Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F1/00—Originals for photomechanical production of textured or patterned surfaces, e.g., masks, photo-masks, reticles; Mask blanks or pellicles therefor; Containers specially adapted therefor; Preparation thereof
  • G03F1/62—Pellicles, e.g. pellicle assemblies, e.g. having membrane on support frame; Preparation thereof
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70008—Production of exposure light, i.e. light sources
  • G03F7/70033—Production of exposure light, i.e. light sources by plasma extreme ultraviolet [EUV] sources
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
  • G03F7/70983—Optical system protection, e.g. pellicles or removable covers for protection of mask
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P50/00—Etching of wafers, substrates or parts of devices
  • H10P50/69—Etching of wafers, substrates or parts of devices using masks for semiconductor materials
  • H10P50/691—Etching of wafers, substrates or parts of devices using masks for semiconductor materials for Group V materials or Group III-V materials

Definitions

• This disclosure relates to an EUV-transmitting film, a pellicle, and an exposure method.
• Patent Document 1 Japanese Patent No. 68588157 discloses a pellicle membrane having a core layer containing a material that is substantially transparent to EUV radiation, such as (poly)Si, and a cap layer containing a material that absorbs IR radiation.
• Patent Document 2 JP 2020-98227 A discloses a pellicle film that is stretched over one end surface of a pellicle frame, and that has a main layer of single-crystal Si and graphene on one or both sides of the main layer. It is said that the presence of graphene in the main layer prevents damage to the pellicle film during pellicle fabrication and ensures sufficient mechanical strength.
• Patent No. 6858817 Japanese Patent Application Laid-Open No. 2020-98227
• the core materials used in pellicle films which have high EUV transmittance, as mentioned above, form a natural oxide film of several nanometers thick on their surface in the atmosphere.
• This oxide film absorbs EUV light, reducing the EUV transmittance of the pellicle film.
• Be in particular, is a material with high EUV transmittance, but it is said that a natural oxide film of 2 to 3 nm thick forms on its surface, resulting in a significant transmittance loss of 6 to 9%.
• the process of producing pellicle films sometimes involves treatment with gases other than the atmosphere, such as fluorine or chlorine, or with acid or alkaline solutions, which can cause a side reaction film to form on the surface of the core material, which can reduce EUV transmittance. Therefore, it is desirable to form a protective layer on the surface of the core material to suppress the formation of these films.
• gases other than the atmosphere such as fluorine or chlorine
• acid or alkaline solutions which can cause a side reaction film to form on the surface of the core material, which can reduce EUV transmittance. Therefore, it is desirable to form a protective layer on the surface of the core material to suppress the formation of these films.
• a reaction-suppressing protective layer to the surface of core materials such as Si or Be can prevent a significant decrease in the EUV transmittance of the pellicle film
• such protective layers still have a lower EUV transmittance than the pure core material, leading to a decrease in the EUV transmittance of the pellicle film as a whole.
• Ru can be used as a protective layer for Be core material, but when considering a pellicle film with a three-layer structure (Ru/Be/Ru) in which 1-2 nm of Ru is provided on the front and back surfaces of the Be core material, the Ru protective layer causes a loss of EUV transmittance of approximately 3-6%, significantly reducing the performance of the pellicle film.
• the inventors have now discovered that by adopting a three-layer structure of nitride layer/metal beryllium layer/nitride layer, it is possible to provide an EUV transmitting film that exhibits high EUV transmittance.
• a metallic beryllium layer having a first surface and a second surface; a first nitride layer covering a first surface of the beryllium layer and including at least one selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride; a second nitride layer covering a second surface of the beryllium layer and including at least one selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride;
• An EUV transmitting film having a three-layer structure consisting of: The EUV transmitting film has an EUV transmittance of 88% or more at a wavelength of 13.5 nm.
• Aspect 5 a substrate having a first surface and a second surface and a central cavity; an amorphous carbon layer covering a first surface of the substrate; an EUV transmitting film according to any one of Aspects 1 to 4, which covers a surface of the amorphous carbon layer opposite to the substrate and is exposed as a free-standing film constituting a bottom surface of the cavity at the same height as the surface of the amorphous carbon layer;
• a pellicle comprising: [Aspect 6] 6. The pellicle of claim 5, wherein the amorphous carbon layer has a thickness of 1 to 15 nm. [Aspect 7] 7. The pellicle according to claim 5, wherein the substrate is a Si substrate. [Aspect 8] Aspect 8.
• FIG. 1 shows a schematic cross-sectional view of an EUV transmission film 10 according to one embodiment of the present invention.
• the EUV transmission film 10 is a three-layer film consisting of a metal beryllium layer 12, a first nitride layer 14a, and a second nitride layer 14b.
• the metal beryllium layer 12 has a first surface 12a and a second surface 12b.
• the first nitride layer 14a is a layer covering the first surface 12a of the metal beryllium layer 12 and containing at least one element selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride.
• the second nitride layer 14b is a layer covering the second surface 12b of the metal beryllium layer 12 and containing at least one element selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride.
• the EUV transmission film 10 has an EUV transmittance of 88% or more at a wavelength of 13.5 nm. In this way, by adopting a three-layer structure of first nitride layer 14a/metallic beryllium layer 12/second nitride layer 14b, it is possible to provide an EUV transmitting film 10 that exhibits high EUV transmittance.
• core materials with high EUV transmittance may form a natural oxide film several nanometers thick on their surface in the atmosphere.
• the process of manufacturing a pellicle film may involve treatment with gases other than the atmosphere, such as fluorine or chlorine, or with acid or alkaline solutions, which can result in the formation of a side reaction film on the surface of the core material.
• gases other than the atmosphere such as fluorine or chlorine
• acid or alkaline solutions which can result in the formation of a side reaction film on the surface of the core material.
• applying a reaction-inhibiting protective layer to the surface of the core material leads to a decrease in the EUV transmittance of the pellicle film as a whole.
• an amorphous carbon layer on both sides of the EUV-transmitting film as a protective film that can be removed by contacting the film with hydrogen plasma and/or hydrogen radicals, or oxygen plasma and/or oxygen radicals.
• the aforementioned natural oxide film and side reaction film are formed on the pellicle film during the process from when it is manufactured to when it is loaded into the EUV exposure device and subjected to the exposure process.
• providing an amorphous carbon layer as a protective layer on both sides of the EUV-transmitting film 10 can prevent the formation of the above-mentioned film.
• the amorphous carbon layer is effective in protecting the EUV-transmitting film 10 from various chemicals (e.g., highly reactive fluorine-based etchants) used in the pellicle film fabrication process (e.g., the self-supporting film fabrication step). Furthermore, if the amorphous carbon layer were provided directly on the metal beryllium layer 12, the amorphous carbon and the metal beryllium might react to form beryllium carbide.
• various chemicals e.g., highly reactive fluorine-based etchants
• the EUV transmitting film 10 thus obtained has a three-layer structure consisting of the metal beryllium layer 12, the first nitride layer 14a, and the second nitride layer 14b, and because it no longer has a protective layer (amorphous carbon layer), it is possible to avoid a decrease in EUV transmittance due to the protective layer.
• the EUV transmitting film 10 can maximize the high transmittance inherent in the three-layer structure consisting of the metal beryllium layer 12, the first nitride layer 14a, and the second nitride layer 14b, i.e., it can exhibit high EUV transmittance during exposure.
• the EUV transmitting film 10 has high EUV transmittance.
• the EUV transmitting film 10 has an EUV transmittance at a wavelength of 13.5 nm of 88% or more, preferably 92% or more, more preferably 93% or more, even more preferably 94% or more, particularly preferably 95% or more, and most preferably 96% or more.
• the metal beryllium layer 12 is a layer containing metal beryllium as its main component.
• the "main component" of the metal beryllium layer 12 refers to a component that accounts for 50 mol % or more of the metal beryllium layer 12, preferably 70 mol % or more, more preferably 80 mol % or more, and even more preferably 90 mol % or more.
• the metal beryllium layer 12 may also contain impurities in addition to the metal beryllium as its main component. Therefore, the metal beryllium layer 12 may consist of metal beryllium and unavoidable impurities.
• the thickness of the metal beryllium layer 12 is preferably 5 to 25 nm, more preferably 7 to 20 nm, and even more preferably 9 to 15 nm.
• Each of the first nitride layer 14a and the second nitride layer 14b contains at least one nitride selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride. Silicon nitride is particularly preferred. The advantages of providing the first nitride layer 14a and the second nitride layer 14b on both sides of the metal beryllium layer 12 are as described above.
• the terms "silicon nitride,”"berylliumnitride,” “ boron nitride,” and “zirconium nitride” refer to comprehensive compositions that include not only stoichiometric compositions such as Si3N4 , Be3N2 , BN, and ZrN, but also non-stoichiometric compositions such as Si3N4 -x (where 0 ⁇ x ⁇ 4), Be3N2 - x (where 0 ⁇ x ⁇ 2), BNx (where 0 ⁇ x ⁇ 1), and ZrNx (where 0 ⁇ x ⁇ 1).
• the thickness of each of the first nitride layer 14a and the second nitride layer 14b is preferably 1 to 5 nm, and more preferably 1 to 3 nm.
• the thickness of the EUV transmitting film 10 is preferably 7 to 30 nm, more preferably 9 to 26 nm, and even more preferably 11 to 21 nm.
• the EUV transmitting coating 10 preferably has a nitrogen concentration gradient region in which the nitrogen concentration decreases toward the metal beryllium layer 12. That is, as described above, beryllium nitride compositions can range from stoichiometric compositions such as Be3N2 to non-stoichiometric compositions such as Be3N2 -x (where 0 ⁇ x ⁇ 2). However, it is preferable that the beryllium nitride constituting the beryllium nitride layer have a gradient composition that approaches a beryllium-rich composition toward the metal beryllium layer 12.
• the thickness of the nitrogen concentration gradient region is preferably smaller than the thickness of each of the nitride layers 14a, 14b. That is, the entire thickness of each of the nitride layers 14a, 14b does not need to be the nitrogen concentration gradient region.
• each of the nitride layers 14a, 14b for example, a region of 10 to 70% of the thickness of each of the nitride layers 14a, 14b is the nitrogen concentration gradient region, and more preferably, a region of 15 to 50% is the nitrogen concentration gradient region.
• the EUV transmitting film 10 preferably has a main region for transmitting EUV in the form of a free-standing film. That is, like the pellicle 11 shown in Figure 2B(k) described below, it is preferable that the substrate 20 or the like (e.g., Si substrate) used during film formation remains as a border only at the outer edge of the EUV transmitting film 10. In other words, it is preferable that no substrate or the like (e.g., Si substrate) remains in the main region other than the outer edge; that is, the main region consists of only three layers: the first nitride layer 14a, the metal beryllium layer 12, and the second nitride layer 14b.
• the substrate 20 or the like e.g., Si substrate
• the main region consists of only three layers: the first nitride layer 14a, the metal beryllium layer 12, and the second nitride layer 14b.
• the EUV transmitting film or pellicle according to the present invention can be fabricated by forming a five-layer composite film on a Si substrate, with protective layers containing amorphous carbon on both sides of the EUV transmitting film, and then removing unnecessary portions of the Si substrate and protective layers by etching to form a free-standing film. Therefore, as described above, the main part of the EUV transmitting film is in the form of a free-standing film with no Si substrate remaining.
• a Si substrate 28 is prepared on which a composite film will be formed.
• the main region i.e., the region to be a free-standing film
• a mask corresponding to the EUV-transmitting shape on the Si substrate using a conventional semiconductor process, and then etch the Si substrate by wet etching to thin the thickness of the main region of the Si substrate to a predetermined thickness.
• the Si substrate after wet etching is then washed and dried to prepare a Si substrate having a cavity formed by wet etching.
• the wet etching mask may be made of any material that is corrosion-resistant to the wet etching solution for Si, such as SiO .
• the wet etching solution is not particularly limited as long as it can etch Si.
• TMAH tetramethylammonium hydroxide
• TMAH tetramethylammonium hydroxide
• a composite film consisting of the second protective layer 16b, the second nitride layer 14b, the metal beryllium layer 12, the first nitride layer 14a, and the first protective layer 16a is formed in this order on the Si substrate.
• the composite film may be formed by any film formation method.
• a preferred example of the film formation method is sputtering.
• the metal beryllium layer 12 is preferably formed by sputtering using a pure Be target.
• the first nitride layer 14a and the second nitride layer 14b are also preferably formed by sputtering.
• a Si, Be, B, or Zr film may be formed by sputtering using a Si, Be, B, or Zr target, and then nitrogen plasma may be applied to cause a nitriding reaction of the Si, Be, B, or Zr, thereby forming the nitride layers 14a and 14b.
• the first nitride layer 14a and the second nitride layer 14b may be formed by reactive sputtering.
• This reactive sputtering can be performed, for example, by introducing nitrogen gas into the chamber during sputtering using a Si, Be, B, or Zr target, thereby reacting the Si, Be, B, or Zr with nitrogen to produce silicon nitride, beryllium nitride , boron nitride , or zirconium nitride.
• the nitride layers 14a and 14b may be directly formed by sputtering using a Si3N4 , Be3N2 , BN, or ZrN target.
• nitrogen gas may be introduced into the chamber to promote the reaction of Si, Be, B, or Zr with nitrogen to produce silicon nitride, beryllium nitride, boron nitride, or zirconium nitride, as in the reactive sputtering described above in (ii).
• Each of the first protective layer 16a and the second protective layer 16b is a layer containing amorphous carbon.
• Layers containing amorphous carbon not only provide high protection against various chemicals (e.g., highly reactive fluorine-based etching agents) used in the pellicle film manufacturing process (e.g., the self-supporting film process), but are also advantageous in that the residue left behind when the protective layers 16a and 16b are removed has little effect on the EUV-transmitting film 10, and the protective layers 16a and 16b are easily removed.
• the first protective layer 16a and the second protective layer 16b preferably contain amorphous carbon as their primary component, and are more preferably composed of amorphous carbon.
• the methods for forming the metal beryllium layer 12, nitride layers 14a, 14b, and protective layers 16a, 16b are not limited to these.
• the metal beryllium layer 12, nitride layers 14a, 14b, and protective layers 16a, 16b may be formed in a single-chamber sputtering system, as in the examples described below, or the metal beryllium layer 12, nitride layers 14a, 14b, and protective layers 16a, 16b may be formed in separate chambers using a multi-chamber sputtering system.
• first nitride layer 14a and the second nitride layer 14b are beryllium nitride layers containing a nitrogen concentration gradient region, i.e., when forming a nitrogen concentration gradient region in an EUV transmitting film 10 with a three-layer structure of beryllium nitride/beryllium/beryllium nitride, nitrogen gas can be introduced into the chamber to deposit the beryllium nitride film and metal beryllium film while continuing sputtering using a pure Be target. The introduction of nitrogen gas can then be stopped midway through to switch to metal beryllium film deposition.
• the Si substrate 28 on which the composite film is formed is etched to remove unnecessary portions of the Si substrate, except for the outer edge portion to be left as a border, to form a freestanding composite film. While any method for etching Si may be used, etching using XeF2 is preferred. Next, exposed portions of the first protective layer 16a and the second protective layer 16b are removed to obtain a three-layer EUV transmitting film 10 in the form of a pellicle 11, consisting of the metal beryllium layer 12, the first nitride layer 14a, and the second nitride layer 14b.
• the first protective layer 16a and the second protective layer 16b no longer require strong protective function against the fluorine-based etchant and are therefore unnecessary films in terms of reducing EUV transmittance. Therefore, after forming the composite film into a freestanding film, the protective layers 16a and 16b can be removed to further increase EUV transmittance.
• the entire first protective layer 16a and the exposed portion of the second protective layer 16b can be removed. Meanwhile, the second protective layer 16b interposed between the Si substrate 28 and the second protective layer 16b remains intact, forming the amorphous carbon layer 16 of the pellicle 11.
• the EUV-transmitting film 10 is preferably provided in the form of a pellicle 11.
• the pellicle 11 comprises a substrate 20, an amorphous carbon layer 16, and the EUV-transmitting film 10.
• the substrate 20 has a first surface 20a and a second surface 20b, and has a cavity 26 in the center.
• the substrate 20 is preferably a Si substrate or a Si border.
• the first surface 20a of the substrate 20 is covered with the amorphous carbon layer 16.
• the EUV-transmitting film 10 covers the surface of the amorphous carbon layer 16 opposite the substrate 20, and is exposed as a free-standing film that forms the bottom surface of the cavity 26 at the same height as the surface of the amorphous carbon layer 16.
• the amorphous carbon layer 16 is a layer containing amorphous carbon.
• the amorphous carbon layer 16 i.e., the second protective layer 16b located directly below the second nitride layer 14b contributes to improving the strength of the second nitride layer 14b.
• the amorphous carbon layer 16 contributes to improving the crystallinity of the second nitride layer 14b formed thereon, thereby increasing the density and strength of the second nitride layer 14b.
• the thickness of the amorphous carbon layer 16 is preferably 1 to 15 nm, more preferably 2 to 12 nm, and even more preferably 3 to 10 nm.
• the second protective layer 16b interposed between the Si border 20 and the second nitride layer 14b remains intact, forming the amorphous carbon layer 16 of the pellicle 11.
• the pellicle 11 including the three-layer EUV transmitting film 10 from which the first protective layer 16a and the second protective layer 16b have been removed is then attached to an EUV exposure device, and EUV is allowed to pass through the EUV transmitting film 10 to perform pattern exposure on a photosensitive substrate in the EUV exposure device.
• the resist mask 24 for SiO 2 etching was removed using an ashing device ( FIG. 2A(e)).
• the Si was then wet-etched using TMAH solution.
• the etching rate was measured in advance, and this etching was carried out for a time required to achieve the target Si substrate thickness of 50 ⁇ m (FIG. 2A(f)).
• the SiO2 film 22 formed on the Si surface that was not etched was removed and cleaned with hydrofluoric acid to prepare a Si substrate 28 (FIG. 2B(g)).
• the Si substrate may be diced with a laser 30 (FIG. 2B(h)) to obtain the desired shape (FIG. 2B(i)) as needed.
• a 110 mm ⁇ 145 mm cavity 26 was provided in the center of the 8-inch (20.32 cm) Si wafer 20, and a Si substrate 28 with a Si thickness of 50 ⁇ m in the cavity 26 portion was prepared.
• the chamber was evacuated again, and sputtering was performed using the Si3N4 target at an internal pressure of 0.7 Pa and argon gas only. Sputtering was terminated once a 2 nm film of Si3N4 was formed. Furthermore, the chamber was evacuated again, and sputtering was performed using a pure Be target at an internal pressure of 0.5 Pa and argon gas only, with the sputtering ending just as the beryllium film had grown to 20 nm. Next, the chamber was evacuated again, and sputtering was performed using a Si 3 N 4 target at an internal pressure of 0.7 Pa and argon gas only, with the sputtering ending just as the beryllium film had grown to 2 nm .
• sputtering was performed using a graphite target in the same manner as the first step, with the sputtering ending just as the amorphous carbon film had grown to 2 nm.
• a composite film of amorphous carbon (C) 2 nm/silicon nitride (Si 3 N 4-x ) 2 nm/beryllium (Be) 20 nm/silicon nitride (Si 3 N 4-x ) 2 nm/amorphous carbon (C) 2 nm was formed.
• this composite film has a five-layer structure consisting of an EUV transmitting film 10 composed of three layers, namely, a first nitride layer 14a, a metal beryllium layer 12, and a second nitride layer 14b, and a first protective layer 16a and a second protective layer 16b containing amorphous carbon as a main component, which are formed on both sides of the EUV transmitting film 10, respectively.
• the valve between the auxiliary chamber and the chamber was opened, and XeF2 gas was introduced into the chamber.
• the XeF2 gas decomposed into Xe and F, and the F reacted with Si to produce SiF4 . Since the boiling point of SiF4 is -95°C, the generated SiF4 quickly evaporated, causing a reaction of F with the newly exposed Si substrate.
• the chamber was evacuated and XeF2 gas was again introduced into the chamber to continue etching.
• Example 2 (reference) A composite freestanding film (having protective layers 16a and 16b on both sides of the EUV transmitting film 10) having a Si border 20 was fabricated in the same manner as in Example 1. The amorphous carbon layers exposed on both sides of the composite freestanding film were then etched with hydrogen plasma to reduce the thickness of each amorphous carbon layer to 1 nm.
• a five-layer composite freestanding film having a Si border 20 and consisting of 1 nm of amorphous carbon (C), 2 nm of silicon nitride (Si 3 N 4-x ), 20 nm of beryllium (Be), 2 nm of silicon nitride (Si 3 N 4-x ), and 1 nm of amorphous carbon (C) was obtained ( FIG. 2B(j) ).
• Example 3 A composite freestanding film (in which protective layers 16a, 16b were provided on both sides of the EUV transmitting film 10) having a Si border 20 was produced in the same manner as in Example 1. Thereafter, the amorphous carbon layers exposed on both sides of the EUV transmitting film 10 were etched with hydrogen plasma to remove each amorphous carbon layer except for the amorphous carbon layer 16 in the portion sandwiched between the EUV transmitting film 10 and the Si border 20.
• a three-layer composite freestanding film i.e., EUV transmitting film 10 having a Si border 20 and consisting of silicon nitride (Si 3 N 4-x ) 2 nm/beryllium (Be) 20 nm/silicon nitride (Si 3 N 4-x ) 2 nm was obtained in the form of a pellicle 11 (FIG. 2B(k)).
• Example 4 A composite freestanding film (having protective layers 16a, 16b provided on both sides of the EUV transmitting film 10) having a Si border 20 was produced in the same manner as in Example 1 , except that in ( 2 ) above, the film formation times for amorphous carbon and silicon nitride were changed to form a composite film of amorphous carbon (C) 12 nm/silicon nitride ( Si3N4 -x ) 1 nm/beryllium (Be) 20 nm/silicon nitride (Si3N4-x) 1 nm/amorphous carbon (C) 12 nm.
• the freestanding films serving as EUV transmitting films prepared in Examples 1 to 3 for EUV transmittance and in-plane uniformity were irradiated with EUV light at an output of 600 W in a hydrogen atmosphere at 20 Pa for 15 minutes, and the transmitted EUV light intensity was measured with a sensor.
• the EUV transmittance was calculated by comparing the obtained measured values with the EUV light intensity directly measured with a sensor without an EUV transmitting film, and the results shown in Table 1 were obtained.
• the EUV light spot used for the transmittance measurement had an oval shape of 0.5 mm ⁇ 0.2 mm, and the EUV transmittance at a wavelength of 13.5 nm was measured within this spot size.
• the present invention can provide an EUV transmitting film that exhibits high EUV transmittance.
• Example 4 is an embodiment in which the thickness of the amorphous carbon layers serving as the first protective layer 16a and the second protective layer 16b is 12 ⁇ m, which is thicker than the thickness (2 ⁇ m) of the amorphous carbon layers in Examples 1 to 3, thereby enhancing the protective function against fluorine-based etching agents.
• Table 1 in the present invention, high EUV transmittance can be achieved by finally removing the protective layers 16a and 16b, and therefore the protective function can be enhanced by thickening the amorphous carbon layers serving as the protective layers 16a and 16b, as in Example 4.

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