Membrane diaphragm

Abstract

A method for manufacturing a pellicle diaphragm is described, the method comprising: providing a first sacrificial layer on a planar substrate to form a stack; and providing at least a portion of the stack with at least one metal silicide or doped metal silicide pellicle core layer that forms at least a portion of the pellicle diaphragm. Also described is a pellicle diaphragm assembly comprising a substrate, a first sacrificial layer, and at least one metal silicide or doped metal silicide pellicle layer that forms at least a portion of the pellicle core; and a lithographic apparatus comprising such a pellicle.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority from European application No. 19188979.9, filed on July 30, 2019, and European application No. 19194571.6, filed on August 30, 2019, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present invention relates to a method for manufacturing a pellicle membrane. The present invention has particular (but not exclusive) use in conjunction with EUV lithography apparatus and EUV lithography tools. The present invention also relates to pellicle membrane assemblies and lithography apparatus including such assemblies. Background Art

[0004] A lithographic apparatus is a machine configured to apply a desired pattern to a substrate. A lithographic apparatus can be used, for example, in integrated circuit (IC) manufacturing. A lithographic apparatus can, for example, project a pattern from a patterning device (e.g., a mask) onto a layer of radiation-sensitive material (resist) disposed on the substrate.

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

[0006] A patterning device (e.g., a mask or reticle) can be used to impart a pattern to a radiation beam in a lithographic apparatus. Radiation is arranged to pass through or reflect from the patterning device to form an image on a substrate. Contamination on the surface of the patterning device can lead to manufacturing defects on the substrate. A diaphragm assembly (also known as a pellicle) can be provided to protect the patterning device from airborne particles and other forms of contaminants.

[0007] A pellicle may also be provided to protect optical components other than the patterning device. A pellicle may also be used to provide a path for lithographic radiation between sealed zones of a lithographic apparatus. A pellicle may also function as a filter (such as a spectral purity filter) or as part of a dynamic airlock in a lithographic apparatus.

[0008] The use of pellicles in photolithography is well known and recognized. A pellicle in a lithographic apparatus is a membrane (also called a pellicle diaphragm) positioned away from the patterning device and outside the focal plane of the lithographic apparatus in use. Because the pellicle is outside the focal plane of the lithographic apparatus, contaminant particles that land on the pellicle are out of focus. Consequently, the image of the contaminant particles is not projected onto the substrate. If the pellicle were not present, contaminant particles that land on the patterning device would be projected onto the substrate and introduce defects into the projected pattern.

[0009] A mask assembly can include a pellicle that protects a patterning device (e.g., a mask) from particle contamination. The pellicle can be supported by a pellicle frame, thereby forming a pellicle assembly or a diaphragm assembly. The pellicle can be attached to the frame, for example, by gluing or otherwise attaching a pellicle boundary region to the frame. The frame can be permanently or releasably attached to the patterning device. The frame can also be known as a border.

[0010] For example, because diaphragms must be frequently cleaned or replaced when they become contaminated or damaged, it is beneficial to manufacture the diaphragms using high-volume manufacturing techniques.

[0011] Because the pellicle is in the optical path of the EUV radiation beam, it is desirable for the pellicle to have high EUV transmittance. High EUV transmittance allows a larger proportion of the incident radiation to pass through the pellicle. Because 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 maintaining sufficient strength to withstand the sometimes harsh environment within a lithographic apparatus.

[0012] Due to the presence of the pellicle in the optical path of the EUV radiation beam, the pellicle may become hot. High temperatures may damage or fracture the pellicle. It is desirable to reduce the operating temperature of the pellicle or to provide a pellicle that can withstand higher temperatures.

[0013] For example, because the diaphragm is thin, it is difficult to manufacture the diaphragm assembly without deforming or damaging the diaphragm assembly during the process. Damage or defects in the diaphragm assembly may result in undesirable performance degradation, reduced service life, or even rupture.

[0014] Etching is a common manufacturing process used to remove portions of material. In multilayer materials, selective etching can remove portions of a layer, exposing the underlying layer. Overetching can occur when more material than intended is removed. Overetching in pellicle manufacturing can damage the pellicle membrane. Overetching can reduce the strength of the pellicle membrane, which can cause the pellicle membrane to break during manufacturing, shipping, or subsequent use. Therefore, it is desirable to reduce the probability of overetching. It is also desirable to develop a manufacturing process that facilitates the deposition of layers and / or removal of portions of material in a controlled manner to achieve pellicle components with reliable and consistent properties.

[0015] It would be desirable to provide a method of manufacturing a pellicle that provides a pellicle having consistent physical properties, that minimizes damage or defects in the pellicle and that enables high volume manufacturing of the pellicle.The present invention has been designed in an attempt to address at least some of the problems identified above. Summary of the Invention

[0016] According to a first aspect, a method for manufacturing a pellicle diaphragm is provided, the method comprising: providing a first sacrificial layer on a planar substrate to form a stack; and providing at least a portion of the stack with at least one metal silicide or doped metal silicide pellicle core layer forming at least a portion of the pellicle diaphragm.

[0017] Metal silicides and doped metal silicides can be beneficial for use in pellicle membranes due to their high EUV transmittance. Additionally, the high emissivity of metal silicides and doped metal silicides can beneficially lower the operating temperature of the pellicle membrane, thereby reducing the risk of damage to the pellicle membrane while in use. Furthermore, due to the emissivity of metal silicides or doped metal silicides, their use as a pellicle core layer can alleviate or eliminate the need for additional emissive capping layers on the front and / or back of the pellicle membrane. Advantageously, removing the need for emissive capping layers can reduce manufacturing time and / or reduce damage to the pellicle membrane during manufacturing.

[0018] Methods for making other types of pellicle diaphragms, for example, with silicon cores, may be suboptimal for making pellicle diaphragms comprising at least one metal silicide or doped metal silicide pellicle core layer. Methods and related embodiments according to this aspect of the invention may advantageously provide methods for making pellicle diaphragms comprising at least one metal silicide or doped metal silicide pellicle core layer with higher quality and / or higher yield. In particular, providing a first sacrificial layer prior to depositing the metal silicide or doped metal silicide pellicle core layer may advantageously control the properties of the surface for receiving the pellicle core layer, such as the surface morphology. Advantageously, the layer may have at least one of: a low pinhole count, a low roughness, a low dopant particle count, a uniform layer thickness, and / or a negligible amount of air / vacuum between the surface and the pellicle core layer.

[0019] The ratio of metal, silicon and optional dopant in the metal silicide and doped metal silicide can be adjusted as needed.The planar substrate may be referred to simply as a substrate.

[0020] The pellicle core layer can be deposited using physical vapor deposition (PVD). Advantageously, PVD can reduce the amount of raw materials required for deposition. Advantageously, PVD can provide greater control over deposition-related properties, such as the thickness of the pellicle core layer, the uniformity of the pellicle core layer, the ratio of metal, silicon, and (optional) dopants in the pellicle core layer, and / or the repeatability of these properties when processing multiple diaphragms.

[0021] The metal may include platinum. The metal M may be one of a range of metals. For example, the metal may be selected from the group consisting of Ce, Pr, Sc, Eu, Nd, Ti, V, Cr, Zr, Nb, Mo, Ru, Rh, La, Y, and Be. Within this group, preferred metals are zirconium, molybdenum, and beryllium. Molybdenum is most preferred.

[0022] The dopant may include nitrogen. The dopant may be any suitable dopant. For example, the dopant may be oxygen, carbon, boron, or nitrogen. Of these dopants, nitrogen is a preferred dopant.

[0023] The first sacrificial layer may comprise an oxide. The oxide may comprise a thermal oxide. The oxide may be provided by any suitable technique. Annealing of a planar substrate may be used to provide the oxide layer. The first sacrificial layer may be arranged so that the surface of the first sacrificial layer for accommodating at least one pellicle core layer has a high smoothness and / or a high cleanliness. That is, it may have a uniform thickness and / or low roughness, and / or a low dopant particle density. By providing a surface having a high smoothness, the metal silicide or doped metal silicide pellicle core layer may be deposited with high quality. High quality may mean, for example, a low number of pinholes, a uniform layer thickness, and / or a negligible amount of air / vacuum between the surface and the pellicle core layer.

[0024] The method may further comprise providing at least one additional sacrificial layer on the first sacrificial layer prior to providing the at least one pellicle core layer. There may be any number of additional sacrificial layers, for example 1 or 4. Providing additional sacrificial layers may be beneficial in controlling the surface morphology of the surface that receives the at least one pellicle core layer. Beneficially, the layer may be of high quality, for example a low number of pinholes, a uniform layer thickness, and / or a negligible amount of air / vacuum between the surface and the pellicle core layer. The additional sacrificial layers may be referred to as sacrificial layers; that is, a "sacrificial layer" may comprise the first sacrificial layer and optionally one or more additional sacrificial layers. Where the sacrificial layers comprise different materials, each material may have a different etching rate in one etchant than in another etchant. This may therefore allow for highly controlled etching of the stack, as certain sacrificial layers may be resistant to the etchant and over-etching may therefore be avoided.

[0025] The at least one additional sacrificial layer may comprise oxide or silicon. Preferably, the composition of adjacent sacrificial layers may alternate between oxide and silicon. The oxide may be silicon oxide.

[0026] As mentioned, oxide and silicon can have different etch rates. Having different sacrificial layers comprising oxide or silicon can advantageously provide different sacrificial layers with different etch rates. Adjacent layers having different etch rates advantageously allow a layer to serve as an etch stop layer for an adjacent layer.

[0027] The silicon may be doped or undoped silicon or polysilicon, for example, in-situ doped polysilicon. The dopant may be phosphorus or another dopant. The oxide may be silicon dioxide, formed from tetraethylorthosilicate (TEOS), thermal oxide, or any material having similar performance and / or chemical / physical properties to silicon dioxide.

[0028] At least one additional sacrificial layer can be arranged to have a controlled stress within the layer. For example, it can have a tensile stress. Providing stress within the sacrificial layer can advantageously pre-stress the at least one pellicle core layer. Pre-stressing the pellicle core layer can advantageously reduce sagging of the pellicle membrane when it is removed from the substrate and freestanding, as well as when the pellicle membrane is in use.

[0029] The first sacrificial layer may include amorphous carbon. The at least one additional sacrificial layer may include amorphous carbon. Amorphous carbon may be beneficial in reducing overetching during diaphragm fabrication and / or providing a diffusion barrier between layers of the diaphragm-diaphragm assembly and / or prestressing the diaphragm.

[0030] The method may comprise providing three pellicle core layers on the stack. Preferably, the pellicle core layers may be deposited in the following order: a first metal silicide layer, a doped metal silicide layer, and a second metal silicide layer. A pellicle membrane having three core layers may advantageously have high emissivity and / or high EUV transmittance. A pellicle membrane having three core layers may be manufactured with low defectivity. A pellicle membrane comprising an ordered stack of: a first metal silicide layer, a doped metal silicide layer, and a second metal silicide layer may advantageously be manufactured in a relatively simple and / or rapid manner using PVD.

[0031] The method may further comprise one or more etching steps to remove at least a portion of the substrate and one or more sacrificial layers. Removing at least a portion of the substrate and one or more sacrificial layers may define, for example, a boundary or frame around the perimeter of the pellicle membrane. Removing at least a portion of the substrate and one or more sacrificial layers may substantially release the pellicle membrane from the substrate and one or more sacrificial layers. The released pellicle membrane may form part of a pellicle assembly, wherein the pellicle assembly includes the pellicle membrane and a boundary supporting the pellicle membrane. An appropriate etchant may be selected depending on the particular material to be etched.

[0032] The method may include performing at least one etching step after depositing the sacrificial layer and before depositing the pellicle core layer. Such an etching step may define an area to be etched in a subsequent etching step. The defined area may define the overall shape of the final pellicle assembly. The defined area may define, for example, a frame or border around the periphery of the pellicle diaphragm. The etching step may remove at least a portion of at least one of the one or more sacrificial layers. The etching step may optionally remove at least a portion of the substrate. Advantageously, by performing such an etching step before depositing the pellicle core layer to define the area to be etched in a subsequent etching step, damage to the pellicle core layer may be avoided.

[0033] The planar substrate may be a silicon-on-insulator (SOI) wafer. The planar substrate may be a silicon wafer. These types of substrates are well characterized and readily available.

[0034] The planar substrate may be annealed to provide a thermal oxide layer prior to providing the tetraethylorthosilicate layer.

[0035] The final etching step may be a wet etch, preferably a HF wet etch of the tetraethylorthosilicate layer.

[0036] The method may further include a plasma treatment step after the final etching step. The plasma treatment step may remove at least a portion of the amorphous carbon first sacrificial layer or additional sacrificial layers. The plasma treatment may include treatment with free radicals (e.g., hydrogen radicals). Advantageously, the plasma treatment may remove portions of the sacrificial layer (e.g., portions of the sacrificial layer made of an etch-resistant but plasma-sensitive material, such as amorphous carbon) without damaging or removing the pellicle membrane.

[0037] According to an embodiment of the present invention, the method comprises patterning the back side of the stack after providing the first and second sacrificial layers on the planar substrate. The back side is the side or face of the stack opposite the side or face of the stack on which the pellicle core layer is provided. Thus, the back side of the stack is patterned before providing the third sacrificial layer. As explained in more detail below, this provides a manufacturing process that allows the sacrificial layers immediately adjacent to the pellicle core layer to be removed at different stages. This eliminates the need for a wet HF etch at the end of the process, which is advantageous because a wet HF etch could result in damage to the pellicle core layer.

[0038] The method may also include the following sequential steps: i) providing a third sacrificial layer in the form of an oxide to form a bottom oxide; ii) depositing the pellicle core layer on the surface of the stack; iii) optionally depositing a cap layer in the form of another oxide layer on the top surface of the pellicle core layer to form a top oxide layer; iv) annealing the stack; v) optionally removing the top oxide layer (if present) and / or any native oxide layer; vi) patterning the front side of the stack; vii) providing a protective layer to protect the front side of the stack; and viii) performing a cavity etch from the back side of the stack to remove the planar substrate, the first sacrificial layer, a portion of the second sacrificial layer, and optionally, a portion of the third sacrificial layer to define a pellicle assembly.

[0039] In existing processes for manufacturing diaphragm assemblies, silicon oxide layers are positioned directly above and below the diaphragm core layer at the stage when the final freestanding diaphragm is separated from the support wafer. A final wet HF etch stage is required to etch away these sacrificial protective layers. This requires the insertion of a very thin diaphragm, approximately 140 nm, into an etch tank or bath with very or high reactivity. This step often results in a loss of mechanical yield. In addition, when the diaphragm core material (such as MoSiN used in embodiments of the present invention) is etched by HF, local differences in thickness can occur due to the HF etch, which leads to non-uniformity in EUV transmittance. Furthermore, the compressive nature of silicon oxide causes the diaphragm stack to wrinkle before any HF etching and to be subject to vibrations caused by natural vibrations (such as sound). This wrinkled state makes the diaphragm very fragile and difficult to handle or process. The process according to embodiments of the present invention addresses or overcomes these difficulties.

[0040] A third sacrificial layer in the form of an oxide can be provided to form a bottom oxide. The term "bottom oxide" is used to indicate the relative position of this oxide to the core layer of the pellicle at a later stage in the process. This distinguishes the bottom oxide from the top oxide. This sacrificial layer can be provided by any suitable means known in the art, such as chemical or thermal. When formed using chemical methods known in the art (such as DiO3, DiO3 + SC1 + SC2, or DiO3 + SC1), the thickness of the third sacrificial layer can be approximately 0.5 nm to 3 nm. This layer serves as an etch barrier for silicon (ISDP) etching. Previously, it was necessary to remove the bottom oxide layer to increase EUV transmittance. However, it has been found that the very thin nature of chemical oxides limits the impact on EUV transmittance of the bottom oxide layer, thus eliminating the need to etch the bottom oxide. This enables a process flow without an HF etching stage. Alternatively, a thermal oxide layer can be provided. This is also referred to as a dry oxide. This type of oxide can be thermally grown at high temperatures (e.g., temperatures exceeding 900°C) in an oxygen-rich environment. The thickness of this thermal oxide layer can be approximately 5 nm to 15 nm, and can typically be approximately 10 nm. In this flow, since there is no top sacrificial layer, the bottom oxide can be removed as part of the cavity etch before the freestanding diaphragm is separated from the wafer. During the cavity etch, the diaphragm is not freestanding because it is covered by a protective layer, such as a polymer (such as perylene), which can be several microns thick. The thermal oxide can be removed using an HF or BOE bath. The advantage of using a dry oxide is that the base sacrificial ISDP layer is exposed to a high temperature process before the pellicle core layer is deposited on top. This high temperature helps stabilize the ISDP layer, and thus the substrate on which the pellicle core material is deposited. In embodiments where a top oxide is not provided, this allows the pellicle to remain flat throughout the entire process flow, thereby allowing for safer handling.

[0041] In embodiments of the present invention, step iii) is optional. The pellicle membrane has been found to be sufficiently robust to handle subsequent process steps without compromising final performance. Therefore, a top oxide is not necessarily required, and by eliminating this layer, a process flow that does not include HF etching can be provided. Therefore, step v) is also optional.

[0042] The cap layer of step iii) may be formed from TEOS, but any other suitable process as known in the art may be used.

[0043] The protective layer may be formed from a polymeric material such as perylene. Likewise, any suitable protective material known for protecting materials during etching processes may be used.

[0044] The protective layer can be removed to release the pellicle membrane assembly. The protective layer can be removed by oxygen plasma. Therefore, if a final HF etch is not performed, a thin silicon dioxide layer of approximately 1 nm to 2 nm in thickness will remain on top of the pellicle core membrane.

[0045] As described above, the third sacrificial layer may be a chemical oxide or a thermal oxide.

[0046] The method may not include a wet HF etching step. Due to the design of the flow sheet, risky HF etching may not be required during the process.

[0047] This method has been found to reduce EUV transmittance non-uniformity by approximately a factor of 3 due to the elimination of the final HF etch step. As expected from minimizing EUV transmittance non-uniformity, this method provides an improved final pellicle product that would not be achievable using other processes. Thus, by having an EUV transmittance non-uniformity of less than 0.15%, the final product is distinguishable from seemingly similar pellicle components.

[0048] According to a second aspect of the present invention, a diaphragm assembly is provided, comprising a substrate, a first sacrificial layer, and at least one metal silicide or doped metal silicide diaphragm layer forming at least a portion of a diaphragm core.

[0049] Metal silicides and doped metal silicides can be beneficial for use in pellicle membranes due to their high EUV transmittance. Furthermore, the high emissivity of metal silicides and doped metal silicides can beneficially lower the operating temperature of the pellicle membrane, thereby reducing the risk of damage to the pellicle membrane while in use. Furthermore, due to the emissivity of metal silicides or doped metal silicides, their use as a pellicle core layer can alleviate or eliminate the need for additional emissive capping layers on the front and / or back of the pellicle membrane. Advantageously, eliminating the need for emissive capping layers can reduce manufacturing time and / or reduce damage to the pellicle membrane during manufacturing. Thus, assemblies according to the present invention can support improved pellicle membranes. For example, the pellicle membrane can be of higher quality and / or can be produced at a higher yield compared to other pellicle membranes. The pellicle membrane can have higher transmittance and higher emissivity compared to other pellicle membranes.

[0050] The assembly may further comprise at least one additional sacrificial layer disposed between the first sacrificial layer and the at least one pellicle core layer. There may be any number of additional sacrificial layers, for example one or four. Providing additional sacrificial layers may be beneficial in controlling the surface topography of the surface receiving the at least one pellicle core layer (e.g., to increase smoothness). Additional sacrificial layers may be referred to as sacrificial layers; that is, a "sacrificial layer" may comprise the first sacrificial layer and optionally one or more additional sacrificial layers. Additionally, different sacrificial layers may be selected that have improved adhesion properties between layers. For example, there may be a reduced lattice mismatch between the layers, which reduces the probability of delamination.

[0051] The assembly may comprise at least three sacrificial layers.The first sacrificial layer and the second sacrificial layer may comprise the same material, preferably, wherein the material is a thermal oxide, preferably silicon oxide.

[0052] At least one pellicle core layer may comprise a first pellicle core layer, a second pellicle core layer and a third pellicle core layer. Preferably, the first pellicle core layer and the third pellicle core layer may comprise a metal silicide, and the second pellicle core layer may comprise a doped metal silicide. The metal may be molybdenum. A pellicle membrane having three core layers may advantageously have high emissivity and / or high EUV transmittance. A pellicle membrane having three core layers may be manufactured with low defectivity. A pellicle membrane comprising an ordered stack of a first metal silicide layer, a doped metal silicide layer and a second metal silicide layer may advantageously be manufactured in a relatively simple and / or rapid manner using PVD.

[0053] The substrate may form at least a portion of a boundary that holds or supports the pellicle membrane.

[0054] The boundary can comprise an ordered sequence of a portion of a planar substrate and at least one sacrificial layer, wherein the at least one sacrificial layer is adjacent to the pellicle membrane / core. The pellicle assembly can be fabricated by depositing at least one metal silicide or doped metal silicide pellicle core layer that forms part of the pellicle membrane, wherein the assembly comprises a substrate and one or more sacrificial layers; and selectively etching one or more portions of the substrate to define the boundary. Thus, the boundary can be compositionally similar to the assembly, wherein if the stack is an ordered sequence of a substrate and one or more sacrificial layers, the boundary will comprise multiple portions of the corresponding ordered sequence of the substrate and one or more sacrificial layers.

[0055] The at least one sacrificial layer may comprise oxide or silicon. Preferably, the composition of adjacent sacrificial layers may alternate between oxide and silicon.

[0056] Oxide and silicon can have different etch rates. Having different sacrificial layers comprising oxide or silicon can advantageously provide different sacrificial layers with different etch rates. Adjacent layers having different etch rates advantageously allow a layer to serve as an etch stop layer for an adjacent layer.

[0057] The silicon can be doped or undoped silicon or polysilicon, for example, the silicon can be in-situ doped polysilicon. The dopant can be a phosphor or another dopant. The oxide can be silicon dioxide, tetraethyl orthosilicate (TEOS), thermal oxide, or any material that behaves similarly to silicon dioxide.

[0058] At least one additional sacrificial layer can be arranged to have a controlled stress within the layer. For example, it can have a tensile stress. Providing stress within the sacrificial layer can advantageously pre-stress the at least one pellicle core layer. Pre-stressing the pellicle core layer can advantageously reduce sagging of the pellicle membrane when it is removed from the substrate and freestanding, as well as when the pellicle membrane is in use.

[0059] A sacrificial layer adjacent to the diaphragm membrane may include an oxide and may be substantially thinner than the diaphragm membrane.

[0060] By thin, it is meant that the thickness of the sacrificial layer adjacent to the pellicle membrane is substantially less than the thickness of the pellicle membrane. The sacrificial layer adjacent to the pellicle membrane may be known as a thin oxide layer. Thin oxide layers are easily grown to a well-known layer thickness. The thin oxide layer adjacent to the pellicle membrane can provide a smooth surface for the pellicle membrane. The thin oxide layer adjacent to the pellicle membrane can take advantage of the low defectivity of the pellicle membrane.

[0061] The first sacrificial layer or at least one additional sacrificial layer may include amorphous carbon. Amorphous carbon may be beneficial in reducing overetching during diaphragm fabrication and / or providing a diffusion barrier between layers of the diaphragm-membrane assembly and / or prestressing the diaphragm membrane.

[0062] The sacrificial layer adjacent to the pellicle membrane may include amorphous carbon. The sacrificial layer adjacent to the pellicle membrane may be substantially thinner than the pellicle membrane. Advantageously, the thin amorphous carbon sacrificial layer may provide a beneficial amount of overetch reduction and / or diffusion reduction, and / or prestress.

[0063] The first and third pellicle layers may comprise metal silicide. The second pellicle core layer may comprise amorphous carbon. Advantageously, the amorphous carbon pellicle core layer may provide tension in the pellicle membrane. Advantageously, the amorphous carbon pellicle core layer may reduce sagging in the pellicle membrane.

[0064] According to a third aspect of the present invention, there is provided a method of manufacturing a pellicle membrane, the method comprising providing at least one amorphous carbon layer adjacent to a pellicle layer forming at least a portion of the pellicle membrane.

[0065] Amorphous carbon can beneficially reduce over-etching during diaphragm fabrication and / or provide a diffusion barrier between layers of a diaphragm-membrane assembly and / or pre-stress the diaphragm membrane.

[0066] The pellicle core layer may include a metal silicide or a doped metal silicide. Metal silicides and doped metal silicides may be beneficial for use in pellicle membranes due to their high EUV transmittance. Additionally, the high emissivity of metal silicides and doped metal silicides may beneficially reduce the operating temperature of the pellicle membrane, thereby reducing the risk of damage to the pellicle membrane while in use. Furthermore, due to the emissivity of metal silicides or doped metal silicides, their use as a pellicle core layer may mitigate or eliminate the need for additional emissive cover layers on the front and / or back of the pellicle membrane. Advantageously, removing the need for emissive cover layers may reduce manufacturing time and / or reduce damage to the pellicle membrane during manufacturing.

[0067] According to a fourth aspect of the present invention, a pellicle diaphragm assembly is provided, comprising a substrate, at least one amorphous carbon layer, and a pellicle diaphragm.

[0068] Amorphous carbon can beneficially reduce over-etching during diaphragm fabrication and / or provide a diffusion barrier between layers of a diaphragm-membrane assembly and / or pre-stress the diaphragm membrane.

[0069] The pellicle core layer may include a metal silicide or a doped metal silicide. Metal silicides and doped metal silicides may be beneficial for use in pellicle membranes due to their high EUV transmittance. Additionally, the high emissivity of metal silicides and doped metal silicides may beneficially reduce the operating temperature of the pellicle membrane, thereby reducing the risk of damage to the pellicle membrane while in use. Furthermore, due to the emissivity of metal silicides or doped metal silicides, their use as a pellicle core layer may mitigate or eliminate the need for additional emissive cover layers on the front and / or back of the pellicle membrane. Advantageously, removing the need for emissive cover layers may reduce manufacturing time and / or reduce damage to the pellicle membrane during manufacturing.

[0070] The thickness of the amorphous carbon layer may be substantially thinner than the pellicle membrane.Beneficially, a thin amorphous carbon sacrificial layer may provide a beneficial amount of over-etch reduction and / or diffusion reduction, and / or pre-stress.

[0071] The substrate may form at least a portion of a boundary retaining the pellicle membrane.

[0072] One or more etching steps may be used to remove at least a portion of the substrate and, if present, one or more sacrificial layers to define the boundaries. An appropriate etchant may be selected based on the specific material being etched. The final etching step may be a wet etch. Preferably, the tetraethyl orthosilicate layer is etched using HF wet etching.

[0073] The border may be referred to as a frame. The border may, for example, extend around the perimeter of the pellicle membrane. Removing at least a portion of the substrate and the one or more sacrificial layers may substantially release the pellicle membrane from the substrate and the one or more sacrificial layers.

[0074] The released pellicle membrane may form part of a pellicle assembly, wherein the pellicle assembly includes the pellicle membrane and a border supporting the pellicle membrane.

[0075] The planar substrate may be a silicon-on-insulator (SOI) wafer. The planar substrate may be a silicon wafer. These types of substrates are well characterized and readily available.

[0076] The planar substrate may be annealed to provide a thermal oxide layer prior to providing the tetraethylorthosilicate layer.

[0077] The boundary comprises an ordered stack of a portion of a planar substrate and a portion of an amorphous carbon layer, wherein the at least one amorphous carbon layer is adjacent to the pellicle membrane.

[0078] According to a fifth aspect of the present invention, a lithographic apparatus is provided, comprising the pellicle assembly described above or any one of the pellicle membranes or pellicle assemblies manufactured according to any one of the aforementioned technical solutions.

[0079] Features described in relation to any of these aspects may be combined with features described in relation to any of the other aspects of the invention.

[0080] The invention will now be described with reference to EUV lithography apparatus.However, it will be appreciated that the invention is not limited to EUV lithography and may be applicable to other types of lithography. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which:

[0082] - Figure 1 Describes a lithographic system including a lithographic apparatus and a radiation source;

[0083] - Figure 2 Describe the membrane components;

[0084] - Figure 3 illustrates stages of fabrication of a diaphragm membrane and a diaphragm assembly according to an embodiment of the present invention;

[0085] - Figure 4 illustrates stages of manufacturing a diaphragm membrane and a diaphragm assembly according to another embodiment of the present invention;

[0086] - Figure 5 Schematic diagram of the manufacturing stages of a diaphragm membrane and a diaphragm assembly according to another embodiment of the present invention;

[0087] - Figure 6 illustrates stages of manufacturing a diaphragm membrane and a diaphragm assembly according to another embodiment of the present invention;

[0088] - FIG. 7 illustrates a stage in the manufacture of a diaphragm membrane and a diaphragm assembly according to another embodiment of the invention; and

[0089] - Figure 8 A flow chart illustrating the manufacture of a pellicle assembly is shown. DETAILED DESCRIPTION

[0090] Figure 1 A lithographic system is shown comprising a radiation source SO and a lithographic apparatus LA. The radiation source SO is configured to generate an EUV radiation beam B and to supply the EUV radiation beam B to the lithographic apparatus LA. The lithographic apparatus LA comprises an illumination system IL, a support structure MT configured to support a patterning device MA (e.g., a mask), a projection system PS, and a substrate table WT configured to support a substrate W.

[0091] The illumination system IL is configured to condition the EUV radiation beam B before it is incident on the patterning device MA. In addition, the illumination system IL may include a faceted field mirror arrangement 10 and a faceted pupil mirror arrangement 11. The faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11 together provide an EUV radiation beam B having a desired cross-sectional shape and a desired intensity distribution. In addition to or as an alternative to the faceted field mirror arrangement 10 and the faceted pupil mirror arrangement 11, the illumination system IL may include other mirrors or arrangements.

[0092] After being conditioned in this way, the EUV radiation beam B interacts with the patterning device MA. Due to this interaction, a patterned EUV radiation beam B' is generated.

[0093] Pellicle assembly 15 is depicted in the path of the radiation to protect patterning device MA. Pellicle assembly 15 comprises a pellicle membrane 19 and a frame 17 that supports the pellicle membrane 19. Frame 17 may be referred to as a boundary. Pellicle membrane 19 comprises a membrane that is substantially transparent to EUV radiation (although it will absorb a small amount of EUV radiation). Pellicle membrane 19 serves to protect patterning device MA from particle contamination. Pellicle membrane 19 may be referred to simply as a pellicle. It will be appreciated that pellicle assembly 15 may be located in any desired location and may be used to protect any element of a lithographic apparatus, such as one or more of the mirrors in the lithographic apparatus.

[0094] Despite efforts to maintain a clean environment within the lithographic apparatus LA, particles may still be present within the lithographic apparatus LA. In the absence of the pellicle membrane 19, particles may be deposited onto the patterning device MA. Particles on the patterning device MA may adversely affect the pattern imparted to the radiation beam B and, therefore, the pattern transferred to the substrate W. The pellicle membrane 19 provides a barrier between the patterning device MA and the environment within the lithographic apparatus LA to prevent particles from being deposited on the patterning device MA.

[0095] In use, the pellicle membrane 19 is positioned a distance from the patterning device MA that is sufficient so that any particles incident on the surface of the pellicle membrane 19 are not located in the focal plane of the radiation beam B. This separation between the pellicle membrane 19 and the patterning device MA serves to reduce the extent to which any particles on the surface of the pellicle membrane 19 impart a pattern to the radiation beam B. It will be appreciated that, in the event that a particle is present in the radiation beam B but not in the focal plane of the radiation beam B (i.e., not at the surface of the patterning device MA), then any image of the particle will not be focused at the surface of the substrate W. In some embodiments, the separation between the pellicle membrane 19 and the patterning device MA may be, for example, between 2 mm and 3 mm (e.g., approximately 2.5 mm). In some embodiments, the separation between the pellicle membrane 19 and the patterning device MA may be adjustable.

[0096] After generating the patterned EUV radiation beam B', the projection system PS is configured to project the patterned EUV radiation beam B' onto the substrate W. For this purpose, the projection system PS may comprise a plurality of mirrors 13, 14 configured to project the patterned EUV radiation beam B' onto the substrate W held by the substrate table WT. The projection system PS may apply a reduction factor to the patterned EUV radiation beam B', thereby forming an image having features that are smaller than corresponding features on the patterning device MA. For example, a reduction factor of 4 or 8 may be applied. Although the projection system PS is illustrated as having only Figure 1, but the projection system PS may comprise a different number of mirrors (eg six or eight mirrors).

[0097] The substrate W may include a previously formed pattern. In such a case, the lithographic apparatus LA aligns the image formed by the patterned EUV radiation beam B′ with the pattern previously formed on the substrate W.

[0098] A relative vacuum, ie, a small amount of gas (eg, hydrogen) at a pressure well below atmospheric pressure, may be provided in radiation source SO, in illumination system IL and / or in projection system PS.

[0099] Figure 1 The radiation source SO shown in FIG. 1 is of a type that can be referred to as a laser produced plasma (LPP) source, for example. A laser system 1, which can include, for example, a CO2 laser, is arranged to deposit energy via a laser beam 2 into a fuel, such as tin (Sn), provided from, for example, a fuel emitter 3. Although tin is mentioned in the following description, any suitable fuel may be used. The fuel can, for example, be in liquid form and can be, for example, a metal or alloy. The fuel emitter 3 can include a nozzle configured to direct the tin, for example, in the form of droplets, along a trajectory toward a plasma formation region 4. The laser beam 2 is incident on the tin at the plasma formation region 4. The deposition of laser energy into the tin generates a tin plasma 7 at the plasma formation region 4. Radiation, including EUV radiation, is emitted from the plasma 7 during deexcitation and recombination of electrons and ions of the plasma.

[0100] EUV radiation from the plasma is collected and focused by a collector 5. The collector 5 comprises, for example, a near-normal-incidence radiation collector 5 (sometimes more generally referred to as a normal-incidence radiation collector). The collector 5 may comprise a multilayer mirror structure arranged to reflect EUV radiation (e.g., EUV radiation having a desired wavelength, such as 13.5 nm). The collector 5 may have an elliptical configuration with two focal points. A first of the focal points may be located at the plasma formation region 4, and a second of the focal points may be located at an intermediate focus 6, as discussed below.

[0101] The laser system 1 may be spatially separated from the radiation source SO. In such a case, the laser beam 2 may be delivered from the laser system 1 to the radiation source SO by means of a beam delivery system (not shown) comprising, for example, suitable directing mirrors and / or a beam expander and / or other optical devices. The laser system 1, the radiation source SO, and the beam delivery system may together be considered a radiation system.

[0102] The radiation reflected by the collector 5 forms an EUV radiation beam B. The EUV radiation beam B is focused at an intermediate focus 6 to form an image at the intermediate focus 6 of a plasma present in the plasma formation region 4. The image at the intermediate focus 6 serves as a virtual radiation source for illuminating the system IL. The radiation source SO is arranged so that the intermediate focus 6 is located at or near an opening 8 in an enclosure 9 of the radiation source SO.

[0103] Although Figure 1 The radiation source SO is depicted as a laser produced plasma (LPP) source, but any suitable source such as a discharge produced plasma (DPP) source or a free electron laser (FEL) may be used to generate EUV radiation.

[0104] Figure 2 The figure schematically illustrates the pellicle assembly 15 and the patterning device MA in cross-section and in greater detail. The patterning device MA has a patterned surface 24. The pellicle frame 17 (or "frame") supports the pellicle membrane 19 around a peripheral portion of the pellicle membrane 19. The pellicle frame 17 may include an attachment mechanism 22 configured to allow the pellicle frame 17 to be removably attached to the patterning device MA (i.e., to allow the pellicle frame 17 to be attached to and detached from the patterning device MA). The attachment mechanism 22 is configured to engage with an attachment feature (not shown) provided on the patterning device MA. The attachment feature may be, for example, a protrusion extending from the patterning device MA. The attachment mechanism 22 may, for example, include a locking member that engages with the protrusion and secures the pellicle frame 17 to the patterning device MA. The pellicle frame 17 may be attached to the mask via another pellicle frame. Multiple attachment mechanisms and associated attachment features may be provided. The attachment mechanisms may be distributed around the pellicle frame 17 (e.g., two attachment mechanisms on one side of the frame and two attachment mechanisms on opposite sides of the frame). Associated attachment features may be distributed around the perimeter of the patterning device MA. It will be appreciated that any other attachment mechanism or positioning method may be used to position the pellicle membrane 19 in a desired location.

[0105] Figure 2A contaminant particle 26 is schematically shown in FIG. Contaminant particle 26 is incident on and retained by the pellicle membrane 19. The pellicle membrane 19 holds the contaminant particle sufficiently away from the patterned surface 24 of the mask MA so that it is not imaged onto the substrate by the lithographic apparatus LA. A pellicle assembly according to embodiments of the present invention can allow for the provision of a mask pattern (protected from contamination by the pellicle) that remains substantially defect-free during use.

[0106] The pellicle assembly 15 can be constructed by depositing a pellicle membrane 19 directly on top of a substrate on which the frame 17 will be located. The substrate can be, for example, a silicon wafer or an SOI wafer. After depositing the film defining the pellicle membrane 19, the substrate can be selectively etched back to remove the central portion of the substrate and retain only the outer periphery to form the frame 17 used to support the pellicle membrane 19. The fabrication process is further discussed below.

[0107] Phalaris are known in the art and typically have a core layer made of silicon (e.g., polysilicon). The applicant has recognized that various other materials may be beneficial. In particular, the applicant has found that metal silicides or doped metal silicides may be beneficial.

[0108] The doped metal silicide can be represented by the formula M x (Si) y D z , wherein M represents metal, Si represents silicon, and D represents dopant. The subscripts x, y, and z represent the relative ratios of M, Si, and D, respectively.

[0109] The metal M can be one of a variety of metals. For example, the metal can be selected from the group consisting of Ce, Pr, Sc, Eu, Nd, Ti, V, Cr, Zr, Nb, Mo, Ru, Rh, La, Y, and Be. Within this group, the preferred metal is zirconium, molybdenum, or beryllium. Molybdenum is most preferred.

[0110] The dopant D may be one of a range of dopants. For example, the dopant may be oxygen, carbon, boron or nitrogen. Of these, nitrogen is the preferred dopant.

[0111] Of particular interest are molybdenum silicon nitride (MoSiN) and molybdenum silicide (MoSi). The relative ratios of molybdenum, silicon, and (optionally) nitrogen can be varied.

[0112] The deposition of metal silicide or doped metal silicide will sometimes be described below with reference to MoSiN and MoSi, but it should be understood that the following process can be applied to any metal silicide or doped metal silicide.

[0113] Metal silicides are emissive, or radioactive, materials. They are often desirable for diaphragms within lithographic equipment (or any system where the diaphragm is exposed to a radiation beam). Emissive materials can emit infrared radiation and, therefore, lose the heat they have gained by absorbing radiation. As stated above, heating the diaphragm is problematic and can lead to damage and / or fracture. Emissive materials can beneficially lower the operating temperature of the diaphragm, which in turn can extend the life of the diaphragm and / or reduce damage to the diaphragm.

[0114] Typically, pellicles are not highly emissive, meaning they do not possess a high degree of radioactivity, but are treated with emissive materials such as ruthenium, molybdenum, and / or zirconium. For example, pellicles with a silicon core layer must be treated to increase their emissivity. This is accomplished by applying an emissive capping layer to the front and / or back of the pellicle membrane. This capping layer is often applied to a separate pellicle, for example, by depositing the emissive material onto a pellicle membrane that is freely suspended within a pellicle membrane frame. This process can be referred to as deposition onto a separate pellicle. Due to its location as the final or near-final processing step in the production line, this process can also be referred to as back-end-of-line processing. Significant manufacturing difficulties arise from back-end processing. In particular, due to the independent nature of the pellicle membrane, it is susceptible to damage. Furthermore, if any damage occurs at this stage in the production line, the entire process must be repeated, resulting in significant delays. Therefore, reducing or eliminating back-end processing is beneficial.

[0115] The applicants have realised that by using an emissive material such as a metal suicide or doped metal suicide as the core layer in the pellicle, additional processing (and therefore post-processing) to increase the emissivity can be reduced or avoided altogether.

[0116] However, typical production lines and techniques used to manufacture typical pellicles are not suitable for manufacturing pellicles using metal silicide or doped metal silicide as the core layer, especially when high-volume manufacturing capacity or capability for pellicles is required. Therefore, the present applicant has developed a manufacturing technology that allows for manufacturing pellicles using metal silicide or doped metal silicide as the core layer.

[0117] Typically, chemical vapor deposition (CVD) is used to deposit the surface core layer, such as silicon. However, this is not the optimal process for depositing doped metal silicides. This is partly because CVD is a stoichiometric process, and therefore it is difficult to control the amount of dopant within the material.

[0118] On the other hand, physical vapor deposition (PVD) is preferably used rather than CVD to deposit doped metal silicides. Advantageously, PVD offers better process control, allowing for more controlled dopant levels. Furthermore, PVD offers better process control regarding the thickness, uniformity, and repeatability of doped metal silicide and metal silicide deposition. An additional advantage of PVD is its directionality: because it deposits directionally, it is relatively easy to select the area for deposition, unlike CVD, which can deposit material in undesirable areas. For example, when depositing material onto a substrate, PVD relatively easily deposits material onto one surface (or just one area) of the substrate, whereas CVD will preferably deposit material onto all surfaces of the substrate. Deposition onto just one surface or area means reduced raw material usage, which can be advantageous for cost and environmental reasons, for example. Reduced raw material usage also helps reduce contamination, as material can be removed later in the manufacturing process from undesirable areas that could potentially contaminate the pellicle membrane, processing equipment, or lithographic equipment.

[0119] There are some initial disadvantages to using PVD, which are overcome by the methods of embodiments of the present invention.

[0120] Depositing a pellicle layer comprising a metal silicide or doped metal silicide onto a substrate has the disadvantage that the layer will not be conformable. For example, if the substrate has any surface texture, the pellicle layer will not perfectly, i.e., adequately, cover all surface features, and defects may form. For example, pinholes (i.e., gaps) may exist in the layer, there may be areas of greater or lesser depth, and / or there may be "bridging" features whereby air is present between a portion of the layer and the substrate. Bridging features are particularly common between two adjacent surface features of a substrate, and are where the layer covering the features does not contact the surface between the features, but is suspended between the features. All of these defects can reduce the quality of the resulting pellicle film and can, for example, lead to fractures. Bridging features are particularly problematic because these overhanging areas can fracture during manufacturing or in use, and can contaminate the pellicle membrane, or other areas of the manufacturing equipment or lithographic apparatus.

[0121] Another disadvantage is that, due to the directional nature of the process, PVD typically processes one (or a small number of) wafers at a time. Consequently, manufacturing speeds are relatively slow compared to conventional methods. This speed must be increased to enable mass production of metal silicide and doped metal silicide films.

[0122] The applicant has developed a process for producing a membrane having a metal silicide or doped metal silicide membrane layer with the desired quality and yield. Figures 3 to 5 and FIG7 to describe the manufacturing process.

[0123] It should be noted that the drawings are intended to be illustrative / illustrative and, as such, are not drawn to scale. This is particularly important when considering, for example, the thickness of a surface film layer relative to, for example, a planar substrate. This is also particularly important when considering the stages of manufacturing. Key stages of manufacturing are shown, but it should be understood that these stages are illustrative or exemplary in nature, and that additional steps and processes may be performed before, during, between, and / or after the steps shown. In addition, some stages may be illustrated as a single step (e.g., an etching process), but in reality, they may be performed as several sequential smaller processes, with the overall effect illustrated by a single step.

[0124] The following process involves etching. Etching is a common manufacturing process used to remove portions of material. In multilayer materials, selective etching can remove portions of outer layers, exposing underlying layers. Etching can include providing a resist (e.g., a photoresist) and patterning the resist. The present invention is not particularly limited by the nature of the resist, and any suitable resist can be used. The resist is used to protect the underlying layer from etching. Thus, patterning the resist is used to define areas of the stack that are removed by subsequent etching steps. The etchant can be a chemical etchant, such as, for example, phosphoric acid and / or hydrofluoric acid.

[0125] Figure 3 Stages of manufacture of a pellicle assembly 15 according to an embodiment of the invention are schematically illustrated.The pellicle assembly (and precursor stage) is shown in cross-section.

[0126] A planar substrate is provided, which may be referred to simply as substrate 30. Substrate 30 may be, for example, a silicon wafer. For example, substrate 30 may have a shape such as square, circular, or rectangular. The shape of substrate 30 is not particularly limited, but is most likely circular, as it is the most commonly available shape. The size of substrate 30 is not particularly limited.

[0127] The first sacrificial layer 31 is provided, for example, by depositing the first sacrificial layer 31 on the substrate 30. The substrate 30 and the first sacrificial layer 31 may together be referred to as a stack. The first sacrificial layer 31 preferably substantially surrounds the substrate 30, but in some embodiments, the first sacrificial layer may only partially surround the substrate 30. The first sacrificial layer may comprise an oxide, such as silicon oxide or thermal oxide. The first sacrificial layer 31 advantageously provides a substantially flat surface in preparation for receiving a pellicle layer. Additionally or alternatively, depending on the choice of the first sacrificial layer 31, a substantially clean and / or pinhole-free and / or uniform surface may advantageously be provided in preparation for receiving a pellicle layer. That is, the first sacrificial layer controls the surface morphology.

[0128] The pellicle membrane 19 is provided on the surface of the first sacrificial layer 31. That is, the pellicle membrane 19 is provided on the surface of the stack. The pellicle membrane 19 may include one or more pellicle layers. Figure 5 Some example embodiments of multilayer diaphragms are further described. Figure 3 The pellicle membrane 19 shown in FIG. 1 comprises a single pellicle layer comprising a doped metal silicide, which will form the core layer of the pellicle membrane 19 .

[0129] As previously discussed, metal silicides and doped metal silicides can be deposited by physical vapor deposition (PVD). Because depositing metal silicides or doped metal silicides in this manner results in non-conformal coating, it is important to provide a smooth and / or clean (i.e., low number / density of contaminant particles) surface beneath the pellicle membrane 19 (i.e., the surface on which the pellicle layer is deposited). On the other hand, a rough and / or contaminated surface may result in pores in the pellicle layer and / or contamination of the pellicle and other equipment discussed above.

[0130] Additionally or alternatively, the surface beneath the pellicle membrane 19 may be optimized by advantageously controlling the surface topography. Thus, additionally or alternatively, for a smooth and / or clean surface, the surface may advantageously have a low number of pinholes and / or a uniform layer thickness.

[0131] Compared to coating onto the substrate 30, applying the first sacrificial layer 31 can advantageously provide an optimized surface. The first sacrificial layer 31 can be tailored to provide greater smoothness; for example, a thicker first sacrificial layer 31 can provide a smoother surface. The first sacrificial layer 31 can be tailored to provide a surface that is relatively free of contaminant particles and / or has a uniform layer thickness and / or a low number of pinholes. Alternatively (or additionally), an additional sacrificial layer can be added between the first sacrificial layer 31 and the pellicle membrane 19.

[0132] After depositing the pellicle membrane 19, the substrate 30 and the first sacrificial layer 31 can be selectively etched back to remove the central portion of the sacrificial layer and the substrate and retain only the outer periphery to form the frame 17, which is used to support the pellicle membrane 19. The frame 17 thus includes a portion of the substrate 30 and a portion of the first sacrificial layer 31, wherein the first sacrificial layer 31 is disposed between the substrate 30 and the pellicle membrane 19.

[0133] The pellicle layer comprises a doped metal silicide, some of the benefits of which are discussed above. Specifically, the pellicle layer is emissive, which eliminates the need for back-end processing—any additional processing steps after etching back the substrate 30 and the first sacrificial layer 31 to form the frame 17 of the pellicle assembly 15. Eliminating this process reduces the risk of damage to the pellicle membrane 19 and increases the speed of manufacturing a single pellicle assembly 15. This speed increase is due in part to the elimination of back-end processing steps. It is also due in part to the fact that only one emissive layer deposition step is required (as opposed to two, which are beneficial for conventional silicon pellicles because both the front and back layers must be coated). This is particularly significant because, in a typical production line, the emissive layer deposition step can be a "bottleneck" tool that significantly increases the processing time of a pellicle assembly. Therefore, reducing the number of emissive layer deposition steps can significantly reduce the processing time of a pellicle assembly.

[0134] Figure 3 A stack with one sacrificial layer is depicted, but additional sacrificial layers may be provided. Any number (eg, 1 or 4) of additional sacrificial layers may be provided. Figure 4 The present invention schematically illustrates a stage of manufacturing a pellicle assembly 15 according to an embodiment of the present invention, wherein two additional sacrificial layers are provided, namely, three sacrificial layers 31 a , 31 b , 31 c are provided between the substrate 30 and the pellicle membrane 19 .

[0135] As in the previous embodiment, a planar substrate is provided, which may be referred to simply as substrate 30. The substrate 30 may be, for example, a silicon wafer. For example, the substrate 30 may have a shape such as a square, a circle, or a rectangle. The shape of the substrate 30 is not particularly limited, but is most likely a circle, as it is the most commonly available shape. The size of the substrate 30 is not particularly limited.

[0136] The first sacrificial layer 31a is provided, for example, by depositing the first sacrificial layer 31a on the substrate 30. The first sacrificial layer 31a preferably substantially surrounds the substrate 30, but in some embodiments, the first sacrificial layer may only partially surround the substrate 30. The first sacrificial layer 31a includes an oxide, such as silicon oxide or thermal oxide.

[0137] A second sacrificial layer 31b is then provided, for example, by depositing the second sacrificial layer 31b onto the first sacrificial layer 31a. The second sacrificial layer 31b preferably substantially surrounds the first sacrificial layer 31a, but in some embodiments, the second sacrificial layer may only partially surround the first sacrificial layer 31a. The second sacrificial layer 31b comprises a type of silicon, such as polysilicon or doped silicon, preferably in-situ doped polysilicon (ISDP). Advantageously, the second sacrificial layer 31b comprising ISDP can be formed with relatively low roughness and few protrusions.

[0138] For a given etching operation, adjacent sacrificial layers (e.g., first sacrificial layer 31a and second sacrificial layer 31b) formed of different materials (in this example, oxide and silicon) will be etched at different rates. That is, for a particular etching operation, the first sacrificial layer 31a may be etched quickly, while the second sacrificial layer 31b may be etched relatively slowly or not at all. In this way, adjacent sacrificial layers formed of different materials can advantageously enable one layer to form an etch stop layer for the given etching operation.

[0139] The third sacrificial layer 31c is provided, for example, by depositing the third sacrificial layer 31c on the second sacrificial layer 31b. The third sacrificial layer 31c preferably substantially surrounds the second sacrificial layer 31b, but in some embodiments, the third sacrificial layer may only partially surround the second sacrificial layer 31b. The third sacrificial layer 31c comprises a thin layer of oxide, such as silicon oxide or thermal oxide. "Thin" means that the thickness of the third sacrificial layer 31c is substantially less than the thickness of the pellicle diaphragm 19. The third sacrificial layer 31c may be known as a thin oxide layer 31c. Thin layers of oxide are easy to grow to have a layer thickness as is well known in the art. In this way, the thin oxide layer 31c can be formed to have a low surface roughness. This therefore provides a smooth surface on which to deposit the pellicle diaphragm 19.

[0140] The substrate 30 and the first, second, and third sacrificial layers 31 a, 31 b, and 31 c may be referred to as a stack at this stage.

[0141] Prior to depositing the pellicle membrane, the sacrificial layers 31a, 31b, 31c are patterned so as to define areas that will subsequently become boundaries, thereby defining the shape of the final pellicle assembly. That is, a face of the stack is patterned so as to define the shape of the final pellicle assembly. Such a face may be referred to as the "back" of the stack, which is defined as the opposite face to the face that will receive the pellicle membrane 19. Such a process may be known as a patterning process. Such a patterning process may be performed using any suitable resist and etching process. During such a process, the substrate may be transported by equipment that may, for example, clamp the substrate in place and / or invert the substrate. Such transport may carry the risk of damaging or contaminating one or more surfaces of the transported substrate or associated sacrificial layer. By performing such a patterning process prior to depositing the pellicle membrane 19, the risk of damage to the pellicle membrane 19 may be reduced. Although in Figure 4 A specific pattern is depicted in FIG, but it should be understood that any alternative pattern may be produced depending on the desired final shape of the pellicle assembly.

[0142] After the patterning process, the pellicle membrane 19 is disposed on the surface of the third sacrificial layer 31 c. The pellicle membrane 19 may include one or more pellicle layers. Figure 4 The pellicle membrane 19 shown in FIG. 1 comprises a single pellicle layer. The pellicle layer comprises a doped metal silicide, some of the benefits of which are discussed above. The pellicle layer in this or other embodiments may alternatively comprise a metal silicide.

[0143] One or more capping layers may be provided with the pellicle layer. These capping layers may be provided as etch stop layers for future etching processes. Alternatively or additionally, these capping layers may be provided to control the amount of stress on the pellicle layer or pellicle membrane. The capping layer may, for example, comprise an oxide. The capping layer may advantageously be deposited with a stress comparable to that of the third sacrificial layer 31 c. The capping layer may advantageously be configured to have an etching time similar to that of the third sacrificial layer 31 c.

[0144] After depositing the pellicle membrane 19, the substrate 30, the first sacrificial layer 31a, the second sacrificial layer 31b, and the remaining portions of the third sacrificial layer 31c can be selectively etched back to remove a portion of the substrate 30 (and portions of the sacrificial layers 31a, 31b, and 31c), leaving only the outer perimeter to form the frame 17 for supporting the pellicle membrane 19. Thus, the frame 17 includes a portion of the substrate 30, a portion of the first sacrificial layer 31a, a portion of the second sacrificial layer 31b, and a portion of the third sacrificial layer 31c. It can be said that, immediately prior to abutting the pellicle membrane 19, the frame 17 comprises an ordered stack of portions of the substrate 30, the first sacrificial layer 31a, the second sacrificial layer 31b, and the third sacrificial layer 31c. In an example given some of the materials discussed above with reference to such embodiments, immediately prior to abutting the doped metal silicide pellicle membrane, the frame 17 may comprise an ordered stack of silicon, oxide, ISDP, and thin oxide. Alternatively, the frame 17 may comprise an ordered stack of silicon, oxide, silicon and thin oxide just before abutting the doped metal silicide membrane. It will be appreciated that the frame 17 may comprise a corresponding ordered stack of multiple layers depending on the number of sacrificial layers and their composition.

[0145] The choice of sacrificial layer composition can further help reduce the processing time of the pellicle assembly. For example, some processes constitute "bottlenecks" in the manufacturing process, such as the formation of silicon nitride or ISDP. Advantageously, these materials can be omitted from some embodiments of the present invention, thereby reducing the processing time.

[0146] In the above examples, a process for forming a pellicle membrane comprising a single doped metal silicide pellicle layer is described. However, the pellicle membrane may comprise a plurality of pellicle layers. Figure 5 An example embodiment of such a pellicle membrane is illustrated, schematically illustrating a stage in the manufacture of a pellicle assembly 15 having a pellicle membrane 19 comprising three pellicle layers 50a, 50b, 50c.

[0147] As in the previous embodiment, a planar substrate is provided, which may be referred to simply as substrate 30. Substrate 30 may be, for example, a silicon wafer. For example, substrate 30 may have a shape such as square, circular, or rectangular. The shape of substrate 30 is not particularly limited, but is most likely circular, as it is the most commonly available shape. The size of substrate 30 is not particularly limited.

[0148] The first sacrificial layer 31 is provided, for example, by depositing the first sacrificial layer 31 on the substrate 30. The substrate 30 and the first sacrificial layer 31 may be referred to as a stack. The first sacrificial layer 31 preferably substantially surrounds the substrate 30, but in some embodiments, the first sacrificial layer may only partially surround the substrate 30. The first sacrificial layer 31 may comprise an oxide, such as silicon oxide or thermal oxide. The first sacrificial layer 31 advantageously provides a substantially flat surface in preparation for receiving a pellicle layer. Although not depicted, additional sacrificial layers may also be provided prior to depositing the pellicle layer. Similar to Figure 4 In the embodiment illustrated in FIG, the first sacrificial layer 31 is patterned prior to depositing the pellicle layer. This patterning process is performed to define regions that will subsequently become boundaries, thereby defining the shape of the final pellicle assembly. However, it should be noted that, while beneficial in reducing damage to the pellicle layer, this patterning process is not required prior to depositing the pellicle layer.

[0149] A first film layer 50a is disposed on the first sacrificial layer 31. The first film layer 50a includes a metal silicide. A second film layer 50b is disposed on the first film layer 50a. The second film layer 50b includes a doped metal silicide. A third film layer 50c is disposed on the second film layer. The third film layer 50c includes a metal silicide (e.g., the same metal silicide as the first film layer 50a). The first film layer 50a, the second film layer 50b, and the third film layer 50c form the film diaphragm 19. It should be understood that a different number of film layers, such as two or five film layers, can be deposited in a similar manner to form a multi-layer film diaphragm.

[0150] After depositing the first pellicle layer 50a, the second pellicle layer 50b, and the third pellicle layer 50c, the substrate 30 and the first sacrificial layer 31 may be selectively etched back to remove a portion of the substrate and the sacrificial layer and retain only the outer periphery to form the frame for supporting the pellicle diaphragm 19. The frame 17 thus includes a portion of the substrate 30 and a portion of the first sacrificial layer 31, wherein the first sacrificial layer 31 is disposed between the substrate 30 and the pellicle diaphragm 19.

[0151] While the above process describes the fabrication of the pellicle assembly 15, it should be understood that the above process also describes the fabrication of the pellicle membrane 19 deposited on a stack (e.g., on a substrate 30 having one or more sacrificial layers). In some cases, such as if the etching steps are to be performed at a later date or at a different location, it may be beneficial to fabricate the pellicle membrane only on the stack (without defining the boundaries).

[0152] In pellicle manufacturing, the final etching stage (e.g., etching away material to leave only the outer perimeter supporting the pellicle membrane) can be critical to the quality of the resulting pellicle membrane. This etching step is typically performed using a wet etch, for example using common etchants such as buffered oxide etch (BOE), tetramethylammonium hydroxide (TMAH), or hydrofluoric acid (HF).

[0153] The above process describes providing one or more sacrificial layers below the pellicle membrane 19 (i.e., between the pellicle membrane 19 and the substrate 30). However, it may be beneficial to provide a sacrificial layer above the pellicle membrane 19 (i.e., provided to the face of the pellicle membrane 19 distal from the substrate 30), for example, to protect the top surface of the pellicle membrane 19 during additional processing steps.

[0154] Providing sacrificial layers both above and below the pellicle membrane can be beneficial. By providing sacrificial layers above and below the pellicle membrane, and by matching the thickness of the sacrificial layer above the pellicle membrane with the sacrificial layer below the pellicle membrane, overetching can be mitigated. For example, with matching thicknesses between the sacrificial layers above and below the pellicle membrane, the upper sacrificial layer will etch at the same rate as the lower sacrificial layer. This contrasts with mismatched layers, which will etch at different rates, and therefore one layer may be under-etched or over-etched.

[0155] It should be understood that "above" and "below" are relative terms, used relative to the orientation in which they are presented in the figures. These terms should not be construed as limiting, as the pellicle assembly and precursor stage can be oriented in any manner.

[0156] Figure 6 Stages of manufacture of a pellicle assembly 15 according to an embodiment of the invention are schematically illustrated.The pellicle assembly (and precursor stage) is illustrated in cross-section.

[0157] A planar substrate is provided, which may be referred to simply as substrate 30. The substrate 30 may be, for example, a silicon wafer. For example, the substrate 30 may have a shape such as a square, a circle, or a rectangle. The shape of the substrate 30 is not particularly limited, but is most likely a circle, as it is the most commonly available shape. The size of the substrate 30 is not particularly limited.

[0158] The first sacrificial layer 31 is provided, for example, by depositing the first sacrificial layer 31 on the substrate 30. The substrate 30 and the first sacrificial layer 31 may be referred to as a stack. The first sacrificial layer 31 preferably substantially surrounds the substrate 30, but in some embodiments, the first sacrificial layer may only partially surround the substrate 30. The first sacrificial layer 31 may include an oxide, such as silicon oxide or thermal oxide.

[0159] A second sacrificial layer is provided adjacent to the first sacrificial layer 31. This forms an updated stack comprising a planar substrate, the first sacrificial layer 31, and the second sacrificial layer. In this embodiment, the second sacrificial layer comprises amorphous carbon. Thus, the amorphous carbon layer 60 may be provided before providing the pellicle membrane 19, but it will be appreciated that the multiple layers may be provided in a different order.

[0160] The pellicle membrane 19 is provided on the surface of the amorphous carbon layer 60. The pellicle membrane 19 may include one or more pellicle layers. Figure 6 The pellicle membrane 19 shown in FIG. 1 comprises a single pellicle layer forming the pellicle membrane 19 .

[0161] After depositing the pellicle membrane 19, the substrate 30 and the first sacrificial layer 31 are selectively etched back to remove the sacrificial layer and the central portion of the substrate and retain only the outer periphery to form a frame for supporting the pellicle membrane 19 and the amorphous carbon layer 60. Such a frame supporting the pellicle membrane 19 and the amorphous carbon layer 60 may be known as a pre-assembly 62.

[0162] Finally, a portion of the amorphous carbon layer 60 can be removed to retain only the outer periphery, thereby forming a frame 17 for supporting the pellicle membrane 19, thereby forming the pellicle assembly 15. The frame 17 thus includes a portion of the substrate 30, a portion of the first sacrificial layer 31, and a portion of the amorphous carbon layer 60, wherein the amorphous carbon layer 60 is disposed between the first sacrificial layer 31 and the pellicle membrane 19. The amorphous carbon layer 60 can be removed using a number of processes, such as plasma treatment using free radicals, such as hydrogen radicals. In fact, any suitable method can be used to remove the amorphous carbon, and the present invention is not particularly limited by the specific method used.

[0163] Amorphous carbon is highly resistant to several common etchants, such as, but not limited to, buffered oxide etch (BOE), tetramethylammonium hydroxide (TMAH), and hydrofluoric acid (HF). Amorphous carbon can be removed from the pre-assembly 62 without damaging the pellicle membrane 19, for example, using plasma treatment. Plasma treatment is a fast process compared to etching, so applying an amorphous carbon layer followed by subsequent removal using plasma treatment can be beneficial in saving time during the pellicle fabrication process.

[0164] Providing the amorphous carbon layer 60 significantly reduces the probability of overetching, thereby reducing the risk of damaging the pellicle membrane 19 during the etching step. For example, during an etching step used to selectively remove the sacrificial layer and the central portion of the substrate, the amorphous carbon layer 60 can reduce or mitigate the chance that the etchant will remove any portion of the pellicle membrane (i.e., overetch). This results in increased yield in pellicle membrane manufacturing due to the reduced or mitigated chance of damaging or fracturing the pellicle membrane. Additionally, due to the amorphous carbon layer's resistance to etching, a more aggressive and / or faster etching process can be used to remove adjacent layers without compromising the integrity of the pellicle membrane. Consequently, such an etching process can be performed more quickly than without the amorphous carbon layer, thereby beneficially saving time during the pellicle manufacturing process.

[0165] The use of an amorphous carbon layer also provides greater flexibility in selecting other sacrificial layers, such as the properties of the sacrificial layer, such as composition and / or thickness. The flexibility in sacrificial layer selection is provided due to the etch-stopping ability of amorphous carbon; thereby reducing the technical and design constraints on other sacrificial layers previously required to reduce overetching.

[0166] The use of an amorphous layer also provides greater flexibility in selecting the pellicle material due to the high etch resistance of the amorphous layer. The use of an etch stop layer such as an amorphous carbon layer is particularly advantageous when used in combination with a metal silicide or doped metal silicide pellicle layer. Metal silicides and doped metal silicides are particularly sensitive to overetching, so reducing the chance of overetching, for example by using an amorphous carbon layer, is beneficial. Furthermore, etch stop layers such as an amorphous carbon layer are particularly advantageous when used with other materials that are susceptible to wet etching, such as zirconium.

[0167] The amorphous carbon layer 60 may be disposed below the diaphragm 19, as shown in FIG. Figure 6 . An amorphous carbon layer may also be provided above the pellicle membrane, which can protect the top layer of the pellicle membrane 19 from overetching and other potential damage during other processing steps. An amorphous carbon layer may additionally be used at other stages in the pellicle manufacturing process to protect other surfaces and / or reduce overetching of other surfaces.

[0168] Additionally, amorphous carbon provides an effective diffusion barrier. This barrier reduces the risk of material diffusion between adjacent layers. For example, when using a first sacrificial layer comprising an oxide, oxygen may diffuse into the pellicle membrane. Diffusion can be enhanced when the pre-assembly is heated, such as during thermal treatment of the oxide or during the annealing process common in pellicle manufacturing.

[0169] Reducing diffusion into the pellicle layer can be beneficial. For example, optimizing the EUV transmittance of a pellicle membrane can be beneficial, however, diffusing materials can reduce EUV transmittance. In a specific example, diffusion of oxygen from a sacrificial layer comprising an oxide into a pellicle layer comprising a metal silicide can form a metal oxide that has reduced EUV transmittance compared to a metal silicide without the metal oxide. A diffusion barrier (e.g., an amorphous carbon layer) between the sacrificial layer and the pellicle layer can thus optimize the EUV transmittance of the pellicle membrane.

[0170] By providing an amorphous carbon layer between the sacrificial oxide layer and the metal silicide pellicle layer, diffusion of elements between the sacrificial layer and the pellicle layer is reduced. The amorphous carbon diffusion barrier layer reduces interlayer diffusion to a practically negligible level. That is, even during or after heating, virtually no diffusion occurs across the entire diffusion barrier. Furthermore, carbon does not diffuse from the amorphous carbon layer into the pellicle membrane.

[0171] Additionally, the amorphous carbon layer 60 can function as a stress control element. By controlling the properties of the layers adjacent to the pellicle membrane 19, the amount of stress in the pellicle membrane 19 during manufacturing can be reduced. The amorphous carbon layer can function as a stress reducing element, thereby reducing the amount of stress on the pellicle membrane 19 during manufacturing, or it can apply stress, for example, as a prestressing element.

[0172] The thickness of the amorphous carbon layer can be selected to control the amount of diffusion and to optimize other physical properties of the multiple layers, such as stress control. For example, an amorphous carbon layer having a thickness substantially thinner than that of the pellicle membrane can advantageously provide an effective barrier to diffusion, set an etch stop layer, and advantageously pre-stress the pellicle layer.

[0173] In another embodiment, an amorphous carbon layer serves as a pellicle core layer between two pellicle layers. For example, the pellicle membrane may comprise an ordered combination of a metal silicide layer, an amorphous carbon layer, and a second metal silicide layer. Advantageously, the amorphous carbon layer in such an embodiment can be used to tune the amount of tension in the pellicle membrane. Controlling the tension in the pellicle membrane can reduce sagging in the pellicle membrane.

[0174] Figures 7a to 7i Schematically illustrating stages of manufacture of a pellicle assembly 15 according to an embodiment of the present invention. The pellicle assembly (and precursor stages) are illustrated in cross-section. Note that not all intermediate stages are illustrated.

[0175] As in the previous embodiment, Figure 7aAs depicted in FIG, a planar substrate is provided, which may be referred to simply as substrate 30. The substrate 30 may be, for example, a silicon wafer. For example, the substrate 30 may have a shape such as a square, a circle, or a rectangle. The shape of the substrate 30 is not particularly limited, but is most likely a circle, as it is the most commonly available shape. The size of the substrate 30 is not particularly limited.

[0176] The first sacrificial layer 31a is provided, for example, by depositing the first sacrificial layer 31a on the substrate 30. The first sacrificial layer 31a preferably substantially surrounds the substrate 30, but in some embodiments, the first sacrificial layer may only partially surround the substrate 30. The first sacrificial layer 31a preferably comprises an oxide, such as silicon oxide or thermal oxide. The first sacrificial layer 31a may include silicon dioxide or may consist essentially of silicon dioxide.

[0177] A second sacrificial layer 31b is then provided, for example, by depositing the second sacrificial layer 31b onto the first sacrificial layer 31a. The second sacrificial layer 31b preferably substantially surrounds the first sacrificial layer 31a, but in some embodiments, the second sacrificial layer may only partially surround the first sacrificial layer 31a. The second sacrificial layer 31b comprises a type of silicon, such as polysilicon or doped silicon, preferably in-situ doped polysilicon (ISDP). Advantageously, the second sacrificial layer 31b comprising ISDP can be formed with relatively low roughness and few protrusions.

[0178] For a given etching operation, adjacent sacrificial layers (e.g., the first sacrificial layer 31a and the second sacrificial layer 31b) formed of different materials (in this example, oxide and silicon) will be etched at different rates. That is, for a particular etching operation, the first sacrificial layer 31a may be etched quickly, while the second sacrificial layer 31b may be etched relatively slowly or not at all. In this way, adjacent sacrificial layers formed of different materials can advantageously enable one layer to form an etch stop layer for a given etching operation.

[0179] The first sacrificial layer 31a and the second sacrificial layer 31b are patterned to define what will later become the boundary region, thereby defining the shape of the final pellicle assembly. That is, a face of the stack is patterned to define the shape of the final pellicle assembly. This face, which may be referred to as the "back face" of the stack, is defined as the side opposite the face that will receive the pellicle membrane 19. This process is known as patterning. Any suitable resist and etching process can be used to perform this patterning process. During this process, the substrate may be transported by equipment (e.g., which may hold the substrate in place and / or invert it). This transport may carry the risk of damaging or contaminating one or more surfaces of the substrate or associated sacrificial layers. By performing this patterning process before depositing the pellicle membrane 19, the risk of damage to the pellicle membrane 19 is reduced. While a specific pattern is depicted in FIG7 , it should be understood that any alternative pattern may be produced depending on the desired final shape of the pellicle assembly.

[0180] The third sacrificial layer 31c is provided, for example, by depositing it onto the second sacrificial layer 31b after the patterning process. The third sacrificial layer 31c preferably substantially surrounds the second sacrificial layer 31b, but in some embodiments, the third sacrificial layer may only partially surround the second sacrificial layer 31b. The third sacrificial layer 31c comprises a thin layer of oxide, such as silicon oxide or thermal oxide. The oxide layer may be grown chemically and / or thermally as is known in the art. By "thin" is meant that the thickness of the third sacrificial layer 31c is substantially less than the thickness of the pellicle diaphragm 19. The third sacrificial layer 31c may be known as a thin oxide layer 31c. Thin layers of oxide are easy to grow with layer thicknesses as is well known in the art. In this way, the thin oxide layer 31c may be formed with low surface roughness. This thus provides a smooth surface on which to deposit the pellicle diaphragm 19. Figure 7b The stack produced according to the invention is depicted after patterning of the stack and subsequent provision of a third sacrificial layer 31 c.

[0181] The substrate 30 and the first, second, and third sacrificial layers 31 a, 31 b, and 31 c may be referred to as a stack at this stage.

[0182] like Figure 7cAs depicted in FIG, after the patterning process and subsequent provision of the third sacrificial layer 31 c, a pellicle membrane 19 is provided on the surface of the third sacrificial layer 31 c. The pellicle membrane 19 may include one or more pellicle layers. The pellicle membrane 19 shown in FIG7 includes a single pellicle layer. The pellicle layer includes a doped metal silicide, preferably a MoSiN layer, some of the benefits of doped metal silicides being discussed above. The pellicle layer in this or other embodiments may alternatively include a metal silicide. The pellicle membrane 19 may be provided by any means known in the art.

[0183] One or more capping layers may be configured to include a pellicle layer. These capping layers may be configured to serve as etch stop layers for future etching processes. Alternatively or additionally, these capping layers may be configured to control the amount of stress on the pellicle layer or the pellicle membrane. The capping layer may, for example, comprise an oxide. The capping layer may advantageously be deposited with a stress comparable to that of the third sacrificial layer 31 c. The capping layer may advantageously be configured to have an etching time similar to that of the third sacrificial layer 31 c.

[0184] The one or more capping layers may be provided as an oxide layer, which may be derived from TEOS. Optionally, the one or more capping layers may be provided on top of the pellicle membrane 19. The stack may be annealed with or without the one or more capping layers. Annealing the stack preferably controls stress within the stack. The stack may be annealed under conditions known in the art, and the present invention is not particularly limited by the annealing conditions used.

[0185] After annealing of the stack, the one or more capping layers and portions of the third sacrificial layer 31c may be etched, as shown in FIG. Figure 7d As depicted in , it may be a native oxide layer that is etched away without providing one or more capping layers. Figure 7d As illustrated in , this provides a stack having a pellicle membrane 19 disposed on top of a third sacrificial layer 31 c. As such, any sacrificial or capping layer on the surface or top of the pellicle membrane 19 is removed at this stage, and the third sacrificial layer 31 c disposed beneath the pellicle membrane 19 remains.

[0186] The front face of the stack may then be patterned to define the dimensions of the final veneer assembly.The front face of the stack may be patterned by any suitable means as known in the art, and the present invention is not particularly limited by the patterning means used.

[0187] Once the front face of the stack has been patterned, a protective layer 70 may be provided. This protective layer may be a polymeric material as known in the art, such as parylene. Figure 7e The stack is depicted once the front face of the stack has been patterned and after a protective layer 70 has been provided.

[0188] Having provided the protective layer 70, a so-called cavity etching process may be performed. The cavity etching process removes material from the core, the first sacrificial layer 31a, and the second sacrificial layer 31b. Figure 7f An embodiment of the invention is shown in which the material of the third sacrificial layer 31c below the pellicle membrane 19 is not removed during the cavity etching process. Figure 7h An embodiment of the present invention is depicted in which material of the third sacrificial layer 31 c underlying the pellicle membrane 19 is removed during the cavity etching process.

[0189] Therefore, portions of the substrate 30, the first sacrificial layer 31a, the second sacrificial layer 31b, and optionally the third sacrificial layer 31c are selectively etched back to remove a portion of the substrate 30 (and, as needed, portions of the sacrificial layers 31a, 31b, and 31c), while retaining an outer perimeter to form the frame 17 for supporting the pellicle membrane 19. Thus, the frame 17 comprises a portion of the substrate 30, a portion of the first sacrificial layer 31a, a portion of the second sacrificial layer 31b, and a portion of the third sacrificial layer 31c. Depending on whether the third sacrificial layer 31c is etched or not during the cavity etching step, the third sacrificial layer 31c may or may not span the entire pellicle membrane. In other words, immediately prior to abutting the pellicle membrane 19, the frame 17 comprises an ordered stack of portions of the substrate 30, the first sacrificial layer 31a, the second sacrificial layer 31b, and the third sacrificial layer 31c. In an example given some of the materials discussed above with reference to such an embodiment, the frame 17 may comprise an ordered stack of silicon, oxide, ISDP, and thin oxide just before being abutted against a doped metal silicide membrane (preferably MoSiN). Alternatively, the frame 17 may comprise an ordered stack of silicon, oxide, silicon, and thin oxide just before being abutted against a doped metal silicide membrane. It will be understood that the frame 17 may comprise a corresponding ordered stack of multiple layers, depending on the number of sacrificial layers and their composition. Figure 7g Depicting an embodiment of a diaphragm assembly in which the third sacrificial layer 31c spans the diaphragm membrane 19, however Figure 7iAn embodiment is depicted in which the third sacrificial layer 31 c does not span the diaphragm 19 .

[0190] The choice of sacrificial layer composition can also help reduce the processing time of the pellicle assembly. For example, some processes constitute "bottlenecks" in the manufacturing process, such as the formation of silicon nitride or ISDP. Advantageously, these materials can be omitted from some embodiments of the present invention, thereby reducing processing time.

[0191] Figure 8 FIG7 is an exemplary flow chart of the method depicted in FIG7 . In a first stage 100, a first sacrificial layer and a second sacrificial layer are disposed in a core. The core is preferably c-Si, although other allotropes of silicon and other materials may also be used. The first sacrificial layer is preferably silicon oxide, preferably silicon dioxide. The second sacrificial layer is preferably silicon-based and may be ISDP. The core, first sacrificial layer, and second sacrificial layer may be referred to as a stack. In stage 200, the back of the stack may be patterned. This may be accomplished by any suitable means and serves to define the shape of the final pellicle assembly by defining the dimensions of the frame that supports the pellicle membrane in the final assembly. In stage 300, another oxide layer, known as the third sacrificial layer, is disposed on the patterned stack. The oxide layer may be formed by any known means, such as chemical or thermal oxidation. In stage 400, the material that will form the pellicle membrane is deposited or otherwise disposed on the surface of the patterned stack. Stage 500 is optional and involves applying another sacrificial / capping layer to the patterned stack. This may be referred to as a top oxide. In stage 600, the stack is annealed. It has been found that the annealing step may be performed without the additional protection provided by stage 500. In stage 700, the top oxide (if present) and / or any native oxide layer may be removed. After removing the top oxide or native oxide layer (if present), in stage 800, the front side of the stack is patterned to define the shape and dimensions of the pellicle membrane. Following the patterning in stage 800, a protective layer (preferably a polymeric protective material such as perylene) is applied to protect the pellicle membrane layer. A cavity etching step is then performed in stage 900, which etches away the core from the back side and forms the framework of the pellicle assembly. Optionally, the sacrificial layer located below the pellicle membrane is removed or left in place in stage 1000 or 1100, as appropriate. The final pellicle assembly can then be released from the protective layer. Since the sacrificial layers immediately above and immediately below the pellicle membrane are removed in different stages, a wet HF etching step to remove these oxide layers may not be necessary. Thus, as shown in FIG7 and FIG10 , the sacrificial layer is removed from the protective layer. Figure 8The process described in avoids a wet HF etching step that may lead to damage and possible mechanical loss or malfunction / failure of the pellicle membrane during fabrication, as well as reducing non-uniformities caused by over-etching portions of the pellicle membrane.

[0192] It should be understood that features of the above-described embodiments may be combined. For example, although described in different embodiments, the use of an amorphous carbon layer is applicable to use with a pellicle membrane comprising three pellicle layers, a pellicle assembly comprising three sacrificial layers, or any other features discussed above. The pellicle membrane may include one or more metal silicide layers and / or one or more doped metal silicide layers and / or one or more amorphous carbon layers.

[0193] Although specific reference may be made herein to the use of lithographic apparatus in IC fabrication, it should be understood that the lithographic apparatus described herein may have other applications. Possible other applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), diaphragm magnetic heads, and the like.

[0194] While specific reference may be made herein to embodiments of the present invention in the context of lithographic apparatus, embodiments of the present invention may be used in other devices. Embodiments of the present invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus that measures or processes an object, such as a wafer (or other substrate) or a mask (or other patterning device). These apparatuses may generally be referred to as lithographic tools. Such lithographic tools may utilize either vacuum conditions or ambient (non-vacuum) conditions.

[0195] Where context permits, embodiments of the present invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the present invention may also be implemented as instructions stored on a machine-readable medium, which can be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing device). For example, a machine-readable medium may include read-only memory (ROM); random-access memory (RAM); magnetic storage media; optical storage media; flash memory devices; electrical, optical, acoustic, or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, etc.); and the like. Furthermore, firmware, software, routines, and instructions may be described herein as performing specific actions. However, it should be understood that such descriptions are for convenience only, and that such actions are actually caused by a computing device, processor, controller, or other device executing the firmware, software, routines, instructions, etc., and in doing so, may cause actuators or other devices to interact with the physical world.

[0196] Although specific embodiments of the present invention have been described above, it will be appreciated that the present invention may be practiced in other ways than those described. The foregoing description is intended to be illustrative, not restrictive. Thus, it will be apparent to those skilled in the art that modifications may be made to the present invention as described without departing from the scope of the claims set forth below.

Claims

1. A method for manufacturing a diaphragm membrane, the method comprising: providing a first sacrificial layer on a planar substrate to form a stack; and providing at least a portion of the stack with at least one metal silicide or doped metal silicide pellicle core layer forming at least a portion of the pellicle diaphragm; and providing at least one additional sacrificial layer on the first sacrificial layer before providing the at least one pellicle core layer, and arranging the at least one additional sacrificial layer to have a controlled stress in the at least one additional sacrificial layer.

2. The method of claim 1, wherein the pellicle core layer is deposited using physical vapor deposition.

3. The method of claim 1 or 2, wherein the metal comprises molybdenum. The method of claim 1 , wherein the dopant comprises nitrogen, boron and / or carbon. The method of claim 1 , wherein the first sacrificial layer comprises oxide. The method of claim 1 , wherein the at least one additional sacrificial layer comprises oxide or silicon. The method of claim 6 , wherein the composition of adjacent sacrificial layers alternates between oxide and silicon. The method of claim 1 , wherein the first sacrificial layer comprises amorphous carbon.

9. The method of claim 1, wherein the at least one additional sacrificial layer comprises amorphous carbon.

10. The method of claim 1, wherein three skin core layers are disposed on the laminate.

11. The method of claim 10, wherein the three pellicle core layers are deposited in the following order: a first metal silicide layer, a doped metal silicide layer, and a second metal silicide layer.

12. The method of claim 1, further comprising one or more etching steps to remove one or more sacrificial layers and at least a portion of the substrate.

13. The method of claim 12, wherein at least one etching step is performed after depositing one or more sacrificial layers and before depositing the pellicle core layer.

14. The method of claim 1, wherein one or more etching steps define a boundary that maintains the pellicle membrane.

15. The method of claim 1, wherein the planar substrate is a silicon-on-insulator (SOI) wafer.

16. The method of claim 1, wherein the planar substrate is annealed to provide a thermal oxide layer prior to providing a tetraethylorthosilicate layer. The method of claim 1 , wherein the final etching step is a wet etch.

18. The method of claim 17, wherein the final etching step is a HF wet etch of the tetraethylorthosilicate layer.

19. The method of claim 17 or 18, wherein at least one of the first sacrificial layer and the at least one additional sacrificial layer comprises amorphous carbon, and the method further comprises a plasma treatment step after the final etching step, wherein the plasma treatment step removes at least a portion of the first sacrificial layer or the additional sacrificial layer of amorphous carbon.

20. The method of claim 1, wherein the method comprises patterning a back side of the stack after providing the first and second sacrificial layers on the planar substrate.

21. The method according to claim 20, further comprising the following sequential steps: i) providing a third sacrificial layer in the form of an oxide to form a bottom oxide; ii) depositing the skin core layer on a face of the laminate; iii) optionally depositing a capping layer in the form of another oxide layer on the top surface of the pellicle core layer to form a top oxide layer; iv) annealing the stack; v) optionally, removing the top oxide layer and / or any native oxide layer; vi) patterning the front side of the stack; vii) providing a protective layer to protect the front side of the stack; as well as viii) performing a cavity etch from the back side of the stack to remove the planar substrate, the first sacrificial layer, a portion of the second sacrificial layer, and optionally a portion of the third sacrificial layer to define a pellicle assembly. 22 . The method according to claim 21 , wherein the cap layer of step iii) is formed of TEOS.

23. A method according to claim 21 or 22, wherein the protective layer is formed from a polymeric material. The method according to claim 23 , wherein the protective layer is formed of parylene.

25. The method of claim 21, further comprising removing the protective layer to release the diaphragm membrane assembly.

26. The method of claim 21, wherein the third sacrificial layer is a chemical oxide or a thermal oxide.

27. The method of claim 21, wherein the method does not include a wet HF etch step.

28. A diaphragm assembly comprising a substrate, a first sacrificial layer, and at least one metal silicide or doped metal silicide diaphragm core layer forming at least a portion of a diaphragm core, and at least one additional sacrificial layer disposed between the first sacrificial layer and the at least one diaphragm core layer. Wherein the at least one additional sacrificial layer is arranged to have a controlled stress in the at least one additional sacrificial layer.

29. The diaphragm assembly of claim 28, wherein the diaphragm assembly comprises at least three sacrificial layers, wherein the first sacrificial layer and the third sacrificial layer comprise the same material.

30. The diaphragm diaphragm assembly of claim 29, wherein the first and third sacrificial layers comprise thermal oxide as the same material.

31. The skin membrane assembly of claim 28, 29 or 30, wherein the at least one skin core layer comprises a first skin layer, a second skin layer and a third skin layer.

32. The diaphragm assembly of claim 31, wherein the first diaphragm layer and the third diaphragm layer comprise metal silicide, and the second diaphragm layer comprises a doped metal silicide.

33. The diaphragm diaphragm assembly of claim 32, wherein the metal comprises molybdenum.

34. The diaphragm assembly of claim 28, wherein the substrate forms at least a portion of a boundary retaining the diaphragm membrane.

35. The pellicle membrane assembly of claim 34, wherein the boundary comprises an ordered stack of: a portion of a planar substrate, and at least one sacrificial layer, wherein the at least one sacrificial layer is adjacent to the pellicle membrane.

36. The diaphragm diaphragm assembly of claim 35, wherein the at least one sacrificial layer comprises oxide or silicon.

37. The diaphragm diaphragm assembly of claim 36, wherein the composition of adjacent sacrificial layers alternates between oxide and silicon.

38. The diaphragm assembly of claim 28, wherein the sacrificial layer adjacent to the diaphragm diaphragm comprises an oxide and is thinner than the diaphragm diaphragm.

39. The diaphragm diaphragm assembly of claim 28, wherein the first sacrificial layer or at least one additional sacrificial layer comprises amorphous carbon.

40. The diaphragm assembly of claim 39, wherein the sacrificial layer adjacent to the diaphragm diaphragm comprises amorphous carbon.

41. The diaphragm membrane assembly of claim 40, wherein the sacrificial layer adjacent to the diaphragm membrane is thinner than the diaphragm membrane.

42. The diaphragm assembly of claim 31, wherein the first diaphragm layer and the third diaphragm layer comprise metal silicide, and the second diaphragm layer comprises amorphous carbon.

43. A method of manufacturing a pellicle membrane, the method comprising: providing at least one amorphous carbon layer adjacent to a pellicle core layer forming at least a portion of the pellicle membrane, The method further comprises: before providing the at least one amorphous carbon layer, providing a first sacrificial layer on the planar substrate to form a stack; and wherein the at least one amorphous carbon layer comprises at least one additional sacrificial layer disposed between the first sacrificial layer and the pellicle core layer, and the at least one amorphous carbon layer disposed adjacent to the pellicle core layer comprises: providing the at least one additional sacrificial layer on the first sacrificial layer and arranging the at least one additional sacrificial layer to have a controlled stress; and The skin core layer is provided to at least a portion of the stack.

44. The method of claim 43, wherein the pellicle core layer comprises a metal silicide or a doped metal silicide.

45. A pellicle diaphragm assembly comprising a substrate, at least one amorphous carbon layer, and a pellicle diaphragm, at least a portion of the pellicle diaphragm comprising a pellicle core layer, The diaphragm assembly further comprises a first sacrificial layer disposed on the substrate. wherein the at least one amorphous carbon layer comprises at least one additional sacrificial layer disposed between the first sacrificial layer and the pellicle core layer, and Wherein the at least one additional sacrificial layer is arranged to have a controlled stress in the at least one additional sacrificial layer.

46. ​​The diaphragm membrane assembly of claim 45, wherein the diaphragm membrane comprises a metal silicide, a doped metal silicide, or zirconium.

47. The diaphragm membrane assembly of claim 45 or 46, wherein the amorphous carbon layer is thinner than the diaphragm membrane.

48. The diaphragm assembly of claim 45, wherein the substrate forms at least a portion of a boundary retaining the diaphragm membrane.

49. The pellicle membrane assembly of claim 48, wherein the boundary comprises an ordered stack of: a portion of a planar substrate and a portion of an amorphous carbon layer, wherein the at least one amorphous carbon layer is adjacent to the pellicle membrane.

50. A lithographic apparatus comprising a pellicle membrane assembly according to any one of claims 28 to 42 or 45 to 49 or a pellicle membrane manufactured by the method of any one of claims 1 to 27, 43 or 44.

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