Fluid handling structure, lithographic apparatus, method of controlling a fluid handling structure, method of controlling a lithographic apparatus and method of manufacturing a semiconductor device

Abstract

Disclosed herein is a fluid handling structure for a lithographic apparatus, wherein the fluid handling structure is configured to at least partly confine a liquid to an immersion space between a final optical element of a projection system of the lithographic apparatus and a substrate onto which the projection system of the lithographic apparatus is configured to project a patterned beam, the fluid handling structure comprising: a plurality of channels configured to supply fluid towards the substrate and / or extract fluid away from the substrate; a flow adjuster configured to move relative to the channels so as to partially block the channels; an actuation device configured to move the flow adjuster relative to the channels; and a control system configured to control the actuation device so as to control partial blocking of the channels by the flow adjuster.

Description

FLUID HANDLING STRUCTURE, LITHOGRAPHIC APPARATUS, METHOD OF CONTROLLING A FLUID HANDLING STRUCTURE, METHOD OF CONTROLLING A LITHOGRAPHIC APPARATUS AND METHOD OF MANUFACTURING A SEMICONDUCTOR DEVICECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 23185828.3 which was filed on 17 July 2023 and which incorporated herein in its entirety by reference.FIELD

[0002] The present invention relates to a fluid handling structure, a lithographic apparatus, a method of controlling a fluid handling structure, a method of controlling a lithographic apparatus and a method of manufacturing a semiconductor device.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). Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion at one time, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a given direction (the "scanning" -direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.

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

[0006] The immersion fluid may be confined to a localized area, referred to as an immersion space, between a liquid confinement structure of the lithographic apparatus and the substrate by a fluidhandling system. The fluid handling system may be an assembly comprising a number of component parts, some such parts having complicated and intricate structures. In particular, the fluid handling system provides an intricate system of flow channels for the fluid provided to the immersion space.SUMMARY

[0007] According to a first aspect of the invention, there is provided a fluid handling system for a lithographic apparatus, the fluid handling system comprising: a fluid handling structure configured to at least partly confine a liquid to an immersion space between a final optical element of a projection system of the lithographic apparatus and a substrate onto which the projection system of the lithographic apparatus is configured to project a patterned beam, the fluid handling structure comprising: a plurality of channels configured to supply fluid towards the substrate and / or extract fluid away from the substrate; a flow adjuster configured to move relative to the channels so as to partially block the channels, thereby partially blocking flow through the channels; and an actuation device configured to move the flow adjuster relative to the channels; and a control system configured to control the actuation device so as to control partial blocking of the channels by the flow adjuster.

[0008] According to a second aspect of the invention, there is provided a lithographic apparatus comprising: a projection system configured to project a patterned beam onto a substrate and having a final optical element; a substrate support configured to support the substrate; the fluid handling system.

[0009] According to a third aspect of the invention, there is provided a method of controlling a fluid handling system for a lithographic apparatus, comprising a fluid handling structure configured to at least partly confine a liquid to an immersion space between a final optical element of a projection system of the lithographic apparatus and a substrate onto which the projection system of the lithographic apparatus is configured to project a patterned beam, the method comprising: supplying fluid towards the substrate and / or extracting fluid away from the substrate through a plurality of channels of the fluid handling structure; and controlling an actuation device to move a flow adjuster relative to channels so as to control partial blocking of the channels by the flow adjuster.

[0010] According to a fourth aspect of the invention, there is provided a method of controlling a lithographic apparatus, the method comprising: moving a substrate along a route comprising scanning movements; andthe method of controlling a fluid handling system for the lithographic apparatus, wherein the actuation device is controlled dependent on the scanning movements.

[0011] According to a fifth aspect of the invention, there is provided a method of manufacturing a semiconductor device, the method comprising the method of controlling a fluid handling system for a lithographic apparatus.

[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, are described in detail below with reference to the accompanying drawings.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:

[0014] Figure 1 depicts the schematic overview of the lithographic apparatus;

[0015] Figures 2a, 2b, 2c and 2d each depict, in cross section, two different versions of a fluid handling system with different features illustrated on the left hand side and the right hand side of each version, which may extend around the complete circumference;

[0016] Figure 3 schematically illustrates, in cross-section, a flow adjuster of a fluid handling system;

[0017] Figures 4 and 5 schematically illustrate, with a side on view, a function of a flow adjuster;

[0018] Figure 6 schematically illustrates a top view of a flow adjuster;

[0019] Figure 7 schematically illustrates a flow adjuster applied to a fluid handling structure;

[0020] Figures 8-11 schematically illustrate alternative shapes of apertures and channels;

[0021] Figures 12 and 13 schematically illustrate an effect of a flow adjuster on the flow area of channels;

[0022] Figure 14 schematically illustrates a side view of a flow adjuster;

[0023] Figure 15 schematically illustrates a top view of a flow adjuster;

[0024] Figure 16 schematically illustrates a flow adjuster applied to a fluid handling structure;

[0025] Figures 17-19 schematically illustrate a function of a flow adjuster;

[0026] Figures 20 and 21 schematically illustrate an effect of movement of a flow adjuster within a fluid handling structure;

[0027] Figure 22 schematically illustrates a cross-sectional view of a flow adjuster within a fluid handling structure;

[0028] Figure 23 schematically illustrates a flow adjuster partially blocking channels of a fluid handling structure;

[0029] Figures 24-27 schematically illustrate an effect of moving a flow adjuster on the flow area of different channels;

[0030] Figure 28 schematically illustrates a flow adjuster partially blocking channels of a fluid handling structure;

[0031] Figure 29 schematically illustrates a side on view of the flow adjuster of Figure 28;

[0032] Figure 30 schematically illustrates an alternative position of a flow adjuster compared to that shown in Figure 28;

[0033] Figures 31-33 schematically illustrate alternative arrangements of a flow adjuster; and

[0034] Figures 34-36 schematically illustrate alternative structural configurations of a flow adjuster.

[0035] 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 apparatus 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

[0036] 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 365, 248, 193, 157 or 126 nm).

[0037] 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.

[0038] Figure 1 schematically depicts a lithographic apparatus. The lithographic apparatus includes an illumination system (also referred to as illuminator) IL configured to condition a radiation beam B (e.g., UV radiation or DUV radiation), a mask support (e.g., a mask table) MT 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) 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. A controller 500 controls the overall operation of the apparatus. Controller 500 may be a centralised control system or a system of multiple separate sub-controllers within various sub-systems of the lithographic apparatus.

[0039] 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 varioustypes 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.

[0040] 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.

[0041] The lithographic apparatus is 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 a space 11 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.

[0042] 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.

[0043] In addition to the substrate support WT, the lithographic apparatus may comprise a measurement stage (not depicted in figures). 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.

[0044] 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 IF, 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 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.

[0045] To clarify the invention, 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 axis is orthogonal to the other two axis. 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.

[0046] Immersion techniques have been introduced into lithographic systems to enable improved resolution of smaller features. In an immersion lithographic apparatus, a liquid layer of immersion liquid having a relatively high refractive index is interposed in the space 11 between a projection system PS of the apparatus (through which the patterned beam is projected towards the substrate W) and the substrate W. The immersion liquid covers at least the part of the substrate W under a final element of the projection system PS. Thus, at least the portion of the substrate W undergoing exposure is immersed in the immersion liquid.

[0047] In commercial immersion lithography, the immersion liquid is water. Typically the water is distilled water of high purity, such as Ultra-Pure Water (UPW) which is commonly used in semiconductor fabrication plants. In an immersion system, the UPW is often purified and it may undergo additional treatment steps before supply to the space 11 as immersion liquid. Other liquids with a high refractive index can be used besides water as the immersion liquid, for example: a hydrocarbon, such as a fluorohydrocarbon; and / or an aqueous solution. Further, other fluids besides liquid have been envisaged for use in immersion lithography.

[0048] In this specification, reference will be made in the description to localized immersion in which the immersion liquid is confined, in use, to the space 11 between the final element 100 and a surface facing the final element 100. The facing surface is a surface of substrate W or a surface of the supporting stage (or substrate support WT) that is co-planar with the surface of the substrate W. (Please note that reference in the following text to surface of the substrate W also refers in addition or in the alternative to the surface of the substrate support WT, unless expressly stated otherwise; and vice versa). A fluid handling structure 12 present between the projection system PS and the substrate support WT is used to confine the immersion liquid to the space 11. The space 11 filled by the immersion liquid is smaller in plan than the top surface of the substrate W and the space 11 remainssubstantially stationary relative to the projection system PS while the substrate W and substrate support WT move underneath.

[0049] Other immersion systems have been envisaged such as an unconfined immersion system (a so-called ’All Wet’ immersion system) and a bath immersion system. In an unconfined immersion system, the immersion liquid covers more than the surface under the final element 100. The liquid outside the space 11 is present as a thin liquid film. The liquid may cover the whole surface of the substrate W or even the substrate W and the substrate support WT co-planar with the substrate W. In a bath type system, the substrate W is fully immersed in a bath of immersion liquid.

[0050] The fluid handling structure 12 is a structure which supplies the immersion liquid to the space 11, removes the immersion liquid from the space 11 and thereby confines the immersion liquid to the space 11. It includes features which are a part of a fluid supply system. The arrangement disclosed in PCT patent application publication no. WO 99 / 49504 is an early fluid handling structure comprising pipes which either supply or recover the immersion liquid from the space 11 and which operate depending on the relative motion of the stage beneath the projection system PS. In more recent designs, the fluid handling structure extends along at least a part of a boundary of the space 11 between the final element 100 of the projection system PS and the substrate support WT or substrate W, so as to in part define the space 11.

[0051] The fluid handing structure 12 may have a selection of different functions. Each function may be derived from a corresponding feature that enables the fluid handling structure 12 to achieve that function. The fluid handling structure 12 may be referred to by a number of different terms, each referring to a function, such as barrier member, seal member, fluid supply system, fluid removal system, liquid confinement structure, etc..

[0052] In an embodiment, immersion liquid is used as the immersion fluid. In that case the fluid handling structure 12 may be a liquid handling system. In reference to the aforementioned description, reference in this paragraph to a feature defined with respect to fluid may be understood to include a feature defined with respect to liquid.

[0053] A lithographic apparatus has a projection system PS. During exposure of a substrate W, the projection system PS projects a beam of patterned radiation onto the substrate W. To reach the substrate W, the path of the radiation beam B passes from the projection system PS through the immersion liquid confined by the fluid handling structure 12 between the projection system PS and the substrate W. The projection system PS has a lens element, the last in the path of the beam, which is in contact with the immersion liquid. This lens element which is in contact with the immersion liquid may be referred to as ‘the last lens element’ or “the final element”. The final element 100 is at least partly surrounded by the fluid handling structure 12. The fluid handling structure 12 may confine the immersion liquid under the final element 100 and above the facing surface.

[0054] Figures 2a, 2b, 2c and 2d show different features which may be present in variations of a fluid handling system. The designs may share some of the same features as Figures 2a, 2b, 2c and 2dunless described differently. The features described herein may be selected individually or in combination as shown or as required. The figures depict different versions of a fluid handling system with different features illustrated on the left hand side and the right hand side, which may extend around the complete circumference. Thus, for example, the fluid handling system may have the same features extending around the complete circumference. For example, the fluid handling system may have only the features of the left hand side of Figure 2a, or the right hand side of Figure 2a, or the left hand side of Figure 2b, or the right hand side of Figure 2b, or the left hand side of 2c, or the right hand side of 2c, or the left hand side of 2d, or the right hand side of 2d. Alternatively, the fluid handling system may be provided with any combination of features from these figures at different locations around the circumference. The fluid handling system may comprise the fluid handling structure 12 as described in the variations below.

[0055] Figure 2a shows a fluid handling structure 12 around the bottom surface of the final element 100. The final element 100 has an inverted frusto-conical shape. The frusto-conical shape having a planar bottom surface and a conical surface. The frusto-conical shape protrudes from a planar surface and having a bottom planar surface. The bottom planar surface is the optically active portion of the bottom surface of the final element 100, through which the radiation beam B may pass. The final element 100 may have a coating 30. The fluid handling structure 12 surrounds at least part of the frusto-conical shape. The fluid handling structure 12 has an inner-surface which faces towards the conical surface of the frusto-conical shape. The inner-surface and the conical surface may have complementary shapes. A top surface of the fluid handling structure 12 may be substantially planar. The fluid handling structure 12 may fit around the frusto-conical shape of the final element 100. A bottom surface of the fluid handling structure 12 may be substantially planar and in use the bottom surface may be parallel with the facing surface of the substrate support WT and / or substrate W. Thus, the bottom surface of the fluid handling structure 12 may be referred to as a surface facing the surface of the substrate W. The distance between the bottom surface and the facing surface may be in the range of 20 to 500 micrometers, desirably in the range of 70 to 200 micrometers.

[0056] The fluid handling structure 12 extends closer to the facing surface of the substrate W and substrate support WT than the final element 100. The space 11 is therefore defined between the inner surface of the fluid handling structure 12, the planar surface of the frusto-conical portion and the facing surface. During use, the space 11 is filled with immersion liquid. The immersion liquid fills at least part of a buffer space between the complementary surfaces between the final element 100 and the fluid handling structure 12, in an embodiment at least part of the space between the complementary inner-surface and the conical surface.

[0057] The immersion liquid is supplied to the space 11 through an opening formed in a surface of the fluid handling structure 12. The immersion liquid may be supplied through a supply opening 20 in the inner-surface of the fluid handling structure 12. Alternatively or additionally, the immersion liquid is supplied from an under supply opening 23 (which may be referred to as water supplyopening) formed in the bottom surface of the fluid handling structure 12. The under supply opening 23 may surround the path of the radiation beam B and it may be formed of a series of openings in an array or a single slit. The immersion liquid is supplied to fill the space 11 so that flow through the space 11 under the projection system PS is laminar. The supply of the immersion liquid from the under supply opening 23 additionally prevents the ingress of bubbles into the space 11. This supply of the immersion liquid may function as a liquid seal.

[0058] The immersion liquid may be recovered from a recovery opening 21 formed in the inner- surface. The recovery of the immersion liquid through the recovery opening 21 may be by application of an underpressure; the recovery through the recovery opening 21 as a consequence of the velocity of the immersion liquid flow through the space 11; or the recovery may be as a consequence of both. The recovery opening 21 may be located on the opposite side of the supply opening 20, when viewed in plan. Additionally or alternatively, the immersion liquid may be recovered through an overflow recovery 24 located on the top surface of the fluid handling structure 12. The supply opening 20 and recovery opening 21 can have their function swapped (i.e. the flow direction of liquid is reversed). This allows the direction of flow to be changed depending upon the relative motion of the fluid handling structure 12 and substrate W.

[0059] Additionally or alternatively, immersion liquid may be recovered from under the fluid handling structure 12 through a recovery opening 25 formed in its bottom surface. The recovery opening 25 may serve to hold a meniscus 33 of the immersion liquid to the fluid handling structure 12. The meniscus 33 forms between the fluid handling structure 12 and the facing surface and it serves as border between the liquid space and the gaseous external environment. The recovery opening 25 may be a porous plate which may recover the immersion liquid in a substantially single phase flow. The recovery opening in the bottom surface may be a series of pinning openings 32 through which the immersion liquid is recovered. The pinning openings 32 may recover the immersion liquid in a two phase flow.

[0060] Optionally radially outward, with respect to the inner-surface of the fluid handling structure 12, is a gas knife opening 26. Gas may be supplied through the gas knife opening 26 at elevated speed to assist liquid confinement of the immersion liquid in the space 11. The supplied gas may be humidified and it may contain substantially carbon dioxide. Radially outward of the gas knife opening 26 is a gas recovery opening 28 for recovering the gas supplied through the gas knife opening 26.

[0061] Further openings, for example open to atmosphere or to a gas source or to a vacuum, may be present in the bottom surface of the fluid handling structure 12, i.e. in the surface of the fluid handling structure 12 facing the substrate W. An example of such an optional further opening 49 is shown in dashed lines on the right hand side of Figure 2a. As shown, the further opening 49 may be a supply or extraction member, which is indicated by the double-headed arrow. For example, if configured as a supply, the further opening 49 may be connected to a liquid supply or a gas supply as with any of thesupply members. Alternatively, if configured as an extraction, the further opening 49 may be used to extract fluid, and may for example, be connected to atmosphere or to a gas source or to a vacuum. For example, the at least one further opening 49 may be present between gas knife opening 26 and gas recovery opening 28, and / or between pinning openings 32 and gas knife opening 26.

[0062] The two different versions of the fluid handling structure 12 of the left and right sides of Figure 2a pin the meniscus 33. The version of the fluid handling structure 12 on the right hand side of Figure 2a may pin the meniscus 33 at a position that is substantially fixed with respect to the final element 100, due to the fixed position of the pinning opening 32. The version of the fluid handling structure 12 on the left hand side of Figure 2a may pin the meniscus 33 below the recovery opening 25, and thus the meniscus 33 may move along the length and / or width of the recovery opening 25. For the radiation beam B to be directed to a full side of the substrate W under exposure, the substrate support WT supporting the substrate W is moved relative to the projection system PS. To maximize the output of substrates W exposed by the lithographic apparatus, the substrate support WT (and so substrate W) is moved as fast as possible. However, there is a critical relative speed (often referred to as a critical scan speed) above which the meniscus 33 between the fluid handling structure 12 and the substrate W becomes unstable. An unstable meniscus 33 has a greater risk of losing immersion liquid, for example in the form of one or more droplets. Furthermore, an unstable meniscus 33 has a greater risk of resulting in the inclusion of gas bubbles in the immersion liquid, especially when the confined immersion liquid crosses the edge of the substrate W.

[0063] A droplet present on the surface of the substrate W may apply a thermal load and may be a source of defectivity. The droplet may evaporate leaving a drying stain, it may move transporting contamination such as a particle, it may collide with a larger body of immersion liquid introducing a bubble of gas into the larger body and it may evaporate, applying the thermal heat load to the surface on which it is located. Such a thermal load could be a cause of distortion and / or a source of a positioning error if the surface is associated with positioning of components of the lithographic apparatus relative to the substrate W being imaged. A formation of a droplet on a surface is therefore is undesirable. To avoid formation of such a droplet, the speed of the substrate support WT is thus limited to the critical scan speed at which the meniscus 33 remains stable. This limits the throughput of the lithographic apparatus.

[0064] The left hand side of the fluid handling system in Figure 2a may comprise a spring 60. The spring 60 may be an adjustable passive spring configured to apply a biasing force to the fluid handling structure 12 in the direction of the substrate W. Thus, the spring 60 can be used to control the height of the fluid handling structure 12 above the substrate W. Such adjustable passive springs are described in US 7,199,874 which is herein incorporated by reference in its entirety. Other bias devices may also be appropriate, for example, using an electromagnetic force. Although the spring 60 is shown with the left hand side of Figure 2a, it is optional and does not need to be included with the other features of the left hand side of Figure 2a. The spring 60 is not shown on any of the otherfigures, but could also be included with the other variations of the fluid handling system described in relation to Figures 2a, 2b, 2c, or 2d.

[0065] Figure 2b shows two different versions of the fluid handling structure 12 on its left side and on its right side, which allow movement of the meniscus 33 with respect to the final element 100. The meniscus 33 may move in the direction of the moving substrate W. This decreases the relative speed between the meniscus 33 and the moving substrate W, which may result in improved stability and a reduced risk of breakdown of the meniscus 33. The speed of the substrate W at which the meniscus33 breaks down is increased so as to allow faster movement of the substrate W under the projection system PS. Throughput is thus increased.

[0066] Features shown in Figure 2b which are common to Figure 2a share the same reference numbers. The fluid handling structure 12 has an inner surface which complements the conical surface of the frusto-conical shape. The bottom surface of the fluid handling structure 12 is closer to the facing surface than the bottom planar surface of the frusto-conical shape.

[0067] Immersion liquid is supplied to the space 11 through supply openings 34 formed in the inner surface of the fluid handling structure 12. The supply openings 34 are located towards the bottom of the inner surface, perhaps below the bottom surface of the frusto-conical shape. The supply openings34 are located around the inner surface, spaced apart around the path of the radiation beam B.

[0068] Immersion liquid is recovered from the space 11 through recovery openings 25, in the bottom surface of the fluid handling structure 12. As the facing surface moves under the fluid handling structure 12, the meniscus 33 may migrate over the surface of the recovery opening 25 in the same direction as the movement of the facing surface. The recovery openings 25 may be formed of a porous member. The immersion liquid may be recovered in single phase. The immersion liquid may be recovered in a two phase flow. The two phase flow is received in a chamber 35 within the fluid handling structure 12 where it is separated into liquid and gas. The liquid and gas are recovered through separate channels 36, 38 from the chamber 35.

[0069] An inner periphery 39 of the bottom surface of fluid handling structure 12 extends into the space 11 away from the inner surface to form a plate 40. The inner periphery 39 forms a small aperture which may be sized to match the shape and size of the radiation beam B. The plate 40 may serve to isolate the immersion liquid at either side of it. The supplied immersion liquid flows inwards towards the aperture, through the inner aperture and then under the plate 40 radially outwardly towards the surrounding the recovery openings 25.

[0070] The fluid handling structure 12 may be in two parts as shown on the right hand side of Figure 2b: an inner part 12a and an outer part 12b. The inner part 12a and the outer part 12b may move relatively to each other, mainly in a plane parallel to facing surface. The inner part 12a may have the supply openings 34 and it may have the overflow recovery 24. The outer part 12b may have the plate 40 and the recovery opening 25. The inner part 12a may have an intermediate recovery 42 for recovering the immersion liquid which flows between the inner part 12a and the outer part 12b.

[0071] The two different versions of the fluid handling structure of Figure 2b thus allow for movement of the meniscus 33 in the same direction as the substrate W, enabling faster scan speeds and increased throughput of the lithographic apparatus. However, the migration speed of meniscus 33 over the surface of the recovery opening 25 in the fluid handling structure 12 of the left side of Figure 2b may be slow. The fluid handling structure 12 of the right side of Figure 2b allows for quicker movement of the meniscus 33, by moving the outer part 12b with respect to the inner part 12a and the final element 100. However, it may be difficult to control the intermediate recovery 42 so as to ensure that enough immersion liquid is provided between the inner part 12a and the outer part 12b to prevent contact therebetween.

[0072] Figure 2c shows two different versions of the fluid handling structure 12 on its left side and on its right side, which may be used to pin the meniscus 33 of the immersion liquid to the fluid handling structure 12 as described above in relation to Figures 2a and / or 2b. Features shown in Figure 2c which are common to Figures 2a and / or 2b share the same reference numbers.

[0073] The fluid handling structure 12 has an inner surface which compliments the conical surface of the frusto-chronical shape. The bottom surface of the fluid handling structure 12 is closer to the facing surface than the bottom planar surface of the frusto-chronical shape. Immersion liquid is supplied to the space 11 delivered through an opening formed in a surface of the fluid handling structure 12. The immersion liquid may be supplied through a supply opening 34 in the inner surface of the fluid structure 12. Alternatively or additionally, the immersion liquid may be supplied through a supply opening 20 in the inner surface of the fluid structure 12. Alternatively or additionally, the immersion liquid is supplied through the under supply opening 23. The immersion liquid may be recovered via an extraction member, for example, via recovery opening 21 formed in the inner- surface and / or overflow recovery 24 and / or one or more openings in a surface of the fluid handling structure 12 as described below.

[0074] The two different versions of the fluid handling structure 12 of the left and right sides of Figure 2c pin the meniscus 33. The version of the fluid handling structure 12 on the right hand side of Figure 2c may pin the meniscus 33 at a position that is substantially fixed with respect to the final element 100, due to the fixed position of the recovery opening 32a. The version of the fluid handling structure 12 on the left hand side of Figure 2c may pin the meniscus 33 below the recovery opening 25, and thus the meniscus 33 may move along the length and / or width of the recovery opening 25.

[0075] As described above in relation to Figure 2b, an inner periphery of the bottom surface of fluid handling structure 12 may extends into the space 11 away from the inner surface to form a plate 40 as shown on the left hand side. As described above, this may form a small aperture, and may isolate the immersion liquid at either side and / or cause immersion liquid to flow inwards towards the aperture, through the inner aperture and then under the plate 40 radially outwardly towards the surrounding the recovery openings 25. Although this features is shown on the left hand side in Figure 2c, it is optional in combination with the other features shown. Preferably, as shown on the left hand side, immersionliquid is supplied to the space 11 through supply openings 34 formed in the inner surface of the fluid handling structure 12. The supply openings 34 are located towards the bottom of the inner surface, perhaps below the bottom surface of the frusto-conical shape. The supply openings 34 are located around the inner surface, spaced apart around the path of the radiation beam B. Alternatively or additionally, the immersion liquid may be supplied through a supply opening 20 in the inner surface of the fluid structure 12. Alternatively or additionally, the immersion liquid is supplied through the under supply opening 23. Although the supply openings 34 are the preferred liquid supply, any combination of supply openings 34, supply openings 20 and / or under supply openings 23 may be provided.

[0076] As shown on the left hand side of Figure 2c, a fluid handling system may comprise the fluid handling structure 12 as described above and a further device 3000. The fluid handling structure 12 may have an extraction member, such as recovery opening 25, and a liquid supply opening, such as the under supply opening 23. It will be understood that the fluid handling structure 12 may comprise any configuration as disclosed in relation to the left hand of Figure 2a, the right hand side of Figure 2a, the left hand side of Figure 2b, the right hand side of Figure 2b or (as described below) the right hand side of Figure 2c, in combination with the further device 3000.

[0077] The further device 3000 may otherwise be referred to as a droplet catcher. The further device 3000 is provided to reduce occurrence of liquid on the surface of the substrate W after the fluid handling structure 12 has moved over the surface. The further device 3000 may comprise a liquid supply member 3010 and at least one extraction member 3020. The at least one extraction member 3020 may be formed in a shape surrounding the at least one supply member 3010 in plan. The at least one liquid supply member 3010 may be configured to provide a further liquid to a space 3110 between at least a part of the further device 3000 and the surface of the substrate W. The further device 3000 may be configured to recover at least some of the liquid via the at least one extraction member 3020. The further device 3000 may be used to incorporate any liquid left on the surface of the substrate W with the liquid in the space 3110 and then use the further device 3000 to extract the liquid such that the amount of liquid remaining on the surface of the substrate W is reduced.

[0078] The further device 3000 is shown as a separate device from the fluid handling structure 12 in Figure 2c. The further device 3000 may be positioned adjacent to the fluid handling structure 12. Alternatively, the further device 3000 may be part of, i.e. integral to, the fluid handling structure 12.

[0079] The further device 3000 may be configured to provide a liquid to the space 3110 which is separate from the liquid provided by the fluid handling structure 12.

[0080] Additionally or alternatively, the fluid handling structure 12 may have the components as shown on the right hand side of Figure 2c. More specifically, the fluid handling structure 12 may comprise the at least one liquid supply member, two extraction members (e.g., recovery openings 32a and 32b) and two gas supply members (e.g., gas supply openings 27a and 27b) formed on the surface of the fluid handling structure 12. Gas supply opening 27a can be omitted, i.e. is optional. The atleast one liquid supply member may be the same as the under supply opening 23 in the bottom surface of the fluid handling structure 12 described above or the supply opening 20 or liquid supply openings 34 formed on the inner surface of the fluid handling structure 12 described in relation to left hand side of Figure 2b. The liquid supply member, the extraction members and the gas supply members may be formed on the surface of the fluid handling structure 12. Specifically, these components may be formed on a surface of the fluid handling structure 12 facing the substrate W, i.e. the bottom surface of the fluid handling structure 12.

[0081] At least one of the two extraction members may comprise a porous material 37 therein. The porous material 37 may be provided within an opening, e.g., recovery opening 32a through which fluid handling structure 12 extracts fluid from below the fluid handling structure 12 and may recover the immersion liquid in a single phase flow. The other of the two extraction members, e.g., recovery opening 32b may recover the immersion fluid as a dual phase extractor. The porous material 37 does not need to be flush with the bottom surface of the fluid handling structure 12.

[0082] Specifically, the fluid handling structure 12 may comprise the liquid supply member (e.g., under supply opening 23), with a first extraction member (e.g., recovery opening 32a) radially outwards of the liquid supply member, and a first gas supply member (e.g., gas supply opening 27a) radially outwards of the first extraction member, and the second extraction member (e.g., recovery opening 32b) radially outwards of the first gas supply member, and a second gas supply member (e.g., gas supply opening 27b) radially outwards of the second extraction member. Similar to Figure 2a, further openings, for example open to atmosphere or to a gas source or to a vacuum, may be present in the bottom surface of the fluid handling structure 12 as described previously (in relation to the fluid handling structure 12).

[0083] For example, at least one further opening (not shown) may be provided in the bottom surface of the fluid handling structure 12. The further opening is optional. The further opening may be arranged between the first extraction member (e.g., recovery opening 32a) and the first gas supply member (e.g., gas supply opening 27a) as described in the arrangement above. Alternatively or additionally, the further opening may be arranged between the second extraction member (e.g., recovery opening 32b) and the second gas supply member (e.g., gas supply opening 27b) as described in the arrangement above. The further opening may be the same as further opening 49 described above.

[0084] Optionally, the fluid handling structure 12 comprises a recess 29. The recess 29 may be provided between the recovery opening 32a and recovery opening 32b or gas supply opening 27a and recovery opening 32b. The shape of the recess 29 may be uniform around the fluid handling structure 12 and may optionally contain an inclined surface. In the case of the recess 29 provided between the recovery opening 32a and recovery opening 32b, the gas supply opening 27b may be provided on the inclined surface as shown in Figure 2c. In the case of the recess 29 provided between the supply opening 27a and recovery opening 32b, the gas supply opening 27b may be provided on the inclinedsurface or a part of the bottom surface of the fluid handling structure 12 which is parallel to the surface of the substrate W. Alternatively, the shape of the recess 29 may vary around the circumference of the fluid handling structure 12. The shape of the recess 29 may be varied to alter the impact of gas supplied from the gas supply members on the fluid below the fluid handling structure 12.

[0085] Figure 2d shows, in its left and right halves, two different versions of the fluid handling structure 12. The fluid handling structure 12 of the left half of Figure 2d has a liquid injection buffer 41a, which holds a buffer amount of immersion liquid, and liquid injection holes 41 which supply immersion liquid from the liquid injection buffer to the space 11. Outwardly of the liquid injection holes 41 are inner liquid recovery apertures 43 for conducting liquid to an inner recovery buffer 43 a which is provided with a porous member. A recess 29 similar to that described relating to Figure 2c is provided outward of the inner liquid recovery apertures 43. Outward of the recess 29, in the lower face of the fluid handling structure 12 is a gas guiding groove 44 into which open outer recovery holes 44a. The outer recovery holes 44a lead a two-phase recovery flow to outer recovery buffer 44b which is also provided with a porous member. Outermost are gas sealing holes 45 which communicate between a gas sealing buffer volume 45a and the space underneath the fluid handling structure 12 to provide a gas flow to contain the immersion liquid.

[0086] The fluid handling structure 12 of the right half of Figure 2d has a liquid supply opening 20 in the inner inclined face thereof. In the underside of the fluid handling structure 12 there are (from inner side to outer side) an extraction opening 25 provided with a porous member 37; a first gas knife opening 26a, a second gas knife opening 26b and a third gas knife opening 26c. Each of these openings opens into a groove in the underside of the fluid handling structure 12 that provides a buffer volume. The outermost part of the fluid handling structure 12 is stepped so as to provide a greater separation between the fluid handling structure 12 and the substrate W.

[0087] Figures 2a-2d show examples of different configurations which can be used as part of a fluid handling system. It will be understood that the examples provided above refer to specific extraction members and recovery members, but it is not necessary to use the exact type of extraction member and / or recovery member. In some cases different terminology is used to indicate the position of the member, but the same functional features may be provided. Examples of the extraction member referred to above include recovery opening 21, overflow recover 24, recovery opening 25 (possibly comprising a porous plate and / or the chamber 35), gas recovery opening 28, pinning opening 32, recovery opening 32a, recovery opening 32b and / or the intermediate recovery 42. Examples of the supply member referred to above include supply opening 20, under supply opening 23, gas knife opening 26, gas supply opening 27a, gas supply opening 27b, and / or supply openings 34. In general, an extraction member used to extract / recover fluid, liquid or gas is interchangeable with at least any of the other examples used which extract / recover fluid, liquid or gas respectively. Similarly, a supply member used to supply fluid, liquid or gas is interchangeable with at least any of the other examplesused which supply fluid, liquid or gas respectively. The extraction member may extract / recover fluid, liquid or gas from a space by being connected to an underpressure which draws the fluid, liquid or gas into the extraction member. The supply member may supply fluid, liquid or gas to the space by being connected to a relevant supply.

[0088] Figure 3 schematically illustrates, with a side on view, the relative positions of a fluid handling structure 12 and substrate W and / or substrate support WT. The fluid handling structure 12, substrate W and substrate support WT may be according to known implementations during a lithographic process. In particular, the fluid handling structure 12 may be the same as, or similar to, any of the fluid handling structures 12 described with reference to Figures 2a to 2d.

[0089] There is a separation distance between fluid handling structure 12 and substrate W and / or substrate support WT. The separation distance may be referred to as the fly height of the fluid handling structure 12. During a lithographic process, the substrate support WT, together with a substrate W that is loaded on the substrate support WT, is moved relative to the fluid handling structure 12 by a positioning device, such as the second positioner PW described in relation to Figure 1. The positioning device may be controlled by a control system, such as the controller 500 described in relation to Figure 1. The movement of the substrate W and substrate support WT may be in the x-y plane and may comprise substantially no movement in the z-direction. The fluid handling structure 12 may be separated from the substrate W and / or substrate support WT in the z-direction. That is to say, the fluid handling structure 12 is separated from the substrate W and substrate support WT in a direction that is orthogonal to the plane in which the substrate W and substrate support WT move. When a substrate W is exposed to a patterned radiation beam B, the path of the patterned radiation beam B through the space 11 may be substantially in the z-direction.

[0090] Figure 3 schematically illustrates a cross-sectional view of the left side of a fluid handling structure 12. The fluid handling structure 12 may have the features of the fluid handling structure 12 as shown in any of Figures 2a- 2d. As shown in Figure 3, in an embodiment the fluid handling structure 12 comprises a plurality of channels configured to supply fluid towards the substrate W and / or the space 11 and / or extract fluid away from the substrate W and / or the space 11. In an embodiment the plurality of channels comprises under supply openings 23 as described elsewhere. In an embodiment the plurality of channels comprises pinning openings 32 as described elsewhere. In an embodiment the plurality of channels comprises channels associated with the gas knife openings 26 as described elsewhere. The channels 13 may be associated with the gas knife openings 26 by being in fluid communication with the gas knife openings 26. The channels 13 may open out into the gap between the fluid handling structure 12 and the substrate W at the gas knife openings 26. In an embodiment the plurality of channels comprises channels associated with the gas recovery openings 28 as described elsewhere.

[0091] Embodiments of the invention are described primarily in the context of the plurality of channels being channels 13 associated with the gas knife openings 26. However, the invention maybe implemented with the plurality of channels comprising additional channels associated with other openings or alternative channels associated with different openings, e.g., under supply openings 23, pinning openings 32 and gas recovery openings 28.

[0092] As shown in Figure 3, in an embodiment the fluid handling structure 12 comprises a flow adjuster 50. The flow adjuster 50 is configured to move relative to the channels 13. For example, the flow adjuster 50 may be configured to move across the channels 13. In the arrangement shown in Figure 3, the flow adjuster 50 may be configured to move in at least the left-to-right directions. The flow adjuster 50 may be configured to move in a direction that is substantially perpendicular to the longitudinal direction of the channels 13. However, this is not necessarily the case. For example, the channels 13 may extend in a longitudinal direction other than the Z direction. The channels 13 may extend diagonally such that their longitudinal direction has a component in the X-Y plane. In an embodiment the flow adjuster 50 is configured to move within the X-Y plane. Additionally or alternatively, the flow adjuster 50 may be configured to move within a plane that is angled relative to the X-Y plane. The flow adjuster 50 may be configured to move in a plane such that the flow adjuster 50 may move in directions having a component in the Z direction.

[0093] The flow adjuster 50 is configured to partially block the channels 13. The extent to which the flow adjuster blocks the channels 13 may be adjusted by moving the flow adjuster 50. In an embodiment, the flow adjuster 50 may be moved to a location in which at least some, and optionally all, of the channels 13 are unblocked by the flow adjuster 50. In an embodiment the flow adjuster 50 is configured to move to a position in which the flow adjuster 50 completely blocks at least some of, and optionally all of, the channels 13. The flow adjuster 50 may be controlled so as to be at a target position relative to the channels 13. In an embodiment the target position is selected dependent on a desired flow. One or more target positions correspond to a position at which the flow adjuster 50 partially blocks at least one of the channels 13. In an embodiment the flow adjuster 50 is configured to move within the channels 13 relative to the centre point of openings (e.g. gas knife openings 26) with which the channels 13 are associated.

[0094] In an embodiment the fluid handling structure 12 comprises an actuation device 18 (shown in Figure 22). The actuation device 18 is configured to move the flow adjuster 50 relative to the channels 13. In an embodiment the actuation device 18 is configured to control the extent to which the channels 13 are blocked by the flow adjuster 50. In an embodiment the actuation device 18 is configured to control the extent to which flow through the openings 26 is restricted by the flow adjuster 50. In an embodiment the flow adjuster 50 is arranged such that the flow adjuster 50 blocks different channels 13 to different extents.

[0095] In an embodiment the fluid handling structure 12 comprises a control system (not shown). The control system is configured to control the actuation device 18 so as to control partial blocking of the channels 13 by the flow adjuster 50. The control system may be the controller 500 shown in Figure 1. Alternatively, the control system may be independent of the controller 500. The controlsystem may be considered to form part of the fluid handling system comprising the fluid handling structure 12. The control system may be physically separated from the rest of the fluid handling structure 12. The control system may be considered to be part of the lithographic apparatus. The control system is configured to control the extent to which different channels 13 of the plurality of channels 13 are blocked by the flow adjuster 50.

[0096] An embodiment of the invention is expected to improve the accuracy with which flow of fluid caused by, i.e., supplied from and / or extracted into, the fluid handling structure 12 may be controlled. An embodiment of the invention is expected to increase the flexibility of control of the fluid handling structure 12. An embodiment of the invention is expected to increase the number of different ways in which the fluid handling structure 12 may be implemented so as to improve performance.

[0097] For example, an embodiment of the invention is expected to increase throughput of substrates W without unduly increasing defectivity issues. Defects can be caused by shedding of immersion liquid. Immersion liquid may be lost in the middle of the substrate W and also as droplets shed near the edge of the substrate W. In general, it is expected that the problem of droplets being shed near the edge of the substrate W is worse when the relative movement between the substrate W and the fluid handling structure 12 is increased. An embodiment of the invention is expected to allow higher scan speeds, without significantly increasing defects due to liquid being shed near the edge of the substrate W.

[0098] By controlling relative movement between the flow adjuster 50 and the channels 13, the flow through the channels 13 and therefore through the gas knife openings 26 (or other openings with which the channels may be associated) can be changed and / or manipulated. When the flow adjuster 50 is moved, the effective flow area of the channels 13 is adjusted. The size of the channels 13 remains constant. However, by moving the flow adjuster 50 across the channels 13, the flow adjuster 50 can partially or fully block the channels 13 for flow.

[0099] By controlling the flow adjuster 50, the gas knife at the receding edge of the fluid handling structure 12 may be made stronger while the edge of the substrate W is passing the fluid handling structure 12. The strength of the gas knife may be controlled by controlling the effective flow area of the channels 13 associated with the gas knife openings 26. In general, a greater effective flow area is associated with a stronger gas knife. By making the gas knife stronger, the film of immersion liquid behind the gas knife is expected to reduce. After the gap between the edge of the substrate W and the substrate support WT is passed, the gas knife could be made weaker again. By strengthening the gas knife while the edge of the substrate W is passing the fluid handling structure 12, shedding of liquid and therefore defects caused by shedding of liquid may be reduced.

[0100] An embodiment of the invention is expected to simplify construction of a fluid handling structure 12 while allowing control of flow caused by the fluid handing structure 12. The flow adjuster 50 allows the flow to be controlled without requiring extra equipment such as flowcontrollers, hoses, connections and valves. This simplifies not only the structure of the fluid handling structure 12 but also the structure of parts of the lithographic apparatus external to the fluid handling structure 12. This also reduces the amount of collaboration required between different components (e.g. between different flow controllers).

[0101] An embodiment of the invention is expected to reduce lag time in controlling flows caused by the fluid handling structure 12. As shown in Figure 3, in an embodiment the flow adjuster 50 may be provided near the gas knife openings 26 associated with the channels 13. This helps to keep flow response times low. In contrast, if flow controllers were used then the response times would be expected to be greater due to the flow path between such flow controllers and the gas knife openings 26.

[0102] An embodiment of the invention is expected to provide a more robust and / or reliable way of controlling flow caused by a fluid handling structure 12. Movements of the flow adjuster 50 are expected to induce lower levers of vibrations compared to using flow controllers. This is expected to make the fluid handling structure 12 more robust and less likely to experience damage due to vibrations. Additionally, by reducing the vibrations, any compensation required in movement of the fluid handling structure 12 may be reduced, thereby improving accuracy.

[0103] Figures 4 and 5 schematically illustrate a function of the flow adjuster 50. As shown in Figure 4, in an embodiment the flow adjuster 50 comprises a plate. In an embodiment the flow adjuster comprises holes or apertures 51. Figure 4 also shows part of the channels 13. The channels 13 may be at least partly defined by a housing member 16. The housing member 16 may comprise a plate. As shown in Figure 4, in an embodiment the flow adjuster 50 is located adjacent to the channel 13. The flow adjust 50 may be positioned such that the open flow area of the channel 13 is controlled. The flow adjuster 50 is configured such that an open flow area 52 defined by the flow adjuster 50 and the housing member 16 may vary between the aperture 51 and the channel 13 along the flow adjuster 50. For example, as shown in Figure 4 the flow adjuster 50 is positioned such that the open flow area 52 of the channel 13 is reduced compared to the cross-sectional area of the channel 13. By controlling the position of the flow adjuster 50, the open flow area 52 of the channel 13 may be controlled so as to regulate a flow rate through the channel 13.

[0104] Figure 5 shows the flow adjuster 50 in a different position relative to the channels 13. By altering the open flow area 52, the flow restriction is changed and thereby a different flow rate can be regulated. In an embodiment, the flow adjuster 50 is configured to move in the left-right directions shown in Figure 4. The channels 13 may have a fixed position relative to the rest of the fluid handling structure 12. Alternatively, in an embodiment the housing member 16 may be configured to move so as to move the channels 13. By controlling movement of the flow adjuster 50 and / or the housing member 16, the open flow area 52 of the channels 13 may be controlled so as to regulate the flow rate. A variable flow area is obtained when the flow adjuster 50 is positioned differently to the channels 13.In an embodiment the flow adjuster 50 and the housing member 16 are separated by a gas bearing. This may help to reduce undesirable particle generation.

[0105] Figure 6 schematically illustrates a top view of a flow adjuster 50. As shown in Figure 6, in an embodiment the flow adjuster 50 comprises a plurality of apertures 51. The apertures 51 may be arranged in one or more arrays. As shown in Figure 6, in an embodiment the apertures 51 are arranged to form a shape. In an embodiment the shape surrounds a central portion of the flow adjuster 50. In an embodiment the shape is similar to, or the same as, the shape in which the channels 13 are arranged.

[0106] Figure 7 schematically shows the flow adjuster 50 of Figure 6 applied to channels 13 of a fluid handling structure 12. As shown in Figure 7, the flow adjuster 50 may be positioned such that the channels 13 are partially blocked by the flow adjuster 50. There may be a region of overlap between the apertures 51 of the flow adjuster 50 and the channels 13. The overlapping area corresponds to the open flow area 52 of the channels 13. By controlling the position of the flow adjuster 50, the extent to which the channels 13 are blocked by the flow adjuster 50 may be controlled. The open flow area 52, and hence flow rate, may be controlled.

[0107] An embodiment of the invention is expected to make it easier to provide low flow rates. By shifting the flow adjuster 50, open flow areas 52 of arbitrarily small size may be obtained. Without use of the flow adjuster 50, it would be more difficult to manufacture particularly small channel sizes in order to obtain low flow rates. The flow adjuster 50 allows open flow areas 52 to be generated beyond the manufacturing tolerances of the fluid handling structure 12.

[0108] Figures 8-11 schematically depict alternative arrangements of apertures 51 and channels 13. Figures 8-11 show the flow adjuster 50 as a plate adjacent to the housing member 16 defining the channels 13. By positioning the flow adjuster 50, the open flow area 52 may be controlled (e.g. reduced relative to the cross-sectional area of the channels 13). By altering the open flow area 52, the flow restriction is changed and thereby a different flow rate can be regulated. As shown in Figures 8- 11, different geometries of the apertures 51 are possible.

[0109] For example, as shown in Figure 8 in an embodiment the apertures 51 of the flow adjuster 50 are elliptical, for example circular. In an embodiment the channels 13 have an elliptical, e.g. circular, cross-sectional area. This results in open flow areas 52 having edges defined by convex arcs.

[0110] Figure 9 shows an alternative flow adjuster 50 in which the apertures 51 have a smaller size. In an embodiment, the apertures 51 are smaller than the cross-sectional areas of the channels 13. This allows the open flow area 52 to be defined by the flow adjuster 50.

[0111] As shown in Figure 10, in an alternative embodiment the apertures 51 of the flow adjuster 50 are polygonal. For example, as shown in Figure 10 in an embodiment the apertures 51 are quadrilaterals, for example parallelograms such as squares. In an embodiment the channels 13 have a cross-sectional area that is polygonal. As shown in Figure 10, in an embodiment the open flow area 52 is polygonal.

[0112] Figure 11 shows an alternative arrangement in which the apertures 51 are polygonal and the channels 13 have an elliptical cross-section. This results in a differently shaped open flow area 52 defined by a straight edge and an arc. The shape and size of the apertures 51 and the shape and size of the cross-sectional areas of the channels 13 may be selected depending on the desired characteristics of the flow.

[0113] In an embodiment the flow adjuster 50 comprises substantially the same number of apertures 51 as the number of channels 13 to have their open flow area 52 controlled by the flow adjuster 50. Alternatively, the flow adjuster 50 may comprise a lower number of apertures 51 or a greater number of apertures 51.

[0114] In an embodiment the flow adjuster 50 is configured such that when a first set of the channels 13 are minimally blocked by the flow adjuster 50, a second set of the channels 13 are more than minimally blocked by the flow adjuster 50. In other words, the relationship between the extent to which a channel 13 is blocked and the position of the flow adjuster 50 is different for different sets of channels 13. This is shown schematically in Figure 12. Figure 12 shows a flow adjuster 50 applied to channels 13 of a fluid handling structure 12. Minimally blocked means that the flow adjuster 50 is positioned within its range of possible locations such that the flow adjuster 50 blocks the first set of channels 13 no more than when the flow adjuster 50 is at any other position within its range of possible positions. This means that the open flow area 52 defined by the flow adjuster 50 at these locations is at its maximum value. In an embodiment the flow adjuster 50 is of a fixed geometry and dimension.

[0115] As shown in Figure 12, in an embodiment the flow adjuster 50 comprises apertures 51 forming a shape that generally is similar to the shape formed by the channels 13 of the fluid handling structure 12. However, as shown in Figure 12 in an embodiment the (exact) pattern formed by the apertures 51 is different from the pattern formed by the channels 13. In the arrangement shown in Figure 12, the distribution of the apertures 51 is contracted slightly (compared to the distribution of channels 13) in the Y-direction (i.e. the up-down direction in Figure 12). As a result, different channels 13 are blocked to different extents by the flow adjuster 50.

[0116] The arrow shown in Figure 12 represents the direction in which the substrate W moves under the fluid handling structure 12. The direction is the direction of movement of the substrate W relative to the fluid handling structure 12. The open flow area 52 for the set of channels 13 shown in the top half of Figure 12, i.e., receding edge of the fluid handling structure 12 is greater than the open flow area 52 of the set of channels 13 in the bottom half of Figure 12, i.e., advancing edge of the fluid handling structure 12. When the channels 13 are associated with the gas knife openings 26, the gas knife is stronger through the set of channels 13 which have a greater open flow area 52. By controlling the flow adjuster 50, there may be different flow rates at the advancing and receding edges of the fluid handling structure 12. There may be different flow rates for different channels 13 at different positions in the direction of the scan direction.

[0117] In an embodiment the flow adjuster 50 may be shifted downwards compared to the arrangement shown in Figure 12. By shifting the flow adjuster 50, there may be a greater open flow area 52 for the channels 13 in the bottom half of Figure 12 and a smaller open flow area 52 for the channels 13 in the top half of Figure 12 (i.e. the opposite of what is shown in Figure 12).

[0118] Figure 13 shows an arrangement in which the flow adjuster 50 is shifted downwards relative to its position shown in Figure 12. As shown by the arrow in Figure 13, the scan direction is reversed compared to Figure 12. In an embodiment, the control system is configured to control the position of the flow adjuster 50 based on the scan direction. This allows the flow rate to be controlled depending on whether the channels 13 face towards the scan direction or away from the scan direction.Although Figures 12 and 13 show a greater open flow area 52 for channels 13 that are at the receding edge of the fluid handling structure 12, the opposite may be implemented. In an embodiment the control system is configured to control positioning of the flow adjuster 50 such that the open flow area 52 of channels 13 is greater at the advancing edge of the fluid handling structure 12.

[0119] In an embodiment the first set of channels 13 and the second set of channels 13 (i.e. the sets of channels 13 that have different open flow areas 52) are on opposite sides of the space 11. This is shown in Figures 12 and 13, where the space 11 is surrounded by the apertures 51 and the channels 13. In an embodiment the flow adjuster 50 can be controllably positioned so as to partly block a group of channels 13, for example to have greater flow as one side of the space 11 (e.g. the receding edge) and lower flow at the other side of the space 11 (e.g. the advancing edge).

[0120] In an embodiment the control system is configured to control the actuation device 18 dependent on a direction of relative movement between the fluid handling structure 12 and the substrate W. This may allow the gas knife to be made stronger at the receding edge of the fluid handling structure 12. This may help to reduce the amount of liquid shed which may cause defects.

[0121] As shown in Figures 6, 7, 12 and 13, in an embodiment the flow adjuster 50 comprises a plurality of apertures 51. The apertures 51 are arranged to partially overlap with respective at least one of the channels 13. For example, as shown in Figures 12 and 13, in an embodiment the apertures 51 are arranged to partially overlap with respective channels 13. There may be an aperture 51 for each of the channels 13. However, it is not essential for there to be an aperture 51 for each channel 13. In an alternative embodiment, one or more of the apertures 51 may correspond to a plurality of the channels 13. For example, in an embodiment the apertures 51 are arranged to partially overlap with respective pairs of the channels 13. Each pair of channels 13 may comprise two channels 13 at non-overlapping distances from the space 11. Figure 14 schematically shows a side view of a flow adjuster 50 in which an aperture 51 corresponds to a pair of channels 13, 17. In an embodiment, one of the channels 13 is associated with a gas knife opening 26, e.g., referring to Figure 22. The other channel 17 may be associated with the gas supply openings 27, e.g., referring to Figure 22. The gas supply openings 27 may be radially outward of the gas knife openings 26. The channels 13 may beradially inward of the other channels 17. The gas supply openings 27 may be for maintaining the environment of a gas (e.g. carbon dioxide).

[0122] As shown in Figure 14, in an embodiment the aperture 51 may overlap with none, one or both of the channels 13, 17, depending on the position of the flow adjuster 50. In the position shown in Figure 14, the aperture 51 partially overlaps with both the channel 13 and the other channel 17. The overlap between the aperture 51 and the channel 13 results in an open flow area 52 of the channel 13. The overlap between the aperture 51 and the other channel 17 corresponds to the other open flow area 53 of the other channel 17.

[0123] Figure 15 schematically illustrates a top view of a flow adjuster 50. As shown in Figure 15, in an embodiment the flow adjuster 50 comprises a plurality of apertures 51 that may each overlap with a plurality of channels 13, 17. As shown in Figure 15, in an embodiment the apertures 51 are elongate. In an embodiment the direction of elongation is substantially radial. The direction of elongation may correspond to the direction joining the centre points of the channels 13, 17 within each pair of channels 13, 17. It is not essential for the apertures 51 to be elongate. In an alternative embodiment, the apertures 51 may be bulbous and arranged to at least partially overlap with a plurality of channels 13, 17.

[0124] Figure 16 schematically illustrates the flow adjuster 50 of Figure 15 applied to a fluid handling structure 12 comprising channels 13 and other channels 17. As shown in Figure 16, each aperture 51 is arranged to partially overlap with both the channels 13 associated with the gas knife openings 26 and the other channels 17 associated with the gas supply openings 27, e.g., referring to Figure 22. The extent of overlap and hence the open flow areas 52, 53 may be controlled by controlling the position of the flow adjuster 50.

[0125] Figures 17-19 schematically illustrate a function of the flow adjuster 50 in which each aperture 51 corresponds to a plurality of channels 13, 17. In Figure 17, the open flow area 52 of the channels 13 is smaller than the other open flow area 53 of the other channels 17. Figure 18 shows the situation where the flow adjuster 50 is moved to the right slightly compared to its position in Figure17. In the position shown in Figure 18, the open flow area 52 of the channels 13 is substantially equal to the other open flow area 53 of the other channels 17. Figure 19 shows the situation where the flow adjuster 50 is moved slightly further to the right compared to its position shown in Figure 17 or Figure18. In the position shown in Figure 19, the open flow area 52 of the channels 13 is greater than the other open plan area 53 of the other channels 17.

[0126] Figures 20 and 21 schematically illustrate how the open flow areas 52, 53 may be adjusted when the flow adjuster 50 is applied to a fluid handling structure 12 comprising both the channels 13 associated with the gas knife openings 26 and the other channels 17 associated with the gas supply openings 27. In the position shown in Figure 20, the open flow area 52 of the channels 13 associated with the gas knife openings 26 is greater in the bottom half of Figure 20 than in the top half of Figure20, and the other open flow area 53 of the other channels 17 associated with the gas supply openings 27 is greater in the top half of Figure 20 than in the bottom half of Figure 20.

[0127] Figure 21 shows the arrangement of Figure 20 in which the flow adjuster 50 is shifted down slightly compared to its position in Figure 20. As shown in Figure 21, the open flow areas 52 associated with the gas flow openings 26 may be greater in the top half of Figure 21 than in the bottom half of Figure 21. The other open flow areas 53 of the other channels 17 associated with the gas supply openings 27 may be greater in the bottom half of Figure 21 than in the top half of Figure21. As shown in Figures 20 and 21, the position of the flow adjuster 50 may be controlled dependent on the direction in which the substrate W is being scanned relative to the fluid handling structure 12. Additionally or alternatively, the position of the flow adjuster 50 may be controlled dependent on the position where the substrate W is located relative to the fluid handling structure 12. In the arrangements shown in Figures 20 and 21, the scan direction is shown by the arrows. In Figures 20 and 21, the other open flow areas 53 associated with the gas supply openings 27 are greater at the receding edge of the fluid handling structure 12. In an alternative embodiment, the control system is configured to control movement of the flow adjuster 50 such that the open flow areas 52 associated with the gas knife openings 26 is greater at the receding edge of the fluid handling structure 12 (i.e. opposite to what is shown in Figures 20 and 21).

[0128] Figure 22 schematically illustrates a cross-sectional view of the left side of the fluid handling structure 12 comprising both the gas knife openings 26 and the gas supply openings 27. As shown in Figure 22, in an embodiment the flow adjuster 50 is arranged to partially overlap both the channels 13 associated with the gas knife openings 26 and the other channels 17 associated with the gas supply openings 27. In the arrangement shown in Figure 22, the other channels 17 associated with the gas supply openings 27 correspond to apertures 15 of a restriction plate 14.

[0129] As shown in Figure 22, in an embodiment the fluid handling structure 12 comprises a restriction plate 14. The restriction plate 14 is configured to define an area of at least some of the channels 13, 17 configured to supply gas towards the substrate W. For example in the arrangement shown in Figure 22, the restriction plate 14 is configured to define an area of the other channels 17 configured to supply gas towards the substrate W. The other channels 17 are associated with the gas supply openings 27. The restriction plate 14 is arranged to define the area of the other channels 17 by comprising apertures 15. The restriction plate 14 is configured to control the division of gas between the channels 13 associated with the gas knife openings 26 and the other channels 17 associated with the gas supply openings 27. In an embodiment the restriction plate 14 is fixed in position relative to the main body of the fluid handling structure 12. The restriction plate 14 may be initially made as a separate component from the main body of the fluid handling structure 12. The restriction plate 14 may subsequently be fixed in position relative to the main body of the fluid handling structure 12. Alternatively, the restriction plate 14 may be formed integrally with the main body of the fluid handling structure 12.

[0130] As shown in Figure 22, in an embodiment the flow adjuster 50 is adjacent to the restriction plate 14. For example, as shown in Figure 22, in an embodiment the flow adjuster 50 is just above the restriction plate 14. The restriction plate 14 is located between the flow adjuster 50 and the gas supply openings 27 in the Z-direction. However, it is not essential for the flow adjuster 50 to be above the restriction plate 14. In an alternative embodiment, the flow adjuster 50 is positioned below the restriction plate 14. The flow adjuster 50 may be located between the restriction plate 14 and the gas supply openings 27 in the Z-direction. The flow adjuster 50 may be configured to partially block the apertures 15 of the restriction plate 14 so as to control the flow rate through the other channels 17 and the gas supply openings 27. It is not essential for the flow adjuster 50 to be immediately adjacent to the restriction plate 14. In an alternative embodiment, the flow adjuster 50 may be located at an intermediate point between the restriction plate 14 and the gas supply openings 27 and may be distanced from the restriction plate 14 in the Z-direction.

[0131] In an embodiment the flow adjuster 50 is upstream of the restriction plate 14. This is shown in Figure 22, where the downstream direction is downwards through the channels 13, 17 and out through the gas knife openings 26 and the gas supply openings 27. However, it is not essential for the flow adjuster 50 to be upstream of the restriction plate 14. In an alternative embodiment, the flow adjuster 50 is downstream of the restriction plate 14.

[0132] An exemplary actuation device 18 is shown in Figure 22. In an embodiment the actuation device 18 comprises a mechanical actuator configured to move the flow adjuster 50. In an embodiment the actuation device 18 comprises a piezoelectric actuator configured to move the flow adjuster 50. In an embodiment the actuation device 18 comprises a drive chain actuator configured to move the flow adjuster 50.

[0133] As mentioned above, in an embodiment the flow adjuster 50 comprises apertures 51 arranged to overlap with the channels 13. However, it is not essential for the flow adjuster 50 to comprise apertures 51. In an alternative embodiment, the flow adjuster 50 comprises a contiguous component configured to partially (or fully) block the channels 13. Figure 23 schematically illustrates an embodiment in which the flow adjuster 50 does not comprise any apertures 51. The flow adjuster 50 comprises an external edge 54. The external edge 54 is configured to define the edge of the open flow area 52 of the channels 13. In an embodiment the control system is configured to control movement of the flow adjuster 50 so as to control the extent to which different channels 13 are blocked by the flow adjuster 50.

[0134] Figures 24-27 show the function of the flow adjuster 50 depending on its position. The position may be controlled by the control system. In the position shown in Figure 24, the flow adjuster 50 is moved slightly in the plus Y-direction. The channels 13 in the highlighted region 55 have a small open flow area 52. When the channels 13 are associated with the gas knife openings 26, a low open flow area 52 may be used to provide low gas knife flow.

[0135] In the alternative position shown in Figure 25, the open flow areas 52 of the channels 13 in the highlighted region 55 are greater. This is because the flow adjuster 50 is shifted in the minus Y- direction compared to Figure 24. A stronger gas knife may be desirable for example at the receding edge of the fluid handling structure 12 so as to reduce liquid loss through film pulling.

[0136] As shown in the Figures, in an embodiment the flow adjuster 50 is configured to move translationally relative to the channels 13. In the description above, movement of the flow adjuster 50 in the Y-direction has been focussed on. However, in an embodiment the flow adjuster 50 is configured to move within a plane. The flow adjuster 50 may be moved in the X-direction and the Y- direction.

[0137] For example, Figure 26 shows the flow adjuster 50 in which the flow adjuster 50 is moved in the plus X-direction. As a result, the open flow area 52 for channels 13 at the plus X-side of the fluid handling structure 12 is smaller. The open flow area 52 for channels 13 at the minus X-side of the fluid handling structure 12 is greater. Figure 27 shows the arrangement of Figure 26 in which the flow adjuster 50 is moved in the minus X-direction. The control system is configured to control movement of the flow adjuster 50 in at least two degrees of freedom so as to control flow rate through the channels 13.

[0138] In an embodiment the flow adjuster 50 is configured to move rotationally relative to the channels 13. By allowing rotational movement of the flow adjuster 50, further flexibility of the system may be provided.

[0139] Figure 28 schematically illustrates an alternative arrangement of a flow adjuster 50. As shown in Figure 28, the flow adjuster 50 comprises an external edge 54. The flow adjuster 50 may further comprise an internal edge 56. The internal edge 56 may define the edge of the open flow area 52 of some of the channels 13. The flow adjuster 50 may be configured to controllably partially block the channels 13 associated with gas knife openings 26 as well as the other channels 17 associated with the gas supply openings 27.

[0140] Figure 29 schematically depicts a possible implementation of the flow adjuster 50 of Figure 28 in a side view. As shown in Figure 29, depending on the position of the flow adjuster 50, the flow adjuster 50 may partially or fully overlap the channels 13 and the other channels 17.

[0141] Figure 30 schematically illustrates the arrangement shown in Figures 28 and 29, with the flow adjuster 50 moved in the minus Y-direction. In an embodiment the control system is configured to control the position of the flow adjuster 50 dependent on the scan direction. In an embodiment, at the advancing edge a low gas knife flow may be provided. The advancing edge may be the upper side of Figure 30. As shown in Figure 30, in an embodiment a high gas supply flow may be provided at the advancing edge. This can help to reduce gas reaching and penetrating through the meniscus 33. As shown in Figure 30, this is done by shifting the flow adjuster 50.

[0142] In an embodiment, at the receding edge a high gas knife flow may be provided to reduce liquid loss through film pulling. In an embodiment a low gas supply is provided because there may be already a sufficient gas supplied through the gas knife openings 26.

[0143] Figures 31-33 schematically depict different possible shape configurations for the flow adjuster 50. The shape of the flow adjuster 50 may be selected depending on the desired flow rates, desired pressures and other parameters of the lithographic process. As shown in Figure 31, in an embodiment the flow adjuster 50 comprises convex portions 57. The convex portions 57 may be provided at the external edge and / or at the internal edge of the flow adjuster 50. The convex portions 57 may be provided in locations that correspond to the channels 13.

[0144] As shown in Figure 32, in an embodiment the flow adjuster 50 comprises concave portions58. The concave portions 58 may be provided at the external edge and / or at the internal edge of the flow adjuster 50. In an embodiment the concave portions 58 are provided at locations corresponding to locations of the channels 13.

[0145] As shown in Figure 33, in an embodiment the flow adjuster 50 comprises needle portions59. The needle portions 59 have the shape of a needle. The needle portions 59 are elongate. As shown in Figure 33, in an embodiment the needle portions 59 are provided to protrude from the external edge and / or from the internal edge of the flow adjuster 50. In an embodiment the needle portions 59 are provided at locations corresponding to locations of the channels 13.

[0146] Figure 34 schematically depicts an arrangement of a flow adjuster 50. In an embodiment the flow adjuster 50 comprises a plurality of separate members 50a, 50b, 50c, 50d. The separate members 50a-d are arranged to partially overlap with the channels 13. In an embodiment, each separate member 50a-d is arranged to partially overlap a different set of the channels 13.

[0147] In an embodiment the separate members 50a-d are configured to move independently relative to the channels 13. The separate members 50a-d may be controlled independently of each other. The control system is configured to control each separate member 50a-d independently. It is not necessary for the separate members 50a-d to remain in the formation relative to each other as is shown in Figure 34. This may help to increase the accuracy of controlling the flow rates at different sides of the fluid handling structure 12. The flow rates at different sides of the fluid handling structure 12 may be controlled more independently of each other. In an embodiment the separate member 50a-d are coplanar. The plate that forms the flow adjuster 50 is divided into sections. Alternatively the separate members 50a-d may be arranged to move within different planes. The separate members 50a-d may be stacked on top of each other.

[0148] Figure 35 shows an alternative arrangement of separate members 50a-d of a flow adjuster 50. As shown in Figure 35, each separate member 50a-d may correspond to a respective corner of the fluid handling structure 12. In contrast, the arrangement shown in Figure 34 has separate members 50a-d corresponding to different sides or edges of the fluid handling structure 12. The arrangementshown in Figure 35 allows more independent control of flow rates for respective corners of the fluid handling structure 12.

[0149] As shown in Figure 3, in an embodiment the channels 13 open into the gap between the fluid handling structure 12 and the substrate W (or substrate support WT) at respective gas knife openings 26. The gas knife openings 26 are between the flow adjuster 50 and the gap. In other words, the flow adjuster 50 is internal to the fluid handling structure 12. The flow adjuster 50 is not provided at an external edge of the fluid handling structure 12. The flow adjuster 50 is distanced from the gas knife openings 26. However, the flow adjuster 50 may be located near the gas knife openings 26.

[0150] As explained above, in an embodiment a first series of the channels 13 are configured to supply gas towards the substrate W so as to prevent the liquid from moving from the space 11 to radially outward of the first series of channels 13. The first series of channels 13 may be channels 13 associated with the gas knife openings 26. The first series of channels 13 may be a gas knife series. In an embodiment a second series of the channels 17 are configured to supply a first gas towards the substrate W so as to maintain an environment of the first gas radially outward of the space 11. For example, the second series of channels 17 may be associated with the gas supply openings 27. The first gas may be carbon dioxide. The second series of channels 17 may be referred to as gas supply series.

[0151] In an embodiment the channels comprises a third series of channels configured to extract fluid away from the substrate W. For example, the channels may be associated with the gas recovery openings 28.

[0152] Figure 36 schematically illustrates another arrangement for the flow adjuster 50. As shown in Figure 36, the flow adjuster 50 comprises a plurality of separate members 50a-c. A separate members 50a-c may be controlled independently of each other.

[0153] In an embodiment, a plurality of the separate members 50a-c are arranged to move in different planes. The different members 50a-c may be located at different positions in the Z-direction. The separate members 50a-c may correspond to plates that are effectively stacked relative to each other. The members 50a-c may be moved independently such that they may potentially overlap with each other.

[0154] The present invention may provide a lithographic apparatus. The lithographic apparatus may have any / all of the other features or components of the lithographic apparatus as described above. For example, the lithographic apparatus may optionally comprise at least one or more of a source SO, an illumination system IL, a projection system PS, etc.

[0155] Specifically, the lithographic apparatus may comprise the projection system PS configured to project the radiation beam B towards the region of the surface of a substrate W.

[0156] Although specific reference may be made in this text to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described hereinmay have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat-panel displays, liquidcrystal displays (LCDs), thin-film magnetic heads, etc.

[0157] Where the context allows, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented by instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read only memory (ROM); random access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g. carrier waves, infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such descriptions are merely for convenience and that such actions in fact result from computing devices, processors, controllers, or other devices executing the firmware, software, routines, instructions, etc. and in doing that may cause actuators or other devices to interact with the physical world.

[0158] Although specific reference may be made in this text to embodiments of the invention in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object such as a wafer (or other substrate W) or mask (or other patterning device). These apparatus may be generally referred to as lithographic tools. Such a lithographic tool may use ambient (non- vacuum) conditions.

[0159] 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, where the context allows, is not limited to optical lithography.

[0160] Embodiments include the following numbered clauses:1. A fluid handling system for a lithographic apparatus, the fluid handling system comprising: a fluid handling structure configured to at least partly confine a liquid to an immersion space between a final optical element of a projection system of the lithographic apparatus and a substrate onto which the projection system of the lithographic apparatus is configured to project a patterned beam, the fluid handling structure comprising: a plurality of channels configured to supply fluid towards the substrate and / or extract fluid away from the substrate; a flow adjuster configured to move relative to the channels so as to partially block the channels, thereby partially blocking flow through the channels; and an actuation device configured to move the flow adjuster relative to the channels; anda control system configured to control the actuation device so as to control partial blocking of the channels by the flow adjuster.2. The fluid handling system of clause 1, wherein the flow adjuster is configured such that when a first set of the channels are minimally blocked by the flow adjuster, a second set of the channels are more than minimally blocked by the flow adjuster.3. The fluid handling system of clause 2, wherein the first set of the channels and the second set of the channels are on opposite sides of the immersion space.4. The fluid handling system of any preceding clause, wherein the control system is configured to control the actuation device dependent on a direction of relative movement between the fluid handling structure and the substrate.5. The fluid handling system of any preceding clause, wherein the flow adjuster comprises a plurality of apertures arranged to partially overlap with respective at least one of the channels.6. The fluid handling system of clause 5, wherein the apertures are arranged in a different pattern from the channels.7. The fluid handling system of clause 5 or 6, wherein the apertures are arranged to partially overlap with respective pairs of the channels comprising two openings at non-overlapping distances from the immersion space.8. The fluid handling system of any preceding clause, wherein the flow adjuster comprises a plurality of separate members arranged to partially overlap with the channels.9. The fluid handling system of clause 8, wherein the separate members are configured to move independently controllably relative to the channels.10. The fluid handling system of clause 8 or 9, wherein a plurality of the separate members are coplanar.11. The fluid handling system of any of clauses 8-10, wherein a plurality of the separate members are arranged to move in different planes.12. The fluid handling system of any preceding clause, comprising a restriction plate configured to define an area of at least some of the channels configured to supply gas towards the substrate.13. The fluid handling system of clause 12, wherein the flow adjuster is adjacent to the restriction plate.14. The fluid handling system of clause 12 or 13, wherein the flow adjuster is upstream of the restriction plate.15. The fluid handling system of clause 12 or 13, wherein the flow adjuster is downstream of the restriction plate.16. The fluid handling system of any preceding clause, wherein the channels open into a gap between the fluid handling structure and the substrate at respective openings, wherein the openings are between the flow adjuster and the gap.17. The fluid handling system of any preceding clause, wherein a first series of the channels are configured to supply a first gas towards the substrate so as to prevent the liquid from moving from the immersion space to radially outward of the first series of channels.18. The fluid handling system of any preceding clause, wherein a second series of the channels are configured to supply a second gas towards the substrate so as to maintain an environment of the first gas radially outward of the immersion space.19. The fluid handling system of any preceding clause, wherein a third series of the channels are configured to extract fluid away from the substrate.20. The fluid handling system of any preceding clause, wherein the flow adjuster is configured to move relative to the channels in at least one direction parallel to the substrate.21. The fluid handling system of any preceding clause, wherein the flow adjuster is configured to move translationally and / or rotationally relative to the channels.22. A lithographic apparatus comprising: a projection system configured to project a patterned beam onto a substrate and having a final optical element; a substrate support configured to support the substrate; and the fluid handling system according to any preceding clause.23. The lithographic apparatus of clause 22, comprising: a positioning device configured to move the substrate support and thereby the substrate; and a positioning control system is configured to control the positioning device so that the substrate support is moved along a route comprising scanning movements.24. A method of controlling a fluid handling system for a lithographic apparatus, comprising a fluid handling structure configured to at least partly confine a liquid to an immersion space between a final optical element of a projection system of the lithographic apparatus and a substrate onto which the projection system of the lithographic apparatus is configured to project a patterned beam, the method comprising: supplying fluid towards the substrate and / or extracting fluid away from the substrate through a plurality of channels of the fluid handling structure; and controlling an actuation device to move a flow adjuster relative to channels so as to control partial blocking of the channels by the flow adjuster.25. The method of clause 24, comprising controlling the actuation device to move the flow adjuster within a range of positions such that a first set of the channels are blocked to different extents depending on the position within the range of positions.26. The method of clause 25, wherein the first set of channels are blocked to a minimum extent at a first position within the range of positions, and a second set of the channels are blocked to a minimum extent at a second position, different from the first position, within the range of positions.27. The method of clause 26, wherein the first set of the channels and the second set of the channels are on opposite sides of the immersion space.28. The method of any of clauses 24-27, comprising controlling the actuation device dependent on a direction of relative movement between the fluid handling structure and the substrate.29. The method of any of clauses 24-28, wherein the flow adjuster comprises a plurality of apertures arranged to partially overlap with respective at least one of the channels.30. The method of any of clauses 24-29, comprising independently controlling relative to the channels a plurality of separate members of the flow adjuster that are arranged to partially overlap with the channels.31. The method of any of clauses 24-30, wherein the channels open into a gap between the fluid handling structure and the substrate at respective openings, wherein the openings are between the flow adjuster and the gap.32. The method of any of clauses 24-31, comprising the flow adjuster moving relative to the channels in at least one direction parallel to the substrate.33. The method of any of clauses 24-32, comprising the flow adjuster moving translationally and / or rotationally relative to the channels.34. A method of controlling a lithographic apparatus, the method comprising: moving a substrate along a route comprising scanning movements; and the method of any of clauses 24-33, wherein the actuation device is controlled dependent on the scanning movements.35. A method of manufacturing a semiconductor device, the method comprising the method according to any of clauses 24-34.

[0161] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The 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.

Claims

CLAIMS1. A fluid handling system for a lithographic apparatus, the fluid handling system comprising: a fluid handling structure configured to at least partly confine a liquid to an immersion space between a final optical element of a projection system of the lithographic apparatus and a substrate onto which the projection system of the lithographic apparatus is configured to project a patterned beam, the fluid handling structure comprising: a plurality of channels configured to supply fluid towards the substrate and / or extract fluid away from the substrate; a flow adjuster configured to move relative to the channels so as to partially block the channels, thereby partially blocking flow through the channels; and an actuation device configured to move the flow adjuster relative to the channels; and a control system configured to control the actuation device so as to control partial blocking of the channels by the flow adjuster.

2. The fluid handling system of claim 1, wherein the flow adjuster is configured such that when a first set of the channels are minimally blocked by the flow adjuster, a second set of the channels are more than minimally blocked by the flow adjuster, desirably wherein the first set of the channels and the second set of the channels are on opposite sides of the immersion space.

3. The fluid handling system of claim 1 or 2, wherein the control system is configured to control the actuation device dependent on a direction of relative movement between the fluid handling structure and the substrate, and / or wherein the flow adjuster comprises a plurality of apertures arranged to partially overlap with respective at least one of the channels, desirably wherein the apertures are arranged in a different pattern from the channels, and / or desirably wherein the apertures are arranged to partially overlap with respective pairs of the channels comprising two openings at non-overlapping distances from the immersion space.

4. The fluid handling system of any of the preceding claims, wherein the flow adjuster comprises a plurality of separate members arranged to partially overlap with the channels, desirably wherein the separate members are configured to move independently controllably relative to the channels, and / or desirably wherein a plurality of the separate members are coplanar, and / or desirably wherein a plurality of the separate members are arranged to move in different planes.

5. The fluid handling system of any of the preceding claims, comprising a restriction plate configured to define an area of at least some of the channels configured to supply gas towards the substrate, wherein the flow adjuster is adjacent to the restriction plate, and / or desirably wherein the flow adjuster is upstream of the restriction plate or desirably wherein the flow adjuster is downstream of the restriction plate.

6. The fluid handling system of any of the preceding claims, wherein the channels open into a gap between the fluid handling structure and the substrate at respective openings, wherein the openings are between the flow adjuster and the gap, and / or wherein a first series of the channels are configured to supply a first gas towards the substrate so as to prevent the liquid from moving from the immersion space to radially outward of the first series of channels, and / or wherein a second series of the channels are configured to supply a second gas towards the substrate so as to maintain an environment of the first gas radially outward of the immersion space, and / or wherein a third series of the channels are configured to extract fluid away from the substrate, and / or wherein the flow adjuster is configured to move relative to the channels in at least one direction parallel to the substrate, and / or wherein the flow adjuster is configured to move translationally and / or rotationally relative to the channels.

7. A lithographic apparatus comprising: a projection system configured to project a patterned beam onto a substrate and having a final optical element; a substrate support configured to support the substrate; and the fluid handling system according to any of the preceding claims.

8. The lithographic apparatus of claim 7, comprising: a positioning device configured to move the substrate support and thereby the substrate; and a positioning control system is configured to control the positioning device so that the substrate support is moved along a route comprising scanning movements.

9. A method of controlling a fluid handling system for a lithographic apparatus, comprising a fluid handling structure configured to at least partly confine a liquid to an immersion space between a final optical element of a projection system of the lithographic apparatus and a substrate onto which the projection system of the lithographic apparatus is configured to project a patterned beam, the method comprising: supplying fluid towards the substrate and / or extracting fluid away from the substrate through a plurality of channels of the fluid handling structure; and controlling an actuation device to move a flow adjuster relative to channels so as to controlpartial blocking of the channels by the flow adjuster.

10. The method of claim 9, comprising controlling the actuation device to move the flow adjuster within a range of positions such that a first set of the channels are blocked to different extents depending on the position within the range of positions, desirably wherein the first set of channels are blocked to a minimum extent at a first position within the range of positions, and a second set of the channels are blocked to a minimum extent at a second position, different from the first position, within the range of positions, desirably wherein the first set of the channels and the second set of the channels are on opposite sides of the immersion space.

11. The method of claim 9 or 10, comprising controlling the actuation device dependent on a direction of relative movement between the fluid handling structure and the substrate, and / or wherein the flow adjuster comprises a plurality of apertures arranged to partially overlap with respective at least one of the channels, and / or comprising independently controlling relative to the channels a plurality of separate members of the flow adjuster that are arranged to partially overlap with the channels, and / or wherein the channels open into a gap between the fluid handling structure and the substrate at respective openings, wherein the openings are between the flow adjuster and the gap, and / or comprising the flow adjuster moving relative to the channels in at least one direction parallel to the substrate, and / or comprising the flow adjuster moving translationally and / or rotationally relative to the channels.

12. A method of controlling a lithographic apparatus, the method comprising: moving a substrate along a route comprising scanning movements; and the method of any of claims 9-11, wherein the actuation device is controlled dependent on the scanning movements.

13. A method of manufacturing a semiconductor device, the method comprising the method according to any of claims 9-12.

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