Method for manufacturing EUV permeable membrane and pellicle

Abstract

A method is provided for manufacturing a high-quality EUV transparent film or pellicle using an efficient method that is difficult to generate particles by avoiding the mask layer remaining in a sunshade shape extended toward the cavity. The method comprises the steps of: preparing a substrate having a first surface and a second surface; covering the entire area of ​​the first surface and the surrounding area other than the cavity region located at the center of the second surface with a mask layer; partially etching away the substrate exposed to the cavity region to form a cavity; etching away the mask layer covering the first surface; forming an EUV transparent film on the surface of the cavity side of the substrate and the surface of the mask layer covering the second surface; and etching away the substrate from the first surface until the EUV transparent film is exposed to the side opposite to the cavity, thereby making the EUV transparent film in the cavity region a self-supporting film.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing an EUV permeable film and a pellicle. Background Technology

[0002] Miniaturization in semiconductor manufacturing processes is progressing year by year, and various improvements are being made in each process. In particular, in the photolithography process, EUV (extreme ultraviolet) light with a wavelength of 13.5 nm has begun to be used in place of the conventional ArF exposure wavelength of 193 nm. As a result, the wavelength has suddenly become less than 1 / 10, and its optical characteristics have become completely different. However, since there are no materials with high transmittance for EUV light, there is no practical material yet available for a pellicle, which is a particle adhesion barrier for a photomask [reticle]. For this reason, the current situation is that device manufacturers are manufacturing semiconductor devices without being able to use pellicles.

[0003] Therefore, poly Si-based pellicle films have been proposed. For example, Patent Document 1 (Japanese Patent Publication No. 6858817) discloses a pellicle film comprising a core layer that is substantially transparent to EUV radiation, such as (poly) Si, and a cap layer that absorbs IR radiation. However, when the poly Si-based pellicle film is set to a thickness that maintains film strength, the EUV transmittance does not reach 90% of the target, and thus it is not yet practical.

[0004] In addition, carbon nanotube (CNT)-based pellicle films have been developed [e.g., Patent Document 2 (Japanese Patent Publication No. 2018-194840)], and higher EUV transmittance is expected. However, CNT-based pellicle films lack durability against the pellicle usage environment (low-pressure hydrogen atmosphere), and if a metal is coated on the pellicle film to provide durability, the EUV transmittance decreases, making it impossible to achieve a transmittance at a practical level.

[0005] Various methods for manufacturing pellicle films have been proposed. For example, Non-patent Literature 1 (Dario L. Goldfarb, "Fabrication of a full size EUV pellicle based on silicon nitride", Volume 31, Issue 12, PHOTOMASK, SPIE, 2015) discloses a method for manufacturing a SiNx self-supporting film as a pellicle film. The basic method is as follows. First, a SiNx film serving as a pellicle film is deposited on both sides of a Si substrate (Process A). Next, a reactive ion etching (RIE) mask for etching the deposited SiNx is formed on only one side (Process B). A portion of the SiNx is removed by RIE to expose the Si substrate (Process C). After coating both sides of the Si substrate with amorphous Si, the outer shape of the Si substrate is diced (Process D). Finally, using the SiNx film as a mask, the Si substrate is wet-etched to form a SiNx self-standing film (Process E). Prior art literature

[0006] Japanese Patent Publication No. 6858817 and Japanese Patent Publication No. 2018-194840

[0007] Dario L. Goldfarb, "Fabrication of a full size EUV pellicle based on silicon nitride", Volume 31, Issue 12, PHOTOMASK, SPIE, 2015 The problem to be solved

[0008] When attempting to manufacture an EUV transparent film as a pellicle film by referring to a conventional manufacturing method as disclosed in Non-Patent Document 1, it is considered to form an EUV transparent film on a substrate and then remove unnecessary parts of the substrate by etching to form a self-supporting film. An example of such a conventional manufacturing process is illustrated in FIGS. 4a and 4b. In this conventional process, first, a substrate (110), such as a Si wafer, is prepared [Fig. 4a (a)]. A mask layer (112), such as a SiO2 layer, is formed on both sides of this substrate (110). A resist is applied to one or both sides of the substrate (110), and exposure and development are performed to form a resist mask (not shown) for etching so that a hole of the resist of a predetermined size is formed on one side. By etching one side of the substrate (110), the exposed portion of the mask layer (112) is etched away to form an opening corresponding to the cavity region (C) [Fig. 4a (c)]. After removing the resist mask, the substrate (110) is etched with an etching solution such as TMAH (tetramethylammonium hydroxide) solution to thin the cavity region (C) of the substrate (110) to a desired thickness, thereby forming a cavity (114) [Fig. 4a (d)]. The mask layer (112) present on the side opposite the cavity (114) is etched away to obtain a cavity substrate (115) [Fig. 4b (e)]. An EUV transparent film (116) is formed on the side opposite the cavity (114) of the cavity substrate (115) [Fig. 4b (f)]. Finally, the substrate (110) corresponding to the portion to be made into a self-supporting film is etched away to make the EUV transparent film (116) into a self-supporting film [(g) of FIG. 4b]. In this way, a frame (117) including the substrate (110) and mask layer (112) left in a frame shape, and a pellicle (118) having the EUV transparent film (116) are obtained.

[0009] However, in the pellicle (118) produced in this way, as shown in (g) of FIG. 4b and FIG. 4c, the inner edge (112a) of the frame-shaped mask layer (112) remains in a sunshade shape extending toward the cavity (114). This is because when the substrate (110), such as a Si wafer, for forming the cavity (114) is etched from the bottom, as the etching proceeds upward in the drawing, side etching also occurs in the horizontal direction. If the mask layer (112) is left in a state extending toward the cavity (114) in a sunshade shape like this, the sunshade-shaped inner edge (112a), which is weak in strength, breaks, causing particles (dust) to be generated, and the particles are likely to adhere to the EUV transparent film (116). If particles are attached to the EUV transparent film (116), the EUV light is blocked at the particle portion during exposure, resulting in an exposure defect where the mask pattern is not accurately transferred. Meanwhile, removing the mask layer (112) after etching the substrate (110) is considered, but this incurs additional process steps and costs, and since the self-supporting film of the EUV transparent film (116) has already been completed, it leads to the addition of a process with a high risk of damage to the self-supporting film. Therefore, a manufacturing method is desired to avoid the mask layer (112) remaining as a sunshade extending from the cavity (114).

[0010] The inventors have now obtained the insight that by forming an EUV transparent film on the cavity-side surface of a substrate and etching away the substrate from the side opposite to the cavity to make the EUV transparent film self-supporting, the mask layer can be avoided remaining as a sunshade extending toward the cavity, thereby enabling the production of a high-quality EUV transparent film or pellicle using an efficient method that is less likely to generate particles.

[0011] Accordingly, the objective of the present invention is to manufacture a high-quality EUV transparent film or pellicle using an efficient method that is unlikely to generate particles by avoiding the mask layer remaining as a sunshade extending toward the cavity. means of solving the problem

[0012] According to one aspect of the present invention,

[0013] A process for preparing a substrate having a first surface and a second surface, and

[0014] A process of covering the entire area of ​​the first surface and the surrounding area other than the cavity area located at the center of the second surface with a mask layer, and

[0015] A process of forming a cavity by partially etching away the substrate exposed in the cavity region, and

[0016] A process of etching and removing the mask layer covering the first surface, and

[0017] A process of forming an EUV transparent film on the surface of the cavity side of the substrate and on the surface of the mask layer covering the second surface, and

[0018] A process of etching and removing the substrate from the first surface until the EUV transparent film is exposed on the side opposite to the cavity, thereby making the EUV transparent film in the cavity region a self-supporting film.

[0019] A method for manufacturing an EUV permeable film including is provided.

[0020] According to another aspect of the present invention,

[0021] A process for preparing a substrate having a first surface and a second surface, and

[0022] A process of covering the entire area of ​​the first surface and the surrounding area other than the cavity area located at the center of the second surface with a mask layer, and

[0023] A process of forming a cavity by partially etching away the substrate exposed in the cavity region, and

[0024] A process for etching and removing the mask layer covering the first surface and the mask layer covering the surrounding area of ​​the second surface, and

[0025] A process of forming an EUV transparent film on the cavity-side surface of the above substrate, and

[0026] A process of etching and removing the substrate from the first surface until the EUV transparent film is exposed on the side opposite to the cavity, thereby making the EUV transparent film in the cavity region a self-supporting film.

[0027] A method for manufacturing an EUV permeable film including is provided.

[0028] According to another aspect of the present invention,

[0029] A substrate having a first surface and a second surface, and also having a cavity in the center, and

[0030] A mask layer covering the second surface of the above substrate, and

[0031] An EUV transparent film exposed as a self-supporting film that continuously covers the surface of the mask layer and the inner surface of the cavity of the substrate, and also constitutes the bottom surface of the cavity at the same height as the first surface.

[0032] A pellicle equipped with is provided.

[0033] According to another aspect of the present invention,

[0034] A substrate having a first surface and a second surface, and also having a cavity in the center, and

[0035] An EUV transparent film exposed as a self-supporting film that continuously covers the second surface of the substrate and the inner surface of the cavity, and also constitutes the bottom surface of the cavity at the same height as the first surface.

[0036] A pellicle equipped with is provided. Brief explanation of the drawing

[0037] FIG. 1a is a diagram illustrating an example of the first half of the process in a method for manufacturing an EUV permeable film according to one embodiment of the present invention. FIG. 1b is a drawing illustrating an example of a later process following FIG. 1a in a method for manufacturing an EUV permeable film according to one embodiment of the present invention. FIG. 1c is a drawing illustrating another example of the latter process following FIG. 1a in a method for manufacturing an EUV transparent film according to one embodiment of the present invention. FIG. 2a is a diagram illustrating another example of the overall process in the method for manufacturing an EUV permeable film according to the present invention. FIG. 2b is a diagram illustrating an example of a later process following FIG. 2a in a method for manufacturing an EUV permeable film according to the present invention. FIG. 3a is a diagram illustrating an example of the overall process in a method for manufacturing an EUV transparent film using an SOI substrate according to the present invention. FIG. 3b is a diagram illustrating an example of the latter process following FIG. 3a in the method for manufacturing an EUV transparent film using an SOI substrate according to the present invention. FIG. 4a is a diagram illustrating the overall process of a method for manufacturing an EUV transparent film according to the prior art. FIG. 4b is a diagram illustrating the latter process following FIG. 4a of a method for manufacturing an EUV transparent film according to the prior art. FIG. 4c is an SEM image of a portion of the pellicle [region enclosed by solid lines (4C)] shown in FIG. 4b (g) observed from the mask layer toward the bottom of the cavity. Specific details for implementing the invention

[0038] Method for manufacturing an EUV permeable film

[0039] The method for manufacturing an EUV transparent film according to the present invention comprises each of the following steps: (1) preparation of a substrate, (2) formation of a mask layer, (3) formation of a cavity, (4) removal of the mask layer, (5) formation of an EUV transparent film, and (6) self-supporting of the EUV transparent film. In the present invention, an EUV transparent film is formed on the cavity-side surface of the substrate, and the EUV transparent film is made self-supporting by etching away the substrate from the side opposite to the cavity. By doing so, the mask layer is avoided from remaining as a sunshade extending toward the cavity, thereby enabling the manufacture of a high-quality EUV transparent film or pellicle using an efficient method that is less prone to particle generation. The details thereof will be clarified in the following description.

[0040] FIGS. 1a to 4b illustrate a method for manufacturing an EUV transparent film according to several embodiments of the present invention. With reference to these figures, each process will be described below.

[0041] (1) Preparation of the substrate

[0042] As illustrated in FIG. 1a(a) and FIG. 2a(a), a substrate (10) is prepared. The substrate (10) has a first surface (10a) and a second surface (10b). The second surface (10b) is the side where a cavity is formed in a subsequent process, and the first surface (10a) is the side where a cavity is not formed in a subsequent process. The substrate (10) is a support for forming an EUV transparent film (16) thereon, but ultimately, in order to make the EUV transparent film (16) self-supporting, the cavity region (C) is etched away, and the surrounding region (P) is left as a frame. Accordingly, the substrate (10) is desired to be a material that can be etched away, providing a desirable substrate for forming the EUV transparent film (16). Such a substrate (10) is not particularly limited, but is preferably a Si substrate (e.g., a Si wafer).

[0043] The substrate (10) may be an SOI (Silicon on Insulator) substrate. As shown in (a) of FIG. 3a, the SOI substrate (10') is composed of a Si substrate (10c), a SiO2 layer (10d), and a Si layer (10e), with the SiO2 layer (10d) interposed between the Si substrate (10c) and the Si layer (10e). In this case, the first surface (10a) is the surface of the Si layer (10e), and the second surface (10b) is the surface of the Si substrate (10c). By using the SOI substrate (10'), the etching can be accurately stopped at the SiO2 layer (10d) during the etching (Si etching) of the Si substrate (10c). For this reason, there is an advantage in that it is easy to avoid problems caused by excessive Si etching [e.g., sagging of the self-supporting film caused by the substrate (10) becoming too thin].

[0044] (2) Formation of the mask layer

[0045] As illustrated in FIGS. 1a (b) and (c) and FIGS. 2a (b) and (c), the entire area of ​​the first surface (10a) and the surrounding area (P) other than the cavity area (C) located in the center of the second surface (10b) on the substrate (10) are covered by a mask layer (12). The mask layer (12) is not particularly limited as long as it is made of a material that is corrosion-resistant to the wet etching solution used for etching the substrate (10) (e.g., TMAH used for Si etching). A preferred mask layer (12) is a SiO2 film. The mask layer (12) may be formed by any method. For example, the formation of the SiO2 film is preferably carried out by chemical vapor deposition (CVD) or thermal oxidation. In addition, the thickness of the SiO2 film is preferably 100 to 1000 nm.

[0046] The formation of the mask layer (12) can be performed as follows. First, a mask layer (12) is formed on the first surface (10a) and the second surface (10b) of the substrate (10) [Fig. 1a (b) and Fig. 2a (b)]. Next, a resist is applied to the first surface (10a) and the second surface (10b), and exposure and development are performed so that an opening of the resist corresponding to a cavity region (C) is created on the second surface (10b) side, thereby forming a resist mask (not shown). The size of the cavity region (C) corresponds to the size of the EUV transparent film (16) to be manufactured. After etching away the exposed portion of the mask layer (12) at the opening of the resist mask by wet etching with an etching solution such as hydrofluoric acid, the resist mask is removed. In this way, a mask layer (12) having an opening in the cavity region (C) is obtained [(c) of FIG. 1a and (c) of FIG. 2a].

[0047] (3) Formation of the cavity

[0048] As shown in FIG. 1a (d) and FIG. 2a (d), the substrate (10) exposed to the cavity region (C) is partially etched away to form a cavity (14). That is, the cavity region (C) of the substrate (10) is removed by etching after an EUV transparent film (16) is formed thereon. Therefore, in order to perform etching efficiently in a short time, it is desired to thin the thickness of the substrate (10) in the region [i.e., the cavity region (C)] where the self-supporting film is to be formed in advance. For this reason, the cavity region (C) of the substrate (10) is thinned by etching the substrate (10) from the opening of the mask layer (12) to form a cavity (14). The etching of the substrate (10) may be either wet etching or dry etching and is not particularly limited. The etchant is not particularly limited as long as it is capable of etching the substrate (10). For example, when etching is performed using the DeepRIE method, which is a dry process, as shown in (d) of FIG. 1a, the Si substrate is etched perpendicularly to the mask layer (12), so it is preferable in that the mask layer (12) is less likely to remain in a sunken shape. When wet etching of the Si substrate is performed, a TMAH (tetramethylammonium hydroxide) solution is preferable. If the TMAH solution is used under appropriate conditions, very good etching can be achieved through anisotropic etching of Si. In particular, anisotropic etching can be said to be more advantageous than isotropic etching in that, when forming the cavity (14), the etching can be performed with straightness in the thickness direction of the substrate (10) [making it difficult to go around directly under the mask layer (12)], so the mask layer (12) is less likely to remain in a sunken shape.Nevertheless, when wet etching is performed, as shown in (d) of FIG. 2a, the Si substrate is etched not only in the vertical direction but also in the horizontal direction as the liquid flows in, so the mask layer (12) may temporarily remain in a sunshade shape. However, in the embodiment shown in FIG. 2a and FIG. 2b, the mask layer (12) is removed in a subsequent process as shown in (e) of FIG. 2b, so the mask layer (12) remaining in a sunshade shape can be avoided.

[0049] When using an SOI substrate (10'), the formation of the cavity (14) is preferably performed by etching away the Si substrate (10c) until the cavity (14) reaches the SiO2 layer (10d) [Fig. 3a (d)], as shown in FIG. 3a (d) and FIG. 3b (e), and then etching away the SiO2 layer (10d) separately from the cavity (14) [Fig. 3b (e)]. The etching of the Si substrate (10c) may be performed by either dry etching or wet etching as described above. In this embodiment, since the etching can be stopped precisely at the SiO2 layer (10d), problems caused by excessive Si etching [e.g., sagging of the self-supporting film resulting from the substrate (10) becoming excessively thin] can be avoided. Afterward, the etching removal of the exposed SiO2 layer (10d) within the cavity (14) is preferably performed using hydrofluoric acid. In this way, the Si layer (10e) is exposed as a self-supporting film within the cavity (14).

[0050] (4) Removal of mask layer

[0051] As illustrated in (e) of FIG. 1b, the mask layer (12) covering the first surface (10a) is etched away. In this way, a substrate (10) [i.e., a cavity substrate (15)] having a cavity (14) is obtained. The etching away of the mask layer (12) can be performed by wet etching with an etching solution such as hydrofluoric acid, as described above. In this way, a cavity substrate (15) having a cavity (14) is obtained. The mask layer (12) covering the peripheral region (P) of the second surface (10b) can be left intact. That is, in a subsequent film deposition process, an EUV transparent film (16) can be deposited over the mask layer (12) covering the peripheral region (P) of the second surface (10b). This makes it possible to omit the mask removal process.

[0052] However, as a modified mode, the mask layer (12) covering the surrounding area (P) of the second surface (10b) may also be etched away. That is, as shown in (e') of FIG. 1c and (e) of FIG. 2b, both the mask layer (12) covering the first surface (10a) and the mask layer (12) covering the surrounding area (P) of the second surface (10b) may be etched away. By etching away the mask layer (12) covering the surrounding area (P) of the second surface (10b), the mask layer (12) is completely eliminated, so the mask layer (12) remaining in a sunshade form can be avoided.

[0053] Even when using an SOI substrate (10'), as shown in (f) of FIG. 3b, the mask layer (12) covering the first surface (10a) can be etched and removed in the same way as above.

[0054] (5) Formation of EUV permeable membrane

[0055] As shown in (f) of FIG. 1b, an EUV transparent film (16) is formed on the surface of the second surface (10b) and the surface of the mask layer (12) covering the cavity (14) side of the substrate (10). Alternatively, in a modified form as shown in (f') of FIG. 1c and (f) of FIG. 2b, an EUV transparent film (16) is formed on the surface of the cavity (14) side of the substrate (10). That is, in conventional methods, the EUV transparent film (16) has been formed on a flat surface opposite to the side where the cavity (14) is formed, but in the present invention, the film is formed from the non-flat surface on the side where the cavity (14) is formed [or from above the mask layer (12) if there is a mask layer thereon]. The advantages associated with this will be described later in the following process.

[0056] It is preferable that the EUV transparent film (16) has a main layer composed of at least one metal selected from the group consisting of Ni, Al, Be, Cr, and Ga. These metals have the advantage of being difficult to erode by XeF2 gas when the EUV transparent film (16) is formed by etching a substrate (10), such as a Si substrate, with XeF2 gas. This is supported by the fact that the boiling points of the respective fluorides of Ni, Al, Be, Cr, and Ga are very high, at 1750°C (NiF2), 1260°C (AlF3), 1169°C (BeF2), 1100°C (CrF2), and 950°C (GaF3), compared to the boiling point of XeF2, which is 114°C. This is because a high boiling point indicates a low vapor pressure, which means it is difficult to etch with XeF2 gas. From the perspective of an EUV transparent film, a particularly desirable main layer is composed of Be (metallic beryllium). Since Be has a higher EUV transmittance than Si or C, it exhibits a high EUV transmittance (e.g., 93% or more) at a practical level. Additionally, from the perspective of protecting the main layer, it is desirable for the EUV transparent film (16) to further have a protective layer covering at least one side (preferably both sides) of the main layer. When the main layer is composed of Be, preferred examples of materials constituting the protective layer include beryllium nitride, beryllium oxide, and beryllium fluoride.

[0057] The formation of the EUV transparent film (16) may be performed by any film deposition method. Examples of preferred film deposition methods include sputtering or CVD (chemical vapor deposition). As described above, in the present invention, film deposition is performed on the non-flat surface on the side where the cavity (14) of the substrate (10) is formed. However, even with a film deposition method that has poor penetration sensitivity such as sputtering, the substrate (10), such as a Si substrate, typically has a thickness of 1 mm or less, so there is no significant difference in film thickness compared to the case where film is deposited on a flat surface, even if it is on the inner surface of the cavity (14).

[0058] For example, when fabricating a three-layer structure of beryllium nitride / beryllium / beryllium nitride, it is preferable to fabricate the beryllium film as the main layer by sputtering using a pure Be target, and to perform the beryllium nitride film as the protective layer by reactive sputtering. This reactive sputtering can be performed, for example, by introducing nitrogen gas into the chamber during sputtering using a pure Be target, so that beryllium and nitrogen react to produce beryllium nitride. As described below, the beryllium nitride film may have a gradient composition layer (a layer consisting of a nitrogen concentration gradient region described below) in which the nitrogen concentration decreases toward the beryllium film. An example of a preferred sequence in this case is as follows. First, beryllium nitride is deposited by performing Be sputtering while introducing nitrogen gas in addition to Ar, which is normally used as an atmosphere gas. After forming a beryllium nitride film of a predetermined thickness, a gradient composition layer is formed by performing Be sputtering while reducing the amount of nitrogen gas. At the point where the gradient composition layer is formed, the introduction of subsequent nitrogen gas is stopped, and a beryllium layer is formed to a predetermined thickness. Subsequently, the gradient composition layer is formed again while increasing the amount of nitrogen gas introduced, and a beryllium nitride film is formed again as the outermost layer by reactive sputtering.

[0059] In addition, as another method, beryllium nitride can be produced by forming a beryllium film and then irradiating the beryllium with nitrogen plasma to cause a nitridation reaction to produce beryllium nitride. In any case, the synthesis methods for beryllium nitride are not limited to these. Also, while it is preferable to use different beryllium targets for forming the beryllium nitride film and the beryllium film, it is also possible to use the same target for both the beryllium nitride film and the beryllium film. Furthermore, the beryllium nitride film and the beryllium film may be formed using a single-chamber sputtering apparatus as described in the examples below, or the beryllium nitride film and the beryllium film may be formed in separate chambers using a two-chamber sputtering apparatus.

[0060] Even when using an SOI substrate (10'), as shown in (g) of FIG. 3b, an EUV transparent film (16) can be formed on the surface of the mask layer (12) covering the cavity (14) side of the SOI substrate (10') and the second surface (10b) in the same manner as above.

[0061] (6) Self-supporting membrane of EUV permeable membrane

[0062] As illustrated in (g) of FIG. 1b, (g') of FIG. 1c, and (g) of FIG. 2b, the substrate (10) is etched away from the first surface (10a) until the EUV transparent film (16) is exposed to the side opposite the cavity (14), thereby making the EUV transparent film (16) in the cavity region (C) self-supporting. Thus, the etching of the substrate (10) (e.g., a Si substrate) to make the EUV transparent film (16) self-supporting is performed from the flat surface opposite the cavity (14) of the substrate (10), unlike the conventional process in which the etching of the substrate (10) is performed from the inner surface of the cavity (14). This brings about several advantages as follows.

[0063] First, since the EUV transparent film (16) has resistance to the etchant (or has a protective film that has resistance to the etchant), it functions as a protective film on the surface of the cavity (14) of a substrate (10), such as a Si substrate, thereby preventing the substrate (10) on the inner surface of the cavity (14) from being side-etched. In this way, it is possible to prevent the mask layer (12) from remaining in a sunshade shape. That is, as described above, in the conventional process, side-etching occurs on the side of the cavity (14), and as a result, as shown in (g) of FIG. 4b and FIG. 4c, there was a problem that the mask layer (112) remained in a sunshade shape extending toward the cavity (114). If left in this state, the inner edge (112a) of the sunshade shape, which is weak in strength, breaks, generating particles (dust), and the particles become prone to adhering to the EUV transparent film (116). If particles are attached to the EUV transparent film (116), the EUV light is blocked at the particle portion during exposure, resulting in an exposure defect where the mask pattern is not accurately transferred. In contrast, the method of the present invention prevents side etching because the cavity (14) or the mask layer (12) is covered by the EUV transparent film (16), thereby preventing the mask layer (12) from remaining in a sunshade shape. Additionally, removing the mask layer (12) after etching the substrate (10) is considered, but this incurs additional process steps and costs, and since the self-supporting film of the EUV transparent film (16) has already been completed, it leads to the addition of a process with a high risk of damage to the self-supporting film. The method of the present invention eliminates the need for such an additional process.

[0064] Secondly, since the etching of the substrate (10) is performed on a flat surface without a cavity (14), compared to etching from the side of the cavity (14) of the substrate (10), it is difficult for etching non-uniformity caused by the difference in shape between the flat part and the non-flat part (corner part, etc.) to occur, and uniform etching becomes possible. That is, in the etching from the inner surface of the cavity (14) in the conventional process, etching non-uniformity depending on the location occurred due to the diffusion non-uniformity of the etchant, etc., but in the method of the present invention, since the EUV transparent film (16) can be made into a self-supporting film by etching on a flat surface, it is difficult for etching non-uniformity to occur. Therefore, according to the method of the present invention, a high-quality EUV transparent film (16) or pellicle (18) can be manufactured.

[0065] Thus, according to the method of the present invention, by avoiding the mask layer (12) remaining in a sunshade shape extended toward the cavity (14), a high-quality EUV transparent film or pellicle can be manufactured using an efficient method that is difficult to generate particles.

[0066] It is preferable that the etching of the substrate (10) to make the EUV transparent film (16) self-supporting be performed by an etching method that does not erode the EUV transparent film (16). For example, when etching a Si substrate, it is preferable to perform the etching with XeF2 gas.

[0067] Even when using an SOI substrate (10'), as shown in (h) of FIG. 3b, the self-supporting film of the EUV transparent film (16) can be etched away from the first surface (10a) by removing the SOI substrate (10') [specifically the Si layer (10e)] in the same manner as above until the EUV transparent film (16) is exposed to the side opposite the cavity (14). As a result of making the EUV transparent film (16) in the cavity region (C) self-supporting in this way, the self-supporting portion of the EUV transparent film (16) and the SiO2 layer (10d) are exposed on the same plane opposite the cavity (14). In this embodiment, since there is a SiO2 layer (10d) below the Si layer (10e), the etching can be stopped at the SiO2 layer (10d) without strictly managing the etching time in XeF2 etching to remove the Si layer (10e).

[0068] In this way, as a result of etching away the substrate (10) or SOI substrate (10'), the EUV transparent film (16) in the cavity region (C) becomes a self-supporting film. Meanwhile, in the surrounding region (P) other than the cavity region, three layers of the substrate (10), mask layer (12), and EUV transparent film (16) [(g) in FIG. 1b], two layers of the substrate (10) and EUV transparent film (16) [(g') in FIG. 1c and (g) in FIG. 2b], or four layers of SiO2 layer (10d), Si substrate (10c), mask layer (12), and EUV transparent film (16) [(h) in FIG. 3b] are left to form a frame (17) for supporting the self-supporting film. In this way, a pellicle (18) having the EUV transparent film (16) (pellicle film) and the frame (17) is obtained.

[0069] Pellicle

[0070] As described above, an EUV permeable film and a pellicle equipped with the same are manufactured by the manufacturing method of the present invention.

[0071] As illustrated in (g) of FIG. 1b, a pellicle (18) according to one embodiment of the present invention comprises a substrate (10), a mask layer (12), and an EUV transparent film (16). The substrate (10) has a first surface (10a) and a second surface (10b), and also has a cavity (14) in the center. The mask layer (12) covers the second surface (10b) of the substrate (10). The EUV transparent film (16) continuously covers the surface of the mask layer (12) and the inner surface of the cavity (14) of the substrate (10), and is also exposed as a self-supporting film that forms the bottom surface of the cavity (14) at the same height as the first surface (10a).

[0072] As illustrated in (g') of FIG. 1c and (g) of FIG. 2b, a pellicle (18') according to another aspect of the present invention comprises a substrate (10) and an EUV transparent film (16). The substrate (10) has a first surface (10a) and a second surface (10b), and also has a cavity (14) in the center. The EUV transparent film (16) continuously covers the second surface (10b) of the substrate (10) and the inner surface of the cavity (14), and is also exposed as a self-supporting film that forms the bottom surface of the cavity (14) at the same height as the first surface (10a).

[0073] In any embodiment, the substrate (10) may be composed of two layers, such as the pellicle (18'') shown in (h) of FIG. 3b, a Si substrate (10c) and a SiO2 layer (10d). This is a typical layer configuration in a pellicle (18'') manufactured using an SOI substrate (10').

[0074] As described above, the pellicle (18, 18' or 18'') has an EUV transparent film (16) (pellicle film) and a frame (17). The frame (17) is composed of three layers of a substrate (10), a mask layer (12) and an EUV transparent film (16) [(g) in FIG. 1b], two layers of a substrate (10) and an EUV transparent film (16) [(g') in FIG. 1c and (g) in FIG. 2b], or three or four layers of a SiO2 layer (10d), a Si substrate (10c), a mask layer (12) (optional), and an EUV transparent film (16) [(h) in FIG. 3b].

[0075] Preferred embodiment of an EUV permeable membrane

[0076] As described above, an EUV transparent film according to a preferred embodiment comprises a main layer and a protective layer covering at least one side (preferably both sides) of the main layer. In this embodiment, the main layer is preferably composed of metal beryllium, while the protective layer is preferably composed of beryllium nitride. Thus, by combining a main layer composed of metal beryllium and a protective layer composed of beryllium nitride, it is possible to provide an EUV transparent film that combines a high practical level of EUV transmittance (e.g., 93% or more) and durability in a low-pressure hydrogen atmosphere environment.

[0077] The main layer according to the present embodiment is preferably composed of metal beryllium. However, the main layer does not need to be entirely composed of metal beryllium; it is sufficient if the main layer is composed of at least 99 weight%, more preferably at least 99.5 weight%, and even more preferably at least 99.8 weight% of metal beryllium. It contributes to the realization of a high practical level of EUV transmittance while securing basic functions as a pellicle film (such as particle adhesion prevention function). In this regard, the thickness of the main layer is preferably 10 to 70 nm, more preferably 15 to 50 nm, and even more preferably 20 to 35 nm.

[0078] The protective layer according to the present embodiment is a layer for protecting the main layer, which is a metal beryllium layer. Accordingly, the protective layer may cover at least one side of the main layer, but it is preferable to cover both sides of the main layer with the protective layer. The protective layer is preferably composed of beryllium nitride. However, the protective layer does not need to be entirely composed of beryllium nitride; it is sufficient if 99 weight percent or more, preferably 99.5 weight percent or more, and more preferably 99.8 weight percent or more of the protective layer is composed of beryllium nitride. Since beryllium nitride has a high EUV transmittance, when compared at the same thickness, the EUV transmittance is higher than that of a beryllium film with a Ru layer formed thereon. According to theoretical calculations, the transmittance is 85.8% when a Ru film with a thickness of 3 nm is formed on both sides of a beryllium film with a thickness of 30 nm, but the transmittance is 91.1% when a beryllium nitride film with a thickness of 3 nm is formed on both sides of a beryllium film with a thickness of 30 nm. When a beryllium nitride layer with a thickness of 2 nm and a gradient composition layer with a thickness of 1 nm (a layer consisting of a nitrogen concentration gradient region described later) are formed on both sides of a beryllium film with a thickness of 30 nm, the transmittance exceeds 91.1%. By forming a dense beryllium nitride layer on both sides of the beryllium layer, the reaction with XeF2 gas used for etching the Si substrate described later can be suppressed. In addition, since beryllium is a highly reactive material, it is easily oxidized to form beryllium oxide, but oxidation can be suppressed by the formation of beryllium nitride. As described above, the advantages of using a beryllium nitride layer as a protective layer are increased EUV transmittance, protection of the beryllium film (main layer) during the etching process, and prevention of oxidation.

[0079] The thickness of the protective layer according to the present embodiment is preferably 5 nm or less, and more preferably 3 nm or less. When considering the deposition of a protective layer with a thickness of 3 nm on both sides of the main layer, the EUV transmittance of the 3 nm thick beryllium nitride film is 95%, which is significantly higher than that of the Ru film at 90%. Although the lower limit of the thickness of the protective layer is not particularly limited, if it is excessively thin, it becomes difficult to cover the entire surface of the main layer, or the crystallinity of the beryllium nitride deteriorates, making it difficult to obtain the physical properties of beryllium nitride; therefore, it is typically 1 nm or more. Furthermore, in this specification, the term "beryllium nitride" refers not only to stoichiometric compositions such as Be3N2, but also to Be3N 2-x (food 0 <x<2임)와 같은 비화학량론 조성도 허용하는 포괄적인 조성을 의미하는 것으로 한다.

[0080] It is desirable for the protective layer to have a nitrogen concentration gradient region in which the nitrogen concentration decreases as it approaches the main layer. That is, as mentioned above, the composition of the beryllium nitride constituting the protective layer includes Be3N from a stoichiometric composition such as Be3N2. 2-x(food 0 <x<2임)와 같은 비화학량론 조성까지 포함할 수 있는 바, 보호층을 구성하는 질화베릴륨이, 주층에 근접함에 따라 베릴륨 리치의 조성에 근접하는 경사 조성으로 하는 것이 바람직하다. 이렇게 함으로써, 보호층(즉 질화베릴륨층)과 주층(즉 금속베릴륨층)의 밀착성을 향상시킬 수 있고, 양층 사이의 열팽창차에서 기인하는 응력의 발생을 완화할 수 있다. 즉, 양층 사이의 밀착성을 향상시켜 박리를 억제하거나, EUV광을 흡수하여 고온이 된 경우의 양층 사이의 열팽창 완화층으로서 박리되기 어렵게 하거나 할 수 있다. 질소 농도 경사 영역의 두께는, 보호층의 두께보다 작은 것이 바람직하다. 즉, 보호층의 두께의 전역이 질소 농도 경사 영역일 필요는 없다. 예컨대, 보호층의 두께의 일부만, 예컨대, 보호층의 두께 중 바람직하게는 10∼70%의 영역, 보다 바람직하게는 15∼50%의 영역이 질소 농도 경사 영역인 것이 바람직하다.

[0081] The EUV transparent film (16) according to the present embodiment may have an EUV transmittance of a high practical level, preferably 91% or more, more preferably 92% or more, and even more preferably 93% or more. Since a higher EUV transmittance is desirable, the upper limit is not specifically limited, but the EUV transmittance of the EUV transparent film (16) according to the present embodiment may typically be 99% or less, more typically 98% or less, and even more typically 95% or less.

[0082] Examples

[0083] The present invention will be explained in more detail by the following examples.

[0084] Example 1

[0085] A composite self-supporting membrane (EUV permeable membrane) with a three-layer structure of beryllium nitride / beryllium nitride / beryllium nitride was fabricated as follows, in accordance with the order shown in FIGS. 1a and 1b.

[0086] (1) Preparation of cavity substrate

[0087] A Si wafer with a diameter of 8 inches (20.32 cm) was prepared as a substrate (10) [Fig. 1a (a)]. On both sides of this Si wafer, a SiO2 layer with a thickness of 1 μm was formed by thermal oxidation as a mask layer (12) [Fig. 1a (b)]. A resist was applied to both sides of the Si wafer with the formed SiO2 layer, and exposure and development were performed to form a resist mask (not shown) for SiO2 etching, such that a hole of the resist measuring 110 mm × 140 mm was created as a cavity region (C) on one side. By wet etching one side of this substrate with hydrofluoric acid, the exposed portion of the SiO2 film in the cavity region (C) was etched away to expose the Si wafer, and then the resist mask was removed using an ashing device [Fig. 1a (c)]. After that, a Si wafer was dry-etched (anisotropic etched) in the thickness direction using reactive ion etching from the exposed portion of the cavity region (C) to form a cavity (14) [Fig. 1a (d)]. At this time, the etching time was determined in advance from the etching rate so that the thickness of the Si wafer remaining as the bottom portion of the cavity (14) was about 10 μm, and etching was performed for that amount of etching time. The SiO2 layer on the side opposite to the cavity (14) was removed and cleaned with hydrofluoric acid to prepare a cavity substrate (15) for forming an EUV transparent film [Fig. 1b (e)].

[0088] (2) Formation of a composite membrane

[0089] A composite film of a three-layer structure of beryllium nitride / beryllium / beryllium nitride was formed as follows on the cavity (14) forming surface of the cavity substrate (15) obtained in (1) above, over the entire area including not only the cavity region (C) [inner surface of the cavity (14)] but also the surrounding region (P) (SiO2 layer) [f of FIG. 1b]. First, the cavity substrate (15) was set up in a sputtering device and a pure Be target was attached. The inside of the chamber was vacuumed, and reactive sputtering was performed at an internal pressure of 0.5 Pa by adjusting the flow rate ratio of argon gas to nitrogen gas to 1:1, and the reactive sputtering was terminated when the time for 2 nm of beryllium nitride to be deposited was determined. Subsequently, sputtering was performed with only argon gas without introducing nitrogen gas, and the sputtering was terminated when the time for 25 nm of beryllium to be deposited was determined. After that, reactive sputtering was performed by introducing nitrogen gas again as before, and the reactive sputtering was terminated by determining the time for 2 nm of beryllium nitride to be deposited. In this way, a composite film of 2 nm of beryllium nitride / 25 nm of beryllium nitride / 2 nm of beryllium nitride was formed as an EUV transparent film (16).

[0090] (3) Self-supporting membrane

[0091] A cavity substrate (15) having the EUV transparent film (16) obtained in (2) above was set up in the chamber of a XeF2 etcher so that the side opposite to the cavity (14) [i.e., the exposed side of the Si substrate (10)] would be etched with XeF2, and the inside of the chamber was sufficiently vacuumed. At this time, if moisture remained in the chamber, it would react with the XeF2 gas to generate hydrofluoric acid, which would cause corrosion of the etcher or etching beyond the expected state, so sufficient vacuuming was performed. If necessary, the inside of the chamber was vacuumed and nitrogen gas was introduced repeatedly to reduce residual moisture. When sufficient vacuuming was achieved, the valve between the XeF2 raw material cylinder and the pre-chamber was opened. As a result, XeF2 sublimated and XeF2 gas accumulated in the pre-chamber. When sufficient XeF2 gas had accumulated in the pre-chamber, the valve between the pre-chamber and the chamber was opened to introduce XeF2 gas into the chamber. XeF2 gas reacted with Si to produce SiF4 and Xe. Since the boiling point of SiF4 is -95°C, the generated SiF4 evaporated rapidly, and a reaction occurred between the newly exposed Si substrate and F. As Si etching proceeded and the amount of XeF2 in the chamber decreased, the inside of the chamber was vacuumed, and XeF2 gas was introduced into the chamber again to perform etching. In this way, vacuuming, introduction of XeF2 gas, and etching were repeated until the Si substrate (10) corresponding to the portion to be formed into a self-supporting film was lost. Etching was terminated when the unnecessary portion of the Si substrate was removed. In this way, a pellicle (18) equipped with a composite self-supporting film of an EUV transparent film (16) and a frame (17) supporting the composite self-supporting film was obtained [Fig. 1b (g)]. The EUV transmittance of the obtained beryllium nitride / beryllium / beryllium nitride three-layer composite self-supporting film was measured to be 92.8%.

[0092] Example 2

[0093] According to the order shown in FIGS. 2a and 2b, a composite self-supporting membrane (EUV permeable membrane) with a three-layer structure of beryllium nitride / beryllium / beryllium nitride was fabricated as follows.

[0094] (1) Preparation of cavity substrate

[0095] A Si wafer with a diameter of 8 inches (20.32 cm) was prepared as a substrate (10) [Fig. 2a (a)]. On both sides of this Si wafer, a SiO2 layer with a thickness of 1 μm was formed by thermal oxidation as a mask layer (12) [Fig. 2a (b)]. A resist was applied to both sides of the Si wafer with the formed SiO2 layer, and exposure and development were performed to form a resist mask (not shown) for SiO2 etching, such that a hole of the resist measuring 110 mm × 140 mm was created as a cavity region (C) on one side. By wet etching one side of this substrate with hydrofluoric acid, the exposed portion of the SiO2 film in the cavity region (C) was etched away to expose the Si wafer, and then the resist mask was removed using an ashing device [Fig. 2a (c)]. Afterwards, a Si wafer was wet-etched (anisotropic etched) in the thickness direction with TMAH solution from the exposed portion of the cavity region (C) to form a cavity (14) [Fig. 2a (d)]. At this time, the etching time was determined in advance from the etching rate so that the thickness of the Si wafer remaining as the bottom portion of the cavity (14) was about 10 μm, and etching was performed for that amount of etching time. At this time, the etching with TMAH solution is anisotropic etching and proceeds mainly in the upward direction in the drawing, but etching also proceeds in the horizontal direction. Therefore, as shown in Fig. 2a (d), the mask layer (12) forms a sunshade structure. Thus, the mask layer (12) on both sides of the substrate was removed and cleaned with hydrofluoric acid to prepare a cavity substrate (15') for forming an EUV transparent film [Fig. 2b (e)].

[0096] (2) Formation of a composite membrane

[0097] On the cavity (14) forming surface of the cavity substrate (15') obtained in (1) above, a composite film of a three-layer structure of beryllium nitride / beryllium / beryllium nitride was formed as an EUV transparent film (16) in the same manner as in Example 1 [(f) of FIG. 2b], over the entire area including not only the cavity region (C) [inner surface of the cavity (14)] but also the surrounding region (P).

[0098] (3) Self-supporting membrane

[0099] The cavity substrate (15') having the EUV transparent film (16) obtained in (2) above was set in the chamber of the XeF2 etcher so that the side opposite to the cavity (14) [i.e., the exposed side of the Si substrate (10)] was XeF2 etched, and XeF2 etching was performed in the same manner as in Example 1. In this way, by etching away the Si substrate (10) at the bottom of the cavity (14), a pellicle (18') having a composite self-supporting film of the EUV transparent film (16) and a frame (17) supporting the composite self-supporting film was obtained [(g) of FIG. 2b]. At this time, unlike Example 1, in Example 2 the mask layer (12) is removed, so a shading structure by the mask layer (12) is not created, and thus the mask layer (12) is not damaged and does not generate particles. The EUV transmittance of the obtained beryllium nitride / beryllium nitride / beryllium nitride three-layer composite self-supporting film was measured and found to be 93.1%.

[0100] Example 3

[0101] A composite self-supporting membrane (EUV permeable membrane) with a three-layer structure of beryllium nitride / beryllium nitride / beryllium nitride was fabricated as follows, in accordance with the order shown in Figs. 3a and 3b.

[0102] (1) Preparation of cavity substrate

[0103] As a substrate (10'), an SOI substrate was prepared in which a SiO2 layer (10d) (insulator layer) with a thickness of 1 μm and a Si layer (10e) (SOI layer) with a thickness of 10 μm were formed in sequence on a Si substrate (10c) [Fig. 3a (a)]. On both sides of this SOI substrate (10'), a SiO2 layer with a thickness of 1 μm was formed by thermal oxidation as a mask layer (12) [Fig. 3a (b)]. A resist was applied to both sides of the SOI substrate (10') on which the SiO2 layer was formed, and exposure and development were performed to form a resist mask (not shown) for SiO2 etching, such that a hole of the resist with a thickness of 110 mm × 140 mm was formed as a cavity region (C) on one side. By wet etching one side of the substrate with hydrofluoric acid, the exposed portion of the SiO2 film in the cavity region (C) was etched away to expose the SOI substrate (10'), and then the resist mask was removed with an ashing device [Fig. 3a (c)]. After that, the Si substrate (10c) from the exposed portion of the cavity region (C) was dry etched (anisotropic etched) by reactive ion etching until the SiO2 layer (10d) was exposed in the thickness direction, thereby forming a cavity (14) [Fig. 3a (d)]. The exposed SiO2 layer (10d) was etched away with hydrofluoric acid to expose the Si layer (10e) [Fig. 3b (e)]. After that, the mask layer (12) (SiO2 layer) on the side opposite the cavity (14) was etched away with hydrofluoric acid to prepare a cavity substrate (15'') for forming an EUV transparent film [(f) of FIG. 3b].

[0104] (2) Formation of a composite membrane

[0105] A composite film of a three-layer structure of beryllium nitride / beryllium nitride / beryllium nitride was formed as an EUV transparent film (16) in the same manner as in Example 1 on the cavity (14) forming surface of the cavity substrate (15'') obtained in (1) above, including not only the cavity region (C) [inner surface of the cavity (14)] but also the surrounding region (P) (SiO2 layer). [(g) of FIG. 3b].

[0106] (3) Self-supporting membrane

[0107] The cavity substrate (15'') having the EUV transparent film (16) obtained in (2) above was set in the chamber of a XeF2 etcher so that the side opposite to the cavity (14) [i.e., the exposed side of the Si layer (10e)] was XeF2 etched, and XeF2 etching was performed in the same manner as in Example 1. In this way, by etching away the Si layer (10e) at the bottom of the cavity (14), a pellicle (18'') having a composite self-supporting film of the EUV transparent film (16) and a frame (17) supporting the composite self-supporting film was obtained [(h) of FIG. 3b]. At this time, unlike in Example 1, in Example 3, since a SiO2 layer (10d) exists below the Si layer (10e), the etching can be stopped at the SiO2 layer (10d) without strictly managing the etching time in XeF2 etching to remove the Si layer (10e). This is advantageous in that it prevents excessive etching. The EUV transmittance of the obtained beryllium nitride / beryllium / beryllium nitride three-layer structure composite self-supporting film was measured and found to be 93.3%.

[0108] Results and Discussion

[0109] In Examples 1 to 3, since the mask layer (SiO2 layer in Examples 1 to 3) for forming a cavity in the substrate and the inner surface of the cavity are coated with a beryllium nitride / beryllium / beryllium nitride composite film, the inner surface of the cavity is not etched by XeF2 etching. In other words, side etching does not occur. In Examples 1 to 3, since the Si thickness of the cavity bottom is 10 μm, if a conventional method is used, side etching of about 10 μm occurs, resulting in a sunshade structure where the mask layer extends toward the cavity. If the mask layer becomes a sunshade structure, the mask layer is composed of SiO2 with a thickness of only 1 μm, so its strength is low and it breaks easily. Furthermore, when it breaks, particles (dust) are generated and adhere to the self-supporting film. When a self-supporting film is used as a pellicle film, if particles adhere to the self-supporting film, the EUV light is blocked at the particle portion during exposure, resulting in an exposure defect where the mask pattern is not accurately transferred. In this regard, since the self-supporting film produced in the present invention does not have a shading structure formed therein, the problem of the shading structure being damaged and adhering to the self-supporting film does not occur.

Claims

Claim 1 A method for manufacturing an EUV transparent film comprises: a process of preparing a substrate having a first surface and a second surface; a process of covering a surrounding area other than a cavity region located at the center of the second surface and the entire area of ​​the first surface with a mask layer; a process of partially etching away the substrate exposed to the cavity region to form a cavity; a process of etching away the mask layer covering the first surface; a process of forming an EUV transparent film on the surface of the substrate on the cavity side and on the surface of the mask layer covering the second surface; and a process of etching away the substrate from the first surface until the EUV transparent film is exposed to the side opposite to the cavity, thereby making the EUV transparent film in the cavity region a self-supporting film, wherein the EUV transparent film comprises a main layer composed of at least one metal selected from the group consisting of Ni, Al, Be, and Ga. Claim 2 A method for manufacturing an EUV transparent film according to claim 1, wherein the EUV transparent film comprises a main layer composed of metal beryllium. Claim 3 A method for manufacturing an EUV transparent film according to paragraph 2, wherein the EUV transparent film comprises a protective layer covering at least one side of the main layer. Claim 4 A method for manufacturing an EUV transparent film according to claim 1, wherein the substrate is a Si substrate. Claim 5 A method for manufacturing an EUV transparent film according to claim 1, wherein the substrate is an SOI substrate, and the SOI substrate is composed of a Si substrate, a Si layer, and a SiO2 layer interposed between the Si substrate and the Si layer, and the first surface is the surface of the Si layer, and the second surface is the surface of the Si substrate. Claim 6 A method for manufacturing an EUV transparent film according to claim 5, wherein the formation of the cavity is performed by etching away the Si substrate until the cavity reaches the SiO2 layer, and then separately etching away the SiO2 layer from the cavity, and as a result, the self-supporting portion of the EUV transparent film and the SiO2 layer are exposed on the same plane opposite to the cavity. Claim 7 A pellicle comprising: a substrate having a first surface and a second surface and also having a cavity in the center; a mask layer covering the second surface of the substrate; and an EUV transparent film exposed as a self-supporting film that continuously covers the surface of the mask layer and the inner surface of the cavity of the substrate and also forms the bottom surface of the cavity at the same height as the first surface, wherein the EUV transparent film comprises a main layer composed of at least one metal selected from the group consisting of Ni, Al, Be, and Ga. Claim 8 A pellicle described in paragraph 7, manufactured by the method of any one of paragraphs 1 to 6. Claim 9 A method for manufacturing an EUV transparent film comprises: a process of preparing a substrate having a first surface and a second surface; a process of covering a surrounding area other than a cavity region located at the center of the second surface and the entire area of ​​the first surface with a mask layer; a process of partially etching away the substrate exposed to the cavity region to form a cavity; a process of etching away the mask layer covering the first surface and the mask layer covering the surrounding area of ​​the second surface; a process of forming an EUV transparent film on the cavity-side surface of the substrate; and a process of etching away the substrate from the first surface until the EUV transparent film is exposed to the side opposite to the cavity, thereby making the EUV transparent film in the cavity region a self-supporting film, wherein the EUV transparent film comprises a main layer composed of at least one metal selected from the group consisting of Ni, Al, Be, and Ga. Claim 10 In claim 9, the method for manufacturing an EUV transparent film comprises a main layer composed of metal beryllium. Claim 11 A method for manufacturing an EUV transparent film according to claim 10, wherein the EUV transparent film comprises a protective layer covering at least one side of the main layer. Claim 12 A method for manufacturing an EUV transparent film according to claim 9, wherein the substrate is a Si substrate. Claim 13 A method for manufacturing an EUV transparent film according to claim 9, wherein the substrate is an SOI substrate, and the SOI substrate is composed of a Si substrate, a Si layer, and a SiO2 layer interposed between the Si substrate and the Si layer, and the first surface is the surface of the Si layer, and the second surface is the surface of the Si substrate. Claim 14 A method for manufacturing an EUV transparent film according to claim 13, wherein the formation of the cavity is performed by etching away the Si substrate until the cavity reaches the SiO2 layer, and then separately etching away the SiO2 layer from the cavity, and as a result, the self-supporting portion of the EUV transparent film and the SiO2 layer are exposed on the same plane opposite to the cavity. Claim 15 A pellicle comprising a substrate having a first surface and a second surface and a cavity in the center, and an EUV transparent film exposed as a self-supporting film that continuously covers the second surface of the substrate and the inner surface of the cavity and also forms the bottom surface of the cavity at the same height as the first surface, wherein the EUV transparent film comprises a main layer composed of at least one metal selected from the group consisting of Ni, Al, Be, and Ga. Claim 16 A pellicle described in paragraph 15, manufactured by the method of any one of paragraphs 9 through 14.

Images