Substrate holder, substrate support, lithographic apparatus and method

Abstract

1. A substrate holder configured to support a substrate for exposure in an immersion lithography apparatus, the substrate having a first contact angle with an immersion liquid, the substrate holder comprising a peripheral structure surrounding the substrate and coplanar with the substrate when supported by the substrate holder, the structure comprising a surface structure and an electrode structure below the surface structure, the surface structure having a second contact angle with the immersion liquid, the first contact angle being different from the second contact angle, the electrode structure being configured to modify the contact angle of a portion of the surface structure to make a transition from the first contact angle to the second contact angle, or vice versa, gradual so as to stabilize a meniscus of immersion liquid moving along the surface structure towards or away from the substrate.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to European Patent Application No. 23160526.2, filed March 7, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a substrate holder configured to hold a substrate, a substrate support configured to hold the substrate holder, a lithographic apparatus including the substrate support, and a method for manufacturing a device using the substrate support. [Background technology]

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus has, for example, a projection system for projecting a pattern (often referred to as a "design layout" or "design") in 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 and so-called scanners: in steppers, each target portion is irradiated by exposing the entire pattern onto the target portion at once, and in scanners, each target portion is irradiated by scanning the radiation beam across the pattern in a given direction (scan direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.

[0004]

[0004] As semiconductor manufacturing processes continue to evolve, the dimensions of circuit elements have continually decreased, while the amount of functional elements, such as transistors, per device has steadily increased for decades, following a trend colloquially known as "Moore's Law." To keep up with Moore's Law, the semiconductor industry pursues technologies that enable the creation of smaller and smaller features. 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]

[0005] Further improvements in resolution of smaller features can be achieved by providing an immersion fluid, such as water, with a relatively high refractive index on the substrate during exposure. The immersion liquid has the effect of allowing imaging of smaller features because the exposure radiation has a shorter wavelength in a liquid than in a gas. The immersion liquid can also be seen to increase the effective numerical aperture (NA) of the system, which in turn increases the depth of focus.

[0006]

[0006] The immersion fluid may be confined to a localized area between the projection system of the lithographic apparatus and the substrate by the fluid handling structure.

[0007]

[00] 07 In lithography apparatus that use immersion liquid (often referred to as immersion lithography apparatus), droplets or liquid films left on the substrate can cause defects. For example, when the meniscus of the immersion liquid filling the space between the projection lens and the substrate collides with droplets left on the substrate, gas (e.g., air) bubbles can enter the immersion liquid and enter the beam path. Bubbles in the beam path can distort the image projected onto the substrate and cause defects. Droplets or liquid films can also cause drying marks on the resist.

[0008]

[0008] It is known that if the meniscus of the immersion liquid crosses from the substrate to the cover ring of the substrate holder and / or to the surface of the substrate support supporting the substrate holder, or vice versa, there is a high probability of loss of immersion liquid from the immersion space. Summary of the Invention

[0009]

[0009] The object of the present invention is to provide an arrangement that can reduce loss of immersion liquid when the meniscus of the immersion liquid crosses the boundary between the substrate and the cover of the substrate holder and / or the surface of the substrate support that supports the substrate holder.

[0010]

[0010] According to the present invention, there is provided a substrate holder configured to support a substrate for exposure in an immersion lithography apparatus, wherein the substrate has a first contact angle with respect to immersion liquid, the substrate holder comprising a peripheral structure surrounding the substrate and being flush with the substrate when supported by the substrate holder, the structure comprising a surface structure and an electrode structure below the surface structure, the surface structure having a second contact angle with the immersion liquid, the first contact angle being different from the second contact angle, and the electrode structure configured to change the contact angle of a portion of the surface structure to smooth the transition from the first contact angle to the second contact angle, or vice versa, so as to stabilize a meniscus of immersion liquid moving along the surface structure towards or away from the substrate.

[0011]

[0011] According to the present invention, there is also provided a substrate support comprising a support block having an upper surface and a recess in the upper surface of the support block, and a substrate holder as described in any one of claims 1 to 4 that is accommodated in the recess so that its surface structure is flush with the upper surface of the support block, wherein an outer portion of the upper surface of the support block has a third contact angle with the immersion liquid, the third contact angle being smaller than the second contact angle, and a transition region of the upper surface of the support block between the outer portion and the recess has a transition contact angle between the second contact angle and the third contact angle.

[0012]

[0012] According to the present invention, there is also provided a lithographic apparatus including a substrate support.

[0013]

[0013] The present invention also provides a method for manufacturing a device using a substrate support.

[0014] 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]

[0015]

[0015] Some embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which like reference symbols indicate corresponding parts, and in which:

[0016]

[0015] [Figure 1] 1 shows a schematic overview of a lithographic apparatus; [Figure 2A] 1 illustrates, in cross-section, a portion of a substrate support, a substrate holder, and a substrate in one embodiment of the present invention. [Figure 2B] The contact angles at different positions are shown. [Figure 3] 10 shows a fluid handling structure traversing the edge of a substrate; [Figure 4A] The electrode structure is shown. [Figure 4B] The potentials generated by the electrode structure are shown. [Figure 5A] 1 shows an alternative electrode configuration. [Figure 5B] 4 shows the potentials generated by the alternative electrode structure. [Figure 6A] 1 shows an alternative electrode configuration. [Figure 6B] 4 shows the potentials generated by the alternative electrode structure. [Figure 7] 1 shows the stamp used to create the static contact angle gradient. [Figure 8A] 1 illustrates the operating principle of auxetic meshes. [Figure 8B] 1 illustrates the operating principle of auxetic meshes. [Figure 9A] 1 shows the effect of changes in the state of the auxetic mesh on the droplet. [Figure 9B] 1 shows the effect of changes in the state of the auxetic mesh on the droplet. [Figure 10] FIG. 1 is a more detailed diagram showing the cell structure of an exemplary auxetic mesh. [Figure 11] 11 is a graph of contact angle versus auxetic rotation angle for the auxetic mesh of FIG. 10. [Figure 12] Figure 1 illustrates, in cross-section, part of a fluid handling structure and part of a substrate support including an auxetic mesh;

[0017]

[0016] Features in the drawings are not necessarily drawn to scale, and the illustrated size and / or arrangement is not limiting. 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 are illustrated in each drawing, and a drawing may show only some of the components relevant to explain a particular feature. DETAILED DESCRIPTION OF THE INVENTION

[0018]

[0017] In this specification, the terms "radiation" and "beam" are used to encompass all types of electromagnetic radiation, including ultraviolet radiation (eg, having a wavelength of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm).

[0019]

[0018] As used herein, the terms "reticle," "mask," or "patterning device" may be broadly interpreted to refer to a general patterning device that can be used to impart a patterned cross section to an incident radiation beam, corresponding to the pattern to be created in a target portion of a substrate. The term "light valve" may also be used in this context. In addition to traditional masks (transmissive or reflective, binary, phase-shifting, hybrid, etc.), examples of other such patterning devices include programmable mirror arrays and programmable LCD arrays.

[0020] 1 schematically depicts a lithographic apparatus comprising: an illumination system (also called an illuminator) IL configured to condition a radiation beam B (e.g. violet UV radiation or DUV radiation), a mask support (e.g. a mask table) MT constructed to support a patterning device (e.g. a mask) MA and coupled to a first positioner PM configured to accurately position the patterning device MA according to certain parameters, a substrate support (e.g. a substrate table) WT constructed to hold a substrate (e.g. a resist-coated wafer) W and coupled 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) 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) of the substrate W.

[0021]

[0020] 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 is used to condition the radiation beam B so that it has a desired spatial and angular intensity distribution in its cross-section in the plane of the patterning device MA.

[0022]

[0021] 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 optics, or any combination thereof, as appropriate for the exposure radiation being 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 can be considered as synonymous with the more general term "projection system" PS.

[0023] The lithographic apparatus may be of a type in which at least a portion of the substrate W is covered by an immersion liquid having a relatively high refractive index (e.g. water) so as to fill an immersion space 11 between the projection system PS and the substrate W, also referred to as immersion lithography. More detailed information about immersion techniques is provided in U.S. Patent No. 6,952,253, which is incorporated herein by reference.

[0024] The lithographic apparatus may be of a type having two or more substrate supports WT (also referred to as "dual stage"). In such a "multi-stage" machine, the substrate supports WT can be used in parallel and / or preparation steps for a subsequent exposure of a substrate W can be performed on a substrate W arranged on one of the substrate supports WT, while a pattern on another substrate W is exposed using the other substrate support WT.

[0025] In addition to the substrate support WT, the lithographic apparatus may comprise a measurement stage (not shown in the drawings). The measurement stage is arranged to hold a sensor and / or a cleaning device. The sensor may be arranged to measure a property of the projection system PS or a property of the radiation beam B. The measurement stage may hold multiple sensors. The cleaning device may be arranged to clean part of the lithographic apparatus, for example part of the projection system PS or part of a system for supplying immersion liquid. The measurement stage may move below the projection system PS when the substrate support WT is moved away from the projection system PS.

[0026]

[0025] 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. After passing through the mask MA, the radiation beam B passes through the projection system PS, which focuses the beam onto a target portion C of the substrate W. Using the second positioner PW and the position measurement system IF, the substrate table WT can be accurately moved, for example to position different target portions C in the path of the radiation beam B at focused and aligned positions. Similarly, the patterning device MA can be accurately 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 Figure 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 as illustrated occupy dedicated target portions, the substrate alignment marks may 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.

[0027] 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 about the x-axis is called Rx-rotation. Rotation about the y-axis is called Ry-rotation. Rotation about the z-axis is called Rz-rotation. The x- and y-axes define a horizontal plane, while the z-axis is vertical. The Cartesian coordinate system is used for clarity purposes only and does not limit the invention. Instead of Cartesian coordinates, another coordinate system, such as a cylindrical coordinate system, may be used to clarify the invention. The Cartesian coordinate system may have a different orientation, for example, the z-axis has a component along the horizontal plane.

[0028] 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 inserted 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. That is, at least a portion of the substrate W undergoing exposure is immersed in the immersion liquid.

[0029] In commercial immersion lithography, the immersion liquid is water. Typically, this water is highly pure, distilled water, such as ultrapure water (UPW), commonly used in semiconductor manufacturing facilities. In immersion systems, the UPW is often purified and may undergo additional processing steps before being supplied to the immersion space 11 as the immersion liquid. In addition to water, other high refractive index liquids may be used as the immersion liquid, such as hydrocarbons, e.g., fluorocarbons, and / or aqueous solutions. Furthermore, other fluids in addition to liquids have been envisioned for use in immersion lithography. Desirably, the immersion liquid should not dissolve, swell, or adhere to the underlying photoresist.

[0030]

[0029] This specification will refer to localized immersion where the immersion liquid is confined, in use, to an immersion space 11 between the final element and a surface facing the final element. The facing surface may be the surface of the substrate W or a support stage (or substrate support W) that is flush with the surface of the substrate W. ). (Note that in the following description, when reference is made to the surface of the substrate W, reference is made to the surface of the substrate support WT in addition to or instead of the substrate W, and vice versa, unless expressly stated otherwise.) A fluid handling structure 12 present between the projection system PS and the substrate support WT is used to confine the immersion liquid to an immersion space 11. The immersion space 11, when filled with immersion liquid, is smaller in plan than the top surface of the substrate W, and the immersion space 11 remains substantially confined relative to the projection system PS while the substrate W and substrate support WT move underneath.

[0031] Other immersion systems have also been envisaged, such as unconfined immersion systems (so-called "all wet" immersion systems) and bath immersion systems. In an unconfined immersion system, the immersion liquid covers an area larger than the surface below the final element. The liquid outside the immersion space 11 is present as a thin film. The immersion liquid may cover the entire surface of the substrate W or may also cover the substrate W and the substrate support WT which is flush with the substrate W. In a bath system, the substrate W is completely immersed in a bath of immersion liquid.

[0032] 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. The fluid handling structure 12 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 a plurality of pipes that either supply immersion liquid to or remove 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 of the projection system PS and the substrate support WT or substrate W, to partly define the immersion space 11.

[0033] The fluid handling structure 12 may have a selection of different functions, each of which may result 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, each of which refers to a function such as a barrier member, a seal member, a fluid supply system, a fluid removal system, a fluid confinement system, etc.

[0034]

[0033] As immersion fluid an immersion liquid may be used. In that case the fluid handling structure 12 may be a liquid handling system. With reference to the above description, references in this paragraph to features defined with respect to a fluid can be understood to include features defined with respect to a liquid.

[0035] The lithographic apparatus has a projection system PS. During exposure of a substrate W, the projection system PS projects a patterned radiation beam 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 that is confined between the projection system PS and the substrate W by a fluid handling structure 12. The projection system PS has a lens element that is at the end of the path of the beam and in contact with the immersion liquid. This lens element in contact with the immersion liquid may be referred to as the "last lens element" or "final element". The final element is at least partly surrounded by a fluid handling structure 12. The fluid handling structure 12 may confine immersion liquid below the final element and above a facing surface.

[0036] As shown in Figure 1, the lithographic apparatus comprises a controller 500. The controller 500 is configured to control a substrate table WT.

[0037]

[0036] Figure 2A shows part of a substrate support for a lithographic apparatus according to the invention. The arrangement shown in Figure 2A and described below may be part of a substrate support WT and may be applied to the lithographic apparatus shown in Figure 1 and described above. Figure 2A shows a cross section through a substrate support 20 and a substrate W.

[0038] In one embodiment, the substrate support 20 comprises one or more conditioning channels (not shown) of a thermal conditioner. The substrate W is held by a support 21 (e.g. a pimple table or a burl table) comprising one or more burls (not shown). The support 21 is an example of an object holder. Another example of an object holder is a mask holder. A negative pressure applied between the substrate W and the substrate support 20 ensures that the substrate W is held firmly in place.

[0039] A gap 5 exists between the edge of the substrate W and the edge of the recess in the substrate support 20. The edge of the recess in the substrate support 20 may optionally be defined by a cover ring 101 that is spaced from the supports 21 of the substrate support 20. The cover ring 101 may be shaped as a ring in plan and surrounds the outer edge of the substrate W. When the edge of the substrate W is being imaged, or at other times, such as when the substrate W is initially moving under the projection system PS (as described above), the immersion space 11, which has been filled with liquid by the fluid handling structure 12, will pass at least partially over the gap 5 between the edge of the substrate W and the edge of the substrate support 20. This may allow liquid from the immersion space 11 to enter the gap 5.

[0040] If immersion liquid gets between the substrate W and the support 21, difficulties may arise, particularly when unloading the substrate W. To deal with immersion liquid entering the gap 5, a drain 10 is provided at the edge of the substrate W to remove the immersion liquid that enters the gap 5. In one embodiment, the drain 10 is annular so that it surrounds the entire periphery of the substrate W.

[0041] The main function of the drain 10 (radially outward from the edge of the substrate W) is to help prevent gas bubbles from entering the immersion space 11 where liquid of the fluid handling structure 12 is present. Such bubbles could adversely affect imaging of the substrate W. The drain 10 is present to help avoid gas in the gap 5 leaking into the immersion space 11 of the fluid handling structure 12. If gas leaks into the immersion space 11, it could cause bubbles to float in the immersion space 11. If such bubbles are in the path of the radiation beam B, imaging errors could occur. The drain 10 is configured to remove gas from the gap 5 between the edge of the substrate W and the edge of the recess in the substrate support 20 in which the substrate W is positioned. The drain 10 mainly removes gas and only small amounts of immersion liquid. However, at certain times the drain may also mainly remove liquid.

[0042] Optionally, an inner drain (at the edge of the substrate W and / or radially inward of the drain 10) may be provided, but is not shown. The inner drain may help to prevent liquid seeping under the substrate W from the gap 5 from interfering with efficient release of the substrate W from the substrate support 20 after imaging. The provision of an inner drain reduces or eliminates any problems that may arise due to liquid seeping under the substrate W.

[0043] 2A, the cover ring 101 has a top surface. The top surface extends circumferentially around the substrate W on the support 21. In use of the lithographic apparatus, the substrate support 20 moves relative to the fluid handling structure 12. During this relative movement, the fluid handling structure 12 moves across the gap 5 between the cover ring 101 and the substrate W. In an embodiment, the relative movement is caused by the substrate support 20 moving below the fluid handling structure 12. In an alternative embodiment, the relative movement is caused by the fluid handling structure 12 moving above the substrate support 20. In a further alternative embodiment, the relative movement is provided by both movement of the substrate support below the fluid handling structure 12 and movement of the fluid handling structure 12 above the substrate support 20. In the following description, movement of the fluid handling structure 12 is used to mean relative movement of the fluid handling structure 12 with respect to the substrate support 20.

[0044] The supports 21 include a plurality of burls (not shown). When the substrate W is supported by the supports 21, the substrate W comes into contact with the burls of the supports 21. The supports 21 are parts of the substrate support 20 that physically support the underside of the substrate W. The distal ends of the burls define a support plane on which the underside of the substrate W is supported. The underside of the substrate W comes into contact with the distal ends of the burls. The burls are on the upper surface of the supports 21.

[0045]

[0044] The material of the substrate support 20 is not particularly limited, and may be any suitable material known in the art. Preferably, the substrate support 20 may be made of siliconized silicon carbide (SiSiC).

[0046]

[0045] Fabrication of the substrate support 20 involves standard techniques known in the art. Some openings may be too small for methods such as electrical discharge machining (EDM). In this case, laser drilling may be used.

[0047] To form a pattern on the substrate W, the substrate W is covered with a photoresist PR. Different photoresists may be used in different situations. In some cases, a topcoat (not shown) may be provided on top of the photoresist PR. The material composition and surface structure of the top surface of the substrate W may therefore vary according to the patterning recipe being performed. This variation in the top surface of the substrate W may also cause the contact angle of the top surface with the immersion liquid (e.g., water) to vary from batch to batch. Common values ​​for the contact angle of the top surface of the substrate W with the immersion liquid are in the range of about 70° to about 110°. It should be noted that a large contact angle is desirable for the photoresist PR, as this allows for a higher relative velocity between the substrate W and the fluid handling structure 12 without significant loss of immersion liquid droplets or films. The outermost part of the substrate support 20 may be a polished siliconized silicon carbide (SiSiC) surface with a contact angle in the range of about 0° to about 30°.

[0048] It is known that instabilities in the meniscus 17 can be caused when the immersion liquid meniscus 17 undergoes a sudden transition in contact angle with the moving underlying surface. Such instabilities can lead to immersion liquid being left behind on the substrate W and / or bubbles being contained in the immersion liquid. In particular, a sudden increase in the contact angle has been found to cause pinning of the meniscus 17 and significant defects in substrates processed by the apparatus.

[0049] To reduce the sudden change in the contact angle, it is known to provide a surface coating or surface structure 102 on the cover ring 101. The surface structure 102 has a contact angle that is larger than the contact angle of the outer portion of the substrate support 20 and closer to the expected contact angle of the photoresist PR with the immersion liquid. Furthermore, a seal (or sticker) 24 provided to cover the gap between the cover ring 101 and the outer portion of the substrate support 20 is also configured to have a contact angle similar to the contact angle of the surface structure 102. A transition region 23 is provided on the outside of the seal 24 to provide a gradual or step-like transition in the contact angle between the outer region 22 of the substrate holder 20 and the seal 24. The transition region 23 may comprise a surface coating, seal (or sticker), or surface treatment as needed to provide a gradual or step-like transition in the contact angle.

[0050] While the transition region 23, seal 24, and surface structure 102 are effective in reducing immersion fluid loss from the meniscus 17 by providing a more gradual transition in contact angle, depending on the recipe being manufactured, a significant transition in contact angle may still occur between the surface structure 102 and the photoresist PR on the substrate W, as different recipes may have different contact angles for the photoresist PR. Therefore, further improvements are desirable.

[0051] In one embodiment of the present invention, an electrode structure 103 is provided in the cover ring 101 under the surface structure 102. The electrode structure 103 is connected to a potential source 106 to change the contact angle of the surface structure 102 by electrowetting. To avoid this, the surface structure 102 preferably has a large contact angle similar to that of the seal 24 (e.g., by having a hydrophobic coating such as PTFE). The contact angle of the surface structure 102 may be similar to or larger than the largest contact angle expected for the photoresist PR. When connected to the potential source 106, the electrode structure 103 generates an electric field in the vicinity of the surface structure 102 that is effective to change (e.g., decrease) the contact angle of the surface structure 102 with the immersion liquid. The potential applied to the electrode structure 103 may be determined depending on the contact angle of the photoresist PR in the recipe being executed. The contact angle of the photoresist PR may be known or estimated, for example through measurement, but in one embodiment, the potential applied to the electrode structure 103 is determined so that the contact angle of the surface structure 102 is closer to the contact angle of the photoresist PR than the contact angle would be if no potential were applied to the electrode structure 103.

[0052] The operation of the present invention is illustrated in FIG. 2B, which is a graph showing the change in contact angle on different surfaces of the structure of FIG. 2A. The achieved contact angle is shown by the solid line, while the natural contact angle of the unmodified surface is shown by the dashed line. The dotted area indicates the gap 5, where there is no contact angle. The contact angle of the outer region 22 of the substrate support 20 can be seen to have a relatively small contact angle CA3. The transition region 23 has a gradually increasing contact angle CAt. The seal 24 has a contact angle CA2 that is larger than the contact angle CA3 of the outer region 22. The contact angle CA2 of the seal 24 is preferably close to or within the range of expected values ​​for the contact angle of the photoresist PR. The contact angle CA2 can be, for example, in the range of 70° to 110°.

[0053] 2B shows that by setting different potentials for the electrode structure 103, the contact angle of the surface structure 102 can be set to an increasing contact angle CA2A that transitions towards a larger contact value CA1A of the photoresist PR. Alternatively, the contact angle of the surface structure 102 can be set to a decreasing contact angle CA2B that transitions towards a smaller contact angle CA1B of the photoresist PR. For intermediate values, the contact angle of the surface structure 102 can be increased or decreased to a larger or smaller value. Thus, whatever the value of the contact angle of the photoresist PR, a smooth and gradual transition can be configured, thereby minimizing the loss of immersion liquid.

[0054] Preferably, the electrode structure 103 is provided around the whole of the cover ring 101, i.e. surrounding the entire periphery of the substrate W. However, as shown in Figure 3, there are areas at the periphery of the substrate where the fluid handling structure 12 crosses the edge of the substrate W more frequently than elsewhere, and at an angle where the immersion liquid meniscus 17 is most likely to be unstable. Therefore, the electrode structure 103 may be provided only in areas of the periphery that are most susceptible to loss of immersion liquid.

[0055] The location of the area where immersion liquid loss is most likely to occur may vary depending, inter alia, on the serpentine pattern used in a given recipe for the relative movement of the substrate W and the projection system PS. Therefore, a controller 107 may be provided to control the potential applied to the electrode structure 103 by the potential source 106 according to the instantaneous position of the meniscus 17. The position of the meniscus 17 may be determined by reference to the known relative positions of the substrate W and the fluid handling structure 12. There may be a different effect when the leading part of the meniscus crosses the edge of the substrate W and the cover ring 101 compared to when the trailing part of the meniscus crosses the edge of the substrate W and the fluid handling structure 12. The applied potential may therefore vary between these two events. This may require potential changes on the time scale of 0.1 seconds, which is easily achievable. Since the contact angle may change when the photoresist PR is exposed, the controller 107 may be configured to set different potentials, resulting in different contact angle gradients, depending on whether the meniscus 17 is transitioning onto or off of exposed or unexposed photoresist PR.

[0056]

[0055] Figure 4A shows the electrode structure 103 in cross section, and Figure 4B shows the potentials that can be achieved. The electrode structure 103 comprises multiple electrodes 104, 105, which are alternately connected to either a positive potential (electrode 105) or a negative potential (electrode 104). The electrodes 104, 105 may be rings that completely surround the substrate W, or may be divided into multiple segments so that the potential applied to each segment can be controlled separately. As illustrated in Figure 4B, the structure shown in Figure 4A produces a potential VDC at the surface of the surface structure 102 that is substantially constant with radius. This configuration can be used in conjunction with a time-varying potential (as described above) to control the contact angle of the surface structure 102.

[0057] 5A shows an alternative configuration, which differs from that of FIG. 4A in that a resistor 108 connected to a positive power supply is provided between the electrodes 105. The potential drop across the resistor 108 when current flows along the positive rail creates a different potential at the electrodes 105. As shown in FIG. 5B, the structure shown in FIG. 5A has a potential V that varies with radius (e.g., decreases towards the center of the substrate) at the surface of the surface structure 102. DC , which causes the contact angle of the surface structure 102 to vary with radius. DC The variation of V may be stepped, but if the steps are small and numerous, it may be considered to be substantially continuous. DC The shape of the variation of is substantially fixed by the value of resistor 108.

[0058] 6A shows another alternative configuration, which differs from that of FIG. 4A in that each of the electrodes 105 is connected to an individually controllable potential output by the controller 107. The potentials set at the electrodes 105 can be used to establish any desired potential V DC A profile similar to that of FIG. 5B is shown in FIG. 6B, although other profiles are possible. DC The variation of may be in steps, but if the steps are small and numerous it may be considered to be substantially continuous. The concepts of Figures 5A and 6A may also be combined, for example, where individually controllable potentials are applied to groups of electrodes 105 connected by resistors 108.

[0059] 4A, 5A, and 6A show ten electrodes 104, 105, practical embodiments may have many more electrode rings, for example, more than 20 or even more than 50. The greater the number of electrodes 104, 105, the more gradual the transition in contact angle that can be achieved. The change in contact angle is preferably in steps of 5° or less, preferably in steps of 3° or less, and most preferably in steps of 1° or less. The width of the electrodes 104, 105 is preferably 100 μm or less, and preferably about 50 μm or less.

[0060] An alternative approach using only one or two electrodes 104, 105 is to dynamically adjust the potential applied to the electrode structure 103 as the meniscus 17 traverses the electrodes 104, 105. With this approach, although the contact angle may not be optimal along the entire length of the meniscus 17, the contact angle may be optimized for at least a portion of the meniscus 17, for example near a corner of the immersion space 11 where pulling of the liquid film is most likely to occur.

[0061] To obtain a desired contact angle on the seal (sticker) 24, a tailored coating can be used. The hydrophobicity of the coating can be adjusted by applying molecular entities that form self-assembled monolayers on the coating before oxidation. Typically, for hydrophobic surfaces, molecular species with Si-Cl3 end groups or Si-(O-CH3)3 graft groups that bond with hydroxyl groups on the substrate can be used. Since the end groups of the molecular species determine the SFE, contact angles of up to CA=120 and CA=110 can be achieved by using CF3 or CH3 end groups, respectively. Hydrophobicity can be varied by adding molecular species with more polar end group functionality.

[0062]

[0061] Varying amounts of molecular species may be deposited on the monolayer at different locations to obtain a gradually varying or graded contact angle in the transition region 23. Such a gradient can be obtained by different concentrations of molecular species at different locations, by deposition for different times at different locations, by deposition at locally varying temperatures that affect the amount of species, or by any combination of these approaches.

[0063] Another approach to providing locally varying contact angles utilizes microcontact printing, in which molecular species are printed locally, so that by using different mixtures or different concentrations in the stamp, different subregions within the transition region 23 can be printed with different species, resulting in a gradient. Figure 7 shows a stamp 201 having protrusions 202 that can be customized to deliver different "inks" or different amounts of ink at different locations to achieve the desired gradient. Gradients can also be achieved by varying numbers of overlapping printing steps.

[0064] In a further embodiment of the invention described below with reference to Figures 8A to 12, an auxetic mesh is used to control the contact angle of part of the surrounding structure. The contact angle is controlled through actuators (not shown) which exert a force on the auxetic mesh. Thus, the contact angle can be controlled depending on the direction and / or speed of movement of the substrate holder 20 as described above.

[0065] 8A shows a schematic of an example of an auxetic mesh 300. The auxetic mesh 300 comprises an array of bowtie elements 301 connected to each other to form rows. Adjacent bowtie elements 301 in the same row share a side. The rows are interconnected by ligaments 302 that connect narrow portions of the bowtie elements 301 between adjacent rows.

[0066] 8B shows the effect of applying tension to auxetic mesh 300 in a direction perpendicular to the rows of bowtie elements 301. As the rows move away from each other, the ligaments 302 connecting the narrow portions (i.e., waists) of bowtie elements 301 open up the narrow portions of bowtie elements 301, causing the bowtie elements 301 to expand in the direction of the rows. The auxetic mesh 300 then exhibits a negative Poisson's ratio. That is, whereas a conventional elastic material would contract in a direction perpendicular to the applied tension, the auxetic mesh 300 expands in a direction perpendicular to the applied tension. It will be appreciated that the auxetic mesh 300 exhibits a negative Poisson's ratio both when the applied tension is directed parallel to the rows of bowtie elements 301 and when a compressive force is applied instead of a tension force.

[0067]

[0066] Figures 9A and 9B show schematically that droplets (e.g., water droplets) 306 may reside on the surface of the auxetic mesh 300 (Figure 9A) or may penetrate the auxetic mesh 300 (Figure 9B).

[0068] 10 shows a perspective view of a unit cell (i.e., bowtie element 301) of auxetic mesh 300. Bowtie element 301 has a concave hexagonal shape formed by two parallel long sides joined by four short sides 311. The four short sides 311 form two concave surfaces. Ligaments 302 are connected between the two short sides 311. The shape of bowtie element 301 can be characterized by the auxetic rotation angle α, which is the angle between the short side 311 and the normal to the long side 310.

[0069]

[0068] When tension is applied to the lattice, the angle α changes. Assuming the edge members of the auxetic mesh 300 are substantially rigid, it will naturally follow that when a force is applied to the auxetic mesh 300 such that it expands or contracts, the void ratio or open area of ​​each cell will change. It will naturally follow that the surface area occupied by the edge members that make up the auxetic mesh 300 does not change significantly, so the porosity is most sensitive to changes in the shape of the mesh. A change in the porosity of the mesh will change the wettability that the mesh offers to a droplet or puddle of liquid resting or moving on its surface.

[0070] 11, which is a phase diagram illustrating whether a droplet 306 having a particular contact angle on a flat surface will stagnate or fully penetrate into a membrane (e.g., auxetic mesh 300), an initially hydrophobic auxetic mesh 300 will become more and then less hydrophobic as it is expanded until the auxetic rotation angle α reaches 0. Thus, a controller (not shown) may be provided to control the actuators to soften the transition from the first contact angle to the second contact angle, or vice versa, so as to stabilize the meniscus of a droplet moving along the surface structure towards the substrate W or vice versa.

[0071] Figure 12 is a view similar to Figure 2A and shows an auxetic mesh 300 provided on the top surface of a cover ring 101 that surrounds the substrate W when the substrate W is held on supports 21. Other elements shown in Figure 12 are similar to those shown in Figure 2A and, for the sake of brevity, will not be described further below. The auxetic mesh 300 may be provided as a complete ring surrounding the substrate W, or as a number of separate parts or segments that are selectively actuable so that the effective hydrophobicity of the covering ring 101 can be individually controlled in different regions. It will be appreciated that the space available for actuators near the substrate W is limited. Thus, one edge of the auxetic mesh 300, for example the edge adjacent the inner periphery of the covering ring 101, may be fixed to the covering ring 101, for example, and an actuator (not shown) may be connected to the other edge, for example the outer periphery.

[0072] The actuators may be remote and connected to the auxetic mesh 300 by mechanical elements. Actuators, for example piezo elements, may be integrated into the auxetic mesh 300. The actuators may be electrically driven (e.g. solenoids or piezo actuators), hydraulic or pneumatic. There may be multiple actuators which may be equally spaced around the periphery of the auxetic mesh 300, or multiple actuators which are concentrated in the main directions of movement of the substrate W during exposure (e.g. to exert forces in the X and Y directions).

[0073]

[0072] If the auxetic mesh 300 is annular or arc-shaped, the bowtie elements 301 may be arranged so that the rows are radial or circumferential rather than linear.

[0074] The present invention may provide a lithographic apparatus, which may have any / all of the other features or components of the lithographic apparatus as described above. For example, the lithographic apparatus may optionally comprise at least one or more of a radiation source SO, an illumination system IL, a projection system PS, a substrate table WT, etc.

[0075] In particular, the lithographic apparatus may comprise a projection system PS configured to project a radiation beam B towards a region of a surface of a substrate W. The lithographic apparatus may further comprise a substrate support 20 as described in any of the embodiments and variants described above.

[0076]

[0075] Although specific reference is made in this specification to the use of lithographic apparatus in IC manufacturing, it should be understood that the lithographic apparatus described herein may have other applications. Other contemplated applications include 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.

[0077]

[0076] Where circumstances permit, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented by instructions stored on a machine-readable medium that can 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 disk storage media, optical storage media, flash memory devices, or electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.). Also, firmware, software, routines, or instructions may be described herein as performing certain actions. However, it should be understood that such description is for convenience only, and that such actions are in fact due to a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc., thereby causing actuators or other devices to interact with the physical world.

[0078] Although specific reference has been made herein to embodiments of the invention in relation to lithographic apparatus, embodiments of the invention can also 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 generally be referred to as lithography tools.

[0079]

[0078] Although specific reference has been made above to the use of embodiments of the present invention in the context of optical lithography, it will be appreciated that the present invention is not limited to optical lithography, where circumstances permit.

[0080]

[0079] Embodiments of the present invention are described in the numbered clauses below. 1. A substrate holder configured to support a substrate for exposure in an immersion lithography apparatus, the substrate having a first contact angle with an immersion liquid, the substrate holder comprising a peripheral structure surrounding the substrate and coplanar with the substrate when supported by the substrate holder, the structure comprising a surface structure and an electrode structure below the surface structure, the surface structure having a second contact angle with the immersion liquid, the first contact angle being different from the second contact angle, the electrode structure configured to modify the contact angle of a portion of the surface structure to make the transition from the first contact angle to the second contact angle, or vice versa, gradual so as to stabilize a meniscus of immersion liquid moving along the surface structure towards or away from the substrate. 2. The substrate holder of clause 1, wherein the electrode structure comprises a plurality of electrodes. 3. The substrate holder of clause 2, wherein the plurality of electrodes comprises a plurality of concentric ring electrodes. 4. The substrate holder of clause 2 or 3, further comprising a potential source configured to apply a potential gradient across the plurality of electrodes. 5. A substrate holder according to any of clauses 1 to 4, further comprising a controller configured to control the potential applied to the electrode structure based on the position of the meniscus. 6. A substrate holder according to clause 5, wherein the controller is configured to control the electrical potential based on the position of the substrate holder relative to the fluid handling structure. 7. The substrate holder according to any one of clauses 1 to 6, wherein the second contact angle when no potential is applied is in the range of 70° to 100°. 8. A substrate support comprising: a support block having a support block top surface and a recess in the support block top surface; and a substrate holder according to any of clauses 1 to 7 received in the recess so that the surface structure is flush with the support block top surface, wherein an outer portion of the support block top surface has a third contact angle with the immersion liquid, the third contact angle being smaller than the second contact angle, and a transition region of the support block top surface between the outer portion and the recess has a transition contact angle between the second contact angle and the third contact angle. 9. The substrate support of clause 8, wherein the transition region has a gradually varying contact angle. 10. The substrate support of clause 8, wherein the transition region has a graduated contact angle. 11. The substrate support of clause 8, 9 or 10, wherein the transition region has a hydrophobic coating. 12. The substrate support of clause 11, wherein the hydrophobic coating has a varying composition. 13. The substrate support of clause 12, wherein the hydrophobic coating comprises a plurality of molecular species having different end groups. 14. The substrate support of clause 13, wherein the terminal groups include CF3 and CH3. 15. The substrate support of clause 13 or 14, wherein the hydrophobic coating has different concentrations of a plurality of molecular species at different locations. 16. A lithographic apparatus comprising a substrate support according to any one of clauses 8 to 15. 17. A method for manufacturing a device using a substrate support according to any one of clauses 8 to 15. 18. A substrate holder configured to support a substrate for exposure in an immersion lithography apparatus, the substrate having a first contact angle with respect to immersion liquid, the substrate holder comprising a surrounding structure that surrounds and is coplanar with the substrate when supported by the substrate holder, the surrounding structure comprising an auxetic mesh and an actuator system configured to apply a force to the auxetic mesh; the surface structure has a second contact angle with the immersion liquid; the auxetic mesh is configured such that the second contact angle of at least a portion thereof changes in response to a force applied by the actuator system; Substrate holder. 19. A substrate holder as described in clause 18, further comprising a controller that controls the actuator to soften the transition from the first contact angle to the second contact angle, or vice versa, so as to stabilize a meniscus of immersion liquid moving along the surface structure towards or away from the substrate. 20. The substrate holder of clause 18 or 19, wherein the actuator is configured to apply a force in the plane of the auxetic mesh. 21. A substrate holder according to clause 18 or 19, wherein the mesh is configured such that the size of the voids in the mesh are changed by the application of force by the actuator.

[0081]

[0080] While specific embodiments of the present invention have been described above, it will be appreciated that the present invention may be embodied in other ways. The foregoing description is intended to be illustrative rather than limiting. Thus, it will be apparent to those skilled in the art that modifications may be made to the present invention as described above without departing from the scope of the following claims.

Claims

1. 1. A substrate holder configured to support a substrate for exposure in an immersion lithography apparatus, the substrate having a first contact angle with respect to an immersion liquid, the substrate holder comprising: a peripheral structure surrounding the substrate and coplanar with the substrate when supported by the substrate holder, the peripheral structure comprising a surface structure and an electrode structure below the surface structure; the surface structure has a second contact angle with the immersion liquid, the first contact angle being different from the second contact angle; the electrode structure is configured to modify a contact angle of a portion of the surface structure to soften a transition from the first contact angle to the second contact angle, or vice versa, so as to stabilize a meniscus of the immersion liquid moving along the surface structure towards or away from the substrate; Substrate holder.

2. 10. The substrate holder of claim 1, wherein the electrode structure comprises a plurality of electrodes, preferably the plurality of electrodes comprises a plurality of concentric ring electrodes, and / or further comprises a potential source that applies a potential gradient across the plurality of electrodes.

3. 3. A substrate holder according to claim 1, further comprising a controller configured to control the potential applied to the electrode structure based on the position of the meniscus, desirably the controller configured to control the potential based on the position of the substrate holder relative to a fluid handling structure.

4. 4. The substrate holder according to claim 1, wherein the second contact angle when no potential is applied is in the range of 70° to 100°.

5. a support block having a support block top surface and a recess in the support block top surface; a substrate holder according to any one of claims 1 to 4, which is accommodated in the recess so that the surface structure is flush with an upper surface of the support block; a substrate support, wherein an outer portion of the support block top surface has a third contact angle with the immersion liquid, the third contact angle being smaller than the second contact angle, and a transition region of the support block top surface between the outer portion and the recess has a transition contact angle between the second contact angle and the third contact angle.

6. The substrate support of claim 5 , wherein the transition region has a gradually varying contact angle, or the transition region has a stepped contact angle.

7. The substrate support according to claim 5 or 6, wherein the transition area comprises a hydrophobic coating.

8. The hydrophobic coating has a varying composition, preferably the hydrophobic coating comprises a plurality of molecular species having different end groups, preferably the end groups are CF ３ and CH ３ The substrate support of claim 7 , comprising:

9. The substrate support of claim 8 , wherein the hydrophobic coating has different concentrations of the plurality of molecular species at different locations.

10. 1. A substrate holder configured to support a substrate for exposure in an immersion lithography apparatus, the substrate having a first contact angle with respect to an immersion liquid, the substrate holder comprising: a surrounding structure surrounding and coplanar with the substrate when supported by the substrate holder, the surrounding structure comprising an auxetic mesh and an actuator system configured to apply a force to the auxetic mesh; the surface structure has a second contact angle with the immersion liquid; the auxetic mesh is configured such that the second contact angle of at least a portion thereof changes in response to a force applied by the actuator system. Substrate holder.

11. 11. The substrate holder of claim 10, further comprising a controller that controls the actuator to soften a transition from the first contact angle to the second contact angle, or vice versa, so as to stabilize a meniscus of the immersion liquid moving along the surface structure towards or away from the substrate.

12. 12. A substrate holder according to claim 10 or 11, wherein the actuator is configured to apply a force in the plane of the auxetic mesh.

13. 12. A substrate holder according to claim 10 or 11, wherein the mesh is configured such that the size of voids in the mesh is changed by the application of force by the actuator.

14. A lithographic apparatus comprising a substrate support according to any one of claims 5 to 9 or a substrate holder according to any one of claims 10 to 13.

15. A method for manufacturing a device, using the substrate support according to any one of claims 5 to 9 or the substrate holder according to any one of claims 10 to 13.

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