Lithography apparatus, method for unloading a substrate, and method for loading a substrate

Abstract

To improve the flatness of the clamped substrate and / or reduce wear on the support table. [Solution] A method for unloading a substrate from a support table configured to support the substrate, the method comprising supplying gas to the gap between the base surface of the support table and the substrate through a plurality of gas flow openings in the support table, wherein in the initial stage of unloading, the gas is supplied from at least one gas flow opening in the outer region of the support table and not from a gas flow opening in the central region of the support table located radially inward from the outer region, and in the later stage of unloading, the gas is supplied from at least one gas flow opening in the outer region and at least one gas flow opening in the central region.

Description

Technical Field

[0001] Cross-reference to related applications

[0001] This document claims the priority of European Patent Application No. 16154599.1 filed on February 8, 2016 and European Patent Application No. 16172678.1 filed on June 2, 2016, and the entire contents thereof are incorporated herein by reference.

[0002]

[0002] The present invention relates to a lithographic apparatus, a method of unloading a substrate, and a method of loading a substrate, particularly onto a support table of a lithographic apparatus.

Background Art

[0003]

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such a case, a patterning device, also alternatively called a mask or a reticle, can be used to generate the circuit pattern to be formed on the individual layers of the IC. This pattern can be transferred onto a target portion (e.g., including a part of one or several dies) on a substrate (e.g., a silicon wafer). The transfer of the pattern is usually performed by imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. Generally, one substrate includes a network of adjacent target portions onto which patterns are sequentially imparted. Conventional lithographic apparatuses include so-called steppers in which each target portion is irradiated by exposing the entire pattern onto the target portion at once, and scanners in which the pattern is scanned with a radiation beam in a given direction (the "scan" direction) while the substrate is scanned synchronously parallel or antiparallel to a given direction (the "scan" direction), so that each target portion is irradiated. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate.

[0004]

[0004] It has been proposed to immerse the substrate in the lithography projection apparatus in a liquid having a relatively high refractive index, such as water, to fill the space between the final element of the projection system and the substrate. In some embodiments, the liquid is ultrapure water, but other liquids may be used. Embodiments of the present invention have been described in terms of liquids. However, other fluids, in particular wetting fluids, incompressible fluids and / or fluids with a refractive index higher than air, preferably higher than water, may also be suitable. Fluids other than gases are particularly preferred. The point is that the exposure radiation has a shorter wavelength in the liquid, which allows for miniaturization of the features to be imaged. (The effect of the liquid can also be seen as being able to increase the effective numerical aperture (NA) of the system and increase the depth of focus.) Other immersion liquids have also been proposed, such as water in which solid particles (e.g., quartz) are suspended, or liquids in which nanoparticles (e.g., particles with a maximum size of up to 10 nm) are suspended. The suspended particles may or may not have the same refractive index as the liquid in which they are suspended. Other liquids that may be suitable are hydrocarbons such as aromatics, fluorohydrocarbons, and / or aqueous solutions.

[0005]

[0005] Immersing the substrate or the substrate and support table in a bath of liquid (see, for example, U.S. Patent No. 4,509,852) also means that there is a large mass of liquid that needs to be accelerated during scan exposure. This requires an additional motor or a more powerful motor, and turbulence in the liquid can cause undesirable and unpredictable effects.

[0006]

[0006] In an immersion apparatus, the immersion fluid is handled by a fluid handling system, device structure, or apparatus. In some embodiments, the fluid handling system can supply the immersion fluid and is therefore a fluid supply system. In some embodiments, the fluid handling system can at least partially contain the immersion fluid and is therefore a fluid containment system. In some embodiments, the fluid handling system can form a barrier to the fluid and is therefore a barrier member, such as a fluid containment structure. In some embodiments, the fluid handling system can generate or use a gas flow to help control, for example, the flow and / or position of the immersion fluid. The gas flow can form a seal that contains the immersion fluid and is therefore a fluid handling structure that can also be called a sealant. Such a sealant may be a fluid containment structure. In some embodiments, the immersion liquid is used as the immersion fluid. In this case, the fluid handling system may be a liquid handling system. With respect to the above description, references to features defined in this paragraph with respect to fluids may be considered to include features defined with respect to liquids. [Overview of the Initiative]

[0007]

[0007] In both immersion and dry exposure apparatuses, the substrate is clamped to a support table during the exposure process. Clamping may be assisted by the presence of a gap between the substrate and the support table at a pressure lower than the ambient pressure. Ambient pressure is the pressure surrounding the substrate and the support table. The area enclosed by the support table and the substrate may be at a near-vacuum pressure such that the substrate is vacuum-clamped to the support table.

[0008]

[0008] The support table includes one or more holes formed therein. The holes facilitate clamping of the substrate. Gas can be extracted through the holes from the gap surrounded by the substrate and the support table, thereby reducing the pressure in this gap to clamp the substrate.

[0009]

[0009] The substrate is loaded onto the support table. During loading, the substrate may deform due to gravity. The substrate is clamped in a deformed state, which may increase the overlay.

[0010]

[0010] The substrate has areas where near-vacuum pressure is applied during unloading and areas where it is not applied. A is possible. When near-vacuum pressure is not applied (e.g., released), the substrate can move away from the support table. In other areas where near-vacuum pressure is still applied, the substrate may slide. This can cause wear on the support table where the substrate slides. The periphery of the upper surface of the support table is particularly prone to wear.

[0011]

[0010] For example, it is desirable to provide a lithography apparatus, a method for unloading a substrate, and a method for loading a substrate that improve the flatness of the clamped substrate and / or reduce wear on the support table.

[0012]

[0011] According to one aspect of the present invention, a method is provided for unloading a substrate from a support table configured to support the substrate, the method comprising supplying gas to the gap between the base surface of the support table and the substrate through a plurality of gas flow openings of the support table, wherein in an initial stage of unloading, the gas is supplied from at least one gas flow opening in the outer region of the support table and not from a gas flow opening in the central region of the support table located radially inward from the outer region, and in a later stage of unloading, the gas is supplied from at least one gas flow opening in the outer region and at least one gas flow opening in the central region.

[0013]

[0012] According to one aspect of the present invention, a method is provided for loading a substrate onto a support table configured to support the substrate, the method comprising extracting gas from a gap between the base surface of the support table and the substrate through a plurality of gas flow openings in the support table, wherein in a first stage of loading, the gas extraction is performed from at least one gas flow opening in the central region of the support table, but not from gas flow openings in the intermediate region of the support table radially outside the central region and gas flow openings in the outer region of the support table radially outside the intermediate region; in a second stage of loading, the gas extraction is performed from at least one gas flow opening in the central region and at least one gas flow opening in the intermediate region, but not from gas flow openings in the outer region; and in a third stage of loading, the gas extraction is performed from at least one gas flow opening in the central region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the outer region.

[0014]

[0013] According to one aspect of the present invention, a method is provided for loading a substrate onto a support table configured to support the substrate, the method comprising: lowering the substrate toward the support table; controlling a negative pressure source to apply negative pressure to extract gas from the gap between the base surface of the support table and the substrate through a plurality of gas flow openings in the support table as the substrate is lowered toward the support table; stopping the application of negative pressure to the negative pressure source, which is in fluid communication with one of the gas flow openings in the support table, when the substrate has reached a predetermined distance above the support table; and restarting the application of negative pressure to the negative pressure source to extract gas through a plurality of gas flow openings in the support table when the substrate has landed on the support table.

[0015]

[0014] According to one aspect of the present invention, a method is provided for loading a substrate onto a support table configured to support the substrate, the method comprising extracting gas from a gap between the base surface of the support table and the substrate through a plurality of gas flow openings in the support table, wherein in a first stage of loading, the gas extraction is performed from at least one gas flow opening in the outer region of the support table, but not from a gas flow opening in the intermediate region of the support table radially inward from the outer region and a gas flow opening in the central region of the support table radially inward from the intermediate region; in a second stage of loading, the gas extraction is performed from at least one gas flow opening in the outer region and at least one gas flow opening in the intermediate region, but not from a gas flow opening in the central region; and in a third stage of loading, the gas extraction is performed from at least one gas flow opening in the outer region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the central region.

[0016]

[0015] According to one aspect of the present invention, a lithography apparatus is provided comprising a gas flow system, a controller configured to control the gas flow system, and a support table configured to support a substrate, wherein the support table comprises a base surface, a central region, an outer region radially outside the central region, and a plurality of gas flow openings configured for use by the gas flow system to supply gas to the gap between the base surface and the substrate, wherein, when the substrate is unloaded from the support table, in the initial stage of unloading, the controller is configured to control the gas flow system so that gas is supplied from at least one gas flow opening in the outer region and not from the gas flow opening in the central region, and in the later stage of unloading, the controller is configured to control the gas flow system so that gas is supplied from at least one gas flow opening in the outer region and at least one gas flow opening in the central region.

[0017]

[0016] According to one aspect of the present invention, a lithography apparatus comprising a gas flow system, a controller configured to control the gas flow system, and a support table configured to support a substrate, wherein the support table comprises a base surface, a central region, an intermediate region radially outside the central region, an outer region radially outside the intermediate region, and a plurality of gas flow openings configured for the gas flow system to extract gas from a gap between the base surface and the substrate, and when the substrate is loaded onto the support table, in a first stage of loading, the controller extracts gas from at least one gas flow opening in the central region and the intermediate region A lithography apparatus is provided, configured to control the gas flow system so that gas extraction is not performed from gas flow openings and gas flow openings in the outer region, and in a second stage of loading, the controller is configured to control the gas flow system so that gas extraction is performed from at least one gas flow opening in the central region and at least one gas flow opening in the intermediate region, but not from gas flow openings in the outer region, and in a third stage of loading, the controller is configured to control the gas flow system so that gas extraction is performed from at least one gas flow opening in the central region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the outer region.

[0018]

[0017] According to one aspect of the present invention, a lithography apparatus is provided comprising: a gas flow system with a negative pressure source; a controller configured to control the gas flow system; and a support table configured to support a substrate, wherein the controller is configured to control the negative pressure source to apply negative pressure in order to extract gas from the gap between the support table and the substrate through a plurality of gas flow openings in the support table when the substrate is lowered toward the support table; the controller is configured to stop controlling the negative pressure source, which is in fluid communication with one of the gas flow openings in the support table, to apply negative pressure when the substrate has reached a predetermined distance above the support table; and the controller is configured to restart controlling the negative pressure source to apply negative pressure in order to extract gas through a plurality of gas flow openings in the support table when the substrate has landed on the support table.

[0019]

[0018] According to one aspect of the present invention, a lithography apparatus is provided comprising a gas flow system, a controller configured to control the gas flow system, and a support table configured to support a substrate, wherein the support table comprises a base surface, a central region, an intermediate region radially outside the central region, an outer region radially outside the intermediate region, and a plurality of gas flow openings configured for use by the gas flow system to extract gas from a gap between the base surface and the substrate, each region being provided with a flow path that fluidly communicates with the gas flow opening in that region and a pressure sensor configured to sense the pressure in that region, and the lithography apparatus is provided configured such that when a substrate is loaded onto the support table, the controller controls the timing of gas extraction from the gas flow opening in each region based on the sensed pressure in each region. [Brief explanation of the drawing]

[0020]

[0019] Embodiments of the present invention will be described below with reference to the attached schematic diagrams in which the corresponding reference numerals indicate the corresponding parts, but these are merely illustrative examples.

[0021] [Figure 1]

[0020] Shows a lithography apparatus according to an embodiment of the present invention. [Figure 2]

[0021] Shows a liquid supply system used in a lithography projection apparatus. [Figure 3]

[0022] It is a side sectional view showing another liquid supply system according to an embodiment. [Figure 4]

[0023] The support table of the lithography apparatus according to an embodiment of the present invention is shown in a sectional view. [Figure 5]

[0024] The support table of the lithography apparatus according to an embodiment of the present invention is shown in a plan view. [Figure 6]

[0025] The support table of the lithography apparatus according to another embodiment of the present invention is shown in a plan view. [Figure 7]

[0026] The support table and a part of the gas flow system of the lithography apparatus according to an embodiment of the present invention are schematically shown. [Figure 8]

[0027] The support table and the gas flow system of the lithography apparatus according to an embodiment of the present invention are schematically shown. [Figure 9]

[0028] The support table and the gas flow system of the lithography apparatus according to an embodiment of the present invention are schematically shown. [Figure 10]

[0029] Shows the vertical height of the substrate over time when the substrate is lowered onto the support table. [Figure 11]

[0030] Shows the pressures of different parts of the lithography apparatus when the substrate is lowered onto the support table. [Figure 12]

[0031] Schematically shows the state of lowering the substrate according to an embodiment of the present invention onto the support table. [Figure 13]

[0032] The support table of the lithography apparatus according to an embodiment of the present invention is shown in a plan view. [Modes for carrying out the invention]

[0022]

[0033] Figure 1 schematically shows a lithography apparatus according to one embodiment of the present invention. This apparatus is a. A lighting system (illuminator) IL configured to adjust the radiation beam B (e.g., UV radiation or DUV radiation), b. A support structure (e.g., mask table) MT connected to a first positioner PM, which is constructed to support a patterning device (e.g., mask) MA and configured to precisely position the patterning device MA according to certain parameters, c. A support table, for example, a sensor table for supporting one or more sensors, or a support table WT, constructed to hold a substrate (e.g., a resist-coated substrate) W and connected to a second positioner PW configured to precisely position the surface of the substrate W according to certain parameters, d. A projection system (e.g., a refractive projection lens system) PS configured to project a pattern applied to a radiation beam B by a patterning device MA onto a target portion C of a substrate W (e.g., including one or more dies).

[0023]

[0034] The illumination system IL may include various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, or other types of optical components, or any combination thereof, for inducing, shaping, or controlling radiation.

[0024]

[0035] The support structure MT holds the patterning device MA. The support structure MT holds the patterning device in a manner that depends on the orientation of the patterning device MA, the design of the lithography apparatus, and other conditions, such as whether the patterning device MA is held in a vacuum environment. The support structure MT can use mechanical, vacuum, electrostatic, or other clamping techniques to hold the patterning device MA. The support structure MT may be, for example, a frame or a table, and may be fixed or movable as needed. The support structure MT can ensure that the patterning device MA is reliably positioned relative to, for example, a projection system PS. Where the terms “reticle” or “mask” are used herein, these terms can be considered synonymous with the more general term “patterning device.”

[0025]

[0036] As used herein, the term “patterning device” should be interpreted broadly to refer to any device that can be used to impart a pattern to a cross-section of a radiation beam in order to generate a pattern on a target portion of a substrate. It should be noted that the pattern imparted to the radiation beam may not precisely correspond to the desired pattern on the target portion of the substrate, for example, if the pattern includes phase-shift features or so-called assist features. Generally, the pattern imparted to the radiation beam corresponds to a specific functional layer of a device, such as an integrated circuit, that is generated on the target portion.

[0026]

[0037] As used herein, the term “projection system” should be interpreted broadly to encompass any type of projection system, including, for example, refractive optical systems, reflective optical systems, reflector-refractor optical systems, magneto-optical systems, electromagnetic optical systems, and electrostatic optical systems, or any combination thereof, depending on the exposure radiation used or other factors such as the use of immersion liquid or vacuum. Where the term “projection lens” is used herein, it can be considered synonymous with the more general term “projection system.”

[0027]

[0038] As described herein, the device is of the transmissive type (e.g., using a transmissive mask). Alternatively, the device may be of the reflective type (e.g., using a programmable mirror array of the type mentioned above, or using a reflective mask).

[0028]

[0039] A lithography apparatus may be of the type having two or more tables (or stages or supports), for example, two or more support tables, or a combination of one or more support tables and one or more cleaning, sensor, or measurement tables. For example, in one embodiment, the lithography apparatus is a multi-stage apparatus including two or more tables positioned on the exposure side of a projection system, each table containing and / or holding one or more objects. In one embodiment, one or more tables may hold a radiation-sensitive substrate. In one embodiment, one or more tables may hold sensors for measuring radiation from the projection system. In one embodiment, the multi-stage apparatus comprises a first table (i.e., a support table) configured to hold a radiation-sensitive substrate and a second table (hereinafter collectively referred to as a measurement, sensor, and / or cleaning table, but not limited to these) not configured to hold a radiation-sensitive substrate. The second table may contain and / or hold one or more objects other than the radiation-sensitive substrate. Such one or more objects may include one or more selected from: a sensor for measuring radiation from a projection system, one or more alignment marks, and / or a cleaning device (e.g., for cleaning a liquid-contained structure).

[0029]

[0040] In such a “multiple-stage” (or “multi-stage”) machine, multiple tables can be used in combination, or one or more tables can be used for exposure while preliminary processes are performed on one or more tables. The lithography apparatus may have two or more patterning device tables (or stages or supports) that can be used in combination in the same manner as the substrate, cleaning, sensor and / or measurement table.

[0030]

[0041] Referring to Figure 1, the illumination system IL receives a radiant beam from the radiation source SO or radiation. The radiation source SO and the lithography apparatus may be separate components, for example, when the radiation source SO is an excimer laser. In such cases, the radiation source SO is not considered to form part of the lithography apparatus, and the radiant beam is delivered from the radiation source SO to the illumination system IL with the help of a beam delivery system BD, which includes, for example, appropriate guide mirrors and / or beam expanders. In other cases, for example, when the radiation source SO is a mercury lamp, the radiation source SO may be an integral part of the lithography apparatus. The radiation source SO and the illumination system IL may, if necessary, be called a radiation system together with the beam delivery system BD.

[0031]

[0042] The illumination system IL may include an adjuster AD for adjusting the angular intensity distribution of the radiated beam. Generally, the outer and / or inner radial ranges of the intensity distribution at the pupil plane of the illumination system IL (generally referred to as σ-outer and σ-inner, respectively) can be adjusted. The illumination system IL may also include various other components such as an integrator IN and a capacitor CO. The radiated beam may be tuned using the illumination system IL to obtain desired uniformity and intensity distribution across its cross-section. Similar to the radiation source SO, the illumination system IL may or may not be considered as part of the lithography apparatus. For example, the illumination system IL may be an integrated part of the lithography apparatus, or it may be a separate component. In the latter case, the lithography apparatus may be configured to mount the illumination system IL on it. Optionally, the illumination system IL may be detachable and provided separately (e.g., by the manufacturer of the lithography apparatus or another supplier).

[0032]

[0043] The radiant beam B is incident on a patterning device MA held on a support structure MT, and a pattern is formed by the patterning device MA. After crossing the patterning device MA, the radiant beam B passes through a projection system PS, which focuses the beam onto a target portion C on the substrate W. With the help of a second positioner PW and a position sensor IF (e.g., an interferometer device, a linear encoder, or a capacitive sensor), the substrate table WT can be precisely moved to position, for example, various target portions C along the path of the radiant beam B. Similarly, using a first positioner PM and another position sensor (not shown in Figure 1), the patterning device MA can be precisely positioned relative to the path of the radiant beam B after mechanical removal from the mask library or during scanning. In general, the movement of the support structure MT can be achieved with the help of long-stroke modules (coarse positioning) and short-stroke modules (fine positioning) that form part of the first positioner PM. Similarly, the movement of the substrate table WT can be achieved using long-stroke modules and short-stroke modules that form part of the second positioner PW. In the case of a stepper (as opposed to a scanner), the support structure MT may be connected only to or fixed to the short-stroke actuator. The patterning device MA and the substrate W can be aligned using patterning device alignment marks M1, M2 and substrate alignment marks P1, P2. The patterning device alignment marks M1, M2, as shown in the figure, occupy dedicated target areas, but may also be located in the space between the target areas (known as scribe line alignment marks). Similarly, in situations where multiple dies are provided on the patterning device MA, the patterning device alignment marks may be placed between the dies.

[0033]

[0044] While this text specifically refers to the use of lithography equipment in IC manufacturing, it should be understood that the lithography equipment described herein may have other applications in the manufacture of components with microscale and even nanoscale features, such as integrated optical systems, induction and detection patterns for magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), and thin-film magnetic heads.

[0034]

[0045] Configurations for providing liquid between the final element of the projection system PS and the substrate can be classified into three general categories: bath configurations, so-called local immersion systems, and all-wet immersion systems. In bath configurations, substantially the entire substrate W and optionally a portion of the support table WT are submerged in a liquid bath.

[0035]

[0046] A localized immersion system uses a liquid supply system that delivers liquid only to a localized area of ​​the substrate. The space filled with liquid is smaller than the top surface of the substrate in plan view, and the area filled with liquid remains substantially stationary relative to the projection system PS, while the substrate W moves below that area. Figures 2 and 3 show different supply devices that can be used in such a system. A sealing feature exists to seal the liquid in the localized area. One method proposed for constructing this is disclosed in PCT Patent Application Publication WO99 / 49504.

[0036]

[0047] The proposed configuration provides the liquid supply system with a liquid containment structure that extends along at least a portion of the spatial boundary between the final element of the projection system and the support table. Such a configuration is shown in Figure 2.

[0037]

[0048] Figure 2 schematically illustrates a local fluid supply system, i.e., a fluid handling system. The fluid supply system comprises a fluid handling structure IH (or fluid containment structure) extending along at least a portion of the boundary of the space 11 between the final element of the projection system PS and the support table WT or substrate W. (Note that unless otherwise specified, the following description relating to the surface of the substrate W also additionally or alternatively refers to the surface of the support table WT.) The fluid handling structure IH is substantially stationary with respect to the projection system PS in the XY plane, but may have some relative movement in the Z direction (in the direction of the optical axis). In some embodiments, a seal is formed between the fluid handling structure IH and the surface of the substrate W, and the seal can be a non-contact seal such as a gas seal (such a system with a gas seal is disclosed in European Patent Application Publication EP-A-1,420,298) or a liquid seal.

[0038]

[0049] The fluid handling structure IH at least partially confines the liquid in the space 11 between the final element of the projection system PS and the substrate W. A non-contact seal to the substrate W can be formed around the image field of the projection system PS so that the liquid is confined within the space 11 between the surface of the substrate W and the final element of the projection system PS. The space 11 is located below the final element of the projection system PS and is at least partially formed by the fluid handling structure IH surrounding it. The liquid is drawn into the space 11, which is below the projection system PS and inside the fluid handling structure IH, by one of the liquid openings 13. The liquid can be removed by the other liquid opening 13. The liquid may be drawn into the space 11 from at least two liquid openings 13. Which liquid opening 13 is used to supply the liquid and which is used to remove the liquid (optionally) may depend on the direction of movement of the support table WT. The fluid handling structure IH may extend slightly above the final element of the projection system PS. The liquid level rises above the final element so that a liquid buffer is supplied. In one embodiment, the fluid handling structure IH has an inner circumference that is closely conformed to the shape of the projection system PS or its final element at its upper end, and may be, for example, circular. At the bottom, the inner circumference is closely conformed to the shape of the image field, which may be, for example, rectangular, but is not required.

[0039]

[0050] The liquid can be confined to space 11 by a gas seal 16 formed between the bottom of the fluid handling structure IH and the surface of the substrate W during use. The gas seal 16 is formed by gas. The gas in the gas seal 16 is supplied under pressure to the gap between the fluid handling structure IH and the substrate W via an inlet 15. The gas is extracted via an outlet 14. The excess pressure on the gas inlet 15, the vacuum level relative to the outlet 14, and the geometry of the gap are configured to have a high-speed inward gas flow that confines the liquid. The force of the gas on the liquid between the fluid handling structure IH and the substrate W confines the liquid to space 11. The inlet / outlet can be an annular groove surrounding space 11. The annular groove may be continuous or discontinuous. The gas flow has the effect of confining the liquid to space 11. Such a system is disclosed in U.S. Patent Application Publication US2004-0207824, which is incorporated herein by reference in its entirety. In some embodiments, the fluid handling structure IH does not have a gas seal 16.

[0040]

[0051] Figure 3 is a side cross-sectional view showing another liquid supply system, i.e., a fluid handling system, according to one embodiment. The configuration shown in Figure 3, described below, can be applied to the lithography apparatus shown in Figure 1. The liquid supply system comprises a fluid handling structure IH (i.e., a liquid confinement structure) extending along at least a portion of the boundary of the space 11 between the final element of the projection system PS and the support table WT or substrate W. (Note that unless otherwise specified, the following descriptions relating to the surface of the substrate W also additionally or alternatively refer to the surface of the support table WT.)

[0041]

[0052] The fluid handling structure IH at least partially confines the liquid in the space 11 between the final element of the projection system PS and the substrate W. The space 11 is located below the final element of the projection system PS and is at least partially formed by the fluid handling structure IH surrounding it. In one embodiment, the fluid handling structure IH comprises a main body member 53 and a porous member 33. The porous member 33 is plate-shaped and has a plurality of holes (i.e., openings or pores). In one embodiment, the porous member 33 is a mesh plate formed by a number of small holes 84 in a mesh-like manner. Such a system is disclosed in U.S. Patent Application Publication US2010 / 0045949A1, which is incorporated herein by reference in its entirety.

[0042]

[0053] The main body member 53 includes a supply port 72 that can supply liquid to the space 11 and a recovery port 73 that can recover liquid from the space 11. The supply port 72 is connected to a liquid supply device 75 via a passage 74. The liquid supply device 75 can supply liquid to the supply port 72. The liquid supplied from the liquid supply device 75 is supplied to each supply port 72 via the corresponding passage 74. The supply ports 72 are located in predetermined positions on the main body member 53 facing the optical path, near the optical path. The recovery port 73 can recover liquid from the space 11. The recovery port 73 is connected to a liquid recovery device 80 via a passage 79. The liquid recovery device 80 includes a vacuum system and can recover liquid by sucking it through the recovery port 73. The liquid recovery device 80 recovers the liquid recovered through the passage 79 via the recovery port 73. The porous member 33 is located at the recovery port 73.

[0043]

[0054] In one embodiment, to form a space 11 containing liquid between the projection system PS and the fluid handling structure IH on one side and the substrate W on the other side, liquid is supplied to the space 11 from a supply port 72, and the pressure in the recovery chamber 31 within the fluid handling structure IH is adjusted to a negative pressure to recover the liquid through the holes 84 (i.e., recovery port 73) of the porous member 33. By performing a liquid supply operation using the supply port 72 and a liquid recovery operation using the porous member 33, the space 11 is formed between the projection system PS and the fluid handling structure IH on one side and the substrate W on the other side.

[0044]

[0055] As shown in the figure, the apparatus may be of the immersion type. Alternatively, the apparatus may be of the dry type in which the substrate is not immersed in liquid.

[0045]

[0056] Figure 4 shows a cross-sectional view of a support table WT of a lithography apparatus according to one embodiment of the present invention. The support table WT is configured to support a substrate W. The lithography apparatus also includes a gas flow system that interacts with the support table WT.

[0046]

[0057] The support table WT includes a base surface 61. In one embodiment, the base surface 61 is configured to be substantially parallel to the lower surface of the substrate W supported by the support table WT. In one embodiment, the support table WT includes a plurality of burrs 62. The burrs 62 project above the base surface 61. Each of the plurality of burrs 62 has an individual distal end 63. The distal ends 63 of the burrs are positioned on the support plane to support the substrate W. When the substrate W is supported by the support table WT, the substrate W is supported by the individual distal ends 63 of each of the plurality of burrs 62.

[0047]

[0058] During use, the substrate W is supported by the support table WT. When the substrate W is supported by the support table WT, the substrate W is supported by the distal ends 63 of each individual bar 62.

[0048]

[0059] A gap is defined between the base surface 61 of the support table WT and the substrate W. The width of the gap corresponds to the height of the distal end 63 of the bar from the base surface 61.

[0049]

[0060] Figure 7 schematically shows a portion of the support table WT and gas flow system 97 of a lithography apparatus according to one embodiment of the present invention in a cross-sectional view. The lithography apparatus comprises the gas flow system 97. The gas flow system 97 interacts with the support table WT. As shown in Figure 7, in one embodiment, the support table WT comprises a plurality of gas flow openings 69. The gas flow openings 69 facilitate clamping of the substrate W. Gas can be extracted from the gap enclosed by the substrate W and the support table WT through the gas flow openings 69 to reduce the pressure in this gap for clamping of the substrate W. In one embodiment, an additional two-phase extractor (not shown in Figure 7) is located radially outside the outer seal 67 to extract gas and liquid bubbles from between the substrate W and the support table WT.

[0050]

[0061] In one embodiment, the gas flow system 97 is configured to supply gas from a gas flow opening 69 into the gap between the base surface 61 and the substrate W. In another embodiment, the gas flow system 97 is configured to extract gas from the gap between the base surface 61 and the substrate W through the gas flow opening 69. In yet another embodiment, the gas flow system 97 is configured to supply gas to the gap through the gas flow opening 69 and to extract gas from the gap.

[0051]

[0062] In a method for unloading a substrate W from a support table WT, gas is supplied to the gap between the base surface 61 and the substrate W via a gas flow opening 69 of the support table WT. In one embodiment, the method for unloading the substrate W includes different stages of unloading in which different pressure profiles are applied to the gap between the base surface 61 and the substrate W.

[0052]

[0063] There may be two different stages of unloading. In one embodiment, the method includes an initial stage of unloading and a later stage of unloading. The later stage of unloading follows the initial stage of unloading. In one embodiment, the later stage of unloading follows immediately after the initial stage of unloading. In an alternative embodiment, there are three stages of unloading. In one embodiment, an intermediate stage of unloading follows the initial stage of unloading and precedes the later stage of unloading. In one embodiment, there are four or more stages of unloading.

[0053]

[0064] In one embodiment, the support table WT comprises a central region 81 and an outer region 83, as shown in Figure 4. The outer region 83 is radially outward from the central region 81.

[0054]

[0065] In the initial stage of unloading, gas is supplied from at least one gas flow opening 69 in the outer region 83, but not from the gas flow opening in the central region 81. In the later stage of unloading, gas is supplied from at least one gas flow opening 69 in the outer region 83, and also from at least one gas flow opening in the central region 81.

[0055]

[0066] When the substrate W is clamped to the support table WT, a vacuum (or near-vacuum pressure) is applied to the central region 81 and the outer region 83. When the substrate W is unloaded, the vacuum is released in the outer region 83 before the vacuum is released in the central region 81. By releasing the vacuum in the outer region 83 first, and then in the central region 81, the substrate W is expected to be released (i.e., move away) from the edges towards the center. One embodiment of the present invention is expected to prevent the substrate W from sliding on the crowbars 62 in the outer region 83 (e.g., the peripheral area) of the support table WT. Thus, one embodiment of the present invention is expected to achieve a reduction in wear of the crowbars 62 on the outer periphery of the support table WT.

[0056]

[0067] In one embodiment, the central region 81 borders the outer region 83. However, this is not always the case. For example, as shown in Figure 4, in one embodiment, the support table includes an intermediate region 82.

[0057]

[0068] As described above, in some embodiments, the method includes an intermediate step in unloading. This may be particularly true when the support table WT has an intermediate region 82. The intermediate region 82 is radially outside the central region 81. The intermediate region 82 is radially inside the outer region 83. In some embodiments, the intermediate region 82 borders the central region 81. In some embodiments, the intermediate region 82 borders the outer region 83.

[0058]

[0069] In one embodiment, during the initial stage of unloading, gas is supplied from at least one gas flow opening 69 in the outer region 83, but not from the gas flow openings in the central region 81 and the intermediate region 82. During the intermediate stage of unloading, gas is supplied from at least one gas flow opening 69 in the outer region 83 and at least one gas flow opening 69 in the intermediate region 82, but not from the gas flow opening 69 in the central region 81. During the later stage of unloading (after the intermediate stage of unloading), gas is supplied from at least one gas flow opening 69 in the outer region 83, at least one gas flow opening 69 in the intermediate region 82, and at least one gas flow opening 69 in the central region 81.

[0059]

[0070] Therefore, in one embodiment, the support table WT comprises three different segments or clamping areas from which vacuum can be applied and released at different timings. By providing an additional intermediate region 82 and releasing the vacuum in the outer region 83, then the intermediate region 82, and then the central region 81, one embodiment of the present invention is expected to reduce wear on the crowbar 62. This is because the successive release of vacuum, starting from the outer periphery and ending in the central region 81, is expected to reduce the likelihood of the substrate W sliding on the crowbar 62, i.e., reduce the sliding force. In one embodiment, the support table WT comprises four or more different segments or clamping areas from which vacuum can be released, starting from the outer periphery and ending in the central region 81, at different timings.

[0060]

[0071] In one embodiment, the gas flow system 97 is configured to inject gas (e.g., air) from the gas flow opening 69 before releasing the vacuum. The gas injection is intended to encourage the substrate W to move away from the bar 62 in order to reduce the likelihood of slippage. In one embodiment, in the initial stage of unloading, gas is supplied from at least one gas flow opening 69 in the outer region 83 at a first pressure greater than the ambient pressure. The gas supplied at the first pressure greater than the ambient pressure is a gas injection that encourages the substrate W to move away from the bar 62. After this gas injection, gas is supplied from at least one gas flow opening 69 in the outer region 83 at a second pressure less than the first pressure. In one embodiment, the second pressure is greater than the ambient pressure. Therefore, when the second pressure is applied, the substrate W does not reattach to the support table WT. In an alternative embodiment, the second pressure is less than the ambient pressure so that the vacuum is released after the initial gas injection. By supplying gas at the second pressure less than the ambient pressure, the vacuum is gradually released in the outer region 83. Therefore, gas injection can be performed prior to the release of the vacuum in the outer region 83. By supplying gas at a first pressure greater than the ambient pressure, the possibility of the warped substrate W unnecessarily coming into contact with the crowbar 62 during the unloading process is reduced. Generally, when the substrate W warps, its edges warp. Therefore, the substrate W is at the greatest risk of unnecessarily coming into contact with the crowbar 62 in the outer region 83 during the unloading process.

[0061]

[0072] In one embodiment, the gas can be supplied to any of the outer region 83, the intermediate region 82, and the central region 81 at a first pressure greater than the ambient pressure. For example, in one embodiment, during an intermediate stage of unloading, the gas is supplied from at least one gas flow opening 69 in the intermediate region 82 at a first pressure greater than the ambient pressure, and then the gas is supplied from at least one gas flow opening 69 in the intermediate region 82 at a second pressure less than the first pressure.

[0062]

[0073] In one embodiment, during the later stages of unloading, gas is supplied from at least one gas flow opening 69 in the central region 81 at a first pressure greater than the ambient pressure, and then gas is supplied from at least one gas flow opening 69 in the central region 81 at a second pressure less than the first pressure. Thus, injection can be applied to each region before the vacuum is released. This reduces the force with which the substrate W slides on the crowbar 62, i.e., the likelihood of the substrate W sliding on the crowbar 62 is reduced, resulting in reduced wear on the crowbar 62.

[0063]

[0074] The present invention has been described above in terms of a method for unloading a substrate W from a support table WT. The present invention is similarly applicable to a method for loading a substrate W onto a support table WT.

[0064]

[0075] According to a method for loading a substrate W onto a support table WT, the method includes extracting gas from gaps through multiple gas flow openings 69 of the support table WT. The method for loading the substrate W includes at least three loading steps. There may be four or more steps.

[0065]

[0076] In the first stage of loading, gas is extracted from at least one gas flow opening 69 in the central region 81, but not from the gas flow openings 69 in the intermediate region 82 and the outer region 83. Next, in the second stage of loading, gas is extracted from at least one gas flow opening 69 in the central region 81 and at least one gas flow opening 69 in the intermediate region 82, but not from the gas flow opening 69 in the outer region 83. Next, in the third stage of loading, gas is extracted from at least one gas flow opening 69 in the central region 81, at least one gas flow opening 69 in the intermediate region 82, and at least one gas flow opening 69 in the outer region 83.

[0066]

[0077] Therefore, the vacuum can be applied first to the central region 81, then to the intermediate region, and then to the outer region 83. One embodiment of the present invention is expected to achieve a reduction in lattice deformation remaining after the substrate W is loaded. Deformation of the substrate W can increase the overlay error. For example, deformation of the substrate W can reduce the accuracy of radiation incidence onto the substrate W. Curvature of the surface of the substrate W may cause slight mis-contact between the radiation and the substrate W. In particular, if the substrate W is first clamped to the bar 62 on the outer periphery of the support table WT, any deformation of the substrate W may remain when the substrate W is clamped. By applying the vacuum first to the central region 81 and then to the outer region 83, it is expected that the clamping of the substrate W to the bar 62 will start from the central region 81. This is expected to reduce the deformation of the substrate W when the substrate W is loaded onto the support table WT. In one embodiment, the support table WT comprises four or more regions. During loading, the vacuum is applied first to the central region and then to the outermost region.

[0067]

[0078] As described above, the gas may be supplied to the same region across different stages of unloading. For example, the gas may be supplied to the central region 81 in the initial, intermediate, and late stages of unloading. The gas flow opening 69 used to supply the gas at different stages may be the same gas flow opening 69. Alternatively, different gas flow openings 69 may be used within specific regions at different stages.

[0068]

[0079] Similarly, during the loading process, the gas may be extracted to a single region at different stages of the loading process. For example, the gas may be extracted in the central region 81 at the first, second, and third stages of the loading process. The gas flow opening 69 used for a particular region at different stages may be the same gas flow opening 69. Alternatively, different gas flow openings may be used for a particular region at different stages.

[0069]

[0080] In one embodiment, gas may be supplied through gas flow openings 69 during the loading process. This is to prevent the warped substrate W from unnecessarily touching the crowbars 62, particularly on the outer periphery of the support table WT. In one embodiment, during the first stage of loading, gas at a pressure greater than the ambient pressure is supplied through at least one gas flow opening 69 in the intermediate region 82 and / or at least one gas flow opening 69 in the outer region 83. Thus, while a vacuum is formed in the central region 81, gas is being supplied to the intermediate region 82 and the outer region 83. This prevents the substrate W from unnecessarily touching the crowbars 62 in the intermediate region 82 or the outer region 83 before the substrate W comes into contact with the crowbars 62 in the central region 81.

[0070]

[0081] In one embodiment, during the second stage of loading, gas is supplied from at least one gas flow opening 69 in the outer region 83 at a pressure greater than the ambient pressure. Thus, gas injection can be provided to the outer region 83 even when a vacuum is formed in the intermediate region 82.

[0071]

[0082] As described above, in one embodiment, vacuum is applied first to the central region 81, then to the intermediate region 82, and then to the outer region 83. However, in an alternative embodiment, the loading sequence is reversed. In one embodiment, in the first stage of loading, gas is extracted from at least one gas flow opening 69 in the outer region 83 of the support table WT, but not from the gas flow opening 69 in the intermediate region 82 of the support table WT or the gas flow opening 69 in the central region 81 of the support table WT. In the second stage of loading, gas is extracted from at least one gas flow opening 69 in the outer region 83 and at least one gas flow opening 69 in the intermediate region 82, but not from the gas flow opening 69 in the central region 81. In the third stage of loading, gas is extracted from at least one gas flow opening 69 in the outer region 83, at least one gas flow opening 69 in the intermediate region 82, and at least one gas flow opening 69 in the central region 81.

[0072]

[0083] This embodiment of the present invention is expected to be advantageous for clamping a warped substrate W having a bowl shape (i.e., the outer periphery of the substrate W is higher than the central portion of the substrate W).

[0073]

[0084] In one embodiment, the gas flow between the central region 81 and the intermediate region 82 is restricted. By restricting the gas flow between the central region 81 and the intermediate region 82, the extraction or supply of gas to or from the gaps in the central region 81 and the intermediate region 82 can be performed substantially independently.

[0074]

[0085] For example, Figure 4 shows the central region wall 64. The central region wall 64 protrudes above the base surface 61. The central region wall 64 restricts the gas flow between the intermediate region 82 and the central region 81. In one embodiment, the central region wall 64 is configured to restrict the gas flow between the central region 81 and the intermediate region 82. The top of the central region wall 64 does not come into contact with the substrate W when the substrate W is clamped to the support table WT. The central region wall 64 functions as a seal. The central region wall 64 is not as high as the bar 62. A small gap exists between the substrate W and the top of the central region wall 64.

[0075]

[0086] Figure 5 shows a plan view of the support table WT shown in Figure 4. The crowbar 62 is omitted from Figure 5 for simplicity. In one embodiment, the central region wall 64 is continuous. The central region wall 64 has no gaps between the intermediate region 82 and the central region 81 where gas can enter or exit. As shown in Figure 5, in one embodiment the central region wall 64 is circular in plan view. However, other shapes are also possible. For example, the central region wall 64 may be square or rectangular.

[0076]

[0087] As shown in Figure 5, in one embodiment, the intermediate region 82 surrounds the central region 81. The intermediate region 82 surrounds the central region 81 in a plan view. As shown in Figure 5, in one embodiment, the radial periphery of the intermediate region 82 is defined by the intermediate region wall 65. The intermediate region wall 65 protrudes above the base surface 61. The intermediate region wall 65 is configured to restrict the gas flow between the intermediate region 82 and the outer region 83. This allows for substantially independent supply or extraction of gas to or from the gaps in the intermediate region 82 and the outer region 83. The intermediate region wall 65 functions as a seal. The intermediate region wall 65 is not as high as the bar 62. A small gap exists between the substrate W and the top of the intermediate region wall 65.

[0077]

[0088] By enabling substantially independent gas flows to each region, the loading and unloading processes can be controlled more precisely. As shown in Figure 5, in one embodiment, the outer region 83 surrounds the intermediate region 82. The outer region 83 surrounds the intermediate region 82 in a plan view.

[0078]

[0089] As shown in Figure 5, in one embodiment, the outer region 83 is defined by an outer region wall 66 along its radial periphery. The outer region wall 66 protrudes above the base surface 61. The outer region wall 66 is configured to restrict gas flow between the outer region 83 and the region radially outside the outer region 83. The outer region wall 66 functions as a seal. The outer region wall 66 is not as high as the bar 62. A small gap exists between the substrate W and the top of the outer region wall 66.

[0079]

[0090] In one embodiment, the support table WT includes one or more outer seals 67. The outer region wall 66 and the outer seal 67 may form a double seal. The double seal may be for a water extraction system. For example, a fluid extraction opening 88 (see Figure 7) may be provided for extracting liquid (and gas) from the space between the outer region wall 66 and the outer seal 67.

[0080]

[0091] In one embodiment, each region has its own intake passage. This means that the gas pressure in each region can be controlled individually. In one embodiment, the gas flow system 97 includes flow paths 98 for each region. For example, in one embodiment, the gas flow system 97 includes a central flow path connected to at least one gas flow opening 69 in the central region 81, an intermediate flow path connected to at least one gas flow opening 69 in the intermediate region 82, and an outer flow path connected to at least one gas flow opening in the outer region 83. The central flow path, the intermediate flow path, and the outer flow path are independent of each other. The central flow path, the intermediate flow path, and the outer flow path are depicted as bidirectional arrows in Figure 7.

[0081]

[0092] Figure 6 shows a plan view of a support table WT, which is an alternative to the support table WT shown in Figure 5. However, the functionality of the present invention in the embodiment shown in Figure 6 is substantially the same as that in the embodiment shown in Figure 5. The crowbar 62 has been omitted from Figure 6 for simplicity.

[0082]

[0093] As shown in Figure 6, in one embodiment, the central region 81 includes multiple non-overlapping central sub-regions 91. Each central sub-region 91 is defined by a central sub-region wall 94. Each central sub-region wall 94 protrudes above the base surface 61. Each central sub-region wall 94 is configured to restrict gas flow between the central region 81 and any other region (e.g., the outer region 83 or the intermediate region 82). This allows for the supply or extraction of gas to or from the gap in the central region 81 to be substantially independent of other regions. Each central sub-region wall 94 functions as a seal. Each central sub-region wall 94 is not as high as the bar 62. A small gap exists between the substrate W and the top of each central sub-region wall 94.

[0083]

[0094] As shown in Figure 6, in one embodiment, the central sub-regions 91 are spaced apart from each other. The central sub-region walls 94 of adjacent central sub-regions 91 are separated and do not come into contact with each other. This means that there is space between the central sub-regions 91 (i.e., outside the central sub-region walls 94) that does not belong to the central region 81, the intermediate region 82, or the outer region 83. Therefore, the intermediate region 82 or the outer region 83 does not need to completely surround the central region 81.

[0084]

[0095] Alternatively, adjacent central sub-regions 91 may share a boundary with each other. The central sub-region wall 94 may be shared by adjacent central sub-regions 91. This means that the central sub-region wall 94 may be a boundary line separating adjacent central sub-regions 91. One central sub-region 91 may be on one side of the central sub-region wall 94, and the other central sub-region 91 may be on the other side of the central sub-region wall 94.

[0085]

[0096] As shown in Figure 6, the intermediate region 82 and the outer region 83 may be arranged similarly to the central region 81. In particular, the present invention can be implemented by using seal islands (formed by sub-region walls). Sub-regions are sometimes called seal islands because, in plan view, their edges appear as islands defined by seals (i.e., sub-region walls). In particular, in one embodiment, the intermediate region 82 includes a plurality of non-overlapping intermediate sub-regions 92. Each intermediate sub-region 92 is defined by an intermediate sub-region wall 95. Each intermediate sub-region wall 95 protrudes above the base surface 61. Each intermediate sub-region wall 95 is configured to restrict gas flow between the intermediate region 82 and any other region. This means that gas can be supplied to or extracted from the gap in the intermediate region 82 substantially independently of the other region. Each intermediate sub-region wall 95 functions as a seal. Each intermediate sub-region wall 95 is not as high as the bar 62. A small gap exists between the substrate W and the top of each intermediate sub-region wall 95.

[0086]

[0097] As shown in Figure 6, in one embodiment, the intermediate sub-regions 92 are spaced apart from each other. However, this is not always the case. In one embodiment, the intermediate sub-regions 92 are directly adjacent to each other without any gaps. For example, the intermediate sub-region wall 95 of one intermediate sub-region 92 may be connected to the intermediate sub-region wall 95 of an adjacent intermediate sub-region 92 so that there is no gap between the adjacent intermediate sub-regions 92.

[0087]

[0098] As shown in Figure 6, in one embodiment, the outer region 83 includes a plurality of non-overlapping outer sub-regions 93 that restrict gas flow between them. Each outer sub-region 93 is defined by an outer sub-region wall 96. Each sub-region wall 96 protrudes above the base surface 61. The outer region 83 is composed of the outer sub-regions 93. The spaces between the outer sub-regions 93 (to which gas can flow freely) do not form part of the outer region 83. Each outer sub-region wall 96 is configured to restrict gas flow between the outer region 83 and any other region. This means that gas can be supplied to or extracted from the outer region 83 substantially independently of any other region. Each outer sub-region wall 96 acts as a seal. Each outer sub-region wall 96 is not as high as the bar 62. A small gap exists between the substrate W and the top of each outer sub-region wall 96.

[0088]

[0099] As shown in Figure 6, in one embodiment, the outer sub-regions 93 are spaced apart from each other. However, this is not always the case. In an alternative embodiment, the outer sub-regions 93 are directly adjacent to each other without any gaps.

[0089]

[0100] Figure 5 shows the concentric region of the support table WT. In contrast, Figure 6 shows the region formed by using an island of seals (formed by sub-region walls). In some embodiments, at least one region may be formed as shown in Figure 5, and at least one region may be formed as shown in Figure 6. For example, in some embodiments, the central region 81 is formed from the central sub-region 91 as shown in Figure 6, while the outer region 83 is defined by the intermediate region wall 65 and the outer region wall 66. Other combinations of the embodiments shown in Figures 5 and 6 are also possible.

[0090]

[0101] For example, as shown in Figures 5 to 7 and described above, in one embodiment, different regions of the support table WT are separated from each other by walls. However, the provision of walls is not essential. In alternative embodiments, no walls are provided.

[0091]

[0102] Figure 13 schematically shows a support table in plan view according to one embodiment of the present invention. In one embodiment, the support table WT comprises a plurality of independently controllable flow channels 98 (see Figure 9), each connected to a gas flow opening 69 in a different region of the support table WT. Figure 13 shows three sets of gas flow openings 69. Each set of gas flow openings 69 is in fluid communication with a flow channel 98. The flow channels 98 are independently controllable from one another. This makes it possible to independently control the pressure in each set of gas flow openings 69 from one another.

[0092]

[0103] Each set of gas flow openings 69 includes multiple gas flow openings 69. As shown in Figure 13, in one embodiment, one set of gas flow openings 69 is arranged in a ring shape. Other arrangements are also possible, such as a square or a rhombus. As shown in Figure 13, in one embodiment, each set has 12 gas flow openings 69. However, the number of gas flow openings 69 in each set is not particularly limited and may be, for example, 6, 10, or 16.

[0093]

[0104] Each set of gas flow openings 69 is located at a different radial distance from the center of the support table WT. Figure 13 shows a configuration in which the first set of gas flow openings 69 is located at a radial distance r1 from the center of the support table WT. The second set of gas flow openings 69 is located at a radial distance r2 from the center of the support table WT. The third set of gas flow openings 69 is located at a radial distance r3 from the center of the support table WT. In Figure 13, one dashed line represents the boundary between the central region 81 and the intermediate region 82 of the support table. The other dashed line represents the boundary between the intermediate region 82 and the outer region 83 of the support table. As shown in Figure 13, the first set of gas flow openings 69 is located in the central region 81 of the support table WT. The second set of gas flow openings 69 is located in the intermediate region 82 of the support table WT. The third set of gas flow openings 69 is located in the outer region 83 of the support table WT.

[0094]

[0105] The flow in each set of gas flow openings 69 can be controlled to provide the above-described loading or unloading sequence. For example, in one embodiment, gas extraction is performed first through a first set of gas flow openings 69, then additionally through a second set of gas flow openings 69, and then additionally through a third set of gas flow openings 69. The number of sets of gas flow openings 69 is not particularly limited and may be, for example, two, four, or more.

[0095]

[0106] Figure 13 mainly shows the bar plate 21 of the support table WT (see Figures 5 and 6 for the difference between the bar plate 21 and the chuck 22 of the support table WT). As shown in Figure 13, the bar plate 21 has a radius r0. In one embodiment, the first set of gas flow openings 69 is arranged such that r1:r0 is at least 0.2. In another embodiment, the first set of gas flow openings 69 is arranged such that r1:r0 is at most 0.5. In yet another embodiment, the first set of gas flow openings 69 is arranged such that r1:r0 is about 0.4.

[0096]

[0107] In one embodiment, a second set of gas flow openings 69 is arranged such that r2:r0 is at least 0.5. In another embodiment, a second set of gas flow openings 69 is arranged such that r2:r0 is at most 0.8. In yet another embodiment, a second set of gas flow openings 69 is arranged such that r2:r0 is approximately 0.6.

[0097]

[0108] In one embodiment, a third set of gas flow openings 69 is arranged such that r3:r0 is at least 0.5. In another embodiment, a third set of gas flow openings 69 is arranged such that r3:r0 is at most 0.95. In yet another embodiment, a third set of gas flow openings 69 is arranged such that r3:r0 is approximately 0.9.

[0098]

[0109] As described above, other arrangements of the gas flow opening 69 are also possible, such as a square or a rhombus. Any of the above walls can be provided in other forms, such as a non-radial opening configuration. This is useful because the substrate W is not likely to warp symmetrically, i.e., rotationally, and is not likely to warp in a saddle shape, for example.

[0099]

[0110] As shown in Figure 13, the wall depicted in Figure 5 is not provided between the sets of gas flow openings 69, but in one embodiment the support table is provided with an outer seal 67.

[0100]

[0111] As shown in Figure 13, in one embodiment, the support table WT is provided with a number of pinholes 71. Although six pinholes 71 are depicted in Figure 13, any suitable number of pinholes 71 may be used, i.e., the number of pinholes 71 is not limited to six. The pinholes 71 allow the pins 70 (shown in Figure 12 and described later) to extend vertically through the support table WT. In one embodiment, one of the sets of gas flow openings WT is located at substantially the same radial distance from the center of the support table WT as the pinholes 71. In the configuration shown in Figure 13, the second set of gas flow openings 69 and the pinholes 71 are located at a radial distance r2 from the center of the support table WT.

[0101]

[0112] Figure 8 schematically shows a support table WT and a gas flow system 97 according to one embodiment of the present invention. Figure 8 shows the flow channels 98 of the gas flow system 97. The flow channels 98 are in fluid communication with the gas flow opening 69 of the support table WT. Figure 8 shows only one flow channel 98 as an example. The gas flow system 97 comprises multiple flow channels 98 to independently control the application and release of vacuum to each region of the support table WT.

[0102]

[0113] As shown in Figure 8, in one embodiment, the gas flow system 97 includes at least one piezoelectric valve 99. The piezoelectric valve 99 is configured to change the flow rate through a flow path 98, which may be a central flow path, an intermediate flow path, or an outer flow path. However, it is not necessary to use a piezoelectric valve. Other valves can also be used to change the flow rate. For example, a solenoid valve may be used.

[0103]

[0114] In one embodiment, the piezoelectric valve 99 is used to control pressure and flow during the substrate loading sequence and / or substrate unloading sequence. The use of the piezoelectric valve 99 is expected to simplify the creation of load / unload sequences for various applications. For example, the sequence may depend on the type of layer formed on the substrate W during the exposure operation. This allows for a reduction in grid errors of the substrate W during the substrate loading process.

[0104]

[0115] By providing a variable valve such as a piezoelectric valve 99, the load sequence for any shape of the substrate W can be improved using closed-loop feedback control. For example, in one embodiment, the support table WT includes at least one pressure sensor 85. The pressure sensor 85 is configured to sense the pressure near the substrate W. For example, the pressure sensor 85 is configured to sense the pressure in the flow path 98 as shown in Figure 8. Alternatively, the pressure sensor may be located elsewhere. The pressure sensor 85 may be configured to sense the pressure between the support table WT and the substrate W. In one embodiment, the controller of the gas flow system 97 is configured to change the flow rate of the flow path 98 based on the pressure sensed by the pressure sensor 85.

[0105]

[0116] In one embodiment, the gas flow system 97 includes a valve pressure sensor 86. The valve pressure sensor 86 is configured to sense the pressure in a flow path 98 near a piezoelectric valve 99. In another embodiment, the gas flow system 97 includes a negative pressure source 87. The negative pressure source 87 may be, for example, a vacuum generator.

[0106]

[0117] In one embodiment, the pressure sensor 85 is located as close as possible to the substrate W. For example, the pressure sensor 85 is part of a support table WT. In one embodiment, the support table WT comprises a chuck 22 and a bar plate 21 (see, for example, Figures 5 and 6). The bar plate 21 comprises a base surface 61 and a bar 62. The bar plate 21 is attached to the chuck 22. In one embodiment, the pressure sensor 85 is mounted on the bar plate 21 so as close as possible to the substrate W. This helps to better measure what is happening on the substrate W. A valve pressure sensor 86 is located near the outlet of the piezoelectric valve 99. The valve pressure sensor 86 can be used to keep the control stable.

[0107]

[0118] The relationship between the setting of the piezoelectric valve 99 and the pressure response of the substrate W can be measured by the pressure sensor 85. This measurement can be used as a feedforward correction for the next substrate W, especially when deformation (e.g., warpage) can be compared for all substrates in a group of substrates.

[0108]

[0119] The piezoelectric valve 99 (or any other type of valve) can be controlled based on the output from the pressure sensor 85. The pressure sensor 85 may be provided in each region of the support table WT to provide feedback. By using the pressure sensor 85 in combination with the piezoelectric valve 99 (or any other type of valve), the load / unload sequence can be configured to be more robust.

[0109]

[0120] In one embodiment, the gas flow system 97 includes a mass flow controller for each region of the support table WT. Each mass flow controller is configured to measure and control the gas flow through a channel 98 associated with one of the central region 81, the intermediate region 82, and the outer region 83.

[0110]

[0121] In one embodiment, each region comprises a flow path 98 and a pressure sensor 85. The flow path 98 is in fluid communication with a gas flow opening 69 in that region. The pressure sensor 85 is configured to sense the pressure in that region, namely the central region 81, the intermediate region 82, or the outer region 83. This may include sensing the pressure between the substrate W and the support table WT in that region, and / or sensing the pressure in the flow path 98. This makes it possible to independently determine the suction flow in each region so that a temporally optimal pressure profile can be applied to each region. Measuring the pressure between the substrate W and the support table WT may be beneficial in that it may provide a more accurate pressure influencing the substrate W, which can then be used as a parameter to more precisely control the clamping.

[0111]

[0122] In one embodiment, when the substrate W is loaded onto the support table WT, the controller 500 is configured to control the timing of gas extraction from the gas flow openings 69 in each region based on the pressure of each sensed flow path 98.

[0112]

[0123] One embodiment of the present invention is expected to achieve an improved loading sequence without the need to know the warpage of the substrate W in advance. By determining the suction flow in each region, the controller 500 can automatically determine the optimal loading sequence. For example, the controller 500 can determine a sequence to turn on the vacuum from the central region 81 or from the outer region 83.

[0113]

[0124] Figure 9 schematically shows the region arrangement of a support table WT according to one embodiment of the present invention, together with the gas flow system 97. The region arrangement shown in Figure 9 is an example of a hybrid of the concentric arrangement in Figure 5 and the island seal arrangement in Figure 6. In the arrangement of Figure 9, the central region 81 is defined by the central region wall 64, similar to the method shown in Figure 5. On the other hand, the intermediate region 82 includes a plurality of intermediate sub-regions 92 defined by the intermediate sub-region wall 95, similar to the arrangement shown in Figure 6. The outer region 83 includes a plurality of outer sub-regions 93 defined by the outer sub-region wall 96, similar to the arrangement shown in Figure 6.

[0114]

[0125] Figure 9 shows an example of a non-circular seal island (i.e., sub-region). The intermediate sub-regions 92 and outer sub-regions 93 have the shape of a part of the annular band rather than being circular. In the arrangement shown in Figure 9, each intermediate sub-region 92 corresponds to a quarter of the annular band. There are four intermediate sub-regions 92. However, the number of intermediate sub-regions 92 may be less than or greater than four. As shown in Figure 9, in one embodiment, the support table WT has eight outer sub-regions 93, each corresponding to half of a quarter of the annular band. However, the number of outer sub-regions 93 may be less than or greater than eight.

[0115]

[0126] As described above, in one embodiment, the vacuum pressure can be controlled substantially independently for regions at different radial positions (i.e., different distances from the center of the support table WT). The support table WT has radial degrees of freedom for controlling the clamp pressure.

[0116]

[0127] In some embodiments, the lithography apparatus has tangential (or rotational) degrees of freedom for controlling the clamp pressure. In particular, in some embodiments, the clamp pressure of different sub-regions (located in different tangential positions) within the same region can be controlled independently. For example, in some embodiments, the gas flow between intermediate sub-regions 92 is restricted so that gas can be extracted or supplied to each gap in the intermediate sub-regions 92 substantially independently.

[0117]

[0128] As shown in Figure 9, in one embodiment, at least one region includes a plurality of tangentially distributed sub-regions. Each sub-region comprises a flow path 98 and a pressure sensor 85. The flow path 98 is in fluid communication with a gas flow opening 69 of the sub-region. The pressure sensor 85 is configured to sense the pressure related to the sub-region, and for example, the pressure sensor 85 may be configured to sense the pressure between the support table WT and the substrate W of the sub-region, or the pressure in the flow path 98.

[0118]

[0129] When the substrate W is loaded onto the support table WT, the controller 500 is configured to control the timing of gas extraction from the gas flow openings 69 of each sub-region based on the pressure of each sensed flow path 98. The controller 500 can determine an optimal loading sequence that independently controls sub-regions located at different tangential positions. This can be particularly beneficial when clamping a substrate W that is warped in a tangential direction.

[0119]

[0130] In one embodiment, the gas flow between intermediate sub-regions 92 is restricted by the intermediate sub-region walls 95. In another embodiment, the gas flow is restricted between the outer sub-regions 93 so that gas can be extracted or supplied to each gap in the outer sub-regions 93 substantially independently. For example, the gas flow between the outer sub-regions can be restricted by the outer sub-region walls 96.

[0120]

[0131] In embodiments in which the central region 81 includes multiple non-overlapping central sub-regions 91, the gas flow between the central sub-regions 91 can be restricted so that gas can be extracted or supplied to each gap in the central sub-regions 91 substantially independently. For example, the gas flow can be restricted by the central sub-region walls 94.

[0121]

[0132] In one embodiment, the gas flow system 97 includes a separate flow path 98 for each sub-region within a region of the support table WT. Figure 9 schematically shows a flow path 98 connected to at least one gas flow opening 69 in one outer sub-region 93. This represents only one flow path 98 for one sub-region. Each of the outer sub-regions 93 may have a separate flow path 98. Similarly, each of the intermediate sub-regions 92 may have a separate flow path 98. If the central region 81 comprises multiple central sub-regions 91, each of the central sub-regions 91 may have a separate flow path 98. The flow paths 98 are independent of each other.

[0122]

[0133] As shown in Figure 9, in one embodiment, the pressure sensor 85 is associated with the outer sub-region 93. The pressure sensor 85 is configured to sense the pressure within the outer sub-region 93. Thus, the pressure sensor 85 provides a measure of the clamp pressure in the gap between the base surface 61 and the substrate W within the outer sub-region 93.

[0123]

[0134] In one embodiment, the gas flow system 97 includes a piezoelectric valve 99 (or another type of valve, such as a solenoid valve) configured to control the pressure applied to the outer sub-region 93. The piezoelectric valve 99 may be controlled based on information from a pressure sensor 85. In one embodiment, the controller 500 controls the piezoelectric valve 99 based on information from the pressure sensor 85. Thus, the controller 500 can control the pressure in each of the outer sub-regions 93 substantially independently. Similarly, in one embodiment, the controller 500 can control the pressure in each of the intermediate sub-regions 92 substantially independently. In one embodiment, the controller 500 can control the pressure in each of the central sub-regions 91 substantially independently.

[0124]

[0135] Therefore, different pressures can be applied to different tangential positions of the support table WT. This means that the support table WT has tangential degrees of freedom for controlling the clamping pressure. In some embodiments, the pressure setpoint does not differ with respect to the difference in tangential position. In some embodiments, each sub-region has its own pressure control loop. This is useful for handling tangentially warped, i.e., curved substrates. This makes it possible to apply the same pressure to different tangential (i.e., rotational) positions even if the curvature of the substrate W differs at different tangential positions.

[0125]

[0136] Embodiments of the present invention are expected to improve the flatness of a clamped substrate W having a non-circularly symmetric warp (e.g., a saddle-shaped warp). This does not require prior knowledge of the warp of the substrate W to be clamped.

[0126]

[0137] As described above, the gas flow system 97 is capable of supplying a pressure higher than the ambient pressure (i.e., gas injection) to a specific region. In one embodiment, the gas flow system 97 is configured to independently supply gas at a pressure higher than the ambient pressure to each sub-region. Therefore, the supply of gas injection can be controlled depending on the tangential position within the support table WT. The tangential position refers to a position along the tangential (azimuth) direction.

[0127]

[0138] In an alternative embodiment, the gas extraction system 97 is controlled to stop gas extraction when the substrate W is at a predetermined distance above the support table WT. The predetermined distance may vary depending on the lithography apparatus. The predetermined distance can be calibrated for a particular lithography apparatus. More specifically, in one embodiment, the method of loading the substrate W onto the support table WT includes lowering the substrate W toward the support table WT. In one embodiment, for example, the substrate W is supported by a plurality of pins 70 (shown in Figure 12) that contact the underside of the substrate W. The pins 70 extend vertically through the support table WT. The controller 500 is configured to control the pins 70 (e.g., via actuators) so that the pins 70 move vertically downward. As the pins 70 move vertically downward, the substrate W descends toward the support table WT.

[0128]

[0139] In one embodiment, the substrate W is supported

[0140] As the substrate W descends toward the table WT, the negative pressure source 87 is controlled to apply negative pressure to extract gas from the gap between the base surface 61 of the support table WT and the substrate W through multiple gas flow openings 69 of the support table WT (shown in Figures 8 and 9). The negative pressure source 87, which may be, for example, a vacuum supply unit, is turned on when the substrate W descends toward the support table WT.

[0129]

[0141] In one embodiment, the controller 500 is configured to turn on the negative pressure source 87 when it determines that the pin 70 is moving vertically downward. In another embodiment, as soon as the pin 70 moves downward toward the support table WT together with the substrate W, the highest possible gas extraction flow rate is turned on. This is to reduce the air resistance between the substrate W and the support table WT as the substrate W moves toward the support table WT. This also increases throughput.

[0130]

[0142] In one embodiment, when the substrate W reaches a predetermined distance above the support table WT, a negative pressure source 87, which is in fluid communication with the gas flow opening 69 of the support table WT, is controlled to stop applying negative pressure. The vacuum is turned off when the pin 70 is just above the height of the support table WT.

[0131]

[0143] In one embodiment, the controller 500 is configured to monitor the vertical height of the pins 70 supporting the substrate W. As shown in Figure 12, in one embodiment, the lithography apparatus includes a height sensor 60. The height sensor 60 is configured to measure the vertical position of the pins 70. The height sensor 60 is configured to output a value representing the height of the substrate W from the support table WT. The height sensor 60 is connected to the controller 500. The height sensor 60 is configured to output a signal to the controller 500 indicating the height of the pins 70. Specifically, the height sensor 60 is configured to output a signal to the controller 500 indicating the height of the top of the pins 70 from the support table WT. The controller 500 is configured to control a negative pressure source 87 based on the signal received from the height sensor 60. In one embodiment, the controller 500 is configured to control the negative pressure source 87 by controlling a piezoelectric valve 99 (shown in Figures 8 and 9).

[0132]

[0144] In one embodiment, the height sensor 60 is located near the support table WT. In another embodiment, the height sensor 60 is connected to the support table WT, or is located inside or on top of the support table WT. In an alternative embodiment, as shown in Figure 12, the height sensor 60 is located away from the support table WT.

[0133]

[0145] According to this embodiment, the substrate W lands on the support table WT without applying a vacuum. This improves the positional accuracy that allows the substrate W to be clamped onto the support table WT.

[0134]

[0146] In one embodiment, when the substrate W lands on the support table WT, the negative pressure source 87 is controlled to restart applying negative pressure to extract gas from the gap through a plurality of gas flow openings 69 in the support table WT. After the substrate W lands on the support table WT without a vacuum being formed, the vacuum is applied again.

[0135]

[0147] In one embodiment, the vacuum is gradually increased in stages from a low flow rate to a high flow rate. In particular, in one embodiment, when the substrate W lands on the support table WT, the negative pressure source 87 is controlled to gradually increase the negative pressure in stages such that the flow rate of gas extracted from the gap through a plurality of gas flow openings 69 gradually increases.

[0136]

[0148] Figure 10 shows the vertical height of the substrate W from the support table WT when the substrate W is loaded. The Y-axis represents the vertical height in the Z-direction. The X-axis represents the time it takes to load the substrate W.

[0137]

[0149] Figure 11 shows the pressure measured at different parts of the lithography apparatus over the same period of time during which the substrate W is loaded. The solid line represents the pressure on pin 70. When pin 70 is supporting the substrate W, a negative pressure (i.e., a downward force) is applied to pin 70 due to the weight of the substrate W. When pin 70 no longer supports the substrate W (because the substrate W is fully supported by the support table WT instead of pin 70), the negative pressure disappears. This can be seen on the right side of Figure 11 where the solid line rises to the zero pressure value on the Y axis of the graph. This corresponds to the time when the substrate W is fully supported by the support table WT. This is because, once the substrate W is fully supported by the support table WT, the weight of the substrate W no longer pushes down on pin 70.

[0138]

[0150] The dashed line in Figure 11 represents the pressure on the fluid extraction opening 88 (shown in Figure 7) located around the periphery of the support table WT. When the substrate W is fully supported by the support table WT, a vacuum is created across the fluid extraction opening 88. In Figures 10 and 11, time t0 represents the time when the pin 70 begins to move downward with the substrate W. Time t1 represents the time when the substrate W lands on the support table WT. Time t2 represents the time when the substrate W is fully supported by the support table WT.

[0139]

[0151] The dashed line in Figure 11 represents the negative pressure relative to the gas flow opening 69 of the support table WT. The magnitude of the negative pressure gradually increases after the substrate W lands on the support table WT.

[0140]

[0152] Embodiments of the present invention are expected to improve the clamping accuracy of the substrate W while simultaneously improving throughput. Embodiments of the present invention are expected to enable clamping of a wide range of substrate W types. For example, some substrates W are flat, while others are more warped (i.e., less flat). As described above, after the substrate W lands on the support table WT, the vacuum is gradually increased in stages from a low flow rate to a high flow rate. Flat substrates W with little to moderate warping can be clamped at the lowest possible flow rate, thus improving the positional accuracy of the substrate W relative to the support table WT. Highly warped substrates W that cannot be clamped at the lowest flow rate can be clamped at a later point when the flow rate has increased.

[0141]

[0153] Embodiments of the present invention are expected to improve the positional accuracy of clamping a substrate W onto a support table WT, particularly for new substrates W (i.e., substrates W that have not yet been used). Commonly used substrates W are known to be somewhat less sensitive to positional inaccuracies during clamping.

[0142]

[0154] One embodiment of the present invention includes a loading sequence for a substrate W that utilizes several different pre-clamp flows. This not only allows different types of substrates W to be clamped but also results in a dynamic substrate loading that gives the possibility of optimizing positional accuracy and throughput. It is possible to turn the pre-clamped vacuum on and off at a constant vertical position of pin 70. In an alternative embodiment, the controller 500 is configured to control a negative pressure source 87 to change the negative pressure based on a constant pressure level. For example, the pressure level can be measured by a pressure sensor 85 (shown in Figure 8).

[0143]

[0155] A loading sequence in which the vacuum is turned off when pin 70 is just above the height of the support table WT can be combined with the aforementioned loading sequences in which gas is extracted from different regions of the gas flow opening 69 at different stages of loading. In particular, in one embodiment, the first, second, and third stages of loading described above occur when the substrate W lands on the support table WT. In this way, the flow rate gradually increases when the substrate W lands on the support table WT. However, before the substrate W lands on the support table WT, gas is extracted while the substrate W is descending, and the vacuum is turned off when the substrate W reaches a predetermined distance above the support table WT.

[0144]

[0156] A load sequence that turns off the vacuum when pin 70 is just above the height of the support table WT is feasible for any type of support table WT. The support table shown in Figure 5 above, which has three separate vacuum areas, is just one example of a usable type of support table WT. Other usable support table WTs may have, for example, only one or two vacuum areas.

[0145]

[0157] In one embodiment, the lithography apparatus includes a controller 500 configured to control a gas flow system 97. The controller 500 can execute the sequence of applied pressures described above.

[0146]

[0158] Many of the examples above have been described in relation to immersion lithography apparatus. However, the present invention is also applicable to dry lithography apparatus. As can be understood, any of the above features can be used in conjunction with other features, and this application covers not only the combinations specified.

[0147]

[0159] The following clauses represent alternative configurations for lithography according to the present invention. Clause 1. A method for unloading a substrate from a support table configured to support the substrate, the method being: This includes supplying gas to the gap between the base surface of the support table and the substrate through multiple gas flow openings in the support table, In the initial stages of unloading, gas is supplied from at least one gas flow opening in the outer region of the support table, and not from a gas flow opening in the central region of the support table located radially inward from the outer region. A method in which, during the later stages of unloading, gas is supplied from at least one gas flow opening in the outer region and at least one gas flow opening in the central region. Clause 2. In the initial stage of unloading, gas is supplied from at least one gas flow opening in the outer region, and not from the gas flow opening in the central region, nor from the gas flow opening in the intermediate region of the support table, which is radially inward of the outer region and radially outward of the central region. During the intermediate stage of unloading, gas is supplied from at least one gas flow opening in the outer region and at least one gas flow opening in the intermediate region, but not from the gas flow opening in the central region. The method according to Clause 1, wherein in the later stages of unloading, the gas is supplied from at least one gas flow opening in the outer region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the central region. Clause 3. The method according to Clause 2, wherein, in an intermediate stage of unloading, gas is supplied from at least one gas flow opening in the intermediate region at a first pressure greater than the ambient pressure, and thereafter, gas is supplied from at least one gas flow opening in the intermediate region at a second pressure less than the first pressure. Clause 4. The method according to any one of Clauses 1 to 3, wherein in the initial stage of unloading, gas is supplied from at least one gas flow opening in the outer region at a first pressure greater than the ambient pressure, and thereafter, gas is supplied from at least one gas flow opening in the outer region at a second pressure less than the first pressure. Clause 5. The method according to any one of Clauses 1 to 4, wherein in the later stage of unloading, gas is supplied from at least one gas flow opening in the central region at a first pressure greater than the ambient pressure, and then gas is supplied from at least one gas flow opening in the central region at a second pressure less than the first pressure. Clause 6. A method for loading a substrate onto a support table configured to support the substrate, the method being: This includes extracting gas from the gap between the base surface of the support table and the substrate through multiple gas flow openings in the support table, In the first stage of loading, gas extraction is performed from at least one gas flow opening in the central region of the support table, and not from gas flow openings in the intermediate region of the support table located radially outside the central region, nor from gas flow openings in the outer region of the support table located radially outside the intermediate region. In the second stage of loading, gas extraction is performed from at least one gas outlet in the central region and at least one gas outlet in the intermediate region, but not from the gas outlet in the outer region. A method in which, in the third stage of loading, gas extraction is performed from at least one gas outlet in the central region, at least one gas outlet in the intermediate region, and at least one gas outlet in the outer region. Clause 7. The method according to Clause 6, wherein in the first stage of loading, a supply of gas at a pressure greater than the ambient pressure is provided from at least one gas outlet in the intermediate region and / or at least one gas outlet in the outer region. Clause 8. The method according to Clause 6 or 7, wherein in the second stage of loading, the gas supply is carried out from at least one gas flow opening in the outer region at a pressure greater than the ambient pressure. Clause 9. When the substrate is lowered toward the support table, gas extraction is performed from at least one gas flow opening in the central region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the outer region. When the substrate reaches a predetermined distance above the support table, gas extraction is not performed from any of the gas flow openings in the central region, the intermediate region, or the outer region. The method according to any one of the clauses 6 to 8, wherein the first stage of loading, the second stage of loading, and the third stage of loading are performed when the substrate is placed on a support table. Clause 10. The method of any one of Clauses 2 to 9, including restricting the gas flow between the central region and the intermediate region so that gas can be extracted or supplied to the gaps of the central region and the intermediate region substantially independently. Clause 11. The method according to any one of Clauses 2 to 10, wherein the intermediate region surrounds the central region. Clause 12. The method according to any one of Clauses 2 to 11, wherein the intermediate region is defined by an intermediate region wall projecting above the base plane and restricting the gas flow between the intermediate region and the outer region. Clause 13. The method according to any of Clauses 2 to 11, wherein the intermediate region includes multiple non-overlapping intermediate sub-regions that restrict the gas flow between them. Clause 14. The method according to Clause 13, wherein each intermediate sub-region is defined by an intermediate sub-region wall that protrudes above the base surface and restricts the gas flow between the intermediate region and the central or outer region. Clause 15. The intermediate sub-regions are separated from each other, as described in Clause 13 or 14. Clause 16. The method according to Clauses 13 to 15, wherein gas can be extracted or supplied substantially independently of each other to the respective gaps of the intermediate sub-regions. Clause 17. The method of any of Clauses 2 to 16, including restricting the gas flow between the intermediate region and the outer region so that gas can be extracted or supplied to the gaps of the intermediate region and the outer region substantially independently. Clause 18. The method according to any one of Clauses 2 to 17, wherein the outer region surrounds the intermediate region. Clause 19. The method according to any one of Clauses 1 to 18, comprising restricting the gas flow between the central region and the outer region so that gas extraction or supply to the respective gaps of the central region and the outer region can be performed substantially independently. Clause 20. The method according to any one of Clauses 1 to 19, wherein the central region is defined by a central region wall that protrudes above the base surface of the support table and restricts the gas flow between the central region and the outer region. Clause 21. The method according to any one of Clauses 1 to 19, wherein the central region includes multiple non-overlapping central sub-regions that restrict gas flow between them. Clause 22. The method according to Clause 21, wherein each central sub-region is defined by a central sub-region wall that protrudes above the base surface and restricts the gas flow between the central region and the outer region. Clause 23. The method according to Clause 21 or 22, wherein the central sub-regions are spaced apart from each other. Clause 24. The method according to Clauses 21 to 23, wherein gas can be extracted or supplied substantially independently of each other to the respective gaps in the central sub-regions. Clause 25. The method according to any one of Clauses 1 to 24, wherein the outer region is defined by an outer region wall projecting above the base plane and restricting the gas flow between the outer region and a region radially outside the outer region. Clause 26. The method according to any of Clauses 1 to 24, wherein the outer region includes a plurality of non-overlapping outer sub-regions that restrict the gas flow between them. Clause 27. The method according to Clause 26, wherein each outer sub-region is defined by an outer sub-region wall that protrudes above the base surface and restricts the gas flow between the outer region and a region radially outside the outer region. Clause 28. The outer sub-regions are spaced apart from each other, as described in Clause 26 or 27. Clause 29. The method according to Clauses 26 to 28, wherein gas can be extracted or supplied substantially independently of each other to the respective gaps in the outer sub-regions. Article 30. Gas flow system and, A controller configured to control a gas flow system, A lithography apparatus comprising a support table configured to support a substrate, The support table is Base surface and The central region and, The outer region located radially outside the central region, The gas flow system comprises a plurality of gas flow openings configured to supply gas to the gap between the base surface and the substrate, When the circuit board is unloaded from the support table, In the initial stages of unloading, the controller is configured to control the gas flow system so that gas is supplied from at least one gas flow opening in the outer region and not from the gas flow opening in the central region. A lithography apparatus configured such that, in the later stages of unloading, the controller controls the gas flow system to supply gas from at least one gas flow opening in the outer region and at least one gas flow opening in the central region. Clause 31. The support table comprises an intermediate region located radially outward from the central region and radially inward from the outer region. When the circuit board is unloaded from the support table, In the initial stages of unloading, the controller is configured to control the gas flow system so that gas is supplied from at least one gas flow opening in the outer region, and not from the gas flow openings in the central region and the intermediate region. During the intermediate stage of unloading, the controller is configured to control the gas flow system so that gas is supplied from at least one gas flow opening in the outer region and at least one gas flow opening in the intermediate region, but not from the gas flow opening in the central region. The lithography apparatus according to Clause 30, wherein in the later stages of unloading, the controller is configured to control the gas flow system so that gas is supplied from at least one gas flow opening in the outer region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the central region. Clause 32. The lithography apparatus according to Clause 31, wherein, in an intermediate stage of unloading, the controller is configured to control the gas flow system so that, after supplying gas from at least one gas flow opening in the intermediate region at a first pressure greater than the ambient pressure, the gas is then supplied from at least one gas flow opening in the intermediate region at a second pressure less than the first pressure. Clause 33. A lithography apparatus according to any one of Clauses 30 to 32, wherein, in the initial stage of unloading, the controller is configured to control the gas flow system so that gas is supplied from at least one gas flow opening in the outer region at a first pressure greater than the ambient pressure, and then gas is supplied from at least one gas flow opening in the outer region at a second pressure less than the first pressure. Clause 34. A lithography apparatus according to any one of Clauses 30 to 33, wherein in the later stages of unloading, the controller is configured to control the gas flow system so that after supplying gas from at least one gas flow opening in the central region at a first pressure greater than the ambient pressure, the gas is supplied from at least one gas flow opening in the central region at a second pressure less than the first pressure. Article 35. Gas flow system and, A controller configured to control a gas flow system, A lithography apparatus comprising a support table configured to support a substrate, wherein the support table is Base surface and The central region and, The intermediate region located radially outside the central region, The outer region located radially outside the intermediate region, The gas flow system comprises a plurality of gas flow openings configured for use in extracting gas from the gap between the base surface and the substrate, When the substrate is loaded onto the support table, In the first stage of loading, the controller is configured to control the gas flow system so that gas is extracted from at least one gas flow opening in the central region, but not from the gas flow openings in the intermediate region and the outer region. In the second stage of loading, the controller is configured to control the gas flow system so that gas is extracted from at least one gas flow opening in the central region and at least one gas flow opening in the intermediate region, but not from the gas flow opening in the outer region. A lithography apparatus configured such that, in the third stage of loading, the controller controls the gas flow system to extract gas from at least one gas flow opening in the central region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the outer region. Clause 36. The lithography apparatus according to Clause 35, wherein in the first stage of loading, the controller is configured to control the gas flow system so that gas at a pressure greater than the ambient pressure is supplied from at least one gas flow opening in the intermediate region and / or at least one gas flow opening in the outer region. Clause 37. The lithography apparatus according to Clause 35 or 36, wherein in the second stage of loading, the controller is configured to control the gas flow system so that the gas is supplied from at least one gas flow opening in the outer region at a pressure greater than the ambient pressure. Clause 38. When the substrate is lowered toward the support table, the controller is configured to control the gas flow system so that gas is extracted from at least one gas flow opening in the central region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the outer region. When the substrate reaches a predetermined distance above the support table, the controller is configured to control the gas flow system so that gas is not extracted from any of the central gas flow openings, intermediate gas flow openings, or outer gas flow openings. A lithography apparatus according to any one of clauses 35 to 37, wherein when the substrate lands on a support table, the controller is configured to control the gas flow system to perform a first stage of loading, a second stage of loading, and a third stage of loading. Clause 39. A lithography apparatus according to either Clause 31 or 37, wherein the central region is defined by a central region wall that protrudes above the base surface and is configured to restrict the gas flow between the central region and the intermediate region so that gas can be supplied to or extracted from the gaps of the central region and the intermediate region substantially independently. Clause 40. A lithography apparatus according to any one of Clauses 31 to 39, wherein the intermediate region surrounds the central region. Clause 41. A lithography apparatus according to any one of Clauses 31 to 40, wherein the intermediate region is defined by an intermediate region wall projecting above the base plane and restricting the gas flow between the intermediate region and the outer region. Clause 42. A lithography apparatus according to any one of Clauses 31 to 40, wherein the intermediate region comprises multiple non-overlapping intermediate sub-regions, each intermediate sub-region being defined by an intermediate sub-region wall projecting above the base plane and restricting the gas flow between the intermediate region and the outer region so that gas can be supplied to or extracted from the gaps of the intermediate region and the outer region substantially independently. Clause 43. A lithography apparatus according to Clause 42, wherein the intermediate sub-regions are spaced apart from each other. Clause 44. The lithography apparatus according to Clause 42 or 43, wherein the gas flow system is configured to extract or supply gas to each gap in the intermediate sub-region substantially independently of each other. Clause 45. A lithography apparatus according to any one of Clauses 31 to 44, wherein the outer region surrounds the intermediate region. Article 46. The gas flow system, A central channel connected to at least one gas flow opening in the central region, It comprises an outer channel connected to at least one gas flow opening in the outer region, A lithography apparatus according to any one of clauses 30 to 45, wherein the central channel is independent of the outer channel. Article 47. The gas flow system, A central channel connected to at least one gas flow opening in the central region, An intermediate channel connected to at least one gas flow opening in the intermediate region, It comprises an outer channel connected to at least one gas flow opening in the outer region, A lithography apparatus according to any one of the clauses 31 to 45, wherein the central channel, intermediate channel, and outer channel are independent of each other. Clause 48. Lithography apparatus according to Clause 46 or 47, wherein the gas flow system comprises at least one piezoelectric valve configured to change the flow rates of a central flow channel, an intermediate flow channel, and / or an outer flow channel. Clause 49. The system comprises at least one pressure sensor configured to sense the pressure in the central channel, intermediate channel, and / or outer channel, A lithography apparatus according to any one of clauses 46 to 48, wherein the controller is configured to change the flow rate of the central channel, intermediate channel, and / or outer channel based on the pressure sensed by a pressure sensor. Clause 50. A lithography apparatus according to any one of Clauses 30 to 49, wherein the central region is defined by a central region wall that protrudes above the base surface and is configured to restrict the gas flow between the central region and the outer region so that gas can be supplied to or extracted from the gaps of the central region and the outer region substantially independently. Clause 51. A lithography apparatus according to any one of Clauses 30 to 49, wherein the central region comprises a plurality of non-overlapping central subregions, each central subregion being defined by a central subregion wall projecting above the base plane and restricting the gas flow between the central and outer regions so that gas can be supplied to or extracted from the respective gaps between the central and outer regions substantially independently. Clause 52. The lithography apparatus according to Clause 51, wherein the central subregions are spaced apart from each other. Clause 53. The lithography apparatus according to Clause 51 or 52, wherein the gas flow system is configured to extract or supply gas to each gap in the central sub-region substantially independently of each other. Clause 54. Lithography apparatus according to any one of Clauses 30 to 53, wherein the outer region is defined by an outer region wall projecting above the base plane and restricting gas flow between the outer region and a region radially outside the outer region. Clause 55. A lithography apparatus according to any one of Clauses 30 to 54, wherein the outer region includes a plurality of non-overlapping outer sub-regions that restrict gas flow between them, and each outer sub-region is defined by an outer sub-region wall that protrudes above the base plane and restricts gas flow between the central region and the outer region. Clause 56. The lithography apparatus according to Clause 55, wherein the outer subregions are spaced apart from each other. Clause 57. The lithography apparatus according to Clause 55 or 56, wherein the gas flow system is configured to extract or supply gas to each gap in the outer sub-region substantially independently of each other. Article 58. A method for loading a substrate onto a support table configured to support the substrate, the method being: Lowering the circuit board towards the support table, When lowering the substrate toward the support table, a negative pressure source is controlled to apply negative pressure in order to extract gas from the gap between the base surface of the support table and the substrate through multiple gas flow openings in the support table. When the substrate reaches a predetermined distance above the support table, control the negative pressure source that is in fluid communication with one of the gas flow openings of the support table to stop applying negative pressure, and A method comprising controlling a negative pressure source to restart applying negative pressure in order to extract gas through multiple gas flow openings in a support table when the substrate lands on the support table. Clause 59. The method of Clause 58, wherein the negative pressure source is controlled to gradually increase the negative pressure in multiple stages, such that the gas flow extracted from the gap through multiple gas flow openings gradually increases when the substrate lands on the support table. Clause 60. A gas flow system equipped with a negative pressure source, A controller configured to control a gas flow system, A lithography apparatus comprising a support table configured to support a substrate, When the substrate is lowered toward the support table, the controller is configured to control a negative pressure source and apply negative pressure to extract gas from the gap between the support table and the substrate through multiple gas flow openings in the support table. When the substrate reaches a predetermined distance above the support table, the controller is configured to control a negative pressure source that is in fluid communication with one of the gas flow openings in the support table, thereby stopping the application of negative pressure. A lithography apparatus configured such that, when the substrate lands on the support table, the controller controls a negative pressure source to restart applying negative pressure in order to extract gas through multiple gas flow openings in the support table. Article 61. A method for loading a substrate onto a support table configured to support the substrate, the method being: This includes extracting gas from the gap between the base surface of the support table and the substrate through multiple gas flow openings in the support table, In the first stage of loading, gas extraction is performed from at least one gas flow opening in the outer region of the support table, and not from the gas flow opening in the intermediate region of the support table located radially inward from the outer region, nor from the gas flow opening in the central region of the support table located radially inward from the intermediate region. In the second stage of loading, gas extraction is performed from at least one gas flow opening in the outer region and at least one gas flow opening in the intermediate region, but not from the gas flow opening in the central region. A method in which, in the third stage of loading, gas extraction is performed from at least one gas flow opening in the outer region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the central region. Clause 62. Gas flow system and, A controller configured to control a gas flow system, A lithography apparatus comprising a support table configured to support a substrate, wherein the support table is Base surface and The central region and, The intermediate region located radially outside the central region, The outer region located radially outside the intermediate region, The gas flow system comprises a plurality of gas flow openings configured for use in extracting gas from the gap between the base surface and the substrate, Each area A gas flow opening in that region and a fluid channel that communicates with it, It comprises a pressure sensor configured to sense the pressure in the flow path, A lithography apparatus configured such that, when a substrate is loaded onto a support table, the controller controls the timing of gas extraction from gas flow openings in each region based on the pressure of each channel it senses. Clause 63. At least one of the regions includes subregions distributed in multiple tangential directions, each subregion being: The gas flow opening in that sub-region and the fluid flow path that communicates with it, It comprises a pressure sensor configured to sense the pressure in the flow path, The lithography apparatus according to Clause 62, wherein, when a substrate is loaded onto a support table, the controller is configured to control the timing of gas extraction from the gas flow openings of each sub-region based on the pressure of each sensed flow path.

[0148]

[0160] As can be understood, any of the above features can be used in conjunction with other features, and this application does not cover only the combinations specified. One embodiment of the present invention can be applied, for example, to the embodiment shown in Figure 3. Furthermore, although the embodiments of the present invention have been described in relation to immersion lithography apparatus for convenience, it will be understood that the embodiments of the present invention can be used with any form of lithography apparatus.

[0149]

[0161] In light of these alternative uses, it will be recognized by those skilled in the art that where the terms “wafer” or “die” are used herein, they may be considered synonymous with the more general terms “substrate” or “target portion,” respectively. The substrates described herein may be processed before or after exposure with, for example, a track (usually a tool for coating a layer of resist onto the substrate and developing the exposed resist), metrology tools, and / or inspection tools. Where appropriate, the disclosure herein may be applied to the above and other substrate processing tools. Furthermore, the substrate may be processed multiple times, for example to produce a multilayer IC, and therefore the term substrate as used herein may also refer to a substrate that already contains multiple processed layers.

[0150]

[0162] As used herein, the terms “radiation” and “beam” encompass all types of electromagnetic radiation, including ultraviolet (UV) radiation (e.g., having wavelengths of 365 nm, 248 nm, 193 nm, 157 nm, or 126 nm, or around these wavelengths). The term “lens” refers, where circumstances permit, to one or a combination of various types of optical components, including refractive and reflective optical components.

[0151]

[0163] While specific embodiments of the present invention have been described above, it will be understood that the present invention can be implemented in ways other than those described. The above description is illustrative and not limiting. Accordingly, it will be apparent to those skilled in the art that modifications can be made to the described invention without departing from the claims set forth below.

Claims

1. A method for unloading a substrate from a support table configured to support the substrate, This includes supplying gas to the gap between the base surface of the support table and the substrate through a plurality of gas flow openings in the support table, In the initial stage of unloading, the gas is supplied from at least one gas flow opening in the outer region of the support table, and not from a gas flow opening in the central region of the support table located radially inward from the outer region. A method wherein, in the later stages of unloading, the gas is supplied from at least one gas flow opening in the outer region and at least one gas flow opening in the central region.

2. In the initial stage of the unloading process, the gas is supplied from at least one gas flow opening in the outer region, and not from the gas flow opening in the central region, nor from the gas flow opening in the intermediate region of the support table, which is located radially inward of the outer region and radially outward of the central region. During the intermediate stage of unloading, the gas is supplied from at least one gas flow opening in the outer region and at least one gas flow opening in the intermediate region, but not from the gas flow opening in the central region. The method according to claim 1, wherein in the later stage of the unloading, the gas is supplied from at least one gas flow opening in the outer region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the central region.

3. The method according to claim 2, wherein, in an intermediate stage of the unloading, gas is supplied from at least one gas flow opening in the intermediate region at a first pressure greater than the ambient pressure, and thereafter, gas is supplied from at least one gas flow opening in the intermediate region at a second pressure less than the first pressure.

4. A method for loading a substrate onto a support table configured to support the substrate, This includes extracting gas from the gap between the base surface of the support table and the substrate through a plurality of gas flow openings in the support table, In the first stage of loading, the gas is extracted from at least one gas flow opening in the central region of the support table, and not from the gas flow opening in the intermediate region of the support table located radially outside the central region or from the gas flow opening in the outer region of the support table located radially outside the intermediate region. In the second stage of loading, the gas extraction is performed from at least one gas outlet in the central region and at least one gas outlet in the intermediate region, but not from the gas outlet in the outer region. A method in which, in the third stage of loading, the gas is extracted from at least one gas outlet in the central region, at least one gas outlet in the intermediate region, and at least one gas outlet in the outer region.

5. The method according to claim 4, wherein in the first stage of the load, a gas at a pressure greater than the ambient pressure is supplied from at least one gas outlet in the intermediate region and / or at least one gas outlet in the outer region.

6. When the substrate is lowered toward the support table, the gas is extracted from at least one gas outlet in the central region, at least one gas outlet in the intermediate region, and at least one gas outlet in the outer region. When the substrate reaches a predetermined distance above the support table, the gas extraction is not performed from any of the gas outlets in the central region, the intermediate region, or the outer region. The method according to claim 4 or 5, wherein the first stage of loading, the second stage of loading, and the third stage of loading are performed when the substrate lands on the support table.

7. The aforementioned intermediate region surrounds the aforementioned central region, or The aforementioned intermediate region includes a plurality of non-overlapping intermediate sub-regions that restrict the gas flow between them, and / or The method according to any one of claims 2 to 6, wherein the outer region surrounds the intermediate region.

8. The method according to any one of claims 1 to 7, wherein the outer region includes a plurality of non-overlapping outer sub-regions that restrict gas flow between them.

9. A method for loading a substrate onto a support table configured to support the substrate, Lowering the substrate toward the support table, When the substrate is lowered toward the support table, a negative pressure source is controlled to apply negative pressure in order to extract gas from the gap between the base surface of the support table and the substrate through multiple gas flow openings in the support table. When the substrate reaches a predetermined distance above the support table, control the negative pressure source that is in fluid communication with one of the gas flow openings of the support table to stop applying negative pressure, and A method comprising controlling the negative pressure source to resume applying negative pressure in order to extract the gas through a plurality of gas flow openings in the support table when the substrate lands on the support table.

10. The method according to claim 9, wherein when the substrate lands on the support table, the negative pressure source is controlled to gradually increase the negative pressure in several stages so that the flow rate of gas extracted from the gap through the plurality of gas flow openings gradually increases.

11. A method for loading a substrate onto a support table configured to support the substrate, This includes extracting gas from the gap between the base surface of the support table and the substrate through a plurality of gas flow openings in the support table, In the first stage of loading, the gas is extracted from at least one gas flow opening in the outer region of the support table, and not from the gas flow opening in the intermediate region of the support table located radially inward from the outer region, and not from the gas flow opening in the central region of the support table located radially inward from the intermediate region. In the second stage of loading, the gas extraction is performed from at least one gas flow opening in the outer region and at least one gas flow opening in the intermediate region, but not from the gas flow opening in the central region. A method wherein, in a third stage of loading, the gas is extracted from at least one gas outlet in the outer region, at least one gas outlet in the intermediate region, and at least one gas outlet in the central region.

12. Gas flow system and, A controller configured to control the gas flow system, A lithography apparatus comprising a support table configured to support a substrate, wherein the support table is Base surface and The central region and, The outer region located radially outside the central region, The gas flow system comprises a plurality of gas flow openings configured to supply gas to the gap between the base surface and the substrate, When the substrate is unloaded from the support table, In the initial stages of unloading, the controller is configured to control the gas flow system so that the gas is supplied from at least one gas flow opening in the outer region and not from the gas flow opening in the central region. A lithography apparatus in which, in the later stages of unloading, the controller is configured to control the gas flow system so that the gas is supplied from at least one gas flow opening in the outer region and at least one gas flow opening in the central region.

13. Gas flow system and, A controller configured to control the gas flow system, A lithography apparatus comprising a support table configured to support a substrate, wherein the support table is Base surface and The central region and, The intermediate region located radially outside the central region, The outer region located radially outside the aforementioned intermediate region, The gas flow system comprises a plurality of gas flow openings configured to be used to extract gas from the gap between the base surface and the substrate, When the substrate is loaded onto the support table, In the first stage of loading, the controller is configured to control the gas flow system such that the gas is extracted from at least one gas flow opening in the central region, but not from the gas flow openings in the intermediate region and the gas flow openings in the outer region. In the second stage of loading, the controller is configured to control the gas flow system such that the gas is extracted from at least one gas flow opening in the central region and at least one gas flow opening in the intermediate region, but not from the gas flow opening in the outer region. A lithography apparatus, wherein in a third stage of loading, the controller is configured to control the gas flow system so that the gas is extracted from at least one gas flow opening in the central region, at least one gas flow opening in the intermediate region, and at least one gas flow opening in the outer region.

14. A gas flow system equipped with a negative pressure source, A controller configured to control the gas flow system, A lithography apparatus comprising a support table configured to support a substrate, When the substrate is lowered toward the support table, the controller is configured to control the negative pressure source to apply negative pressure in order to extract gas from the gap between the support table and the substrate through a plurality of gas flow openings in the support table. When the substrate reaches a predetermined distance above the support table, the controller is configured to control the negative pressure source, which is in fluid communication with one of the gas flow openings of the support table, and stop applying negative pressure. A lithography apparatus configured such that when the substrate lands on the support table, the controller controls the negative pressure source to resume applying negative pressure in order to extract the gas through a plurality of gas flow openings in the support table.

15. Gas flow system and, A controller configured to control the gas flow system, A lithography apparatus comprising a support table configured to support a substrate, wherein the support table is Base surface and The central region and, The intermediate region located radially outside the central region, The outer region located radially outside the aforementioned intermediate region, The gas flow system comprises a plurality of gas flow openings configured to be used to extract gas from the gap between the base surface and the substrate, Each area is, A flow path that communicates with the gas flow opening in that region, A pressure sensor configured to sense the pressure in that region is provided, A lithography apparatus configured such that, when the substrate is loaded onto the support table, the controller controls the timing of gas extraction from the gas flow openings in each region based on the pressure of each region that it senses.

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