Pellicle, method of forming the same and method of manufacturing semiconductor device using the same

Abstract

A photomask protector is provided for protecting a photomask from contaminating particles during lithography. The photomask protector comprises a photomask material having a boron carbon nitride (BCN) nanostructure network. The photomask protector is attached to a photomask frame, which is mounted onto the photomask used during lithography operations.

Description

Prior Technology

[0001] In the semiconductor integrated circuit (IC) industry, technological advancements in materials and design have resulted in each generation of ICs having smaller and more complex circuitry than the previous one. Functional density (i.e., the number of interconnect devices per wafer area) has generally increased, while geometry (i.e., the smallest component (or line) that can be created using manufacturing processes) has decreased. This shrinking process typically provides benefits through increased production efficiency and reduced associated costs, but it also increases the complexity of IC processes and manufacturing.

[0002] During lithography, patterned photoresist layers are formed for various patterning processes, such as etching or ion implantation. The smallest feature size that can be patterned through this lithography process is limited by the wavelength of the projected radiation source. Existing lithography equipment uses deep ultraviolet (DUV) light, including a 248 nm KrF laser and a 193 nm ArF laser, as well as extreme ultraviolet (EUV) light at a wavelength of 13.5 nm.

[0003] In lithography, a photomask is used. A photomask consists of a substrate and a patterning layer defining the IC to be transferred onto the semiconductor substrate during the lithography process. A photomask typically includes a protective film. The protective film comprises a transparent thin film and a protective film frame, with the thin film mounted above the protective film frame. The protective film protects the photomask from falling particles and defocuses them, preventing them from creating patterned images that can cause defects when using the photomask. Existing protective films exposed to harsh lithography conditions may exhibit reduced optical performance due to exposure to temperature and light. There is still room for improvement in protective film materials with extreme ultraviolet (EUV) exposure stability and optimized mechanical and optical properties. Simple Explanation of the Diagram

[0004] The various aspects of this disclosure are most readily understood when read in conjunction with the accompanying drawings. It should be emphasized that, in accordance with industry standard practice, the features are not drawn to scale. In fact, for clarity of discussion, the dimensions of the features may be arbitrarily increased or decreased. Figure 1 is a schematic diagram of a lithography system established according to some embodiments of the present disclosure. Figure 2 is a cross-sectional view of a photomask-photomask protective film assembly according to some embodiments of the present disclosure. Figure 3 is a cross-sectional view of another photomask-photomask protective film assembly having a protective layer according to other embodiments of the present disclosure. Figure 4 is an exploded view of a photomask protective film according to some embodiments of the present disclosure. Figure 5 is a flowchart illustrating a method for forming a photomask-photomask protective film assembly according to at least one embodiment of the present disclosure. Figure 6 illustrates a flowchart of a method for manufacturing a semiconductor device according to at least one embodiment of the present disclosure. Figure 7 illustrates an example of a boron carbonitride (BCN) nanostructure according to at least one embodiment of the present disclosure. Implementation

[0005] Please understand that the following disclosure provides many different embodiments or examples to achieve different features of this application. Specific embodiments or examples of components and arrangements are described below to simplify this disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the dimensions of elements are not limited to the range or values ​​disclosed, but may depend on process conditions and / or the desired characteristics of the apparatus. Furthermore, the formation of a first feature on or above a second feature in the following description may include embodiments where the first and second features are formed in direct contact, or embodiments formed by inserting an additional feature between the first and second features, such that the first and second features may not be in direct contact. For simplicity and clarity, various features may be drawn at any different scale. In the drawings, some layers / features may be omitted for simplicity.

[0006] Furthermore, spatial relative terms, such as "below," "lower," "lower," "upper," "higher," etc., may be used herein to facilitate the description of the relationship between one element or feature shown in the figures and another element or feature. Spatial relative terms are intended to include different orientations of the device in use or operation other than those depicted in the figures. The device may be oriented in other ways (rotated 90 degrees or other orientations), and the spatial relative descriptors used herein may be interpreted accordingly. Additionally, the term "made of" may mean "comprising" or "consisting of." Moreover, in the following manufacturing processes, there may be one or more additional operations between the described operations, and the order of operations may change. In this disclosure, the phrase "at least one of A, B, and C" means any one of A, B, C, A+B, A+C, B+C, or A+B+C, and not one from A, one from B, one from C, unless otherwise stated.

[0007] In one example, this disclosure provides a durable, high-transmittance pellicle for extreme ultraviolet (EUV) lithography equipment. In some embodiments, the EUV lithography scanner uses EUV light radiation to project a pattern formed on a photomask onto a silicon wafer, which can then be etched into the wafer. In some examples, the pellicle serves to protect the photomask from contamination. For example, particles may fall onto the photomask surface. These particles may also be printed or transferred onto the wafer when the EUV lithography scanner subsequently prints or transfers the photomask pattern, causing defects in the pattern. However, a properly positioned pellicle can prevent particles from falling onto the photomask.

[0008] While pellicles reduce photomask contamination, they can also reduce the amount of extreme ultraviolet (EUV) radiation reaching the photomask. For example, if the pellicle membrane is too thick, it may absorb most of the EUV radiation before it reaches the photomask, potentially reducing the yield of EUV lithography scanners. Furthermore, existing pellicle materials are prone to mechanical deformation under typical EUV or deep ultraviolet lithography system process conditions. For instance, EUV lithography systems operate at exposure energies of 400 to 600 watts. Under these conditions, the temperature of the pellicle can reach 600 to 800 degrees Celsius, far exceeding the melting point of many materials. Therefore, traditional pellicles may require relatively frequent replacement.

[0009] This disclosure provides an example of a durable, high-transmittance photomask liner that is resistant to temperature-induced deformation and transmits a high percentage (e.g., 94% or higher) of radiation onto the photomask. In some embodiments, the photomask liner has an extreme ultraviolet (EUV) reflectance between 0.01% and 0.05%, while the deep ultraviolet (DUV) reflectance is reduced to less than 24%. In one example, the photomask liner comprises a thin film of a ternary compound containing a boron carbonitride (BCN) nanostructure network. In other examples, the BCN nanostructure network includes one or more dopants at optimized concentrations to extend the EUV transmittance and exposure lifetime of the photomask liner. In some embodiments, the BCN nanostructure network is doped with one or more dopants selected from molybdenum (Mo), oxygen (O), niobium (Nb), silicon (Si), or yttrium (Y). In some embodiments, the dopants act as grain growth controllers, contributing to exposure stability.

[0010] In other embodiments, one or more protective layers are disposed on the surface of the pellicle membrane, the material of which is selected from one or more metals, metal oxides, carbides, or nitrides. In other embodiments, additional elements of silicon, boron, carbon, nitrogen, phosphorus, or oxygen are added to the boron carbonitride (BCN) nanostructure to further control grain growth and increase exposure stability. In some embodiments, when additional elements of silicon, boron, carbon, nitrogen, phosphorus, or oxygen are added to the boron carbonitride (BCN) nanostructure, a hybrid interface is formed between the BCN nanostructure and the protective layer.

[0011] In some embodiments disclosed herein, the photomask liner comprises a network of boron carbon nitride (BCN) nanostructures selected from nanotubes, nanowires, nanofibers, nanosheets, or nanocages. The photomask liner possesses mechanical strength, is durable under deep ultraviolet and extreme ultraviolet light, and allows for improved radiation transmission. In some embodiments, the boron carbon nitride (BCN) nanostructure is amorphous, while in other embodiments it is crystalline.

[0012] Additional features may be added to the photomask cover disclosed herein. Some features described below may also be replaced or eliminated to obtain different examples. Although some examples disclosed below discuss operations performed in a specific order, these operations may also be performed in other orders without departing from the scope of this disclosure. In various views and illustrative embodiments, the same reference numerals are used to designate the same elements.

[0013] Furthermore, in other examples, the photomask protective films and methods disclosed herein can be applied to a variety of applications, including the fabrication of transistors. For example, certain examples of this disclosure may be well-suited for patterning features including lines, trenches, or vias to create relatively tight spacing between features.

[0014] Figure 1 is a simplified schematic diagram of a lithography system 100 according to an example disclosed herein. The lithography system 100 may also be referred to herein as a scanner, which is operable to perform a lithography exposure process using its respective radiation source and exposure mode.

[0015] In one example, the lithography system 100 includes an exposure light source 102, an illuminator 104, a mask stage 106, a photomask 108, a projection optics module 110, and a substrate stage 112. In some examples, the lithography system 100 includes additional components not shown in FIG. 1. In further examples, one or more of the light source 102, illuminator 104, mask stage 106, photomask 108, projection optics module 110, and substrate stage 112 are omitted from the lithography system 100 or integrated into a combined component.

[0016] In some embodiments, light source 102 is configured to emit radiation with wavelengths ranging from about 1 nanometer to 250 nanometers. In a particular example, light source 102 produces extreme ultraviolet light with wavelengths concentrated at about 13.5 nanometers; therefore, in some examples, light source 102 may also be referred to as an extreme ultraviolet light source. However, it should be understood that light source 102 is not limited to emitting extreme ultraviolet light. For example, light source 102 can be used to perform any high-intensity photon emission from excited target materials.

[0017] In some examples (e.g., when lithography system 100 is an ultraviolet lithography system), illuminator 104 includes various refractive optical elements, such as a single lens or a lens system containing multiple lenses (area plates). In another example (e.g., when lithography system 100 is an extreme ultraviolet lithography system), illuminator 104 includes various reflective optical elements, such as a single mirror or a mirror system containing multiple mirrors. Illuminator 104 can guide light from exposure light source 102 onto mask stage 106, and more specifically onto photomask 108 fixed to mask stage 106. In examples where light source 102 produces light in the extreme ultraviolet wavelength range, illuminator 104 includes reflective optical elements.

[0018] In some embodiments, the mask stage 106 is configured to hold the photomask 108. In some examples, the mask stage 106 includes an electrostatic chuck to hold the photomask 108. Because gas molecules absorb extreme ultraviolet light, the lithography system 100 for extreme ultraviolet lithography patterning is maintained in a vacuum environment to minimize extreme ultraviolet light intensity loss. Here, the terms photomask, mask, and photomask are used interchangeably. In one example, the photomask 108 is a reflective photomask.

[0019] In some embodiments of this disclosure, a pellicle 114 is placed over the photomask 108, for example, between the photomask 108 and the substrate stage 112. The pellicle 114 protects the photomask 108 from particles and can defocus the particles, preventing them from creating an image (which could cause defects on the semiconductor wafer 116 during lithography). In some embodiments of this disclosure, a boron carbon nitride (BCN) pellicle film (FIG. 2) or a boron carbon nitride (BCN) pellicle film with a protective layer is used (FIG. 3).

[0020] In some embodiments, the projection optics module 110 is configured to image the pattern of the photomask 108 onto a semiconductor wafer 116 fixed on a substrate stage 112. In one example, the projection optics module 110 includes refractive optical elements (such as those used in an ultraviolet lithography system). In another example, the projection optics module 110 includes reflective optical elements (such as those used in an extreme ultraviolet lithography system). Light guided from the photomask 108 carries an image of the pattern defined on the photomask 108 and is collected by the projection optics module 110. The illuminator 104 and the projection optics module 110 may be collectively referred to as the optical modules of the lithography system 100.

[0021] In some examples, semiconductor wafer 116 may be a bulk semiconductor wafer. In some embodiments, semiconductor wafer 116 includes a silicon wafer. In other examples, semiconductor wafer 116 includes another elemental semiconductor material, such as germanium. In some examples, semiconductor wafer 116 includes a compound semiconductor. In other examples, compound semiconductors include gallium arsenide, silicon carbide, indium arsenide, indium phosphide, other suitable materials, or combinations thereof. In still other examples, semiconductor wafer 116 includes a silicon-on-insulator (SOI) substrate. In some embodiments, the SOI substrate is fabricated using a separation by implantation of oxygen (SIMOX) process, a wafer bonding process, other suitable processes, or a combination thereof. In some examples, semiconductor wafer 116 includes an undoped substrate. However, in other examples, semiconductor substrate 116 includes a doped substrate, such as a p-type substrate or an n-type substrate.

[0022] In some examples, semiconductor wafer 116 includes various doped regions (not shown), depending on the design requirements of the semiconductor device structure. Doped regions may include, for example, p-type wells and / or n-type wells. In some examples, the doped regions are doped with p-type dopants such as boron or boron fluoride. In other examples, the doped regions are doped with n-type dopants such as phosphorus or arsenic. In some examples, some doped regions are p-type doped while others are n-type doped.

[0023] In some embodiments, an interconnect structure is formed on a semiconductor wafer 116. The interconnect structure includes multiple interlayer dielectric layers, including dielectric layers. In some embodiments, the interconnect structure includes multiple conductive features formed in the interlayer dielectric layers. In some embodiments, the conductive features include conductive lines, conductive vias, and / or conductive contacts.

[0024] In some examples, various device elements are formed in semiconductor wafer 116. Examples of various device elements include transistors (e.g., metal-oxide-semiconductor field-effect transistors (MOSFETs), complementary metal-oxide-semiconductor (CMOS) transistors, bipolar junction transistors (BJTs), high-voltage transistors, high-frequency transistors, p-channel and / or n-channel field-effect transistors (PFETs and / or NFETs), diodes, or other suitable components. In some embodiments, various processes are used to form the various device elements, including deposition, etching, placement, lithography, annealing, and / or other suitable processes.

[0025] In some embodiments, device elements are interconnected via interconnect structures on semiconductor wafer 116 to form an IC device. In some embodiments, the IC device includes logic devices, memory devices (e.g., static random access memory (SRAM) devices), radio frequency (RF) devices, input / output (I / O) devices, system-on-chip (SoC) devices, image sensor devices, other suitable devices, or combinations thereof.

[0026] In some examples, the semiconductor wafer 116 is coated with a photoresist layer that is sensitive to active radiation, such as deep ultraviolet or extreme ultraviolet light. In other embodiments, various elements described above are integrated and operable to perform lithography processes.

[0027] Figure 2 shows a cross-sectional view of a photomask-pellicle assembly 205 for lithography according to some embodiments. The photomask-pellicle assembly 205 includes a photomask 108 and a photomask pellicle 114. An exemplary photomask 108 is a reflective photomask for extreme ultraviolet (EUV) lithography, including a substrate 202, alternating reflective layers 204, spacer layers 206, a capping layer 208, an EUV absorbing layer 210 (patterned to define patterned areas or surfaces of the photomask), an anti-reflective coating (ARC) 212, and a conductive back-side layer 214. The exemplary photomask 108 is merely a non-limiting example. The photomask pellicle 114 disclosed herein can be used with substantially any type of reflective or transmissive photomask. As another example (not shown), the photomask 108 is a transmissive photomask, in which case the substrate is transparent to light of the wavelengths used to perform lithography. Generally, reflective or transmissive photomasks include a substrate (e.g., substrate 202) and a photomask pattern (e.g., absorption layer 210) disposed on the substrate 202. As shown in the embodiment of FIG2, the pellicle 114 includes a mounting frame 222, an adhesive layer 224, and a pellicle membrane 230. In some embodiments, the photomask-pellicle membrane assembly 205 is used for extreme ultraviolet wavelengths, for example from about 10 nanometers to about 124 nanometers, including about 13.5 nanometers.

[0028] In some embodiments, substrate 202 is made of a low thermal expansion material (LTEM), such as quartz or titanium dioxide silicate glass. In some examples, substrate 202 comprises a transparent substrate, such as substantially defect-free fused silica, borosilicate glass, soda-lime glass, calcium fluoride, LTEM, ultra-low thermal expansion material, or other suitable material. Substrate 202 helps reduce or prevent photomask warping due to energy absorption and the resulting heating. Reflective layer 204 and spacer layer 206 cooperate to form a Bragg reflector for reflecting extreme ultraviolet light. In some embodiments, reflective layer 204 comprises molybdenum (Mo), and spacer layer 206 comprises silicon (Si). Cap layer 208 is used to protect the reflector formed by reflective layer 204 and spacer layer 206, for example, from oxidation and etching. In some embodiments, cap layer 208 comprises ruthenium (Ru). Extreme ultraviolet absorbing layer 210 absorbs extreme ultraviolet wavelengths and is patterned in a desired pattern. In some embodiments, extreme ultraviolet absorbing layer 210 comprises boron nitride tantalum. An anti-reflective coating (ARC) 212 further reduces reflections from the extreme ultraviolet (EUV) absorbing layer. In some embodiments, the anti-reflective coating 212 comprises boron nitride tantalum. A conductive backside layer 214 allows the exemplary photomask to be mounted on an electrostatic chuck and regulates the temperature of the mounting substrate 202. In some embodiments, the conductive backside layer 214 comprises chromium nitride.

[0029] The photomask protector 114 includes a mounting frame 222 that supports the photomask protector 230 at a sufficient height such that the photomask protector 230 is located outside the focal plane of the lithography, for example, a few millimeters (mm) above the photomask 108 in some non-limiting example embodiments. In some embodiments, the mounting frame 222 itself is made of a suitable material such as anodized aluminum oxide, stainless steel, plastic, silicon (Si), titanium, silicon dioxide, aluminum oxide (Al2O3), or titanium dioxide (TiO2). In some examples, suitable processes for forming the mounting frame 222 include machining processes, sintering processes, photochemical etching processes, other suitable processes, or combinations thereof.

[0030] In other embodiments, vent holes (not shown) are provided in the mounting frame 222 to balance the pressure on both sides of the photomask liner 230. In some examples, the venting structure includes one or more holes formed on the side of the mounting frame 222. In some embodiments, these holes can be of any shape, including circular holes, rectangular holes, slit holes, other shapes, or any combination thereof. In some embodiments, these holes allow ambient airflow in the lithography system to pass through a portion of the photomask-photomask liner assembly 205. In some examples, these holes may include filters to minimize the passage of external particles through the vent holes. In some examples, the vent holes may be formed using a photochemical etching process, other applicable processes, or a combination thereof.

[0031] In some embodiments, an adhesive layer 224 is used to secure the photomask cover 230 to the mounting frame 222. Suitable adhesives may include silicone, epoxy resin, thermoplastic elastomer rubber, acrylic polymer, acrylic copolymer, or combinations thereof. In some embodiments, the adhesive layer 224 has a crystalline and / or amorphous structure. In some embodiments, the adhesive layer 224 has a glass transition temperature (Tg) higher than the highest operating temperature of the lithography system to prevent the adhesive from exceeding the Tg during system operation.

[0032] In some examples, the adhesive layer 224 includes a heat-dissipating filler. The heat-dissipating filler may include, for example, aluminum nitride, boron nitride, aluminum oxide, magnesium oxide, silicon oxide, graphite, metal powder, ceramic powder, other suitable materials, or combinations thereof. In some examples, extreme ultraviolet (EUV) lithography processes may involve an EUV beam penetrating the photomask 230, causing the temperature of the photomask 230 to rise. The heat-dissipating filler helps dissipate the heat from the photomask 230 through the adhesive layer 224 to the mounting frame 222, the photomask 108, and the EUV lithography scanner. Therefore, in some embodiments, the maximum temperature of the photomask 230 is reduced during EUV lithography processes using the photomask 230 according to embodiments of this disclosure, thereby reducing the likelihood of the photomask 230 cracking.

[0033] In some examples, a surface treatment is performed on the mounting frame 222 to enhance the adhesion between the mounting frame 222 and the adhesive layer 224. In some examples, the surface treatment includes an oxygen plasma process, other applicable processes, or a combination thereof. However, in other examples, no surface treatment is performed on the mounting frame 222.

[0034] In the embodiment of Figure 3, a protective layer 240 is applied to the outer surface of the photomask liner 230. In some embodiments, the protective layer 240 is applied via physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced CVD, atomic layer deposition (ALD), plasma-enhanced ALD, electron beam evaporation, electroless deposition, electrodeposition, or ion beam deposition (IBD). In some embodiments, it is desirable that the protective layer 240 aligns with the exposed surface of the photomask liner 230, such that pores present in the photomask liner 230 remain and are not filled by the protective layer 240. Therefore, in some embodiments, the photomask liner 230 is a porous thin film or membrane. In some embodiments, when applied, the protective layer 240 protects the photomask liner 230 from damage that may be caused by heat and hydrogen plasma generated during extreme ultraviolet (EUV) exposure. When the protective layer 240 is applied to the photomask liner 230, there is a synergistic effect in resisting hydrogen damage.

[0035] In some embodiments, the material used for protective layer 240 has a low refractive index, i.e., as close to 1 as possible when measured at a wavelength of 13.5 nanometers. In some embodiments, the material used for protective layer 240 has a low extinction coefficient at a wavelength of 13.5 nanometers. The extinction coefficient measures how easily a material can penetrate at that wavelength. In some embodiments, the material used for protective layer 240 has a transmittance (T%) greater than 90%, greater than 92%, greater than 94%, or greater than 95% when measured at an extreme ultraviolet wavelength of 13.5 nanometers, when the thickness is between 0.5 nanometers and 10 nanometers. This reduces the absorption of extreme ultraviolet light by protective layer 240 (allowing for further downstream processes) while protecting photomask liner 230.

[0036] In some embodiments, the material of the protective layer 240 is selected from SiOx, SiNx, SiCx, and their oxynitrides or oxycarbides. In other embodiments, the material of the protective layer 240 includes a metal, a metal oxide, a metal carbide, a metal nitride, or a metal oxynitride, wherein the metal is selected from one or more of ruthenium, niobium, aluminum, or molybdenum. In other embodiments, the material of the protective layer 240 is selected from one or more of boron, boron nitride, B4C, B2O3, B6Si, silicon nitride, Si3N4, SiN2, silicon carbide, zirconium silicate, SiCxNy, niobium, niobium nitride, niobium silicate, niobium silicate, Nb2O5, NbTixNy, niobium carbide, Nb5Si3, ZrNx, ZrYxOy, zirconium fluoride, ZrF4. ZrSi2, yttrium nitride, Y2O3, yttrium fluoride, molybdenum, MO2N, molybdenum silicon, MoSi2, molybdenum silicon nitride, MoC2, molybdenum carbide, MoS2, molybdenum nitride, ruthenium, ruthenium-niobium, ruthenium silicon nitride, RuO2, titanium nitride, TiCxNy, HfO2, HfNx, HfF4, vanadium nitride, rhodium, platinum, palladium, tungsten, chromium, nickel, iron, cobalt, silver, gold, zirconium, yttrium, or composites thereof. In some embodiments, the thickness of the protective layer 240 is from about 0.5 nanometers (nm) to about 10 nanometers. In some embodiments, the thickness of the protective layer 240 is between about 1 nanometer and about 8 nanometers.

[0037] In some embodiments, a mixing interface (not shown) appears between the photomask liner 230 and the protective layer 240 when one or more additional elements selected from silicon, boron, carbon, nitrogen, and phosphorus are present in the boron carbon nitride (BCN) nanostructure. In some embodiments, the thickness of the mixing interface is between about 1 nanometer and about 5 nanometers. The mixing interface provides additional exposure stability. In some embodiments, the protective layer 240 is present in the form of a continuous film, nanocrystals, nanoparticles, nanosheets, or a combination thereof. In some embodiments, the coating consists of multiple layers of the materials listed above, each layer having any of the forms listed above.

[0038] Figure 7 shows an example of a boron carbon nitride (BCN) nanostructure 700. The boron carbon nitride (BCN) nanostructure 700 is shown as a nanotube structure, consisting of cylindrical molecules formed by a sheet-like structure composed of a monolayer of carbon atoms 701, nitrogen atoms 703, and boron atoms 705 rolled up.

[0039] Figure 4 is an exploded view of a photomask liner 114 according to some embodiments of the present disclosure. In some embodiments, the photomask liner 230 is a single-layer or multi-layer thin film formed of a boron carbon nitride (BCN) nanostructure network. In some embodiments, the atomic percentage of carbon in the boron carbon nitride (BCN) nanostructure is optimized to increase the strength of the boron carbon nitride (BCN) nanostructure. In some examples, the boron carbon nitride (BCN) nanostructure includes carbon with an atomic percentage ranging from about 1.2 to 3.6. Examples of boron carbon nitride (BCN) nanostructures include BC1.2N, BC1.9N1.1, BC2.4N1.3, BC2.8N1.4, and BC3.6N1.7.

[0040] In the embodiment of FIG4, the photomask liner 230 includes a first boron carbonitride (BCN) nanostructure 231 and a second boron carbonitride (BCN) nanostructure 231'. The two layers 231 and 231' of the photomask liner 230 are in contact with each other through van der Waals forces, and the boron carbonitride (BCN) nanostructures in each layer 231 and 231' do not entangle with the other layer. In some embodiments, a protective layer 240 is applied to the outer surface of the photomask liner 230. In other embodiments, a protective layer 240 is applied to the inner surface of the photomask liner 230. In the embodiment of FIG4, the protective layer 240 and the photomask liner 230 are enclosed within a frame 232. In some embodiments, the frame 232 is fixed to the mounting frame 222 through an adhesive layer 224 (FIG. 3). The photomask liner 114 is then fixedly mounted on the photomask 108. In some embodiments, the photomask protective film 114 is fixed to the photomask 108 with an adhesive or the like.

[0041] In some embodiments disclosed herein, the use of boron carbonitride (BCN) nanostructures in the photomask liner 230 provides a thin film exhibiting effective or advantageous mechanical and optical properties when used during extreme ultraviolet lithography. Other useful physical properties include high-temperature resistance, the ability to maintain a flat, wrinkle-free morphology during photomask preparation and use, and resistance to reactive chemicals, particularly hydrogen radical degradation.

[0042] In some embodiments, the photomask liner 230, as described, comprising a boron carbon nitride (BCN) nanostructure, is made both very thin and lightweight. In some embodiments, the photomask liner 230 is a thin film containing a network of boron carbon nitride (BCN) nanostructures. In some embodiments, the boron carbon nitride (BCN) nanostructures comprise a network of nanotubes, nanowires, nanofibers, nanosheets, or nanocages dispersed within the photomask liner 230, and are interconnected or interlaced to form a thin but cohesive thin film. In some embodiments, the boron carbon nitride (BCN) nanostructures comprise various molecular and structural arrangements of boron carbon nitride (BCN). In some embodiments, the boron carbon nitride (BCN) nanostructures comprise morphologies arranged in periodic nanocrystalline, amorphous, or polycrystalline forms.

[0043] In some embodiments, the boron carbon nitride (BCN) nanostructure network constituting the photomask liner 230 has sufficient structure density to maximize extreme ultraviolet (EUV) radiation transmission while minimizing particle penetration through the photomask liner 230. For example, while a looser structure density may allow greater EUV radiation transmission, it may also allow particles to fall onto the photomask 108. In some embodiments, the photomask liner 230 comprising the boron carbon nitride (BCN) nanostructure is formed through a roll-to-roll process, other suitable processes, or any combination thereof.

[0044] In some embodiments, the photomask liner 230 is a single-layer structure. In other embodiments, the photomask liner 230 is a multilayer structure (FIG. 4). In some embodiments, the layers of the multilayer structure may be made of the same material, while in other embodiments, the layers of the multilayer structure may be made of different materials selected for a specific purpose and arranged in a desired order. For example, in some embodiments, the photomask liner may comprise one or more boron carbonitride (BCN) nanostructure layers and one or more carbon nanotube (CNT) layers. In some embodiments, the thickness of the photomask liner 230 is between about 5 nanometers and about 15 nanometers. In other embodiments, the thickness of the photomask liner 230 is between about 10 nanometers and about 12 nanometers. In some embodiments, the photomask liner comprises BCN, BC2N, BC3N, BC4N, BC5N, or BC6N nanostructures.

[0045] In some embodiments disclosed herein, the boron carbonitride (BCN) nanostructure exists in the form of nanotubes, nanowires, nanofibers, nanosheets, or nanocages. In some embodiments, the initial nanotube membrane is formed from nanotube bundles. In some embodiments, this is done by arranging the nanotube bundles adjacent to each other. Without being bound by any particular theory, it is generally accepted that nanotube bundles are bound together by sufficiently strong van der Waals forces to form the initial nanotube membrane. In some embodiments, the initial nanotube membrane is annealed at a temperature of approximately 1000°C to approximately 2000°C. In some embodiments, the initial nanotube membrane is treated to reduce its thickness and obtain a photomask protective film 230. In some embodiments, the initial nanotube membrane is compressed or immersed in a solution to obtain the desired thickness.

[0046] In some embodiments, boron carbonitride (BCN) nanostructure networks are formed using several different fabrication processes. These processes include, for example, chemical vapor deposition (CVD), floating catalyst CVD, plasma-enhanced CVD, and electrophoretic deposition; dispersion in solution followed by concentration through solvent removal; vacuum filtration; and so on. In some embodiments, BCN nanotubes are formed directly from spinning nanotubes within a floating catalyst CVD system. The direct spinning process begins by providing a reactor vessel. In some examples, the reactor vessel is equipped with a heat source to ensure a specified temperature within the vessel. In some embodiments, the BCN nanotubes are then grown in the vessel to form an aerogel, which can then be spun into fibers.

[0047] In some embodiments, the photomask 230 has a Young's coefficient between about 1.18 TPa and about 1.33 TPa; a maximum tensile strength between about 30 GPa and about 100 GPa; a thermal conductivity between about 3,000 W / m K and about 4,000 W / m K; and is stable at about 800 degrees Celsius in air.

[0048] In some embodiments, the nanostructures of the photomask 230 are randomly oriented or oriented in a desired direction. In some embodiments, all the nanostructures of the photomask 230 are randomly oriented. In some embodiments, all the nanostructures of the photomask 230 are oriented. In these embodiments, the oriented nanostructures are aligned relative to each other at an angle (e.g., 0 to 180 degrees).

[0049] In some embodiments, the boron carbon nitride (BCN) nanostructure network includes one or more dopants. In some embodiments, the dopant concentration in the boron carbon nitride (BCN) nanostructure network is about 0 to about 15 atomic percent (atomic %, at.%). In other embodiments, the dopant concentration in the boron carbon nitride (BCN) nanostructure network is between about 7 at.% and about 10 at.%. Dopant concentrations above 15 at.% can reduce the transmittance of the photomask and decrease its mechanical strength. In some embodiments, the boron carbon nitride (BCN) nanostructure is doped with one or more dopants selected from molybdenum, oxygen, niobium, silicon, or yttrium. In some embodiments, the dopant material is selected from one or more silicon nitride (SiN), molybdenum disilicide (MoSi2), molybdenum silicide (Mo5Si3), and Mo3Si (molybdenum trisilicide). In some embodiments, the dopant acts as a grain growth controller to aid exposure stability. In some embodiments, the dopant concentration in the boron carbon nitride (BCN) nanostructure enhances the exposure durability of the photomask coating 230. In other embodiments, the boron carbon nitride (BCN) nanostructure includes additional elements selected from silicon, boron, carbon, nitrogen, phosphorus, or oxygen, and alloys or mixtures thereof, to optimize optical and mechanical properties. In still other embodiments, the nanostructure includes a low extinction coefficient (low K) material to achieve exposure stability. In some embodiments, the low extinction coefficient (low K) material has an extinction coefficient of about 0.01 to 0 and can be tuned by the film composition and intrinsic optical constant. Examples of low extinction coefficient (low K) materials include materials containing one or more molybdenum, niobium, zirconium, yttrium, calcium, sulfur, phosphorus, potassium, strontium, rubidium, silicon, and chlorine. In some embodiments, the low extinction coefficient (low K) material is manufactured from precursors, targets, or reactive synthesis processes, including but not limited to PVD, CVD, ALD, and ion beam.

[0050] In some embodiments, boron carbonitride (BCN) nanostructures undergo thermal and mechanical stresses during extreme ultraviolet (EUV) lithography. These stresses can alter grain growth and lead to coarsening of gains, potentially reducing the material strength and hardness of the BCN nanostructure. Furthermore, cracks can occur in the BCN nanostructure due to grain boundary migration, stress concentration, and the presence of defects. The high surface energy and grain boundary presence of BCN nanostructures make them more susceptible to cracking. In some embodiments disclosed herein, dopant concentration controls the grain size in the BCN nanostructure and helps reduce cracking. In other embodiments, the dopant is provided at the grain boundaries of the BCN nanostructure to suppress oxidation and reduce the loss of nitrogen or carbon atoms at the grain boundaries.

[0051] In some embodiments disclosed herein, the dopant concentration is controlled, and the penetration of the dopant material into the boron carbonitride (BCN) nanostructure of the photomask liner 230 is limited. In some embodiments, mixing occurs between the dopant material and the boron carbonitride (BCN) nanostructure. In some examples, the dopant material penetrates to a depth of about 0 to about 3 nanometers into the boron carbonitride (BCN) nanostructure grains.

[0052] Figure 5 is a flowchart of a method for forming a photomask-photomask cover assembly 205. The method includes step 501, forming a photomask cover 230 comprising a boron carbonitride (BCN) nanostructure network. The method includes step 503, enclosing the photomask cover 230 within a frame 232. The method includes step 505, attaching the frame 232 having the photomask cover 230 to a photomask cover mounting frame 222. The method further includes step 507, covering a photomask 108, wherein the photomask 108 includes a patterned region 210, with the photomask cover mounting frame 222.

[0053] Figure 6 is a flowchart of a method for manufacturing a semiconductor device. The method includes step 601, providing a photomask 114 comprising a photomask material 230 fixed to a photomask mounting frame 222. The photomask material comprises a boron carbon nitride (BCN) nanostructure network. The method includes step 603, mounting the photomask 114 onto a photomask 108, wherein the photomask 108 includes a patterned surface 210. The method includes step 605, loading the photomask 108 with the photomask 114 mounted into a lithography system 100. The method includes step 607, loading a semiconductor wafer 116 onto a substrate stage 112 of the lithography system 100. The method includes step 609, performing a lithography process to transfer the pattern of the patterned surface of the photomask 108 onto the semiconductor wafer 116.

[0054] Therefore, the examples disclosed herein provide a robust, high-transmittance boron carbonitride (BCN) nanostructure photomask liner that resists deformation caused by temperature and pressure and transmits a high percentage (e.g., greater than 94%) of radiation onto the photomask. The photomask liner disclosed herein may be particularly suitable for use in ultraviolet lithography systems, and even more so in extreme ultraviolet lithography systems.

[0055] In one example, this disclosure provides a method for forming a photomask-photomask cover assembly. The method includes forming a photomask cover comprising a boron carbonitride (BCN) nanostructure network. The method includes enclosing the photomask cover within a frame. The method includes attaching the frame having the photomask cover to a photomask cover mounting frame. The method includes covering the photomask with the photomask cover mounting frame, wherein the photomask includes patterned areas.

[0056] In some embodiments, the boron carbon nitride (BCN) nanostructure network includes nanotubes, nanowires, nanofibers, nanosheets, or nanocages. In some embodiments, the boron carbon nitride (BCN) nanostructure network contains one or more dopants selected from molybdenum (Mo), oxygen (O), niobium (Nb), silicon (Si), or yttrium (Y). In some embodiments, the concentration of the one or more dopants is 15 atomic percent (at.%) or less. In some embodiments, the concentration of the one or more dopants is 7 at.% to 10 at.%. In other embodiments, the thickness of the photomask protective film is 5 nanometers (nm) to 15 nm. In some embodiments, the method includes forming a protective layer on the photomask protective film. In some embodiments, the protective layer contains one or more selected from metals, metal oxides, metal carbides, metal nitrides, or metal oxynitrides. In some embodiments, the thickness of the protective layer is 0.5 nm to 10 nm. In other embodiments, the photomask includes a substrate, alternating reflective layers, spacer layers, and capping layers.

[0057] In another example, a method for manufacturing a semiconductor device is provided. The method includes providing a photomask containing a photomask material fixed to a photomask mounting frame. The photomask material includes a boron carbon nitride (BCN) nanostructure network. The method includes mounting the photomask onto a photomask, wherein the photomask includes a patterned surface. The method includes loading a photomask having the photomask mounted thereon into a lithography system. The method includes loading a semiconductor wafer onto a substrate stage of the lithography system. The method includes performing a lithography exposure process to transfer a pattern of the patterned surface of the photomask onto the semiconductor wafer.

[0058] In some embodiments, the lithography process generates light selected from deep ultraviolet or extreme ultraviolet light. In some embodiments, the boron carbon nitride (BCN) nanostructure network comprises one or more dopants selected from molybdenum (Mo), oxygen (O), niobium (Nb), silicon (Si), or yttrium (Y). In some embodiments, the concentration of the one or more dopants is 15 atomic percent (at.%) or less. In other embodiments, a protective layer is formed on the photomask. In some embodiments, the protective layer is selected from one or more SiOx, SiNx, SiCx, and their oxynitrides or oxycarbides.

[0059] In another example, a photomask protector for semiconductor lithography is provided. The photomask protector includes a photomask protector comprising at least one porous thin film. The at least one porous thin film comprises a boron carbon nitride (BCN) nanostructure network. A border is attached to the photomask protector along a peripheral region of the photomask protector. A mounting frame is attached to the border.

[0060] In some embodiments, a protective layer is disposed on a photomask protective film. In some embodiments, the boron carbon nitride (BCN) nanostructure network comprises one or more dopants selected from molybdenum (Mo), oxygen (O), niobium (Nb), silicon (Si), or yttrium (Y). In other embodiments, the concentration of one or more dopants is 15 atomic percent (at.%) or less.

[0061] The foregoing outlines the features of several embodiments to enable those skilled in the art to better understand the various aspects of this disclosure. Those skilled in the art should understand that they can use this disclosure as a basis for designing or modifying other processes and structures to perform the same purpose and / or achieve the same advantages of the embodiments described herein. Those skilled in the art should also recognize that such equivalent structures do not depart from the spirit and scope of this disclosure, and they can make various changes, substitutions, and modifications without departing from the spirit and scope of this disclosure.

[0062] 100: Microfilm System 102: Light source 104:Illuminator 106: Shielding Platform 108: Light Mask 110: Projection Optical Module 112:Substrate table 114: Photomask Protective Film 116: Semiconductor wafers, semiconductor substrates 202:Substrate 204: Reflective layer 205: Photomask - Photomask Protective Film Assembly 206: Spacing layer 208: Cap layer 210: Extreme ultraviolet absorption layer, patterned area, patterned surface 212: Anti-reflective coating 214: Conductive backside layer 222: Installation Frame 224: Adhesive layer 230: Photomask Protective Film 231, 231', 700: Boron carbon nitride nanostructures 232: Border 240: Protective layer 501, 503, 505, 507, 601, 603, 605, 607, 609: Steps 701: Carbon atom 703: Nitrogen atom 705: Boron atom

Claims

1. A method for forming a photomask-photomask protective film assembly, comprising: A photomask protective film comprising a boron carbon nitride (BCN) nanostructure network is formed, wherein the boron carbon nitride nanostructure network comprises hollow cylindrical molecules formed by a sheet-like structure composed of a single layer of carbon atoms, nitrogen atoms, and boron atoms rolled up; the photomask protective film is enclosed within a frame; the frame having the photomask protective film is attached to a photomask protective film mounting frame; And cover the photomask with the photomask protective film mounting frame, wherein the photomask includes a patterned area.

2. The method of claim 1, wherein the photomask further comprises a substrate, alternating reflective layers, spacer layers, and capping layers.

3. The method of claim 1, wherein the boron carbon nitride nanostructure network comprises one or more dopants selected from molybdenum (Mo), oxygen (O), niobium (Nb), silicon (Si) or yttrium (Y).

4. The method as described in claim 3, wherein the concentration of the one or more dopants is 15 atomic percent (at.%) or lower.

5. The method of claim 4, wherein the concentration of said one or more dopants is from 7 atomic percent (at.%) to 10 atomic percent (at.%).

6. The method of claim 1, wherein the boron carbonitride nanostructure network further comprises one or more of Si, B, C, N, P and O, and alloys thereof.

7. The method as described in claim 1, further comprising: A protective layer is formed on top of the photomask film.

8. A method for manufacturing a semiconductor device, comprising: A photomask protector is provided, comprising a photomask protector fixed on a photomask protector mounting frame, wherein the photomask protector comprises a boron carbon nitride nanostructure network, wherein the boron carbon nitride nanostructure network comprises hollow cylindrical molecules formed by a sheet-like structure of monolayer carbon atoms, nitrogen atoms, and boron atoms rolled up; the photomask protector is mounted onto a photomask, wherein the photomask comprises a patterned surface; the photomask with the photomask protector mounted is loaded into a lithography system; a semiconductor wafer is loaded onto a substrate stage of the lithography system; and a lithography exposure process is performed to transfer the pattern of the patterned surface of the photomask onto the semiconductor wafer.

9. The method of claim 8, wherein the lithography process produces light selected from deep ultraviolet or extreme ultraviolet light.

10. A photomask protective film, comprising: A photomask protector includes at least one porous film comprising a boron carbon nitride nanostructure network, wherein the boron carbon nitride nanostructure network comprises hollow cylindrical molecules formed by a sheet-like structure of monolayer carbon atoms, nitrogen atoms, and boron atoms rolled up; a frame attached to the photomask protector along a peripheral region of the photomask protector; and a mounting frame attached to the frame.

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