 having a first side configured to support the substrate W. The main body 10 of the substrate support 1 also comprises a second side opposite to the first side. Figures 4 to 6 provide a view looking towards the second side of the substrate supports 1 according to different arrangements. In one arrangement, the first side may be a top side and the second side may be a bottom side of the substrate support 1. In this configuration, with the first side being a top side, the substrate W may rest on the substrate support 1 due to gravity. However, alternative arrangements, in which the substrate support 1 is tilted, such that the first side is not directly above the second side, are possible. Such alternative arrangements may include protrusions, e.g., burls, and / or holding arms on the first side of the substrate support 1 to aid in holding the substrate W in place.

[0043] As shown in Figures 4 to 6, the second side of the substrate support 1 is formed with a plurality of grooves. The plurality of grooves are desirably configured to enable negative and / or positive pressure to be applied to the substrate support 1. The plurality of grooves may be referred to as vacuum channels in situations where a vacuum source is in fluid communication with the plurality of grooves. A negative pressure may be applied to the grooves for example to aid in securing the substrate support 1 to a stage (not shown) on which the substrate support 1 is mounted. Alternatively, or additionally, negative pressure may be applied through the grooves for example to aid in securing a substrate W to the first side of the substrate support 1. Similarly, a positive pressure may be applied by introducing fluid flow through the grooves to aid in removing the substrate W from the substrate support 1.

[0044] It is desirable that the grooves are arranged to enable a desired pressure to be achieved in different regions, for example between the substrate W being supported and the first side of the substrate support 1. In particular, especially for substrates W which are warped, it may be desirable to first secure one area of the substrate W before securing another area of the substrate W. This may aid in achieving a flat, uniform surface for inspection of the substrate W, and / or may reduce stress on thesubstrate W while it is being secured. For example, having a substrate W which is bowl shaped, it may be desirable to first apply a negative pressure to secure the centre, or lowest point, of the substrate W, before applying a negative pressure to a radially outward region of the substrate W to gradually achieve a desired pressure distribution across the substrate W, and possibly to gradually flatten the substrate W. In this way, the substrate W may be secured efficiently, without flow being wasted unnecessarily on regions (such as radially outward regions of a bowl-shaped warped substrate) of the substrate W that are too far (in a Z-direction) from the substrate support 1 to be meaningfully influenced by the flow through the grooves. Furthermore, the substrate W may be secured without being subjected to excessive stress. Alternatively, or additionally, the grooves may be arranged to secure substrates W of different sizes efficiently, without wasting flow on areas of the substrate support 1 which do not correspond to a smaller substrate.

[0045] In the arrangement shown in Figures 4 to 10, the plurality of grooves comprises a plurality of channels 50 and a plurality of conduits 60. The plurality of channels 50 comprises a first channel 51 and a second channel 52. The plurality of conduits 60 comprises at least one first conduit 61 and at least one second conduit 62. The first channel 51 is in fluid communication with the at least one first conduit 61. In other words, a flow to provide a positive or negative pressure may be provided through the first conduit 61 and the first channel 51. Optionally the first channel 51 and the at least one first conduit 61 may form a continuous groove in the second side of the substrate support 1. The second channel 52 is in fluid communication with the at least one second conduit 62. Optionally the second channel 52 and the at least one second conduit 62 may form a continuous groove in the second side of the substrate support 1. In this way, a flow provided through any of the conduits 61, 62 is provided to the corresponding channel 51, 52 with which the conduit 61, 62 is in fluid communication. In this way, the channels 51, 52 may be shaped as desired to achieve a desirable pressure profile across a substrate W, and the conduits 61, 62 may be used as supply grooves to enable flow to / from the channels 51, 52.

[0046] The second channel 52 substantially surrounds the first channel 51. In other words, the second channel 52 extends around the first channel 51. In this way, the first channel 51 may be used to secure a centre of the substrate W to the substrate support 1, and the second channel 52 may be used to secure a radially outward region of the substrate W to the substrate support 1. The second channel 52 may extend at least 90° around the first channel 51. Desirably the second channel 52 extends at least 180° around the first channel 51, more desirably at least 200°, yet more desirably at least 225°, yet more desirably at least 270°, yet more desirably at least 315°.

[0047] One or more, optionally all, conduits 61, 62 of the plurality of conduits 60 extend from a corresponding channel 51, 52 towards the periphery of the substrate support 1. For example, in the arrangements of Figures 4 to 6, the at least one first conduit 61 and the at least one second conduit 62 extend towards the periphery of the substrate support 1. Desirably, the at least one first conduit 61 and the at least one second conduit 62 extend to a position on the substrate support 1 radiallyoutwards of the radially outermost channel of the plurality of channels 50. Optionally one or more of the plurality of conduits 60 extend to an outer area in the outermost half of the substrate support 1 in a radial direction. Desirably, the outer area is in the outermost third of the substrate support 1 in a radial direction. More desirably the outer area is in the outermost quarter of the substrate support 1. Yet more desirably, the outer area is in the outermost fifth of the substrate support 1.

[0048] The second channel 52 desirably extends less than 360° around the first channel 51. For example, the second channel 52 may extend less than or equal to 315° around the first channel 51. In other words, as shown for example in Figure 4 to 6, the second channel 52 may be formed with a discontinuity 5 in a circumferential direction of the substrate support 1. The discontinuity 5 may form a cut region on the second side of the substrate support 1. The cut region is an area, optionally a sector, on the second side that the second channel 52 does not extend across. The at least one first conduit 61 may extends across the cut region. In other words, the discontinuity 5 in the second channel 52 may enable the at least one first conduit 61 to extend from the first channel 51 towards a periphery of the second side of the substrate support 1, without the first conduit 61 cutting across the second channel 52.

[0049] The plurality of channels 50 optionally comprises at least one further channel 53-56 in addition to the first channel 51 and the second channel 52. In the arrangement of Figure 5, the at least one further channel comprises four further channels 53-56. In an alternative arrangement, the at least one further channel may consist of two or three channels. The one or more of the at least one further channels 53-56 and the second channel 52 are optionally concentric with each other, as shown in Figure 5. The further channels 53-56 may enable more areas of the substrate W to be selectively secured to the substrate support 1.

[0050] As shown in Figure 5, the at least one further channel 53-56 surrounds the second channel 52. In other words, each further channel 53-56 is disposed radially outwards of the second channel 52. For example, a first further channel 53 is disposed radially outwards of the second channel 52. Each further channel 53-56 is optionally disposed radially outwards of the preceding channel. As the number of further channels is increased, the extent to which each channel may surround the adjacent, radially inward channel, may be reduced. In other words, a cut region for a further channel 53-56 may be a larger sector than the cut region of the second channel 52. The reduced length, or extent in a circumferential direction, of the further channels 53-56 may be desirable in applications where it is desired to have control over the pressure in discrete regions of the substrate W as it is being secured to the substrate support 1. For example, it may be desirable to control the timing and / or magnitude of application of positive or negative pressure to the substrate W at different circumferential positions, or sectors, of the substrate W. Furthermore, shorter grooves may be less susceptible to leakage than longer grooves, meaning shorter grooves may be less likely to undesirably lose pressure through leakage.

[0051] In the arrangements of Figures 4 to 6, the first channel 51, or the innermost channel of the plurality of channels 50, may take any shape. In other words, the shape of the first channel 51 may be selected based on the application, for example based on the expected warpage of the substrate W to be secured. The second channel 52 has a shape enabling the second channel 52 to substantially surround the first channel 51. For example, the second channel 52 may have a substantially square, hexagonal, star, elliptical or irregular shape. The first channel 51 and / or the second channel 52 optionally has a substantially arc shape, such as that shown in Figures 4 to 6. For example, one or more channels 51- 56 of the plurality of channels 50 may have a substantially arc shape. In other words, one or more channels 51-56 of the plurality of channels 50 may have an incomplete circle shape. In the arrangements of Figures 4 to 6, the first channel 51 and the second channel 52 are concentric with each other. Optionally all of the channels 51-56 of the plurality of channels 50 may be concentric with each other. For example, if it is expected that the substrate W may be warped such that the substrate W has a bowl shape, then it may be desirable for the second channel 52, and any further channels 53-56, to have a concentric arc shape to promote a more uniform pressure distribution around the substrate W.

[0052] In the arrangements of Figures 4 and 5, each conduit 61-66 of the plurality of conduits 60 are straight and extend in a radial direction. In particular, the first conduit 61 extends in a radial direction and the second conduit 62 extends in a radial direction. The first conduit 61 and the second conduit 62 form a non-zero angle. In other words, the first conduit 61 extends in a different direction than the second conduit 61. In an alternative arrangement, one or more conduits 61, 62 of the plurality of conduits 60 may not be straight and / or may not extend in a radial direction. For example, as shown in Figure 6, the conduits 61, 62 each extend in a non-radial direction. In an alternative arrangement, one or more conduits 61-66 of the plurality of conduits 60 may follow a curved path between the respective channel 51-56 and a periphery of the substrate support 1. For example, this may be beneficial in order to reduce a size of a cut region, or discontinuity 5, while providing a conduit 61-66 to connect the corresponding channel 51-56 to a periphery of the substrate support 1.

[0053] The substrate support 1 may comprise a plurality of inlets 70, such as those shown in Figures 4 to 6. Each of the inlets 70 is desirably suitable for connection to one or more positive and / or negative pressure sources. The negative pressure source may be a vacuum source configured to create a vacuum within the plurality of grooves when the plurality of grooves are in fluid communication with the vacuum source via one or more of the inlets 70. As shown in Figures 4 to 6, it is desirable that each conduit 61-66 of the plurality of conduits 60 is in fluid communication with an inlet of the plurality of inlets 70. In this way, the channels 50 may be in fluid communication with the inlets 70 via the respective conduits 60. Each of the plurality of inlets 70 is disposed towards the periphery of the substrate support 1. In other words, one or more, and desirably all, of the plurality of inlets 70 may be disposed in the outer region into which the conduits 61-66 extend.In the arrangements of Figure 4 and 6, the at least one first conduit 61 comprises a plurality of conduits. In this example, the at least one first conduit 61 comprises two conduits. In the arrangement of Figures 4 and 6, the at least one second conduit 62 comprises a plurality of conduits. In these examples, the at least one second conduit 62 comprises two conduits.

[0054] Desirably, as shown in Figures 4 to 6, each conduit 61-66 of the plurality of conduits 60 is in fluid communication with one, desirably only one, channel 51-56 of the plurality of channels 50. For example, in the arrangements of Figures 4 to 6, each conduit of the at least one first conduit 61 is in fluid communication with the first channel 51, and each conduit of the at least one second conduit 62 is in fluid communication with the second channel 52. In this way, each inlet of the plurality of inlets 70 may be in fluid communication with one, desirably only one, respective channel 51-56 of the plurality of channels 50. Desirably, at least one of the plurality of inlets 70 may be connected to a negative pressure source to secure the substrate support 1 to the stage on which the substrate support 1 is mounted. Each channel 51-56 of the plurality of channels 50 is in fluid communication with at least one inlet 70 of the plurality of inlets 70 via at least one conduit 61-66 of the plurality of conduits 60, as shown in Figures 4 to 6. Optionally, as shown in Figures 4 and 6, each channel 51-56 of the plurality of channels 50 is in fluid communication with more than one inlet of the plurality of inlets 70.

[0055] In the arrangements of Figures 4 to 8 and 10, the plurality of grooves may be associated with at least one through hole 12. The at least one through hole 12 extends from the corresponding groove on the second side to the first side of the main body 10 of the substrate support 1. One or more, and desirable each, channel 51-56 of the plurality of channels 50 desirably comprises at least one through hole 12. For example, each of the first channel 51 and the second channel 52 may comprises at least one through hole 12. Additionally, or alternatively, each of the first conduit 61 and the second conduit 62 may also comprise at least one through hole 12. The at least one through hole 12 comprises a plurality of through holes 12. The plurality of through holes 12 may be evenly distributed along the groove. Alternatively, the through holes 12 may be more densely concentrated in certain regions along the length of the groove depending on the application. Similarly, the size and / or cross-sectional shape of the through holes 12 may be selected according to the application. The through holes 12 may be configured to act together with the plurality of grooves to act as vacuum channels. In other words, when negative pressure is supplied through one or more inlets 70, this negative pressure may aid in securing the substrate W to the substrate support 1 via the through holes 12 in the grooves. Similarly, when positive pressure is supplied through one or more inlets 70, this positive pressure may aid in forcing the substrate W away from the substrate support 1 via the through holes 12 in the grooves.

[0056] The plurality of grooves, including the plurality of channels 50 and the plurality of conduits 60, may all be grooves of the same depth, width and cross-sectional shape. Alternatively, the channels 50 may have a different depth and / or width and / or cross-sectional shape than the conduits60. In some arrangements, the depth and / or width and / or cross-sectional shape may be the same for each channel 51-56 of the plurality of channels 50. In other arrangements, different channels 51-56 of the plurality of channels 50 may have different depth and / or width and / or cross-sectional shapes. In some arrangements, the depth and / or width and / or cross-sectional shape may be the same for each conduit 61-66 of the plurality of conduits 60. In other arrangements, different conduits 61-66 of the plurality of conduits 60 may have different depth and / or width and / or cross-sectional shapes.

[0057] The plurality of channels 50 on the second side is associated with a plurality of corresponding clamping zones 510, 520, as shown for example in Figure 6 (which depicts a view of the second side of an arrangement). Each clamping zone 510, 520 desirably corresponds to one or more respective grooves. The one or more respective grooves desirably comprises a channel 51, 52. As shown in the arrangement of Figure 6, the one or more respective grooves may comprise a conduit61, 62. For example, as shown in Figure 6, a first clamping zone 510 on the second side may comprise the first channel 51 and the first conduit 61, and optionally further comprises the at least one inlet 70 to which the first conduit 61 is connected. Similarly, a second clamping zone 520 on the second side may comprise the second channel 52 and the second conduit 62, and optionally further comprises at least one inlet 70 to which the second conduit 62 is connected. In this way, each flow path, between the inlet 70 and the corresponding channel 51, 52, may correspond to a clamping zone 510, 520. In an arrangement having at least one further channel 53-56, one or more of the clamping zones may correspond to two or more respective channels 51-56 of the plurality of channels 50. Each clamping zone 510, 520 on the second side is desirably individually controllable to increase or decrease pressure in that clamping zone 510, 520 on a second side of the substrate support 1. It is desirable for the clamping zones 510, 520 to be controllable such that a different amount of pressure may be applied in different clamping zones 510, 520 and / or the clamping zones 510, 520 may be activated at different times. This control may have the benefit of enabling effective and efficient securing of the substrate support 1 on the second side to the stage on which the substrate support 1 is mounted. Furthermore, if desired, a positive pressure may be applied to one clamping zone 510, 520 while a negative pressure is being applied to a different clamping zone 510, 520.

[0058] In an arrangement such as that of Figures 4 to 7, each channel 51-56 of the plurality of channels 50 may be in fluid communication with an inlet 70 of the plurality of inlets 70 via one or more conduits 61-66 of the plurality of conduits 60. Each inlet 70 may be individually connected to a corresponding dedicated negative and / or positive pressure source such that activation of the pressure source results in a pressure change in the corresponding clamping zone 510, 520. Alternatively, a negative and / or positive pressure source may be shared between a plurality of inlets 70 and a plurality of valves (not shown) may be provided to individually control the input and output to each inlet 70. In this way, the pressure applied in each clamping zone 510, 520 may be individually controllable by controlling the negative and / or positive pressure source and / or the valves.

[0059] The substrate support 1 may be part of a substrate support system. The substrate support system may comprise a stage configured to support the substrate support 1. The substrate support system optionally comprises one or more controllers (not shown) configured to individually control each clamping zone 510, 520. The one or more controllers are desirable configured to activate the respective clamping zones 510, 520 to change a pressure in a region of the second side, and optionally also the first side, corresponding to the respective clamping zones 510, 520. The one or more controllers may comprise a plurality of controllers. Each controller of the plurality of controllers is configured to control a respective clamping zone 510, 520. Alternatively, one controller of the one or more controllers may be configured to individually control a plurality of clamping zones 510, 520.

[0060] The one or more controllers may be configured to control a plurality of positive and / or negative pressure supply sources in fluid communication with the plurality of channels 50 via the plurality of conduits 60. In this arrangement, each positive and / or negative pressure supply source is in fluid communication with one channel of the plurality of channels 50 via at least one conduit of the plurality of conduits 60. Alternatively, or additionally, the one or more controllers may be configured to control a plurality of valves in fluid communication with the plurality of channels 50 via the plurality of conduits 60. In this arrangement, each positive and / or negative pressure supply source may be in fluid communication with two or more channels of the plurality of channels 50 via the plurality of conduits 60 and the individual control of those clamping zones 510, 520 may be provided by controlling the valves.

[0061] Corresponding clamping zones 510, 520, 610, 620 on a first side and a second side of the substrate support 1 may be activated simultaneously. For example, the first clamping zone 510 on the second side will be activated simultaneously with the activation of the first clamping zone 610 on the first side because the first clamping zone 510, 610 on both sides correspond to the first channel 51. In particular, a plurality of through holes 12 (referring to Figure 3) may extend from one or more of the grooves, for example from each of the channels 50, in a clamping zone 510, 520 on the second side to a corresponding clamping zone 610, 620 on the first side. In other words, a first clamping zone 510 on the second side and a first clamping zone 610 on the first side may both be activated by providing flow through the first channel 51 and thus through a plurality of through holes 12 extending from the first channel 51 to the first side of the main body 10 of the substrate support 1. Similarly, a second clamping zone 520 on the second side and a second clamping zone 620 on the first side may both be activated by providing flow through the second channel 52 and thus through a plurality of through holes 12 extending from the second channel 52 to the first side of the main body 10 of the substrate support 1. The pressure in the one or more clamping zones 510, 520 on the second side may not be equal to the pressure in the respective one or more clamping zones 610, 620 on the first side. The pressure in each clamping zone 510, 520, 610, 620 may be dependent on a number of factors, for example including the size, number and distribution of through holes 12, as other geometric features of the substrate support 1 and / or the substrate W. Thus, individually controlling the activation ofclamping zones 510, 520 on the second side results in control of the activation of the corresponding clamping zones 610, 620 on the first side. This control may beneficially be used to provide effective and efficient securing of the substrate W on the first side of the substrate support 1. In other words, a first clamping zone 510, 610 on both the first side and the second side may be activated simultaneously, such that corresponding clamping zones of the first side and the second side (e.g., the first clamping zones 510, 610 of the first and second sides) are controlled collectively. In an alternative arrangement, one or more second side clamping zones (not shown) may be defined on the second side of the substrate support 1. Each second side clamping zone may comprise only grooves in which no through holes 12 are defined. In other words, there may be one or more clamping zones on the second side which are not in fluid communication with a corresponding clamping zone 610, 620 on the first side. These second side clamping zones may be used to aid in securing the substrate support 1 to the stage on which the substrate support 1 is mounted.

[0062] The one or more controllers may be configured to activate the clamping zones 510, 520 sequentially. In other words, the one or more controllers may be configured to activate one clamping zone, such as the first clamping zone 510. The one or more controllers may be configured to then activate another clamping zone, such as the second clamping zone 520, a certain time period after activation of the one clamping zone. The one clamping zone may optionally remain activated when the other clamping zone is activated. In other words, a negative pressure may be applied to the first clamping zone 510 and then, after a certain time period, a negative pressure may also be applied to the second clamping zone 520.

[0063] Additionally, or alternatively, the one or more controllers may be configured to activate the clamping zones 510, 520 based on certain pressure. The certain pressure may comprise the overall pressure across all of the clamping zones 510, 520. Alternatively, the certain pressure may comprise the overall pressure across the clamping zones 510, 520 on the second side or across the clamping zones 610, 620 on the first side. Preferably, the certain pressure may comprise a pressure in each of the clamping zones 510, 520 individually. In other words, the certain pressure may vary between different clamping zones 510, 520. In this arrangement, one or more pressure sensors (not shown) may be provided to measure the pressure in each clamping zone 510, 520. The one or more controllers may be configured to activate one clamping zone and, once a pressure in the one clamping zone exceeds a predetermined pressure threshold, to activate another clamping zone of the plurality of clamping zones 510, 520. For example, the one or more controllers may be configured to activate the first clamping zone 510 and, once a pressure in the first clamping zone 510 exceeds a predetermined pressure threshold, to activate the second clamping zone 520 of the plurality of clamping zones 510, 520. In the arrangement of Figure 6, the second clamping zone 520 is disposed closer to a periphery of the substrate support 1 than the first clamping zone 510. In this way, each substrate W may be effectively and efficiently secured despite variations in factors such as warpage and tilt may vary between different substrates W.

[0064] Additionally, or alternatively, the one or more controllers may be configured to activate the clamping zones 510, 520 based on another parameter. For example, the activation may be based on height of the substrate W above the first side.

[0065] In an embodiment, at least one of the plurality of grooves is optionally surrounded by a seal structure 421, 422 on the second side of the substrate support 1. For example, as shown in Figures 6 and 8, a seal structure 421 may substantially surround the first channel 51 and another seal structure 422 may substantially surround the second channel 52. The seal structure 421, 422 may be the same as the sealing member 40 described above with reference to Figure 3. The seal structure 421, 422 may define and / or separate the clamping zones 510, 520. In other words, a first seal structure 421 may define a first clamping zone 510 of the second side and a second seal 422 may define a second clamping zone 520 of the second side. The first clamping zone 510 may be associated with or comprise the first channel 51, the first conduit 61 and the corresponding inlets 70. The second clamping zone 520 may be associated with or comprise the second channel 52, the second conduit 62 and the corresponding inlets 70. The pressure in the regions defined by each seal structure 421, 422 may be individually controllable. In an embodiment, similar arrangement of seal structure 421, 422 and clamping zones 510, 520 may be applied to the examples shown in Figures 4 and 5.

[0066] The substrate support 1 may comprise a plurality of second protrusions (not shown) extending from the second side of the substrate support 1. The plurality of second protrusions are desirably configured to support the substrate support 1 on a stage. The distal ends of the plurality of second protrusions desirably define a support plane which may be a substantially flat plane. The plurality of second protrusions may be a plurality of burls 20 as described above with reference to Figure 3. The seal structure 421, 422 desirably has a height less than a height of the plurality of second protrusions.

[0067] Figure 7 provides a view looking towards the first side of the substrate support 1 shown in Figure 6. Figure 8 provides a cross-sectional view through section A-A of the substrate support 1 of Figure 7. The arrangement of Figure 7 comprises a plurality of clamping zones 610, 620 on the first side. In the arrangement of Figure 6 and 7, each of the clamping zones 610, 620 on the first side has a footprint overlapping at least one clamping zone 510, 520 on the second side. In the arrangement of Figures 6 and 7, the first clamping zone 510 on the second side has a different area and shape than a first clamping zone 610 on the first side, and the second clamping zone 520 on the second side has a different area and shape than a second clamping zone 620 on the first side. In an alternative arrangement, the area of each clamping zone 610, 620 on the first side may correspond to the area of each clamping zone 510, 520 on the second side. In other words, the clamping zones 610, 620 on the first side may have the same footprint as the corresponding clamping zones 510, 520 on the second side. In the arrangement of Figure 7, each of the clamping zones 610, 620 on the first side is associated with a channel 51, 52 on the second side. In other words, one or more through holes 12 (referring to Figure 3) extend from a channel 51, 52 on the second side to a respective clamping zone610, 620 on the first side. For example, one or more through holes 12 may extend from the first channel 51 on the second side to a first clamping zone 610 on the first side, and one or more through holes 12 may extend from the second channel 52 on the second side to a second clamping zone 620 on the first side. In an alternative arrangement, one or more clamping zones 610, 620 on the first side may be associated with a plurality of channels 51, 52 on the second side.

[0068] At least one of the plurality of grooves is optionally surrounded by a seal structure 411, 412 on the first side, as shown for example in Figure 7 and 8. For example, as shown in Figure 7 and 8, a seal structure 411 on the first side may substantially surround an area corresponding to the footprint of the first channel 51 on the second side and another seal structure 412 on the first side may substantially surround an area corresponding to the footprint of the second channel 52 on the second side. In other words, the seal structure 411, 412 on the first side may surround a plurality of through holes 12 on the first side, wherein each of the through holes 12 extends to the first side from a corresponding groove on the second side. The first seal structure 411 desirably surrounds though holes 12 extending to a groove belonging to the first clamping zone 510 on the second side and a second seal structure 412 desirably surrounds through holes 12 extending to a groove belonging to the second clamping zone 520 on the second side. In this way, by surrounding a plurality of through holes 12 on the first side, the seal structure 411, 412 on the first side surrounds the corresponding grooves. The seal structure 411, 412 may be the same as the sealing member 40 described above with reference to Figure 3. The seal structure 411, 412 may define and / or separate the clamping zones 610, 620. In other words, the pressure in the regions defined by each seal structure 411, 412 may be individually controllable. The seal structures 411, 412, 421, 422 on the first and / or second sides may beneficially improve the efficiency of pressure in the corresponding clamping zone 510, 520, 610, 620 and may reduce the influence of pressure from one clamping zone 510, 520, 610, 620 on adjacent clamping zones 510, 520, 610, 620. In an embodiment, similar arrangement of seal structure 411, 412, 421, 422 and clamping zones 510, 520, 610, 620 may be applied to the example shown in Figures 4 and 5.

[0069] The substrate support 1 desirably comprises a plurality of first protrusions (not shown) extending from the first side of the substrate support 1. The first protrusions may be burls 20 as described above with reference to Figure 3. The plurality of first protrusions are desirably configured to support the substrate W. The distal ends of the plurality of first protrusions desirably define a support plane which may be a substantially flat plane. The seal structure 411, 412 desirably has a height less than that of the plurality of first protrusions.

[0070] Figure 9A and Figure 9B each depict arrangements of a first side of a substrate support 1 having a plurality of clamping zones 600 defined by a plurality of seal structures 400. The substrate support 1 may be the one as described above with reference to Figures 4, 5 and 6. Each seal structure 400 may be continuous, without any discontinuities. A single seal structure may define a clamping zone 611. In the arrangement of Figure 9 A, one or more of the clamping zones 600 is defined by aplurality of seal structures 400. In other words, two seal structures 400 of the plurality of seal structures 400 may together define an enclosed area corresponding to a respective clamping zone 612, 613, 614. In the arrangement of Figure 9A, similarly to the arrangement of Figure 7, the substrate support 1 comprises a plurality of clamping zones 611, 612, 613, 614. Each clamping zone 611, 612, 613, 614 of the plurality of clamping zones 600 desirably corresponds to a channel of the plurality of channels 50 on the second side of the substrate support 1. Each clamping zone 611, 612, 613, 614 is arranged at a different radial distance from the centre of the substrate support 1. For example, a first clamping zone 611 is arranged at a centre of the substrate support 1, a second clamping zone 612 is arranged radially outward of the first clamping zone 611, a third clamping zone 613 is arranged radially outward of the second clamping zone 612, and a fourth clamping zone 614, is arranged radially outward of the third clamping zone 613. In the arrangement of Figure 9 A, the seal structures 400 are not equally spaced in a radial direction of the substrate support 1. In an alternative arrangement, the seal structures 400 may be equally spaced in a radial direction of the substrate support 1. Alternatively, the seal structures 400 may be more closely spaced towards a periphery of the substrate support 1 than towards a centre of the substrate support 1, for example to reduce a difference in area of the clamping zones 600. In the arrangement of Figure 9A, each seal structure extends 360° in a circumferential direction of the substrate support 1.

[0071] Figure 9B depict a first side 110 of a substrate support 1 having a plurality of clamping zones 600 defined by a plurality of seal structures 400. Each seal structure 400 desirably forms an enclosed area corresponding to the respective clamping zone 600. In other words, each seal structure 400 may be continuous, without any discontinuities, and may define a clamping zone 600. In the arrangement of Figure 9B, the substrate support 1 comprises a plurality of groups 601, 602, 603 of clamping zones 600. Each group 601, 602, 603 of clamping zones 600 desirably corresponds to a channel of the plurality of channels 50 on the second side of the substrate support 1. Each group 601, 602, 603 of clamping zones 600 is arranged at a different radial distance from the centre of the substrate support 1. For example, a first group 601 is arranged at a centre of the substrate support 1, a second group 602 is arranged radially outward of the first group 601, and a third group 603 is arranged radially outward of the second group 602. One or more of the groups 602, 603 may comprise a plurality of seal structures 400. In other words, one or more of the groups 602, 603 may comprise a plurality of clamping zones 600. In the arrangement of Figure 9B, the second and third groups 602, 603 each comprise a plurality of clamping zones 600 distributed in a circumferential direction around the substrate support 1.

[0072] Figure 10 depicts a cross-sectional view of a substrate support 1. In this arrangement, a floor level of the first side is different between clamping zones. In the arrangement of Figure 10, a distance between the first side and the second side is different between clamping zones. In particular, in this example, the main body 10 of the substrate support 1 is thinner in a centre than at a periphery.

[0073] A first floor level 111 of the first side in a first clamping zone is lower than a second floor level 112 of the first side in a second clamping zone. The second clamping zone is closer to a periphery of the substrate support 1 than the first clamping zone. Furthermore, the second floor level 112 of the first side in the second clamping zone is lower than a third floor level 113 of the first side in a third clamping zone. The third clamping zone is closer to a periphery of the substrate support 1 than the second clamping zone. In the arrangement shown in Figure 10, there is a step change in floor level 111, 112, 113 between clamping zones. In an alternative arrangement, the floor level may be sloped such that an average floor level is different between clamping zones (not shown). The sloped floor may provide a smooth transition between clamping zones. In a further arrangement, the floor level 111, 112, 113 may be substantially flat within each clamping zone, but the transition in floor level between clamping zones may be sloped. In a preferred arrangement (not shown in the Figures), the substrate support 1 may comprise one or more seal structures 400 to define one or more of the clamping zones in addition to the floor level being different between claiming zones. The seal structures may be the same as the seal structures 411, 412 described above with reference to Figure 8 or seal structures 400 as described above with reference to Figure 9A.

[0074] The floor level being higher closer to the periphery and lower at the centre of the first side of the substrate support 1 may provide a benefit particularly when supporting a warped substrate W having a bowl, or umbrella, shape. With such a warped wafer, if the first side of the substrate support 1 is flat and the distance between the first side and the underside of the substrate W will increase towards the periphery of the substrate W. Even before providing any flow to induce negative pressure, the shape of the floor being a higher level towards an outer periphery of the substrate W may bring the floor of the first side closer to the substrate W compared to substrate support 1 having a flat floor level across the first side. Furthermore, once the innermost clamping zone is activated to induce flow providing negative pressure, the centre of the substrate W will be attracted towards the first side, as well as possibly further reducing a distance between the floor of the first side in a clamping zone radially outwards of the innermost clamping zone. In this way, the amount of flow required to secure the warped substrate W to the substrate support 1 may be reduced by the different floor levels 111, 112, 113 of the first side, particularly when implemented in combination with the controllable clamping zones.

[0075] As shown in Figures 6 to 8 and 10, the main body 10 of the substrate support 1 may define a plurality of loading pin holes 7. As shown in Figures 8 and 10, each of the loading pin holes 7 is a through hole extending from the second side to the first side. The loading pin holes 7 may each be configured to receive a loading pin (not shown) for aiding in the loading and / or unloading of a substrate W to / from the substrate support 1.

[0076] The plurality of loading pin holes 7 desirably comprises two or more groups of loading pin holes 7. The loading pin holes 7 of each group of loading pin holes 7 are disposed at a different radial distance from a centre of the substrate support 1. In other words, the loading pin holes 7 of a firstgroup of loading pin holes 7 may be disposed radially inwards from the loading pin holes 7 of a second group of loading pin holes 7. Optionally, the loading pin holes 7 belonging to the same group may be disposed at the same radial distance from a centre of the substrate support 1. Each group of loading pin holes 7 may correspond to a respective clamping zone.

[0077] The substrate support 1 may be configured to support substrates W of different sizes. For example, a relatively smaller substrate W may be loaded / unloaded using loading pin holes 7 of a group of loading pin holes 7 disposed at a radially inward location. A relatively larger substrate W may be loaded / unloaded using loading pin holes 7 of a group of loading pin holes 7 disposed at a radially outward location, instead of or in addition to the radially inward loading pin holes 7. Alternatively, or additionally, the relatively smaller substrate W may be secured to the substrate support 1 by applying negative pressure on a radially inward clamping zone, e.g., first clamping zone 510, 610. The relatively larger substrate W may be secured to the substrate support 1 by applying negative pressure on a radially outward clamping zone, e.g., second clamping zone 520, 620, in addition to the radially inward clamping zone, e.g., first clamping zone 510, 610.

[0078] The substrate support 1 may further comprise one or more raised regions 9 on the first side surrounding one or more of the loading pin holes 7. In other words, a floor level of the first side in one or more raised regions 9 surrounding one of the loading pin holes 7 is higher than a floor level of the first side in a region further from the one or more loading pin holes 7. As shown for example in Figure 10, the raised region 9 surrounding the loading pin hole 7, i.e., area 90, is at a higher floor level than the floor level 112 in the area surrounding the raised region 9. In other words, the raised region 9 has a higher floor level than the floor level 112 of a substantial area of that clamping zone on the first side. The raised region 9 may reduce a likelihood of leakage of flow around the corresponding loading pin hole 7. Desirably, a seal structure or a raised region 9 may be provided around each of the loading pin holes 7 of the substrate support 1. Therefore, the pressure on the substrate W may be more uniform. Furthermore, the amount of flow required to secure the substrate W sufficiently may be reduced.

[0079] Figure 11 A-C depicts example arrangements of the area 90 including the raised region 9 on Figure 10. The raised region 9 may be flat, as shown for example in Figure 11A. In particular, the raised region 9 may be a flat region 91 that is level with the floor level 112 surrounding the raised region 9, which may be horizontal. The raised region 9 may have an upward gradient profile towards the one or more loading pin holes 7, with respect to a floor level 112 surrounding the raised region 9. In other words, in the raised region 9, the floor level may increase with decreasing distance to the loading pin hole 7. For example, the upward gradient profile may be a slope 92, as shown in Figure 1 IB. Alternatively, the raised region 9 may have an upward gradient profile increasing with radial distance from a centre of the substrate support 1. The upward gradient profile may have any shape. In a preferred arrangement, the upward gradient profile may be a plurality of steps 93, as shown in Figure 11C. A plurality of steps 93 may be easier to manufacture than a slope or a curved profile.

[0080] As shown in the arrangements of Figures 12A, 12B and 13, there is a substrate support 1 configured to support a substrate W. The substrate support 1 comprises a main body 10 having a first side 14 configured to support the substrate W, and a second side 15 opposite to the first side 14. The main body 1 defines a plurality of through holes 12 and a plurality of inlets. The plurality of inlets is for connection to one or more positive and / or negative pressure sources (not shown). The inlets may be the same as the inlets 70 described above with reference to Figures 4 to 7. Each through hole 12 extends from the second side 15 to the first side 14. Each through hole 12 is in fluid communication with at least one inlet of the plurality of inlets.

[0081] The substrate support 1 is optionally a substrate support 1 as described above, for example in relation to Figures 2 to 10. The main body 10 may further define a plurality of through holes 12 in a region not corresponding to the channels 50. As shown for example in Figure 12A and 12B, each through hole 12 extends from the second side 15 to the first side 14 of the main body 1.

[0082] Fluid flow may be provided through the through holes 12 to enable the flow to provide negative pressure to aid in securing the substrate W to the substrate support 1. As shown in Figure 12 A, fluid desirably flows (in the direction shown by the arrow) through the through holes 12 from the first side 14 to the second side 15 of the main body 10 in order to generate a force attracting the substrate W to the substrate support 1. In some circumstances, the substrate W may be warped such that some areas, often the more peripheral areas, of the substrate W are farther from the substrate support 1 than the other areas, such as more central areas, of the substrate W. In other words, a distance between the through holes 12 and the substrate W in one region may be greater than the distance between the through holes 12 and the substrate W in another region.

[0083] If all of the through holes 12 are unrestricted, the flow and associated force is distributed among the plurality of through holes 12, for example in the region 121 of Figure 12A. In the region 121 where the substrate W is farther from the substrate support 1, the attractive force provided by flow through the through holes 12 may have less influence on the substrate W than the force provided by flow through the through holes 12 in the other regions, where the substrate W is closer to the substrate support 1. It is therefore desirable to make more efficient use of flow through the through holes 12 by applying the attractive force in a more targeted manner. This effect may be achieved, for example, by using check valves 80 to restrict flow through certain through holes 12 at certain times. In this way, the attractive force provided through the unrestricted through holes 12 may be locally greater. The through holes 12 may then be sequentially unrestricted in order to locally attract the substrate W to the substrate support 1 in a region around each through hole 12 until the substrate W is clamped to the substrate support 1.

[0084] In the arrangement depicted in Figure 12B, one ore more of the through holes 12 is in fluid communication with a corresponding check valve 80. The check valve 80 is configured to restrict fluid flow through the corresponding through hole 12 when the check valve 80 is in a closedcondition. In other words, in the closed condition the check valve 80 may partially or fully block flow through the corresponding through hole 12. The check valve 80 is configured to allow fluid flow through the corresponding through hole 12 when the check valve 80 is in an open condition. The substrate support 1 may comprise the one or more check valves 80. Alternatively, the check valves 80 may be disposed more remote from the substrate support 1, but within a broader substrate support system.

[0085] In the arrangement shown in Figure 12B, the check valve 80 is part of the substrate support 1. In particular, in the arrangement of Figure 12B, the check valve 80 is fully disposed within the through hole 12 in order to restrict fluid flow through the through hole 12. In another arrangement (not shown), the check valve 80 may be only partially disposed within the through hole 12. Alternatively, the check valve 80 may be disposed elsewhere in a flow path to the through hole 12 in order to restrict fluid flow through the through hole 12.

[0086] As shown in Figure 12B, the check valves 80 are desirably configured to restrict flow through the through holes 12 in regions where the substrate W is more distant from the substrate support 1. The check valves 80 are desirably configured to open to allow flow through the through holes 12 in a region 122 where the substrate W has become close enough to the substrate support 1 for the attractive force to be effective. For example, in the arrangement of Figure 12B, the two rightmost through holes 12 have check valves 80 in the closed condition, whereas the check valve 80 to the left of those is in the open condition such that there is flow in the region 122 where the substrate W has become close enough. As the attractive force takes effect, the substrate W will be further drawn towards the substrate support 1 and the adjacent check valve 80 may then open in order to allow flow to pass through the through hole 12 unrestricted. In this way, the substrate W may be clamped in place on the substrate support 1 more quickly and / or more efficiently than in an arrangement (such as that of Figure 12 A) wherein flow through all through holes 12 is completely unrestricted at all times.

[0087] The check valve 80 is optionally configured to be controllable to change from the closed condition to the open condition. The check valve 80 may change from the closed condition to the open condition in response to a command from a user. Alternatively, or additionally, the check valve 80 may change from the closed condition to the open condition in response to a certain predetermined condition being met.

[0088] The check valve 80 is preferably configured to change from the closed condition to the open condition when a pressure difference between a first pressure and a second pressure is reduced below a predetermined opening pressure difference threshold. The first pressure is a pressure on an upstream side 801 of the check valve 80 and the second pressure is the pressure on a downstream side 801 of the check valve 80 in a direction of fluid flow (as shown by the arrow in Figure 12B). In other words, the check valve 80 is configured to change from the closed condition to the open condition in response to the pressure difference across the check valve 80 dropping below the predetermined opening pressure difference threshold. The substrate support 1, or substrate support system, isdesirably configured such that the difference between the first pressure and the second pressure is reduced as the distance between the substrate W and the first side 14 of the main body 10 adjacent to the corresponding through hole 12 is decreased. In other words, the substrate support 1 and check valves 80 are desirably configured such that the check valves 80 are changed from the closed condition to the open condition in response to the substrate W in the region adjacent to the corresponding through hole 12 moving close enough to the first side 14 of the main body 10. For example, a check valve 80 may change from the closed condition to the open condition in response to the substrate W being within a predetermined proximity to the first side 14 of the main body 10 in the region 122 of the corresponding through hole 122.

[0089] Figure 13 illustrates an arrangement wherein a warped substrate W is being clamped on to a substrate support 1. In Figure 13, the bending torque T applied to the substrate W is illustrated as the area under the curve. The arrangement of Figure 13 includes a plurality of check valves 80. At the point in time shown in Figure 13, the two leftmost check valves 80, depicted with adjacent arrows to show unrestricted fluid flow, are in the open condition, and the two rightmost check valves 80 are in the closed condition. The two leftmost check valves 80 are in the open condition to open up a local vacuum flow in a region where the warped substrate W is close enough to the corresponding through holes 12 to have a significant pneumatic torque (or downforce) effect, while not consuming unnecessary flow when the substrate W is further away.

[0090] The substrate support 1 of the arrangement of Figure 13 includes a plurality of burls 20 configured to support the substrate W when it is clamped to the substrate support 1. A floor height h of the burls 20 is a peak of the burl 20 above an upper surface of the main body 10. With the arrangement including the check valves 80, the floor height h can be selected at a lower value than normal. This is because the allowable pressure drop per in-plane length unit is much higher. There is therefore desirably an increase in attractive force on the substrate W due to the smaller floor height h, as well as an increase in local attractive force through each through hole 12 due to the closure of through holes 12 in regions where the distance of the substrate W would anyway make the attractive force ineffective. This arrangement may desirably provide a more effective bending torque T on the warped substrate W to bring it to a flat, clamped condition more efficiently.

[0091] The plurality of through holes 12 may define a plurality of clamping zones. In other words, similarly to the channels 50 described above, for example with reference to Figures 4 to 10, the through holes 12 and check valves 80 may enable the substrate W to be secured sequentially in different regions. In other words, there may be a first group comprising one or more through holes 12 and a second group comprising one or more through holes 12. The first group and second group may be disposed at different regions of the main body 10. In this way, the check valves 80 corresponding to the first group of through holes 12 may be set to the open condition at a different time to the second group of check valves 80. There may be more than two groups of through holes 12.

[0092] For example, the through holes 12 of the second group may each be disposed in a region more radially outward than a region in which the through holes 12 of the first group are disposed in the main body 10. With an arrangement such as this, a centre of the substrate W may be secured before a more radially outward region of the substrate W is secured.

[0093] Furthermore, through holes 12 may be provided within the different clamping zones 601, 602, 603, 611, 612, 613 of the arrangement of Figures 9A and 9B. In other words, one or more through holes 12, having corresponding check valves 80, may be provided in one or more of the clamping zones 601, 602, 603, 611, 612, 613. For example, one or more through holes 12, having corresponding check valves 80, may be provided in each clamping zone 601, 602, 603, 611, 612, 613. The corresponding check valve 80 may be configured to open to begin the activation of the corresponding clamping zone, within which the corresponding through hole 12 is disposed. Alternatively, the corresponding check valve 80 may be configured to open in response to activation of the corresponding clamping zone, within which the corresponding through hole 12 is disposed. In this way, the channels 50 as well as the through holes 12 and check valves 80, may act together to provide a means to efficiently clamp substrates W in a controlled manner.

[0094] Figure 14A illustrates a check valve 80 in the closed condition. Figure 14B illustrates the check valve 80 of Figure 14A in the open condition. The check valve 80 of Figures 14A and 14B comprises a spring 81. The pressure difference is a pressure difference between first pressure Pl at an upstream side of the check valve 80, and second pressure P2 at a downstream side of the check valve 80. The check valve 80 of Figures 14A and 14B is configured to remain in a closed condition, until the first pressure Pl at the upstream side of the check valve 80 (opposite a side from which negative pressure is applied) is sufficiently lowered. In other words, the pressure difference (P2-P1) becomes smaller than the pressure needed to counteract the spring force that opens up the check valve 80. A force of the spring 81 may be based on the desired predetermined pressure difference threshold. The check valve 80 is optionally configured such that the force of the spring 81 is adjustable. In this way, the predetermined pressure difference threshold may be adjusted as desired, for example according to different applications or environmental conditions.

[0095] The spring 81 may be any suitable type of spring, for example a coil spring or a leaf spring. The spring is preferably a non-linear spring. For example, the spring 81 may be configured such that the rate of change of flow rate through the check valve 80 is greater for a pressure difference between the first pressure Pl and the second pressure P2 close to the predetermined pressure difference threshold than for a pressure difference between the first pressure Pl and the second pressure P2 with a greater difference to the predetermined pressure difference threshold. In this way, there may be a more precise control of flow rate at pressure difference values at or around the predetermined pressure difference threshold.

[0096] In some arrangements, for example the arrangement of Figure 13, the spring 81 of the check valves 80 is a push spring. In other words, the spring 81 is configured to extend when a compressiveload on the spring 81 is reduced below a predetermined threshold. In this arrangement the fixed end of the push spring 81 is fixed on a downstream side of the check valve 80, in a direction of flow of fluid.

[0097] In an alternative arrangement, the spring 81 may be a pull spring. In other words, the spring 81 is configured to contract when a tensile load on the spring 81 is reduced below a predetermined threshold. In this arrangement, a fixed end of the push spring 82 may be fixed on an upstream side of the check valve 80.

[0098] The check valve 80 may comprise a block 82 disposed at the free end of the spring 81, as shown in the arrangement of Figures 14A and 14B. The block 82 is configured to restrict or block flow through the corresponding through hole 12, or in a flow path to the corresponding through hole 12, when the check valve 80 is in the closed condition. The block 82 desirably has a diameter larger than a width of the spring 81. The block 82 may have any suitable shape to perform the restriction / blocking function. For example, the block may be a spherical ball.

[0099] Furthermore, the check valve 80 may comprise an alternative mechanism instead of the spring 81. Any suitable mechanism may be used. For example, the check valve 80 may comprise a swing type mechanism configured to swing or rotate into the closed condition where the flow path to or through the corresponding through hole 12 is restricted and into the open condition where the flow to or through the corresponding through hole 12 is not restricted.

[0100] The check valve 80 optionally defines a bleed hole. The bleed hole may desirably make the check valve 80 more robust to small leaks of flow. The bleed hole may be defined between a surface of the through hole 12 in the main body 10, and a part of the check valve 80. The bleed hole may be defined between the block 82 and a seat 85 in which the block 82 is configured to sit when the check valve 80 is in a closed condition (such as the closed condition shown in Figure 14A). The check valve 80 is desirably configured such that the size of the bleed hole is adjustable. This may enable local adjustments to be made at each check valve 80 making the system more robust to different flow conditions.

[0101] The check valves 80 may configured to be controllable to return from the open condition to the closed condition. For example, it may be desirable to set the check valves 80 in a closed condition after one substrate W has been removed and before a next substrate W is clamped to the substrate support 1. In this way, the check valves 80 may open when the required conditions are met, in order to efficiently secure the substrate W to the substrate support 1 and may then be closed again ready for the next substrate W.

[0102] The check valves 80 may be configured to be returned from the open condition to the closed condition by controlling the positive and / or negative pressure sources. In particular, the positive and / or negative pressure sources may be controlled such that a pressure difference between the first pressure Pl, on the upstream side 801 of the check valve 80, and the second pressure P2, on the downstream side of the check valve 802, exceeds a predetermined closing pressure differencethreshold. In other words, the check valve 80 may be configured to return to the closed condition when the pressure difference reaches or exceeds the predetermined closing pressure difference threshold.

[0103] Alternatively, or additionally, any suitable means may be used to aid in returning the check valve 80 from the open condition to the closed condition. For example, the check valve 80 may be configured to be returned from an open condition to a closed condition by applying an acceleration and / or a magnetic force.

[0104] It will also be appreciated that the principles of the present invention can be applied to metrology or lithographic tools and clamping systems that employ electrostatic clamps. In such a case, rather than controlling the flow rate of an evacuation flow, other relevant parameters such as the voltage applied to the electrostatic clamp may be controlled.

[0105] Although specific reference may be made in this text to the use of a metrology system in the context of the manufacture of ICs, it should be understood that the metrology system described herein may have other applications, such as in the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquid-crystal displays (LCDs), thin film magnetic heads, etc. The skilled artisan will appreciate that, in the context of such alternative applications, any use of the terms “wafer” or “die” herein may be considered as synonymous with the more general terms “substrate” or “target portion", respectively. The substrate referred to herein may be processed, before or after exposure, in for example a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), a metrology tool and / or an inspection tool. Where applicable, the disclosure herein may be applied to such and other substrate processing tools. Further, the substrate may be processed more than once, for example in order to create a multi-layer IC, so that the term substrate used herein may also refer to a substrate that already contains one or multiple processed layers.

[0106] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention may be used in other applications.

[0107] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described.

[0108] The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

[0109] Embodiments include the following numbered clauses:1. A substrate support configured to support a substrate, comprising a main body having: a first side configured to support the substrate; and a second side opposite to the first side; wherein the second side is formed with a plurality of grooves, the plurality of grooves comprising a plurality of channels and a plurality of conduits; wherein the plurality of channels comprises a first channel and a second channel substantially surrounding the first channel; wherein the plurality of conduits comprises at least one first conduit and at least one second conduit; wherein the first channel is in fluid communication with the at least one first conduit, and the at least one first conduit extends towards the periphery of the substrate support, and wherein the second channel is in fluid communication with the at least one second conduit, and the at least one second conduit extends towards the periphery of the substrate support.2. The substrate support according to clause 1, wherein the second channel has a substantially arc shape.3. The substrate support according to clause 1 or 2, wherein the first channel has a substantially arc shape.4. The substrate support according to clause 3 when dependent on clause 2, wherein the first channel and the second channel are concentric with each other.5. The substrate support according to any preceding clause, wherein the second channel is formed with a discontinuity in a circumferential direction of the substrate support, wherein the discontinuity forms a cut region on the second side, wherein the at least one first conduit extends across the cut region.6. The substrate support according to any preceding clause, wherein the first conduit extends in a radial direction.7. The substrate support according to any preceding clause, wherein the second conduit extends in a radial direction.8. The substrate support according to clause 7 when dependent on clause 6, wherein the first conduit and the second conduit form a non-zero angle.9. The substrate support according to any preceding clause, wherein each of the plurality of conduits is in fluid communication with one of the plurality of channels.10. The substrate support according to any preceding clause, further comprising a plurality of inlets for connection to one or more positive and / or negative pressure sources, wherein each conduit is in fluid communication with an inlet of the plurality of inlets.11. The substrate support according to clause 10, wherein each of the plurality of inlets is disposed towards the periphery of the substrate support.12. The substrate support according to any preceding clause, wherein the plurality of channels comprises at least one further channel in addition to the first channel and the second channel.13. The substrate support according to clause 12, wherein the at least one further channel surrounds the second channel.14. The substrate support according to clause 13, wherein the at least one further channel and the second channel are concentric with each other.15. The substrate support according to any of clauses 12 to 14, wherein the at least one further channel comprises two or three channels.16. The substrate support according to any preceding clause, wherein each of the first channel and the second channel comprises at least one through hole, wherein the at least one through hole extends from the second side to the first side.17. The substrate support according to clause 16, wherein the at least one through hole comprises a plurality of through holes.18. The substrate support according to clause 16 or 17, wherein the main body further defines a plurality of through holes in a region not corresponding to the first channel and the second channel, wherein each through hole extends from the second side to the first side of the main body.19. The substrate support according to any of clauses 16 to 18, wherein one or more through hole is in fluid communication with a corresponding check valve, wherein the check valve is configured to restrict fluid flow through the corresponding through hole when the check valve is in a closed condition and to allow fluid flow through the corresponding through hole when the check valve is in an open condition; wherein the check valve is configured to change from a closed position to an open condition when a pressure difference between a first pressure, on an upstream side of the check valve, and a second pressure, on a downstream side of the check valve in a direction of fluid flow, is reduced below a predetermined opening pressure difference threshold.20. A substrate support configured to support a substrate, comprising a main body having a first side configured to support the substrate, and a second side opposite to the first side; wherein the main body defines a plurality of through holes, wherein each through hole extends from the second side to the first side; and a plurality of inlets for connection to one or more positive and / or negative pressure sources, wherein each through hole is in fluid communication with at least one inlet of the plurality of inlets, wherein one or more through holes is in fluid communication with a corresponding check valve configured to restrict fluid flow through the corresponding through hole whenthe check valve is in a closed condition and to allow fluid flow through the corresponding through hole when the check valve is in an open condition; and the check valve is configured to change from a closed position to an open condition when a pressure difference between a first pressure, on an upstream side of the check valve, and a second pressure, on a downstream side of the check valve in a direction of fluid flow, is reduced below a predetermined opening pressure difference threshold.21. The substrate support according to clauses 20, wherein each check valve is configured to restrict fluid flow through the corresponding through hole when the check valve is in the closed condition and to allow fluid flow through the corresponding through hole when the check valve is in the open condition; wherein each check valve is configured to change from an open position to a closed position when a pressure difference between a first pressure, on an upstream side of the check valve, and a second pressure, on a downstream side of the check valve in a direction of fluid flow, exceeds a predetermined pressure difference threshold.22. The substrate support according to any one of clauses 19 to 21, wherein the pressure difference between the first pressure and the second pressure is reduced as the distance between the substrate and the first side of the main body adjacent to the corresponding through hole is decreased.23. The substrate support according to any one of clauses 19 to 22, wherein the plurality of through holes is disposed at different radial distances from a centre of the main body, and the plurality of through holes defines a plurality of clamping zones at different radial distances from the centre of the main body.24. The substrate support according to any preceding clause, wherein the plurality of channels on the second side is associated with a plurality of corresponding clamping zones.25. The substrate support according to clause 24, wherein each clamping zone corresponds to a respective channel.26. The substrate support according to any preceding clause, comprising a plurality of loading pin holes, wherein each of the loading pin holes is a through hole extending from the second side to the first side.27. The substrate support according to clause 26, the plurality of loading pin holes comprises two or more groups of loading pin holes, wherein the loading pin holes of each group of loading pin holes are disposed at a different radial distance from a centre of the substrate support.28. The substrate support according to clause 26 or 27, comprising one or more raised regions on the first side surrounding one of the loading pin holes, wherein a floor level of the first side in one or more raised regions surrounding one of the loading pin holes is higher than a floor level of the first side in a region further from the one or more loading pin holes.29. The substrate support according to clause 28, wherein the raised region has an upward gradient profile towards the one or more loading pin holes.30. The substrate support according to clause 29, wherein the upward gradient profile is a slope or a plurality of steps.31. The substrate support according to any of clauses 24 to 30, wherein a floor level of the first side is different between clamping zones.32. The substrate support according to clause 31, wherein a distance between the first side and the second side is different between clamping zones.33. The substrate support according to clause 31 or 32, wherein a floor level of the first side in a first clamping zone is lower than a floor level of the first side in a second clamping zone, wherein the second clamping zone is closer to a periphery of the substrate support than the first clamping zone.34. The substrate support according to any preceding clause, further comprising a plurality of first protrusions extending from the first side, wherein the plurality of first protrusions are configured to support the substrate.35. The substrate support according to clause 34, wherein the distal ends of the plurality of first protrusions define a substantially flat plane.36. The substrate support according to any preceding clause, further comprising a plurality of second protrusions extending from the second side, wherein the plurality of second protrusions are configured to support the substrate support to a stage.37. The substrate support according to clause 36, wherein the distal ends of the plurality of second protrusions define a substantially flat plane.38. The substrate support according to any preceding clause, wherein at least one of the plurality of grooves is surrounded by a seal structure on the second side.39. The substrate support according to clause 38, wherein the seal structure defines one or more clamping zones on the second side.40. The substrate support according to clause 38 or 39 when dependent on clause 36 or 37, wherein the seal structure has a height less than that of the plurality of second protrusions.41. The substrate support according to any preceding clause, wherein at least one of the plurality of grooves is surrounded by a seal structure on the first side.42. The substrate support according to clause 41, wherein the seal structure defines one or more clamping zones on the first side.43. The substrate support according to clause 41 or 42 when dependent on clause 34 or 35, wherein the seal structure has a height less than that of the plurality of first protrusions.44. A substrate support system comprising the substrate support of any preceding clause.45. The substrate support system according to clause 44 when dependent from clause 24, 25, 39 or 42, further comprising one or more controllers configured to individually control each clampingzone to activate the respective clamping zones to secure a substrate to the substrate support in a region of the first side corresponding to the respective clamping zones.46. The substrate support system according to clause 45, wherein the one or more controllers comprise a plurality of controllers, wherein each controller of the plurality of controllers is configured to control a respective clamping zone.47. The substrate support system according to clause 45 or 46, wherein the one or more controllers are configured to control a plurality of positive and / or negative pressure supply sources in fluid communication with the plurality of channels via the plurality of conduits.48. The substrate support system according to clause 47, wherein each positive and / or negative pressure supply source is in fluid communication with one channel of the plurality of channels via at least one conduit of the plurality of conduits.49. The substrate support system according to any of clauses 45 to 48, wherein the one or more controllers are configured to activate the clamping zones sequentially.50. The substrate support according to any of clauses 45 to 49, wherein the one or more controllers are configured to activate the clamping zones based on a pressure in the clamping zones.51. The substrate support system according to clause 50, wherein the one or more controllers are configured to activate a first clamping zone of the plurality of clamping zones, and once a pressure in the first clamping zone exceeds a pressure threshold, to activate a second clamping zone of the plurality of clamping zones.52. The substrate support system according to clause 51, wherein the second clamping zone is disposed closer to a periphery of the substrate support than the first clamping zone.53. The substrate support system according to any one of clauses 44 to 52, further comprising a stage configured to support the substrate support, wherein at least one of the plurality of inlets is connected to a negative pressure source to secure the substrate support to the stage.54. The substrate support system according to any one of clauses 44 to 53, when dependent on any of clauses 19 to 23, further comprising the one or more check valves.55. The substrate support system according to clause 54, wherein the one or more check valves are disposed within the corresponding through holes.56. The substrate support system according to clause 54 or 55, wherein the one or more check valves comprises a spring, and wherein the predetermined pressure difference threshold is set based on a force of the spring.57. The substrate support system according to clause 56, wherein the one or more check valves are configured such that the force of the spring is adjustable.58. The substrate support system according to clause 56 or 57, wherein the spring is a push spring, and wherein a fixed end of the push spring is fixed on a downstream side of the check valve, in a direction of flow of fluid.59. The substrate support system according to clause 56 or 57, wherein the spring is a pull spring, and wherein a fixed end of the push spring is fixed on an upstream side of the check valve, in a direction of flow of fluid.60. The substrate support system according to any one of clauses 56 to 59, wherein a block is disposed at the free end of the spring, wherein the block is configured to restrict or block flow through the through hole when the check valve is in the closed condition.61. The substrate support system according to clause 60, wherein the block is a spherical ball.62. The substrate support system according to any one of clauses 56 to 61, wherein the spring is a leaf spring.63. The substrate support system according to any one of clauses 56 to 62, wherein the spring is a non-linear spring.64. The substrate support system according to any one of clauses 54 to 63, wherein the check valve defines a bleed hole.65. The substrate support system according to clause 64, wherein the bleed hole is defined between a surface of the through hole in the main body, and a part of the check valve.66. The substrate support system according to clause 64 or 65, wherein the check valve is configured such that the size of the bleed hole is adjustable.67. The substrate support system according to any one of clauses 54 to 66, wherein the check valve is configured to be controllable to return from the open condition to the closed condition.68. The substrate support system according to clause 67, wherein the check valve is configured to be returned from the open condition to the closed condition by controlling the positive and / or negative pressure sources such that the pressure difference between the first pressure and the second pressure exceeds a predetermined closing pressure difference threshold.69. The substrate support system according to clause 67 or 68, wherein the check valve is configured to be returned from the open condition to the closed condition by applying an acceleration and / or a magnetic force.70. A metrology system comprising the substrate support system according to any of clauses 44 to 69.

Claims

CLAIMS1. A substrate support configured to support a substrate, comprising a main body having: a first side configured to support the substrate; and a second side opposite to the first side; wherein the second side is formed with a plurality of grooves, the plurality of grooves comprising a plurality of channels and a plurality of conduits; wherein the plurality of channels comprises a first channel and a second channel substantially surrounding the first channel; wherein the plurality of conduits comprises at least one first conduit and at least one second conduit; wherein the first channel is in fluid communication with the at least one first conduit, and the at least one first conduit extends towards the periphery of the substrate support, and wherein the second channel is in fluid communication with the at least one second conduit, and the at least one second conduit extends towards the periphery of the substrate support.

2. The substrate support according to claim 1, wherein the second channel has a substantially arc shape, and / or wherein the first channel has a substantially arc shape, desirably wherein the first channel and the second channel are concentric with each other.

3. The substrate support according to any preceding claim, wherein the second channel is formed with a discontinuity in a circumferential direction of the substrate support, wherein the discontinuity forms a cut region on the second side, wherein the at least one first conduit extends across the cut region, and / or wherein the first conduit extends in a radial direction, and / or wherein the second conduit extends in a radial direction, desirably wherein the first conduit and the second conduit form a non-zero angle.

4. The substrate support according to any preceding claim, wherein each of the plurality of conduits is in fluid communication with one of the plurality of channels, and / or further comprising a plurality of inlets for connection to one or more positive and / or negative pressure sources, wherein each conduit is in fluid communication with an inlet of the plurality of inlets, desirably wherein each of the plurality of inlets is disposed towards the periphery of the substrate support.

5. The substrate support according to any preceding claim, wherein the plurality of channels comprises at least one further channel in addition to the first channel and the second channel,desirably wherein the at least one further channel surrounds the second channel, desirably wherein the at least one further channel and the second channel are concentric with each other, and / or wherein the at least one further channel comprises two or three channels.

6. The substrate support according to any preceding claim, wherein each of the first channel and the second channel comprises at least one through hole, wherein the at least one through hole extends from the second side to the first side, desirably wherein the at least one through hole comprises a plurality of through holes, desirably wherein the main body further defines a plurality of through holes in a region not corresponding to the first channel and the second channel, wherein each through hole extends from the second side to the first side of the main body, desirably wherein one or more through hole is in fluid communication with a corresponding check valve, wherein the check valve is configured to restrict fluid flow through the corresponding through hole when the check valve is in a closed condition and to allow fluid flow through the corresponding through hole when the check valve is in an open condition; wherein the check valve is configured to change from a closed position to an open condition when a pressure difference between a first pressure, on an upstream side of the check valve, and a second pressure, on a downstream side of the check valve in a direction of fluid flow, is reduced below a predetermined opening pressure difference threshold.

7. The substrate support according to any preceding claim, wherein the plurality of channels on the second side is associated with a plurality of corresponding clamping zones, desirably wherein each clamping zone corresponds to a respective channel.

8. The substrate support according to any preceding claim, comprising a plurality of loading pin holes, wherein each of the loading pin holes is a through hole extending from the second side to the first side, desirably the plurality of loading pin holes comprises two or more groups of loading pin holes, wherein the loading pin holes of each group of loading pin holes are disposed at a different radial distance from a centre of the substrate support, desirably comprising one or more raised regions on the first side surrounding one of the loading pin holes, wherein a floor level of the first side in one or more raised regions surrounding one of the loading pin holes is higher than a floor level of the first side in a region further from the one or more loading pin holes, desirably wherein the raised region has an upward gradient profile towards the one or more loading pin hole, desirably wherein the upward gradient profile is a slope or a plurality of steps.

9. The substrate support according to claim 7 or 8, wherein a floor level of the first side is different between clamping zones, desirably wherein a distance between the first side and the second side is different between clamping zones, desirably wherein a floor level of the first side in a firstclamping zone is lower than a floor level of the first side in a second clamping zone, wherein the second clamping zone is closer to a periphery of the substrate support than the first clamping zone.

10. The substrate support according to any preceding claim, further comprising a plurality of first protrusions extending from the first side, wherein the plurality of first protrusions are configured to support the substrate, and / or further comprising a plurality of second protrusions extending from the second side, wherein the plurality of second protrusions are configured to support the substrate support to a stage, and / or wherein at least one of the plurality of grooves is surrounded by a seal structure on the second side, and / or wherein at least one of the plurality of grooves is surrounded by a seal structure on the first side.

11. The substrate support according to claim 10, wherein the distal ends of the plurality of first protrusions define a substantially flat plane, and / or wherein the distal ends of the plurality of second protrusions define a substantially flat plane, and / or wherein the seal structure defines one or more clamping zones on the second side, and / or wherein the seal structure has a height less than that of the plurality of second protrusions, desirably wherein the seal structure defines one or more clamping zones on the first side, desirably wherein the seal structure has a height less than that of the plurality of first protrusions.

12. A substrate support system comprising the substrate support of any preceding claim.

13. A lithographic apparatus comprising the substrate support of any of claims 1-11 or the substrate support system of claim 12.

14. A metrology system comprising the substrate support system according to claim 12.

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