Fluid handling system, method and lithographic apparatus

Abstract

A fluid handling system for a lithographic apparatus is disclosed. The fluid handling system is configured to confine immersion liquid to a liquid confinement space between a part of a projection system in the lithographic apparatus and a surface of a substrate such that a radiation beam projected from the projection system can pass through the immersion liquid to illuminate the surface of the substrate. The fluid handling system comprises a damper provided between first and second outlets, both configured to extract fluid. The damper is configured to support a meniscus of immersion liquid between a surface of the damper and the surface of the substrate.

Description

[Technical Field]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims priority to European Application No. 20209779.6, filed November 25, 2020, which is incorporated herein by reference in its entirety.

[0002] [Technical field] The present invention relates to a fluid handling system and a device manufacturing method.The present invention also relates to a lithographic apparatus. [Background technology]

[0003] A lithographic apparatus is a machine configured to apply a desired pattern onto a substrate. Lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern (often referred to as 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 in one go, and so-called scanners, in which each target portion is irradiated by scanning the pattern through a radiation beam in a predetermined direction (the "scan" direction) while simultaneously scanning the substrate parallel or non-parallel to this direction.

[0004] As semiconductor manufacturing processes continue to improve, the dimensions of circuit elements are continually decreasing while the amount of functional elements, such as transistors, per device has steadily increased over the past few decades, following a trend commonly referred to as "Moore's Law." The semiconductor industry pursues technologies that enable the creation of smaller and smaller features to keep up with Moore's Law. To project a pattern onto a substrate, a lithography apparatus 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 improvements in resolution of smaller features may be realized by providing an immersion fluid, such as water, having a relatively high refractive index onto the substrate during exposure. The effect of the immersion fluid is that the exposure radiation in the fluid has a shorter wavelength than in a gas, allowing for imaging of smaller features. The effect of the immersion fluid is also to increase the effective numerical aperture (NA) of the system, which also increases the depth of focus. Summary of the Invention [Problem to be solved by the invention]

[0006] The immersion fluid may be confined to a localized area between the projection system of the lithographic apparatus and the substrate by a fluid handling structure. The use of such an immersion fluid can lead to the presence of droplets on the surface of the substrate. Such droplets can be problematic because they can result in dry spots on the substrate and, when the droplets hit the immersion liquid meniscus, can lead to the formation of bubbles due to gas trapped in the immersion liquid. Bubbles in the immersion liquid can lead to defects being printed on the substrate. The likelihood of introducing such bubbles can be reduced by reducing the relative velocity of the substrate, but this limits the throughput of the lithographic apparatus.

[0007] It is an object of the present invention to provide a fluid handling system and method in which measures are taken to increase throughput and / or reduce defects on substrates. [Means for solving the problem]

[0008] According to a first aspect of the present invention, there is provided a fluid handling system for a lithographic apparatus, the fluid handling system configured to confine immersion liquid to a liquid confinement space between a part of a projection system of the lithographic apparatus and a surface of a substrate such that a radiation beam projected from the projection system can pass through the immersion liquid to illuminate the surface of the substrate, the fluid handling system comprising a damper provided between first and second outlets configured to both extract fluid, the damper configured to support a meniscus of immersion liquid between a surface of the damper and the surface of the substrate.

[0009] According to a second aspect of the invention, there is provided a lithographic apparatus comprising the fluid handling system of the first aspect.

[0010] According to a third aspect of the invention, there is provided a device manufacturing method in a lithographic apparatus having a substrate holder configured to hold a substrate, a projection system configured to project a beam of radiation onto the substrate held by the substrate holder, and a fluid handling system according to the first aspect, the method comprising using the fluid handling system to confine immersion liquid to a space between at least part of the fluid handling system and a surface of the substrate, projecting a patterned beam of radiation through the immersion liquid in the space onto the substrate, supporting a meniscus of the immersion liquid between a surface of a damper and the substrate, and driving the substrate in a scan direction substantially perpendicular to a direction of propagation of the radiation beam such that the meniscus moves along the surface of the damper in response to movement of the substrate.

[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 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] FIG. 1 depicts a schematic overview of a lithographic apparatus.

[0014] Figures 2a, 2b, 2c and 2d each show in cross section two different versions of a fluid handling system, which may extend all around, with different features illustrated on the left and right sides of each version.

[0015] Figures 3a and 3b show a fluid handling system according to a first embodiment in first and second operational states respectively.

[0016] Figure 4 depicts a fluid handling system according to a second embodiment.

[0017] Figure 5 depicts a fluid handling system according to a third embodiment.

[0018] FIG. 6 depicts a fluid handling system according to a fourth embodiment.

[0019] The features shown in the figures are not necessarily to scale and are not limited to the size and / or arrangement shown. The figures are understood to include optional features that are not essential to the invention. Furthermore, not all features of a device are shown in each figure, and a figure may show only some of the components relevant to describing a particular feature. DETAILED DESCRIPTION OF THE INVENTION

[0020] In this document, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (eg, having wavelengths of 365, 248, 193, 157 or 126 nm).

[0021] The terms "reticle," "mask," or "patterning device," as used in this text, may be broadly interpreted to refer to a general patterning device that may 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. Besides 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.

[0022] Figure 1 schematically illustrates a lithographic apparatus. The lithographic apparatus includes an illumination system (also referred to as an illuminator) IL configured to condition a radiation beam B (e.g., UV or DUV radiation), a mask support (e.g., mask table) MT configured to support a patterning device (e.g., mask) MA and connected to a first positioner PM configured to accurately position the patterning device MA according to certain parameters, a substrate support (e.g., substrate table) WT configured to hold a substrate (e.g., a resist-coated wafer) W and connected to a second positioner PW configured to accurately position the substrate support WT according to certain parameters, and a projection system (e.g., a refractive projection lens system) PS configured to project a pattern formed in the radiation beam B by the patterning device MA onto a target portion C (e.g., comprising one or more dies) of the substrate W. A controller 500 controls the overall operation of the apparatus. The controller 500 may be a central control system or a system of multiple separate sub-controllers within various subsystems of the lithographic apparatus.

[0023] In operation, the illumination system IL receives a 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, or any combination thereof, such as refractive, reflective, magnetic, electromagnetic, electrostatic and / or other types of optical components, for directing, shaping and / or controlling the radiation. The illuminator IL may be used to condition the radiation beam B so that it has a desired spatial and angular intensity distribution in its cross-section at the plane of the patterning device MA.

[0024] The term "projection system" PS as used herein should be interpreted broadly to encompass various types of projection systems, including refractive, reflective, catadioptric, anamorphic, magnetic, electromagnetic and / or electrostatic optical systems, or any combination thereof, appropriate for the exposure radiation used and / or other factors such as the use of an immersion liquid or vacuum. Any use of the term "projection lens" herein may be considered synonymous with the more general term "projection system" PS.

[0025] The lithographic apparatus is of a type (also referred to as immersion lithography) in which at least a part of the substrate W may be covered by an immersion liquid, such as water, having a relatively high refractive index, so as to fill an immersion space 11 between the projection system PS and the substrate W. More information about immersion techniques is given in US 6,952,253, which is incorporated herein by reference.

[0026] The lithographic apparatus may also 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 preparation steps for a subsequent exposure of a substrate W may be performed on a substrate W located on one substrate support WT while another substrate W on the other substrate support WT is being used to expose a pattern onto another substrate W.

[0027] In addition to the substrate support WT, the lithographic apparatus may comprise a measurement stage (not shown). The measurement stage is arranged to hold a sensor and / or a cleaning device. The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning device may be arranged to clean parts of the lithographic apparatus, for example parts of the projection system PS or parts 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.

[0028] In operation, a radiation beam B is incident on a patterning device, such as a 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. After passing through the mask MA, the radiation beam B passes through a projection system PS, which focuses the beam onto a target portion C of a substrate W. The substrate support WT may be accurately driven by the second positioner PW and position measurement system IF, for example, to position different target portions C at focusing and alignment positions in the path of the radiation beam B. Similarly, the first positioner PM and other appropriate position sensors (not explicitly shown in FIG. 1 ) may be used to accurately position the patterning device MA with respect to the path of the radiation beam B. The patterning device MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2. Although the illustrated substrate alignment marks P1, P2 occupy dedicated target portions, they may also be located in spaces between the target portions. Substrate alignment marks P1, P2 located between target portions C are known as scribe-lane alignment marks.

[0029] To clarify the 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 around the x axis is referred to as Rx rotation. Rotation around the y axis is referred to as Ry rotation. Rotation around the z axis is referred to as Rz rotation. The x and y axes define a horizontal plane, and the z axis defines a vertical direction. The Cartesian coordinate system is not intended to limit the invention and is used for illustration purposes only. Alternatively, other coordinate systems, such as a cylindrical coordinate system, may be used to clarify the invention. The orientation of the Cartesian coordinate system may be different, for example, so that the z axis has a component along the horizontal plane.

[0030] Immersion techniques have been introduced into lithography systems to enable improved resolution of smaller 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 towards the substrate W) and the substrate W. The immersion liquid covers at least a portion of the substrate W below the final element of the projection system PS. In this way, at least a portion of the substrate W during exposure is immersed in the immersion liquid.

[0031] In commercial immersion lithography, the immersion liquid is water. The water is typically highly pure distilled water, such as ultrapure water (UPW), commonly used in semiconductor manufacturing plants. In immersion systems, the UPW is frequently purified and may have to undergo additional processing steps before being supplied to the immersion space 11 as the immersion liquid. Other liquids besides water that have a high refractive index, such as hydrocarbons such as fluorocarbons and / or aqueous solutions, may also be used as the immersion liquid. Furthermore, other fluids besides liquids are anticipated for use in immersion lithography.

[0032] Reference is made herein to localized immersion, where the immersion liquid in use is confined to 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 references in the following text to the surface of the substrate W may also or instead refer to the surface of the substrate support WT, and vice versa, unless otherwise stated). 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, filled with immersion liquid, is smaller in plan than the top surface of the substrate W, and remains substantially stationary relative to the projection system PS while the substrate W and substrate support WT move underneath.

[0033] Other immersion systems are also envisaged, such as unconfined immersion systems (so-called "all wet" immersion systems) and bath-based immersion systems. In an unconfined 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 liquid film. The liquid may cover the entire surface of the substrate W or the substrate W and a substrate support WT flush with the substrate W. In a bath-based system, the substrate W is completely immersed in a bath of immersion liquid.

[0034] 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 are 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 withdraw immersion liquid from the immersion space 11 and that operate in response to relative movement of a stage below the projection system PS. In newer designs, the fluid handling structure extends along at least part of the boundary of the immersion space 11 between the final element 100 of the projection system PS and the substrate support WT or substrate W, and partially defines the immersion space 11.

[0035] The fluid handling structure 12 may have a choice of different functions, each of which may result from corresponding features that enable the fluid handling structure 12 to perform that function. The fluid handling structure 12 may be referred to by a number of different terms, each describing a function, such as barrier member, sealing member, fluid supply system, fluid removal system, liquid confinement structure, etc.

[0036] The fluid handling structure 12 as a barrier member is a barrier to the flow of immersion liquid from the immersion space 11. As a liquid confinement structure the structure confines the immersion liquid to the immersion space 11. As a seal member the sealing features of the fluid handling structure 12 form seals to confine the immersion liquid to the immersion space 11. The sealing features may include an additional gas flow from openings in the surface of the seal member, such as a gas knife.

[0037] In an embodiment, the fluid handling structure 12 may provide the immersion fluid as a fluid supply system.

[0038] In an embodiment, the fluid handling structure 12 may at least partly confine the immersion fluid as a fluid confinement system.

[0039] In an embodiment, the fluid handling structure 12 may provide a barrier to the immersion fluid as a barrier member, such as a fluid confinement structure.

[0040] In an embodiment, the fluid handling structure 12 may generate or use a gas flow, for example to help control the flow and / or position of the immersion fluid.

[0041] The gas flow may form a seal to confine the immersion fluid and the fluid handling structure 12 may be referred to as a seal member. Such a seal member may be a fluid confinement structure.

[0042] In an embodiment, an immersion liquid is used as the immersion fluid, and the fluid handling structure 12 in this case may be a liquid handling system. With reference to the above description, references in these paragraphs to features defined in relation to a fluid are understood to include features defined in relation to a liquid.

[0043] 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. To reach the substrate W, the path of the radiation beam B passes from the projection system PS through immersion liquid confined by a fluid handling structure 12 between the projection system PS and the substrate W. The projection system PS has a lens element at the end of the beam's path that comes into contact with the immersion liquid. This lens element that comes into 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 an opposing surface.

[0044] Figures 2a, 2b, 2c and 2d show different features that may be present in various fluid handling systems. 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 a fluid handling system with different features illustrated on the left and right sides, which may extend around the entire periphery. Thus, for example, a fluid handling system may have the same feature extending around the entire periphery. For example, a fluid handling system may only have the feature on the left side of Figure 2a, or the right side of Figure 2a, or the left side of Figure 2b, or the right side of Figure 2b, or the left side of Figure 2c, or the right side of Figure 2c, or the left side of Figure 2d, or the right side of Figure 2d. Alternatively, a fluid handling system may be provided with any combination of features from these figures, at different circumferential positions. The fluid handling system may comprise various fluid handling structures 12, as described below.

[0045] Figure 2a shows the fluid handling structure 12 around the bottom surface of the final element 100. The final element 100 has an inverted truncated conical shape. The truncated conical shape has a flat bottom and a conical surface. The truncated conical shape has a flat bottom protruding from the flat surface. The flat bottom is the optically active part of the bottom surface of the final element 100 through which the radiation beam B may pass. The final element 100 may have a coating 30. The fluid handling structure 12 surrounds at least part of the 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 fit around the truncated conical shape of the final element 100. The bottom surface of the fluid handling structure 12 may be substantially flat and, in use, the bottom surface 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 thus 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 30 to 500 micrometers, desirably in the range of 80 to 200 micrometers.

[0046] 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 the inner surface of the fluid handling structure 12, the 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 (in an embodiment at least part of the space between the complementary inner surfaces and the conical surface).

[0047] Immersion liquid is supplied to the immersion space 11 through openings formed in a surface of the fluid handling structure 12. Immersion liquid may be supplied through supply openings 20 in an inner surface of the fluid handling structure 12. Alternatively or additionally, immersion liquid is supplied from lower supply openings 23 formed in a bottom surface of the fluid handling structure 12. The lower supply openings 23 may surround the path of the radiation beam B and may be formed as a series of openings in an array or a single slit. Immersion liquid is supplied to fill the immersion space 11 and the flow through the immersion space 11 below the projection system PS is laminar. Supply of immersion liquid from the lower supply openings 23 additionally prevents bubbles from entering the immersion space 11. This supply of immersion liquid may act as a liquid seal.

[0048] 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 caused by application of reduced pressure. Recovery through the recovery openings 21 may be the result of a flow rate of immersion liquid through the immersion space 11. Alternatively, recovery may be the result of both. The recovery openings 21 may be located opposite the supply openings 20 in plan view. Additionally or alternatively, immersion liquid may be recovered through an overflow recovery part 24 located on the top surface of the fluid handling structure 12. The functions of the supply openings 20 and recovery openings 21 may be swapped (i.e. the liquid flow direction is reversed). In this case, the flow direction can be changed depending on the relative movement of the fluid handling structure 12 and the substrate W.

[0049] Additionally or alternatively, immersion liquid may be recovered from below the fluid handling structure 12 through recovery openings 25 formed in its bottom surface. The recovery openings 25 may serve to hold a meniscus 33 of immersion liquid against 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 external gas environment. The recovery openings 25 may be a perforated plate which may recover a single-phase flow of immersion liquid. The recovery openings in the bottom surface may be a series of pinning openings 32 through which immersion liquid is recovered. The pinning openings 32 may recover a two-phase flow of immersion liquid.

[0050] Optionally, a gas knife opening 26 is provided radially outwardly relative to the inner surface of the fluid handling structure 12. Gas may be supplied through the gas knife opening 26 at an increased velocity 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 is provided a gas recovery opening 28 for recovering gas supplied through the gas knife opening 26.

[0051] Further openings, for example those open to atmosphere, a gas source or vacuum, may be present at the bottom surface of the fluid handling structure 12, i.e. the surface of the fluid handling structure 12 facing the substrate W. An example of such an optional further opening 50 is shown by the dotted line on the right-hand side of Figure 2a. As shown, the further opening 50 may be a supply or an outlet, as indicated by the double arrow. For example, if configured as a supply, the further opening 50 may be connected to a liquid supply or a gas supply or any other supply. Alternatively, if configured as an outlet, the further opening 50 may be used to extract fluid and may be connected to, for example, 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 pinning opening 32 and the gas knife opening 26.

[0052] Two different versions of the fluid handling structures 12 on the left and right sides of FIG. 2a hold the meniscus 33. The version of the fluid handling structure 12 on the right side of FIG. 2a may hold the meniscus 33 in a position substantially fixed relative to the final element 100 due to the fixed position of the pinning aperture 32. The version of the fluid handling structure 12 on the left side of FIG. 2a may hold the meniscus 33 below the recovery aperture 25, and the meniscus 33 may move along the length and / or width of the recovery aperture 25. To direct the radiation beam B to both ends of the substrate W during exposure, the substrate support WT supporting the substrate W is driven relative to the projection system PS. To maximize the output of the substrate W exposed by the lithographic apparatus, the substrate support WT (and also the substrate W) is driven as fast as possible. However, there is a critical relative speed (often expressed as the critical scan speed), beyond which the meniscus 33 between the fluid handling structure 12 and the substrate W becomes unstable. An unstable meniscus 33 is associated with a greater risk, for example, of losing the immersion liquid in the form of one or more droplets. Furthermore, an unstable meniscus 33 is associated with a greater risk of introducing air bubbles into the immersion liquid, especially when the limited immersion liquid exceeds the edge of the substrate W.

[0053] Droplets present on the surface of the substrate W can impose a heat load and can cause defects. Droplets can evaporate and leave a dry spot, can move and carry contaminants such as particles, can collide with a larger mass of immersion liquid and introduce gas bubbles into the larger mass, and can evaporate and impose a heat load on the surface on which they are disposed. Such a heat load can be a cause of distortion and / or a source of positioning error when the surface is related to the positioning of components of the lithographic apparatus with respect to the substrate W during imaging. Thus, the formation of droplets on the surface is undesirable. To avoid the formation of such droplets, the speed of the substrate support WT is limited to the critical scan speed at which the meniscus 33 is stable. This limits the throughput of the lithographic apparatus.

[0054] 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 exert a biasing force on the fluid handling structure 12 in the direction of the substrate W. In this way, the spring 60 may 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 (e.g., those using electromagnetic forces) are also suitable. The spring 60 is optionally shown with the left-hand side of Figure 2a, but does not need to be included 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 be included with various other fluid handling systems described in relation to Figures 2a, 2b, 2c, or 2d.

[0055] Figure 2b shows, on the left and right, two different versions of the fluid handling structure 12 that allow 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 velocity between the meniscus 33 and the moving substrate W, which may result in improved stability and a reduced risk of collapse of the meniscus 33. Increasing the velocity of the substrate W at which the meniscus 33 collapses allows for faster movement of the substrate W below the projection system PS. In this way, throughput is increased.

[0056] Features shown in Figure 2b that are in common with Figure 2a share the same reference numerals. The fluid handling structure 12 has an inner surface that is 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 flat bottom surface of the frusto-conical shape.

[0057] 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 located at the bottom side 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 away from the path of the radiation beam B.

[0058] 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 below the fluid handling structure 12, a meniscus 33 may move on the surface of the recovery opening 25 in the same direction as the movement of the facing surface. The recovery openings 25 may be formed of a porous member. The immersion liquid may be recovered in a single phase. The immersion liquid may be recovered in a two-phase flow. The two-phase flow is received in a chamber 35 in the fluid handling structure 12 and separated into liquid and gas. The liquid and gas are recovered from the chamber 35 through further channels 36, 38.

[0059] An inner periphery 39 of the bottom of the fluid handling structure 12 extends from the inner surface into the immersion space 11 to form a plate 40. The inner periphery 39 defines a small opening of a size that matches the shape and size of the radiation beam B. The plate 40 may serve to isolate the immersion liquid at either end. Immersion liquid supplied flows inward towards the opening, through the inner opening and radially outwards towards the surrounding recovery opening 25 below the plate 40.

[0060] 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 opposing 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.

[0061] Thus, 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, enabling faster scanning speeds and increased throughput of the lithographic apparatus. However, the speed of movement of the meniscus 33 on 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 allows faster movement of the meniscus 33 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 provided between the inner part 12a and the outer part 12b to prevent contact between them.

[0062] Figure 2c shows, on the left and right, two different versions of a fluid handling structure 12 that may be used to pin a meniscus 33 of immersion liquid to a fluid handling structure 12 as described above with respect 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.

[0063] 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 facing surface than the flat bottom surface of the frusto-conical 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 structure 12. Alternatively or additionally, the immersion liquid may be supplied through supply openings 20 in the inner surface of the fluid structure 12. Alternatively or additionally, the immersion liquid may be supplied through lower supply openings 23. The immersion liquid may be collected via an outlet (e.g. a collection opening 21 and / or an overflow collection opening 24 formed in the inner surface and / or one or more openings in the surface of the fluid handling structure 12 as described below).

[0064] The two different versions of the fluid handling structure 12 on the left and right of Figure 2c pin the meniscus 33. The version of the fluid handling structure 12 on the right of Figure 2c may pin the meniscus 33 in a substantially fixed position relative to the final element 100 due to the fixed position of the collection opening 32a. The version of the fluid handling structure 12 on the left of Figure 2c may pin 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.

[0065] 2c. As described above with respect to Figure 2b, the inner periphery of the bottom surface of the fluid handling structure 12 may extend from the inner surface into the immersion space 11 to form a plate 40 as shown on the left. As described above, this may form small openings, may isolate the immersion liquid at either end, and / or may allow immersion liquid to flow inward towards the opening, through the inner opening and radially outward towards a surrounding recovery opening 25 below the plate 40. This feature is shown on the left in Figure 2c, but may optionally be combined with the other shown features. Preferably, as shown on the left, 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 located at the bottom side of the inner surface (e.g. below the bottom surface of the frusto-conical shape). The supply openings 34 are located around the inner surface, away from 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 structure 12. Alternatively or additionally, immersion liquid is supplied through lower supply openings 23. Supply openings 34 are the preferred liquid supply, although any combination of supply openings 34, supply openings 20 and / or lower supply openings 23 may be provided.

[0066] As shown on the left side of Figure 2c, the fluid handling system may comprise a fluid handling structure 12 as described above and a further device 3000. The fluid handling structure 12 may have an outlet such as a recovery opening 25 and a liquid supply opening such as a lower supply opening 23. It will be appreciated that the fluid handling structure 12, in combination with the further device 3000, may have any configuration as 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 the right side of Figure 2c (described below).

[0067] The further device 3000 may be referred to as a droplet catcher. The further device 3000 is provided to reduce the amount of liquid remaining on the surface of the substrate W after the fluid handling structure 12 has moved over the surface. The further device 3000 may comprise a liquid supply 3010 and at least one outlet 3020. The at least one outlet 3020 may be shaped to surround the at least one supply 3010 in plan view. The at least one liquid supply 3010 may be configured to provide the further liquid to a space 3110 between at least part of the further device 3000 and the surface of the substrate W. The further device 3000 may be configured to recover at least part of the liquid via the at least one outlet 3020. The further device 3000 may be used to combine the liquid remaining on the surface of the substrate W with the liquid in the space 3110, and the further device 3000 is used to remove the liquid so that the amount of liquid remaining on the surface of the substrate W is reduced.

[0068] In Figure 2c the further device 3000 is shown as a separate device to the fluid handling structure 12. The further device 3000 may be located in the vicinity of the fluid handling structure 12. Alternatively, the further device 3000 may be part of (i.e. configured integrally with) the fluid handling structure 12 (see Figure 3d, although either configuration is an option).

[0069] The further device 3000 may be configured to provide a liquid to the space 3110 that is separate from the liquid provided by the fluid handling structure 12 .

[0070] 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, two outlets (e.g. recovery openings 32a and 32b) and two gas supply (e.g. gas supply openings 27a and 27b) formed on a surface of the fluid handling structure 12. Gas supply opening 27a may be omitted, i.e. is optional. The at least one liquid supply may be the same as the lower supply opening 23, supply opening 20 in the bottom surface of the fluid handling structure 12 described above, or the liquid supply opening 34 formed on an internal surface of the fluid handling structure 12 as described with respect to the left-hand side of Figure 2b. The liquid supply, outlets and gas supply may be formed on a surface of the fluid handling structure 12. Specifically, these components may be formed on the surface of the fluid handling structure 12 facing the substrate W, i.e. the bottom surface of the fluid handling structure 12.

[0071] At least one of the two outlets may comprise a porous material 37 therein. The porous material 37 may be provided in an opening, for example recovery opening 32a through which the fluid handling structure 12 may recover single-phase immersion liquid from the fluid handling structure 12 below. The other of the two outlets, such as recovery opening 32b, may recover immersion fluid as a two-phase outlet. The porous material 37 may not be flush with the bottom surface of the fluid handling structure 12.

[0072] In particular, the fluid handling structure 12 may comprise a liquid supply (e.g. lower supply opening 23). Radially outward from the liquid supply is a first outlet (e.g. recovery opening 32a), radially outward from the first outlet is a first gas supply (e.g. gas supply opening 27a), radially outward from the first gas supply is a second outlet (e.g. recovery opening 32b) and radially outward from the second outlet is a second gas supply (e.g. gas supply opening 27b). As with Figure 2a, further openings, for example those open to atmosphere, a gas source or vacuum, may be present in the bottom surface of the fluid handling structure 12, as described above (in relation to the fluid handling structure 12).

[0073] For example, at least one further opening (not shown) may be provided in the bottom surface of the fluid handling structure 12. The further opening is optional. The further opening may be provided between the first outlet (e.g. collection opening 32a) and the first gas supply (e.g. gas supply opening 27a) as described in the arrangements above. Alternatively or in addition, the further opening may be provided between the second outlet (e.g. collection opening 32b) and the second gas supply (e.g. gas supply opening 27b) as described in the arrangements above. The further opening may be the same as the further opening 50 described above.

[0074] 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 fluid handling structure 12 or may optionally include a sloped surface. If a recess 29 is provided between the collection openings 32a and 32b, the gas supply opening 27b may be provided in the sloped surface, as shown in Figure 2c. If a recess 29 is provided between the supply openings 27a and 32b, the gas supply opening 27b may be provided in the sloped surface or in a part of the 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 fluid handling structure 12. The shape of the recess 29 may be varied to change the effect of gas supplied from the gas supply on the fluid below the fluid handling structure 12.

[0075] Figure 2d shows two different versions of the fluid handling structure 12, in left and right halves. The fluid handling structure 12 in the left half of Figure 2d has 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 sides of the liquid injection holes 41 are provided inner liquid recovery openings 43 for directing liquid to inner recovery buffers 43a in which a porous member is provided. Recesses 29 similar to those described in relation to Figure 2c are provided outer sides of the inner liquid recovery openings 43. Outer sides of the recesses 29 in the underside of the fluid handling structure 12 are provided gas guide grooves 44 into which outer recovery holes 44a open. The outer recovery holes 44a direct a two-phase recovery flow to outer recovery buffers 44b in which a porous member is provided. Outermost, gas sealing holes 45 are provided connecting between the gas sealing buffer volume 45a and the space below the fluid handling structure 12 to provide a gas flow for inclusion in the immersion liquid.

[0076] The fluid handling structure 12 in the right half of Figure 2d has a liquid supply opening 20 in its inner sloping surface. Provided below the fluid handling structure 12 are (from the inside to the outside) an extraction opening 25 provided with a porous member 37, a first gas knife opening 26a, a second gas knife opening 26b and a third gas knife opening 26c. Each of these openings opens into a groove below the fluid handling structure 12 which provides a buffer volume. The outermost part of the fluid handling structure 12 is stepped to provide greater spacing between the fluid handling structure 12 and the substrate W.

[0077] 2a-2d show examples of different configurations that may be used as part of a fluid handling system. While the examples provided above refer to specific extraction and recovery sections, it is understood that the exact same type of extraction and / or recovery section need not be used. In some cases, different terminology is used to indicate the location of the components, but the same functional features may be provided. Examples of the aforementioned extraction sections include recovery opening 21, overflow recovery section 24, recovery opening 25 (preferably comprising a perforated plate and / or chamber 35), gas recovery opening 28, pinning opening 32, recovery opening 32a, recovery opening 32b, and / or intermediate recovery section 42. Examples of the aforementioned supply sections 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 sections used to extract / recover fluids, liquids, or gases are interchangeable with other uses for extracting / recovering fluids, liquids, or gases, respectively. Similarly, supplies used to supply fluids, liquids or gases are interchangeable with other uses for supplying fluids, liquids or gases, respectively. An extraction may extract / recover fluids, liquids or gases from a space by being connected to a reduced pressure that draws the fluid, liquid or gas into the extraction. A supply may supply fluids, liquids or gases to a space by being connected to a corresponding supply.

[0078] As previously mentioned, while the use of immersion fluid / liquid is useful in increasing the resolution of smaller features on a substrate, there are challenges with the use of immersion fluid / liquid in terms of defects introduced on the substrate.

[0079] Generally, when an immersion liquid is used, droplets of the immersion liquid may be left behind on the surface of the substrate W. The meniscus 33 at the edge of the immersion liquid may collide with the droplets on the surface of the substrate W. When the droplets hit the meniscus 33, gas may become trapped in the immersion liquid. This results in bubbles in the immersion liquid. The formation of bubbles in the immersion liquid may lead to defects on the substrate W. The droplets remaining on the surface of the substrate W may cause dried spots and / or affect the chemical properties of the resist, leading to defects.

[0080] It is known that the rate of droplet generation increases with the movement speed of the substrate W relative to the fluid handling system. In some cases, there is no / negligible droplet formation below a critical scan speed, and non-negligible droplet formation above the critical scan speed. The critical scan speed is related to the static receding contact angle between the immersion liquid and the resist provided on the substrate W. As the static receding contact angle increases, the critical scan speed also increases. Since the critical scan speed can be a limiting factor for the throughput of a lithography apparatus, it is desirable to increase the critical scan speed. Efforts to increase the critical scan speed include increasing the static receding contact angle by changing the composition of the resist or by providing a topcoat on the resist. However, further improvement is desired.

[0081] The present invention may reduce the effects of at least one droplet related problem.The present invention includes various embodiments of a droplet mitigation system that may be used in all types of localized immersion lithography apparatus.

[0082] As described in detail below, embodiments provide a fluid handling system in which a meniscus of fluid moves in response to relative movement of the substrate and the fluid handling system, advantageously increasing the maximum allowable speed of relative movement between the fluid handling system and the substrate without substantial droplet formation.

[0083] Figures 3a and 3b show part of a fluid handling system 301 according to a first embodiment. The fluid handling system 301 may confine immersion liquid to a liquid confinement space between part of the projection system PS and the surface of the substrate W. The immersion liquid may be any of the immersion fluids mentioned above. For example, the immersion liquid may be water. A radiation beam B projected from the projection system PS may irradiate the surface of the substrate W through the immersion liquid.

[0084] Figure 3a shows only a part of the fluid handling system 301 that supports a meniscus 310 of immersion liquid. The meniscus 310 forms a boundary between the immersion liquid and the ambient environment of the fluid handling system 301. Although not shown in Figure 3a, the main part of the fluid handling system 301 is disposed in the direction indicated by arrow 306. The main part of the fluid handling system 301 may comprise immersion liquid and may comprise any part of the various structures disclosed above with reference to Figures 2a to 2d or any other system that localizes immersion liquid below the projection system PS. In particular, the main part of the fluid handling system 301 may comprise a lens bus such as lens bus 11 as described with reference to Figures 2a to 2d.

[0085] As shown in Figure 3a, a fluid handling system 301 is provided above a substrate W. The substrate W may comprise a wafer 305 and a resist coating 304 on the wafer 305. There is a channel 308 between the fluid handling system 301 and the substrate W. A part of the channel 308 between a main part of the fluid handling system 301 and a meniscus 310, arranged in a direction 306, may comprise immersion liquid. A part of the channel 308 between the meniscus 310 and an environment external to the fluid handling system 301, arranged in a direction 307, may comprise gas.

[0086] The fluid handling system 301 comprises a first outlet portion 302. The first outlet portion 302 comprises a first outlet conduit 302b. The first outlet conduit 302b is a fluid conduit and may provide a flow of immersion liquid out of the fluid handling system 301. The first outlet portion 302 also comprises a first outlet opening 302a provided in an upper surface of the channel 308. The first outlet opening 302a is an end of the first outlet conduit 302b.

[0087] The fluid handling system 301 comprises a second outlet portion 303. The second outlet portion 303 comprises a second outlet conduit 303b. The second outlet conduit 303b is a conduit for a fluid, such as a gas. The second outlet portion 303 also comprises a second outlet opening 303a provided in an upper surface of the channel 308. The second outlet opening 303a is the end of the second outlet conduit 303b.

[0088] Between the first outlet 302 and the second outlet 303 is an upper surface of the channel 308 designated as damper 311. The length of damper 311 defines the spacing of the first outlet 302 and the second outlet 303 along the length of the channel 308.

[0089] The first outlet 302 may be configured to remove immersion liquid by means of a fluid flow 309. The fluid flow through the first outlet 302 may be substantially only immersion liquid in the fluid flow 309. However, the first outlet 302 may also remove gas from an environment external to the fluid handling system 301. In this way, the fluid flow through the first outlet 302 may be a two-phase flow.

[0090] The second outlet 303 may be configured to extract gas from the channel 308. Figure 3b shows the gas extraction gas flow 314. The gas flow 314 may create a reduced pressure in the channel 308.

[0091] Although not shown in Figures 3a and 3b, a main part of the fluid handling system 301 arranged in direction 306 may comprise a fluid handling structure having an inner surface configured to confine immersion liquid. The first outlet 302 and the second outlet 303 are arranged radially away from the main part of the fluid handling system 301. The second outlet 303 may be arranged further away from the inner surface of the fluid handling structure than the first outlet 302. Alternatively, the first outlet 302 and the second outlet 303 may be part of the main part of the fluid handling system 301. The second outlet 303 may be arranged further away from the centre of the fluid handling system 301 than the first outlet 302.

[0092] A first operational state of the fluid handling system 301 is shown in Figure 3a. In the first operational state, there is no relative movement between the substrate W and the fluid handling system 301. The first outlet 302 may be configured such that, in the first operational state, the amount of immersion liquid removed therethrough does not substantially exceed the amount required to maintain the meniscus 310 at substantially the same position along the channel 308. The fluid flow rate through the first outlet 302 is the minimum flow rate that is capable of keeping the meniscus 310 substantially stationary in the absence of relative movement between the substrate W and the fluid handling system 301.

[0093] A second operational state of the fluid handling system is shown in Figure 3b. In the second operational state, the substrate W may move relative to the fluid handling system 301. The second operational state comprises a scanning movement in a scanning direction. The scanning direction may be substantially perpendicular to the direction of propagation of the radiation beam B. The scanning direction may be direction 312 as shown in Figure 3b. It should be noted that the second operational state may comprise relative movements between the substrate W and the fluid handling system 301 other than the scanning movement. For example, the second operational state may comprise a preparatory movement before the scanning movement.

[0094] The first outlet 302 may be configured such that the amount of immersion liquid extracted therethrough is substantially the same in both the first and second operating states. Movement of the substrate W in direction 312 generates a shear force on the immersion liquid in the channel 308. This causes the meniscus 310 to move along the channel 308 in direction 313. The increased flow of immersion liquid into the channel 308 may be described as Couette flow, or alternatively as shear-driven flow or pressure-driven flow. The creation of a reduced pressure in the channel 308 by the gas flow 314 also supports the movement of the meniscus 310 along the channel 308.

[0095] In the second operating state, the meniscus 310 is not held stationary by the fluid flow through the first outlet 302. The fluid flow through the first outlet 302 is sufficient to keep the meniscus 310 stationary only if there is no relative movement between the fluid handling system 301 and the substrate W. Thus, in the second operating state, the meniscus 310 moves along the channel 308. Advantageously, the maximum allowable speed of relative movement between the fluid handling system 301 and the substrate W is increased. The speed of relative movement between the meniscus 310 and the substrate W is below a critical scan speed so that significant droplet formation does not occur. The speed of relative movement between the fluid handling system 301 and the meniscus 310 increases the speed of relative movement between the fluid handling system 301 and the substrate W. The speed of relative movement between the fluid handling system 301 and the substrate W can be increased by up to twice the critical scan speed of known systems in which the meniscus 310 in the channel 308 is substantially stationary.

[0096] The distance that the meniscus 310 may move along the channel 308 depends on the length of the surface of the damper 311 between the first outlet 302 and the second outlet 303. The length of the surface of the damper 311 between the first outlet 302 and the second outlet 303 is between about 1 mm and about 100 mm, preferably between about 1 mm and about 50 mm, preferably greater than about 20 mm, preferably greater than about 30 mm, more preferably greater than about 30 mm.

[0097] The damper 311 may be configured such that its surface properties support proper movement of the edge of the meniscus 310. In particular, the surface of the damper 311 may be coated or configured to be either liquidphobic, liquidphilic, or porous.

[0098] The surface of the damper 311 may be configured so that it is substantially parallel to the surface of the substrate W.

[0099] Alternatively, the surface of the damper 311 may be curved or sloped away from the surface of the substrate W. A first end of the surface of the damper 311 is at the first outlet 302 and a second end of the surface of the damper 311 is at the second outlet 303. The surface of the damper 311 may be configured such that the distance between the surface of the damper 311 and the surface of the substrate W is greater at the second end than at the first end.

[0100] The damper 311 mentioned above may be referred to as the first damper 311. As shown in at least Figures 3a and 3b, the fluid handling system 301 may comprise a second damper 315. The surface of the second damper 315 is a length of the upper surface of the channel 308 on the other side of the first outlet 302 to the first damper 311. The second damper 315 may be configured such that immersion liquid is supported between the surface of the second damper 315 and the surface of the substrate W.

[0101] The surface of the second damper 315 may be parallel to the surface of the substrate W. The distance between the surface of the second damper 315 and the surface of the substrate W may be the same as the distance between all or at least a portion of the surface of the first damper 311 and the surface of the substrate W. Alternatively or additionally, the distance between all or at least a portion of the surface of the first damper 311 and the surface of the substrate W may be larger than the distance between at least a portion of the surface of the second damper 315 and the surface of the substrate W.

[0102] A second embodiment is shown in Figure 4. The fluid handling system 301 of the second embodiment may comprise all of the above-mentioned features of the fluid handling system 301 of the first embodiment. The fluid handling system 301 of the second embodiment differs from the fluid handling system 301 of the first embodiment in that it further comprises a first valve 401 and a second valve 402.

[0103] A first valve 401 may be provided to control the flow of fluid through the first outlet 302. The first valve 401 may be provided in the first outlet conduit 302b of the first outlet 302.

[0104] A second valve 402 may be provided to control the flow of fluid through the second outlet 303. The second valve 402 may be provided in the second outlet conduit 303b of the second outlet 303.

[0105] Advantageously, the first valve 401 and the second valve 402 provide improved control of fluid flow and pressure within the channel 308, thereby improving control of the movement of the meniscus 310 along the channel 308.

[0106] Figure 4 also shows further features of the fluid handling system 301 that may be present in any embodiment of the fluid handling system 301 disclosed herein.

[0107] For example, the fluid handling system 301 may further comprise a fluid supply opening 403. The fluid supply opening 403 may be an opening in the upper surface of the channel 308. The fluid supply opening 403 may be separated from the first outlet 302 by a length of the upper surface of the channel 308. As mentioned above, this may be a surface of the second damper 315. The fluid supply opening 403 may be a supply of immersion liquid into the channel 308. The supply of immersion liquid to the channel 308 may create pressurization of the immersion liquid in the channel 308. Although not shown in Figures 3a and 3b, the embodiments shown here may comprise a fluid supply opening 403. The embodiments also include the use of a valve at the fluid supply opening 403 to improve control of fluid flow and pressure in the channel 308.

[0108] 4 also shows a length of the upper surface 316 of the channel 308 that starts at the second outlet 303 and extends in the direction 307 towards the environment external to the fluid handling system 301. As shown in FIG. 4, a part of the upper surface 316 of the channel 308 adjacent the second outlet 303 may be parallel to the surface of the substrate W. Other parts of the upper surface 316 of the channel 308 further away from the second outlet 303 may be sloped / curved so that the spacing between the upper surface 316 of the channel 308 and the surface of the substrate W varies. As shown in FIG. 4, the spacing between the upper surface 316 of the channel 308 and the surface of the substrate W may increase. However, embodiments also include cases where the spacing between the upper surface 316 of the channel 308 and the surface of the substrate W locally decreases and then increases. The pressure of the gas in the channel 308 may depend on the shape of the upper surface 316. The shape of the surface 316 may be determined to create an appropriate pressure of gas within the channel 308 to support movement of the meniscus 310 under the intended operating conditions.

[0109] A third embodiment is shown in Figure 5. The fluid handling system 301 of the third embodiment may comprise some or all of the above-mentioned features of the fluid handling system 301 of the first and second embodiments.

[0110] The fluid handling system 301 of the third embodiment differs from the fluid handling systems 301 of the first and second embodiments in that it further comprises a third output conduit 501. The third output conduit 501 is in fluid communication with both the first output conduit 302b and the second output conduit 303b. A connecting conduit 502 may be provided between the second output conduit 303b and the third output conduit 501. The connecting conduit 502 may be part of the second output conduit 303b. The fluid flow through the third output conduit 501 may comprise both immersion liquid and gas (i.e. two-phase flow).

[0111] In a first implementation of the third embodiment, the first extraction conduit 302b, the second extraction conduit 303b and the third extraction conduit 501 may not be provided with valves. The shape / geometry of the first extraction conduit 302b, the second extraction conduit 303b and / or the third extraction conduit 501 is adjusted so that under the intended operating conditions the pressure of the gas and / or immersion liquid is adequate to provide movement of the meniscus 310 along the channel 308. Advantageously, the pressure naturally generated within the channel 308 is adequate to passively support movement of the meniscus 310.

[0112] In a second example of the third embodiment, the third output conduit 501 is provided with a valve, while the first output conduit 302b and the second output conduit 303b are not. As described for the first example, the shape / geometry of the first output conduit 302b and the second output conduit 303b may be adjusted to naturally generate the appropriate pressure to support movement of the meniscus 310 along the channel 308. The valve in the third output conduit 501 may be used to control the fluid flow through the third output conduit 501. This may improve control of the meniscus 310 movement.

[0113] In a third implementation of the third embodiment, valves are provided in some or all of the first output conduit 302b, the second output conduit 303b and the third output conduit 501. The valves in the first output conduit 302b and the second output conduit 303b may be the same as those described for the second embodiment and shown in Figure 4. Advantageously, the valves may improve control of meniscus 310 movement.

[0114] A fourth embodiment is shown in Figure 6. The fluid handling system 301 of the fourth embodiment may comprise some of the previously described features of the fluid handling systems 301 of the first, second and third embodiments.

[0115] The fourth embodiment is different from the first, second and third embodiments in that it includes a first extraction section 302 but does not include a second extraction section 303.

[0116] In a fourth embodiment, movement of the meniscus 310 along the channel 308 may be passively supported by an intrinsic pressure that generates in the channel 308 during operation. For example, surface tension may result in a reduced pressure in the channel 308 that supports movement of the meniscus 310 along the channel 308.

[0117] A valve 601 may be provided in the first outlet conduit 302b for controlling fluid flow through the first outlet 302. The valve 601 improves control of fluid flow and / or pressure within the channel 308 and improves control of the movement of the meniscus 310.

[0118] The embodiments described above provide a number of designs for the fluid handling system 301 in which the meniscus 310 may move along the channel 308. One end of the meniscus 310 moves along the surface of the damper 311 and the other end of the meniscus 310 moves along the surface of the substrate W.

[0119] In known systems, the meniscus of immersion liquid is held stationary relative to the fluid handling system. Fluid flow through pinning openings in the channel 308 between the fluid handling system and the substrate holds the meniscus against the opening when there is relative movement between the fluid handling system and the substrate. Thus, in known systems, the meniscus is held stationary between the opening and the substrate. The meniscus is not moveably supported between the damper and the substrate.

[0120] An important difference between the embodiment and the known system is that in the embodiment, the fluid flow through the first outlet 302 is less than in the known system. Under all operating conditions, the fluid flow through the first outlet 302 does not substantially exceed the amount required to hold the meniscus 310 stationary when there is no relative movement between the fluid handling system 301 and the substrate W. Hence, the meniscus 310 moves along the channel 308 when there is relative movement between the fluid handling system 301 and the substrate W. In this way, the meniscus 310 can be supported between the damper 311 and the substrate W.

[0121] In the embodiments described above, only a single first outlet 302 has been described. However, embodiments include cases where there is a plurality of first outlets 302. The plurality of first outlets 302 may be arranged around the centre of the fluid handling system 301. The plurality of first outlets 302 may be arranged in any configuration. For example, they may be in a circular, square, rectangular or star-shaped configuration.

[0122] The first extraction opening 302a of each first extraction section 302 may have any shape, for example, each first extraction opening 302a may be circular, square, rectangular, or slot-shaped.

[0123] In the embodiments described above, only a single second outlet 303 has been described. However, embodiments include cases where there is more than one second outlet 303. The multiple second outlets 303 may be arranged around the centre of the fluid handling system 301. For example, they may be in a circular, square, rectangular or star-shaped configuration. The configuration of the second outlet 303 may be the same as or different from the configuration of the first outlet 302.

[0124] The second extraction opening 303a of each second extraction section 303 may have any shape, for example, each second extraction opening 303a may be circular, square, rectangular or slot-shaped.

[0125] Although not shown in Figures 3a to 6, embodiments also include a fluid handling system 301 comprising a number of sensors for measuring conditions within the channel 308 or any conduit. For example, the fluid handling system 301 may comprise any of temperature, pressure or other types of sensors. The fluid handling system 301 may be controlled in response to the sensor measurements. For example, any valves may be actuated in response to the measured pressure. The speed at which the substrate W is driven relative to the fluid handling system 301 may also be controlled in response to the sensor measurements.

[0126] Embodiments may be incorporated into any of the fluid handling systems shown in Figures 2a to 2d. For example, in Figure 2a, the pinning opening 32 may alternatively act as the first outlet 302 of an embodiment. The further opening 50 may alternatively act as the second outlet 303 of an embodiment. The spacing between the pinning opening 32 and the further opening 50 may also be increased to provide an appropriate distance for the meniscus 310 to travel. Similarly, in Figure 2c, the recovery opening 32a may alternatively act as the first outlet 302 of an embodiment. The recovery opening 32b may alternatively act as the second outlet 303 of an embodiment. The spacing between the recovery opening 32a and the recovery opening 32b may also be increased to provide an appropriate distance for the meniscus 310 to travel.

[0127] Embodiments include the presence and use of further features from those specifically described above. In particular, the fluid handling system 301 of embodiments may include one or more pumps for controlling fluid flow through the first outlet 302 and the second outlet 303. One of the pumps for controlling fluid flow through the first outlet 302 and the second outlet 303 may additionally or alternatively be external to the fluid handling system 301.

[0128] The embodiments also include many modifications and variations to the techniques described above.

[0129] For example, in a modification of the second embodiment, a valve may be provided in only one of the first outlet conduit 302b and the second outlet conduit 303b.

[0130] In an alternative embodiment, a variable pump may be used in place of one or more valves.

[0131] Embodiments include each of the first outlet 302 and / or second outlet 303 comprising a porous material and / or a sieve.

[0132] In the embodiments described above, the first and second outlet openings 302a, 303a and the surface of the damper 311 have been described as being at the upper surface of the channel 308. In a typical configuration for a horizontally oriented substrate W, the surface is the upper surface of the channel 308. However, embodiments more generally include the first and second outlet openings 302a, 303a and the surface of the damper 311 being at a surface of the fluid handling system 301 that is substantially parallel to the surface of the substrate W. The surface of the substrate W is not limited to being horizontally oriented.

[0133] The present invention may provide a lithographic apparatus, which may have some or all of the other features or components of the lithographic apparatus as described above. For example, the lithographic apparatus may optionally include at least one or more of a source SO, an illumination system IL, a projection system PS, a substrate support WT, etc.

[0134] In particular, the lithographic apparatus may comprise a projection system PS configured to project a radiation beam B onto a region of a surface of the substrate W. The lithographic apparatus may further comprise a fluid handling system 301 as described in any of the above embodiments and variations.

[0135] The lithographic apparatus may comprise an actuator configured to drive the substrate W relative to the fluid handling system 301. In this way, the actuator may be used to control the position of the substrate W (or alternatively the position of the fluid handling system 301). The actuator may be or comprise a substrate support (e.g. substrate table) WT and / or a substrate holder configured to hold the substrate W and / or a second positioner PW configured to accurately position the substrate support WT.

[0136] Although specific reference may be made in this text to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications, including the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0137] Where the context allows, embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention may also be implemented by instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM), random-access memory (RAM), magnetic storage media, optical storage media, flash memory devices, electrical, optical, acoustic, or other forms of transmission signals (e.g., carrier waves, infrared signals, digital signals, etc.), and the like. Furthermore, firmware, software, routines, and instructions may be described as performing particular actions. However, it should be understood that such description is merely for convenience and that such actions may actually be brought about by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc., causing actuators or other devices to interact with the physical world.

[0138] Although specific reference may be made in this text to embodiments of the invention in the context of a lithography apparatus, embodiments of the invention may be used in other apparatus. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes 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.

[0139] 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 the invention is not limited to optical lithography, where the context permits.

[0140] Embodiments include the following numbered items: 1. A fluid handling system for a lithographic apparatus, the fluid handling system being configured to confine immersion liquid to a liquid confining space between a part of a projection system in the lithographic apparatus and a surface of a substrate so that a radiation beam projected from the projection system can irradiate the surface of the substrate by passing through the immersion liquid, the fluid handling system comprising a damper provided between first and second extraction units configured to both extract fluid, the damper being configured to support a meniscus of the immersion liquid between the surface of the damper and the surface of the substrate. 2. A fluid handling system according to item 1, further comprising a first valve configured to control the flow of fluid through the first outlet. 3. A fluid handling system according to item 1 or 2, further comprising a second valve configured to control the flow of fluid through the second outlet. 4. A fluid handling system according to any of items 1 to 3, wherein the first outlet is configured such that, in use, fluid flowing therethrough consists substantially of immersion liquid. 5. A fluid handling system according to any of items 1 to 4, wherein the second outlet is configured such that, in use, fluid flowing therethrough consists substantially of gas. 6. A fluid handling system according to any of items 1 to 5, wherein the first extraction section comprises a first extraction conduit and a first extraction opening, the first extraction conduit being configured to receive fluid extracted through the first extraction opening, and the second extraction section comprises a second extraction conduit and a second extraction opening, the second extraction conduit being configured to receive fluid extracted through the second extraction opening. 7. A fluid handling system according to item 6, further comprising a third outlet conduit configured to receive fluid from both the first and second outlet conduits. 8. A fluid handling system according to item 7, further comprising a third valve configured to control the flow of fluid through the third outlet conduit. 9. A fluid handling system according to any of the preceding items, wherein the first outlet is configured such that, in use, the fluid flow rate therethrough is substantially constant. 10. A fluid handling system according to any of items 1 to 9, wherein the first outlet is arranged so that, in use, the fluid flow rate through it is a substantial minimum flow rate capable of holding the meniscus stationary when there is no relative movement between the substrate and the fluid handling system. 11. A fluid handling system according to any of items 1 to 10, wherein the damper, the first outlet and / or the second outlet are configured so that, in use, the meniscus moves along a surface of the damper in response to movement of the substrate relative to the fluid handling system. 12. A fluid handling system according to any of items 1 to 11, wherein the length of the damper surface between the first and second outlets is between 1 mm and 100 mm, preferably between 1 mm and 50 mm, and preferably greater than 20 mm. 13. A fluid handling system according to any of items 1 to 12, wherein a surface of the damper is configured to be substantially parallel to a surface of the substrate. 14. A fluid handling system according to any of items 1 to 12, wherein a first end of the surface of the damper is at the first outcoupling and a second end of the surface of the damper is at the second outcoupling, and wherein the surface of the damper is configured such that a spacing between the surface of the damper and the surface of the substrate is greater or smaller at the second end than at the first end. 15. The fluid handling system according to item 14, wherein the surface of the damper is curved, sloped or corrugated. 16. A fluid handling system according to any of items 1 to 15, wherein the damper is a first damper, and the apparatus further comprises a second damper provided on a different side of the first outlet to the first damper and configured so that immersion liquid is supported between a surface of the second damper and a surface of the substrate, and wherein a distance between at least a portion of the surface of the first damper and the surface of the substrate is greater than a distance between at least a portion of the surface of the second damper and the surface of the substrate. 17. A fluid handling system according to any of items 1 to 16, comprising a fluid handling structure having an inner surface configured to confine immersion liquid, the first and second outlet portions being positioned radially away from the inner surface of the fluid handling structure, the second outlet portion being positioned further away from the inner surface of the fluid handling structure than the first outlet portion. 18. A fluid handling system according to any preceding item, wherein there is a plurality of first outlets. 19. A fluid handling system according to item 18, wherein the plurality of first outlets are arranged around the centre of the liquid restriction space, and the plurality of first outlets are optionally arranged in the shape of a circle, a square, a rectangle or a star, or any combination thereof. 20. A fluid handling system according to any preceding item, wherein there is a plurality of second outlets. 21. A fluid handling system according to item 20, wherein the plurality of second outlets are arranged around the centre of the liquid confinement space, and the plurality of second outlets are optionally arranged in the shape of any of a circle, a square, a rectangle or a star, or any combination thereof. 22. A lithographic apparatus comprising a fluid handling system according to any of items 1 to 21. 23. The apparatus of item 22, further comprising a positioning system configured to drive a substrate holder configured to support the substrate relative to the projection system in a plane substantially parallel to a surface of the substrate. 24. A device manufacturing method in a lithographic apparatus having a substrate holder configured to hold a substrate, a projection system configured to project a radiation beam onto a substrate held by the substrate holder, and a fluid handling system according to any of items 1 to 21, the method comprising: using the fluid handling system to confine immersion liquid to a space between at least part of the fluid handling system and a surface of the substrate; projecting a patterned beam of radiation through the immersion liquid in the space onto the substrate; supporting a meniscus of the immersion liquid between a surface of a damper and the substrate; and driving the substrate in a scan direction substantially perpendicular to the direction of propagation of the radiation beam so that the meniscus moves along the surface of the damper in response to movement of the substrate.

[0141] While specific embodiments of the 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 one skilled in the art that modifications may be made to the invention as described without departing from the scope of the following claims.

Claims

1. 1. A fluid handling system for a lithographic apparatus, comprising: configured to confine immersion liquid in a liquid confinement space between a part of a projection system in the lithographic apparatus and a surface of the substrate such that a beam of radiation projected from the projection system can pass through the immersion liquid and thereby illuminate the surface of the substrate; a damper disposed between a first outlet and a second outlet configured to both extract fluid, the damper configured to maintain a meniscus of immersion liquid between a surface of the damper and a surface of the substrate between the first and second outlets; The length of the damper surface between the first and second outlets is between 20 mm and 100 mm; Fluid handling systems.

2. 10. The fluid handling system of claim 1, further comprising a first valve configured to control the flow of fluid through the first outlet and / or a second valve configured to control the flow of fluid through the second outlet.

3. 3. A fluid handling system according to claim 2, wherein the first outlet is configured such that, in use, the fluid flowing therethrough consists substantially of immersion liquid, and / or the second outlet is configured such that, in use, the fluid flowing therethrough consists substantially of gas.

4. the first outlet portion includes a first outlet conduit and a first outlet opening; the first outlet conduit is configured to receive fluid to be withdrawn through the first outlet opening; the second outlet portion includes a second outlet conduit and a second outlet opening; the second outlet conduit is configured to receive fluid to be withdrawn through the second outlet opening; A fluid handling system according to any preceding claim.

5. 5. The fluid handling system of claim 4, further comprising a third outlet conduit configured to receive fluid from both the first and second outlet conduits.

6. 6. The fluid handling system of claim 5, further comprising a third valve configured to control the flow of fluid through the third outlet conduit.

7. 7. A fluid handling system as described in any preceding claim, wherein the first outlet is configured such that, in use, the fluid flow rate through it is substantially constant, and / or the first outlet is provided such that, in use, the fluid flow rate through it is substantially a minimum flow rate that can keep the meniscus stationary when there is no relative movement between the substrate and the fluid handling system.

8. 8. A fluid handling system according to any preceding claim, wherein the damper, the first outlet and / or the second outlet are configured such that, in use, the meniscus moves along a surface of the damper in response to movement of the substrate relative to the fluid handling system, and / or the surface of the damper is configured to be substantially parallel to the surface of the substrate, and / or the surface of the damper comprises a liquidphobic coating.

9. a first end of the surface of the damper at the first outlet; a second end of the damper surface at a second outlet; the surface of the damper is configured such that the spacing between the surface of the damper and the surface of the substrate is greater or smaller at the second end than at the first end; A fluid handling system according to any preceding claim.

10. The fluid handling system of claim 9 , wherein the surface of the damper is curved, sloped or corrugated.

11. The damper is a first damper, the apparatus further comprising a second damper disposed on a different side of the first outlet from the first damper, the second damper configured such that immersion liquid is supported between a surface of the second damper and a surface of the substrate; a distance between at least a portion of the surface of the first damper and the surface of the substrate is larger than a distance between at least a portion of the surface of the second damper and the surface of the substrate; and / or The fluid handling system comprises a fluid handling structure having an inner surface configured to confine immersion liquid; the first and second outlets are located radially spaced from an inner surface of the fluid handling structure; the second outlet is positioned further from the inner surface of the fluid handling structure than the first outlet; A fluid handling system according to any preceding claim.

12. A fluid handling system according to any preceding claim, wherein there is a plurality of first outlets and / or there is a plurality of second outlets.

13. The plurality of first outlet portions are provided around the center of the liquid containment space, the plurality of first outlets are optionally provided in any shape of a circle, a square, a rectangle, or a star, or any combination thereof; and / or The plurality of second outlet portions are provided around the center of the liquid restricted space, The plurality of second outlets are optionally provided in any shape of a circle, a square, a rectangle, or a star, or any combination thereof; 13. A fluid handling system according to claim 12.

14. The plurality of second outlet portions are provided around the center of the liquid restricted space, The plurality of second outlets are optionally provided in any shape of a circle, a square, a rectangle, or a star, or any combination thereof; 13. A fluid handling system according to claim 12.

15. A lithographic apparatus comprising a fluid handling system according to any preceding claim.

Images