Euv transmission film, shield, and exposure method

Abstract

The present application provides an EUV transmissive film which exhibits high EUV transmittance. The EUV transmissive film (10) is composed of three layers, including: a metal beryllium layer (12) having a first surface and a second surface; a first nitride layer (14a) covering the first surface (12a) of the beryllium layer (12) and containing at least one selected from the group consisting of silicon nitride, beryllium nitride, boron nitride and zirconium nitride; and a second nitride layer (14b) covering the second surface (12b) of the beryllium layer (12) and containing at least one selected from the group consisting of silicon nitride, beryllium nitride, boron nitride and zirconium nitride. The EUV transmissive film (10) has an EUV transmittance of 88% or more at a wavelength of 13.5 nm.

Description

Technical Field

[0001] This invention relates to EUV-permeable membranes, protective components, and exposure methods. Background Technology

[0002] Semiconductor manufacturing processes are becoming increasingly miniaturized, with various improvements being made to each step. In particular, the photolithography process has begun using EUV (Extreme Ultraviolet) light with a wavelength of 13.5 nm to replace the previous 193 nm wavelength used in ArF exposure. As a result, the wavelength is now less than one-tenth of the original wavelength, leading to completely different optical properties. However, there are no materials with high transmittance for EUV light; therefore, protective components, such as pellicles used as anti-particle films in photomasks (reticles), are not yet practical. Consequently, device manufacturers currently manufacture semiconductor devices without using protective components.

[0003] Therefore, in developing protective films, the core materials preferably used are those with high EUV transmittance, such as Si, Be, Y, and Zr. Patent Document 1 (Japanese Patent No. 6858817) discloses a protective film comprising: a core layer containing a material such as (Poly)Si that is substantially transparent to EUV radiation; and an upper cover layer containing a material that absorbs IR radiation.

[0004] Furthermore, Patent Document 2 (Japanese Patent Application Publication No. 2020-98227) discloses a protective film that is stretched and disposed on one end face of a protective frame and has a main layer of single-crystal Si, with graphene on one or both sides of the main layer. Because the main layer contains graphene, the protective film will not break during the fabrication of the protective component, thus exhibiting sufficient mechanical strength.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6858817

[0008] Patent Document 2: Japanese Patent Application Publication No. 2020-98227 Summary of the Invention

[0009] However, the core materials used in the protective film, which have high EUV transmittance, develop a natural oxide film of several nm on their surface in the atmosphere. This oxide film absorbs EUV, leading to a decrease in the EUV transmittance of the protective film. In particular, Be is a material with high EUV transmittance, but a natural oxide film of 2-3 nm forms on its surface, resulting in a transmittance loss of 6-9%. Furthermore, the manufacturing process of the protective film sometimes involves treatment with gases such as fluorine or chlorine, acid solutions, or alkaline solutions other than atmospheric gases. Therefore, side reaction films may also form on the surface of the core material, further reducing EUV transmittance. Therefore, it is desirable to form a protective layer on the surface of the core material to inhibit the formation of these films.

[0010] However, while setting a reaction-inhibiting protective layer on the surface of core materials such as Si and Be can prevent a significant decrease in the EUV transmittance of the protective film, such a protective layer has a lower EUV transmittance compared to the pure core material, resulting in a decrease in the overall EUV transmittance of the protective film. For example, Ru can be used as a protective layer for Be core materials. However, considering the case of a three-layer structure (Ru / Be / Ru) protective film with 1-2 nm of Ru on the surface and back of the Be core material, the EUV transmittance loss due to the Ru protective layer is about 3-6%, which significantly reduces the performance of the protective film.

[0011] The inventors of this invention recently discovered that by employing a three-layer structure consisting of a nitride layer, a beryllium metal layer, and a nitride layer, an EUV-transmitting membrane exhibiting high EUV transmittance can be provided.

[0012] Therefore, an object of the present invention is to provide an EUV-transmitting film or protective element exhibiting high EUV transmittance. Another object of the present invention is to provide an exposure method using an EUV-transmitting film.

[0013] According to the present invention, the following solution is provided.

[0014] [Option 1]

[0015] An EUV permeable membrane, which is composed of the following three layers:

[0016] The three-layer structure includes:

[0017] A beryllium metal layer having a first surface and a second surface;

[0018] A first nitride layer, which covers a first surface of the beryllium layer, and comprises at least one material selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride; and

[0019] A second nitride layer covers the second side of the beryllium layer and comprises at least one material selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride.

[0020] The EUV-permeable membrane is characterized in that...

[0021] The EUV-transmitting membrane has an EUV transmittance of over 88% at a wavelength of 13.5 nm.

[0022] [Option 2]

[0023] The EUV permeable membrane according to Scheme 1 is characterized in that,

[0024] The thickness of the EUV-permeable membrane is 7–30 nm.

[0025] [Option 3]

[0026] The EUV permeable membrane according to Scheme 1 or 2 is characterized in that,

[0027] The thickness of the beryllium layer is 5–25 nm.

[0028] [Option 4]

[0029] The EUV permeable membrane according to any one of claims 1 to 3 is characterized in that,

[0030] The thickness of the first nitride layer and the second nitride layer is 1 to 5 nm.

[0031] [Option 5]

[0032] A protective component, characterized in that it comprises:

[0033] A substrate having a first surface and a second surface, and having a cavity in the center;

[0034] An amorphous carbon layer that covers a first surface of the substrate; and

[0035] The EUV-permeable membrane described in any one of Schemes 1 to 4 covers the surface of the amorphous carbon layer opposite to the substrate and is exposed as a self-standing membrane forming the bottom surface of the cavity at the same height as the surface of the amorphous carbon layer.

[0036] [Option 6]

[0037] The protective component according to Scheme 5 is characterized in that,

[0038] The thickness of the amorphous carbon layer is 1–15 nm.

[0039] [Option 7]

[0040] The protective component according to scheme 5 or 6 is characterized in that,

[0041] The substrate is a Si substrate.

[0042] [Option 8]

[0043] The protective component according to any one of claims 5 to 7 is characterized in that,

[0044] The protective component also includes a mask layer that covers the second side of the substrate.

[0045] [Option 9]

[0046] The protective component according to Scheme 8 is characterized in that,

[0047] The mask layer is a SiO2 layer.

[0048] [Option 10]

[0049] An exposure method, characterized by comprising the following steps:

[0050] Prepare a composite membrane consisting of 5 layers, each having a protective layer containing amorphous carbon on both sides of the EUV permeable membrane described in any of Schemes 1 to 4.

[0051] The composite membrane consisting of the five layers is installed in a device that generates hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals.

[0052] The protective layer is removed by contacting the composite film consisting of the five layers with hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals; and

[0053] An EUV-transmitting film consisting of three layers with the protective layer removed is installed inside an EUV exposure apparatus, allowing EUV to pass through the EUV-transmitting film to perform pattern exposure on the photosensitive substrate inside the EUV exposure apparatus. Attached Figure Description

[0054] Figure 1 This is a simplified cross-sectional view showing one aspect of the EUV permeable membrane of the present invention.

[0055] Figure 2A This is a process flow diagram showing the first half of the manufacturing steps for EUV permeable membranes.

[0056] Figure 2B This is a process flow diagram showing the latter half of the manufacturing process of EUV permeable membranes. Detailed Implementation

[0057] EUV permeable membrane

[0058] Figure 1 The diagram shows a simplified cross-sectional view of an EUV permeable membrane 10 according to one embodiment of the present invention. The EUV permeable membrane 10 is a three-layer membrane comprising a beryllium metal layer 12, a first nitride layer 14a, and a second nitride layer 14b. The beryllium metal 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 beryllium metal layer 12 and comprising at least one layer 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 beryllium metal layer 12 and comprising at least one layer selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride. The EUV permeable membrane 10 has an EUV transmittance of 88% or more at a wavelength of 13.5 nm. By employing a three-layer structure consisting of a first nitride layer 14a, a beryllium metal layer 12, and a second nitride layer 14b, an EUV-transmitting membrane 10 exhibiting high EUV transmittance can be provided.

[0059] As mentioned above, core materials with high EUV transmittance sometimes form a natural oxide film of several nm on their surface in the atmosphere. Furthermore, during the fabrication of the protective film, treatment with gases such as fluorine or chlorine (other than atmospheric gases), acid solutions, or alkaline solutions is sometimes performed, which can also lead to the formation of a secondary reaction film on the surface of the core material. The formation of such films reduces the EUV transmittance of the protective film. Therefore, it is desirable to form a protective layer on the surface of the core material to inhibit the formation of these films. However, by providing a reaction-inhibiting protective layer on the surface of the core material, the overall EUV transmittance of the protective film decreases. To address this, it is considered to provide an amorphous carbon layer on both sides of the EUV-transmitting film as a protective film that can be removed by contacting it with hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals. The aforementioned natural oxide film or secondary reaction film forms on both sides of the EUV-transmitting film 10 during fabrication, before it is mounted in an EUV exposure apparatus and the exposure process is performed. By providing an amorphous carbon layer on both sides of the EUV-transmitting film 10 as a protective layer, the formation of these films can be prevented. In particular, the amorphous carbon layer is effective in protecting the EUV-transmitting membrane 10 from damage by various agents (such as highly reactive fluorine-based etchants) used in the protective film fabrication process (e.g., the self-standing film formation process). Furthermore, if the amorphous carbon layer is directly disposed on the beryllium layer 12, the amorphous carbon and beryllium may sometimes react to form beryllium carbide. However, by employing a three-layer configuration of the first nitride layer 14a / beryllium layer 12 / first nitride layer 14a, and disposing of the amorphous carbon layer on the nitride layers 14a and 14b, undesirable reactions between the amorphous carbon and beryllium can be prevented. On the other hand, after functioning as a protective layer in the protective film fabrication process (e.g., the self-standing film formation process), the amorphous carbon layer becomes an undesirable membrane in terms of reducing EUV transmittance. Therefore, by removing the amorphous carbon layer through contact with hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals, EUV transmittance can be improved. The resulting EUV-transmitting film 10 consists of three layers: a beryllium metal layer 12, a first nitride layer 14a, and a second nitride layer 14b. It no longer has a protective layer (amorphous carbon layer), thus avoiding the reduction in EUV transmittance caused by the protective layer. As a result, the EUV-transmitting film 10 can maximize the inherent high transmittance of its three-layer structure (beryllium metal layer 12, first nitride layer 14a, and second nitride layer 14b), meaning it exhibits high EUV transmittance during exposure.

[0060] As described above, the EUV permeable membrane 10 has a high EUV transmittance. The EUV permeable membrane 10 has an EUV transmittance of 88% or more at a wavelength of 13.5 nm, preferably 92% or more, more preferably 93% or more, further preferably 94% or more, particularly preferably 95% or more, and most preferably 96% or more. A higher EUV transmittance is more desirable, and there is no particular upper limit; ideally it is 100%, but typically it is 99% or less, and more typically 98% or less.

[0061] The beryllium layer 12 is a layer containing beryllium as the main component. Here, the "main component" in the beryllium layer 12 refers to a component that occupies 50 mol% or more, preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more of the beryllium layer 12. In addition to containing beryllium as the main component, the beryllium layer 12 may also contain impurities. Therefore, the beryllium layer 12 can be composed of beryllium and unavoidable impurities. The thickness of the beryllium layer 12 is preferably 5 to 25 nm, more preferably 7 to 20 nm, and even more preferably 9 to 15 nm.

[0062] The first nitride layer 14a and the second nitride layer 14b each comprise 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 having the first nitride layer 14a and the second nitride layer 14b on both sides of the beryllium layer 12 are as described above. It should be noted that the terms "silicon nitride," "beryllium nitride," "boron nitride," and "zirconium nitride" in this specification refer to: not only stoichiometric compositions such as Si3N4, Be3N2, BN, and ZrN are permissible, but also Si3N... 4-x (where 0 < x < 4), Be3N 2-x (where 0 < x < 2), BN x (where 0 < x < 1), ZrN x (where 0 < x < 1) is a general composition of non-stoichiometric composition. The thickness of the first nitride layer 14a and the second nitride layer 14b is preferably 1 to 5 nm, more preferably 1 to 3 nm.

[0063] The first nitride layer 14a, the beryllium layer 12, and the second nitride layer 14b constitute the EUV permeable membrane 10. These layers ensure the basic functions of a protective membrane (such as preventing particle adhesion) and contribute to achieving high EUV transmittance. The thickness of the EUV permeable membrane 10 is preferably 7–30 nm, more preferably 9–26 nm, and even more preferably 11–21 nm.

[0064] When the first nitride layer 14a and / or the second nitride layer 14b each contain beryllium nitride, the EUV permeable membrane 10 preferably has a nitrogen concentration gradient region where the nitrogen concentration decreases as it approaches the metallic beryllium layer 12. That is, as described above, the beryllium nitride composition may contain stoichiometric compositions ranging from Be3N2 to Be3N... 2-x In the case of a non-stoichiometric composition (where 0 < x < 2), the beryllium nitride constituting the beryllium nitride layer is preferably configured as a gradient composition approaching a beryllium-rich composition as it approaches the metallic beryllium layer 12. This improves the adhesion between the nitride layers 14a and 14b (i.e., the beryllium nitride layer) constituting the EUV-transmitting membrane 10 and the metallic beryllium layer 12, and mitigates stress caused by the thermal expansion difference between these layers. That is, it can improve the adhesion between these layers to suppress peeling, or act as a thermal expansion mitigation layer when absorbing EUV light and reaching high temperatures, making peeling difficult. The thickness of the nitrogen concentration gradient region is preferably smaller than the thickness of each of the nitride layers 14a and 14b. That is, the entire region where the thickness of each of the nitride layers 14a and 14b is not required is a nitrogen concentration gradient region. For example, it is preferable that only a portion of the thickness of each of the nitride layers 14a and 14b, such as 10 to 70% of the thickness of each of the nitride layers 14a and 14b, is a nitrogen concentration gradient region, and more preferably 15 to 50% of the region is a nitrogen concentration gradient region.

[0065] EUV permeable membrane 10 is preferably in the form of a self-standing membrane, where the main area for EUV transmission is located. That is, it is preferably as described later. Figure 2B As shown in (k), the substrate 20 (e.g., Si substrate) used only when forming a film at the outer edge of the EUV permeable membrane 10 remains in the form of a border. That is, preferably, no substrate (e.g., Si substrate) remains in the main area other than the outer edge. In other words, the main area consists of only three layers: the first nitride layer 14a, the beryllium metal layer 12, and the second nitride layer 14b.

[0066] Manufacturing method

[0067] The EUV-permeable membrane or protective component of the present invention can be manufactured as follows: after forming a composite film consisting of five layers, each having a protective layer containing amorphous carbon on both sides of the EUV-permeable membrane, on a Si substrate, the unwanted portions of the Si substrate and the protective layers are removed by etching, thereby achieving self-standing film formation, and thus the EUV-permeable membrane or protective component is manufactured. Therefore, as described above, the main part of the EUV-permeable membrane is a self-standing film without any residual Si substrate.

[0068] (1) Preparation of Si substrate

[0069] First, such as Figure 2BAs shown, a Si substrate 28 is prepared for forming a composite film thereon. After forming a composite film including a second protective layer 16b, a second nitride layer 14b, a beryllium layer 12, a first nitride layer 14a, and a first protective layer 16a on the Si substrate 28, the main area (i.e., the area where a self-standing film is to be formed) is removed by etching, except for the outer edge. Therefore, in order to perform etching efficiently in a short time, it is preferable to thin the thickness of the Si substrate in the area where a self-standing film is to be formed beforehand. Therefore, it is desirable to form a mask corresponding to the EUV transmission shape on the Si substrate using conventional semiconductor processes, and to etch the Si substrate using wet etching to thin the thickness of the main area of ​​the Si substrate to a predetermined thickness. The wet-etched Si substrate is cleaned and dried, thereby preparing a Si substrate having cavities formed by wet etching. It should be noted that as the wet etching mask, any material that is corrosion-resistant to the wet etching solution for Si is acceptable, for example, SiO2 is preferred. In addition, as the wet etching solution, there is no particular limitation as long as it can etch Si. For example, if TMAH (tetramethylammonium hydroxide) is used under appropriate conditions, etching can be performed very well with anisotropic etching of Si, and is therefore preferred.

[0070] (2) Formation of composite membrane

[0071] A composite film comprising a second protective layer 16b, a second nitride layer 14b, a beryllium layer 12, a first nitride layer 14a, and a first protective layer 16a is sequentially formed on a Si substrate. The composite film can be formed using any film-forming method. Sputtering is a preferred example of such a method. The beryllium layer 12 is preferably fabricated using sputtering with a pure Be target.

[0072] The first nitride layer 14a and the second nitride layer 14b are preferably fabricated using sputtering. For example, (i) the nitride layers 14a and 14b can be formed by sputtering a Si, Be, B, or Zr film using a Si, Be, B, or Zr target, followed by irradiation with nitrogen plasma to induce a nitriding reaction in the Si, Be, B, or Zr. Alternatively, (ii) the first nitride layer 14a and the second nitride layer 14b can be fabricated using reactive sputtering. This reactive sputtering can be performed as follows: for example, in sputtering using a Si, Be, B, or Zr target, nitrogen gas is introduced into the chamber to react with Si, Be, B, or Zr to generate silicon nitride, beryllium nitride, boron nitride, or zirconium nitride. Or, (iii) the nitride layers 14a and 14b can be directly formed using sputtering using a Si3N4, Be3N2, BN, or ZrN target. In this sputtering process, by introducing nitrogen gas into the chamber, nitrogen can react with Si, Be, B or Zr to promote the formation of silicon nitride, beryllium nitride, boron nitride or zirconium nitride, as in the reactive sputtering described in (ii) above.

[0073] The first protective layer 16a and the second protective layer 16b are both layers containing amorphous carbon. Regarding the layers containing amorphous carbon, in addition to exhibiting higher protective performance compared to various agents (such as highly reactive fluorine-based etchants) used in the protective film manufacturing process (e.g., the self-supporting film formation process), it is also advantageous that the residue from removing the protective layers 16a and 16b has less impact on the EUV-transmitting membrane 10, and that the protective layers 16a and 16b are easy to remove. The first protective layer 16a and the second protective layer 16b preferably contain amorphous carbon as the main component, and more preferably are composed of amorphous carbon. Generally, amorphous carbon rarely has a completely irregular atomic arrangement; it usually has a crystalline structure (i.e., microcrystals) at the microscopic level. In such cases, the irregular arrangement of these microcrystals makes the overall structure amorphous. The material containing numerous three-dimensional 4-coordinate microcrystals, like diamond, is called DLC (diamond-like carbon), and the material containing numerous planar 3-coordinate particles, like graphite, is called GLC (graphite-like carbon). The first protective layer 16a and the second protective layer 16b can be carbon with a completely irregular atomic arrangement or carbon with irregularly arranged microcrystals. Furthermore, they can be amorphous carbon containing fine pores and not completely dense. Here, the "main component" in the first protective layer 16a and the second protective layer 16b refers to a component that occupies 50% or more by weight, preferably 60% or more by weight, more preferably 70% or more by weight, and even more preferably 80% or more by weight in the total weight of the first protective layer 16a or the second protective layer 16b. However, the first protective layer 16a and the second protective layer 16b can be composed solely of amorphous carbon. The thickness of each of the first protective layer 16a and the second protective layer 16b is preferably 1–15 nm, more preferably 2–12 nm, and even more preferably 3–10 nm. The amorphous carbon layer used as the first protective layer 16a and the second protective layer 16b is preferably fabricated by sputtering using a graphite target.

[0074] It should be noted that the methods for forming the beryllium layer 12, nitride layers 14a, 14b, and protective layers 16a, 16b are not limited to these methods. Furthermore, the beryllium layer 12, nitride layers 14a, 14b, and protective layers 16a, 16b can be formed using a single-chamber sputtering apparatus as described in the embodiments below, or multiple-chamber sputtering apparatuses can be used to form the beryllium layer 12, nitride layers 14a, 14b, and protective layers 16a, 16b separately in each chamber.

[0075] When the first nitride layer 14a and the second nitride layer 14b are beryllium nitride layers containing a nitrogen concentration gradient region—that is, when a nitrogen concentration gradient region is formed in the EUV permeable membrane 10 with a three-layer structure of beryllium nitride / beryllium / beryllium nitride—during the deposition of beryllium nitride and metallic beryllium, nitrogen gas is introduced into the chamber while sputtering with a pure Be target continues, and the nitrogen introduction is stopped midway to switch to metallic beryllium deposition. Accordingly, as the nitrogen concentration in the chamber decreases, a region in the deposited membrane where the nitrogen concentration decreases along the thickness direction is formed. On the other hand, when switching from metallic beryllium to beryllium nitride, the opposite is true; if sputtering continues while nitrogen introduction is started midway, a nitrogen concentration gradient region can be formed. By adjusting the time for changing the nitrogen concentration, the thickness of the nitrogen concentration gradient region can be controlled.

[0076] (3) Self-supporting membrane formation

[0077] The unwanted portions of the Si substrate 28, excluding the outer edge remaining in the form of a boundary, are removed by etching to perform self-standing film formation of the composite film. The etching of Si can be performed using any method, but etching using XeF2 is preferred. Next, the exposed portions of the first protective layer 16a and the second protective layer 16b are removed, resulting in an EUV-transmitting film 10 consisting of three layers: a beryllium layer 12, a first nitride layer 14a, and a second nitride layer 14b, in the form of a protective member 11. In particular, after the aforementioned self-standing film formation process using a fluorine-based etchant such as XeF2, the first protective layer 16a and the second protective layer 16b no longer need to have strong protective function against the fluorine-based etchant, thus becoming undesirable films in terms of reducing EUV transmittance. Therefore, after performing self-standing film formation of the composite film, EUV transmittance can be further improved by removing the protective layers 16a and 16b. The preferred process for removing the first protective layer 16a and the second protective layer 16b, i.e., the amorphous carbon layer, is as follows: A composite film including the EUV-permeable membrane 10 is mounted in a device that generates hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals, and the hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals, come into contact with the composite film, thereby removing the protective layer. Alternatively, the first protective layer 16a and the second protective layer 16b, i.e., the amorphous carbon layer, are exposed to a hydrogen plasma and / or hydrogen free radical atmosphere or an oxygen plasma and / or oxygen free radical atmosphere, causing the C and H on the surface of the amorphous carbon layer to react, thus removing the amorphous carbon layer. As a result, the entire first protective layer 16a and the exposed portion of the second protective layer 16b can be removed. On the other hand, the second protective layer 16b, located between the Si substrate 28 and the second protective layer 16b, is retained as is, forming the amorphous carbon layer 16 of the protective member 11.

[0078] Protective components

[0079] Therefore, as Figure 2B As shown in (k), the EUV permeable membrane 10 is preferably provided in the form of a protective member 11. The protective member 11 includes: a substrate 20, an amorphous carbon layer 16, and the EUV permeable membrane 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-made boundary. The first surface 20a of the substrate 20 is covered by the amorphous carbon layer 16. The EUV permeable membrane 10 covers the surface of the amorphous carbon layer 16 opposite to the substrate 20, and is exposed as a self-standing membrane forming the bottom surface of the cavity 26 at the same height as the surface of the amorphous carbon layer 16.

[0080] 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 beneath the second nitride layer 14b helps to improve the strength of the second nitride layer 14b. That is, the amorphous carbon layer 16 helps to improve the crystallinity of the second nitride layer 14b formed thereon, resulting in increased density and strength of the second nitride layer 14b. Specifically, when the second nitride layer 14b is directly formed on the substrate 20 without the amorphous carbon layer 16, the crystallinity of the nitride deteriorates in the initial stage of film formation, leading to a decrease in the density and strength of the nitride. In this respect, by forming the film on the substrate 20 with the amorphous carbon layer 16 in between, a film with good nitride crystallinity can be obtained as the second nitride layer 14b. The amorphous carbon layer 16 corresponds to the aforementioned second protective layer 16b; therefore, the aforementioned description related to the second protective layer 16b directly applies to the amorphous carbon layer 16. Therefore, 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.

[0081] The protective component 11 may further include a mask layer 22a that covers the second surface 20b of the substrate 20. The mask layer 22a is preferably a SiO2 layer.

[0082] Exposure method

[0083] According to a preferred embodiment of the present invention, the following exposure method using an EUV-permeable film 10 is provided. In this method, firstly, as... Figure 2BAs shown in (j), a composite membrane consisting of five layers, including a first protective layer 16a and a second protective layer 16b of amorphous carbon, is prepared on both sides of the EUV-permeable membrane 10. Next, the five-layer composite membrane is installed in a device that generates hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals. Then, the hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals, are brought into contact with the five-layer composite membrane, thereby removing the exposed portions of the first protective layer 16a and the second protective layer 16b. At this time, as... Figure 2B As shown in (k), the second protective layer 16b, located between the Si boundary 20 and the second nitride layer 14b, is retained as is, forming the amorphous carbon layer 16 of the protective member 11. The protective member 11, comprising a three-layer EUV-transmitting film 10 with the first protective layer 16a and the second protective layer 16b removed, is installed in an EUV exposure apparatus, allowing EUV to pass through the EUV-transmitting film 10 to perform pattern exposure on the photosensitive substrate within the EUV exposure apparatus.

[0084] Example

[0085] The invention will be further illustrated by the following examples. However, the invention is not limited to these examples.

[0086] Example 1 (refer to)

[0087] according to Figure 2A and Figure 2B The steps shown are as follows: a composite self-standing membrane consisting of five layers of amorphous carbon / silicon nitride / Be / silicon nitride / amorphous carbon is fabricated (a component with protective layers 16a and 16b provided on both sides of the EUV permeable membrane 10).

[0088] (1) Preparation of Si substrate

[0089] Prepare to produce 8-inch (20.32cm) diameter Si wafers 20 ( Figure 2A (a)). On both sides of the Si wafer 20, a SiO2 film 22 with a thickness of 50 nm is formed by thermal oxidation. Figure 2A (b)). A photoresist is coated on both sides of the Si wafer 20, and exposure and development are performed to form a photoresist mask 24 for SiO2 etching, enabling the formation of 110mm × 145mm photoresist holes on one side. Figure 2A (c) The substrate is wet-etched with hydrofluoric acid on one side to remove the exposed portion of the SiO2 film 22, thus creating a SiO2 mask as mask layer 22a. Figure 2A (d) The resist mask 24 used for SiO2 etching is removed using an ashing device. Figure 2A(e) Then, the Si was wet-etched using TMAH solution. The etching rate was determined beforehand, and the etching was carried out at an etching time set for a target Si substrate thickness of 50 μm. Figure 2A (f) Finally, the SiO2 film 22 formed on the side without Si etching is removed and cleaned with hydrofluoric acid to prepare the Si substrate 28. Figure 2B (g)). Regarding the shape of the Si substrate, it can be cut using laser 30 as needed. Figure 2B (h)), set to the desired shape ( Figure 2B (i)). This prepares a Si substrate 28 with a 110mm × 145mm cavity 26 in the center of an 8-inch (20.32cm) Si wafer 20 and a Si thickness of 50μm in the cavity 26 portion.

[0090] (2) Formation of composite membrane

[0091] The Si substrate 28 with cavity 26 obtained in (1) above is formed as follows: a composite film with a 5-layer structure of amorphous carbon / silicon nitride / Be / silicon nitride / amorphous carbon is formed. Figure 2B (i) First, the Si substrate 28 is fixed to a multi-target sputtering apparatus, and a graphite target, a Si3N4 target, and a pure Be target are mounted. The chamber is evacuated, and sputtering is performed using the graphite target at an internal pressure of 0.3 Pa, with only argon gas. Sputtering is stopped after a 2 nm film formation time for amorphous carbon (DLC, or diamond-like carbon). Next, the chamber is evacuated again, and sputtering is performed using the Si3N4 target at an internal pressure of 0.7 Pa, with only argon gas. Sputtering is stopped after a 2 nm film formation time for Si3N4. Then, the chamber is evacuated again, and sputtering is performed using the pure Be target at an internal pressure of 0.5 Pa, with only argon gas. Sputtering is stopped after a 20 nm film formation time for beryllium. Finally, the chamber is evacuated again, and sputtering is performed using the Si3N4 target at an internal pressure of 0.7 Pa, with only argon gas. 4-x Sputtering was stopped after a film deposition time of 2 nm. Then, sputtering was performed again using a graphite target in the same manner as initially, stopping after a 2 nm amorphous carbon film deposition time. In this way, a 2 nm amorphous carbon (C) / silicon nitride (Si3N) film was formed. 4-x 2nm / Beryllium (Be) 20nm / Silicon Nitride (Si3N) 4-x The composite film consists of 2nm of amorphous carbon (C) and 2nm of amorphous carbon (C). That is, the composite film is composed of an EUV permeable membrane 10 consisting of three layers: a first nitride layer 14a, a beryllium metal layer 12, and a second nitride layer 14b, and five layers: a first protective layer 16a and a second protective layer 16b, each containing amorphous carbon as the main component, formed on both sides of the EUV permeable membrane 10.

[0092] (3) Self-supporting membrane formation

[0093] Inside the chamber of an XeF2 electro-etcher capable of processing 8-inch (20.32 cm) substrates, the Si substrate 28 with the composite film prepared in (2) above is fixed. The chamber is fully evacuated. At this time, if there is residual moisture in the chamber, it will react with the XeF2 gas to produce hydrofluoric acid, causing corrosion of the electro-etcher or unexpected etching. Therefore, the chamber is fully evacuated. As needed, the chamber is repeatedly evacuated and nitrogen is introduced to reduce residual moisture. After fully evacuating, the valve between the XeF2 raw material bottle and the preparation chamber is opened. As a result, XeF2 sublimates, and XeF2 gas is also accumulated in the preparation chamber. After XeF2 gas is fully accumulated in the preparation chamber, the valve between the preparation chamber and the chamber is opened to introduce XeF2 gas into the chamber. XeF2 gas decomposes into Xe and F. F reacts with Si to generate SiF4. The boiling point of SiF4 is -95°C. Therefore, the generated SiF4 evaporates rapidly, and the newly exposed Si substrate reacts with F. After Si etching is performed and the F content in the chamber is reduced, the chamber is evacuated, and XeF2 gas is introduced into the chamber again for etching. This process of evacuation, XeF2 gas introduction, and etching is repeated until the Si substrate 28 corresponding to the self-standing film disappears. Etching ends after the unwanted portion of the Si substrate disappears. This yields a 5-layer composite self-standing film with a Si border 20. Figure 2B (j)).

[0094] Example 2 (refer to)

[0095] A composite self-standing film with Si boundaries 20 was fabricated in the same manner as in Example 1 (a component with protective layers 16a and 16b disposed on both sides of the EUV-transmitting film 10). Then, the amorphous carbon layers exposed on both sides of the composite self-standing film were etched using hydrogen plasma, thereby reducing the thickness of each amorphous carbon layer to 1 nm. This resulted in a film with Si boundaries 20 comprising 1 nm of amorphous carbon (C) and silicon nitride (Si3N). 4-x 2nm / Beryllium (Be) 20nm / Silicon Nitride (Si3N) 4-x A composite self-standing film consisting of 5 layers of 2nm amorphous carbon (C) and 1nm amorphous carbon (C). Figure 2B (j)).

[0096] Example 3

[0097] Similar to Example 1, a composite self-standing film with Si boundary 20 was fabricated (a component with protective layers 16a and 16b provided on both sides of the EUV-transmitting film 10). Then, the amorphous carbon layers exposed on both sides of the EUV-transmitting film 10 were etched using hydrogen plasma, thereby removing all amorphous carbon layers except for the portion of amorphous carbon layer 16 sandwiched between the EUV-transmitting film 10 and the Si boundary 20. Thus, a protective component 11 containing silicon nitride (Si3N) with Si boundary 20 was obtained. 4-x 2nm / Beryllium (Be) 20nm / Silicon Nitride (Si3N) 4-x A 2nm, three-layer composite self-standing membrane (i.e., EUV permeable membrane 10) Figure 2B (k)).

[0098] Example 4

[0099] In the above (2), the film formation times of amorphous carbon and silicon nitride were changed to form amorphous carbon (C) 12nm / silicon nitride (Si3N) film. 4-x 1nm / Beryllium (Be) 20nm / Silicon Nitride (Si3N) 4-x A composite film of 1 nm / 12 nm amorphous carbon (C) was fabricated, and a composite self-standing film with Si boundary 20 was also fabricated in the same manner as in Example 1 (a component with protective layers 16a and 16b provided on both sides of the EUV-transmitting film 10). Then, the amorphous carbon layers exposed on both sides of the EUV-transmitting film 10 were etched using hydrogen plasma, thereby removing all amorphous carbon layers except for the portion of amorphous carbon layer 16 sandwiched between the EUV-transmitting film 10 and the Si boundary 20. Thus, a protective member 11 containing silicon nitride (Si3N) with Si boundary 20 was obtained. 4-x 1nm / Beryllium (Be) 20nm / Silicon Nitride (Si3N) 4-x A 1nm three-layer composite self-standing membrane (i.e., EUV permeable membrane 10) Figure 2B (k)).

[0100] EUV transmittance and its in-plane uniformity

[0101] For the self-standing membranes used as EUV-transmitting films in Examples 1-3, EUV light was irradiated for 15 minutes at an output power of 600 W in a hydrogen atmosphere at 20 Pa. Afterwards, the amount of transmitted EUV light was measured using a sensor. The EUV transmittance was calculated by comparing the measured value with the value obtained by directly measuring the EUV light amount without the EUV-transmitting film using the sensor. The results are shown in Table 1. The EUV light spot used for transmittance measurement was an oblong shape of 0.5 mm × 0.2 mm, and the EUV transmittance at a wavelength of 13.5 nm within this spot size was measured. Therefore, to evaluate the in-plane uniformity of EUV transmittance, the EUV transmittance was measured while moving the EUV light spot. The EUV transmittance at each location was measured, and the in-plane deviation was calculated as three times the standard deviation based on these data. Therefore, the smaller the in-plane deviation, the better the in-plane uniformity of EUV transmittance.

[0102] Table 1

[0103] Table 1

[0104]

[0105] *: indicates a reference example.

[0106] The results above show that if an amorphous carbon layer is left in advance as in Examples 1 and 2, although the in-plane deviation of EUV transmittance is small, i.e., the in-plane uniformity is excellent, the EUV transmittance is reduced. On the other hand, if the amorphous carbon layer is etched away as in Examples 3 and 4, acceptable in-plane uniformity can be ensured, and the transmittance is increased. When the in-plane deviation of EUV transmittance is small, it has the advantage of uniform in-plane exposure and improved device homogeneity; however, when the EUV transmittance is high, the exposure ends in a short time, i.e., the throughput is good. That is, according to the present invention, an EUV-transmitting film exhibiting high EUV transmittance can be provided.

[0107] Furthermore, Example 4 presents a scheme in which the thickness of the amorphous carbon layer serving as the first protective layer 16a and the second protective layer 16b is set to 12 μm, which is 1 to 3 times the thickness (2 μm) of the amorphous carbon layer, thereby improving the protective function against fluorine-based etchants. As shown in Table 1, in this invention, high EUV transmittance can be achieved by ultimately removing the protective layers 16a and 16b. Therefore, by thickening the amorphous carbon layer serving as the protective layers 16a and 16b as in Example 4, the aforementioned protective function can be improved.

Claims

1. An EUV permeable membrane, comprising the following three layers: The three-layer structure includes: A beryllium metal layer having a first surface and a second surface; A first nitride layer covers a first surface of the beryllium layer and comprises at least one selected from the group consisting of silicon nitride, beryllium nitride, boron nitride and zirconium nitride. as well as A second nitride layer covers the second side of the beryllium layer and comprises at least one material selected from the group consisting of silicon nitride, beryllium nitride, boron nitride, and zirconium nitride. The EUV-permeable membrane is characterized in that... The EUV-transmitting membrane has an EUV transmittance of over 88% at a wavelength of 13.5 nm.

2. The EUV permeable membrane according to claim 1, characterized in that, The thickness of the EUV-permeable membrane is 7–30 nm.

3. The EUV permeable membrane according to claim 1 or 2, characterized in that, The thickness of the beryllium layer is 5–25 nm.

4. The EUV permeable membrane according to claim 1 or 2, characterized in that, The thickness of the first nitride layer and the second nitride layer is 1 to 5 nm.

5. A protective component, characterized in that, have: A substrate having a first surface and a second surface, and having a cavity in the center; An amorphous carbon layer covers the first side of the substrate; as well as The EUV-permeable membrane of claim 1 or 2, wherein the EUV-permeable membrane covers the surface of the amorphous carbon layer opposite to the substrate and is exposed as a self-standing membrane forming the bottom surface of the cavity at the same height as the surface of the amorphous carbon layer.

6. The protective component according to claim 5, characterized in that, The thickness of the amorphous carbon layer is 1–15 nm.

7. The protective component according to claim 5, characterized in that, The substrate is a Si substrate.

8. The protective component according to claim 5, characterized in that, The protective component also includes a mask layer that covers the second side of the substrate.

9. The protective component according to claim 8, characterized in that, The mask layer is a SiO2 layer.

10. An exposure method, characterized in that, The process includes the following steps: Prepare a composite membrane consisting of 5 layers having a protective layer containing amorphous carbon on both sides of the EUV permeable membrane as described in claim 1 or 2. The composite membrane consisting of the five layers is installed in a device that generates hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals. The protective layer is removed by contacting the composite film composed of the five layers with hydrogen plasma and / or hydrogen free radicals, or oxygen plasma and / or oxygen free radicals. as well as An EUV-transmitting film consisting of three layers with the protective layer removed is installed inside an EUV exposure apparatus, allowing EUV to pass through the EUV-transmitting film to perform pattern exposure on the photosensitive substrate inside the EUV exposure apparatus.

Images