Pellicle membrane, pellicle, and method for manufacturing the same

Abstract

There is provided a pellicle membrane for a lithographic apparatus, said membrane including a core comprising metal silicon carbon nitride. Also described is a pellicle comprising such a pellicle membrane as well as a lithographic apparatus including such a pellicle membrane or pellicle. Also provided is a method of manufacturing a pellicle membrane, the method comprising sputtering a metal silicide target and a silicon carbide target in a gas stream comprising nitrogen to form a metal silicon carbon nitride core, optionally wherein the metal is selected from one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium. The use of such a pellicle membrane, pellicle, lithographic apparatus or method in a lithographic method or apparatus is described.

Description

PELLICLE MEMBRANE, PELLICLE, AND METHOD FOR MANUFACTURING THE SAMECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of EP application 23181712.3 which was filed on 27 June 2023, and which is incorporated herein in its entirety by reference.FIELD

[0002] The present invention relates to a pellicle membrane for a lithographic apparatus, a pellicle assembly for a lithographic apparatus, method of manufacturing a pellicle membrane, and the use of such a pellicle membrane, pellicle assembly or method in a lithographic apparatus or method. The present invention has particular, but not exclusive, application to EUV lithographic apparatuses and methods.BACKGROUND

[0003] A lithographic apparatus is a machine constructed to apply a desired pattern onto a substrate. A 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. a mask) onto a layer of radiation-sensitive material (resist) provided on a substrate.

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

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

[0006] Pellicles may also be provided for protecting optical components other than patterning devices. Pellicles may also be used to provide a passage for lithographic radiation between regions of the lithography apparatus which are sealed from one another. Pellicles may also be used as filters, such as spectral purity filters or as part of a dynamic gas lock of a lithographic apparatus.

[0007] A mask assembly may include the pellicle which protects a patterning device (e.g. a mask) from particle contamination. The pellicle may be supported by a pellicle frame, forming a pellicle assembly. The pellicle may be attached to the frame, for example, by gluing or otherwise attaching apellicle border region to the frame. The frame may be permanently or releasably attached to a patterning device.

[0008] Due to the presence of the pellicle in the optical path of the EUV radiation beam, it is necessary for the pellicle to have high EUV transmissivity. A high EUV transmissivity allows a greater proportion of the incident radiation through the pellicle and reducing the amount of EUV radiation absorbed by the pellicle may decrease the operating temperature of the pellicle. Since transmissivity is at least partially dependent on the thickness of the pellicle, it is desirable to provide a pellicle which is as thin as possible whilst remaining reliably strong enough to withstand the sometimes hostile environment within a lithography apparatus. A pellicle membrane also needs to be sufficient strong to withstand the forces acting upon it when being transported as well as when in use. It is also necessary for a pellicle membrane to avoid distorting imaging, to avoid contaminating critical scanner components, such as by out-gassing, and also to avoid deflecting outside predetermined specified limits.

[0009] The present invention has been devised in an attempt to address at least some of the problems identified above.SUMMARY OF THE INVENTION

[0010] According to a first aspect of the present disclosure, there is provided a pellicle membrane for a lithographic apparatus, said membrane including a core comprising metal silicon carbon nitride. A metal silicon carbon nitride may also be defined as MetalSiy (metal silicide) crystals embedded in a SiyCbNz matrix, wherein wherein b,y,z>0. Preferably, the metal silicon carbon nitride has the formula MeaSiyCbNzwherein a,b,y,z>0. It will be appreciated that the formula may be stoichiometric, however non-stoichiometric variants are also envisaged. The exact amounts can be adjusted depending on the nature of the metal in the compound as well as the operating conditions intended for the pellicle.

[0011] Various material combinations can be envisaged for both the crystals and the matrix. In one variant the metal silicide has a higher thermal emissivity than the matrix material, although the alternative wherein the matrix material has a higher thermal emissivity is also possible. Suitable metal silicides are for example NbSi2, MoSi2, Mo5Si3, Mo3Si, TiSi2, WSi2, NiSi2, PtSi, CoSi2, and TaSi2. Such silicides are generally emissive, wherein TiSi2 has the smaller emissivity. Other silicides may also be suitable, such as silicides of Pd, Ta or V.

[0012] The metal Me may be selected from one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium. Preferably, the metal is molybdenum. Non-limiting examples are Mo5Si3CxNy, MoSi2CN, Mo3SiCN, including other stoichiometric and non-stoichiometric variants.

[0013] The core of a pellicle membrane provides the pellicle with the necessarily physical properties to allow the membrane to withstand the environment within a lithographic apparatus. In particular, the core provides the mechanical strength to tolerate deflection caused by unequal forces acting upon the membrane, such as from different pressures being exerted on different faces of themembrane. It has been found that partially nitriding a metal silicide core, such as molybdenum silicide, thereby forming a metal silicon nitride core, can improve the properties of a pellicle membrane. In particular, without wishing to be bound by scientific theory, it is believed that metal silicide crystals in the metal silicon nitride core provide thermal emissivity, ductility and stiffness, which are all beneficial properties. Even so, the metal silicide crystals also provide brittleness and high tensile mechanical pretension, which are not desirable. The addition of nitrogen to a metal silicide during the growth of the material is believed to provide a silicon rich amorphous silicon nitride phase which segregates when the material is annealed, which provides a matrix with a more relaxed stress state due to the excess silicon, thereby lowering the global mechanical pellicle pre-tension. In addition, the value of y in MetalSiy drops from around 2 to around 0.6, which lowers the pre-tension and increases emissivity. The addition of nitrogen lowers transmissivity to EUV radiation and therefore decreases the production throughput yield of an individual scanner / lithographic apparatus. Although metal silicon nitride pellicle membranes have certain advantages, some issues may remain. For example, during manufacture there may be an increase in the number of breakages of the pellicle membrane. Furthermore, such membranes outgas species from the core material, including silicon and nitrogen, which can contaminate critical components of the lithographic apparatus. Such membranes can also suffer from excessive sagging and sagging drift over time during exposure, and can also oxidise during use as well as during storage, which lowers scanner throughput yield. It has been found that a core comprising metal silicon carbon nitride addresses a number of the issues with existing pellicle membranes. The metal silicon carbon nitride core of the present disclosure has elevated robustness as compared to existing pellicle membranes and has a reduced likelihood of breakage during manufacture, even at very low membrane thickness. In addition, such a core membrane has been found to have around 1 to 1.5% improvement in EUV transmission as compared to an equivalent metal silicon nitride membrane. In addition, it has been found that such membranes are stable during storage in ambient conditions for at least 5 weeks. Existing pellicle membranes continue to oxidise during storage under ambient conditions, which increases the thickness of the native oxide layer and reduces EUV transmissivity, which is not desirable. Metal silicon carbon nitride membranes also have thermal emissivity of around 30% or more, which is eminently suitable for use as a pellicle membrane in a lithographic apparatus, particularly an EUV lithographic apparatus. The mechanical pre-stress of a metal silicon carbon nitride membrane can also be tuned to a value of from around 200 MPa to around 600 MPa, which is also eminently suitable for use as a pellicle membrane in a lithographic apparatus, particularly an EUV lithographic apparatus. The yield strength of a pellicle including a metal silicon carbon nitride core is from around 3 to 4 GPa, which is sufficiently high for use in a lithographic apparatus. Preferably the metal is molybdenum.

[0014] The membrane may include a silicon oxygen carbon nitride capping layer. Such a silicon oxygen carbon nitride layer has been found to be a very stable oxide layer which displays high hardness and good barrier properties, and also has a lower compressive stress as compared to silicon oxide. In addition, silicon oxygen carbon nitride has an etch rate in 0.5% HF acid etchant of around 2 nm / h,where is approximately a factor of ten slower than silicon dioxide. As such, it is more chemically resistant and can serve as an etch stop layer, which is in contrast to a silicon dioxide capping layer, which etches under operating conditions within a lithographic apparatus.

[0015] According to a second aspect of the present disclosure, there is provided a pellicle membrane for a lithographic apparatus, wherein the membrane includes a silicon oxygen carbon nitride capping layer and a core. Optionally, the core includes metal silicon carbon nitride. The metal may be selected from one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium.

[0016] As mentioned in respect of the first aspect of the present disclosure, a silicon oxygen carbon nitride capping layer is a very stable oxide layer with high hardness and good barrier properties, and also has a lower compressive stress as compared to silicon oxide. In addition, silicon oxygen carbon nitride has an etch rate in 0.5% HF acid etchant of around 2 nm / h, where is approximately a factor of ten slower than silicon dioxide. As such, it is more chemically resistant and can serve as an etch stop layer, which is in contrast to a silicon dioxide capping layer, which etches under operating conditions within a lithographic apparatus.

[0017] The features described below relate to each of the first and second aspects of the present disclosure. Reference to metal may include one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium.

[0018] The pellicle membrane may include an a-SiOxCyNzcapping layer, wherein 0 < x < 2, 0 < y < 1, and 0 < z < 1.33. It will be appreciated that the formula may not be stoichiometric.

[0019] The core may include metal silicide and silicon carbonitride. The metal may be selected from one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium, preferably molybdenum. The core may further comprise silicon, silicon nitride, and / or silicon carbide. It will be appreciated that the composition of the core is not necessarily uniform throughout and may be a composite material including different phases.

[0020] The core layer may comprise metal silicide crystals in a nitrided silicon carbide matrix. The metal may be selected from one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium, preferably molybdenum. Without wishing to be bound by scientific theory, it is believed that the molybdenum silicide crystals provide emissivity to the core, which reduces the operating temperature of a pellicle comprising such a core at a given power level. This is advantageous as the additional emissivity allows a pellicle comprising such a core to be operated at higher power or operated at the same power resulting in a lower operating temperature of the pellicle. It has been found that including carbon and nitrogen in the silicon matrix is advantageous as it reduces outgassing, improves manufacturability, and provides desirable pre-tension characteristics and resistance to sagging or wrinkling.

[0021] The membrane may have a thickness of from about 5 nm to about 50 nm, about 5 nm to about 25 nm, about 8 nm to about 20 nm, or about 10 to about 15 nm. Since the pellicle membrane isin the path of a radiation beam used in lithography, it is desirable to make the pellicle membrane as thin as possible to minimise absorption of radiation whilst at the same time ensuring that the pellicle membrane is strong enough to withstand the environment within a lithographic apparatus.

[0022] Metal may be present in the pellicle membrane in an amount of from about 10% to about 40%, from about 15% to about 35%, from about 18% to about 32%, or from about 21% to about 30% (atomic %).

[0023] Silicon may be present in the pellicle membrane in an amount of from about 30% to about 65%, from about 32% to about 60%, from about 34% to about 55%, or from about 37% to about 51% (atomic %).

[0024] Nitrogen may be present in the pellicle membrane in an amount of from about 2% to about 40%, from about 5% to about 30%, from about 8% to about 28%, or from about 10% to about 25% (atomic %).

[0025] Carbon may be present in the pellicle membrane in an amount of from about 2% to about 40%, from about 5% to about 36%, from about 8% to about 33%, or from about 10% to about 30% (atomic %).

[0026] The pellicle membrane may include a capping layer on both faces. Both capping layers may comprise silicon oxygen carbon nitride. In other embodiments, the capping layer on each face is different.

[0027] The capping layer may be self-assembled. By self-assembled, it is understood that the capping layer forms natively when the core material is exposed to oxygen. Alternatively, the capping layer may be formed by sputtering.

[0028] The capping layer may have a thickness of from around 1 nm to around 5nm, from around 2 nm to around 4 nm, or around 3 nm.

[0029] According to a third aspect of the present disclosure, there is provided a pellicle for a lithographic apparatus, the pellicle including a pellicle membrane according to the first or second aspect of the present disclosure and a support frame for supporting the pellicle membrane.

[0030] According to a fourth aspect of the present disclosure, there is provided a lithographic apparatus comprising the pellicle membrane or pellicle according to any of the first to third aspects of the present disclosure.

[0031] According to a fifth aspect of the present disclosure, there is provided a method of manufacturing a pellicle membrane, the method comprising sputtering a metal silicide target and a silicon carbide target in a gas stream comprising nitrogen to form a molybdenum silicon carbon nitide core. The metal may be selected from one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium, preferably molybdenum.

[0032] The method may include varying the concentration of nitrogen in the gas stream to control the amount of nitrogen included in the core.

[0033] According to a sixth aspect of the present disclosure, there is provided the use of a pellicle membrane, pellicle or lithographic apparatus according to any of the first to fourth aspects of the present disclosure, or a method according to the fifth aspect of the present disclosure in a lithographic method or apparatus.

[0034] It will be appreciated that features described in respect of one aspect may be combined with any features described in respect of another aspect and all such combinations are expressly considered and disclosed herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawing in which corresponding reference symbols indicate corresponding parts, and in which:

[0036] Figure 1 depicts a lithographic apparatus according to an aspect of the present disclosure;

[0037] Figure 2 is a schematic depiction of a pellicle according to an aspect of the present disclosure; and

[0038] Figure 3a and 3b are STEM images of a 20 nm MoSiC layer acquired in Bright Field (3a) and High Angle Annular Dark Field (3b).

[0039] The features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and / or structurally similar elements.DETAILED DESCRIPTION

[0040] Figure 1 shows a lithographic system according to the present invention. The lithographic system comprises a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an extreme ultraviolet (EUV) radiation beam RB. 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. A heater (not shown) may be provided in any suitable location, such as in the illumination system IL or projection system PS, in order to provide thermal energy to a substrate W, such as a wafer, positioned on the substrate table WT The illumination system IL is configured to condition the radiation beam RB before it is incident upon the patterning device MA. The projection system is configured to project the radiation beam RB (now patterned by the mask MA) onto the substrate W. The substrate W may include previously formed patterns. Where this is the case, the lithographic apparatus aligns the patterned radiation beam RB with a pattern previously formed on the substrate W. In this embodiment, a pellicle 15 is depicted in the path of the radiation and protecting the patterning device MA. It will be appreciated that the pellicle 15 may be located in any required position and may be used to protect anyof the mirrors in the lithographic apparatus. The patterning device MA may be referred to as the reticle. The support structure MT may be referred to as the reticle stage.

[0041] The radiation 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 at a pressure below atmospheric pressure (e.g. hydrogen) may be provided in the radiation source SO. A vacuum may be provided in illumination system IL and / or the 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 the projection system PS.

[0042] The radiation source SO shown in Figure 1 is of a type which may be referred to as a laser produced plasma (LPP) source. A laser, which may for example be a CO2 laser, is arranged to deposit energy via a laser beam into a fuel, such as tin (Sn) which is provided from a fuel emitter. Although tin is referred to in the following description, any suitable fuel may be used. The fuel may for example be in liquid form, and may for example be a metal or alloy. The fuel emitter may comprise a nozzle configured to direct tin, e.g. in the form of droplets, along a trajectory towards a plasma formation region. The laser beam is incident upon the tin at the plasma formation region. The deposition of laser energy into the tin creates a plasma at the plasma formation region. Radiation, including EUV radiation, is emitted from the plasma during de-excitation and recombination of ions of the plasma.

[0043] The EUV radiation is collected and focused by a near normal incidence radiation collector (sometimes referred to more generally as a normal incidence radiation collector). The collector may have a multilayer structure which is 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, having two ellipse focal points. A first focal point may be at the plasma formation region, and a second focal point may be at an intermediate focus, as discussed below.

[0044] The laser may be separated from the radiation source SO. Where this is the case, the laser beam may be passed from the laser to the radiation source SO with the aid of a beam delivery system (not shown) comprising, for example, suitable directing mirrors and / or a beam expander, and / or other optics. The laser and the radiation source SO may together be considered to be a radiation system.

[0045] Radiation that is reflected by the collector forms a radiation beam RB. 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 RB 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 to an opening in an enclosing structure of the radiation source.

[0046] The radiation beam RB passes from the radiation source SO into the 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. The faceted field mirror device 10 and faceted pupil mirror device 11 together provide the radiation beam RB with a desired cross- sectional shape and a desired angular distribution. The radiation beam RB passes from the illuminationsystem IL and is incident upon the patterning device MA held by the support structure MT. The patterning device MA reflects and patterns the radiation beam RB. The illumination system IL may include other mirrors or devices in addition to or instead of the faceted field mirror device 10 and faceted pupil mirror device 11. A heater may be positioned and configured to provide thermal energy which is reflected by one or more of the mirror devices to the substrate W.

[0047] Following reflection from the patterning device MA the patterned radiation beam RB enters the projection system PS. The projection system comprises a plurality of mirrors 13, 14 which are configured to project the radiation beam RB onto a substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the radiation beam, forming an image with features that are smaller than corresponding features on the patterning device MA. A reduction factor of 4 may for example be applied. Although the projection system PS has two mirrors 13, 14 in Figure 1, the projection system may include any number of mirrors (e.g. six mirrors).

[0048] The radiation sources SO shown in Figure 1 may include components which are not illustrated. For example, a spectral filter may be provided in the radiation source. The spectral filter may be substantially transmissive for EUV radiation but substantially blocking for other wavelengths of radiation such as infrared radiation.

[0049] If the patterning device MA is left unprotected, the contamination can require the patterning device MA to be cleaned or discarded. Cleaning the patterning device MA interrupts valuable manufacturing time and discarding the patterning device MA is costly. Replacing the patterning device MA also interrupts valuable manufacturing time.

[0050] Figure 2 is a schematic depiction of a pellicle assembly 15 in accordance with the present disclosure. The pellicle assembly includes a support 16 that is configured to support the pellicle membrane 17. In the figure, the support 16 appears as two separate elements, although this does not necessarily have to be the case and the support 16 may be in the form of a border which circumscribes the pellicle membrane 17. The pellicle membrane 17 includes a cap layer 18 that is configured to protect the pellicle membrane 17, particularly the emissive core 19, from degradation. The cap layer may be a silicon oxygen carbon nitride capping layer. The emissive core 19 includes a matrix 20, which provides the required pre-tension and strength, such a matrix may comprise nitrided silicon carbide, which is silicon carbide with additional nitrogen included. The matrix material 20 may include one or more of elemental silicon, silicon oxide, and silicon nitride. The emissive layer 19 includes thermally emissive crystals 21 disposed within the matrix 20. The thermally emissive crystals 21 are included to increase the thermal emissivity of the pellicle membrane 17, thereby allowing it to operate at a lower temperature at a given power than would be the case otherwise, or to operate at the same temperature as pellicle membranes not including emissive crystals, but at a higher power. The thermally emissive crystals 21 may comprise metal silicide, such as molybdenum silicide. As such, the core 19 may be a molybdenum silicon carbon nitride composite core material which includes molybdenum silicide in a nitride silicon carbide matrix. In other embodiments the molybdenum may be replaced by any one or more of themetal described herein. In Figure 2, the cap layer 18 is depicted as completely surrounding the emissive core 19. It will be appreciated that in some embodiments, the cap layer 18 is only provided on one or both faces of the emissive core 19 and may not extend around the edges.

[0051] Figures 3a and 3 depict complementary STEM images acquired in Bright Field (3a) and High Angle Annular Dark Field (3b) mode of a 20 nm MoSiC layer. The images depict the irregularly shaped molybdenum silicide crystals in the MoSiC layer. This is believed to be similar to the structure of the MoSiCN layer material of the present disclosure. It is believed that the addition of nitrogen reduces the grain size of the molybdenum since SiN can also form in addition to SiC and molybdenum silicide.

[0052] In summary, the present disclosure provides for a new core material for pellicle membranes for use in lithographic apparatuses. The new core material demonstrates improved EUV transmissivity over existing materials. The present core materials also demonstrates suitable emissivity as well a tunable pre-tension which are suitable for use in an EUV lithographic apparatus. Such a core material also produces a native oxide layer which serves to reduce or eliminate outgassing of core materials, such as silicon or nitrogen, which can contaminate critical components of a lithographic apparatus. The core material of the present disclosure also has increased robustness, meaning that there is little to no breakage during manufacture, even at very low membrane thickness. Similarly, the present disclosure also provides for a cap or capping layer which protects core materials from the conditions within an EUV lithographic apparatus and serves to reduce or eliminate outgassing of materials from the core. Such a capping layer is also suitable for use in pellicle membranes which are used as Dynamic Gas Lock membranes. The capping layer also prevents oxidation of the core material and thereby limits EUV transmissivity degradation over time.

[0053] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described.

[0054] The descriptions above are intended to be illustrative, not limiting. Thus it will be apparent to one skilled in the art that modifications may be made to the invention as described without departing from the scope of the claims set out below.

Claims

CLAIMS1. A pellicle membrane for a lithographic apparatus, said membrane including a core comprising metal silicon carbon nitride.

2. The pellicle membrane according to claim 1 , wherein the metal is selected from one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium.

3. The pellicle membrane according to claim 1 or claim 2, wherein the membrane includes a silicon oxygen carbon nitride capping layer.

4. A pellicle membrane for a lithographic apparatus, wherein the membrane includes a silicon oxygen carbon nitride capping layer and a core, optionally wherein the core includes metal silicon carbon nitride, optionally wherein metal is selected from one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium.

5. The pellicle membrane according to any preceding claim, wherein the pellicle membrane includes an a-SiOxCyNzcapping layer, wherein 0 < x < 2, 0 < y < 1, and 0 < z < 1.33.

6. The pellicle membrane according to any preceding claim, wherein the core includes metal silicide and silicon carbonitride, optionally wherein the layer further comprises silicon, silicon nitride and / or silicon carbide.

7. The pellicle membrane according to any preceding claim, wherein the core layer comprises metal silicide crystals in a nitrided silicon carbide matrix.

8. The pellicle membrane according to any preceding claim, wherein the membrane has a thickness of from about 5 nm to about 50 nm, about 5 nm to about 25 nm, about 8 nm to about 20 nm, or about 10 to about 15 nm.

9. The pellicle membrane according to any preceding claim, wherein the metal is present in the pellicle membrane in an amount of from about 10% to about 40%, from about 15% to about 35%, from about 18% to about 32%, or from about 15% to about 30% (atomic %).

10. The pellicle membrane according to any preceding claim, wherein the silicon is present in the pellicle membrane in an amount of from about 30% to about 65%, from about 32% to about 60%, from about 34% to about 55%, or from about 37% to about 51% (atomic %).

11. The pellicle membrane according to any preceding claim, wherein the nitrogen is present in the pellicle membrane in an amount of from about 2% to about 40%, from about 5% to about 30%, from about 8% to about 28%, or from about 10% to about 25% (atomic %).

12. The pellicle membrane according to any preceding claim, wherein the carbon is present in the pellicle membrane in an amount of from about 2% to about 40%, from about 5% to about 36%, from about 8% to about 33%, or from about 10% to about 30% (atomic %).

13. The pellicle membrane according to any preceding claim, wherein the membrane includes a capping layer on both faces, optionally wherein both capping layers comprise silicon oxygen carbon nitide.

14. The pellicle membrane according to any of claims 2 to 13, wherein the capping layer is selfassembled.

15. A pellicle membrane according to any of claims 13 to 14, wherein the capping layer has a thickness of from around 1 nm to around 5 nm, from around 2 nm to around 4 nm, or around 3 nm.

16. A pellicle for a lithographic apparatus, the pellicle including a pellicle membrane according to any preceding claim and a support frame for supporting the pellicle membrane.

17. A lithographic apparatus comprising the pellicle membrane or pellicle according to any one of claims 1 to 16.

18. A method of manufacturing a pellicle membrane, the method comprising sputtering a metal silicide target and a silicon carbide target in a gas stream comprising nitrogen to form a metal silicon carbon nitride core, optionally wherein the metal is selected from one or more of niobium, molybdenum, titanium, tungsten, platinum, cobalt, tantalum, palladium, or vanadium.

19. The method according to claim 18, wherein the method includes varying the concentration of nitrogen in the gas stream to control the amount of nitrogen included in the core.

20. The use of a pellicle membrane, pellicle or lithographic apparatus according to any one of claims 1 to 17 or a method according to any of claims 18 and 19 in a lithographic method or apparatus.

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