Substrate support

Abstract

A substrate support configured to support a substrate. The substrate support comprising a plurality of concentrically arranged clamping regions, wherein at least one extraction orifice is defined in each of the plurality of concentrically arranged clamping regions. The at least one extraction orifice is configured to extract fluid from the corresponding clamping region. A number of extraction orifices in the N+1 clamping region is greater than a number of extraction orifices in the N clamping region, N being an integer greater than or equal to 1. The at least one extraction orifice is in direct fluid communication with a corresponding extraction channel. The corresponding extraction channel in direct fluid communication with an extraction orifice in the N+1 clamping region is in direct fluid communication with an extraction channel corresponding to, and in direct fluid communication with, an extraction orifice in the N clamping region.

Description

SUBSTRATE SUPPORTCROSS-REFERENCE TO REEATED APPEICATIONS

[0001] This application claims priority of EP application 24188760.3 which was filed on 16 July 2024 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 metrology system comprising the substrate support, and a method of manufacturing the substrate support.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. There may be a plurality of through holes in the grooves extending to the substrate-facing side of the substrate support. The plurality of through holes enable fluid 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 besecured 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, a substrate support configured to support a substrate. The substrate support comprises a plurality of concentrically arranged clamping regions, wherein at least one extraction orifice is defined in each of the plurality of concentrically arranged clamping regions. The at least one extraction orifice is configured to extract fluid from the corresponding clamping region. A number of extraction orifices in the N+l clamping region is greater than a number of extraction orifices in the N clamping region, N being an integer greater than or equal to 1. The at least one extraction orifice is in direct fluid communication with a corresponding extraction channel. The corresponding extraction channel in direct fluid communication with an extraction orifice in the N+l clamping region is in direct fluid communication with an extraction channel corresponding to, and in direct fluid communication with, an extraction orifice in the N clamping region.

[0010] Also in accordance with the present invention, a metrology system comprising the substrate support.

[0011] Also in accordance with the present invention, a method of manufacturing the substrate support.

[0012] 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

[0013] 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 plan view of the fluid extraction system of the substrate support of Figure 2;Figure 5 depicts the arrangement of extraction orifices and extraction channels in region R of the substrate support of Figure;Figures 6A-E depict a warped substrate W being clamped to the substrate support 1 in sequence;Figure 7 depicts a cross-sectional view through A-A along a fluid flow path of Figure 4; Figures 8A-C depict a plan view of substrate supports 1 having different arrangements of sealing members;Figures 9A-B depict cross-sectional views through different arrangements of substrate support.

[0015] 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

[0016] 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).

[0017] 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.

[0018] 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 table (e.g., a support 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 table 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. The substrate table WT may optionally comprise a substrate support (not shown in Figure 1) constructed to hold the substrate W.

[0019] 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 ofoptical 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.

[0020] 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.

[0021] 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 fdl 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.

[0022] The lithographic apparatus may be of a type having two or more substrate tables WT (also named “dual stage”). In such “multiple stage” machine, the substrate tables 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 table WT while another substrate W on the other substrate table WT is being used for exposing a pattern on the other substrate W.

[0023] In addition to the substrate table WT, the lithographic apparatus may comprise a measurement stage (not shown 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 table WT is away from the projection system PS.

[0024] 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 table 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 deviceMA 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.

[0025] 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.

[0026] 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.

[0027] 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 be a part of or integral with the substrate table WT shown in Figure 1. 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).

[0028] 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.

[0029] 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.

[0030] 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 the substrate 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.

[0031] 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).

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The main body 10 defines a plurality of extraction openings 12, otherwise referred to as extraction orifices, through which the fluid is extracted.

[0036] 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 surface31, 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.

[0037] 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.

[0038] A pressure sensor (not shown 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.

[0039] A flow rate sensor (not shown in drawings) may be used to measure the flow rate of the fluid extracted via the extraction orifices 12. Various sensors for measuring the flow rate from the space below the substrate W are known.

[0040] For the present invention, the exact arrangement of the substrate support 1 is not particularly limited. For example, the exact arrangement of burls 20 and sealing member 40 in the substrate support 1 is not particularly limited.

[0041] It is desirable that when a substrate W is on the substrate support 1 it is secured or clamped such that it is relatively flat and not able to move undesirably. This can aid in ensuring that the lithography or inspection of the substrate W may be performed effectively. This can be challenging when the substrate W is highly warped. In other words, it can be difficult to clamp a substrate which has a warped topography, such as being bowl or saddle shaped.

[0042] One challenge associated with clamping warped substrates is the limitation in using the available negative pressure supply source, especially the available flow rate, to distribute the vacuum or negative pressure to the right location on top of the substrate support 1 to apply the necessary attractive force to pull down the warped substrate. An increased flow rate may be required to secure any regions of the substrate W which are still too distant from the substrate support 1 due to warpage. This may result in stress in the substrate W, which is undesirable as the substrate W may become damaged. Furthermore, there may be wear on the burls 20 due to lateral movement of the substrate W. One possible means to resolve this would be to use valves to control flow to be directed to the desired region of the substrate W. However, this adds complexity to the system and may take time to adjust the valve settings for each substrate W. A more passive solution is therefore desirable.

[0043] Figure 4 shows a plan view of a substrate support 1 configured to support a substrate W. In particular, Figure 4 provides an illustration of the arrangement of extraction orifices 12 and corresponding extraction channels 13. The full arrangement is only depicted for region R in Figure 4. The same arrangement shown in the segment of region R should be repeated a plurality of times to achieve a complete system around the substrate support 1. In the arrangement of Figure 4, the partialsystem shown in region R may be repeated 8 times. In other arrangements, the partial system may be repeated a greater or fewer number of times. Figure 5 provides an illustration of the arrangement of extraction orifices 12 and extraction channels 13 in region R of the substrate support 1 of Figure 4.

[0044] The extraction orifices 12 and extraction channels 13 are arranged to facilitate clamping of substrates W, independent of the shape of the substrates W (including symmetric and non-symmetric warpage). The arrangement may enable substrate flatness to be achieved without the complication of additional mechanics to push / pull down the substrate W.

[0045] The system of extraction orifices 12 and extraction channels 13 is configured to enable fluid to flow from a substrate-facing side of the substrate support 1 to a location remote from the substrate W. In other words, the extraction orifices 12 and extraction channels 13 are configured to extract fluid from a region between a substrate-facing surface (which may be the upper surface 11) of the main body 10 of the substrate support 1, and the substrate W, when the substrate W is on the substrate support 1. The substrate-facing surface is arranged to face a substrate W when the substrate W is placed on the substrate support 1.

[0046] The substrate support 1 comprises a plurality of concentrically arranged clamping regions Zl- Z5, which may be referred to as clamping zones. At least one extraction orifice 12 is defined in each of the plurality of clamping regions Z1-Z5. In other words, the extraction orifices 12 may be defined by the main body 10 of the substrate support 1 at locations such that in each clamping region Z1-Z5 on the substrate-facing surface at least one opening of an extraction orifice 12 is defined. The extraction orifices 12 are configured to extract fluid from the corresponding clamping region Z1-Z5. In other words, the extraction orifices 12 are arranged such that fluid may be extracted from a region between the clamping region Z1-Z5 where the extraction orifice 12 is disposed, and the substrate W.

[0047] A number of extraction orifices 12 in the N+l clamping region is greater than a number of extraction orifices in the N clamping region, N being an integer greater than or equal to 1. For example, the number of extraction orifices 12 in the third clamping region Z3 may be 32 which is greater than the number of extraction orifices 12, which may be 16, in the second clamping region Z2.

[0048] The N+l clamping region is disposed radially outward of the N clamping region, relative to a centre of the substrate support 1. The N+l clamping region is desirably adjacent to the N clamping region. In other words, the clamping regions Z1-Z5 may be concentrically arranged such that the first claiming region Z 1 is towards a centre of the substrate support 1 . Each subsequent clamping region Z2-Z5 is radially outward of the preceding clamping region Z1-Z4, such that the number of the clamping region increases towards the periphery of the substrate support 1. With this arrangement, the central clamping region may be considered to be the first clamping region Z 1. The next clamping region, which is adjacent and radially outward of the first clamping region Z1 may be considered to be the second clamping region Z2. This pattern continues until the most outward clamping region, which in the arrangement of Figure 4, is the fifth clamping region Z5. However, it should beunderstood that the number of clamping regions is not limited to exactly five. There may be more or fewer than five clamping regions. For example, there may be 3, 4 or 6 clamping regions.

[0049] Each extraction orifice 12 is in direct fluid communication with a corresponding extraction channel 13. The corresponding extraction channel 13 in direct fluid communication with an extraction orifice 12 in the N+l clamping region is in direct fluid communication with an extraction channel 13 corresponding to, and in direct fluid communication with, an extraction orifice 12 in the N clamping region. For example, as shown in Figure 5, the first extraction orifice 123 in the third clamping region Z3 is in direct fluid communication with a first corresponding extraction channel 133. The first corresponding extraction channel 133 is in direct fluid communication with a second extraction channel 132 corresponding to, and in direct fluid communication with, a second extraction orifice 122 in the second clamping region Z2. In other words, each extraction orifice 12 in the N+l clamping region is connected via a corresponding extraction channel 13 to an extraction channel 13 corresponding to an extraction orifice 12 in the N clamping region (recalling that N is an integer greater than or equal to 1).

[0050] With an arrangement of extraction orifices 12 and extraction channels 13 such as that of Figures 4 and 5, a supply interface 14 may be provided in the first clamping region Zl. The supply interface 14 is desirably connected to a negative pressure source (not shown). In this way, fluid in the clamping regions Z1-Z5 may be extracted by fluid flow in a generally radially inward direction as shown by arrow F in Figure 5. The above -de scribed arrangement may desirably prompt a sequential clamping of a substrate W to the substrate support 1. In other words, the substrate W may be secured to each clamping region Z 1-Z5 in turn in a passive manner, without requiring active control and valves. The substrate W may be secured to each clamping region Z1-Z5 in order from the first clamping region Zl, towards the centre of the substrate support 1, to the outermost clamping region, which is the fifth clamping region Z5 in the arrangement of Figures 4 and 5. This is beneficial because the fluid flow can provide an attractive force on the substrate W at each clamping region Z 1 - Z5 in sequence rather than flow being disbursed over an entirety of the substrate support 1 at any given time. In this way, with the same negative pressure supply, a high attractive force can be achieved in the active clamping region than if the flow were distributed over the entire sample support 1.

[0051] In particular, the negative pressure fluid flow may provide an attractive force to attract the substrate W to the substrate support 1 in the N clamping region, until the substrate W is within a predetermined distance of the substrate support 1 across the first clamping region Zl. Figures 6A-6E depict a warped substrate W being clamped to the substrate support 1 in sequence from the start of the clamping process in Figure 6A to the substrate W being clamped flat across all clamping regions Zl- Z5 in Figure 6E. For example, as shown in Figure 6A, the negative pressure source may be activated such that fluid flows through any extraction orifice 12 of the first clamping region Z 1 to the supply interface 14. This means that there is an attractive force between the centre of the substrate WC andthe substrate support 1 in the first clamping region Z 1. However, there is little or no attractive force between a periphery of the substrate WP and the substrate support 1, for example in the fourth clamping region Z4. Once the substrate W is within a predetermined distance of the substrate support 1 across the N clamping region, the negative pressure fluid flow will provide an attractive force to attract the substrate W to the substrate support 1 in the N+l clamping region. For example, as shown in Figure 6B, once the substrate W is within a predetermined distance of the substrate support 1 across the first clamping region Zl, the negative pressure fluid flow will be provided from extraction orifices 12 of the second clamping region Z2 towards the supply interface 14 to attract the substrate W to the substrate support 1 in the second clamping region Z2. This process may repeat until the substrate W is within a predetermined distance of the substrate support 1 across all clamping regions Z1-Z5, as shown in Figure 6E. In this way, the arrangement of extraction orifices 12 and extraction channels 13 such as that of Figures 4 and 5, may enable a substrate W to be securely clamped to the substrate support 1 in an effective and efficient manner, with a low risk of damage to the substrate W.

[0052] The extraction channels 13 are desirably arranged, as shown in Figure 4, to extend in a generally radial direction. In other words, the flow path of fluid from an extraction orifice 12 to the supply interface 14 desirably extends in a radially inward flow direction, as shown in Figure 5. This is in contrast to arrangements in which the channels may extend in a generally concentric direction. This arrangement is intended to provide a defined flow path which promotes the sequential clamping of the substrate 1 in the different clamping regions Z 1 -Z5.

[0053] Figure 7 provides a cross-sectional view through A-A along a fluid flow path of Figure 4 between a centre and a periphery of the substrate support 1. As shown in the arrangement of Figures 4, 5 and 7, each extraction orifice 12 in the N+l clamping region is desirably in fluid communication with a corresponding extraction orifice 12 in the N clamping region. In particular, the extraction orifice 12 in the N+l clamping region is in fluid communication, via an extraction channel 13, with one corresponding extraction orifice 12 in the N clamping region. For example, as shown in Figure 5, the first extraction orifice 123 in the third clamping region Z3 is in fluid communication with a second extraction orifice 122 in the second clamping region Z2. In particular, the first extraction orifice 123 and the second extraction orifice 122 are connected via the first corresponding extraction channel 133. In other words, each extraction orifice 12 in the N+l clamping region is connected via a corresponding extraction channel 13 to an extraction orifice 12 in the N clamping region (recalling that N is an integer greater than or equal to 1).

[0054] Each extraction orifice 12 in the N clamping region may be in fluid communication with more than one extraction orifice 12 in the N+l clamping region, N being an integer greater than or equal to 1. In other words, each extraction orifice 12 in the N clamping region is connected, via a corresponding extraction channel 13, to multiple extraction orifices 12 in the N+l clamping region. In other words, an extraction channel 13 extending from the N clamping region to the N+l clamping region may split into a plurality of extraction channels 13, which may optionally be referred to as sub-channels. Each extraction sub-channel branched from the extraction channel 13 may connect to a corresponding extraction orifice 12 of the N+l clamping region.

[0055] Desirably, as shown in the arrangement of Figures 4 and 5, the number of extraction orifice 12 in the M+l clamping region is desirably twice the number of the extraction orifice 12 in the M clamping region, M being an integer greater than 1. Each extraction orifice 12 in the M clamping region is in fluid communication, via an extraction channel 13, with two corresponding extraction orifices 12 in the M+l clamping region.

[0056] In alternative arrangements (not shown in the figures), each extraction channel 13 may split to form more than two sub-channels and / or only some extraction channels 13 may split to form multiple sub-channels.

[0057] As shown in Figure 7, the extraction channels 13 are desirably formed within the main body 10 of the substrate support 1. In an alternative arrangement, not shown, the extraction channels 13 may be formed outside the main body 10 of the substrate support 1. For example, the extraction channels 13 may be formed of conduits disposed below the main body 10 of the substrate support 1.

[0058] In a preferred arrangement, the sum of cross-sectional areas of all extraction channels in the N+l clamping region is within a predetermined channel area threshold range of the sum of cross - section areas of all extraction channels in the N clamping region. All extraction channels 13 in the N+l clamping region means all extraction channels 13 extending from the extraction orifices 12 of the N clamping region towards the N+l clamping region. All extraction channels 13 in the N+l clamping region means all extraction channels 13 extending from the extraction orifices 12 of the N+l clamping region towards the N+2 clamping region. The area of the extraction channel extending from the extraction orifices 12 of the N clamping region towards the N+l clamping region is measured in the main channel connected to the extraction orifice 12 of the N clamping region, prior to the extraction channel 13 splitting to the sub-channels which then connect to the extraction orifices 12 of N clamping region.

[0059] For example, in the arrangement of Figure 5, the sum of cross-sectional areas of all extraction channels AC4 of the fourth clamping region Z4 is within a predetermined channel area threshold range of the sum of the areas of the extraction channels AC3 in third clamping region Z3. In other words, the sum of cross-sectional areas of all extraction channels AC4 of the fourth clamping region Z4, which are connected to the first extraction orifices 123 of the third clamping region Z3 and extend towards the fourth clamping region Z4, is within a predetermined channel area threshold range of the sum of the areas of the extraction channels AC3, which are connected to the second extraction orifices 122 of the second clamping region Z2 and extend towards the third clamping region Z3.

[0060] A ratio between the sum of cross-sectional areas of all extraction channels in the N+l clamping region and a sum of cross-section areas of all extraction channels in the N clamping region is within a predetermined channel area ratio range. The predetermined channel area ratio range is preferably between 0.75 and 1.25, more preferably between 0.8 and 1.2, yet more preferably thepredetermined channel area ratio is 1. In this way, the flow may be appropriately distributed in the different clamping regions Z 1 -Z5 during the different stages of the sequential clamping of the substrate W. In particular, the attractive force is distributed evenly despite being applied across fewer extraction orifices 12 in a lower number, more central, clamping region than in a higher number, more peripheral, clamping region.

[0061] In a preferred arrangement, the sum of cross-sectional areas of all extraction orifices in the N+l clamping region is within a predetermined orifice area threshold range of the sum of cross - section areas of all extraction channels extending from the extraction orifices 12 of the N clamping region towards the N+l clamping region. In other words, the sum of cross-sectional areas of all extraction orifices in the N+l clamping region is within a predetermined orifice area threshold range of the sum of cross-section areas of all extraction channels in the N+l clamping region. The area of the extraction channel extending from the extraction orifices 12 of the N clamping region towards the N+l clamping region is measured in the main channel connected to the extraction orifice 12 of the N clamping region, prior to the extraction channel 13 splitting to the sub-channels which then connect to the extraction orifices 12 of N clamping region.

[0062] For example, in the arrangement of Figure 5, the sum of the areas of the first extraction orifices AO3 in the third clamping region Z3 is within a predetermined orifice area threshold range of the sum of the areas of the extraction channels AC3 extending from the second extraction orifices 122 of the second clamping region Z2 towards the third clamping region Z3. In other words, the sum of the areas of the first extraction orifices AO3 in the third clamping region Z3 is within a predetermined orifice area threshold range of the sum of the areas of the extraction channels AC3 which are connected to the second extraction orifices 122 of the second clamping region Z2 and extend towards the third clamping region Z3.

[0063] A ratio between the sum of cross-sectional areas of all extraction orifices in the N+l clamping region and a sum of cross-section areas of all extraction channels extending from the extraction orifices of the N clamping region towards the N+l clamping region is within a predetermined orifice area ratio range. The predetermined orifice area ratio range is preferably between 0.75 and 1.25, more preferably between 0.8 and 1.2, yet more preferably the predetermined orifice area ratio is 1. In this way, the flow may be appropriately distributed in the different clamping regions Z 1 -Z5 during the different stages of the sequential clamping of the substrate W. In particular, the attractive force is distributed evenly despite being applied across fewer extraction orifices 12 in a lower number, more central, clamping region than in a higher number, more peripheral, clamping region.

[0064] As described above in reference to Figures 4 and 5, the substrate support 1 may comprise a supply interface 14, which is desirable provided in the first clamping region Zl. The supply orifice 14 is connected to a negative pressure source (not shown). In other words, a negative pressure is provided through the supply orifice 14 such that fluid may flow through the extraction orifices 12 and corresponding extraction channels 13 to the supply orifice 14. The supply interface 14 is preferablydisposed at a centre of the substrate support 1. In this way, an even flow may be more readily achieved across the substrate support 1.

[0065] The supply interface 14 may also act as an extraction orifice. In other words, the supply interface 14 may be a through hole extending to a substrate-facing surface of the main body 10 of the substrate support 1. Alternatively, an extraction orifice 12 may be provided at a centre of the substrate support 1, in the first clamping region Zl.

[0066] As shown in Figure 4, the substrate support 1 comprises a plurality of extraction channels 141 in direct fluid communication with the supply interface 14. In other words, a plurality of extraction channels 141 are directly connected to the supply interface 14. Each of the plurality of extraction channels 141 in direct fluid communication with the supply interface 14 extends in a different direction radially extending from the supply interface 14. The different directions are at even intervals radially around the supply interface 14.

[0067] Each of the plurality of extraction channels 141 in direct fluid communication with the supply interface 14 corresponds to a corresponding branch of extraction channels 13 and extraction orifices 12 which are in fluid communication. Each branch provides a flow path from the extraction orifices 12 in that branch to the extraction channel 141 of that branch which is in direct contact with the supply interface 14. The region R of Figure 4 and 5 includes one branch extending from the supply interface 14. As shown by Figure 4, in a preferred arrangement, each branch is in fluid communication with the other branches only at the supply interface 14.

[0068] The number of branches in the arrangement of Figure 4 may be 8. The number of branches may alternatively be greater or less than 8. For example, the number of branches may be between 2 and 20, preferably between 3 and 16, more preferably between 4 and 10.

[0069] The substrate support 1 may optionally further comprise at least one sealing member 40. The sealing member 40 may be a physical boundary such as a wall, as described above with reference to Figure 3. The sealing member 40 may disposed on a substrate-facing surface of the substrate support 1. The substrate-facing surface is a surface (e.g., the upper surface 11) of the main body 10 of the substrate support 1. The substrate-facing surface is configured to face the substrate W during use. The at least one sealing member 40 is configured to restrict a flow of fluid over the substrate -facing surface. The shape and number of sealing members 40 is not limited and may be provided based on the intended application. For example, a particular arrangement of sealing members 40 may be particularly suited to a particular shape of substrate W.

[0070] Figures 8A-C provide a plan view of substrate supports 1 having different arrangements of sealing members 40. In particular, Figure 8 A shows an arrangement including only circumferentially extending sealing members 40. Figure 8B shows an arrangement including only radially extending sealing members 41. Figure 8C shows an arrangement including a combination of circumferentially extending sealing members 40 and radially extending sealing members 41.

[0071] In the arrangements of Figures 8A and 8C, there is at least one sealing member 40 disposed between different clamping regions Z1-Z5. In this way, the at least one sealing member 40 is configured to restrict a flow of fluid over the substrate-facing surface between different clamping regions Z1-Z5. The at least one sealing member 40 is disposed at a border between each of the different circumferentially arranged clamping regions Z1-Z5. In the arrangements of Figures 8A and 8C, the at least one sealing member 40 extends in a circumferential direction around a centre C of the substrate support 1. In the arrangements of Figures 8A and 8C, the at least one sealing member 40 extends continuously in a circumferential direction around the centre C of the substrate support 1.

[0072] In the arrangements of Figures 8A and 8C there is a plurality of sealing members 40 and each boundary between adjacent clamping zones has a corresponding sealing member 40. This is a preferred arrangement, because with this arrangement the attractive force of fluid flow is more contained within each clamping region while that clamping region is active. At a time in the sequence when the substrate W is being attracted to move closer to the substrate support 1, the fluid flow is mainly, or entirely, though extraction orifices 12 within that clamping region. In arrangements having sealing members 40 at the borders of the clamping regions Z1-Z5, a likelihood of the attractive force in the active clamping region being reduced by leakage of fluid flow to another clamping region on the substrate-facing surface is reduced. In alternative arrangements (not shown), there may be sealing members 40 at boundaries of only some of the clamping regions. Concentrically arranged sealing members 40 may be beneficial when clamping substrates W with rotationally symmetrical warpage.

[0073] In the arrangements of Figures 8B and 8C, at least one sealing member 41 extends in a radial direction of the substrate support 1. In particular, the at least one sealing member 41 comprises a plurality of sealing members 41.

[0074] Each of the plurality of sealing members 41 of the arrangement of Figure 8B extends in a different radial direction. In the arrangement of Figure 8B, the at least one sealing member 41 extends continuously from a centre C of the substrate support 1 to a periphery of the substrate support 1. Radially arranged sealing members 41 may be beneficial when clamping substrates W with asymmetrical warpage.

[0075] As shown for example in the arrangement of Figure 8C, the at least one sealing member 41 may include sealing members 41 extending radially outward from the centre C of the substrate support 1. Additionally or alternatively, the at least one sealing member 41 may include sealing members 41 extending radially between concentrically arranged sealing members 40. In this way, smaller regions may be formed where the fluid flow may be contained. An arrangement such as this, having a combination of concentric sealing members 40 and radial sealing members 41, may be suited to clamping of substrates W warped to any shape.

[0076] Figures 9A and 9B provide cross-sectional views through different arrangements of substrate support 1. Figure 9A illustrates a single-sided substrate support 1 having a substrate -facing surface. Figure 9B illustrates a double-sided substrate support 1 having two surfaces disposed on opposingsides of the main body 10 of the substrate support 1. One of the two surfaces is configured to act as the substrate-facing surface. The other of the two surfaces may be configured to support the substrate support 1 on a structure, for example a substrate table WT. In other words, burls 20 and / or sealing members 40 may be formed on the two opposing surfaces of the substrate support 1. Similarly, extraction orifices 12 may optionally be defined to have openings on both of the opposing sides of the main body 10 of the substrate support 1. On the substrate-facing surface, the extraction orifices 12 may be configured to aid in attracting the substrate W to the substrate support 1 by flow of fluid. Whereas, on the opposing surface, the extraction orifices 12 may be configured to aid in attracting the substrate-support 1 to the substrate table WT by flow of fluid.

[0077] In the arrangements of Figures 9A and 9B, extraction orifices 12 and extraction channels 13 are formed in the main body 10 of the substrate support 1. Furthermore, in the arrangement of Figure 9B, a conditioning channel 15 is also defined. The conditioning channel 15 may be configured such that fluid may be provided to thermally condition the substrate support 1.

[0078] The substrate support 1, for example as shown in Figures 9A-B may be manufactured by any suitable method. For example, the substrate support 1 may be manufactured by providing a plurality of layers. The layers may comprise plates. Grooves and / or holes may be formed in some of the layers. The layers may be bonded together to form the substrate support 1. In particular, the layers may be arranged such that the grooves and / or holes in the layers align to form channels and / or orifices in the main body 10 of the substrate support 1. The channels and / or orifices may correspond to the extraction orifices 12 and / or extraction channels 13. Any suitable method may be used. For example, the grooves and / or holes may be defined by lasering or computer numerical control drilling. The bonding may comprises forming one or more of an anodic bond, a glass frit bond, a thermal bond, and diffusion bond.

[0079] Structures on the substrate-facing surface, for example burls 20 and sealing member 40 may be formed by any suitable method - for example, by using a process such as electrical discharge machining, laser structuring or sand blasting. A high wear resistance coating, e.g., DLC, diamond or CrN, may be provided to protect exposed surfaces of the substrate support 1. For example, the burls 20 may be provided with the high wear resistance coating.

[0080] 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.

[0081] 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 alternativeapplications, 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.

[0082] 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.

[0083] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described.

[0084] 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.

[0085] Embodiments include the following numbered clauses:1. A substrate support configured to support a substrate, the substrate support comprising: a plurality of concentrically arranged clamping regions, wherein at least one extraction orifice is defined in each of the plurality of concentrically arranged clamping regions, the at least one extraction orifice configured to extract fluid from the corresponding clamping region; a number of extraction orifices in the N+l clamping region is greater than a number of extraction orifices in the N clamping region, N being an integer greater than or equal to 1; the at least one extraction orifice is in direct fluid communication with a corresponding extraction channel; the corresponding extraction channel in direct fluid communication with an extraction orifice in the N+l clamping region is in direct fluid communication with an extraction channel corresponding to, and in direct fluid communication with, an extraction orifice in the N clamping region.2. The substrate support according to clause 1, wherein each extraction orifice in the N+l clamping region is in fluid communication with a corresponding extraction orifice extraction orifice in the N clamping region.3. The substrate support according to clause 1 or 2, wherein each extraction orifice in the N+l clamping region is in fluid communication with more than one extraction orifice extraction orifice in the N+2 clamping region.4. The substrate support according to any preceding clause, wherein the number of extraction orifice in the M+l clamping region is twice the number of the extraction orifice in the M clamping region, M being an integer greater than 1.5. The substrate support according to any preceding clause, wherein the sum of cross-sectional areas of all extraction channels in the N+l clamping region is within a predetermined channel area threshold range of the sum of cross-section areas of all extraction channels in the N clamping region.6. The substrate support according to any preceding clause, wherein a ratio between the sum of cross-sectional areas of all extraction channels in the N+l clamping region and a sum of cross-section areas of all extraction channels in the N clamping region is within a predetermined channel area ratio range.7. The substrate support according to clause 6, wherein the predetermined channel area ratio range is between 0.75 and 1.25.8. The substrate support according to clause 7, wherein the predetermined channel area ratio is 1.9. The substrate support according to any preceding clause, wherein the sum of cross-sectional areas of all extraction orifices in the N+l clamping region is within a predetermined orifice area threshold range of the sum of cross-section areas of all extraction channels extending from the extraction orifices of the N clamping region towards the N+l clamping region.10. The substrate support according to any preceding clause, wherein a ratio between the sum of cross-sectional areas of all extraction orifices in the N+l clamping region and a sum of cross -section areas of all extraction channels extending from the extraction orifices of the N clamping region towards the N+l clamping region is within a predetermined orifice area ratio range.11. The substrate support according to clause 10, wherein the predetermined orifice area ratio range is between 0.75 and 1.25.12. The substrate support according to clause 11, wherein the predetermined orifice area ratio is 1.13. The substrate support according to any preceding clause, wherein the N+l clamping region is disposed radially outward of the N clamping region, relative to a centre of the substrate support.14. The substrate support according to any preceding clause, wherein the first clamping region is disposed at a centre of the substrate support.15. The substrate support according to any preceding clause, wherein the first clamping region defines a supply interface.16. The substrate support according to clause 15, wherein the supply interface is disposed at a centre of the substrate support.17. The substrate support according to clause 15 or 16, wherein the supply interface is an extraction orifice.18. The substrate support according to clause 15 or 16, wherein the supply interface is configured to direct fluid away from the substrate.19. The substrate support according to any of clauses 15 to 18, wherein the supply orifice is connected to a negative pressure source.20. The substrate support according to any of clauses 15 to 19, further comprising a plurality of extraction channels in direct fluid communication with the supply interface.21. The substrate support according to clause 20, wherein each of the plurality of extraction channels in direct fluid communication with the supply interface extends in a different direction radially extending from the supply interface.22. The substrate support according to clause 21, wherein the different directions are at even intervals radially around the supply interface.23. The substrate support according to any of clauses 20 to 22, wherein each of the plurality of extraction channels in direct fluid communication with the supply interface corresponds to a corresponding branch of extraction channels and extraction orifices, of a plurality of clamping regions, which are in fluid communication.24. The substrate support according to clause 23, wherein each corresponding branch is in fluid communication with the other branches only at the supply interface.25. The substrate support according to any preceding clause, further comprising at least one sealing member disposed on a substrate facing surface of the substrate support configured to face the substrate, wherein the at least one sealing member is configured to restrict a flow of fluid over the substrate facing surface.26. The substrate support according to clause 25, wherein the at least one sealing is disposed between different clamping regions, wherein the at least one sealing member is configured to restrict a flow of fluid over the substrate facing surface between different clamping regions.27. The substrate support according to clause 25 or 26, wherein the at least one sealing member is disposed at a border between each of the different circumferentially arranged clamping regions, wherein the at least one sealing member is configured to restrict a flow of fluid over the substrate facing surface between different clamping regions.28. The substrate support according to any of clauses 25 to 27, wherein the at least one sealing member extends in a circumferential direction around a centre of the substrate support.29. The substrate support according to clause 28, wherein the at least one sealing member extends continuously in a circumferential direction around a centre of the substrate support.30. The substrate support according to any of clauses 25 to 29, wherein the at least one sealing member extends in a radial direction of the substrate support.31. The substrate support according to clause 30, wherein the at least one sealing member extends continuously from a centre of the substrate support to a periphery of the substrate support.32. The substrate support according to any of clauses 25 to 31, wherein the at least one sealing member comprises a plurality of sealing members.33. The substrate support according to any of clauses 15 to 32, wherein the extraction orifices and extraction channels are arranged such that, when a negative pressure fluid flow is applied through the supply interface, the negative pressure fluid flow will provide an attractive force to attract the substrate to the substrate support in the N clamping region, until the substrate is within a predetermined distance of the substrate support across the first clamping region; and once the substrate is within a predetermined distance of the substrate support across the N clamping region, the negative pressure fluid flow will provide an attractive force to attract the substrate to the substrate support in the N+l clamping region.34. A metrology system comprising the substrate support according to any preceding clause.35. A method of manufacturing the substrate support of any of clauses 1 to 33, comprising providing a plurality of layers; defining grooves and / or holes corresponding to the extraction orifices and / or extraction channels in one or more of the plurality of layers; and bonding the layers together.36. The method of clause 35, wherein the bonding comprises forming one or more of an anodic bond, a glass frit bond, and a thermal bond.37. The method of clause 35 or 36, wherein the defining grooves and / or holes comprises lasering or computer numerical control drilling.

Claims

CLAIMS1. A substrate support configured to support a substrate, the substrate support comprising: a plurality of concentrically arranged clamping regions, wherein at least one extraction orifice is defined in each of the plurality of concentrically arranged clamping regions, the at least one extraction orifice configured to extract fluid from the corresponding clamping region; a number of extraction orifices in the N+l clamping region is greater than a number of extraction orifices in the N clamping region, N being an integer greater than or equal to 1 ; the at least one extraction orifice is in direct fluid communication with a corresponding extraction channel; the corresponding extraction channel in direct fluid communication with an extraction orifice in the N+l clamping region is in direct fluid communication with an extraction channel corresponding to, and in direct fluid communication with, an extraction orifice in the N clamping region.

2. The substrate support according to claim 1, wherein each extraction orifice in the N+l clamping region is in fluid communication with a corresponding extraction orifice extraction orifice in the N clamping region, and / or wherein each extraction orifice in the N+l clamping region is in fluid communication with more than one extraction orifice extraction orifice in the N+2 clamping region, and / or wherein the number of extraction orifice in the M+l clamping region is twice the number of the extraction orifice in the M clamping region, M being an integer greater than 1 .

3. The substrate support according to claim 1 or 2, wherein the sum of cross-sectional areas of all extraction channels in the N+l clamping region is within a predetermined channel area threshold range of the sum of cross-section areas of all extraction channels in the N clamping region, and / or wherein a ratio between the sum of cross-sectional areas of all extraction channels in the N+l clamping region and a sum of cross-section areas of all extraction channels in the N clamping region is within a predetermined channel area ratio range, and / or wherein the sum of cross-sectional areas of all extraction orifices in the N+l clamping region is within a predetermined orifice area threshold range of the sum of cross-section areas of all extraction channels extending from the extraction orifices of the N clamping region towards the N+l clamping region, and / or wherein a ratio between the sum of cross-sectional areas of all extraction orifices in the N+l clamping region and a sum of cross-section areas of all extraction channels extending from the extraction orifices of the N clamping region towards the N+l clamping region is within a predetermined orifice area ratio range.

4. The substrate support according to claim 3, wherein the predetermined channel area ratio range is between 0.75 and 1.25, desirably wherein the predetermined channel area ratio is 1, and / or wherein the predetermined orifice area ratio range is between 0.75 and 1.25, desirably wherein the predetermined orifice area ratio is 1 .

5. The substrate support according to any of the preceding claims, wherein the N+l clamping region is disposed radially outward of the N clamping region, relative to a centre of the substrate support, and / or wherein the first clamping region is disposed at a centre of the substrate support, and / or wherein the first clamping region defines a supply interface.

6. The substrate support according to claim 5, wherein the supply interface is disposed at a centre of the substrate support, and / or wherein the supply interface is an extraction orifice, and / or wherein the supply interface is configured to direct fluid away from the substrate, and / or wherein the supply orifice is connected to a negative pressure source, and / or further comprising a plurality of extraction channels in direct fluid communication with the supply interface .

7. The substrate support according to claim 6, wherein each of the plurality of extraction channels in direct fluid communication with the supply interface extends in a different direction radially extending from the supply interface, desirably wherein the different directions are at even intervals radially around the supply interface.

8. The substrate support according to claim 6 or 7, wherein each of the plurality of extraction channels in direct fluid communication with the supply interface corresponds to a corresponding branch of extraction channels and extraction orifices, of a plurality of clamping regions, which are in fluid communication, desirably wherein each corresponding branch is in fluid communication with the other branches only at the supply interface.

9. The substrate support according to any of the preceding claims, further comprising at least one sealing member disposed on a substrate facing surface of the substrate support configured to face the substrate, wherein the at least one sealing member is configured to restrict a flow of fluid over the substrate facing surface, desirably wherein the at least one sealing is disposed between different clamping regions, wherein the at least one sealing member is configured to restrict a flow of fluid over the substrate facing surface between different clamping regions, and / or desirably wherein the at least one sealing member is disposed at a border between each of the different circumferentially arranged clamping regions, wherein the at least one sealing member is configured to restrict a flow of fluid over the substrate facing surface between different clamping regions.

10. The substrate support according to claim 9, wherein the at least one sealing member extends in a circumferential direction around a centre of the substrate support, desirably wherein the at least one sealing member extends continuously in a circumferential direction around a centre of the substrate support.

11. The substrate support according to claim 9 or 10, wherein the at least one sealing member extends in a radial direction of the substrate support, and / or wherein the at least one sealing member comprises a plurality of sealing members, desirably wherein the at least one sealing member extends continuously from a centre of the substrate support to a periphery of the substrate support.

12. The substrate support according to any of claims 5-11, wherein the extraction orifices and extraction channels are arranged such that, when a negative pressure fluid flow is applied through the supply interface, the negative pressure fluid flow will provide an attractive force to attract the substrate to the substrate support in the N clamping region, until the substrate is within a predetermined distance of the substrate support across the first clamping region; and once the substrate is within a predetermined distance of the substrate support across the N clamping region, the negative pressure fluid flow will provide an attractive force to attract the substrate to the substrate support in the N+l clamping region.

13. A metrology system comprising the substrate support according to any of the preceding claims.

14. A method of manufacturing the substrate support of any of claims 1-12, comprising providing a plurality of layers; defining grooves and / or holes corresponding to the extraction orifices and / or extraction channels in one or more of the plurality of layers; and bonding the layers together.

15. The method of claim 14, wherein the bonding comprises forming one or more of an anodic bond, a glass frit bond, and a thermal bond, and / or wherein the defining grooves and / or holes comprises lasering or computer numerical control drilling.

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