Fluid handling systems and methods

Abstract

Disclosed herein is a fluid handling system comprising a liquid confinement structure, a gas supply conduit and a fluid transport conduit. The liquid confinement structure is configured to confine immersion fluid in a space between at least a part of the liquid confinement structure and a surface of the substrate. The gas supply conduit is configured to supply fluid to the space. The gas supply conduit has a flow controller configured to control the supply of gas from the gas supply conduit. The fluid transport conduit is configured to transport fluid extracted from the space. The fluid transport conduit has a flow meter configured to measure a flow of gas in the fluid transport conduit. In a calibration mode, gas supplied by the flow controller flows directly into the fluid transport conduit via a bypass conduit, which bypasses the liquid confinement structure.

Description

[Technical Field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to European Application No. 22216821.3, filed December 27, 2022, which is incorporated herein by reference in its entirety.

[0002] [Technical field] The present invention relates to a fluid handling system and a method for calibrating a flow meter in a fluid handling system. [Background technology]

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. Lithographic apparatus are used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (also called a "design layout" or "design") from a patterning device (e.g. a mask) onto a layer of radiation-sensitive material (resist) provided on the substrate (e.g. a wafer). Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion at once, and so-called scanners, in which each target portion is irradiated by scanning the pattern through the radiation beam in a predetermined direction (the "scan" direction) while synchronously scanning the substrate parallel to or anti-parallel to this direction.

[0004] As semiconductor manufacturing processes continue to advance, the dimensions of circuit elements are continually shrinking, while the number of functional elements, such as transistors, per device has been steadily increasing for decades, following a trend commonly referred to as "Moore's Law." To keep up with Moore's Law, the semiconductor industry is pursuing technologies capable of producing increasingly fine features. To project patterns onto a substrate, lithography equipment may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be patterned on the substrate. Typical wavelengths currently in use are 365 nm (i-line), 248 nm, 193 nm, and 13.5 nm.

[0005] Further improvement in resolution of finer features can be achieved by providing an immersion liquid with a relatively high refractive index, such as water, over the substrate during exposure. The effect of the immersion liquid is to enable imaging of finer features because the exposure radiation has a shorter wavelength in the immersion liquid than in a gas. The effect of the immersion liquid may also be thought of as increasing the effective numerical aperture (NA) of the system and increasing the depth of focus.

[0006] Immersion fluid may be confined to a localized region (also called an immersion space) between a liquid confinement structure of a lithographic apparatus and a substrate by a fluid handling system. A fluid, for example carbon dioxide gas, is supplied to the immersion space by a flow controller. The supplied fluid is then re-extracted from the immersion space by a fluid transport conduit system, where the flow is measured by a flow meter.

[0007] The performance of a fluid handling system can be sensitive to the settings of the flow of fluid delivered through the immersion space: the accuracy of flow controllers and flow meters can deteriorate over time. Summary of the Invention [Problem to be solved by the invention]

[0008] It is an object of the present invention to provide a fluid handling system and method that provides for increased throughput and / or reduced defects on substrates. [Means for solving the problem]

[0009] According to a first aspect of the present invention, there is provided a fluid handling system comprising a liquid confinement structure, a gas supply conduit, and a fluid transport conduit. The liquid confinement structure is configured to confine immersion fluid in a space between at least a part of the liquid confinement structure and a surface of a substrate. The gas supply conduit is in fluid communication with the liquid confinement structure and is configured to supply fluid to the space. The gas supply conduit has a flow controller configured to control the supply of gas from the gas supply conduit. The fluid transport conduit is in fluid communication with the liquid confinement structure and is configured to transport fluid extracted from the space. The fluid transport conduit has a flow meter configured to measure a flow of gas in the fluid transport conduit. In a calibration mode, the gas supply conduit is in direct fluid communication with the fluid transport conduit via a bypass conduit, the bypass conduit bypassing the liquid confinement structure, and gas supplied by the flow controller flows directly into the fluid transport conduit via the bypass conduit.

[0010] According to a second aspect of the present invention, there is provided a method of calibrating a flow meter in a fluid handling system comprising: a liquid confinement structure configured to confine immersion fluid in a space between at least a part of the liquid confinement structure and a surface of a substrate; a gas supply conduit in fluid communication with the liquid confinement structure configured to supply fluid to the space, the gas supply conduit having a flow controller configured to control supply of gas from the gas supply conduit; and a fluid transport conduit in fluid communication with the liquid confinement structure configured to transport fluid extracted from the space, the fluid transport conduit having a flow meter configured to measure a flow of gas in the fluid transport conduit. The method comprises setting the system to a calibration mode, wherein the gas supply conduit is in direct fluid communication with a fluid transport conduit via a bypass conduit, and comparing the flow of gas measured in the fluid transport conduit to a flow of gas supplied by the flow controller. The bypass conduit bypasses the liquid confinement structure, and gas supplied by the flow controller flows directly into the fluid transport conduit via the bypass conduit.

[0011] 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. [Brief explanation of the drawings]

[0012] Embodiments of the present 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:

[0013] [Figure 1] 1 depicts a schematic diagram of a lithographic apparatus;

[0014] [Figure 2a] 1 shows cross-sectional views of two different versions of a fluid handling system with different features depicted on the left and right sides of each version, which features may extend all around the periphery; [Figure 2b] 1 shows cross-sectional views of two different versions of a fluid handling system with different features depicted on the left and right sides of each version, which features may extend all around the periphery; [Figure 2c] 1 shows cross-sectional views of two different versions of a fluid handling system with different features depicted on the left and right sides of each version, which features may extend all around the periphery; [Figure 2d] 1 shows cross-sectional views of two different versions of a fluid handling system with different features depicted on the left and right sides of each version, which features may extend all around the periphery;

[0015] [Figure 3] 1 shows a fluid handling system comprising a gas supply conduit, a fluid transport conduit and a bypass conduit, wherein in a calibration mode the gas supply conduit is configured to be in direct fluid communication with the fluid transport conduit via the bypass conduit.

[0016] [Figure 4]1 shows a fluid handling system comprising a gas supply conduit, a plurality of fluid transport conduits and a corresponding plurality of bypass conduits, wherein in a calibration mode, each bypass conduit is configured such that the gas supply conduit is in direct fluid communication with one of the plurality of fluid transport conduits via the corresponding bypass conduit.

[0017] [Figure 5] 1 shows a fluid handling system comprising a gas supply conduit, a plurality of fluid transport conduits and a bypass conduit, the bypass conduit being configured such that in a calibration mode the gas supply conduit is in direct fluid communication with one of the plurality of fluid transport conduits via the bypass conduit.

[0018] The depicted features are not necessarily to scale, and the depicted size and / or arrangement is not intended to limit the present invention. It will be understood that the drawings include optional features that may not be essential to the present invention. Furthermore, not all features of a device may be shown in each drawing, and a drawing may show only some of the components relevant to the description of a particular feature. DETAILED DESCRIPTION OF THE INVENTION

[0019] In this document, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (eg, wavelengths of 365, 248, 193, 157 or 126 nm).

[0020] The terms "reticle," "mask," or "patterning device," as used herein, may be broadly interpreted to refer to any general patterning device that can be used to impart an incident radiation beam with a patterned cross-section that corresponds to the pattern to be created in a target portion of a substrate. The term "light valve" may also be used in this context. Beyond the classic mask (transmissive or reflective; binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0021] Figure 1 illustrates a schematic diagram of a lithographic apparatus. The lithographic apparatus includes an illumination system (also called an illuminator) IL configured to condition a radiation beam B (e.g., UV or DUV radiation), a mask support (e.g., mask table) MT constructed to support a patterning device (e.g., mask) MA and connected to a first positioner PM configured to precisely position the patterning device MA according to certain parameters, a substrate support (e.g., substrate table) WT constructed to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to precisely position the substrate support WT according to certain parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies) on the substrate W. A controller 500 controls the overall operation of the apparatus. The controller 500 may be a centralized control system or a system of multiple separate sub-controllers within the various subsystems of the lithographic apparatus.

[0022] In operation, the illumination system IL receives the radiation beam B from the radiation source SO, for example via the beam delivery system BD. The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic and / or other types of optical components, or any combination thereof, for directing, shaping and / or controlling the radiation. The illuminator IL may be used to condition the radiation beam B at the plane of the patterning device MA, so that the radiation beam B has a desired spatial and angular intensity distribution in its cross-section.

[0023] The term "projection system" PS as used herein should be interpreted broadly as encompassing various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, depending on the exposure radiation used and / or other factors such as the use of an immersion liquid or the use of a vacuum. Any use of the term "projection lens" herein may be considered as synonymous with the more general term "projection system" PS.

[0024] The lithographic apparatus is of a type in which the substrate W is at least partially covered with an immersion liquid (e.g. water) having a relatively high refractive index, filling an immersion space 11 between the projection system PS and the substrate W, which is also known as immersion lithography. Further details about immersion techniques are found in U.S. Patent No. 6,952,253, which is incorporated herein by reference.

[0025] The lithographic apparatus may be of a type having two or more substrate supports WT (also known as "dual stage") In such a "multi-stage" apparatus, the substrate supports WT may be used in parallel, and / or a substrate W placed on one substrate support WT may be undergoing preparation steps for a subsequent exposure of the substrate W, while another substrate W on another substrate support WT may be used to expose a pattern for the other substrate W.

[0026] In addition to the substrate support WT, the lithographic apparatus may comprise a measurement stage (not shown). The measurement stage is configured to hold a sensor and / or a cleaning device. The sensor may be configured 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 configured to clean part of the lithographic apparatus, for example part of the projection system PS or part of a system for providing immersion liquid. The measurement stage may move below the projection system PS when the substrate support WT is spaced apart from the projection system PS.

[0027] In operation, a radiation beam B is incident on a patterning device (e.g., mask) MA, which is held on a mask support MT, and is patterned according to a pattern (design layout) present on the patterning device MA. Having passed through the patterning device 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 the position measurement system IF, the substrate support WT can be precisely moved, for example, so that different target portions C are positioned at focused and aligned positions in the path of the radiation beam B. Similarly, the patterning device MA may be precisely positioned with respect to the path of the radiation beam B using the first positioner PM and possibly further position sensors (not explicitly shown in FIG. 1 ). The patterning device MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the substrate alignment marks P1, P2 are illustrated as occupying dedicated target portions, they may also be located in spaces between the target portions. When the substrate alignment marks P1, P2 are located between target portions C, they are known as scribe-lane alignment marks.

[0028] For clarity of the present invention, a Cartesian coordinate system is used. The Cartesian coordinate system has three axes: x, y, and z. Each of the three axes is orthogonal to the other two. Rotation about the x-axis is called Rx rotation, rotation about the y-axis is called Ry rotation, and rotation about the z-axis is called Rz rotation. The x- and y-axes define a horizontal plane, and the z-axis is vertical. The Cartesian coordinate system is not a limitation of the present invention and is used for clarity only. Alternatively, another coordinate system, such as a cylindrical coordinate system, may be used for clarity of the present invention. The orientation of the Cartesian coordinate system may be different, for example, the z-axis may have a component along the horizontal plane.

[0029] Immersion techniques have been introduced into lithography systems to improve the resolution of finer features. In an immersion lithography apparatus, a layer of immersion liquid, having a relatively high refractive index, is interposed in an immersion space 11 between the apparatus's projection system PS (through which a patterned beam is projected onto the substrate W) and the substrate W. The immersion liquid covers at least a portion of the substrate W that is located below the final element of the projection system PS. Thus, at least the part of the substrate W that is to be exposed is immersed in the immersion liquid.

[0030] In commercial immersion lithography, the immersion liquid is water. Typically, this water is highly pure distilled water, such as ultrapure water (UPW), which is widely used in semiconductor manufacturing facilities. In immersion systems, UPW is often purified and may undergo additional processing steps before being supplied to the immersion space 11 as the immersion liquid. Besides water, other liquids with high refractive indices can be used as immersion liquids, such as hydrocarbons, such as fluorocarbons, and / or aqueous solutions. Furthermore, fluids other than liquids are also envisioned for use in immersion lithography.

[0031] Description is made herein of localized immersion where, in use, immersion liquid is confined in an immersion space 11 between the final element 100 and a surface facing the final element 100. The facing surface is the surface of the substrate W or a surface of the support stage (or substrate support WT) that is flush with the surface of the substrate W. (Note that in the following text, references to the surface of the substrate W will refer in addition to or instead to the surface of the substrate support WT, unless otherwise stated, 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 immersion space 11. The immersion space 11, which is filled with immersion liquid, is narrower in plan than the top surface of the substrate W, and the immersion space 11 remains substantially stationary relative to the projection system PS while the substrate W and substrate support WT move underneath.

[0032] Other immersion systems are envisaged, such as non-enclosed immersion systems (so-called "all wet" immersion systems) and bath-type immersion. In a non-enclosed immersion system, the immersion liquid covers more than the surface below the final element 100. The liquid outside the immersion space 11 is present as a thin film. The liquid may cover the entire surface of the substrate W, or it may cover the substrate W and a substrate support WT that is flush with the substrate W. In a bath-type system, the substrate W is completely immersed in a bath of immersion liquid.

[0033] The fluid handling structure 12 is a structure that supplies immersion liquid to and removes immersion liquid from the immersion space 11, thereby confining the immersion liquid to the immersion space 11. It includes features that form part of a fluid supply system. The arrangement disclosed in PCT Patent Application Publication No. WO 99 / 49504 is an early fluid handling structure that comprises pipes that supply or remove immersion liquid to and from the immersion space 11 and that operate in response to relative movement of a stage directly below the projection system PS. In more recent designs, the fluid handling structure extends along at least part of the boundary of the immersion space 11 between the final element of the projection system PS and the substrate support WT or substrate W, and partly defines the immersion space 11.

[0034] The fluid handling structure 12 may have a choice of different functions, each derived from a corresponding feature that enables the fluid handling structure 12 to perform that function. The fluid handling structure 12 may be referred to by a number of different terms to describe each function, such as barrier member, seal member, fluid supply system, fluid removal system, liquid confinement structure, etc.

[0035] As a barrier member, the fluid handling structure 12 provides a barrier to the flow of immersion liquid from the immersion space 11. As a liquid confinement structure, it confines the immersion liquid to the immersion space 11. As a seal member, a sealing feature of the fluid handling structure 12 forms a seal to confine the immersion liquid to the immersion space 11. The sealing feature may comprise an additional gas flow from an opening in the surface of the seal member, such as a gas knife.

[0036] In an embodiment, the fluid handling structure 12 may supply immersion fluid and therefore may be a fluid supply system.

[0037] In an embodiment, the fluid handling structure 12 may at least partly confine the immersion fluid and thereby be a fluid confinement system.

[0038] In an embodiment, the fluid handling structure 12 provides a barrier to the immersion fluid and may thereby be a barrier member, such as a fluid confinement structure.

[0039] In an embodiment, the fluid handling structure 12 may generate or use a flow of gas, for example to help control the flow and / or position of the immersion fluid.

[0040] The flow of gas may form a seal to confine the immersion fluid and so the fluid handling structure 12 may be referred to as a seal member, and such a seal member may be a fluid confinement structure.

[0041] In an embodiment, an immersion liquid is used as the immersion fluid, in which case the fluid handling structure 12 may be a liquid handling system. In the context of the above description, references in this paragraph to features defined with respect to a fluid may be understood to include features defined with respect to a liquid.

[0042] The lithographic apparatus has a projection system PS. During exposure of a substrate W, the projection system PS projects a patterned beam of radiation onto the substrate W. The path of the radiation beam B passes from the projection system PS through immersion liquid that is confined between the projection system PS and the substrate W by a fluid handling structure 12, before reaching the substrate W. The projection system PS has a lens element at the end of the beam path that is in contact with the immersion liquid. The lens element in contact with the immersion liquid may be referred to as the "final lens element" or "final element". The final element 100 is at least partly surrounded by the fluid handling structure 12. The fluid handling structure 12 may confine immersion liquid below the final element 100 and above a facing surface.

[0043] Figures 2a, 2b, 2c and 2d show different features that may be present in variants of the fluid handling system. These designs may share some of the same features as Figures 2a, 2b, 2c and 2d unless otherwise stated. The features described herein may be selected individually or in combination as shown or as needed. The figures show different versions of the fluid handling system, with different features depicted on the left and right sides, which may extend around the entire circumference. Thus, for example, a fluid handling system may have the same feature extending around the entire circumference. For example, a fluid handling system may only have the feature on the left side of Figure 2a, the right side of Figure 2a, the left side of Figure 2b, the right side of Figure 2b, the left side of Figure 2c, the right side of Figure 2c, the left side of Figure 2d or the right side of Figure 2d. Alternatively, a fluid handling system may comprise any combination of features from these figures, at different positions around the circumference. The fluid handling system may comprise a fluid handling structure 12 as described in the variants below.

[0044] Figure 2a shows a fluid handling structure 12 around the bottom surface of a final element 100. The final element 100 has an inverted truncated conical shape. The truncated conical shape has a flat bottom surface and a conical surface. The truncated conical shape protrudes from the flat surface and has a flat bottom surface. The flat bottom surface is the optically active part of the bottom surface of the final element 100 and 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 truncated conical shape. The fluid handling structure 12 has an inner surface facing the conical surface of the truncated conical shape. The inner surface and the conical surface may have complementary shapes. The top surface of the fluid handling structure 12 may be substantially flat. The fluid handling structure 12 may be arranged to fit the truncated conical shape of the final element 100. The bottom surface of the fluid handling structure 12 may be a substantially flat surface which, in use, may be parallel to a facing surface of the substrate support WT and / or substrate W. The bottom surface of the fluid handling structure 12 may therefore be referred to as the 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.

[0045] The fluid handling structure 12 extends closer to the facing surfaces of the substrate W and substrate support WT than the final element 100. An immersion space 11 is therefore defined between an inner surface of the fluid handling structure 12, a flat surface of the frusto-conical portion and the facing surface. During use, the immersion space 11 is filled with immersion liquid. The immersion liquid fills at least part of the buffer space between the complementary surfaces between the final element 100 and the fluid handling structure 12, and in an embodiment fills at least part of the space between the complementary inner surface and the conical surface.

[0046] Immersion liquid is supplied to the immersion space 11 through openings formed in the surface of the fluid handling structure 12. The immersion liquid may be supplied through supply openings 20 in an inner surface of the fluid handling structure 12. Alternatively or additionally, the immersion liquid is supplied from a lower supply opening 23 formed in a bottom surface of the fluid handling structure 12. The lower supply opening 23 may surround the path of the radiation beam B and may be formed by a series of openings in an array, or by a single slit. The immersion liquid is supplied to fill the immersion space 11 such that the flow through the immersion space 11 below the projection system PS is laminar. Supply of immersion liquid from the lower supply opening 23 further prevents the introduction of gas bubbles into the immersion space 11. This supply of immersion liquid may act as a liquid seal.

[0047] Immersion liquid may be recovered from recovery openings 21 formed in the inner surface. Recovery of immersion liquid through the recovery openings 21 may be due to the application of negative pressure, or recovery through the recovery openings 21 may be the result of the velocity of immersion liquid passing through the immersion space 11, or both. The recovery openings 21 may be arranged opposite the supply openings 20 in plan view. Additionally or alternatively, immersion liquid may be recovered through an overflow recovery part 24 arranged on the top surface of the fluid handling structure 12. The supply openings 20 and the recovery openings 21 may have interchangeable functions (i.e. the liquid flow directions are reversed). This allows the flow direction to be changed depending on the relative movement of the fluid handling structure 12 and the substrate W.

[0048] Additionally or alternatively, immersion liquid may be recovered from below the fluid handling structure 12 through recovery openings 25 formed in the bottom surface of the fluid handling structure 12. The recovery openings 25 may function to maintain a meniscus 33 of immersion liquid in the fluid handling structure 12. The meniscus 33 is formed between the fluid handling structure 12 and the facing surface and acts as a boundary between the liquid space and the gaseous external environment. The recovery openings 25 may be a porous plate that may recover immersion liquid in a substantially single-phase flow. The recovery openings in the bottom surface may be a series of fixed openings 32 for recovering immersion liquid. The fixed openings 32 may recover immersion liquid in a two-phase flow.

[0049] Optionally, radially outwardly relative to the inner surface of the fluid handling structure 12 is a gas knife opening 26. Gas may be supplied at high velocity through the gas knife opening 26 to assist liquid confinement of the immersion liquid in the immersion space 11. The supplied gas may be humidified and may comprise substantially carbon dioxide. Radially outwardly of the gas knife opening 26 are gas recovery openings 28 for recovering gas supplied through the gas knife opening 26.

[0050] Further openings may be provided at the bottom surface of the fluid handling structure 12, i.e. the surface of the fluid handling structure 12 facing the substrate W, e.g. opening to atmosphere, a gas source or vacuum. An example of such an optional further opening 50 is shown by the dashed line on the right-hand side of Figure 2a. As shown, the further openings 50 may be supply or extraction members, indicated by double arrows. For example, if configured as supply members, the further openings 50 may be connected to a liquid supply or a gas supply, as well as to either of the supply members. Alternatively, if configured as extraction members, the further openings 50 are used to extract fluid and may be connected to, e.g. atmosphere, a gas source or vacuum. For example, at least one further opening 50 may be present between the gas knife opening 26 and the gas recovery opening 28, and / or between the fixed opening 32 and the gas knife opening 26.

[0051] Two different versions of the fluid handling structure 12, on the left and right of Figure 2a, have a fixed meniscus 33. The version of the fluid handling structure 12 on the right of Figure 2a has a fixed position of the fixed opening 32 and may therefore have a fixed meniscus 33 in a substantially fixed position relative to the final element 100. The version of the fluid handling structure 12 on the left of Figure 2a may have a fixed meniscus 33 below the recovery opening 25, and the meniscus 33 may move along the length and / or width of the recovery opening 25. To irradiate the radiation beam B onto the entire surface of the substrate W during exposure, the substrate support WT, which supports the substrate W, moves relative to the projection system PS. To maximise the throughput of substrates W exposed by the lithographic apparatus, the substrate support WT (and also the substrate W) is moved as fast as possible. However, there is a critical relative speed (often called the critical scan speed) at which the meniscus 33 between the fluid handling structure 12 and the substrate W becomes unstable. An unstable meniscus 33 increases the risk of losing immersion liquid, for example in the form of one or more droplets. Furthermore, an unstable meniscus 33 increases the risk of trapping gas bubbles in the immersion liquid, particularly as the trapped immersion liquid crosses the edge of the substrate W.

[0052] Liquid droplets present on the surface of the substrate W can impart thermal loads and cause defects. Droplets can evaporate, leaving dry spots, displacing transported contaminants such as particles, collide with a larger body of immersion liquid and cause bubbles in that body, or evaporate and impart thermal loads to the surface on which they are located. Such thermal loads can cause distortions and positioning errors when that surface is relevant for positioning components of the lithographic apparatus relative to the substrate W being imaged. Therefore, the formation of liquid droplets on the surface is undesirable. To avoid the formation of such droplets, the speed of the substrate support WT is limited to a critical scan speed at which the meniscus 33 remains stable. This limits the throughput of the lithographic apparatus.

[0053] 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. The spring 60 can therefore 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 incorporated herein by reference in its entirety. Other biasing devices, for example using electromagnetic forces, may also be suitable. Although the spring 60 is shown on the left-hand side of Figure 2a, it is optional and does not need to be included together with the other features of the left-hand side of Figure 2a. The spring 60 is not shown in any of the other figures, but may also be included in other variations of the fluid handling system described in relation to Figures 2a, 2b, 2c or 2d.

[0054] Figure 2b shows, on the left and right, two different versions of the fluid handling structure 12, allowing movement of the meniscus 33 relative to the final element 100. The meniscus 33 may move in the direction of the moving substrate W. This reduces the relative speed between the meniscus 33 and the moving substrate W, which may improve stability and reduce the risk of breakage of the meniscus 33. The speed of the substrate W at which the meniscus 33 breaks increases, allowing for faster movement of the substrate W under the projection system PS. This improves throughput.

[0055] Features shown in Figure 2b that are in common with Figure 2a share the same reference numbers. The fluid handling structure 12 has an inner surface complementary to the conical surface of the frusto-conical shape. The bottom surface of the fluid handling structure 12 is closer to the opposing surface than the bottom flat surface of the frusto-conical shape.

[0056] Immersion liquid is supplied to the immersion space 11 through supply openings 34 formed in the inner surface of the fluid handling structure 12. The supply openings 34 are arranged towards the bottom of the inner surface, for example below the base of the frusto-conical shape. The supply openings 34 are arranged around the periphery of the inner surface and are spaced around the path of the radiation beam B.

[0057] Immersion liquid is recovered from the immersion space 11 through recovery openings 25 in the bottom surface of the fluid handling structure 12. As the facing surface moves beneath the fluid handling structure 12, a meniscus 33 moves over the surface of the recovery openings 25 in the same direction as the movement of the facing surface. The recovery openings 25 may be formed of a porous material. The immersion liquid may be recovered in a single phase. The immersion liquid may be recovered in a two-phase flow. The two-phase flow is received in a chamber 35 inside the fluid handling structure 12 where it is separated into liquid and gas. The liquid and gas are recovered from the chamber 35 through separate channels 36, 38.

[0058] An inner periphery 39 of the bottom surface of the fluid handling structure 12 extends away from the inner surface towards the immersion space 11 to form a plate 40. The inner periphery 39 forms a small opening which can be sized to suit the shape and size of the radiation beam B. The plate 40 may act to isolate the immersion liquid on either side of it. The supplied immersion liquid flows inward towards the opening, passes through the inner opening, then flows underneath the plate 40 and radially outwards towards the periphery of the recovery opening 25.

[0059] The fluid handling structure 12 may consist of two parts, an inner part 12a and an outer part 12b, as shown on the right hand side of Figure 2b. The inner part 12a and the outer part 12b may move relative to each other mainly in a plane parallel to their facing faces. The inner part 12a may have a supply opening 34 and may have an overflow collection part 24. The outer part 12b may have a plate 40 and a collection opening 25. The inner part 12a may have an intermediate collection part 42 for collecting immersion liquid flowing between the inner part 12a and the outer part 12b.

[0060] The two different versions of the fluid handling structure in Figure 2b allow movement of the meniscus 33 in the same direction as the substrate W, allowing for faster scanning speeds and improved throughput of the lithographic apparatus. However, the movement of the meniscus 33 at the surface of the recovery opening 25 in the fluid handling structure 12 on the left side of Figure 2b may be slow. The fluid handling structure 12 on the right side of Figure 2b can move the meniscus 33 faster by moving the outer part 12b relative to the inner part 12a and the final element 100. However, it may be difficult to control the intermediate recovery part 42 to ensure that enough immersion liquid is supplied between the inner part 12a and the outer part 12b to prevent them from contacting each other.

[0061] Figure 2c shows, on the left and right, two different versions of a fluid handling structure 12 which can be used to pin the meniscus 33 of immersion liquid to the fluid handling structure 12, as described above in relation to Figures 2a and / or 2b. Features shown in Figure 2c that are in common with Figures 2a and / or 2b share the same reference numbers.

[0062] The fluid handling structure 12 has an inner surface complementary to the conical surface of the frustoconical shape. The bottom surface of the fluid handling structure 12 is closer to the facing surface than the flat bottom surface of the frustoconical shape. Immersion liquid is supplied to the immersion space 11 through openings formed in the surface of the fluid handling structure 12. The immersion liquid may be supplied through supply openings 34 in the inner surface of the fluid handling structure 12. Alternatively or additionally, the immersion liquid may be supplied through supply openings 20 in the inner surface of the fluid handling structure 12. Alternatively or additionally, the immersion liquid may be supplied through lower supply openings 23. The immersion liquid may be recovered via an extraction member, for example via recovery openings 21 and / or overflow recovery part 24 formed in the inner surface of the fluid handling structure 12 and / or one or more openings in the surface of the fluid handling structure 12, as described below.

[0063] Two different versions of the fluid handling structure 12, on the left and right of Figure 2c, fix the meniscus 33. The version of the fluid handling structure 12 on the right of Figure 2c has a fixed position of the collection opening 32a and may therefore fix the meniscus 33 in a substantially fixed position relative to the final element 100. The version of the fluid handling structure 12 on the left of Figure 2c may fix the meniscus 33 below the collection opening 25 and the meniscus 33 may move along the length and / or width of the collection opening 25.

[0064] 2c。 As described above in relation to Figure 2b, the inner periphery of the bottom surface of the fluid handling structure 12 may extend away from the inner surface towards the immersion space 11 to form a plate 40, as shown on the left side. As mentioned above, this may form small openings on either side of which the immersion liquid may be isolated and / or may allow the immersion liquid to flow inwards towards the opening, and after passing through the inner opening, may flow radially outwards under the plate 40 towards the periphery of the recovery opening 25. This feature is shown on the left side of Figure 2c, but is optionally combined with other features as shown. Preferably, as shown on the left side, immersion liquid is supplied to the immersion space 11 through supply openings 34 formed in the inner surface of the fluid handling structure 12. The supply openings 34 are arranged towards the bottom of the inner surface, e.g. below the bottom surface of the frusto-conical shape. The supply openings 34 are arranged around the inner surface and are spaced around the path of the radiation beam B. Alternatively or additionally, immersion liquid may be supplied through supply openings 20 in the inner surface of the fluid handling structure 12. Alternatively or additionally, immersion liquid is supplied through lower supply openings 23. Supply openings 34 are the preferred liquid supply source, although any combination of supply openings 34, supply openings 20 and / or lower supply openings 23 may be provided.

[0065] As shown on the left side of Figure 2c, the fluid handling system may comprise a fluid handling structure 12 as described above and another apparatus 3000. The fluid handling structure 12 may have extraction members, such as recovery openings 25, and liquid supply openings, such as lower supply openings 23. It will be appreciated that the fluid handling structure 12 may comprise any configuration disclosed in relation to the left side of Figure 2a, the right side of Figure 2a, the left side of Figure 2b, the right side of Figure 2b or (as described below) the right side of Figure 2c.

[0066] The further apparatus 3000 may be called a droplet capture apparatus. The further apparatus 3000 is provided to reduce the presence of liquid on the surface of the substrate W after the fluid handling structure 12 has moved over the surface of the substrate W. The further apparatus 3000 may comprise a liquid supply member 3010 and at least one extraction member 3020. The at least one extraction member 3020 may be shaped to surround the at least one supply member 3010 in a plan view. The at least one liquid supply member 3010 may be configured to supply further liquid to a space 3110 between at least part of the further apparatus 3000 and the surface of the substrate W. The further apparatus 3000 may be configured to recover at least some of the liquid via the at least one extraction member 3020. The further apparatus 3000 may be used to combine any liquid remaining on the surface of the substrate W with the liquid in the space 3110, and then the further apparatus 3000 may be used to extract the liquid so that the amount of liquid remaining on the surface of the substrate W is reduced.

[0067] In Figure 2c the further apparatus 3000 is shown as a separate apparatus from the fluid handling structure 12. The further apparatus 3000 may be located adjacent to the fluid handling structure 12. Alternatively, the further apparatus 3000 may be part of, i.e. integrated into, the fluid handling structure 12.

[0068] The alternative apparatus 3000 may be configured to provide a liquid to the space 3110 other than the liquid provided by the fluid handling structure 12 .

[0069] Additionally or alternatively, the fluid handling structure 12 may have components as shown on the right-hand side of Figure 2c. More specifically, the fluid handling structure 12 may comprise 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 in a surface of the fluid handling structure 12. The gas supply opening 27a is optional. The at least one liquid supply member may be the same as the lower supply opening 23 in the bottom surface of the fluid handling structure 12 described above, or the supply openings 20 or liquid supply openings 34 formed in an internal surface of the fluid handling structure 12 described in relation to the left-hand side of Figure 2b. The liquid supply member, extraction members and gas supply members may be formed in a surface of the fluid handling structure 12. In particular, these components may be formed in the surface of the fluid handling structure 12 facing the substrate W, i.e. the bottom surface of the fluid handling structure 12.

[0070] 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 through which the fluid handling structure 12 extracts fluid from below the fluid handling structure 12, e.g., recovery opening 32a, and may recover immersion liquid in a single-phase flow. The other of the two extraction members, e.g., recovery opening 32b, may recover immersion liquid as a two-phase extractor. The porous material 37 does not have to be flush with the bottom surface of the fluid handling structure 12.

[0071] In particular, the fluid handling structure 12 may comprise a liquid supply member (e.g. below the supply openings 23), a first extraction member (e.g. recovery openings 32a) radially outward of the liquid supply member, a first gas supply member (e.g. gas supply openings 27a) radially outward of the first extraction member, a second extraction member (e.g. recovery openings 32b) radially outward of the first gas supply member, and a second gas supply member (e.g. gas supply openings 27b) radially outward of the second extraction member. Similar to Figure 2a, and as described above (in relation to the fluid handling structure 12), there may be further openings in the bottom surface of the fluid handling structure 12, for example open to atmosphere, a gas source or vacuum.

[0072] For example, at least one further opening (not shown) may be provided in a bottom surface of the fluid handling structure 12. The further opening is optional. The further opening may be located between the first extraction member (e.g. collection openings 32a) and the first gas supply member (e.g. gas supply openings 27a), as described in the configurations above. Alternatively or additionally, the further opening may be located between the second extraction member (e.g. collection openings 32b) and the second gas supply member (e.g. gas supply openings 27b), as described in the configurations above. The further opening may be the same as the further opening 50 described above.

[0073] Optionally, the fluid handling structure 12 comprises a recess 29. The recess 29 may be provided between the collection openings 32a and 32b, or between the gas supply openings 27a and 32b. The shape of the recess 29 may be uniform around the periphery of the fluid handling structure 12 or may optionally include a slope. If a recess 29 is provided between the collection openings 32a and 32b, the gas supply openings 27b may be provided on a slope as shown in Figure 2c. If a recess 29 is provided between the supply openings 27a and 32b, the gas supply openings 27b may be provided in a part of the slope or bottom surface of the fluid handling structure 12 that 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 different to change the effect of gas supplied from the gas supply member on the fluid below the fluid handling structure 12.

[0074] Figure 2d shows, in its left and right halves, two different versions of the fluid handling structure 12. The fluid handling structure 12 in the left half of Figure 2d comprises a liquid injection buffer 41a that holds a buffer amount of immersion liquid, and liquid injection holes 41 that supply immersion liquid from the liquid injection buffer to the space 11. Outer the liquid injection holes 41 are inner liquid recovery openings 43 for directing liquid to an inner recovery buffer 43a that comprises a porous member. Recesses 29 similar to those described in relation to Figure 2c are provided outer the inner liquid recovery openings 43. Outer the recesses 29, in the underside of the fluid handling structure 12, are gas guide grooves 44 into which outer recovery holes 44a open. The outer recovery holes 44a direct the two-phase recovery flow to an outer recovery buffer 44b, which also comprises a porous member. At the outermost side there are gas sealing holes 45 which provide communication between the gas sealing buffer volume 45a and the space below the fluid handling structure 12 to provide gas flow for containing the immersion liquid.

[0075] The fluid handling structure 12 in the right half of Figure 2d has a liquid supply opening 20 in its inner sloping surface. In its underside there are (from the inside to the outside) an extraction opening 25 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 buffer space groove in the underside of the fluid handling structure 12. The outermost part of the fluid handling structure 12 is stepped to provide a larger separation between the fluid handling structure 12 and the substrate W.

[0076] 2a-2d illustrate examples of different configurations that can be used as part of a fluid handling system. While the above examples refer to specific extraction and recovery elements, it is understood that exact types of extraction and / or recovery elements need not necessarily be used. In some cases, different terms are used to indicate the location of the elements, but the same function may be provided. Examples of extraction elements include recovery opening 21, overflow recovery section 24, recovery opening 25 (which may comprise a porous plate and / or chamber 35), gas recovery opening 28, fixed opening 32, recovery opening 32a, recovery opening 32b, and / or intermediate recovery section 42. Examples of supply elements include supply opening 20, lower supply opening 23, gas knife opening 26, gas supply opening 27a, gas supply opening 27b, and / or supply opening 34. In general, extraction elements used to extract / recover fluids, liquids, or gases are interchangeable with other examples used to extract / recover fluids, liquids, or gases, respectively. Similarly, supply members used to supply a fluid, liquid, or gas are interchangeable with other examples used to supply a fluid, liquid, or gas, respectively. An extraction member may extract / withdraw a fluid, liquid, or gas from a space by connecting it to a negative pressure that draws the fluid, liquid, or gas into the extraction member. A supply member may supply a fluid, liquid, or gas to a space by connecting it to an associated supply source.

[0077] Figure 3 shows a fluid handling system comprising a fluid handling structure or liquid confinement structure 12, a gas supply conduit 70, a fluid transport conduit 80 and a bypass conduit 90. The liquid confinement structure 12 is configured to confine immersion fluid to an immersion space 11 between at least part of the liquid confinement structure 12 and the surface of the substrate. For example, the fluid handling system, and / or in particular the fluid handling structure or liquid confinement structure 12 and the corresponding immersion space 11 may be as described above with reference to any of Figures 1 and 2a-d.

[0078] The gas supply conduit 70 is in fluid communication with the liquid confinement structure 12. In particular, the gas supply conduit 70 is configured to supply a fluid, for example a gas such as carbon dioxide, to the immersion space 11. The gas supply conduit 70 has a flow controller 71 configured to control the supply of the fluid from the gas supply conduit 70. For example, the flow controller 71 may control the flow rate of the fluid through the gas supply conduit 70. The flow controller 71 is optionally a mass flow controller.

[0079] The fluid transport conduit 80 is in fluid communication with the liquid confinement structure 12. In particular, the fluid transport conduit 80 is configured to transport a fluid, for example a gas, that is extracted from the immersion space 11. The fluid extracted from the immersion space 11 may be a gas, for example carbon dioxide. In particular, the fluid extracted from the immersion space 11 is preferably a fluid that is supplied to the immersion space 11 by the gas supply conduit 70. The fluid transport conduit 80 comprises a flow meter configured to measure the flow of the fluid in the fluid transport conduit 80.

[0080] In the production mode, fluid supplied by the flow controller 71 flows through the liquid confinement structure 12 to the fluid transport conduit 80. In other words, in the production mode, the gas supply conduit 70 supplies fluid to the immersion space 11 and fluid from the immersion space 11 is transported by the fluid transport conduit 80. In the production mode, the flow meter 81 is configured to measure the flow of fluid through the fluid transport conduit 80. Thus, the flow meter 81 may measure the flow of fluid, such as gas and / or liquid, extracted from the immersion space 11 between the liquid confinement structure 12 and the surface of the substrate. The flow meter 81 is optionally a gas flow meter. Preferably, the flow meter 81 is configured to measure the flow rate of the fluid, and more preferably, the flow meter 81 is configured to measure the mass flow rate.

[0081] The performance of a fluid handling system may depend on the flow of fluid into, through and / or out of the liquid confinement structure 12. In particular, it may be beneficial to accurately measure the flow of fluid supplied to and / or transported from the immersion space 11.

[0082] To ensure that the flow measurements of the flow controller 71 supplying fluid are accurate, measurements of the fluid pressure downstream of the flow controller 71 may be made during normal operation. The geometry and pressure-flow relationship in this part of the system is relatively simple and may be linear. Pressure measurements can therefore be used to determine whether the flow controller 71 is providing fluid flow with sufficient accuracy. However, the pressure-flow relationship through the liquid confinement structure 12 is more complex. This is because the flow in this part of the system is determined not only by the geometry of the hardware, but also by a variety of other factors, including the amount of fluid supplied to the immersion space 11, the gap between the liquid confinement structure 12 and the sample, and the contact angle of the sample. For this reason, inaccuracies in the flow meter 81, for example due to drift over time, cannot be accurately determined by observing changes in pressure in the fluid transport conduit system 80.

[0083] It is therefore desirable to provide a means to ensure that the flow meter 81 is calibrated so that the flow of fluid through the fluid transport conduit 80 is known with sufficient accuracy. This may be achieved by a calibration mode of the fluid handling system.

[0084] In the calibration mode, the gas supply conduit 70 is in direct fluid communication with the fluid transport conduit 80 via the bypass conduit 90. The bypass conduit 90 bypasses the liquid confinement structure 12. In other words, in the calibration mode, the gas supply conduit 70 supplies fluid to the bypass conduit 90 instead of supplying fluid to the immersion space 11. The bypass conduit 90 transports fluid from the gas supply conduit 70 to the fluid transport conduit 80.

[0085] In the calibration mode, the fluid supplied by the flow controller 71 flows directly to the fluid transport conduit 80 via the bypass conduit 90. The calibration mode allows for calibration of the flow meter 81 by comparing the fluid flow measured in the fluid transport conduit 80 with the gas flow supplied by the flow controller 71.

[0086] In production mode, due to the complexity of the geometry and flow of the immersion space 11 defined by the liquid confinement structure 12 and the sample, the relationship between the fluid flow supplied by the flow controller 71 in the gas supply conduit 70 and the fluid flow measured by the flow meter 81 in the fluid transport conduit 80 may not be known. In calibration mode, fluid flowing from the gas supply conduit 70 to the fluid transport conduit 80 bypasses the immersion space 11. The geometry and flow of the bypass conduit 90 are simpler than those of the immersion space 11. The bypass conduit 90 provides a direct flow path between the flow controller 71 and the flow meter 81, such that all fluid from the flow controller 71 is provided to the flow meter 81 through the bypass conduit 90. In other words, in calibration mode, there may be no flow outlet in the system between the flow controller 71 and the flow meter 81. Therefore, a direct comparison may be made between the flow provided by the flow controller 71 and the flow measured by the flow meter 81. This situation does not apply during normal operation, for example in production mode. This is because the immersion space 11 is an open environment and the flow may leak or be discharged through other outlets, and not all of the fluid will reach the flow meter 81. Therefore, in the calibration mode, it is possible to know the relationship between the fluid flow supplied by the flow controller 71 in the gas supply conduit 70 and the fluid flow measured by the flow meter 81 in the fluid transport conduit 80. Therefore, if the flow controller 71 is calibrated, it is possible to determine in the calibration mode whether the flow meter 81 is calibrated.

[0087] The fluid handling system may further comprise a comparator (not shown). In a calibration mode, the comparator may be configured to compare the fluid flow measured in the fluid transport conduit 80 with the fluid flow supplied by the flow controller 71. In particular, the comparator may be configured to compare the flow measured by the flow meter 81 with the flow supplied by the flow controller 71.

[0088] As described above, in calibration mode, a known relationship may exist between the flow provided by the flow controller 71 and the flow through the fluid transport conduit 80. Thus, for a given flow provided by the flow controller 71, the flow through the fluid transport conduit 80 may be predetermined. The predetermined flow through the fluid transport conduit 80 based on the known relationship may be compared to the flow through the fluid transport conduit 80 measured by the flow meter 81. If the predetermined flow through the fluid transport conduit 80 and the flow measured by the flow meter 81 match within a predetermined range, the flow meter 81 may be considered calibrated. In other words, it may be determined that the flow meter 81 is providing a sufficiently accurate measurement of the flow through the fluid transport conduit 80.

[0089] The fluid handling system optionally further comprises a meter calibration unit (not shown) configured to adjust the flow meter 81 based on the comparison. For example, if the comparison determines that the measurement of the flow meter 81 is lower than expected, the flow meter 81 may be adjusted to provide the expected measurement. Alternatively, or additionally, the fluid handling system may be configured to send a warning if the comparison indicates that the predetermined flow through the fluid transport conduit 80 and the flow measured by the flow meter 81 do not match within a predetermined range. In other words, the fluid handling system may be configured to warn a user if the flow meter 81 is not providing a sufficiently accurate measurement of the flow through the fluid transport conduit 80. The user may then take action to adjust or replace the flow meter 81 as necessary.

[0090] The bypass conduit 90 may be configured such that, in the calibration mode, both the gas supply conduit 70 and the fluid transport conduit 80 operate at a pressure similar to the pressures in the gas supply conduit 70 and the fluid transport conduit 80 in the production mode, i.e., within a particular threshold range. The bypass conduit 90 is desirably configured such that, in the calibration mode, the pressures at the flow controller 71 and the flow meter 81 are similar to the pressures at the flow controller 71 and the flow meter 81 in the production mode, i.e., within a particular threshold range. The bypass conduit 90 optionally includes a flow restriction 94, as shown, for example, in FIG. 3 . The flow restriction 94 may be configured to achieve a desired pressure level in the fluid transport conduit 80 and / or the gas supply conduit 70 in the calibration mode.

[0091] The fluid handling system may include a bypass conduit 90. Alternatively, all or part of the bypass conduit 90 may be removable from the system. In a calibration mode, the bypass conduit 90 is attached to the system, and in a production mode, the bypass conduit 90 is removed from the system. For example, the bypass conduit 90 may be configured to be disconnected from the gas supply conduit 70 and the fluid transport conduit 80, placing the system in a production mode. To place the fluid handling system in a calibration mode, the bypass conduit 90 may be attached to the system. In other words, to place the fluid handling system in a calibration mode, the bypass conduit 90 may be connected to the gas supply conduit 70 and the fluid transport conduit 80. This configuration allows the same bypass conduit 90 to be shared among multiple fluid handling systems by removing the bypass conduit 90 from a calibrated system and connecting it to another system that may require calibration. This is possible because the bypass conduit 90 is not used when the system is in a production mode. This is beneficial in terms of efficient use of the bypass conduit 90 components, which may result in cost savings.

[0092] The fluid handling system may further comprise a plurality of valves, for example as shown in Figure 3. The plurality of valves may be configured to change the system between a production mode and a calibration mode. Alternatively or additionally, in an arrangement in which the bypass conduit 90 is removable, the plurality of valves may be configured to change the system between a production mode in which the bypass conduit 90 may be removed without interrupting the flow of fluid from the gas supply conduit 70 to the immersion space 11 and through the fluid transport conduit 80 from the immersion space 11, and a calibration mode.

[0093] In the exemplary configuration shown in FIG. 3, the plurality of valves includes a gas supply valve 72, a bypass valve 92, and a fluid extraction valve 82.

[0094] The gas supply valve 72 is arranged in the gas supply conduit 70. The gas supply valve 72 is preferably arranged downstream of the flow controller 71 in the direction of fluid flow. In other words, the gas supply valve 72 may be configured to allow, restrict, and / or prevent a flow from the gas supply conduit 70 to the immersion space 11. In particular, the gas supply valve 72 may be configured to allow, restrict, and / or prevent a flow of fluid supplied by the flow controller 71 to the immersion space 11. In the production mode, the gas supply valve 72 is open and allows a flow of fluid from the gas supply conduit 70 to the immersion space 11. In the calibration mode, the gas supply valve 72 is closed and prevents a flow of fluid from the gas supply conduit 70 to the immersion space 11.

[0095] The bypass valve 92 is disposed within the bypass conduit 90. In other words, the bypass valve 92 may be configured to allow, restrict, and / or prevent flow through the bypass conduit 90. In a production mode, the bypass valve 92 is closed, preventing fluid flow from the gas supply conduit 70 to the fluid transport conduit 80 via the bypass conduit 90. In a calibration mode, the bypass valve 92 is open, allowing fluid flow from the gas supply conduit 70 to the fluid transport conduit 80 via the bypass conduit 90.

[0096] The fluid extraction valve 82 may be arranged in the fluid transport conduit 80 or at the inlet of the fluid transport conduit 80. The fluid extraction valve 82 is preferably arranged upstream of the flow meter 81. In other words, the fluid extraction valve 82 may be configured to allow, restrict, and / or prevent a flow from the immersion space 11 to the fluid transport conduit 80. In particular, the fluid extraction valve 82 may be configured to allow, restrict, and / or prevent a flow from the immersion space 11 to the flow meter 81. In a production mode, the fluid extraction valve 82 is open and allows a flow of fluid from the immersion space 11 to the fluid transport conduit 80. In a calibration mode, the fluid extraction valve 82 is closed and prevents a flow of fluid from the immersion space 11 to the fluid transport conduit 80.

[0097] 3 , the fluid handling system may comprise a fluid extraction conduit 84 in fluid communication with the liquid confinement structure 12 and configured to extract fluid from the immersion space 11 and direct the extracted fluid to the fluid transport conduit 80. The fluid extraction valve 82 may be arranged between the fluid extraction conduit 84 and the fluid transport conduit 80. In other words, the fluid extraction valve 82 may be configured to allow, restrict and / or prevent flow from the fluid extraction conduit 84 to the fluid transport conduit 80. In particular, the fluid extraction valve 82 may be configured to allow, restrict and / or prevent flow from the fluid extraction conduit 84 to the flow meter 81. In a production mode, the fluid extraction valve 82 is open and allows fluid flow from the fluid extraction conduit 84 to the fluid transport conduit 80. In a calibration mode, the fluid extraction valve 82 is closed and prevents flow from the fluid extraction conduit 84 to the fluid transport conduit 80.

[0098] At least in the production mode, immersion liquid is also supplied to the immersion space 11 from liquid supply openings such as 20, 23, 34 in Figures 2a-2d, and a fluid extraction conduit 84 extracts a two-phase fluid, i.e. a mixture of a gas, such as CO2, and a liquid, such as water. The liquid supply and extraction circuits are not shown in Figure 3. In such a configuration, the two-phase fluid may be separated before reaching the flow meter 81, with only a single phase (e.g., gas) being measured by the flow meter 81. In particular, the separated fluid phase (e.g., liquid) may be directed via a branch or outlet (not shown) between the immersion space 11 and the flow meter 81. Optionally, the separated fluid phase may be conducted through a branch or outlet located at a position between the fluid extraction conduit 84 and the flow meter 81, preferably between the fluid extraction conduit 84 and the bypass conduit 90 or the position where a first branch 93 of the bypass conduit 90 is connected to the fluid transport conduit 80, more preferably between the fluid extraction conduit 84 and the fluid extraction valve 82, i.e., located at the aforementioned position or upstream of the fluid extraction valve 82. Similarly for the additional fluid transport conduit 85, a single phase of the two-phase fluid may be extracted before the fluid reaches the additional flow meter 86. The separated fluid phase (e.g., liquid) may be conducted through a branch or outlet (not shown) between the immersion space 11 and the additional flow meter 86. Optionally, the separated fluid phases may be conducted through a branch or outlet located at a position between the fluid extraction conduit 84 and the additional flow meter 86, preferably between the fluid extraction conduit 84 and the additional bypass conduit 95 or a position where a second branch 98 of the bypass conduit is connected to the additional fluid transport conduit 85, more preferably between the fluid extraction conduit 84 and the additional fluid extraction valve 87, i.e., located at the above-mentioned position or upstream of the additional fluid extraction valve 87.

[0099] In an alternative arrangement (not shown in Figure 3), the fluid handling system may comprise a plurality of fluid extraction conduits 84 in fluid communication with the liquid confinement structure 12 and configured to extract fluid from the immersion space 11 and direct the extracted fluid to the fluid transport conduit 80. The multiple fluid extraction conduits 84 optionally join downstream of the immersion space 11 to form the fluid transport conduit 80. In this arrangement, there may be a single fluid extraction valve 82 located at the inlet of the fluid transport conduit 80 upstream of the flow meter 81 or at some point along the fluid transport conduit 80. Alternatively, there may be two fluid extraction valves 82 located at some point along the fluid extraction conduit 84.

[0100] 4 and 5 , the fluid handling system optionally further comprises an additional fluid transport conduit 85 in fluid communication with the fluid handling structure or liquid confinement structure 12 and configured to transport fluid extracted from the immersion space 11. The additional fluid transport conduit 85 is provided with an additional flow meter 86 configured to measure the flow of fluid in the additional fluid transport conduit 85. In particular, the fluid in the additional fluid transport conduit 85 may be a fluid supplied to the immersion space 11 via the gas supply conduit 70.

[0101] Each of the fluid transport conduit 80 and the additional fluid transport conduit 85 may be configured to transport fluid from the immersion space 11. As shown in Figures 4 and 5, the fluid handling system may comprise fluid extraction conduits 84. The first fluid extraction conduit 84 is in fluid communication with the liquid confinement structure 12 and is configured to extract fluid from the immersion space 11 and to direct the extracted fluid to the fluid transport conduit 80. The second fluid extraction conduit 84 is in fluid communication with the liquid confinement structure 12 and is configured to extract fluid from the immersion space 11 and to direct the extracted fluid to the additional fluid transport conduit 85. In an alternative arrangement (not shown), each of the fluid transport conduit 80 and the additional fluid transport conduit 85 may be configured to extract fluid directly from the immersion space 11.

[0102] 4 shows an exemplary fluid handling system comprising a gas supply conduit 70, a plurality of fluid transport conduits 80, 85 and a corresponding plurality of bypass conduits 90, 95. Each bypass conduit 90, 95 is configured such that in a calibration mode, the gas supply conduit 70 is in direct fluid communication with one of the plurality of fluid transport conduits 80, 85 via the corresponding bypass conduit 90, 95.

[0103] Unless otherwise stated, components in Figure 4 having corresponding reference numerals perform the same functions as described above for Figure 3. As with the arrangement of Figure 3 described above, in the arrangement of Figure 4, in calibration mode the gas supply conduit 70 is in direct fluid communication with the fluid transport conduit 80 via a bypass conduit 90, which bypasses the liquid confinement structure 12 and an additional bypass conduit 95. Fluid supplied by the flow controller 71 flows directly into the fluid transport conduit 80 via the bypass conduit 90.

[0104] In the configuration of Figure 4, in the additional calibration mode, the gas supply conduit 70 is in direct fluid communication with the additional fluid transport conduit 85 via the additional bypass conduit 95, which bypasses the liquid confinement structure 12 and the bypass conduit 90. Gas supplied by the flow controller 71 flows directly into the additional fluid transport conduit 85 via the additional bypass conduit 95.

[0105] The fluid handling system may further comprise a plurality of valves, for example as shown in Figure 4. Similar to the exemplary arrangement shown in Figure 3, the plurality of valves in Figure 4 comprises a gas supply valve 72, a bypass valve 92 and a fluid extraction valve 82, each configured as described above in relation to Figure 3. The plurality of valves in Figure 4 further comprises an additional bypass valve 97 and an additional fluid extraction valve 87.

[0106] The additional bypass valve 97 is disposed within the additional bypass conduit 95. In other words, the additional bypass valve 97 may be configured to allow, restrict, and / or prevent flow through the additional bypass conduit 95. In the production mode, the bypass valve 97 is closed, preventing fluid flow from the gas supply conduit 70 to the additional fluid transport conduit 85 via the additional bypass conduit 95. In the calibration mode, the additional bypass valve 97 is closed, preventing fluid flow from the gas supply conduit 70 to the additional fluid transport conduit 85 via the additional bypass conduit 95. In the additional calibration mode, the bypass valve 92 is closed, preventing fluid flow from the gas supply conduit 70 to the fluid transport conduit 80 via the bypass conduit 90. In the additional calibration mode, the additional bypass valve 97 is open, allowing fluid flow from the gas supply conduit 70 to the additional fluid transport conduit 85 via the additional bypass conduit 95.

[0107] The additional fluid extraction valve 87 may be arranged in the additional fluid transport conduit 85 or at the inlet of the additional fluid transport conduit 85. The additional fluid extraction valve 87 is desirably arranged upstream of the additional flow meter 86. In other words, the additional fluid extraction valve 87 may be configured to allow, restrict, and / or prevent a flow from the immersion space 11 to the additional fluid transport conduit 85. In particular, the additional fluid extraction valve 87 may be configured to allow, restrict, and / or prevent a flow from the immersion space 11 to the additional flow meter 86. In the production mode, the additional fluid extraction valve 87 is opened to allow a flow of fluid from the immersion space 11 to the additional fluid transport conduit 85. In the additional calibration mode, the additional fluid extraction valve 87 is closed to prevent a flow of fluid from the immersion space 11 to the additional fluid transport conduit 85. In the additional calibration mode, the fluid extraction valve 87 is closed to prevent a flow of fluid from the immersion space 11 to the additional fluid transport conduit 85.

[0108] As shown in the exemplary configuration of Figure 5, the fluid handling system may comprise an additional fluid extraction conduit 84 in fluid communication with the liquid confinement structure 12 and configured to extract fluid from the space 11 and direct the extracted fluid to the additional fluid transport conduit 85. The additional fluid extraction valve 87 may be arranged between the fluid extraction conduit 84 and the additional fluid transport conduit 85. In other words, the additional fluid extraction valve 87 may be configured to allow, restrict and / or prevent flow from the fluid extraction conduit 84 to the additional fluid transport conduit 85. In particular, the additional fluid extraction valve 87 may be configured to allow, restrict and / or prevent flow from the fluid extraction conduit 84 to the additional flow meter 86. In a production mode, the additional fluid extraction valve 87 is open and allows fluid flow from the fluid extraction conduit 84 to the additional fluid transport conduit 85. In a calibration mode, the additional fluid extraction valve 87 is closed and prevents fluid flow from the fluid extraction conduit 84 to the additional fluid transport conduit 85. In the additional calibration mode, the additional fluid extraction valve 87 is closed, preventing fluid flow from the fluid extraction conduit 84 to the additional fluid transport conduit 85. In the additional calibration mode, the fluid extraction valve 82 is closed, preventing fluid flow from the fluid extraction conduit 84 to the fluid transport conduit 80.

[0109] Figure 5 shows a preferred configuration in which the fluid handling system comprises a gas supply conduit 70, a plurality of fluid transport conduits 80, 85 and a bypass conduit 90. In the configuration of Figure 5, the bypass conduit 90 is configured such that in a calibration mode, the gas supply conduit 70 is in direct fluid communication with one of the plurality of fluid transport conduits 80, 85 via the bypass conduit 90. The bypass conduit 90 may comprise a first branch 93 configured to provide fluid communication between the gas supply conduit 70 and the fluid transport conduit 80. The bypass conduit 90 may comprise a second branch 98 configured to provide fluid communication between the gas supply conduit 70 and the additional fluid transport conduit 85.

[0110] In the calibration mode, the gas supply conduit 70 is in direct fluid communication with the fluid transport conduit 80 via a first branch 93 of the bypass conduit 90, which bypasses the fluid handling structure or liquid confinement structure 12 and a second branch 98 of the bypass conduit 90. Fluid supplied by the flow controller 71 flows directly into the fluid transport conduit 80 via the bypass conduit 90.

[0111] In the configuration of Figure 5, in the additional calibration mode, the gas supply conduit 70 is in direct fluid communication with the additional fluid transport conduit 85 via a second branch 98 of the bypass conduit 90, which bypasses the liquid confinement structure 12 and the first branch 93 of the bypass conduit 90. Fluid supplied by the flow controller 71 flows directly to the additional fluid transport conduit 85 via the bypass conduit 90.

[0112] The fluid handling system may further comprise a plurality of valves, as shown, for example, in Figure 5. Similar to the exemplary configuration shown in Figure 4, the plurality of valves in Figure 5 comprises gas supply valve 72, bypass valve 92, fluid extraction valve 82 and additional fluid extraction valve 87, each configured as described above for Figure 4. The plurality of valves in Figure 5 further comprises a second branch bypass valve 99. In the configuration of Figure 5, bypass valve 92 is located in a first branch 93 of bypass circuit 90. In other words, bypass valve 92 may be configured to allow, restrict and / or prevent flow through first branch 93 of bypass conduit 90.

[0113] The second branch bypass valve 99 is disposed within the second branch 98 of the bypass conduit 90. In other words, the second branch bypass valve 99 may be configured to allow, restrict, and / or prevent flow through the second branch 98 of the bypass conduit 90. In the production mode, the second branch bypass valve 99 is closed, preventing fluid flow from the gas supply conduit 70 to the additional fluid transport conduit 85 via the second branch 98 of the bypass conduit 90. In the calibration mode, the second branch bypass valve 99 is closed, preventing fluid flow from the gas supply conduit 70 to the additional fluid transport conduit 85 via the second branch 98 of the bypass conduit 90. In the additional calibration mode, the bypass valve 92 is closed, preventing fluid flow from the gas supply conduit 70 to the fluid transport conduit 80 via the bypass conduit 90. In the additional calibration mode, the second branch bypass valve 99 is open, allowing fluid flow from the gas supply conduit 70 to the additional fluid transport conduit 85 via the second branch 98 of the bypass conduit 90.

[0114] The fluid handling system may further comprise a comparator (not shown). In an additional calibration mode, the comparator may be configured to compare the fluid flow measured in the additional fluid transport conduit 85 with the fluid flow supplied by the flow controller 71. In particular, the comparator may be configured to compare the flow measured by the additional flow meter 86 with the flow supplied by the flow controller 71.

[0115] The fluid handling system optionally further comprises a meter calibration unit (not shown) configured to adjust the additional flow meter 86 based on the comparison. For example, if the comparison determines that the measurement of the additional flow meter 86 is lower than expected, the additional flow meter 86 may be adjusted to provide the expected measurement. Alternatively or additionally, the fluid handling system may be configured to send a warning if the comparison indicates that a predetermined flow through the additional fluid transport conduit 85 based on the flow rate provided by the flow controller 71 in the additional calibration mode and the flow measured by the additional flow meter 86 do not match within a predetermined range. In other words, the fluid handling system may be configured to warn a user if the additional flow meter 86 is not providing a sufficiently accurate measurement of the flow through the additional fluid transport conduit 85. The user may then take steps to adjust or replace the additional flow meter 86 as necessary.

[0116] The fluid handling system optionally comprises a pressure sensor 73. The pressure sensor 73 may be located downstream of the flow controller 71, for example as shown in Figures 3, 4 and 5. The pressure sensor 73 is configured to measure the pressure of the fluid. The pressure sensor 73 is preferably located in the gas supply conduit 70, as shown in Figure 3. The pressure sensor 73 desirably enables the relationship between pressure and flow rate in the gas supply conduit 70 to be determined for purposes of calibrating the flow controller 71. In this manner, the pressure sensor 73 may be used to calibrate the flow controller 71. The flow controller 71 may be used to calibrate the flow meter 81, for example by setting the fluid handling system in a calibration mode as described above.

[0117] The fluid handling system optionally further comprises a supply calibration unit (not shown) configured to adjust the flow controller 71 based on a comparison between the pressure measured by the pressure sensor 73 and the flow rate set by the flow controller 71. In other words, the supply calibration unit may be configured to automatically adjust the flow controller 71 if the pressure measured by the pressure sensor 73 is not within an acceptable range of expected pressure based on the flow rate set by the flow controller 71, to indicate that the flow controller 71 is out of calibration. The supply calibration unit may therefore be used to automatically calibrate the flow controller 71. Alternatively or additionally, the fluid handling system may comprise a warning unit configured to warn a user if the pressure measured by the pressure sensor 73 is not within an acceptable range of expected pressure based on the flow rate set by the flow controller 71. In this way, the user can manually take steps to adjust or replace the flow controller 71 if necessary.

[0118] Although the configurations shown in Figures 4 and 5 each include only one additional fluid transport conduit 85, the configurations may be modified to include two or more additional fluid transport conduits.

[0119] The present invention may also provide a lithographic apparatus, which may have any or all of the other features or components of the lithographic apparatus described above, for example, the lithographic apparatus may optionally include at least one of a source SO, an illumination system IL, a projection system PS, a substrate support WT, etc.

[0120] In particular, the lithographic apparatus may include a projection system PS configured to project a radiation beam B towards a region of a surface of a substrate W.

[0121] It should be noted that although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, the lithographic apparatus described herein may have other applications, including the manufacture of integrated optical systems, induction and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0122] Where the context allows, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Also, embodiments of the present invention may be implemented as 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, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.), and the like. Furthermore, firmware, software, routines, and instructions may be described herein as performing certain actions. However, it should be understood that such description is merely for convenience, and that such actions actually occur when a computing device, processor, controller, or other device executes the firmware, software, routines, instructions, etc., which may cause actuators or other devices to interact with the physical world.

[0123] Although embodiments of the invention are specifically referred to herein in the context of lithography apparatus, embodiments of the invention may also be applied to other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatus may be generally referred to as lithography tools. Such lithography tools may use atmospheric (non-vacuum) conditions.

[0124] 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 understood that, where the context permits, the invention is not limited to optical lithography.

[0125] Embodiments include the following numbered clauses: (Item 1) a liquid confinement structure configured to confine immersion fluid in a space between at least part of the liquid confinement structure and a surface of a substrate; a gas supply conduit in fluid communication with the liquid confinement structure and configured to supply a fluid to the space, the gas supply conduit having a flow controller configured to control the supply of gas from the gas supply conduit; a fluid transport conduit in fluid communication with the liquid confinement structure and configured to transport fluid extracted from the space, the fluid transport conduit having a flow meter configured to measure a flow of gas in the fluid transport conduit; In calibration mode, the gas supply conduit is in direct fluid communication with the fluid transport conduit via a bypass conduit, the bypass conduit bypassing the liquid confinement structure; the gas supplied by the flow controller flows directly into the fluid transport conduit via the bypass conduit; Fluid handling systems. (Item 2) The system described in Item 1, further comprising a comparator, the comparator being configured to compare the gas flow measured in the fluid transport conduit with the gas flow supplied by the flow controller in the calibration mode. (Item 3) The system described in Item 2, further comprising a meter calibration unit configured to adjust the flow meter based on the comparison. (Item 4) A system described in any of the above items, wherein all or part of the bypass conduit is removable from the system, and in the calibration mode, the bypass conduit is attached to the system. (Item 5) A system described in any of the above items, wherein in production mode, gas supplied by the flow controller flows through the liquid confinement structure into a fluid transport conduit, and the flow meter is configured to measure the flow of extracted gas. (Item 6) The system described in Item 5, wherein all or part of the bypass conduit is removable from the system, and in the calibration mode, the bypass conduit is attached to the system, and in the manufacturing mode, the bypass conduit is removed from the system. (Item 7) The system described in Item 5 or Item 6, further comprising a plurality of valves configured to change the system between the manufacturing mode and the calibration mode. (Item 8) The plurality of valves includes a gas supply valve disposed in the gas supply conduit downstream of the flow controller; In the production mode, the gas supply valve is open to allow gas to flow from the gas supply conduit to the space; Item 8. The system of item 7, wherein in the calibration mode, the gas supply valve is closed to prevent gas flow from the gas supply conduit to the space. (Item 9) The plurality of valves includes a bypass valve disposed in the bypass conduit; In the production mode, the bypass valve is closed to prevent gas from flowing from the gas supply conduit to the fluid transport conduit through the bypass conduit; Item 9. The system of claim 7 or 8, wherein in the calibration mode, the bypass valve is opened to allow gas to flow from the gas supply conduit to the fluid transport conduit via the bypass conduit. (Item 10) The plurality of valves includes a fluid extraction valve disposed in the fluid transport conduit upstream of the flow meter; In the production mode, the fluid extraction valve is open to allow gas flow from the space to the fluid transport conduit; 10. The system of any of claims 7 to 9, wherein in the calibration mode, the fluid extraction valve is closed, preventing gas flow from the space to the fluid transport conduit. (Item 11) A system described in any of the above items, further comprising a plurality of fluid extraction conduits fluidly connected to the liquid confinement structure and configured to extract fluid from the space and direct the extracted fluid to the fluid transport conduit. (Item 12) The system described in Item 11, wherein the multiple fluid extraction conduits converge downstream of the space to form the fluid transport conduit. (Item 13) A system described in any of items 1 to 10, further comprising an additional fluid transport conduit in fluid communication with the liquid confinement structure and configured to transport fluid extracted from the space, the additional fluid transport conduit having an additional flow meter configured to measure the flow of gas in the additional fluid transport conduit. (Item 14) The system described in Item 13, wherein each of the fluid transport conduit and the additional fluid transport conduit is configured to extract fluid from the space. (Item 15) In additional calibration mode, the gas supply conduit is in direct fluid communication with the further fluid transport conduit via the bypass conduit, the bypass conduit bypassing the liquid confinement structure; Item 15. The system of item 13 or 14, wherein the gas supplied by the flow controller flows directly into the additional fluid transport conduit via the bypass conduit. (Item 16) In additional calibration mode, the gas supply conduit is in direct fluid communication with the additional fluid transport conduit via an additional bypass conduit, the additional bypass conduit bypassing the liquid confinement structure and the bypass conduit; Item 15. The system of item 13 or 14, wherein the gas supplied by the flow controller flows directly into the additional fluid transport conduit via the additional bypass conduit. (Item 17) The system described in Item 15 or Item 16, further comprising a comparator, wherein in the additional calibration mode, the comparator is configured to compare the gas flow measured in the additional fluid transport conduit with the gas flow supplied by the flow controller. (Item 18) A system described in any of the above items, further comprising a pressure sensor positioned downstream of the flow controller, the pressure sensor configured to measure the pressure of the gas in the gas supply conduit. (Item 19) The system described in Item 18, further comprising a supply calibration unit configured to adjust the flow controller based on a comparison between the pressure measured by the pressure sensor and the flow rate set by the flow controller. (Item 20) A system described in any of the above items, wherein the bypass conduit is provided with a flow restriction portion. (Item 21) A method of calibrating a flow meter in a fluid handling system, comprising: The fluid handling system comprises: a liquid confinement structure configured to confine immersion fluid in a space between at least part of the liquid confinement structure and a surface of the substrate; a gas supply conduit in fluid communication with the liquid confinement structure and configured to supply a fluid to the space, the gas supply conduit having a flow controller configured to control the supply of gas from the gas supply conduit; a fluid transport conduit in fluid communication with the liquid confinement structure and configured to transport fluid extracted from the space, the fluid transport conduit having a flow meter configured to measure a flow of gas in the fluid transport conduit; The method comprises: setting the system in a calibration mode, wherein the gas supply conduit is in direct fluid communication with the fluid transport conduit via a bypass conduit, the bypass conduit bypassing the liquid confinement structure, and wherein gas supplied by the flow controller flows directly into the fluid transport conduit via the bypass conduit; comparing the gas flow measured in the fluid transport conduit to the gas flow supplied by the flow controller.

[0126] While specific embodiments of the present invention have been described above, it will be understood that the invention may be practiced otherwise than as described. The foregoing description is intended to be illustrative and not limiting. Thus, it will be apparent to those skilled in the art that changes may be made to the invention as described without departing from the scope of the claims that follow.

Claims

1. a liquid confinement structure configured to confine immersion fluid in a space between at least part of the liquid confinement structure and a surface of the substrate; a gas supply conduit in fluid communication with the liquid confinement structure and configured to supply a fluid to the space, the gas supply conduit having a flow controller configured to control the supply of gas from the gas supply conduit; a fluid transport conduit in fluid communication with the liquid confinement structure and configured to transport fluid extracted from the space, the fluid transport conduit having a flow meter configured to measure a flow of gas in the fluid transport conduit; In calibration mode, the gas supply conduit is in direct fluid communication with the fluid transport conduit via a bypass conduit, the bypass conduit bypassing the liquid confinement structure; the gas supplied by the flow controller flows directly into the fluid transport conduit via the bypass conduit; Fluid handling systems.

2. and a comparator configured to compare, in the calibration mode, the flow of gas measured in the fluid transport conduit with the flow of gas supplied by the flow controller. The system of claim 1 .

3. and a meter calibration unit configured to adjust the flow meter based on the comparison. The system of claim 2 .

4. all or part of the bypass conduit is removable from the system, and in the calibration mode the bypass conduit is attached to the system; and / or in a production mode gas supplied by the flow controller flows through the liquid confinement structure into a fluid transport conduit and the flow meter is configured to measure the flow of extracted gas. A system according to any one of claims 1 to 3.

5. all or a portion of the bypass conduit is removable from the system, and in the calibration mode, the bypass conduit is attached to the system, and in the production mode, the bypass conduit is removed from the system; The system of claim 4.

6. further comprising a plurality of valves configured to alter the system between the manufacturing mode and the calibration mode. The system of claim 4.

7. the plurality of valves comprises a gas supply valve disposed in the gas supply conduit downstream of the flow controller; In the production mode, the gas supply valve is open to allow gas to flow from the gas supply conduit to the space; In the calibration mode, the gas supply valve is closed, preventing gas flow from the gas supply conduit to the space; and / or the plurality of valves comprises a bypass valve disposed in the bypass conduit; In the production mode, the bypass valve is closed to prevent gas from flowing from the gas supply conduit to the fluid transport conduit through the bypass conduit; In the calibration mode, the bypass valve is opened to allow gas flow from the gas supply conduit to the fluid transport conduit via the bypass conduit; and / or the plurality of valves comprising a fluid extraction valve disposed in the fluid transport conduit upstream of the flow meter; In the production mode, the fluid extraction valve is open to allow gas flow from the space to the fluid transport conduit; In the calibration mode, the fluid extraction valve is closed to prevent gas flow from the space to the fluid transport conduit. The system of claim 6.

8. further comprising a plurality of fluid extraction conduits in fluid communication with the liquid confinement structure and configured to extract fluid from the space and direct the extracted fluid to the fluid transport conduit; or further comprising an additional fluid transport conduit in fluid communication with the liquid confinement structure and configured to transport fluid extracted from the space, the additional fluid transport conduit having an additional flow meter configured to measure gas flow in the additional fluid transport conduit; A system according to any one of claims 1 to 7.

9. the plurality of fluid extraction conduits meet downstream of the space to form the fluid transport conduit, or the fluid transport conduit and each of the additional fluid transport conduits are configured to extract fluid from the space; The system of claim 8.

10. In an additional calibration mode, the gas supply conduit is in direct fluid communication with the further fluid transport conduit via the bypass conduit, the bypass conduit bypassing the liquid confinement structure; the gas supplied by the flow controller flows directly through the bypass conduit to the additional fluid transport conduit; or In an additional calibration mode, the gas supply conduit is in direct fluid communication with the additional fluid transport conduit via an additional bypass conduit, the additional bypass conduit bypassing the liquid confinement structure and the bypass conduit; the gas supplied by the flow controller flows directly into the additional fluid transport conduit via the additional bypass conduit; 10. The system according to claim 8 or 9.

11. a comparator configured to, in the additional calibration mode, compare the gas flow measured in the additional fluid transport conduit with the gas flow supplied by the flow controller; The system of claim 10.

12. a pressure sensor disposed downstream of the flow controller, the pressure sensor configured to measure a pressure of the gas in the gas supply conduit.

12. A system according to any one of claims 1 to 11.

13. a supply calibration unit configured to adjust the flow controller based on a comparison of the pressure measured by the pressure sensor and a flow rate set by the flow controller; The system of claim 12.

14. the bypass conduit includes a flow restriction.

14. A system according to any one of claims 1 to 13.

15. 1. A method of calibrating a flow meter in a fluid handling system, comprising the steps of: The fluid handling system comprises: a liquid confinement structure configured to confine immersion fluid in a space between at least part of the liquid confinement structure and a surface of the substrate; a gas supply conduit in fluid communication with the liquid confinement structure and configured to supply a fluid to the space, the gas supply conduit having a flow controller configured to control the supply of gas from the gas supply conduit; a fluid transport conduit in fluid communication with the liquid confinement structure and configured to transport fluid extracted from the space, the fluid transport conduit having a flow meter configured to measure a flow of gas in the fluid transport conduit; The method comprises: setting the system in a calibration mode, wherein the gas supply conduit is in direct fluid communication with the fluid transport conduit via a bypass conduit, the bypass conduit bypassing the liquid confinement structure, and wherein gas supplied by the flow controller flows directly into the fluid transport conduit via the bypass conduit; comparing the gas flow measured in the fluid transport conduit with the gas flow supplied by the flow controller. method.

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