Assembly for a lithographic apparatus

Abstract

An assembly for a lithographic apparatus is described that is configured to heat a pellicle membrane by one or a combination of i) providing a heated gas, ii) radiative heating, iii) resistive heating, and iv) inductive heating, and / or by irradiating the pellicle membrane with light having a wavelength of about 91 nm to about 590 nm. Also described is a method of extending an operational lifetime of a pellicle membrane, comprising heating at least a portion of the pellicle membrane when irradiated by EUV by i) providing a heated gas, ii) radiative heating, iii) resistive heating, and iv) inductive heating, and / or by irradiating the pellicle membrane with light having a wavelength of about 91 nm to about 590 nm.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to European Application No. 22154980.1, filed February 3, 2022, and European Application No. 22158451.9, filed February 24, 2022, both of which are incorporated by reference in their entireties into this specification. [Background technology]

[0002] The present invention relates to an assembly for a lithographic apparatus, a method for increasing the operational lifetime of a pellicle membrane, a lithographic apparatus, a ReMa blade and the use of said assembly, method, ReMa blade or lithographic apparatus in a lithographic method or apparatus.

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). A lithographic apparatus may, for example, project a pattern from a patterning device (e.g. mask) onto a layer of radiation-sensitive material (resist) provided on the substrate.

[0004]

[0004] The wavelength of radiation used by a lithographic apparatus to project a pattern onto a substrate determines the minimum size of features that can be formed on the substrate. To form smaller features on a substrate than conventional lithographic apparatus (which may use electromagnetic radiation having a wavelength of, for example, 193 nm), lithographic apparatus may be used that use EUV radiation, which is electromagnetic radiation having a wavelength in the range of 4-20 nm.

[0005]

[0005] A lithographic apparatus includes a patterning device (e.g. a mask or a reticle). Radiation is provided through or reflected from the patterning device to form an image on a substrate. To protect the patterning device from airborne particles and other forms of contamination, a membrane assembly, also referred to as a pellicle, may be provided. Contamination on the surface of the patterning device may cause manufacturing defects of the substrate.

[0006]

[0006] Pellicles may also be provided to protect optical components other than the patterning device. Pellicles may also be used to provide a passage for lithographic radiation between mutually sealed regions of the lithographic apparatus. Pellicles may also be used as filters, such as spectral purity filters, or as part of a dynamic gas lock of the lithographic apparatus.

[0007]

[0007] The presence of a pellicle in the path of the EUV radiation beam requires that the pellicle have a high EUV transmittance. A high EUV transmittance can increase the proportion of incident radiation that passes through the pellicle, and can reduce the operating temperature of the pellicle by reducing the amount of EUV radiation absorbed by the pellicle. Since the transmittance depends at least in part on the thickness of the pellicle, it is desirable to provide a pellicle that is as thin as possible while still remaining reliably strong enough to withstand the sometimes hostile environment within a lithography apparatus. Carbon-based pellicle membranes have been proposed, as carbon has a high melting point and therefore the potential to withstand higher source powers than currently possible.

[0008]

[0008] In view of the important role of pellicle membranes within lithographic apparatus, it is desirable to improve the life of the pellicle membrane by preventing, reducing or eliminating damage to the pellicle membrane.

[0009]

[0009] The present invention has been developed with the aim of addressing at least some of the problems identified above. Summary of the Invention

[0010]

[0010] According to a first aspect of the present invention, there is provided an assembly for a lithographic apparatus configured to desorb adsorbed hydrogen from a pellicle membrane by heating the pellicle membrane by one or a combination of i) providing a heated gas, ii) radiative heating, iii) resistive heating, and iv) inductive heating, and / or by irradiating the pellicle membrane with light having a wavelength of approximately 91 nm to approximately 590 nm.

[0011]

[0011] In use, the pellicle membrane is in the direct optical path of radiation, such as EUV radiation, used in a lithography tool. Carbon nanotubes have been proposed as a suitable material for forming the pellicle membrane, given the high melting point of carbon, which allows for higher source powers to be provided without melting the pellicle membrane. The present invention has particular, but not exclusive, application to protecting carbon-based pellicle membranes, such as carbon nanotube-based pellicle membranes, from etching by hydrogen ionized by EUV present in a lithography tool.

[0012]

[0012] The mechanism of carbon etching in EUV lithography tools has been found to be a two-component process. In particular, hydrogen ions (e.g., H + , H2 + , H3 +) and hydrogen radicals H* are both required to etch the carbon. Without wishing to be bound by chemical theory, it is believed that the carbon-carbon bonds in the nanotubes can be broken by energetic hydrogen ions. The broken bonds can be passivated by dissolved or adsorbed hydrogen radicals. If passivation does not occur, it is possible to restore the bonds. It is believed that heating the carbon nanotube-based pellicle membrane reduces the amount of adsorbed hydrogen, thereby reducing the rate at which passivation occurs. This in turn reduces the rate at which carbon is etched from the pellicle via being released as a hydrocarbon. Heating the pellicle membrane has been found to inhibit the etching of carbon from the pellicle membrane in the hydrogen plasma environment of the lithography apparatus, in addition to any heating effects provided by exposure to the radiation beam used in the associated lithography process. The present disclosure provides several different methods that can be used individually or in combination to provide thermal energy to the pellicle membrane to reduce the amount of adsorbed hydrogen, thereby reducing the rate of etching. Similarly, photons with a sufficiently high energy, such as photons of UV light, can break the bonds between the adsorbed hydrogen and the carbon of the pellicle membrane. Therefore, the adsorbed hydrogen can be removed without necessarily heating the pellicle membrane. This has the advantage of avoiding the introduction of additional heat sources into the lithography apparatus, especially in the vicinity of the reticle. By avoiding or reducing the heat introduced into the apparatus, the negative effects of heating on imaging and overlay performance can be reduced or eliminated. The binding energy of the adsorbed hydrogen radicals varies depending on the proximity of other hydrogen radicals. Typically, the binding energy is in the range of about 0.7 eV to about 2.1 eV. Therefore, photons with wavelengths shorter than approximately 590 nm have sufficient energy to desorb the adsorbed hydrogen. Furthermore, it is desirable that the light does not ionize hydrogen gas, and therefore is preferably below the ionization energy of hydrogen gas. Therefore, the wavelength of the light is preferably greater than approximately 91 nm (13.6 eV).Even at the shortest wavelengths described herein (91 nm), the pellicle membrane is not directly damaged, as no direct damage has been observed from the much more energetic EUV photons, which have wavelengths of approximately 13.5 nm.

[0013]

[0013] The carbon nanotubes may be single-walled or multi-walled. The pellicle membrane may comprise single-walled nanotubes, multi-walled nanotubes, or a combination thereof. Preferably, the pellicle membrane comprises single-walled nanotubes.

[0014]

[0014] The diameter of the nanotubes may range from about 1 nm to about 100 nm. Preferably, the diameter of the nanotubes ranges from about 5 nm to about 25 nm. The diameter of the nanotubes is preferably measured by transmission electron microscopy. It will be appreciated that other measurement techniques may also be used.

[0015]

[0015] The assembly may include at least one gas injection unit positioned to provide heated gas to an area of ​​the pellicle membrane surrounding an area of ​​the pellicle membrane through which the radiation beam passes in use.

[0016]

[0016] Due to diffusion, the plasma surrounding the radiation beam is incident on the pellicle membrane in an area larger than the area through which the radiation beam itself passes. While the area through which the radiation beam passes in use may achieve a temperature high enough to reduce or prevent the rate of hydrogen adsorption and therefore etching, the area surrounding that area may not achieve a high enough temperature. This is because the in-plane thermal conductivity of the pellicle membrane is very low. The present disclosure therefore provides a means for providing additional thermal energy to an area of ​​the pellicle membrane that is larger than the area of ​​the pellicle membrane that the radiation beam adds in use. By providing additional thermal energy to an area surrounding an area irradiated by the EUV radiation beam in use, etching of the pellicle membrane in the area surrounding the area irradiated by the radiation beam in use can be prevented or reduced. This can be achieved in an embodiment by directing a heated gas onto the pellicle membrane.

[0017]

[0017] At least one gas injection unit may be located on a reticle masking (ReMa) blade. ReMa blades are well known in the art and serve to control the radiation beam reaching the reticle through the pellicle. The ReMa blade exposes selected portions of the entire patterned area and also selectively blocks reticle alignment targets so that they are not printed on the wafer. The ReMa blade is movable, and therefore by providing at least one gas injection unit on the ReMa blade, the gas injection unit can be moved relative to the pellicle membrane and therefore used to heat different portions of the pellicle membrane. Thus, unlike a fixed injection port, the area around the radiation beam can be easily heated. The at least one gas injection unit may be located 10 mm or less, preferably 1 mm or less, from the leading edge of the ReMa blade. In this way, a hot gas jet is provided in close proximity to the EUV beam incident on and reflected from the reticle.

[0018]

[0018] The at least one gas injection unit may be thermally insulated from the ReMa blade. Since it is unnecessary and undesirable to actively heat the ReMa blade, it is desirable to mitigate the heating effect of the at least one gas injection unit on the associated ReMa blade. In use, the ReMa blade is actively cooled to offset the heat load corresponding to the absorption of the EUV beam periodically or continuously incident on the ReMa blade. By adding thermal insulation between the ReMa blade and the hot gas injection unit, the ReMa cooling hardware can be kept to a minimum.

[0019]

[0019] At least one gas injection unit may comprise a sintered metal.

[0020]

[0020] The at least one gas injection unit may include a diffuser, which provides a more uniform distribution of the heated gas over the pellicle membrane and also reduces the possibility of high velocity jets that may damage the delicate pellicle membrane.

[0021]

[0021] The at least one gas injection unit may include a heater configured to heat the gas from ambient temperature to a desired temperature, or to maintain or increase the temperature of a gas already heated above ambient temperature.

[0022]

[0022] The at least one gas injection unit may include a showerhead. The showerhead may include a plurality of defined channels through which jets of gas may be provided. As such, a showerhead may differ from a diffuser in that the gas provided therefrom is in the form of a plurality of discrete streams, whereas a diffuser provides a generally uniform flow with less clearly defined discrete streams.

[0023]

[0023] The heating gas may comprise hydrogen. The heating gas may comprise 95% by volume or more, 96% by volume or more, 97% by volume or more, 98% by volume or more, or 99% by volume or more of hydrogen.

[0024] The heated gas may be provided at a temperature of about 500° C. to about 1200° C., optionally about 600° C. to about 1000° C. As such, an apparatus according to the present disclosure may be configured to provide the heated gas at a temperature sufficient to desorb hydrogen gas from the surface of the pellicle membrane.

[0025] The heated gas may be provided at a pressure of about 10 Pa or more and / or at a velocity of more than 1 m / s, preferably about 10 m / s or more, preferably about 20 m / s or more. Since in most lithographic apparatus there is a flow of hydrogen gas across the surface of the pellicle membrane, it is preferred that the velocity of the heated gas is faster than the flow of hydrogen across the surface of the pellicle membrane so that the heated gas can transfer its thermal energy to the pellicle without being deflected too quickly.

[0026] The assembly may include at least one radiant heater provided on the at least one reticle masking (ReMa) blade. The at least one radiant heater may be thermally insulated from the at least one ReMa blade. The at least one heater may be configured to provide a heat load to the pellicle in a region overlapping a pellicle area irradiated by the EUV beam. The at least one heater may provide a heat load of 1 W / cm. 2 Ultra (e.g. 2~4W / cm 2 ) in an area within 1-3 cm around the area irradiated by the EUV, and / or at least one heater may be configured to provide a heat load of 1 W / cm2 to an area of ​​the pellicle that is more than 1-3 cm away from the EUV irradiated area. 2The pellicle may be configured to provide a heat load of less than 1000 MPa. The heat load is adjusted to reach a desired temperature that takes into account the convection and radiation properties of the pellicle. Thus, by providing a higher heat load to an area surrounding the area of ​​the pellicle membrane that is irradiated by the EUV radiation beam in use, that area is heated to a temperature that prevents or reduces etching by the hydrogen plasma. Additionally, by providing a lower heat load to areas outside of the area most affected by etching, the overall heat load on the pellicle membrane is managed and existing cooling mechanisms can still be used, thereby avoiding the need to modify other components of the lithographic apparatus.

[0027]

[0027] The radiant heater may be selected such that the emission spectrum of the radiant heater overlaps with the maximum absorption spectrum of the pellicle membrane, thus providing optimal transfer of thermal energy from the radiant heater to the pellicle membrane.

[0028]

[0028] The at least one radiant heater may be configured to manage the amount of IR radiation reflected by the reticle towards the wafer in use. The at least one radiant heater may include one or more guides configured to direct the emitted thermal radiation towards the pellicle membrane. The one or more guides may be in the form of metal fins, optionally having a high reflectivity (i.e., reflectivity greater than or equal to 0.5) for heater radiation at grazing incidence, for example at an incidence angle of less than 45 degrees. It is desirable for the radiant heater to be directional to avoid unnecessarily providing thermal energy to components that do not need to be heated. By providing a guide in the form of a fin, reflection of IR radiation from the reticle in the direction of the EUV beam sent to the wafer is also reduced. The fins may include a metal having a preferred grazing incidence reflectivity greater than 0.5, greater than 0.75, or greater than 0.9 for radiation between 1 and 5 microns. The directionality of the radiative heater may also be configured to provide maximum heat load from the heater to a region adjacent the pellicle area that is irradiated by EUV.

[0029]

[0029] The assembly may include electrical contacts and a power supply configured to pass a current through the pellicle membrane at the plane of the pellicle membrane. Carbon-based pellicles, particularly carbon nanotube-based pellicles, are electrically conductive, and in use, a voltage across the pellicle in the range of 1V to 100V allows for sufficient heating and is compatible with the reticle mini environment. To heat the pellicle, a DC, AC or pulsed voltage synchronized to the EUV pulse can be used. To reduce the flux or energy of positive ions from the EUV plasma and thus further reduce carbon etching, the assembly may be configured to provide a positive bias to the pellicle in the range of +1V to +100V.

[0030]

[0030] It is possible to cause heating of the membrane by passing an electric current through it in the plane of the membrane. The degree of heating can be controlled by controlling the amount of power provided. A higher current results in greater heating.

[0031]

[0031] The electrical contacts may be configured to divide the pellicle membrane into one or more sectors, at least one of the sectors corresponding to an area surrounding an area of ​​the pellicle membrane that is exposed to the radiation beam in use, and the assembly is further configured to pass a current to at least one sector corresponding to an area surrounding an area of ​​the pellicle membrane that is exposed to the radiation beam in use. The assembly may be configured to provide an AC, DC or voltage pulse synchronized to the EUV pulse. To limit or prevent sputtering in the reticle mini environment, the amplitude of the voltage may be limited to approximately 100V.

[0032] To at least partially repel the etching ions, the assembly can be configured to provide an overall bias on the pellicle membrane in the range of about 1 V to about 100 V. Since etching is considered to be a two-component process, by providing an electrical bias, at least some of the charged ions can be repelled from the pellicle membrane, thereby preventing or reducing etching of the pellicle membrane.

[0033]

[0033] Since only those areas of the pellicle membrane that have been exposed to the diffused hydrogen plasma but not heated by the radiation beam need to be heated, the assembly can be configured to selectively apply electrical current to such areas, thereby reducing the overall power required and also reducing the total thermal energy added to the entire associated lithographic apparatus.

[0034]

[0034] The assembly may include at least one coil and / or at least one antenna provided on at least one reticle masking (ReMa) blade and configured to induce an electric current in the pellicle membrane to heat the pellicle membrane.

[0035]

[0035] Inducing electric current can also be used to heat the pellicle membrane. This can be achieved by providing a coil and / or antenna that generates a time-varying electric field. The coil and / or antenna can be powered by AC current. This allows the heating to be done wirelessly and does not provide a voltage difference that can affect the plasma environment. The heat load profile on the pellicle by the induction heater is localized and may overlap and / or be adjacent to the EUV irradiated pellicle. This has the advantage of reducing the problems associated with heating of the associated reticle.

[0036] It will be appreciated that different options for heating and / or irradiating the pellicle membrane may be provided individually or in combination, such that an assembly may include one, two, three or more of such options, with all combinations being expressly contemplated and disclosed.

[0037] The assembly may be configured to heat at least a portion of the pellicle membrane to a temperature of from about 600° C. to about 1200° C. Such temperatures have been found to reduce or eliminate etching of carbon from the pellicle membrane by the hydrogen plasma.

[0038]

[0038] The assembly may be configured to provide a heat load to the pellicle membrane in an area adjacent to an area of ​​the pellicle membrane through which the EUV radiation beam passes in use, and to limit the heat load to a region of the pellicle away from the EUV irradiated pellicle area. Additionally or alternatively, the assembly may be configured to heat a portion of the pellicle membrane approximately 1-3 cm around the area irradiated by EUV radiation in use to a temperature of approximately 600°C to approximately 1200°C, and to heat a portion of the pellicle membrane more than approximately 1-3 cm around the area irradiated by EUV radiation in use to a temperature of approximately 500°C or less, preferably ambient temperature. Ambient temperature refers to the temperature that the particular area of ​​the pellicle membrane would reach if no additional heating was provided.

[0039]

[0039] The assembly can be configured to irradiate the pellicle membrane with two or more wavelengths of light within the range of about 91 nm to about 590 nm. Because the binding energy of hydrogen radicals depends on the proximity of other hydrogen radicals, irradiating the pellicle membrane with light of different wavelengths serves to further reduce the thermal load applied to the membrane while still extending the life of the pellicle membrane by removing adsorbed hydrogen.

[0040]

[0040] The assembly may include two or more light sources configured to provide light at wavelengths from approximately 91 nm to approximately 590 nm. Optionally, the light source is selected from a lamp, a laser, or a plasma source. The light source may be selected depending on the desired wavelength of light required and whether the light needs to be provided to a concentrated area, as in the case where a laser source is preferred, or whether the light needs to be provided over a wider area, as in the case where a lamp or plasma source is desirable.

[0041]

[0041] The assembly may be configured to irradiate the pellicle membrane in an area adjacent to an area of ​​the pellicle membrane through which the EUV radiation beam passes in use. The area through which the EUV radiation beam passes in use may be heated to a temperature high enough to desorb adsorbed hydrogen, so that it may not be necessary to desorb hydrogen therefrom. Of course, it will be appreciated that the assembly may be configured and used to remove adsorbed hydrogen from anywhere on the surface of the pellicle membrane, as required.

[0042]

[0042] The assembly can be configured to scan light at wavelengths from about 91 nm to about 590 nm across the pellicle membrane. By scanning the light across the pellicle membrane, adsorbed hydrogen can be removed from anywhere on the surface without necessarily illuminating the entire surface at once.

[0043]

[0043] The assembly may include a light source according to the sixth aspect of the present disclosure.

[0044] According to a second aspect of the present invention, there is provided a method of extending the operational life of a pellicle membrane, comprising: i) providing a heated gas for heating at least a portion of the pellicle membrane; ii) heating at least a portion of the pellicle membrane by one or a combination of radiative heating, iii) resistive heating, and iv) inductive heating; and / or desorbing adsorbed hydrogen from the pellicle by irradiating the pellicle with light having a wavelength of about 91 nm to about 590 nm. Preferably, such portion of the pellicle is adjacent to the pellicle area irradiated by EUV.

[0045]

[0045] As with the first aspect of the present disclosure, heating the pellicle membrane or irradiating it with light within a particular wavelength range results in desorption of atomic and molecular hydrogen gas therefrom, which in turn reduces the rate at which carbon is etched from the pellicle membrane.

[0046]

[0046] The method may include providing heated gas via at least one gas injection unit positioned on a reticle masking (ReMa) blade.

[0047]

[0047] The method may include heating the gas using at least one gas injection unit.

[0048]

[0048] The method may include providing a heated gas at a temperature of about 500°C to about 1200°C, optionally about 600°C to about 800°C, and / or providing the heated gas at a pressure of approximately 10 Pa or more, and / or at a velocity of greater than 1 m / s, preferably approximately 10 m / s or more, preferably approximately 20 m / s or more.

[0049] The method may include heating the pellicle membrane to a temperature of from about 600° C. to about 1200° C. Preferably, the heating is directed primarily to a portion of the pellicle membrane of about 1-3 cm around the area that will be irradiated by EUV radiation in use.

[0050] It will be appreciated that the method according to the second aspect of the present disclosure can include any of the heater operations as described herein. For example, the method can include providing an electric current in a plane of the pellicle membrane to effect resistive heating thereof. Alternatively or additionally, the method can include one or more heaters as described herein.

[0051]

[0051] The method may include illuminating the pellicle membrane with two or more different wavelengths of light within the range of approximately 91 nm to approximately 590 nm.

[0052] The method may include operating a lamp, laser or plasma source to provide light at a wavelength from approximately 91 nm to approximately 590 nm.

[0053]

[0053] The method may include irradiating the pellicle membrane in an area adjacent to an area of ​​the pellicle membrane through which the EUV radiation beam passes in use.

[0054]

[0054] The method involves scanning light at wavelengths from approximately 91 nm to approximately 590 nm across a pellicle membrane.

[0055]

[0055] The method includes generating UV light according to the method of the seventh aspect of the present disclosure.

[0056] According to a third aspect of the present disclosure, there is provided a lithographic apparatus including an assembly according to the first aspect of the invention or a light source according to the sixth aspect of the present disclosure.

[0057] According to a fourth aspect of the present disclosure, there is provided a Reticle Masking (ReMa) blade for a lithographic apparatus, the Reticle Masking (ReMa) blade comprising at least one heater and / or light source arranged on a side of the blade facing a reticle in use and configured to generate light at a wavelength of about 91 nm to about 590 nm, optionally the light source being a light source according to the sixth aspect of the present disclosure. The heater may be any heater or heating means as described herein. Thus, this includes radiative, inductive, resistive or other heating means as described herein. Similarly, the light source may be any light source as described herein.

[0058]

[0058] According to a fifth aspect of the present disclosure, there is provided the use of an assembly according to the first aspect of the present disclosure, a light source according to the sixth aspect of the present disclosure, a method according to the second aspect of the present disclosure, a method according to the seventh aspect of the present disclosure, or a lithographic apparatus according to the third aspect of the present disclosure, or a ReMa blade according to the fourth aspect of the present disclosure in a lithographic process or apparatus.

[0059]

[0059] According to a sixth aspect of the present disclosure, there is provided a light source comprising a UV lamp and a grazing incidence optical element, the light path along which light is transmitted from the UV lamp to a target area during nominal use, the grazing incidence optical element being disposed between the UV lamp and the target area so as to block a direct path of particles from the UV lamp to the target area.

[0060]

[0060] Because UV light is absorbed by various materials, including glass, if UV light is to be used in a lithography apparatus, or indeed any other apparatus that requires the use of UV light and is also sensitive to particle contamination, the UV light must be generated within the device. UV lamps use electrical discharges to generate UV light, which generates a large amount of particulates. The electrical discharges can generate particulates that can then contaminate the rest of the apparatus. The present disclosure addresses this issue by using at least one grazing incidence optical element to transmit the UV light to the desired location while blocking the direct path of the particulates from the UV lamp. In this way, UV light can be generated in situ, preventing the generated particulates from reaching the same location where the UV light is needed.

[0061]

[0061] The light source may include multiple grazing incidence optical elements configured to provide a focal point between the UV lamp and the target area.

[0062]

[0062] Further contaminant reduction can be achieved by using multiple optical elements, since the use of multiple optical elements further suppresses particulates that may bounce off the first optical element. In other words, the additional optical elements can create an arbitrary path between where the contaminants are generated and where they cause a roundabout problem, so that the particles have a lower probability of reaching the end of the optical path. The multiple optical elements can be in a Wolter-like configuration, or a double ellipse with an additional focus.

[0063]

[0063] An aperture may be provided between the grazing optics, the presence of which may further reduce the possibility of contaminants passing through to the light source and may also allow a pressure differential to be established across the aperture.

[0064]

[0064] The light source may be configured to provide a different pressure on the side of the aperture where the UV lamp is located than on the side of the aperture where the target area is located.

[0065]

[0065] The pressure on the UV side can be higher than on the other side of the aperture, which is favorable for the production of UV light. Alternatively, a lower pressure on the UV side provides additional particle suppression via gas flow, which slows or stops particles generated by the UV lamp. In an embodiment, different pumping regimes can be used so that the direction of the pressure difference can be reversed.

[0066]

[0066] The light source may be configured such that the light path is arranged substantially vertically, such that particles emitted by the UV lamp are constrained by gravity.

[0067]

[0067] Further suppression of particles can be achieved by orienting the light source such that the generated particles must move against the force of gravity.

[0068]

[0068] The grazing incidence optical element may be configured to shape the light produced by the UV lamp. Any shape may be provided, such as a line or a spot.

[0069] At least a portion of the grazing incidence optical element is provided with a protective layer that is stable in hydrogen, and optionally the protective layer comprises ruthenium.

[0070]

[0070] According to a seventh aspect of the present disclosure, there is provided a method of generating UV light, the method including generating UV light with a UV lamp, directing the UV light to a target area using at least one grazing optical element, and blocking particles generated by the UV lamp to prevent them from reaching the target area.

[0071]

[0071] By blocking particles, UV light can be utilized in devices sensitive to particulate contamination.

[0072]

[0072] The method may further include focusing the UV light at a focal point, and optionally providing an aperture about the focal point. By providing a focal point and an optical aperture, the likelihood of particulate contamination passing through the apparatus may be further reduced.

[0073]

[0073] The method may include providing a pressure differential between the UV lamp and the target area. The pressure may be higher on the UV lamp side or higher on the target area side.

[0074]

[0074] The method may include shaping the UV light into a desired shape or pattern.

[0075]

[0075] It will be understood that any feature described with respect to one embodiment may be combined with any feature described with respect to another embodiment, and all such combinations are expressly contemplated and disclosed in this specification. [Brief description of the drawings]

[0076]

[0076] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which: [Figure 1]

[0077] 1 depicts a lithographic apparatus according to an embodiment of the present disclosure; [Diagram 2]

[0078] 1 is a schematic diagram of a radiation beam, a pair of ReMa blades, a pellicle membrane, and a reticle. [Diagram 3]

[0079] 1A and 1B show cross-sectional and top views of an assembly according to an embodiment of the present disclosure. [Figure 4]

[0080] 1 shows a cross section through a gas injection unit according to the present disclosure. [Diagram 5]

[0081] 1 shows a cross section through a gas injection unit according to the present disclosure. [Figure 6]

[0082] 1 illustrates an assembly according to one embodiment of the present disclosure. [Figure 7]

[0083] 1 illustrates an assembly including a light source capable of providing light at wavelengths from approximately 91 nm to approximately 590 nm, according to one embodiment of the present disclosure. [Figure 8]

[0084] 1 shows a light source according to a sixth embodiment of the present disclosure. [Figure 9]

[0085] 1 shows a light source according to a sixth embodiment of the present disclosure.

[0077]

[0086] The features and advantages of the present invention will become more apparent from the following detailed description when considered in conjunction with the drawings, in which like reference numbers identify corresponding elements throughout, and in which like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0078]

[0087] FIG. 1 shows a lithographic system including a pellicle 15 (also referred to as a membrane assembly) according to the present invention. The lithographic system includes a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an extreme ultraviolet (EUV) radiation beam B. The lithographic apparatus LA includes an illumination system LA, 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. The illumination system IL is configured to condition the radiation beam B before it is incident on the patterning device MA. The projection system is configured to project the radiation beam B (now patterned by the mask MA) onto the substrate W. The substrate W may include a previously formed pattern. In this case, the lithographic apparatus aligns the patterned radiation beam B with the previously formed pattern W on the substrate W. In this embodiment, a pellicle 15 is shown in the radiation path to protect the patterning device MA. It will be appreciated that the pellicle 15 may be positioned in any required location and may be used to protect any of the mirrors within the lithographic apparatus.

[0079]

[0088] The source SO, illumination system IL and projection system PS may all be constructed and arranged such that they can be isolated from the external environment. A gas (e.g. hydrogen) at a pressure below atmospheric pressure may be provided in the source SO. A vacuum may be provided in the illumination system IL and / or projection system PS. A small amount of gas (e.g. hydrogen) at a pressure well below atmospheric pressure may be provided in the illumination system IL and / or projection system PS.

[0080]

[0089] The radiation source SO shown in FIG. 1 is of a type that may be referred to as a laser-produced plasma (LPP) source. A laser, which may be, for example, a CO2 laser, is arranged to deposit energy via a laser beam into a fuel, such as tin (Sn), provided from a fuel emitter. Although the following description refers to tin, any suitable fuel may be used. The fuel may be, for example, in liquid form, but may be, for example, a metal or an alloy. The fuel emitter may comprise a nozzle configured to direct the tin, for example in the form of droplets, along a trajectory towards the plasma formation region. The laser beam is incident on the tin in the plasma formation region. The accumulation of laser energy in the tin creates a plasma in the plasma formation region. Radiation, including EUV radiation, is emitted from the plasma during de-excitation and recombination of the ions of the plasma.

[0081]

[0090] The EUV radiation is collected and focused by a near-normal incidence radiation collector (sometimes, more commonly, referred to as a normal incidence radiation collector). The collector may have a multi-layer structure arranged to reflect EUV radiation (e.g., EUV radiation having a desired wavelength, such as 13.5 nm). The collector may have an elliptical configuration with two elliptical foci. The first focus may be at the plasma formation region and the second focus may be at an intermediate focus, as discussed below.

[0082]

[0091] The laser system may be separate from the radiation source SO. In this case, the laser beam may be passed from the laser system to the radiation source SO with the aid of a beam delivery system (not shown), e.g. comprising suitable directing mirrors and / or beam expanders and / or other optics. The laser system and the radiation source SO together may be considered as a radiation system.

[0083]

[0092] The radiation reflected by the collector forms a radiation beam B. The radiation beam B is focused at a point to form an image of the plasma formation region which acts as a virtual radiation source for the illumination system IL. The point at which the radiation beam B is focused may be referred to as the intermediate focus. The radiation source SO is arranged such that the intermediate focus is located at or near an aperture in the source enclosure structure.

[0084]

[0093] The radiation beam B passes from a radiation source SO through an illumination system IL, which is configured to condition the radiation beam. The illumination system IL may include a facetted field mirror device 10 and a facetted pupil mirror device 11. Together the facetted field mirror device 10 and the facetted pupil mirror device 11 give the radiation beam B a desired cross-sectional shape and a desired angular distribution. The radiation beam B passes from the illumination system IL and is incident on a patterning device MA, which is held by a support structure MT. The patterning device MA reflects the radiation beam B and imparts a pattern to the radiation beam B. The illumination system IL may include other mirrors or devices in addition to or instead of the facetted field mirror device 10 and the facetted pupil mirror device 11.

[0085]

[0094] After reflection from the patterning device MA, the patterned radiation beam B is incident on a projection system PS. The projection system may comprise a number of mirrors 13, 14 arranged to project the radiation beam B onto a substrate W held by a substrate table WT. The projection system PS may apply a demagnification factor to the radiation beam to form images of features that are smaller than corresponding features on the patterning device MA. For example a demagnification factor of 4 may be applied. Although the projection system PS has two mirrors 13, 14 in Figure 1, the projection system may include any number of mirrors (for example six mirrors).

[0086]

[0095] The radiation source SO shown in Figure 1 may include components not shown. For example, a spectral filter may be provided within the radiation source. The spectral filter may be substantially transparent to EUV radiation but may substantially block radiation of other wavelengths, such as infrared radiation.

[0087]

[0096] In one embodiment, the membrane assembly 15 is a pellicle for a patterning device MA for EUV lithography. The membrane assembly 15 of the present invention may be used for a dynamic gas lock, for a pellicle, or for another application. In one embodiment, the membrane assembly 15 comprises a membrane formed from at least one membrane layer configured to transmit at least 90% of the EUV radiation incident thereon. To ensure maximum EUV transmission and minimal impact on imaging performance, the membrane is preferably supported only at the boundaries.

[0088]

[0097] If the patterning device MA is left unprotected, it may become contaminated and require the patterning device MA to be cleaned or discarded. Cleaning the patterning device MA takes up valuable production time, and discarding the patterning device MA is expensive. Replacing the patterning device MA also takes up valuable production time.

[0089]

[0098] FIG. 2 shows the main scheme of ion and radical distribution around the EUV radiation cone B, as indicated by the flux onto the pellicle membrane 110 provided to protect the reticle 100. As shown, the width W-EUV of the EUV radiation beam is narrower than the width W-ion of the ion range, which in turn is narrower than the width W-rad of the radical range in the system. Therefore, only a relatively small area of ​​the pellicle membrane 110 is exposed to the EUV radiation beam B, while a larger area of ​​the pellicle membrane 110 is exposed to the ion and radical fluxes generated in the lithography apparatus. In this way, only the area irradiated by the EUV radiation beam B is heated to a temperature high enough to desorb the adsorbed atomic and molecular hydrogen, thereby undergoing a reduced rate of etching. Furthermore, there is less suppression of radicals in the narrow slit between the pellicle 110 and the ReMa blades 120, 130, since radicals have a recombination rate of less than 0.1 at the nearest wall, while ions have a recombination rate of approximately 1.

[0090]

[0099] FIG. 3 shows a cross-sectional and top view of an assembly according to an embodiment of the present disclosure. The reticle 100 is provided with a pellicle membrane 110. The ReMa blades 120, 130 are provided with heaters 210, 220. The heaters 210, 220 may be the same type of heater or may be different. In the illustrated embodiment, at least one of the heaters 210, 220 is a gas injection unit. In other embodiments, at least one of the heaters 210, 220 is a radiative heater. In other embodiments, at least one of the heaters 210, 220 is an inductive heater. The heaters 210, 220 are provided on a side of the ReMa blade that faces the reticle in use. The heaters 210, 220 are positioned near the edge of the ReMa blade in an area close to where the radiation beam B passes in use, such that the heaters can heat the pellicle membrane 110 in an area surrounding where the radiation beam passes in use. The heaters can be replaced or supplemented by one or more light sources configured to provide light at wavelengths from approximately 91 nm to approximately 590 nm. This is where hydrogen ions and radicals are primarily present, and therefore where the greatest etching may occur in the absence of the improvements provided by the present disclosure. In the illustrated embodiment, gas supply lines 211, 212, 221, 222 are provided that supply gas to the heaters 210, 220. The gas may already be heated, or the heaters 210, 220 may be configured to heat the gas before it is provided to the pellicle membrane 110. If the heaters 210, 220 require electrical connections, such as in the case of radiative or inductive heaters, the electrical connections may be provided in a manner similar to the illustrated gas lines 211, 212, 221, 222.

[0091]

[0100] FIG. 4 shows one embodiment of a ReMa blade 230 according to the present disclosure. A thermal insulation layer 231 is provided on the body of the ReMa blade to provide thermal insulation and reduce the amount that the ReMa blade 150 heats up during use. Gas supply channels 232 are provided that are in fluid communication with a heating element 233 in the form of a showerhead. Thus, gas can pass from the gas supply channels 232 through the heating element 233 where the gas is heated. The gas passes through discrete paths within the heater 233. An optical diffuser 234, which may be formed from sintered metal, is provided to provide a uniform flow distribution to the pellicle membrane and to avoid high velocity jets of heated gas. Additionally, a diffuser based on a heat conducting medium (e.g., sintered metal) can improve heat exchange and direct hotter gas to the pellicle for a given temperature of the heater.

[0092]

[0101] 5 shows an embodiment similar to that of FIG. 4, but with the relative positions of the heating element 233 and the diffuser 234 swapped. It will be appreciated that the diffuser 234 may be provided on both sides of the heating element 233, or on neither side. The heating element 233 may also be in the form of a diffuser configured to heat gas passing therethrough, and a showerhead element need not necessarily be provided. Similarly, the diffuser may act as a heat exchanger.

[0093]

[0102] 6 shows an embodiment of the present disclosure including radiant heaters 240, 250. A beam of EUV radiation 270 is incident on and reflected from the reticle 100, which is protected by the pellicle membrane 110. The radiant heaters 240, 250 are integrated with the ReMa blades 120, 130 and provide heat to areas 111, 112 surrounding the area of ​​the pellicle membrane through which the beam of radiation B, 270 passes in use. Thermal insulation 241 is provided between the ReMa blades 120, 130 to reduce the thermal load on the ReMa blades 120, 130. A radiant element 242 emits IR radiation towards the pellicle membrane 110, a few millimeters away. Optional IR reflecting fins 244 direct the IR radiation to prevent or limit reflection of IR 260 by the reticle at the NA of the lithographic apparatus and reduce the thermal load on the wafer.

[0094]

[0103] FIG. 7 illustrates one embodiment of the present disclosure including a light source 310 configured to provide light having a wavelength from approximately 91 nm to approximately 590 nm and to illuminate at least a portion of the pellicle membrane 110.

[0095]

[0104] 8 illustrates one embodiment of a light source according to the present disclosure. The light source includes a UV lamp 311 configured to generate UV light. The light source also includes a number of grazing incidence optical elements 312, such as mirrors. The UV light generated by the UV lamp 311 travels along an optical path 313 and is moved to a target area by the optical elements 312. Particles generated by the UV lamp 311 travel along a path 314 where they are blocked from traveling to the target area. The particles are blocked by the optical elements 312 or by a separate blocking element positioned in the path of the particles.

[0096]

[0105] 9 shows another embodiment of a light source including two sets of optical elements. The UV light is focused at a focal point 315. An optional aperture 316 is provided around the focal point 315. The presence of the focal point and optional aperture 316 makes it less likely that particles generated by the UV lamp will reach the device by bouncing off the optical elements. Particles that are not traveling along the optical path are blocked by the aperture 316.

[0097]

[0106] It will be understood that various aspects of the invention may be provided or combined. For example, embodiments may be provided that include two or more different heat sources, and any combination of heat sources is expressly contemplated. Additionally, the use of light sources and heating to remove hydrogen adsorbed on the pellicle membrane is expressly contemplated. All combinations of light sources and heating are contemplated.

[0098]

[0107] Although particular reference is made herein to the use of lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein has other applications, such as, for example, 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. Substrates referred to herein may be processed, before or after exposure, for example in a track (a tool that typically applies a layer of resist to a substrate and develops the exposed resist), metrology tool, and / or inspection tool. Where appropriate, the disclosure herein may be applied to these and other substrate processing tools. Furthermore, a substrate may be processed multiple times, for example to produce a multi-layer IC, and thus the term substrate as used herein may also refer to a substrate that already includes multiple processed layers.

[0099]

[0108] Whilst specific embodiments of the invention have been described above, it will be appreciated that embodiments of the invention may be practiced otherwise than as described.

[0100]

[0109] The above description is intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the invention as described without departing from the scope of the claims set out below.

[0101]

[0110] In summary, the present disclosure provides an apparatus and method for extending the operational life of pellicle membranes, particularly carbon pellicle membranes, by removing adsorbed hydrogen from the pellicle membrane. Removal can be achieved by one or a combination of heating and irradiation with light within a specific wavelength range. The importance of removing adsorbed hydrogen from carbon pellicles to extend the life of carbon pellicle membranes has not previously been realized, and the present disclosure provides different options that can be used in combination to achieve the benefits of removing adsorbed hydrogen.

Claims

1. 1. An assembly for a lithographic apparatus configured to desorb adsorbed hydrogen from a pellicle membrane by heating the pellicle membrane by one or a combination of: i) providing a heated gas, ii) radiative heating, iii) resistive heating, and iv) inductive heating, and / or by irradiating the pellicle membrane with light having a wavelength of approximately 91 nm to approximately 590 nm.

2. 2. The assembly of claim 1, wherein the assembly includes at least one gas injection unit positioned to provide heated gas to an area of ​​the pellicle membrane surrounding an area of ​​the pellicle membrane through which a radiation beam passes in use.

3. 3. The assembly of claim 2, wherein the at least one gas injection unit is positioned on a Reticle Masking (ReMa) blade, optionally positioned no more than 10 mm, preferably no more than 1 mm, from a leading edge of the ReMa blade.

4. The assembly of claim 3 , wherein the at least one gas injection unit is thermally isolated from the ReMa braid.

5. The assembly of any one of claims 2 to 4, wherein the at least one gas injection unit comprises a sintered metal and / or the at least one gas injection unit comprises a diffuser.

6. The assembly according to any one of claims 2 to 5, wherein the at least one gas injection unit comprises a heater and / or a showerhead.

7. 7. The assembly of any one of claims 1 to 6, wherein the heating gas comprises hydrogen gas, optionally the heating gas is at a temperature of from about 500°C to about 1200°C, optionally from about 600°C to about 1000°C.

8. 8. An assembly according to any one of the preceding claims, wherein the heated gas is provided at a pressure of approximately 10 Pa or more and / or at a velocity of more than 1 m / s, preferably approximately 10 m / s or more, preferably approximately 20 m / s or more.

9. 9. The assembly of claim 1, wherein the assembly includes at least one radiant heater provided on at least one Reticle Masking (ReMa) blade, and optionally the at least one radiant heater is thermally insulated from the at least one ReMa blade.

10. 10. The assembly of claim 1, wherein the radiative heater is selected such that the spectrum of the radiative heater overlaps with the maximum absorption spectrum of the pellicle membrane.

11. 11. The assembly of any one of claims 9 to 10, wherein the at least one radiative heater is configured to manage the amount of IR radiation reflected by a reticle towards a wafer in use, and optionally the at least one radiative heater includes one or more guides configured to direct emitted thermal radiation towards the pellicle membrane, optionally the one or more guides being in the form of metal fins, optionally having a high (R>0.5) reflectivity for the radiation of the heater at grazing incidence (AOI<45 degrees).

12. The assembly of any one of claims 1 to 11, comprising electrical contacts and a power source configured to pass an electrical current through the pellicle membrane in the plane of the pellicle membrane.

13. 13. The assembly of claim 12, wherein the electrical contacts are configured to divide the pellicle membrane into one or more sectors, at least one of the sectors corresponding to an area surrounding an area of ​​the pellicle membrane that is exposed to a radiation beam in use, and the assembly is further configured to pass an electric current to the at least one sector corresponding to an area surrounding an area of ​​the pellicle membrane that is exposed to a radiation beam in use, and optionally the assembly is configured to provide an AC, DC or voltage pulse synchronized to an EUV pulse, and optionally the amplitude of the voltage is limited to approximately 100V.

14. 14. The assembly of claim 1, wherein the assembly is configured to provide a total bias in the range of approximately 1 V to approximately 100 V on the pellicle membrane to at least partially repel etching ions.

15. The assembly according to any one of claims 1 to 14, comprising at least one coil and / or antenna powered by AC current provided on at least one Reticle Masking (ReMa) blade and configured to induce an electric current in the pellicle membrane to heat the pellicle membrane.

16. The assembly of any one of claims 1 to 15, wherein the assembly is configured to heat the peril membrane to a temperature of from about 600°C to about 1200°C.

17. 17. An assembly according to any one of claims 1 to 16, wherein the assembly is configured to provide a thermal load to the pellicle membrane in an area adjacent to an area of ​​the pellicle membrane through which an EUV radiation beam passes in use and configured to limit the thermal load to a region of the pellicle away from the EUV irradiated pellicle area and / or the assembly is configured to heat a portion of the pellicle membrane approximately 1 to 3 cm around an area that is irradiated by EUV radiation in use to a temperature of approximately 600°C to approximately 1200°C and to heat a portion of the pellicle membrane more than approximately 1 to 3 cm around an area that is irradiated by EUV radiation in use to a temperature of approximately 500°C or less, preferably ambient temperature.

18. The assembly of any one of claims 1 to 17, wherein the assembly is configured to illuminate the pellicle membrane with two or more different wavelengths of light in a range of approximately 91 nm to approximately 590 nm.

19. 19. The assembly of any one of claims 1 to 18, wherein the assembly comprises two or more light sources configured to provide light at wavelengths from approximately 91 nm to approximately 590 nm, optionally selected from lamps, lasers or plasma sources.

20. 20. An assembly according to any preceding claim, wherein the assembly is configured to irradiate the pellicle membrane in an area adjacent to an area of ​​the pellicle membrane through which, in use, a beam of EUV radiation passes.

21. The assembly of any one of claims 1 to 20, wherein the assembly is configured to scan the light across the pellicle membrane at a wavelength of from approximately 91 nm to approximately 590 nm.

22. Assembly according to any one of the preceding claims, comprising a light source according to any one of the preceding claims.

23. A light source comprising a UV lamp and a grazing incidence optical element, the light source including an optical path along which light is transmitted from the UV lamp to a target area during nominal use, the grazing incidence optical element being disposed between the UV lamp and the target area so as to block a direct path of particles from the UV lamp to the target area.

24. 24. The light source of claim 23, wherein the light source includes a plurality of grazing incidence optical elements configured to provide a focal point between the UV lamp and the target area.

25. 25. A light source according to claim 23 or 24, wherein an aperture is provided between the grazing optical elements.

26. 26. The light source of claim 25, wherein the light source is configured to provide a different pressure on a side of the aperture where the UV lamp is located than on a side of the aperture where the target area is located.

27. A light source according to any one of claims 23 to 26, wherein the light source is configured such that the light path is arranged substantially vertically, such that particles emitted by the UV lamp are contained by gravity.

28. The light source of any one of claims 23 to 27, wherein the grazing incidence optical element is configured to shape the light produced by the UV lamp.

29. A light source according to any one of claims 23 to 28, wherein at least a part of the grazing incidence optical element is provided with a protective layer stable in hydrogen, optionally said protective layer comprising ruthenium.

30. A method for extending the operational life of a pellicle membrane, the method comprising: i) providing a heated gas for heating at least a portion of the pellicle membrane when irradiated by EUV; heating the at least a portion of the pellicle membrane by one or a combination of ii) radiative heating, iii) resistive heating, and iv) inductive heating; and / or desorbing adsorbed hydrogen from the pellicle membrane by irradiating the pellicle membrane with light having a wavelength of approximately 91 nm to approximately 590 nm.

31. 31. The method of claim 30, wherein the method includes providing the heating gas via at least one gas injection unit positioned on a reticle masking (ReMa) blade.

32. 32. The method of claim 30 or 31, wherein the method comprises heating the gas by means of at least one gas injection unit.

33. 33. The method of any one of claims 30 to 32, wherein the method comprises providing a heated gas at a temperature of from about 500°C to about 1200°C, optionally from about 600°C to about 1000°C, and / or providing a heated gas at a pressure of approximately 10 Pa or more, and / or at a velocity of more than 1 m / s, preferably approximately 10 m / s or more, preferably approximately 20 m / s or more.

34. 34. A method according to any one of claims 30 to 33, comprising heating the pellicle membrane to a temperature of from about 600°C to about 1200°C, preferably the heating being directed primarily to a portion of the pellicle membrane of about 1 to 3 cm around the area which is irradiated by EUV radiation in use.

35. The method of any one of claims 30 to 34, wherein the method comprises illuminating the pellicle membrane with two or more different wavelengths of light in the range of approximately 91 nm to approximately 590 nm.

36. A method according to any one of claims 30 to 35, wherein the method comprises operating a lamp, laser or plasma source to provide light at a wavelength of from approximately 91 nm to approximately 590 nm.

37. A method according to any one of claims 30 to 36, wherein the method comprises irradiating the pellicle membrane in an area adjacent to the area of ​​the pellicle membrane through which, in use, a beam of EUV radiation passes.

38. The method of any one of claims 30 to 37, wherein the method comprises scanning light of a wavelength from approximately 91 nm to approximately 590 nm across the pellicle membrane.

39. A method according to any one of claims 30 to 38, wherein the method comprises generating UV light according to a method according to any one of claims 40 to 43.

40. 1. A method of generating UV light, the method comprising: generating UV light with a UV lamp; directing the UV light to a target area using at least one grazing optical element; and blocking particles generated by the UV lamp to prevent the particles from reaching the target area.

41. 41. The method of claim 40, wherein the method comprises focusing the UV light at a focal point and optionally providing an aperture around the focal point.

42. 42. The method of claim 40 or 41, further comprising providing a pressure differential between the UV lamp and the target area.

43. The method of any one of claims 40 to 42, wherein the method further comprises shaping the UV light into a desired shape or pattern.

44. A lithographic apparatus comprising an assembly according to any one of claims 1 to 21 or a light source according to any one of claims 22 to 29.

45. A reticle masking (ReMa) blade for a lithographic apparatus, the reticle masking (ReMa) blade comprising at least one heater or light source arranged on a side of the blade facing a reticle in use and configured to generate light at a wavelength of approximately 91 nm to approximately 590 nm, optionally the light source being a light source according to any one of claims 22 to 29.

46. Use of an assembly according to any one of claims 1 to 21, a light source according to any one of claims 22 to 29, a method according to any one of claims 30 to 43, a lithographic apparatus according to claim 44, or a reticle masking (ReMa) blade according to claim 45 in a lithographic process or apparatus.

Images