Lithography equipment and cooling equipment

Abstract

The lithographic apparatus comprises: a projection system configured to project a patterned radiation beam via a projection path onto an exposure zone at a substrate held on a substrate stage, the substrate stage being movable in a region below the projection system; and a cooling apparatus configured to cool the substrate via heat transfer from the substrate to a cooling element, the cooling element being located above the substrate and adjacent to the projection path; wherein the cooling apparatus comprises a diaphragm system located in the projection path to physically separate the projection system from the region.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 18182013.5 filed on July 5, 2018, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a photolithography apparatus and a photolithography method. The present invention also relates to a cooling device. Background Art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern to a substrate. For example, a lithographic apparatus may be used in the manufacture of integrated circuits (ICs). For example, a lithographic apparatus may project a pattern at a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) disposed on a substrate.

[0005] To project a pattern on a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of the radiation determines the minimum size of features that can be formed on the substrate. A lithographic apparatus using extreme ultraviolet (EUV) radiation with a wavelength in the range of 4nm-20nm (e.g., 6.7nm or 13.5nm) may be used to form smaller features on a substrate than, for example, a lithographic apparatus using radiation with a wavelength of 193nm.

[0006] There is a risk that contaminants from the substrate (eg gas phase organic compounds from the resist on the substrate) reach the optical components of the lithographic apparatus (ie the projection system).

[0007] It is desirable to provide a lithographic apparatus that solves the above-mentioned problems or some other problems associated with the prior art. Summary of the invention

[0008] According to a first aspect of the present invention, there is provided a lithographic apparatus comprising: a projection system configured to project a patterned radiation beam via a projection path onto an exposure zone at a substrate held on a substrate stage, the substrate stage being movable in a region below the projection system; and a cooling device configured to cool the substrate via heat transfer from the substrate to a cooling element, the cooling element being located above the substrate and adjacent to the projection path; wherein the cooling device comprises a diaphragm system located in the projection path to physically separate the projection system from the region.

[0009] This has the advantage of isolating the projection system from the area so that gases and / or contaminants cannot enter the projection system from this area. Advantages compared to other systems may be the elimination of parasitic heat loads, associated heat shields, tuning solutions and reduced pumping power.

[0010] The gas flow system may be configured to provide a flow of gas beneath the membrane system. This may provide the advantage of increasing the travel height of the cooling device.

[0011] The gas flow system may be configured to provide a flow of gas between the cooling element and the substrate, the flow may be configured to increase heat transfer from the substrate to the cooling element.

[0012] The gas flow system may be configured to provide a gas flow onto an exposure region on the substrate.

[0013] The gas flow system may include a gas delivery conduit in the cooling device.

[0014] The gas may comprise nitrogen. This has the advantage that nitrogen is five times more stable than hydrogen with respect to the thermal adaptation coefficient (TAC) of different surface materials.

[0015] The lithographic apparatus may further comprise an additional gas flow system which may be configured to provide a flow of an additional gas over the membrane system. This may avoid contamination at the membrane.

[0016] The diaphragm system may comprise a single diaphragm. An advantage may be providing a more robust diaphragm.

[0017] The diaphragm system may include a first diaphragm and a second diaphragm.

[0018] The lithographic apparatus may further comprise a further gas flow system which may be configured to provide a further gas flow through the volume defined by the cooling device, the first membrane and the second membrane. This may provide the advantage of increasing cooling of one or both membranes.

[0019] The lithographic apparatus may further include a blocking member located at a periphery of the cooling apparatus and extending outwardly and / or upwardly from the cooling apparatus.

[0020] The blocking member may be connected to the cooling device.

[0021] The cooling device may include a slit configured such that the projected path passes through the slit, wherein the diaphragm system may physically close the slit.

[0022] The cooling element may comprise fingers extending away from the body of the cooling element towards the substrate, wherein the membrane system may be located between the fingers. This may have the advantage of providing a better cooling flow distribution underneath the membrane for cleaning purposes.

[0023] The gas flow system may be configured to provide a gas flow out from the fingers.

[0024] According to a second aspect of the present invention, there is provided a cooling device, the cooling device being configured for use in a lithography apparatus as described above. According to a third aspect of the present invention, there is provided a lithography method, comprising: projecting a patterned radiation beam through a projection system via a projection path to form an exposure region on a substrate held on a substrate stage; and cooling the substrate using the cooling device via a cooling element, the cooling element being used to remove heat from the substrate, the cooling element being located above the substrate and adjacent to the projection path, wherein the cooling device comprises a diaphragm system located in the projection path to physically separate the projection system from the region.

[0025] The photolithographic method may further include providing a flow of a gas from a gas flow system below the membrane system.

[0026] The lithographic method may further include providing a flow of a gas between the cooling element and the substrate, the flow may be configured to increase heat transfer from the substrate to the cooling element.

[0027] The lithographic method may further comprise providing a flow of an additional gas from a further gas system through the volume defined by the cooling device, the first membrane and the second membrane of the membrane system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0029] - Figure 1 A lithography system including a lithography apparatus and a radiation source according to an embodiment of the present invention is shown;

[0030] - Figure 2 shows a schematic cross-sectional side view of a cooling device and a barrier member above a substrate according to an embodiment of the present invention;

[0031] - Figure 3 shows a schematic cross-sectional view of a cooling device, a blocking member and a funnel according to an embodiment of the present invention;

[0032] - Figure 4a A perspective view showing a cooling device above a substrate according to an embodiment of the present invention;

[0033] - Figure 4b A perspective view showing a cooling device above a substrate according to an embodiment of the present invention;

[0034] - Figure 5 shows a schematic cross-sectional side view of a cooling device according to an embodiment of the present invention;

[0035] - Figure 6 The embodiment according to the present invention is shown along Figure 5A cross-sectional view of the cooling device taken along line AA'. DETAILED DESCRIPTION

[0036] Figure 1 A lithographic system is shown comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and to provide the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g. a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

[0037] The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA. Furthermore, the illumination system IL may include a faceted field mirror arrangement 10 and a faceted pupil mirror arrangement 11. The faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11 together provide a desired cross-sectional shape and a desired intensity distribution for the EUV radiation beam B. The illumination system IL may include other mirrors or arrangements in addition to or instead of the faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11.

[0038] After being so adjusted, the EUV radiation beam B interacts with the pattern forming device MA. The result of this interaction is the generation of a patterned EUV radiation beam B'. The projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. To this end, the projection system PS may include a plurality of mirrors 13, 14, which are configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thereby forming an image having features that are smaller than corresponding features on the pattern forming device MA. For example, a reduction factor of 4 or 8 may be applied. Although in Figure 1 The projection system PS is shown with only two mirrors 13, 14, but the projection system PS may comprise a different number of mirrors (eg six mirrors or eight mirrors).

[0039] The substrate W may include a previously formed pattern. In this case, the lithographic apparatus LA aligns the image formed by the patterned EUV radiation beam B′ with the pattern previously formed on the substrate W.

[0040] A relative vacuum, ie a small amount of gas (eg hydrogen) at a pressure well below atmospheric pressure, may be provided in the radiation source SO, in the illumination system IL and / or in the projection system PS.

[0041] The radiation source SO may be a laser produced plasma (LPP) source, a discharge produced plasma (DPP) source, a free electron laser (FEL) or any other radiation source capable of generating EUV radiation.

[0042] The projection system PS is configured to project a patterned EUV radiation beam B' via a projection path onto an exposure area on the substrate W. The substrate table WT is movable in a region 18 (shown in dashed lines) beneath the projection system PS.

[0043] The lithographic apparatus comprises a cooling device 20 located above the substrate W. The cooling device 20 provides local cooling of the substrate W in the vicinity of the radiation beam B. The cooling device 20 is described in further detail below.

[0044] Figure 2 A cooling device 20 is shown located above the substrate W. The cooling device 20 comprises a first cooling element 22 and a second cooling element 24. In some examples, the cooling device 20 may have a single cooling element. An area 18 in which the substrate table WT may move is schematically shown in dashed lines. The dimensions of the depicted area 18 are only exemplary, and it will be appreciated that the area may have any dimensions as desired, for example, the area 18 may extend further in the y direction.

[0045] exist Figure 2 Cartesian coordinates are shown in , and use the symbols commonly used in lithographic apparatus, i.e. the Y direction is the direction of scanning movement of the substrate W during exposure, the X direction is perpendicular to the Y direction and lies in the plane of the substrate, and the Z direction generally corresponds to the optical axis of the radiation beam B.

[0046] The cooling elements 22, 24 are located on either side of the radiation beam B' in the scanning direction (i.e., in the Y direction). The cooling elements 22, 24 are located above the substrate W and adjacent to the projection path of the patterned EUV radiation beam B'. The cooling elements 22, 24 are adjacent to the exposure area E (i.e., the area on which the radiation beam B is incident). In this context, the term "adjacent" may be interpreted as being less than 1 cm from the edge of the exposure area E. The cooling elements 22, 24 may be less than 0.5 cm from the edge of the exposure area E, and may be approximately 0.1 cm from the edge of the exposure area E. Each cooling element 22, 24 may be configured to cool an area that is 3 cm or less from a line that divides the exposure area E in half. Each cooling element 22, 24 may be configured to cool an area that is 2 cm or less from the edge of the exposure area. In some examples, the first cooling element 22 and the second cooling element 24 may have the same overall construction.

[0047] The cooling elements 22, 24 provide local cooling of the substrate W in the region below the cooling elements 22, 24. Figure 2During scanning exposure of a substrate W (from left to right in FIG. 1 ), the first cooling element 22 cools the portion of the substrate to be exposed by the radiation beam B, and the second cooling element 24 cools the portion of the substrate W that has been exposed by the radiation beam B'. If the scanning exposure is a substrate W moving in the negative Y direction ( Figure 2 ), the second cooling element 24 provides cooling of the portion of the substrate to be exposed by the radiation beam B', and the first cooling element 22 provides cooling of the portion of the substrate W that has been exposed by the radiation beam B'.

[0048] Each cooling element 22, 24 is configured to receive heat from the substrate W and transfer the heat to some other location, for example using a cooling fluid (e.g., water). In this context, the term "cooling fluid" is not intended to imply that the fluid must have a specific temperature, but rather that the fluid carries heat away from the cooling element 22, 24. The cooling fluid passes through cooling conduits 25A, 25B, 25C, 25D in the cooling elements 22, 24. The cooling elements 22, 24 can be maintained at a relatively very low temperature, for example a temperature of -70 degrees Celsius.

[0049] The cooling device 20 can counteract the high heating dose on the substrate W caused by the EUV radiation being incident on the exposure region E of the substrate W.

[0050] Each cooling element 22, 24 comprises a body 26, 27 and fingers 28, 29 extending from their respective bodies 26, 27 towards the substrate W. The fingers 28, 29 define a slit 30. More generally, the cooling device 20 has a slit 30 passing through the cooling device 20. The slit 30 is arranged so that the projected path of the patterned EUV radiation beam B' passes through the slit 30. In other examples, the cooling element may not include fingers, and in this case, the slit may be defined by the body of the cooling element.

[0051] The cooling device 20 includes a membrane system, which in this example is a single membrane 32 located in the slot 30. The membrane 32 is located in the projection path of the patterned EUV radiation beam B'. The slot 30 provides a unique path for contaminants and / or gases, etc. to pass from the region 18 to the projection system PS. The membrane 32 located in the slot 30 physically closes the slot 30. Therefore, the membrane 32 physically separates the projection system PS from the region 18. The cooling device 20 with the membrane 32 can be considered to isolate the region 18 from the projection system PS, and vice versa. A cooling device with a membrane system can be referred to as a cooling mask. In other examples, the membrane system can have more than one membrane, such as Figure 5 shown.

[0052] The lithographic apparatus LA includes a blocking member 34 (also referred to as a tray) located at or around the periphery of the cooling device 20. The blocking member 34 extends outwardly and / or upwardly (e.g., vertically or at an angle) from the cooling device 20. The blocking member 34 may extend to other walls or components of the lithographic apparatus LA, such as a projection optics box (POB) for accommodating the projection system PS. The blocking member 34 may be rigidly connected to these walls or other components of the lithographic apparatus. The blocking member 34 is connected to the cooling device 20 so that no contaminants and / or gases, etc., can be transferred from the region 18 to the projection system PS between the cooling device 20 and the blocking member 34. Therefore, the blocking member 34 and the cooling device 20 with the diaphragm 32 together isolate the region 18 from the projection system PS. In other examples, the blocking member 34 may be integrated with the cooling device 20 so that no contaminants and / or gases can be transferred from the region 18 to the projection system PS. The blocking member and the cooling device with the diaphragm system may be referred to as a cooling mask. In other examples, the blocking member may be only partially located at or around the periphery of the cooling device. In other examples, there may be no separate blocking member, and a separate cooling device may isolate the area from the projection system.

[0053] Unlike cooling devices in other systems that have to move up and down due to dose changes or wafer surface changes, the cooling device 20 with a blocking member 34 is used as a fixed component. In other systems, the cooling element can be held by a support member that includes a mechanism that moves the cooling element to a desired height above the substrate table WT. However, in the lithography device LA with a cooling device 20 as described above, the problem of dose changes or wafer surface changes is solved by flow changes. The stroke height (i.e., the distance between the cooling elements 22, 24 and the wafer W) can be large, so there is no need for movement caused by wafer surface changes. Therefore, there will be no gap between the blocking member 34 and the cooling device 20, and the cooling mask (cooling device 20 and blocking member 34) can be considered to be attached (e.g., bolted or welded) to a main body of the projection optical box (POB).

[0054] Figure 3 FIG. 2 shows a cross-sectional view of the cooling device 20 at a location with the blocking member 34 shown in more detail. Figure 3 1 , but it will be appreciated that they would be located in region 18 below cooling device 20 (also not shown).

[0055] The lithographic apparatus LA includes a funnel 36. The funnel 36 has an approximately truncated cone shape with a hole 36A of a larger diameter at the top and a hole 36B of a smaller diameter at the bottom (the bottom is the end closest to the cooling device 20). The funnel 36 includes an edge 36C extending outward from the hole 36A of the larger diameter. The projection path of the patterned EUV radiation beam B' passes through the hole 36A of the larger diameter and the hole 36B of the smaller diameter. That is, the patterned EUV radiation beam B' passes through the funnel 36 before being incident on the diaphragm 32 in the cooling device 20. The blocking member 34 is attached to the edge 36C of the funnel 36.

[0056] exist Figure 3 In the embodiment, the funnel 36 is shown with a gas delivery conduit 37, which in other systems may be used to supply a gas flow to the substrate. However, in an embodiment, the funnel 36 is not supplied with gas through the gas delivery conduit 37. Moreover, in some embodiments, the funnel 36 may not have a gas delivery conduit. It will be understood that in other examples, the funnel may have different sizes and shapes as long as it provides the function of allowing EUV radiation to pass through a portion of the funnel.

[0057] In an embodiment, funnel 36 may provide a similar function to barrier member 34, either in place of barrier member 34 or in addition to barrier member 34. That is, a shield (or barrier member) is provided to separate region 18 from projection system PS. More specifically, the arrangement may be such that the only path for gas and / or contaminants to travel from region 18 to projection system PS may be through funnel 36. In other embodiments, funnel 36 may not be present, and region 18 may be isolated from projection system PS by other devices (such as barrier member 34 or cooling device 20). Barrier member 34 is connected to cooling device 20 and edge 36C of funnel 36, meaning that projection system PS is isolated from region 18.

[0058] Figure 3 The position of the membrane 32 shown in FIG. 3 is between the fingers 28, 29 of the cooling elements 22, 24. It can be seen that the slit 30 is an aperture in the cooling device 20 to allow the patterned radiation beam B' to pass through the cooling device 20 to impinge on the substrate W below the cooling device 20.

[0059] The use of a diaphragm 32 in the cooling device 20 means that contaminants cannot reach the projection system PS. This means that a relatively high gas flow towards the substrate W to prevent contaminants is not needed, which in other systems can be provided by a gas delivery conduit 37 in the funnel 36 (referred to as a dynamic gas lock - DGL). In other systems, a high gas flow from the DGL is required to inhibit contaminants from reaching the projection system PS. In a high NA (numerical aperture) lithography device LA system, it may be necessary to increase the DGL gas flow to maintain the same contaminant suppression capability as a lower NA system. The use of the diaphragm 32 leads to the elimination of parasitic heat loads that may have occurred due to the DGL (heating on the substrate due to high DGL flow). In addition, the need for related heat shields and adjustment solutions (for example, active cooling and passive cooling) is avoided, which may be required in other systems to thermally control the redirected DGL flow. For example, these may be required to avoid overheating the mirror or cooling the mirror.

[0060] Furthermore, the use of the diaphragm 32 means that pumping power is reduced compared to other systems with a DGL, since the high gas flows previously required by the DGL are not required, or in some embodiments are substantially reduced for current gas flow systems. This can save costs and reduce heat build-up in other components. For example, more than 30% of the pumping capacity can be removed. This also introduces a significant amount of design volume in the lithographic apparatus LA (e.g., which can be used for other components).

[0061] Combining the functions of the DGL and the cooling device of other systems into a single component (i.e., the cooling device 20) can result in better serviceability and higher system availability. This is because, although the DGL and the cooling device are separate modules in other systems, their serviceability is entangled, resulting in longer recovery time, which may result in doubling the machine recovery time.

[0062] The diaphragm 32 may also provide the function of suppressing some of the unwanted EUV or IR radiation that may be reflected from the pellicle and / or mask, thereby preventing at least some of the unwanted radiation from being incident on the substrate W. In other systems, this function may be provided by a diaphragm located elsewhere in the lithographic apparatus (e.g., in the DGL funnel). However, positioning the diaphragm 32 in a slit in the cooling device provides the advantage of reducing the surface area of ​​the diaphragm. This means that the diaphragm 32 is more robust and is less likely to be damaged or broken due to, for example, a pressure difference between the region 18 and the projection system PS. EUV radiation is highly absorbed by the material, so the diaphragm must be thin enough so that the desired amount of EUV radiation can pass through the diaphragm. However, the strength of the diaphragm will decrease as the thickness decreases. Due to the smaller surface area of ​​the diaphragm 32 positioned in the cooling device 20, a more robust diaphragm can be achieved because the strength of the diaphragm will increase as the surface area decreases. In addition, due to the increased strength of the diaphragm 32, a higher pressure difference over the diaphragm 32 can be allowed.

[0063] The cooling device 20 further comprises a gas delivery conduit (not shown) configured to deliver gas to below the membrane 32. The gas delivery conduit may be disposed in the cooling elements 22, 24. A gas flow system (not shown) is configured to provide a gas flow below the membrane 32. The gas delivery conduit is at least partially disposed in the fingers 28, 29 of the cooling elements 22, 24 so that a gas flow is provided from the fingers 28, 29 into the region 18. The fingers 28, 29 have the advantage of providing a better cooling flow distribution below the membrane 32 for cleaning purposes, thereby being able to leave a gap between the fingers 28, 29 and the wafer W. Figure 4a Gap shown.

[0064] like Figure 2 As shown by the arrows in , the gas delivered by the gas delivery conduit flows at least partially through the membrane 32 and flows downwardly from the membrane 32. The gas flow can also flow directly downwardly from the fingers 28, 29 to the substrate W as shown by the arrows.

[0065] Figure 4a The cooling device 20 and the substrate W are shown from above. Figure 4a As shown by the arrows in , the gas can also flow outwardly from between the fingers 28, 29 (ie, from the slits 30) in a substantially horizontal direction (ie, the x-direction). This may be because there is less resistance to movement of the gas in these directions.

[0066] Figure 4b The cooling device 20 and the substrate W are also shown from above. Figure 4bA gas flow from the fingers 28, 29 is shown, first impinging on the substrate W and then passing through the substrate W. The gas flow system is configured to provide the gas flow onto the exposure area E on the substrate W. Generally, the gas can be considered to travel outwardly and be exhausted from underneath the cooling element body 26, 27 to the surrounding environment.

[0067] Thus, it can be seen that the gas flow system provides a gas flow between the cooling elements 22, 24 and the substrate W. This gas flow increases the heat transfer (transfer) from the substrate W to the cooling elements 22, 24. This has the advantage of providing more efficient cooling of the substrate W.

[0068] The gas flow from the cooling device 20 provides enhanced cooling of the substrate W. The gas flow also provides the advantage of more focused cooling (i.e., over the exposure zone E of the substrate W) compared to other systems that do not have a gas flow from the cooling device 20. This provides more efficient cooling compared to other systems that only have cooling elements covering the area around the EUV exposure zone E of the substrate W.

[0069] As previously described, the gas flow also flows at least partially through the diaphragm 32. Thus, the gas flow also provides the advantage of cooling the diaphragm 32, which may have been heated by absorbing some EUV radiation from the patterned beam B' or EUV or IR radiation reflected from the pellicle or mask. When the diaphragm is heated, some heat is radiated toward the substrate W, and some heat can be conducted by any gas below the diaphragm. The diaphragm heating can in turn heat the substrate W and / or the cooling device. Thus, cooling of the diaphragm 32 by the gas flow provides the advantage of helping to avoid additional radiation and heat transfer to the substrate W and / or the cooling device 20.

[0070] The gas flow through the diaphragm 32 can also clean the diaphragm 32 (e.g., remove any particles that may have been deposited there, etc.). The gas flow under and around the diaphragm 32 can address contamination issues at the diaphragm 32, and the gas flow can flow away through one or more gaps perpendicular to the fingers 28, 29.

[0071] Plasma cleaning can be used below the membrane 32, which depends linearly on the EUV radiation power and the gas pressure. The cleaning rate also depends on the type of resist, the membrane material and the cooling gas used.

[0072] There is a small spacing between the bottom of the cooling device 20 (i.e. the bottom of the fingers 28, 29) and the substrate W (also referred to as the stroke height) in order to obtain a desired heat transfer coefficient (HTC) at the fingers that may result in collisions between the fingers and the substrate W. Since the cooling gas is introduced below the membrane 32, the stroke height can be increased to avoid this problem.

[0073] In this example, the gas is nitrogen (N2). A membrane 32 having a slit 30 isolates the region 18 from the projection system PS where hydrogen (H2) may be present. It is desirable to keep hydrogen and nitrogen separated to avoid problems caused by mixing hydrogen and nitrogen in the path of the EUV radiation beam. A CAR (chemically amplified resist) resist associated with the substrate W may have an acid which is essential for the proper function of the resist. If the (basic) amine N x H y If the components (which may be ionized) react / neutralize with the acid, this will negatively affect the resist function. Since these effects will only occur on the top of the resist, we will have different photochemistry on the top of the resist and the rest of the resist, which may increase the topping effect of the resist. By using the diaphragm 32 to separate the nitrogen and hydrogen, no acid neutralizing amines will be produced, and the reactive molecule NH2 that may be produced can be mitigated. + Risks related to the problem.

[0074] The use of the diaphragm 32 therefore allows nitrogen to be used as a cooling gas for cooling the substrate W. Nitrogen is 5 times more stable than hydrogen with respect to the thermal adaptation coefficient (TAC) with respect to different surface materials. The TAC determines the extent to which the heat load is transferred from the gas to the material (TAC can be considered as part of the excess energy transferred from the gas to the material). The substrate W can be cooled more accurately by using the more stable TAC provided by nitrogen. This can directly affect the calibration process and can reduce overlap losses. Alternatively, any other suitable gas (e.g., another inert gas such as hydrogen or helium) can be used. For example, hydrogen can be used to clean the bottom of the diaphragm 32 by cleaning the radicals and ions formed by the passage of EUV radiation.

[0075] The gas is delivered at a sufficiently high pressure to transfer a significant amount of heat from the substrate W to the cooling element body 26, 27. The pressure of the gas may be kept low enough so that the gas does not cause damage to the substrate W. Furthermore, the pressure of the gas may be kept low enough so that it does not generate a tangential force large enough to cause the substrate W to slide over a burl on the substrate table WT (e.g., no tangential force greater than 10 mN is generated). The pressure of the gas may be kept low enough so that no significant deformation of the substrate W occurs at the location where the substrate is supported by the burl of the substrate table WT. The substrate may have, for example, an outer edge of 1 mm-3 mm that is not supported by the burl of the substrate table WT. The pressure of the gas may be low enough so that downward deformation of the substrate at the outer edge is limited to an amount that can be compensated by the lithographic apparatus (e.g., a deformation of less than 10 nm). For example, the pressure of the gas in region 18 may be greater than 100 Pascals. For example, the pressure of the gas in region 18 may be greater than 200 Pascals. For example, the pressure of the gas in region 18 can be up to about 1000 Pascals, can be up to about 2000 Pascals, and can be up to about 5000 Pascals. For example, the pressure of the gas in region 18 can be 100 kPa or higher. For example, the pressure of the gas in region 18 can be about 500 kPa or higher.

[0076] The pressure of the gas in region 18 will be affected by the gap between the lowermost surface of the cooling element body 26, 27 and the substrate W (an increase in the gap will make it more difficult to maintain a high pressure). For example, the gap may be about 20 microns or more, and may be about 50 microns or more. The gap may be about 200 microns or less.

[0077] In addition to promoting the transfer (transfer) of heat from the substrate W to the cooling element body 26, 27, the gas can also act as a cushion, which prevents or inhibits contact between the cooling element body 26, 27 and the substrate W. In an embodiment, the spacing between the lowermost surface of the cooling element body 26, 27 and the substrate W can be greater than 20 microns, and can be, for example, 50 microns or greater. If the spacing is too small, there is a significant risk of contact between the cooling element body 26, 27 and the substrate W. This is undesirable because it may cause damage to the lithographic apparatus. A spacing of 20 microns is sufficient to reduce the risk of contact to a reasonable level. A spacing of 50 microns is sufficient to substantially eliminate the risk of contact. For example, the spacing can reach 100 microns, and for example, can reach 200 microns. A spacing greater than 200 microns may be undesirable because it may cause too much gas to leak out from below the cooling element body 26, 27.

[0078] Further details of aspects of cooling devices and cooling elements that can be used are described, for example, in the published application WO 2018 / 041599 A1, which is incorporated herein by reference.

[0079] In some embodiments, an additional gas flow system (not shown) may be provided that provides an additional gas flow above the diaphragm 32. The additional gas flow system includes a gas delivery conduit (not shown) in the cooling device 20. The gas delivery conduit may be disposed in the cooling elements 22, 24. In some examples, an additional gas flow may be provided through the funnel 36, but in this case a large flow rate may be required, which may be disadvantageous. In some examples, the additional gas flow system may be part of the gas flow system previously described, or may be a separate gas flow system. In some examples, the gas delivery conduit of the additional gas flow system may be at least partially shared with the gas delivery conduit of the gas flow system.

[0080] The additional gas flow over the diaphragm 32 may provide a pressure balance with the gas flow under the diaphragm 32. The additional gas flow over the diaphragm 32 may at least partially protect the projection system PS from contaminants etc. in the event that the diaphragm 32 is damaged or ruptured. The additional gas flow over the diaphragm 32 may prevent falling particles etc. from hitting the diaphragm 32 (which may rupture if the particles are large enough). The falling particles may be loose particles generated or received upstream (optical path) of the projection system PS. The additional gas flow over the diaphragm 32 may cool the diaphragm 32 which is heated due to the absorption of EUV and IR radiation.

[0081] The additional gas may be hydrogen. Alternatively, any other suitable gas may be used (eg another inert gas such as helium).

[0082] Figure 5 An embodiment of an alternative diaphragm system comprising two diaphragms is shown. The diaphragm system comprises a first diaphragm which is substantially identical to diaphragm 32 and will be referred to as diaphragm 32 and a second diaphragm which will be referred to as further diaphragm 38 . Figure 5 The layout and Figure 2 The same or similar and the same numerals will be used for the same or similar parts. Figure 5 The blocking member 34 provides Figure 2 For the sake of clarity, some reference numerals have been omitted, but it should be understood that Figure 5 The cooling device 20 may have Figure 2 The same or similar components of the cooling device.

[0083] A further diaphragm 38 is located above the diaphragm 32, which is located in the same Figure 2 Both the membrane 32 and the further membrane 38 physically close the slit 30 so that contaminants and / or gases etc. cannot pass from the area 18 to the projection system PS.

[0084] It should be understood that in other examples, the diaphragm 32 and the additional diaphragm 38 may not be Figure 5 The precise position shown, but can be located at a different vertical position between the fingers 28, 29, while still physically closing the slit 30. In other examples, there may be no fingers and the diaphragm 32 and the additional diaphragm 38 can be located between portions of the cooling bodies 26, 27.

[0085] Cooling device 20, membrane 32, and further membrane 38 define a volume 40. A further gas flow system (not shown) is configured to provide a further gas flow through volume 40, as indicated by arrows in volume 40. For example, volume 40 is isolated and further gas cannot escape into region 18. The further gas flow system may be part of or separate from the gas flow system and / or the additional gas flow system.

[0086] Additional gas flows above membrane 32 and below membrane 38 (ie, between the two membranes).

[0087] The additional gas is relatively cool to help reduce the temperature of the membranes 32, 38. The additional gas may be at a temperature that cools the membranes 32, 38. The additional gas may be hydrogen. Hydrogen may be preferred because it may provide better EUV radiation transmission than other gases. Alternatively, any other suitable gas may be used (e.g., another inert gas such as helium).

[0088] Figure 6 is along Figure 5 A cross-sectional view taken along line AA' is shown. Figure 6 A cooling device 20 is shown comprising: an additional gas delivery conduit, an inlet gas delivery conduit 42 supplying additional gas to the volume 40, and an outlet gas delivery conduit 44 returning additional gas from the volume 40. The arrows in the additional gas delivery conduits 42, 44 show the flow direction of the additional gas. There are two manifolds 46 to help distribute the additional gas substantially evenly into the volume 40 above the membranes 32, 38 and out of the volume 40, respectively. Each cooling element 22, 24 may include an additional gas delivery conduit.

[0089] The additional gas flow between the membranes 32, 28 provides improved cooling of the membranes 32, 38. Furthermore, having a second membrane (additional membrane 38) also physically close the slit 30 means that even if the first membrane (membrane 32) is damaged and allows some contaminants to pass through the slit 30, the second membrane 38 will protect the projection system PS by blocking these contaminants. In other examples, the membrane system may include more than two membranes.

[0090] Although specific reference may be made herein to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein may have other applications. Other possible applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, etc.

[0091] Although embodiments of the invention may be specifically referenced herein in the context of a lithographic apparatus, embodiments of the invention may be used in other apparatuses. Embodiments of the invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object, such as a wafer (or other substrate) or a mask (or other pattern forming apparatus). These apparatuses may generally be referred to as lithographic tools. Such lithographic tools may use vacuum conditions or ambient (non-vacuum) conditions.

[0092] Although specific reference may have been made above to the use of embodiments of the invention in the context of optical lithography, it will be appreciated that the invention is not limited to optical lithography and may be used in other applications (eg imprint lithography) where the context permits.

[0093] Where the context permits, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include a read-only memory (ROM); a random access memory (RAM); a magnetic storage medium; an optical storage medium; a flash memory device; an electrical, optical, acoustic, or other form of propagation signal (e.g., a carrier wave, an infrared signal, a digital signal, etc.), etc. In addition, firmware, software, routines, instructions may be described herein as performing certain actions. However, it should be appreciated that such description is merely for convenience, and that such actions are actually caused by a computing device, processor, controller, or other device that executes firmware, software, routines, instructions, etc., and that doing so may cause an actuator or other device to interact with the physical world.

[0094] Although specific embodiments of the present invention have been described above, it should be understood that the present invention may be practiced in a manner other than that described. The above description is intended to be illustrative rather than restrictive. Therefore, it will be apparent to those skilled in the art that modifications may be made to the described invention without departing from the scope of the claims set forth below.

Claims

1. A lithography apparatus, comprising: a projection system configured to project a patterned radiation beam via a projection path onto an exposure zone at a substrate held on a substrate stage, the substrate stage being movable in a region below the projection system; as well as a cooling device configured to cool the substrate via heat transfer from the substrate to a cooling element located above the substrate and adjacent to the projected path; wherein the cooling device comprises a membrane system located in the projection path to physically separate the projection system from the region, The cooling element comprises fingers extending away from a horizontally disposed body of the cooling element towards the substrate, wherein the membrane system is located between the fingers. 2 . The lithographic apparatus of claim 1 , comprising a gas flow system configured to provide a flow of gas beneath the membrane system.

3. The lithographic apparatus of claim 2, wherein the gas flow system is configured to provide the flow of the gas between the cooling element and the substrate, the flow being configured to increase heat transfer from the substrate to the cooling element. 4 . The lithographic apparatus of claim 3 , wherein the gas flow system is configured to provide the flow of the gas onto the exposure region on the substrate.

5. The lithographic apparatus of claim 2, wherein the gas flow system comprises a gas delivery conduit in the cooling device. The lithographic apparatus according to claim 2 , wherein the gas comprises nitrogen.

7. The lithographic apparatus according to any one of the preceding claims, further comprising an additional gas flow system configured to provide a flow of an additional gas over the membrane system.

8. The lithographic apparatus according to any one of claims 1 to 7, wherein the membrane system comprises a single membrane.

9. The lithographic apparatus according to any one of claims 1 to 7, wherein the membrane system comprises a first membrane and a second membrane.

10. The lithographic apparatus of claim 9, further comprising a further gas flow system configured to provide a flow of a further gas through a volume defined by the cooling device, the first membrane, and the second membrane.

11. The lithographic apparatus according to any one of claims 1 to 7, further comprising a blocking member located at a periphery of the cooling device and extending outwardly and / or upwardly from the cooling device.

12. The lithographic apparatus according to claim 11, wherein the blocking member is connected to the cooling device.

13. The lithographic apparatus according to any one of claims 1 to 7, wherein the cooling arrangement comprises a slit, the slit being configured such that the projection path passes through the slit, wherein the diaphragm system physically closes the slit.

14. The lithographic apparatus of claim 2, wherein the gas flow system is configured to provide a flow of the gas out of the fingers.

15. A cooling device for a lithographic apparatus, the lithographic apparatus comprising a projection system, the projection system being configured to project a patterned radiation beam via a projection path onto an exposure zone at a substrate held on a substrate table, the substrate table being movable in a region below the projection system; the cooling device being configured to cool the substrate via heat transfer from the substrate to a cooling element located above the substrate and adjacent the projected path; in, The cooling device comprises a membrane system located in the projection path to physically separate the projection system from the area, The cooling element comprises fingers extending away from a horizontally disposed body of the cooling element towards the substrate, wherein the membrane system is located between the fingers.

16. A photolithography method comprising: projecting a patterned radiation beam via a projection path through a projection system to form an exposure area on a substrate held on a substrate table that is movable in a region below the projection system, and using a cooling device to cool the substrate via a cooling element for removing heat from the substrate, the cooling element being located above the substrate and adjacent to the projection path, wherein the cooling means comprises a membrane system located in the projection path so as to physically separate the projection system from the region, The cooling element comprises fingers extending away from a horizontally disposed body of the cooling element towards the substrate, wherein the membrane system is located between the fingers.

17. The photolithographic method of claim 16, further comprising providing a flow of gas from a gas flow system beneath the membrane system.

18. The lithographic method of claim 17, further comprising providing the flow of gas between the cooling element and the substrate, the flow being configured to increase heat transfer from the substrate to the cooling element.

19. The lithographic method according to any one of claims 16 to 18, further comprising providing a flow of a further gas from a further gas system through a volume defined by the cooling device, the first membrane of the membrane system, and the second membrane of the membrane system.

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