Pellicle membrane

Abstract

To provide a method of manufacturing a pellicle which provides pellicles with uniform physical properties, which minimizes damage to or defects in the pellicles, and which allows high volume manufacturing of the pellicles.SOLUTION: A method of manufacturing a pellicle membrane is described which includes: providing a first sacrificial layer onto a planar substrate to form a stack; and providing, to at least a portion of the stack, at least one metal silicide or doped metal silicide pellicle core layer which forms at least part of the pellicle membrane. Also described are: a pellicle membrane assembly having a substrate, a first sacrificial layer, and at least one metal silicide or doped metal silicide pellicle layer which forms at least part of a pellicle core; and a lithography apparatus including such a pellicle.SELECTED DRAWING: Figure 3

Description

TECHNICAL FIELD

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims priority to European / U.S. Application No. ... filed on ..., the entire contents of which are incorporated herein by reference in their entirety.

BACKGROUND ART

[0002]

[0002] The present invention relates to a method of manufacturing a pellicle membrane. The present invention is used in connection with, but not limited to, extreme ultraviolet (EUV) lithographic apparatuses and EUV lithographic tools in particular. The present invention also relates to a pellicle membrane assembly and a lithographic apparatus comprising such an assembly.

[0003]

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

[0004]

[0004] To project a pattern onto a substrate, a lithographic apparatus may use electromagnetic radiation. The wavelength of this radiation determines the minimum size of features that can be formed on the substrate. A lithographic apparatus that uses extreme ultraviolet (EUV) radiation with a wavelength in the range of 4 to 20 nm, for example 6.7 nm or 13.5 nm, can be used to form smaller features on a substrate than, for example, a lithographic apparatus that uses radiation with a wavelength of 193 nm.

[0005]

[0005] In a lithography apparatus, a pattern can be applied to the radiation beam using a patterning device (e.g., a mask or reticle). The radiation is delivered through or reflected from the patterning device to form an image on the substrate. Contamination on the surface of the patterning device may cause manufacturing defects in the substrate. To protect the patterning device from airborne particles and other forms of contamination, a film assembly, also called a pellicle, may be provided.

[0006]

[0006] Pellicles may also be provided to protect optical components other than patterning devices. Pellicles may also be used to provide passages for lithographic radiation between sealed areas of a lithography apparatus. Pellicles may be used as filters, such as spectral purity filters, or as part of a dynamic gas lock in a lithography apparatus.

[0007]

[0007] The use of pellicles in lithography is well known and established. In a lithography apparatus, the pellicle is a film (also called a pellicle film) located away from the patterning device and out of the focal plane of the lithography apparatus during use. Because the pellicle is out of the focal plane of the lithography apparatus, contaminating particles adhering to the pellicle are out of the focal point of the lithography apparatus. As a result, images of the contaminating particles are not projected onto the substrate. If there were no pellicle, contaminating particles adhering to the patterning device would be projected onto the substrate, introducing defects into the projected pattern.

[0008]

[0008] The mask assembly may include a pellicle that protects the patterning device (e.g., the mask) from particle contamination. The pellicle may be supported by a pellicle frame to form a pellicle assembly or membrane assembly. The pellicle may be attached to the frame, for example, by bonding the edge region of the pellicle to the frame or by other means. The frame may be attached to the patterning device permanently or peelably. The frame may also be known as a edging.

[0009]

[0009] Manufacturing pellicles using mass production technology is beneficial, for example, because pellicles must be frequently cleaned or replaced when contaminated or damaged.

[0010]

[0010] The presence of a pellicle in the optical path of the EUV radiation beam necessitates that the pellicle have high EUV transmittance. High EUV transmittance allows most of the incident radiation to pass through the pellicle. Since the transmittance depends at least partially on the thickness of the pellicle, it is desirable to provide the thinnest possible pellicle while ensuring that it maintains sufficient strength to withstand the harsh environment inside the lithography apparatus.

[0011]

[0011] The pellicle may be heated by being in the optical path of the EUV radiation beam. High temperatures can damage or break the pellicle. It is desirable to reduce the operating temperature of the pellicle or to provide a pellicle that can withstand higher temperatures.

[0012]

[0012] Manufacturing a pellicle assembly without the membrane assembly being deformed or damaged during the process is difficult, for example, due to the thinness of the membrane. Damage to the membrane assembly or defects in the membrane assembly are undesirable, as they can lead to reduced performance, shortened lifespan, or even failure.

[0013]

[0013] Etching is a common manufacturing process used to remove a portion of a material. In multilayer materials, selective etching can remove a portion of a layer so that an underlying layer is exposed. Over-etching can occur when more material than desired is removed. Over-etching in pellicle manufacturing can cause damage to the pellicle film. Over-etching can cause a loss of strength in the pellicle film. This may cause the pellicle film to break during manufacturing, transport, or subsequent use. Therefore, it is desirable to reduce the possibility of over-etching. To achieve a pellicle assembly with reliable and uniform properties, it is also desirable to develop a manufacturing process that assists in the deposition of layers and / or removes a portion of the material in a controlled manner.

[0014]

[0014] It is desirable to provide a method for manufacturing a pellicle that provides a pellicle with uniform physical properties, minimizes damage to or defects in the pellicle, and enables mass production of the pellicle. The present invention has been devised to address at least some of the problems identified above. [Overview of the project]

[0015]

[0015] According to a first aspect, a method for manufacturing a pellicle film is provided, comprising providing a first sacrificial layer on a planar substrate to form a stack, and providing at least a portion of the stack with a pellicle core layer of at least one metal silicide or doped metal silicide that forms at least a portion of the pellicle film.

[0016]

[0016] Metal silicides and doped metal silicides may be beneficial for use in pellicle films due to their high EUV transmittance. Their high emissivity can also beneficially lower the operating temperature of the pellicle film, thereby reducing the risk of damage to the pellicle film during use. Furthermore, when metal silicides or doped metal silicides are used as the pellicle core layer, their emissivity may alleviate or eliminate the need for an additional radiant capping layer on the front and / or back surfaces of the pellicle film. Advantageously, eliminating the requirement for a radiant capping layer can reduce manufacturing time and / or reduce damage to the pellicle film during manufacturing.

[0017]

[0017] For example, methods for manufacturing other types of pellicle films using a silicon core would be suboptimal for manufacturing pellicle films having at least one metal silicide or doped metal silicide pellicle core layer. Methods according to this aspect of the present invention and related embodiments may beneficially provide a method for manufacturing pellicle films having 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 before depositing the metal silicide or doped metal silicide pellicle core layer allows for beneficial control of the properties of the surface receiving the pellicle core layer, such as the surface topology. Beneficially, the layer may have at least one of a small number of pinholes, low roughness, a small number of contaminant particles, a uniform layer thickness, and / or trace amounts of air / vacuum between the surface and the pellicle core layer.

[0018]

[0018] 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 simply be referred to as the substrate.

[0019]

[0019] The pellicle core layer can be deposited using physical vapor deposition (PVD). Beneficially, PVD can reduce the amount of raw materials required for deposition. Beneficially, PVD can provide better 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 to silicon and (optionally) dopant in the pellicle core layer, and / or the repeatability of these properties when processing multiple films.

[0020]

[0020] The metal may contain molybdenum. Metal M can be one of a variety of metals. For example, the metal can be selected from the group comprising Ce, Pr, Sc, Eu, Nd, Ti, Cr, Zr, Nb, Mo, Ru, Rh, La, Y, and Be. Of this group, preferred metals are zirconium, molybdenum, and beryllium. Molybdenum is the most preferred.

[0021]

[0021] The dopant may contain nitrogen. The dopant can be any suitable dopant. For example, the dopant may be oxygen, carbon, boron, or nitrogen. Of these, the preferred dopant is nitrogen.

[0022]

[0022] 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 such that the surface of the first sacrificial layer that receives at least one pellicle core layer has high smoothness and / or high cleanliness. That is, the first sacrificial layer may have a uniform thickness and / or low roughness and / or low contaminant particle density. By providing a highly smooth surface, the pellicle core layer of metal silicide or doped metal silicide can be deposited with high quality. High quality may mean, for example, a small number of pinholes, a uniform layer thickness, and / or trace amounts of air / vacuum between the surface and the pellicle core layer.

[0023]

[0023] The method may further comprise providing at least one additional sacrificial layer on top of the first sacrificial layer before providing at least one pellicle core layer. There may be any number of additional sacrificial layers, for example, one or four. Providing additional sacrificial layers allows for beneficial control of the surface topology of the surface that will receive at least one pellicle core layer. Beneficially, the layers may be of high quality, e.g., have a small number of pinholes, uniform layer thickness, and / or trace amounts of air / vacuum between the surface and the pellicle core layer. The additional sacrificial layers may be referred to as sacrificial layers. That is, the “sacrificial layer” may comprise the first sacrificial layer and optionally one or more additional sacrificial layers. If the sacrificial layers comprise different materials, each material may have a different etching rate in a given etching solution compared to another material. This may enable highly controlled etching of the stack, because certain sacrificial layers may be resistant to the etching solution, thus preventing over-etching.

[0024]

[0024] At least one additional sacrificial layer may comprise an oxide or silicon. Preferably, the composition of adjacent sacrificial layers may alternate between oxide and silicon. The oxide may be silicon oxide.

[0025]

[0025] As mentioned, oxides and silicon may have different etching rates. Having different sacrificial layers comprising oxide or silicon can be beneficial in providing different sacrificial layers with different etching rates. Having adjacent layers with different etching rates can be beneficial in allowing one layer to act as an etching stopper for an adjacent layer.

[0026]

[0026] Silicon may be silicon or polysilicon, and may be doped or undoped. For example, the silicon may be in-situ doped polysilicon. The dopant may be phosphorus, or another dopant. The oxide may be silicon dioxide, and may be formed from tetraethyl orthosilicate (TEOS), thermal oxide, or any material having behavior and / or chemical / physical properties similar to silicon dioxide.

[0027]

[0027] The at least one additional sacrificial layer may be arranged to have controlled stress within the layer. For example, the at least one additional sacrificial layer may have tensile stress. Providing stress in the sacrificial layer may beneficially pre-stress the at least one pellicle core layer. Pre-stressing the pellicle core layer can beneficially reduce sagging of the pellicle membrane when the pellicle membrane is removed from the substrate to be free-standing and during use.

[0028]

[0028] The first sacrificial layer may comprise amorphous carbon. The at least one additional sacrificial layer may comprise amorphous carbon. Amorphous carbon can beneficially reduce over-etching during pellicle fabrication, and / or provide a diffusion barrier between layers of the pellicle membrane assembly, and / or pre-stress the pellicle membrane.

[0029]

[0029] 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 can beneficially have high emissivity and / or high EUV transmittance. A pellicle membrane having three core layers can be manufactured with low defectivity. A pellicle membrane comprising a stack in the order of the first metal silicide layer, the doped metal silicide layer, and the second metal silicide layer can beneficially be manufactured relatively easily and / or at a relatively high speed using PVD.

[0030]

[0030] The method may further comprise one or more etching steps for removing at least a portion of the substrate and one or more sacrificial layers. Removing the substrate and at least a portion of the one or more sacrificial layers may define, for example, a border or frame around the periphery of the pellicle film. Removing the substrate and at least a portion of the one or more sacrificial layers may substantially detach the pellicle film from the substrate and one or more sacrificial layers. The detached pellicle film may form part of a pellicle assembly comprising the pellicle film and a border supporting the pellicle film. A suitable etching solution can be selected depending on the specific material to be etched.

[0031]

[0031] The method may comprise performing at least one etching step after the deposition of the sacrificial layer and before the deposition of the pellicle core layer. This etching step may define an area to be etched in a subsequent etching step. The defined area may define the overall shape of the completed pellicle assembly. The defined area may define, for example, a border or frame around the periphery of the pellicle film. The etching step may remove at least a portion of at least one of one or more sacrificial layers. The etching step may optionally remove at least a portion of the substrate. Beneficially, by performing this etching step and defining an area to be etched in a subsequent etching step before the deposition of the pellicle core layer, damage to the pellicle core layer can be avoided.

[0032]

[0032] The planar substrate may be an SOI (silicon-on-insulator) wafer. The planar substrate may be a silicon wafer. These types of substrates are well characterized and readily available.

[0033]

[0033] The planar substrate can be annealed to provide a thermal oxide layer before providing the tetraethyl orthosilicate layer.

[0034]

[0034] The final etching step may be wet etching. Preferably, HF wet etching etches the tetraethyl orthosilicate layer.

[0035]

[0035] The method may further comprise a plasma treatment step following the final etching step. The plasma treatment step may remove at least a portion of the first sacrificial layer of amorphous carbon or an additional sacrificial layer. The plasma treatment may comprise treatment with radicals, such as hydrogen radicals. Beneficially, the plasma treatment may remove some portion of the sacrificial layer (e.g., a portion of the sacrificial layer made from an etching-resistant but plasma-sensitive material, such as amorphous carbon) without damaging or removing the pellicle film.

[0036]

[0036] According to one embodiment of the present invention, the method includes patterning the back side of the stack, following the provision of first and second sacrificial layers on a planar substrate. The back side is the side or face of the stack opposite to the side or face of the stack to which the pellicle core layer is provided. Thus, the back side of the stack is patterned before the provision of the third sacrificial layer. As will be described in more detail below, this specifies a manufacturing procedure that allows the sacrificial layer directly adjacent to the pellicle core layer to be removed at different stages. This eliminates the need for wet HF etching at the end of the procedure, which is advantageous because wet HF etching can cause damage to the pellicle core layer.

[0037]

[0037] The method may sequentially include: i) providing a third sacrificial layer in the form of an oxide to form a bottom oxide; ii) depositing a pellicle core layer on the surface of the stack; iii) optionally depositing a capping layer on the upper surface of the pellicle core layer in the form of a further oxide layer to form a top oxide layer; iv) annealing the stack; v) optionally removing the top oxide layer (if any) and / or the native oxide layer; vi) patterning the front of the stack; vii) providing a protective layer to protect the front of the stack; and viiii) performing cavity etching from the back of the stack to remove a planar substrate, the first sacrificial layer, a portion of the second sacrificial layer, and optionally a portion of the third sacrificial layer to define the pellicle assembly.

[0038]

[0038] In existing procedures for manufacturing pellicle film assemblies, silicon oxide layers are provided directly above and below the pellicle core layer at the stage in which the final self-supporting film is separated from the support wafer. A final wet HF etching step is required to etch away these sacrificial protective layers. This requires the insertion of a very thin film, about 140 nm thick, into a highly reactive etching bath. This step often results in a loss of mechanical yield. Furthermore, if the core material of the pellicle film is etched with HF such as MoSiN, as used in embodiments of the present invention, local differences in thickness may occur due to HF etching, which results in non-uniformity of EUV transmittance. In addition, the compressibility of silicon oxide can lead to wrinkles forming in the pellicle stack or exposure to vibrations caused by natural vibrations such as sound immediately before HF etching. This wrinkled state makes the pellicle very fragile and difficult to handle or process. A flowchart according to one embodiment of the present invention addresses or overcomes these difficulties.

[0039]

[0039] A third sacrificial layer may be provided in the form of an oxide to form a bottom oxide. The term “bottom oxide” is used to refer to the relative position of such oxide to the pellicle core layer in a later stage of the process. This distinguishes the oxide from the top oxide. This sacrificial layer may be provided by any suitable means, such as chemical or thermal, as is known in the art. When the third sacrificial layer is formed using chemical means known in the art, such as DIO3, DIO3+SC1+SC2, or DIO3+SC1, its thickness may be about 0.5 nm to about 3 nm. This layer functions as an etching barrier against silicon (ISDP) etching. Previously, the bottom oxide layer had to be removed to increase EUV transmittance. However, it has been found that, due to the extremely thin nature of chemical oxides, the effect of the bottom oxide layer on EUV transmittance is limited, and therefore etching off the bottom oxide is no longer necessary. This allows for a process flowchart without an HF etching step. Alternatively, a thermal oxide layer may be provided. This may also be called a dry oxide. This type of oxide can be thermally grown at high temperatures, e.g., above 900°C, in an oxygen-rich environment. The thickness of this thermal oxide layer can be approximately 5 nm to 15 nm, typically around 10 nm. In the flowchart of the present invention, since there is no longer a top sacrificial layer, the bottom oxide may be removed before the self-supporting film is separated from the wafer as part of cavity etching. During cavity etching, the film is not yet self-supporting, as it is covered by a protective layer, such as a polymer such as perylene, which may be several microns thick. The thermal oxide may be removed by an HF bath or a BOE bath. The advantage of using a dry oxide is that the underlying sacrificial ISDP layer is exposed to a high-temperature process before the pellicle core layer is deposited on top. This high temperature helps to stabilize the ISDP layer, thereby stabilizing the substrate on which the pellicle core layer is deposited. In embodiments where no top oxide is provided, this allows the pellicle to remain flat throughout the process flowchart, thereby enabling safer handling.

[0040]

[0040] In embodiments of the present invention, step iii) is optional. The pellicle film has been found to be robust enough to handle subsequent process steps without affecting the final performance. Thus, the top oxide is not strictly necessary, and by eliminating this layer, it is possible to provide a process flowchart that does not include HF etching. As a result, step v) is also optional.

[0041]

[0041] The capping layer in step iii) may be formed from TEOS, but any other suitable process known in the art may be used.

[0042]

[0042] The protective layer may be formed from a polymer material such as perylene. Alternatively, any suitable protective material known to be used for protecting materials during the etching process may be used.

[0043]

[0043] The protective layer can be removed to delaminate the pellicle film assembly. The protective layer may be removed by oxygen plasma. Thus, unless final HF etching is performed, a thin silicon dioxide layer about 1 to 2 nm thick will remain on top of the pellicle core film.

[0044]

[0044] As described above, the third sacrificial layer may be a chemical oxide or a thermal oxide.

[0045]

[0045] The method does not have to include a wet HF etching step. The flowchart design makes it possible to avoid the need for dangerous HF etching during the process.

[0046]

[0046] This method has been shown to reduce EUV transmittance non-uniformity by approximately three times by eliminating the final HF etching step. Since minimizing EUV transmittance non-uniformity is desirable, this method provides an improved minimal pellicle product that would not be possible by using other flowcharts. Thus, the final product is distinguished from seemingly similar pellicle assemblies by having an EUV transmittance non-uniformity of less than 0.15%.

[0047]

[0047] According to a second aspect of the present invention, a pellicle film assembly is provided, comprising a substrate, a first sacrificial layer, and a pellicle layer of at least one metal silicide or doped metal silicide that forms at least a portion of the pellicle core.

[0048]

[0048] Metal silicides and doped metal silicides may be beneficial for use in pellicle films due to their high EUV transmittance. Their high emissivity can also beneficially lower the operating temperature of the pellicle film, thereby reducing the risk of damage to the pellicle film during use. Furthermore, when metal silicides or doped metal silicides are used as the pellicle core layer, their emissivity may alleviate or eliminate the need for an additional radiating capping layer on the front and / or back surfaces of the pellicle film. Advantageously, eliminating the requirement for a radiating capping layer can reduce manufacturing time and / or reduce damage to the pellicle film during manufacturing. Thus, the assembly according to the present invention may support an improved pellicle film. For example, its pellicle film may be of higher quality and / or can be produced with a higher yield compared to other pellicle films. Its pellicle film may have higher transmittance and higher emissivity than other pellicle films.

[0049]

[0049] The assembly may further comprise at least one additional sacrificial layer disposed between the first sacrificial layer and 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 beneficially controlled to increase the surface topology of the surface receiving at least one pellicle core layer, for example, to increase smoothness. 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. Also, various sacrificial layers having improved interlayer adhesion properties may be selected. For example, there may be relaxed interlayer lattice mismatches, which reduce the possibility of delamination.

[0050]

[0050] The assembly may comprise at least three sacrificial layers. The first and second sacrificial layers may comprise the same material, preferably a thermal oxide, preferably silicon oxide.

[0051]

[0051] 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 and third pellicle core layers may comprise a metal silicide and the second pellicle core layer may comprise a doped metal silicide. The metal may be molybdenum. A pellicle film having three core layers may beneficially have high emissivity and / or high EUV transmittance. A pellicle film having three core layers may be manufactured with low defect properties. A pellicle film having a stack in the order of a first metal silicide layer, a doped metal silicide layer, and a second metal silicide layer may beneficially be manufactured relatively easily and / or relatively quickly using PVD.

[0052]

[0052] The substrate may form at least a portion of the edging that holds or supports the pellicle film.

[0053]

[0053] The border may comprise an ordered sequence of a portion of the planar substrate and at least one sacrificial layer, the at least one sacrificial layer being adjacent to the pellicle film / core. A pellicle assembly can be manufactured by depositing a pellicle core layer of at least one metal silicide or doped metal silicide that forms part of the pellicle film, and by selectively etching one or more portions of the substrate to define the border, where the assembly comprises a substrate and one or more sacrificial layers. Thus, the border may be similar in composition to the assembly in that if the stack is an ordered sequence of a substrate and one or more sacrificial layers, it will comprise a portion of the ordered sequence of a substrate and one or more sacrificial layers corresponding to that.

[0054]

[0054] At least one sacrificial layer may comprise an oxide or silicon. Preferably, the composition of adjacent sacrificial layers may alternate between oxide and silicon.

[0055]

[0055] Oxides and silicon may have different etching rates. Having different sacrificial layers comprising oxide or silicon can be beneficial in providing different sacrificial layers with different etching rates. Having adjacent layers with different etching rates can be beneficial in allowing one layer to act as an etching stopper for an adjacent layer.

[0056]

[0056] Silicon may be silicon or polysilicon, and may be doped or undoped, for example, silicon may be in-situ doped polysilicon. The dopant may be phosphorus or another dopant. The oxide may be silicon dioxide, tetraethyl orthosilicate (TEOS), thermal oxide, or any material having similar behavior to silicon dioxide.

[0057]

[0057] At least one additional sacrificial layer may be arranged to have controlled stress within the layer. For example, at least one additional sacrificial layer may have tensile stress. Providing stress in the sacrificial layer may beneficially prestress at least one pellicle core layer. Prestressing the pellicle core layer may beneficially reduce sagging of the pellicle film when it is removed from the substrate and standing upright and when it is in use.

[0058]

[0058] The sacrificial layer adjacent to the pellicle film may comprise an oxide and may be substantially thinner than the pellicle film.

[0059]

[0059] Thin means that the thickness of the sacrificial layer adjacent to the pellicle film is substantially less than the thickness of the pellicle film. The sacrificial layer adjacent to the pellicle film may be known as a thin oxide layer. Thin oxide layers are readily grown to known thicknesses. A thin oxide layer adjacent to the pellicle film may provide a smooth surface for the pellicle film. A thin oxide layer adjacent to the pellicle film may enable a low-defect pellicle film.

[0060]

[0060] The first sacrificial layer or at least one of the additional sacrificial layers may comprise amorphous carbon. The amorphous carbon may, beneficially, reduce over-etching during pellicle fabrication and / or provide a diffusion barrier between layers of the pellicle film assembly and / or pre-stress the pellicle film.

[0061]

[0061] The sacrificial layer adjacent to the pellicle film may comprise amorphous carbon. The sacrificial layer adjacent to the pellicle film may be substantially thinner than the pellicle film. Beneficially, a thin amorphous carbon sacrificial layer may provide a favorable amount of reduction in overetching and / or diffusion and / or imparting of prestress.

[0062]

[0062] The first and third pellicle layers may comprise metal silicide. The second pellicle core layer may comprise amorphous carbon. Beneficially, the amorphous carbon pellicle core layer may provide tension in the pellicle film. Beneficially, the amorphous carbon pellicle core layer may reduce sagging in the pellicle film.

[0063]

[0063] According to a third aspect of the present invention, a method for producing a pellicle film is provided, comprising providing at least one amorphous carbon layer adjacent to a pellicle layer that forms at least a portion of the pellicle film.

[0064]

[0064] Amorphous carbon is beneficial in that it can reduce over-etching during pellicle fabrication and / or provide a diffusion barrier between layers of the pellicle film assembly and / or pre-stress the pellicle film.

[0065]

[0065] The pellicle core layer may comprise a metal silicide or a doped metal silicide. Metal silicides and doped metal silicides may be beneficial for use in pellicle films due to their high EUV transmittance. Their high emissivity can also beneficially lower the operating temperature of the pellicle film, thereby reducing the risk of damage to the pellicle film during use. Furthermore, using a metal silicide or a doped metal silicide as the pellicle core layer may alleviate or eliminate the need for an additional radiant capping layer on the front and / or back surfaces of the pellicle film due to their emissivity. Advantageously, eliminating the requirement for a radiant capping layer can reduce manufacturing time and / or reduce damage to the pellicle film during manufacturing.

[0066]

[0066] According to a fourth aspect of the invention, a pellicle film assembly is provided, comprising a substrate, at least one amorphous carbon layer, and a pellicle film.

[0067]

[0067] Amorphous carbon is beneficial in that it can reduce over-etching during pellicle fabrication and / or provide a diffusion barrier between layers of the pellicle film assembly and / or pre-stress the pellicle film.

[0068]

[0068] The pellicle core layer may comprise a metal silicide or a doped metal silicide. Metal silicides and doped metal silicides may be beneficial for use in pellicle films due to their high EUV transmittance. Their high emissivity can also beneficially lower the operating temperature of the pellicle film, thereby reducing the risk of damage to the pellicle film during use. Furthermore, using a metal silicide or a doped metal silicide as the pellicle core layer may alleviate or eliminate the need for an additional radiant capping layer on the front and / or back surfaces of the pellicle film due to their emissivity. Advantageously, eliminating the requirement for a radiant capping layer can reduce manufacturing time and / or reduce damage to the pellicle film during manufacturing.

[0069]

[0069] The thickness of the amorphous carbon layer may be substantially thinner than that of the pellicle film. Beneficially, a thin amorphous carbon sacrificial layer may provide a favorable amount of reduction in over-etching and / or diffusion and / or imparting of pre-stress.

[0070]

[0070] The substrate may form at least a portion of the border that holds the pellicle film.

[0071]

[0071] The border may be defined using one or more etching steps to remove at least a portion of the substrate and, optionally, one or more sacrificial layers, if present. A suitable etching solution can be selected depending on the specific material to be etched. The final etching step may be wet etching. Preferably, HF wet etching etches the tetraethyl orthosilicate layer.

[0072]

[0072] The border may also be referred to as a frame. The border may extend, for example, around the periphery of the pellicle film. By removing at least a portion of the substrate and one or more sacrificial layers, the pellicle film may be substantially peeled off from the substrate and one or more sacrificial layers.

[0073]

[0073] The peeled pellicle film may form part of a pellicle assembly, which comprises a pellicle film and a border that supports the pellicle film.

[0074]

[0074] The planar substrate may be an SOI (silicon-on-insulator) wafer. The planar substrate may be a silicon wafer. These types of substrates are well characterized and readily available.

[0075]

[0075] The planar substrate can be annealed to provide a thermal oxide layer before providing the tetraethyl orthosilicate layer.

[0076]

[0076] The border may consist of a stack of a portion of the planar substrate and a portion of the amorphous carbon layer in that order, with at least one amorphous carbon layer adjacent to the pellicle film.

[0077]

[0077] According to a fifth aspect of the invention, a lithography apparatus is provided comprising the pellicle assembly described above or a pellicle film or pellicle assembly manufactured in accordance with any of the preceding claims.

[0078]

[0078] Features described in any aspect of the present invention may be combined with features described in any other aspect of the present invention.

[0079]

[0079] Next, the present invention will be described with reference to an EUV lithography apparatus. However, it will be understood that the present invention is not limited to EUV lithography and may be suitable for other types of lithography as well. [Brief explanation of the drawing]

[0080]

[0080] Next, embodiments of the present invention will be described only as examples with reference to the attached schematic diagrams.

[0081] [Figure 1] This shows a lithography system equipped with a lithography device and a radiation source. [Figure 2] This shows the pellicle assembly. [Figure 3] The steps for manufacturing a pellicle film and a pellicle assembly according to one embodiment of the present invention are illustrated. [Figure 4] The steps for manufacturing a pellicle film and a pellicle assembly according to another embodiment of the present invention are illustrated. [Figure 5] The steps for manufacturing a pellicle film and a pellicle assembly according to another embodiment of the present invention are illustrated. [Figure 6] The steps for manufacturing a pellicle film and a pellicle assembly according to another embodiment of the present invention are illustrated. [Figure 7] The steps for manufacturing a pellicle film and a pellicle assembly according to another embodiment of the present invention are illustrated. [Figure 8] A flowchart illustrating the manufacturing process of the pellicle assembly is provided. [Modes for carrying out the invention]

[0082]

[0081] Figure 1 shows a lithography system comprising a radiation source SO and a lithography 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 lithography apparatus LA. The lithography 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.

[0083]

[0082] The illumination system IL is configured to adjust the EUV radiation beam B before it is incident on the patterning device MA. For this reason, the illumination system IL may include a faceted field mirror device 10 and a faceted pupil mirror device 11. Both the faceted field mirror device 10 and the faceted pupil mirror device 11 give the EUV radiation beam B a desired cross-sectional shape and a desired intensity distribution. In addition to or instead of the faceted field mirror device 10 and the faceted pupil mirror device 11, the illumination system IL may include other mirrors or devices.

[0084]

[0083] After being adjusted in this way, the EUV radiation beam B interacts with the patterning device MA. As a result of this interaction, a patterned EUV radiation beam B' is generated.

[0085]

[0084] Within the radiation path, a pellicle assembly 15 for protecting the patterning device MA is shown. The pellicle assembly 15 comprises a pellicle film 19 and a frame 17 supporting the pellicle film 19. The frame 17 may also be referred to as a border. The pellicle film 19 comprises a thin film that is substantially transparent to EUV radiation (but will absorb a small amount of EUV radiation). The pellicle film 19 acts to protect the patterning device MA from particle contamination. The pellicle film 19 may also be simply referred to as the pellicle. It will be understood that the pellicle assembly 15 may be in any required position and may be used to protect any element of the lithography apparatus, for example, one or more mirrors in the lithography apparatus.

[0086]

[0085] While a clean environment inside the lithography apparatus LA will be maintained, particles may still be present inside the lithography apparatus LA. Without the pellicle 19, particles may accumulate on the patterning device MA. Particles on the patterning device MA may adversely affect the pattern applied to the radiation beam B and, consequently, the pattern transferred to the substrate W. To prevent particles from accumulating on the patterning device MA, the pellicle 19 provides a barrier between the patterning device MA and the environment inside the lithography apparatus LA.

[0087]

[0086] When in use, the pellicle 19 is positioned at a sufficient distance from the patterning device MA such that particles incident on the surface of the pellicle 19 are not in the focal plane of the radiation beam B. This distance between the pellicle 19 and the patterning device MA acts to reduce the extent to which particles on the surface of the pellicle 19 impart a pattern to the radiation beam B. It will be understood that if particles are located in the radiation beam B but not in the focal plane of the radiation beam B (i.e., not on the surface of the patterning device MA), the image of the particles will not be in focus on the surface of the substrate W. In some embodiments, the distance between the pellicle 19 and the patterning device MA may be, for example, between 2 mm and 3 mm (e.g., about 2.5 mm). In some embodiments, the distance between the pellicle 19 and the patterning device may be adjustable.

[0088]

[0087] After the patterned EUV radiation beam B' is generated, 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 include a number 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 applies a reduction factor to the patterned EUV radiation beam B' so that it can form an image of a feature smaller than the corresponding feature in the patterning device MA. For example, a reduction factor of 4 or 8 can be applied. Although the projection system PS is shown in Figure 1 to have only two mirrors 13, 14, the projection system PS may include a different number of mirrors (e.g., 6 or 8 mirrors).

[0089]

[0088] The substrate W may include a pre-formed pattern. In this case, the lithography apparatus LA aligns the image formed by the patterned EUV radiation beam B' with the pre-formed pattern on the substrate W.

[0090]

[0089] A small amount of gas (e.g., hydrogen) at a relative vacuum, i.e., a pressure significantly below atmospheric pressure, can be provided within the radiation source SO, the illumination system IL, and / or the projection system PS.

[0091]

[0090] The radiation source SO shown in Figure 1 is of a type that can be called, for example, a laser-generated plasma (LPP) source. The laser system 1, which may include, for example, a CO2 laser, is arranged to impart energy via a laser beam 2 to a fuel, such as tin (Sn), provided from a fuel ejector 3. In the following description, we will refer to tin, but any suitable fuel may be used. The fuel may be in the form of, for example, a liquid, or it may be a metal or an alloy. The fuel ejector 3 may have a nozzle configured to guide, for example, tin in the form of droplets, along a trajectory toward the plasma-forming region 4. The laser beam 2 is incident on the tin in the plasma-forming region 4. The imparting of laser energy to the tin generates a tin plasma 7 in the plasma-forming region 4. From the plasma 7, radiation including EUV radiation is emitted during de-excitation and recombination of electrons with plasma ions.

[0092]

[0091] EUV radiation from the plasma is collected and focused by a collector 5. The collector 5 includes, for example, a near-normal incidence radiation collector 5 (sometimes more commonly referred to as a normal incidence radiation collector). The collector 5 may have 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 shape and have two foci. The first of the foci may be in the plasma-forming region 4, and the second of the foci may be in an intermediate focus 6, as will be described later.

[0093]

[0092] The laser system 1 may be spatially separated from the radiation source SO. In this case, the laser beam 2 can be delivered from the laser system 1 to the radiation source SO with the help of a beam delivery system (not shown) equipped with, for example, a suitable guide mirror and / or beam expander and / or other optical components. The laser system 1, the radiation source SO, and the beam delivery system together may be considered a radiation system.

[0094]

[0093] 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, forming an image of the plasma in the plasma-forming region 4 at the intermediate focus 6. The image at the intermediate focus 6 acts as a virtual radiation source for the illumination system IL. The radiation source SO is positioned such that the intermediate focus 6 is located at or near the aperture 8 of the internal structure 9 of the radiation source SO.

[0095]

[0094] Figure 1 shows the SO radiation source as a laser-generated plasma (LPP) source, but any suitable radiation source such as a discharge-generated plasma (DPP) source or a free-electron laser (FEL) can be used to generate EUV radiation.

[0096]

[0095] Figure 2 is a more detailed schematic view of a cross-section of the pellicle assembly 15 and the patterning device MA. The patterning device MA has a pattern surface 24. The pellicle frame 17 (or "border") supports the pellicle 19 around its periphery. The pellicle frame 17 may include a mounting mechanism 22 configured to allow the pellicle frame 17 to be detachably attached to the patterning device MA (i.e., to allow the pellicle frame 17 to be both attachable to and detachable from the patterning device MA). The mounting mechanism 22 is configured to engage with a mounting feature (not shown) provided to the patterning device MA. The mounting feature may be, for example, a projection extending from the patterning device MA. The mounting mechanism 22 may include, for example, a locking member that engages with the projection to secure the pellicle frame 17 to the patterning device MA. The pellicle frame 17 may be attached to the mask via a further pellicle frame. Multiple mounting mechanisms and associated mounting features may be provided. The mounting mechanism may be distributed around the pellicle frame 17 (for example, two on one side of the frame and two on the other side). The associated mounting features may be distributed around the periphery of the patterning device MA. It should be understood that any other mounting mechanism or positioning method may be used to position the pellicle film 19 in the desired position.

[0097]

[0096] Figure 2 schematically shows contaminating particles 26. The contaminating particles 26 are incident on the pellicle 19 and are held by the pellicle 19. The pellicle 19 holds the contaminating particles well away from the pattern surface 24 of the mask MA so that the contaminating particles are not imaged on the substrate by the lithography apparatus LA. A pellicle assembly according to one embodiment of the present invention may enable the provision of a mask pattern (on a patterning device) that remains substantially defect-free during use (the mask pattern is protected from contamination by the pellicle).

[0098]

[0097] The pellicle assembly 15 can be constructed by directly depositing the pellicle 19 onto a substrate that provides the frame 17. The substrate may be, for example, a silicon wafer or an SOI wafer. After the deposition of the film defining the pellicle 19, the substrate may be selectively back-etched to remove the central portion of the substrate, leaving only the outer periphery, in order to form the frame 17 for supporting the pellicle 19. The fabrication process is described further below.

[0099]

[0098] Pellicles are known in the art and typically have a core layer made of silicon, for example, polysilicon. The applicant recognizes that various other materials may be useful. In particular, the applicant has found that metal silicide or doped metal silicide may be useful.

[0100]

[0099] Doped metal silicide is given by formula M x (Si) y D z It can be described by the following: where M represents a metal, Si represents silicon, and D represents a dopant. The subscripts x, y, and z represent the relative ratios of M, Si, and D, respectively.

[0101] [000100] Metal M can be one of various metals. For example, the metal can be selected from the group comprising Ce, Pr, Sc, Eu, Nd, Ti, V, Cr, Zr, Nb, Mo, Ru, Rh, La, Y, and Be. Of this group, preferred metals are zirconium, molybdenum, or beryllium. Molybdenum is the most preferred.

[0102] [000101] Dopant D can be one of several dopants. For example, the dopant can be oxygen, carbon, boron, or nitrogen. Of these, nitrogen is a preferred dopant.

[0103] [000102] Of particular interest are molybdenum silicide nitride (MoSiN) and molybdenum silicide (MoSi). The relative ratio of molybdenum, silicon, and optionally nitrogen can be changed.

[0104] [000103] The deposition of metal silicides or doped metal silicides will be described below with reference to MoSiN and MoSi from time to time, but it should be understood that the following processes are applicable to any metal silicide or doped metal silicide.

[0105] [000104] Metallic silicides are radioactive materials. Radioactive materials are generally desirable for films in lithography equipment (or any system in which the film is in a radiation beam). Radioactive materials emit infrared radiation and can therefore lose heat gained by absorbing radiation. As mentioned above, heating of the pellicle is a problem and can lead to damage and / or fracture of the pellicle. Radioactive materials can beneficially lower the operating temperature of the pellicle, which in turn can increase the lifespan of the pellicle and / or reduce damage to the pellicle.

[0106] [000105] Typically, the pellicle is not highly radioactive but is treated with radioactive materials such as ruthenium and / or molybdenum and / or zirconium. For example, a pellicle with a silicon core layer must be treated to increase its radioactivity. This has been done by providing a radioactive capping layer on the front and / or back of the pellicle film. This capping layer is generally provided on a self-supporting pellicle, for example, by depositing the radioactive material onto a pellicle film that is freely suspended within a frame. This process may also be called deposition on a self-supporting pellicle. This process may also be called back-end of line processing, depending on its temporal position as the final or near-final process step in the production line. Significant manufacturing difficulties arise from back-end of line processing. In particular, due to the self-supporting nature of the pellicle film at this point, the film is easily damaged. Also, if any damage occurs at this stage of the production line, the entire process must be repeated, leading to long delays. Therefore, it is beneficial to reduce or eliminate back-end of line processing.

[0107] [000106] The applicant recognizes that by using a radioactive material such as metal silicide or doped metal silicide as the core layer of the pellicle, all additional treatments (and consequently back-end obline treatments) to enhance radioactivity can be reduced or avoided.

[0108] [000107] However, typical production lines and technologies for manufacturing typical pellicles are not suitable for manufacturing pellicles having metal silicide or doped metal silicide as a core layer, especially with the mass production capacity required for pellicles. Therefore, the applicant has developed a manufacturing technology that enables the production of pellicles having metal silicide or doped metal silicide as a core layer.

[0109] [000108] Typically, the pellicle core layer, such as silicon, is deposited using chemical vapor deposition (CVD). 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 in the material.

[0110] [000109] On the other hand, the deposition of doped metal silicides is preferentially carried out using physical vapor deposition (PVD) rather than CVD. Beneficially, PVD has better process control and therefore the amount of dopant can be controlled in a more controlled manner. Furthermore, PVD has better process control with respect to the thickness, uniformity, and repeatability of the doped metal silicide and metal silicide deposition. Another advantage of PVD is its directional deposition. Because PVD deposits directionally, the area of ​​deposition can be selected relatively easily compared to CVD, where material may be deposited in unwanted areas. For example, when depositing material on a substrate, it is relatively easy to deposit material on only one surface (or only one area) of the substrate using PVD, whereas CVD will preferentially deposit material on all surfaces of the substrate. Deposition on only one surface or area represents a reduction in the use of raw materials, which is advantageous, for example, in terms of cost and environmental concerns. Unnecessary areas of the material can be removed later in the manufacturing process, which could lead to contamination of the pellicle film, processing equipment, or lithography equipment; therefore, reducing the use of raw materials is also beneficial for reducing contamination.

[0111] [000110] There are some initial drawbacks to using PVD, and the methods of the embodiments of the present invention overcome them.

[0112] [000111] Depositing a pellicle layer comprising metal silicide or doped metal silicide onto a substrate has the disadvantage that the layer is not conformal. For example, if the substrate has any surface texture, the pellicle layer will not completely cover all surface features, and defects may be formed. For example, there may be pinholes (i.e., gaps) in the layer, there may be areas of greater or lesser depth, and / or "bridged" features, which may create air between parts of the layer and the substrate. Bridged features are particularly common between two proximal surface features of the substrate, where the layer covering those features does not contact the surface between the features but is suspended between them. All defects can reduce the quality of the resulting pellicle film and may lead to fracture, for example. Bridged features are particularly problematic because these suspended areas may break either during manufacturing or in use, contaminating the pellicle film or other areas of the manufacturing equipment or lithography apparatus.

[0113] [000112] Another drawback of PVD is that, due to the direction of the process, it is typically required to process one (or a few) wafers at a time. As a result, the speed of production is relatively slow compared to conventional methods. In order to enable mass production of metal silicide and doped metal silicide pellicles, the speed must be increased.

[0114] [000113] The applicant has developed a manufacturing process that can produce pellicles having a pellicle layer of metal silicide or doped metal silicide with the required quality and yield. The manufacturing process is described below with reference to Figures 3 to 5 and 7 as an embodiment.

[0115] [000114] Note that the drawings are not illustrative and are therefore not drawn to scale. This is particularly important, for example, when considering the thickness of the pellicle layer in relation to a planar substrate. This is also particularly important when considering the stages of manufacturing. Key stages of manufacturing are shown, but these are essentially illustrative, and it should be understood that additional steps and processes may be performed before, during, between, and / or after the illustrated steps. Also, some stages may be illustrated as a single step (e.g., an etching process), but in reality they may be carried out as several successive small processes and have the effect as a whole that is illustrated by that single step.

[0116] [000115] The following process refers to etching. Etching is a common manufacturing process used to remove a portion of a material. In multilayer materials, selective etching can remove a portion of an outer layer so that an underlying layer is exposed. Etching may comprise providing a resist, such as a photoresist, and patterning the resist. The present invention is not particularly limited by the properties of the resist, and any suitable resist may be used. The resist helps to protect the underlying layer from etching. Thus, patterning the resist helps to define areas of the stack that will be removed by subsequent etching steps. The etching solution may be a chemical etching solution, such as phosphoric acid and / or hydrofluoric acid.

[0117] [000116] Figure 3 schematically illustrates the steps of manufacturing a pellicle assembly 15 according to one embodiment of the present invention. The pellicle assembly (and master stage) is shown in cross-section.

[0118] [000117] A planar substrate 30 is provided, which may simply be referred to as the substrate 30. The substrate 30 may be, for example, a silicon wafer. 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 it will probably be a circle, because this is the most commonly available shape. The size of the substrate 30 is not particularly limited.

[0119] [000118] The first sacrificial layer 31 is provided, for example, by depositing it on a substrate 30. The substrate 30 and the sacrificial layer 31 together may be referred to as a stack. The first sacrificial layer 31 preferably substantially surrounds the substrate 30, but depending on the embodiment, it may only partially surround the substrate 30. The first sacrificial layer may comprise an oxide, such as silicon oxide or a thermal oxide. The first sacrificial layer 31 beneficially provides a substantially flat surface for preparation for receiving the 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 can be beneficially provided for preparation for receiving the pellicle layer. In other words, the first sacrificial layer controls the surface topology.

[0120] [000119] The pellicle film 19 is provided on the surface of the first sacrificial layer 31. That is, the pellicle film 19 is provided on the surface of the stack. The pellicle film 19 may comprise one or more pellicle layers. Several exemplary embodiments of multilayer pellicle films are further described below with reference to Figure 5. The pellicle film 19 shown in Figure 3 comprises a single pellicle layer comprising a doped metal silicide. The pellicle layer forms the core layer of the pellicle film 19.

[0121] [000120] As previously mentioned, metal silicides and doped metal silicides can be deposited by physical vapor deposition (PVD). Since the deposition of metal silicides or doped metal silicides by this method results in a non-conformal coating, it is important to provide a smooth and / or clean surface (i.e., a surface with a small number / low density of contaminant particles) beneath the pellicle film 19 (i.e., the surface on which the pellicle layer is deposited). On the other hand, a rough and / or contaminated surface can lead to pores in the pellicle layer and / or contamination of the film and other equipment, as described above.

[0122] [000121] Additionally or alternatively, the surface beneath the pellicle film 19 can be optimized by beneficially controlling its surface topology. Thus, in addition to or instead of a smooth and / or clean surface, the surface may, beneficially, have a small number of pinholes and / or a uniform layer thickness.

[0123] [000122] Providing the first sacrificial layer 31 can beneficially provide an optimized surface compared to the coating on the substrate 30. The first sacrificial layer 31 may be adjusted to provide better smoothness; for example, a thicker first sacrificial layer 31 may provide a smoother surface. The first sacrificial layer 31 may be adjusted to provide a surface relatively free of contaminant particles and / or a uniform thickness and / or a small number of pinholes. Alternatively (or additionally), an additional sacrificial layer may be added between the first sacrificial layer 31 and the pellicle film 19.

[0124] [000123] After the deposition of the pellicle film 19, the substrate 30 and the first sacrificial layer 31 can be selectively back-etched to remove the central portions of the substrate and sacrificial layer, leaving only the outer periphery, in order to form a frame 17 for supporting the pellicle film 19. Thus, the frame 17 comprises a portion of the substrate 30 and a portion of the first sacrificial layer 31, the first sacrificial layer 31 being positioned between the substrate 30 and the pellicle film 19.

[0125] [000124] The pellicle layer comprises a doped metal silicide, some of which have been described above. In particular, the pellicle layer is radioactive, which eliminates the need for back-end obline processing, i.e., an additional process step following back-etching of the substrate 30 and sacrificial layer 31 to form the frame 17 of the pellicle assembly 15. Eliminating this process reduces the risk of damage to the pellicle film 19 and increases the speed of manufacturing a single pellicle assembly 15. The speed is increased in part because the back-end obline processing is eliminated. The speed is also increased in part because only one radioactive layer deposition step is required (in contrast to two radioactive layer deposition steps which are beneficial for known silicon pellicles where both the front and back surfaces must be covered). This is particularly important because, in a typical processing line, the radioactive layer deposition step can be a “bottleneck” tool that greatly increases the processing time of the pellicle assembly, so reducing the number of radioactive layer deposition steps can greatly reduce the processing time of the pellicle assembly.

[0126] [000125] Figure 3 shows a stack having one sacrificial layer, but additional sacrificial layers may be provided. Any number, for example, one or four additional sacrificial layers may be provided. Figure 4 schematically illustrates the steps of manufacturing the pellicle assembly 15 according to one embodiment of the present invention when two additional sacrificial layers are provided. That is, three sacrificial layers 31a, 31b, and 31c are provided between the substrate 30 and the pellicle film 19.

[0127] [000126] Similar to the previous embodiment, a planar substrate 30 is provided, which may simply be referred to as the substrate 30. The substrate 30 may be, for example, a silicon wafer. 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 it will probably be a circle, because this is the most commonly available shape. The size of the substrate 30 is not particularly limited.

[0128] [000127] The first sacrificial layer 31a is provided, for example, by depositing it on the substrate 30. The first sacrificial layer 31a preferably substantially surrounds the substrate 30, but depending on the embodiment, it may only partially surround the substrate 30. The first sacrificial layer 31a comprises an oxide, for example, silicon oxide or a thermal oxide.

[0129] [000128] Next, a second sacrificial layer 31b is provided, for example, by depositing it on the first sacrificial layer 31a. The second sacrificial layer 31b preferably substantially surrounds the first sacrificial layer 31a, but depending on the embodiment, it 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, a second sacrificial layer 31b comprising ISDP may be formed with relatively low roughness and few protrusions.

[0130] [000129] Adjacent sacrificial layers (e.g., first and second sacrificial layers 31a, 31b) formed from different materials (in this case, oxide and silicon) will etch at different rates with respect to a given etching operation. That is, with respect to a particular etching operation, the first sacrificial layer 31a may etch quickly, while the second sacrificial layer 31b may etch relatively slowly or not etch at all. In this way, adjacent sacrificial layers formed from different materials can be advantageously formed in one layer to stop etching with respect to a given etching operation.

[0131] [000130] The third sacrificial layer 31c is provided, for example, by depositing it on the second sacrificial layer 31b. The third sacrificial layer 31c preferably substantially surrounds the second sacrificial layer 31b, but depending on the embodiment, it 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 a thermal oxide. Thin means that the thickness of the third sacrificial layer 31c is substantially less than the thickness of the pellicle film 19. The third sacrificial layer 31c may be known as a thin oxide layer 31c. Thin layers of oxide are readily grown to known thicknesses, as is known in the art. Thus, the thin oxide layer 31c may be formed with low surface roughness. This thus provides a smooth surface for depositing the pellicle film 19.

[0132] [000131] At this stage, the substrate 30 and the first, second, and third sacrificial layers 31a, 31b, and 31c may be referred to as a stack.

[0133] [000132] Before depositing the pellicle film, the sacrificial layers 31a, 31b, 31c are patterned to define the areas that will later become the borders, thereby defining the shape of the final pellicle assembly. That is, the faces of the stack are patterned to define the shape of the final pellicle assembly. These faces may also be referred to as the "back" faces of the stack and are defined as the faces opposite to the faces that will receive the pellicle film 19. This process may be known as the patterning process. This patterning process may be carried out using any suitable resist and etching process. During this process, the substrate may be handled by equipment, for example, by clamping it in place and / or inverting it. Such handling may damage or contaminate one or more surfaces of the substrate or associated sacrificial layers. By performing this patterning process before depositing the pellicle film 19, the risk of damage to the pellicle film 19 can be reduced. While a specific pattern is shown in Figure 4, it should be understood that any alternative pattern may be generated depending on the desired final shape of the pellicle assembly.

[0134] [000133] Following the patterning process, a pellicle film 19 is provided on the surface of the third sacrificial layer 31c. The pellicle film 19 may comprise one or more pellicle layers. The pellicle film 19 shown in Figure 4 comprises a single pellicle layer. The pellicle layer comprises a doped metal silicide, some of which have been described above. The pellicle layer in this embodiment or other embodiments may alternatively comprise a metal silicide.

[0135] [000134] One or more capping layers may be accompanied by pellicle layers. These capping layers may be provided as etching stops 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 film. The capping layers may comprise, for example, an oxide. The capping layers may be deposited with a stress comparable to that of the third sacrificial layer 31c, which is beneficial. The capping layers may be configured to have an etching time similar to that of the third sacrificial layer 31c, which is beneficial.

[0136] [000135] After the deposition of the pellicle film 19, further portions of the substrate 30, the first sacrificial layer 31a, the second sacrificial layer 31b, and the third sacrificial layer 31c may be selectively back-etched so as to remove a portion of the substrate 30 (and portions of the sacrificial layers 31a, 31b, and 31c) leaving only the outer periphery to form a frame 17 for supporting the pellicle film 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. Before contacting the pellicle film 19, the frame 17 can be said to have a sequential stack of the substrate 30, the first sacrificial layer 31a, the second sacrificial layer 31b, and portions of the third sacrificial layer 31c. In one example, considering some of the materials described above with reference to this embodiment, the frame 17 may have a stack of silicon, oxide, ISDP, and thin oxide in that order before contacting the doped metal silicide pellicle film. Alternatively, the frame 17 may have a stack of silicon, oxide, silicon, and thin oxide in that order before contacting the doped metal silicide pellicle film. Depending on the number and composition of the sacrificial layers, it should be understood that the frame 30 may have a stack of layers in that corresponding order.

[0137] [000136] The choice of sacrificial layer composition can further help reduce the processing time of the pellicle assembly. For example, some processes constitute a “bottleneck” in the manufacturing process, such as the formation of silicon nitride or ISDP. Beneficially, these materials may be omitted from some embodiments of the present invention, thereby reducing the processing time.

[0138] [000137] In the above example, a process for forming a pellicle film comprising a single doped metal silicide pellicle layer has been described. However, a pellicle film may comprise multiple pellicle layers. Figure 5 illustrates an exemplary embodiment of such a pellicle film, schematically illustrating the steps for manufacturing a pellicle assembly 15 having a pellicle film 19 comprising three pellicle layers 50a, 50b, and 50c.

[0139] [000138] Similar to the previous embodiment, a planar substrate 30 is provided, which may simply be referred to as the substrate 30. The substrate 30 may be, for example, a silicon wafer. 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 it will probably be a circle, because this is the most commonly available shape. The size of the substrate 30 is not particularly limited.

[0140] [000139] The first sacrificial layer 31 is provided, for example, by depositing it on a 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, it may only partially surround the substrate 30. The first sacrificial layer 31 may comprise an oxide, such as silicon oxide or a thermal oxide. The first sacrificial layer 31 beneficially provides a substantially flat surface in preparation for receiving the pellicle layer. Although not shown, additional sacrificial layers may also be provided before depositing the pellicle layer. Similar to the embodiment shown in Figure 4, the sacrificial layer 31 is patterned before depositing the pellicle layer. This patterning process is carried out to define areas that will later become borders, thereby defining the shape of the final pellicle assembly. However, it should be noted that this patterning process before depositing the pellicle layer is beneficial, but not required, to reduce damage to the pellicle layer.

[0141] [000140] A first pellicle layer 50a is provided on the first sacrificial layer 31. The first pellicle layer 50a comprises a metal silicide. A second pellicle layer 50b is provided on the first pellicle layer 50a. The second pellicle layer 50b comprises a doped metal silicide. A third pellicle layer 50c is provided on the second pellicle layer. The third pellicle layer 50c comprises a metal silicide, for example, the same metal silicide as that comprising the first pellicle layer 50a. The first, second, and third pellicle layers 50a, 50b, 50c form a pellicle film 19. It should be understood that different numbers of pellicle layers, for example, two pellicle layers or five pellicle layers, may be deposited in a similar manner to form a multilayer pellicle film.

[0142] [000141] After the deposition of the first, second, and third pellicle layers 50a, 50b, and 50c, the substrate 30 and the first sacrificial layer 31 can be selectively back-etched to remove a portion of the substrate and sacrificial layer, leaving only the outer periphery, in order to form a frame for supporting the pellicle film 19. Thus, the frame 17 comprises a portion of the substrate 30 and a portion of the first sacrificial layer 31, the first sacrificial layer 31 being positioned between the substrate 30 and the pellicle film 19.

[0143] [000142] Although the above process describes the manufacturing of the pellicle assembly 15, it should be understood that it also describes the manufacturing of the pellicle film 19 deposited on the stack (for example, on a substrate 30 having one or more sacrificial layers). In some cases, for example, if these etching steps are performed at a later date or in a different location, it may be beneficial to manufacture only the pellicle film on the stack without defining the border.

[0144] [000143] In pellicle manufacturing, the final etching step, for example, etching away the material so that only the outer periphery supporting the pellicle film remains, can be critical to the quality of the resulting pellicle film. This etching step is generally carried out using wet etching with common etching solutions such as buffer oxide etching (BOE), tetramethylammonium hydroxide (TMAH), or hydrofluoric acid (HF).

[0145] [000144] The above process describes providing one or more sacrificial layers beneath the pellicle film 19 (i.e., between the pellicle film 19 and the substrate 30). However, to protect the upper surface of the pellicle film 19 during additional process steps, for example, it would be beneficial to provide a sacrificial layer on top of the pellicle film 19 (i.e., on the side of the pellicle film 19 distal to the substrate 30).

[0146] [000145] It may be beneficial to provide sacrificial layers both above and below the pellicle film. Over-etching can be mitigated by providing sacrificial layers both above and below the pellicle film, and by matching the thickness of the sacrificial layer above the pellicle film with the sacrificial layer below the pellicle film. For example, if the thickness of the sacrificial layer above and below the pellicle film are the same, the upper sacrificial layer will etch at the same rate as the lower sacrificial layer. This is in contrast to uneven layers, which etch at different rates, and thus one layer may be under-etched or over-etched.

[0147] [000146] It should be understood that "up" and "down" are relative terms used in the orientation presented in the drawings. Since the pellicle assembly and master stage can be oriented in any way, these terms should not be interpreted as restrictive.

[0148] [000147] Figure 6 schematically illustrates the steps of manufacturing a pellicle assembly 15 according to one embodiment of the present invention. The pellicle assembly (and master stage) is shown in cross-section.

[0149] [000148] A planar substrate 30 is provided, which may simply be referred to as the substrate 30. The substrate 30 may be, for example, a silicon wafer. 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 it will probably be a circle, because this is the most commonly available shape. The size of the substrate 30 is not particularly limited.

[0150] [000149] The first sacrificial layer 31 is provided, for example, by depositing it on a 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 depending on the embodiment, it may only partially surround the substrate 30. The first sacrificial layer 31 may comprise an oxide, such as silicon oxide or a thermal oxide.

[0151] [000150] A second sacrificial layer 60 is provided adjacent to the first sacrificial layer 31. This forms an updated stack, which comprises a planar substrate 30, the first sacrificial layer 31, and the second sacrificial layer 60. In this embodiment, the second sacrificial layer 60 comprises amorphous carbon. Such an amorphous carbon layer 60 may be provided before the pellicle film 19, but it will be understood that the layers may be provided in different arrangements.

[0152] [000151] A pellicle film 19 is provided on the surface of an amorphous carbon layer 60. The pellicle film 19 may comprise one or more pellicle layers. The pellicle film 19 shown in Figure 6 comprises a single pellicle layer that forms the pellicle film 19.

[0153] [000152] After the deposition of the pellicle film 19, the substrate 30 and the first sacrificial layer 31 are selectively back-etched to remove the central portions of the substrate and sacrificial layer, leaving only the outer periphery, in order to form a frame for supporting the pellicle film 19 and the amorphous carbon layer 60. This frame supporting the pellicle film 19 and the amorphous carbon layer 60 may be known as a pre-assembly 62.

[0154] [000153] Finally, a portion of the amorphous carbon layer 60 may be removed so as to leave only the outer periphery to form a frame 17 for supporting the pellicle film 19, thereby forming the pellicle assembly 15. Thus, the frame 17 comprises a portion of the substrate 30, a portion of the first sacrificial layer 31, and a portion of the amorphous carbon layer 60, the amorphous carbon layer 60 being disposed between the first sacrificial layer 31 and the pellicle film 19. Several processes, such as plasma treatment, can be used to remove the amorphous carbon layer 60, for example, using free radicals such as hydrogen radicals. In fact, any suitable method may be used to remove the amorphous carbon, and the present invention is not particularly limited by the specific method used.

[0155] [000154] Amorphous carbon is highly etchable to several common etching solutions, including, but not limited to, buffer oxide etching (BOE), tetramethylammonium hydroxide (TMAH), and hydrofluoric acid (HF). Amorphous carbon can be removed from the pre-assembly 62 without damaging the pellicle film 19, for example, by plasma treatment. Since plasma treatment is a faster process than etching, the use of an amorphous carbon layer and subsequent removal using plasma treatment is beneficial in that it saves time in the pellicle manufacturing process.

[0156] [000155] The provision of the amorphous carbon layer 60 significantly reduces the possibility of over-etching, thereby reducing the risk of damage to the pellicle film 19 during the etching step. For example, in an etching step to selectively remove the central portion of the substrate and the sacrificial layer, the amorphous carbon layer 60 can reduce or mitigate the possibility that the etching solution will remove any portion of the pellicle film (i.e., over-etch). Since the possibility of damage or fracture of the pellicle film is reduced or mitigated, this results in an increase in yield in pellicle film manufacturing. In addition, the etching resistance of the amorphous carbon layer allows adjacent layers to be removed using a more aggressive and / or rapid etching process without endangering the intact state of the pellicle film. Thus, such an etching process can be carried out more quickly than without the amorphous carbon layer, which beneficially means time savings in the pellicle manufacturing process.

[0157] [000156] The use of an amorphous carbon layer also provides greater flexibility in the selection of other sacrificial layers, such as their properties, including composition and / or thickness. This flexibility in sacrificial layer selection is provided by the etching-stopping ability of amorphous carbon, thereby reducing the technical and design constraints on other sacrificial layers that were previously required to reduce over-etching.

[0158] [000157] The use of amorphous layers offers greater flexibility in the selection of materials for the pellicle layer due to their high etching resistance. The use of etching stop layers such as amorphous carbon layers is particularly beneficial when used in combination with a pellicle layer of metal silicide or doped metal silicide. Since metal silicide and doped metal silicide are particularly sensitive to over-etching, it is beneficial to reduce the possibility of over-etching by using, for example, an amorphous carbon layer. Furthermore, etching stop layers such as amorphous carbon layers are particularly beneficial when used with other materials that are easily wet-etched, such as zirconium.

[0159] [000158] The amorphous carbon layer 60 may be provided beneath the pellicle film 19, as shown in Figure 6. The amorphous carbon layer may also be provided above the pellicle film, which may protect the top layer of the pellicle film 19 from over-etching and other potential damage in other process steps. The amorphous carbon layer may further be used in other stages of the pellicle manufacturing process to protect other surfaces and / or to reduce over-etching of other surfaces.

[0160] [000159] Furthermore, amorphous carbon provides an efficient diffusion barrier. The diffusion barrier reduces the risk of material diffusion between adjacent layers. For example, when a first sacrificial layer comprising an oxide is used, oxygen can diffuse into the pellicle film. Diffusion may increase when the pre-assembly is heated, for example, during the heat treatment of oxides common in pellicle manufacturing or during the annealing process.

[0161] [000160] It would be beneficial to reduce diffusion into the pellicle layer. For example, optimizing the EUV transmittance of the pellicle film may be beneficial, but diffused material can reduce the EUV transmittance. In one specific example, the diffusion of oxygen from a sacrificial layer containing an oxide into a pellicle layer containing a metal silicide may form a metal oxide, which has a reduced EUV transmittance compared to a metal silicide without a metal oxide. Therefore, a diffusion barrier between the sacrificial layer and the pellicle layer, such as an amorphous carbon layer, can optimize the EUV transmittance of the pellicle film.

[0162] [000161] By providing a layer of amorphous carbon between the oxide sacrificial layer and the metal silicide pellicle layer, the diffusion of elements between the sacrificial layer and the pellicle layer is reduced. The amorphous carbon diffusion barrier layer can reduce interlayer diffusion to a virtually negligible level. In other words, diffusion across the diffusion barrier does not occur virtually, even during or after heating. Furthermore, there is no diffusion of carbon from the amorphous carbon layer into the pellicle film.

[0163] [000162] The amorphous carbon layer 60 can also be used as a stress control element. By controlling the properties of one or more layers adjacent to the pellicle film 19, the amount of stress in the pellicle film 19 during manufacturing can be reduced. The amorphous carbon layer can act as a stress reduction element to reduce the amount of stress on the pellicle film 19 during manufacturing, or it can apply stress, for example, as a pre-stressing element.

[0164] [000163] The thickness of the amorphous carbon layer may be selected to control the amount of diffusion and to optimize other physical properties of the layer, such as stress control. For example, an amorphous carbon layer having a substantially thinner thickness than the pellicle film may beneficially provide an efficient barrier to diffusion, provide an etching stop layer, and beneficially prestress the pellicle layer.

[0165] [000164] In another embodiment, an amorphous carbon layer is used as a pellicle core layer between two pellicle layers. For example, the pellicle film may comprise a set of metal silicide layers, amorphous carbon layers, and a second metal silicide layer in that order. Advantageously, the amorphous carbon layer in this embodiment can beneficially adjust the amount of tension in the pellicle film. Controlling the tension in the pellicle film can reduce sagging in the pellicle film.

[0166] [000165] Figures 7a to 7i schematically illustrate the manufacturing steps of the pellicle assembly 15 according to one embodiment of the present invention. The pellicle assembly (and master stage) is shown in cross-section. Note that not all intermediate steps are shown.

[0167] [000166] Similar to the previous embodiment, a planar substrate 30 is provided, as shown in Figure 7a, which may simply be referred to as the substrate 30. The substrate 30 may be, for example, a silicon wafer. 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 it will probably be a circle, because this is the most commonly available shape. The size of the substrate 30 is not particularly limited.

[0168] [000167] The first sacrificial layer 31a is provided, for example, by depositing it on the substrate 30. The first sacrificial layer 31a preferably substantially surrounds the substrate 30, but depending on the embodiment, it may only partially surround the substrate 30. The first sacrificial layer 31a preferably comprises an oxide, such as silicon oxide or a thermal oxide. The first sacrificial layer 31a may comprise silicon dioxide, or may consist essentially of silicon dioxide.

[0169] [000168] Next, a second sacrificial layer 31b is provided, for example, by depositing it on the first sacrificial layer 31a. The second sacrificial layer 31b preferably substantially surrounds the first sacrificial layer 31a, but depending on the embodiment, it 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, a second sacrificial layer 31b comprising ISDP may be formed with relatively low roughness and few protrusions.

[0170] [000169] Adjacent sacrificial layers (e.g., first and second sacrificial layers 31a, 31b) formed from different materials (in this case, oxide and silicon) will etch at different rates with respect to a given etching operation. That is, with respect to a particular etching operation, the first sacrificial layer 31a may etch quickly, while the second sacrificial layer 31b may etch relatively slowly or not etch at all. In this way, adjacent sacrificial layers formed from different materials can be advantageously formed in one layer to stop etching with respect to a given etching operation.

[0171] [000170] The first and second sacrificial layers 31a, 31b are patterned to define the area that will later become the border, thereby defining the shape of the final pellicle assembly. That is, the faces of the stack are patterned to define the shape of the final pellicle assembly. These faces may also be referred to as the "back" faces of the stack and are defined as the faces opposite to the faces that will receive the pellicle film 19. This process may be known as the patterning process. This patterning process may be carried out using any suitable resist and etching process. In this process, the substrate may be handled by equipment, for example, by being clamped in place and / or inverted. Such handling may damage or contaminate one or more surfaces of the substrate or associated sacrificial layers. By performing this patterning process before depositing the pellicle film 19, the risk of damage to the pellicle film 19 can be reduced. While a specific pattern is shown in Figure 7, it should be understood that any alternative pattern may be generated depending on the desired final shape of the pellicle assembly.

[0172] [000171] The third sacrificial layer 31c is provided by depositing it on the second sacrificial layer 31b, for example, following a patterning process. The third sacrificial layer 31c preferably substantially surrounds the second sacrificial layer 31b, but depending on the embodiment, it 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 a thermal oxide. The oxide layer may be grown by chemical and / or thermal means known in the art. Thin means that the thickness of the third sacrificial layer 31c is substantially less than the thickness of the pellicle film 19. The third sacrificial layer 31c may be known as a thin oxide layer 31c. Thin layers of oxide are readily grown at known thicknesses, as known in the art. Thus, the thin oxide layer 31c may be formed with low surface roughness. This thus provides a smooth surface for depositing the pellicle film 19. Figure 7b shows a stack fabricated according to the present invention after patterning the back of the stack and subsequently providing the third sacrificial layer 31c.

[0173] [000172] At this stage, the substrate 30 and the first, second, and third sacrificial layers 31a, 31b, and 31c may be referred to as a stack.

[0174] [000173] As shown in Figure 7c, after the patterning process and the subsequent provision of the third sacrificial layer 31c, the pellicle film 19 is provided on the surface of the third sacrificial layer 31c. The pellicle film 19 may comprise one or more pellicle layers. The pellicle film 19 shown in Figure 7 comprises a single pellicle layer. The pellicle layer comprises a doped metal silicide, preferably a MoSiN layer, some of which have been described above for their benefits. The pellicle layer in this embodiment or other embodiments may alternatively comprise a metal silicide. The pellicle film 19 may be provided by any means known in the art.

[0175] [000174] One or more capping layers may be accompanied by pellicle layers. These capping layers may be provided as etching stops 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 film. The capping layers may comprise, for example, an oxide. The capping layers may be deposited with a stress comparable to that of the third sacrificial layer 31c, which is beneficial. The capping layers may be configured to have an etching time similar to that of the third sacrificial layer 31c, which is beneficial.

[0176] [000175] One or more capping layers may be provided as oxide layers, which may be derived from TEOS. Providing one or more capping layers on the pellicle film 19 is optional. The stack can be annealed with or without the provision of one or more capping layers. Annealing the stack provides suitable control of stress within the stack. The stack can be annealed under conditions known in the art, and the present invention is not particularly limited by the annealing conditions used.

[0177] [000176] After annealing the stack, one or more capping layers and a portion of the third sacrificial layer 31c may be etched, as shown in Figure 7d. If one or more capping layers are not provided, it will be the native oxide layer that is etched away. As shown in Figure 7d, this provides a stack having a pellicle film 19 provided on the third sacrificial layer 31c. Thus, the sacrificial or capping layer on or above the surface of the pellicle film 19 is removed at this stage, and the third sacrificial layer 31c disposed beneath the pellicle film 19 is retained.

[0178] [000177] The front of the stack may then be patterned to define the dimensions of the final pellicle assembly. The front of the stack may be patterned by any suitable means known in the art, and the present invention is not particularly limited by the patterning means used.

[0179] [000178] When the front of the stack is patterned, a protective layer 70 may be provided. The protective layer may be a polymer material such as perylene, as is known in the art. Figure 7e shows a stack in which the front of the stack has been patterned to provide a protective layer 70.

[0180] [000179] Once the protective layer 70 is provided, a so-called cavity etching process may be performed. The cavity etching process removes material from the core 30, the first sacrificial layer 31a, and the second sacrificial layer 31b. Figure 7f shows one embodiment of the present invention in which the material of the third sacrificial layer 31c beneath the pellicle film 19 is not removed during the cavity etching process. Alternatively, Figure 7h shows one embodiment of the present invention in which the material of the third sacrificial layer 31c beneath the pellicle film 19 is removed during the cavity etching process.

[0181] [000180] Thus, the substrate 30, a portion of the first sacrificial layer 31a, a portion of the second sacrificial layer 31b, and optionally a portion of the third sacrificial layer 31c are selectively back-etched so as to remove a portion of the substrate 30 (and, if necessary, portions of the sacrificial layers 31a, 31b, and 31c) leaving only the outer periphery to form a frame 17 for supporting the pellicle film 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. The third sacrificial layer may or may not spread into the pellicle film, depending on whether etching the third sacrificial layer 31c is selected during the cavity etching step. Before contacting the pellicle film 19, the frame 17 can be said to have a stack in the order of 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. In one example, with reference to this embodiment and considering some of the materials described above, the frame 17 may comprise a stack of silicon, oxide, ISDP, and thin oxide in that order before contacting the doped metal silicide pellicle film, preferably MoSiN. Alternatively, the frame 17 may comprise a stack of silicon, oxide, silicon, and thin oxide in that order before contacting the doped metal silicide pellicle film. Depending on the number and composition of the sacrificial layers, it should be understood that the frame 30 may comprise a stack of layers in that corresponding order. Figure 7g shows one embodiment of a pellicle assembly in which a third sacrificial layer 31c extends to the pellicle film 19, while Figure 7i shows one embodiment in which the third sacrificial layer 31c does not extend to the pellicle film 19.

[0182] [000181] The choice of sacrificial layer composition can further help reduce the processing time of the pellicle assembly. For example, some processes constitute a “bottleneck” in the manufacturing process, such as the formation of silicon nitride or ISDP. Beneficially, these materials may be omitted from some embodiments of the present invention, thereby reducing the processing time.

[0183] [000182] Figure 8 is an exemplary flowchart of the method shown in Figure 7. In the first step 100, first and second sacrificial layers are provided to the core. The core is preferably c-Si, but 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, the first sacrificial layer, and the second sacrificial layer may be referred to as a stack. In step 200, the back of the stack may be patterned. This may be done by any suitable means and helps define the shape of the final pellicle assembly by defining the dimensions of the frame that will support the pellicle film in the final assembly. In step 300, a further oxide layer known as a third sacrificial layer is provided on the patterned stack. The oxide layer may be formed by any known means, such as chemical oxidation or thermal oxidation. In step 400, the material to form the pellicle film is deposited on the surface of the patterned stack or otherwise provided. Step 500 is optional and comprises providing an additional sacrificial / capping layer on the patterned stack. This may be referred to as the top oxide. In step 600, the stack is annealed. The annealing step is known to be possible without the need for special protection provided by step 500. In step 700, the top oxide layer (if present) and / or any native oxide layer may be removed. Following the removal of the top oxide or native oxide layer (if present), in step 800, the front side of the stack is patterned to define the shape and dimensions of the pellicle film. Following the patterning in step 800, a protective layer, preferably a polymer protective material such as perylene, is provided to protect the pellicle film layer. Subsequently, in step 900, a cavity etching step is performed to etch away the core from the back side to form the frame of the pellicle assembly. Optionally, the sacrificial layer beneath the pellicle film is removed or retained in place in step 1000 or step 1100, if necessary. The final pellicle assembly may then be peeled from the protective layer.Since the sacrificial layers directly above or below the pellicle film are removed at different stages, it is possible to avoid the need for a wet HF etching step to remove such oxide layers. The process described in Figures 7 and 8 thereby avoids a wet HF etching step that could result in damage to the pellicle film and potential mechanical losses or failures during manufacturing, while also reducing the non-uniformity caused by partial over-etching of the pellicle film.

[0184] [000183] It should be understood that the features of the above embodiments can be combined. For example, as described in different embodiments, the use of amorphous carbon layers is applicable to use in a pellicle film comprising three pellicle layers, a pellicle assembly comprising three sacrificial layers, or any other features described above. The pellicle film may comprise one or more metal silicide layers and / or one or more doped metal silicide layers and / or one or more amorphous carbon layers.

[0185] [000184] Although this text specifically refers to the use of lithography equipment in the manufacture of ICs, it should be understood that lithography equipment described herein has other applications. Other possible applications include the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memory, flat panel displays, liquid crystal displays (LCDs), thin-film magnetic heads, and the like.

[0186] [000185] While embodiments of the present invention are specifically referenced in relation to lithography apparatus, embodiments of the present invention can also be used in other apparatuses. Embodiments of the present invention may form part of a mask inspection apparatus, a metrology apparatus, or any apparatus for measuring or processing objects such as wafers (or other substrates) or masks (or other patterning devices). These apparatuses are sometimes commonly referred to as lithography tools. Such lithography tools may be used under vacuum conditions or ambient (non-vacuum) conditions.

[0187] [000186] Where permitted by context, 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 in a machine-readable medium that can be read and executed by one or more processors. The 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, the machine-readable medium may include read-only memory (ROM), random access memory (RAM), magnetic storage media, optical storage media, flash memory devices, propagating signals of electrical, optical, acoustic or other forms (e.g., carrier waves, infrared signals, digital signals, etc.), and others. Furthermore, firmware, software, routines, and instructions may be described herein as performing specific actions. However, such descriptions are merely for convenience, and it should be understood that such actions actually originate from a computing device, processor, controller, or other device that performs the firmware, software, routines, instructions, etc., and that in the process, actuators or other devices may interact with the material world.

[0188] [000187] Although specific embodiments of the present invention have been described above, it will be understood that the present invention may be carried out in ways other than those described. The above description is intended to be illustrative and not limiting. Accordingly, it will be apparent to those skilled in the art that modifications to the described invention can be made without departing from the scope of the claims set forth below.

Claims

1. A pellicle membrane assembly comprising a membrane and a rim supporting the membrane around its periphery, The aforementioned film comprises a film core including a first film layer, a second film layer, and a third film layer. The first and third film layers comprise a metal silicide, and the second film layer comprises a doped metal silicide. The edging comprises a sequential stack of a portion of a planar substrate and at least a portion of at least one sacrificial layer comprising amorphous carbon, wherein the at least one sacrificial layer is adjacent to the film. Pellicle membrane assembly.

2. The pellicle film assembly according to claim 1, wherein the thickness of the at least one sacrificial layer is substantially thinner than the film.

3. The pellicle film assembly according to claim 1 or 2, wherein the sacrificial layer adjacent to the film comprises an oxide and is substantially thinner than the film.

4. A method for manufacturing a pellicle membrane assembly, A stack is formed by providing at least one sacrificial layer comprising amorphous carbon on a planar substrate, and a film is provided comprising a film core including a first film layer, a second film layer, and a third film layer in at least a portion of the stack, wherein the first and third film layers comprise metal silicide, and the second film layer comprises doped metal silicide. A method comprising at least one etching step for removing at least a portion of the substrate and one or more sacrificial layers, wherein the at least one etching step defines a border supporting the film around the periphery of the film, the border comprising a sequential stack of a portion of the planar substrate and at least a portion of the at least one sacrificial layer comprising amorphous carbon, the at least one sacrificial layer being adjacent to the film.

5. The method of claim 4, wherein the planar substrate is annealed to provide a thermal oxide layer before providing a tetraethyl orthosilicate layer.

6. The method of claim 4 or 5, wherein the final etching step is wet etching.

7. The method of claim 6, further comprising a plasma treatment step following the final etching step, wherein the plasma treatment step removes at least a portion of the amorphous carbon sacrificial layer or additional sacrificial layer.

8. The method according to any one of claims 4 to 7, wherein the planar substrate is an SOI (silicon-on-insulator) wafer.

9. The method, comprising providing the first and second sacrificial layers on the planar substrate, followed by patterning the back side of the stack, as per any one of claims 4 to 8.

10. i) A step of providing a third sacrificial layer in the form of an oxide to form a bottom oxide, ii) The step of depositing the film core layer on the surface of the stack, iii) The step of annealing the stack, iv) A step of patterning the front side of the stack, v) Providing a protective layer to protect the front side of the stack, vi) Cavity etching is performed from the back side of the stack to remove the planar substrate, the first sacrificial layer, and a portion of the second sacrificial layer to define the pellicle film assembly, The method of claim 9, further comprising the following in order.

11. The method of claim 10, further comprising removing the protective layer and peeling off the pellicle film assembly.

12. The method of claim 10 or 11, wherein the third sacrificial layer is a chemical oxide or a thermal oxide.

13. An apparatus comprising the pellicle membrane assembly according to any one of claims 1 to 3.

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