JP7839673B2 - Pellicle - Google Patents

Description

This invention relates to a pellicle . More specifically, it relates to a pellicle in which a frame can be easily joined to a pellicle material .

In photolithography, a technology used in the manufacturing process of semiconductor devices, a resist is applied to a semiconductor wafer, and then a photomask is used to expose specific areas of the applied resist to create a resist pattern of the desired shape on the semiconductor wafer. When irradiating the resist with exposure light, a dustproof cover called a pellicle is used to cover the photomask, preventing foreign matter from adhering to it.

The pellicle comprises a pellicle membrane, a border supporting the pellicle membrane, and a frame joined to the border. The border contains pores reaching the pellicle membrane. The frame and border have substantially the same shape when viewed in plan. Suitable materials for the pellicle membrane are those with high transmittance to exposure light and high resistance to exposure light (less deterioration and deformation at high temperatures). In this specification, the portion of the pellicle excluding the frame may be referred to as the pellicle material.

In semiconductor device manufacturing processes, the miniaturization of semiconductor devices has led to increased demand for miniaturization of photolithography technology. In recent years, the mainstream use of light sources such as KrF (krypton fluoride) excimer lasers (248 nm) and ArF (argon fluoride) excimer lasers (193 nm) as exposure light sources has become prevalent. Furthermore, the use of even shorter wavelength light sources, such as EUV (Extreme Ultra Violet) light (13.5 nm), is also being considered.

When using KrF or ArF excimer lasers as light sources, organic thin films are used as the pellicle film. However, when the wavelength of the exposure light becomes shorter, such as with EUV light, the energy absorbed by the pellicle film from the exposure light increases. Therefore, in photolithography using EUV light, the use of inorganic thin films with high transmittance and high resistance to EUV light is being considered. These types of inorganic thin films include Si (silicon), SiN (silicon nitride), C (carbon) (graphite, graphene, diamond-like carbon (DLC), amorphous carbon, carbon nanotubes (CNTs), etc.), and SiC (silicon carbide).

Techniques related to the manufacturing method of pellicle membranes are disclosed, for example, in the following Patent Documents 1 and 2.

Patent Document 1 discloses a method for manufacturing a compound semiconductor substrate, comprising the steps of forming a SiC film on the surface of a Si substrate and removing at least a portion of the back surface of the Si substrate by wet etching. In the step of removing at least a portion of the back surface of the Si substrate, the Si substrate and the SiC film are moved relative to the chemical solution used for wet etching.

Patent Document 2 discloses a pellicle comprising a pellicle film and a support material for supporting the pellicle film. The pellicle film is made of DLC, amorphous carbon, graphite, carbon nanotubes (CNTs), or silicon carbide, etc. The pellicle frame is made of silicon or a metal, etc. This pellicle is manufactured by shaping a support material by etching a substrate, and then forming the pellicle film on the substrate.

The following pellicle manufacturing method is disclosed in Patent Document 3: A pellicle film holding portion is provided on an SOI (Silicon On Insulator) substrate with a silicon crystal film formed on one main surface. The support substrate is removed from the other main surface side of the SOI substrate, leaving the silicon crystal film as the pellicle film.

Japanese Patent Publication No. 2017-218358 International Publication No. 2014/187710 Japanese Patent Publication No. 2009-116284

As the pellicle film becomes thinner, its transmittance increases, but its mechanical strength decreases, making it more susceptible to damage. When the pellicle film is thin, the pellicle material is manufactured using the following method: A pellicle film is formed on the surface of a Si-containing border. Next, holes reaching the pellicle film are formed in the border by wet etching. By employing wet etching as the method for forming holes in the border, damage to the pellicle film can be suppressed.

Furthermore, the etching speed of dry etching is significantly slower than that of wet etching. Therefore, using dry etching to form holes in the border is disadvantageous from a manufacturing cost perspective. Also, if the pellicle film is thin, attempting to form holes in the border by mechanical grinding will damage the pellicle film due to the force applied. Therefore, using mechanical grinding to form holes in the border is difficult. Moreover, if the pellicle film is thin, attempting to join the border containing the holes to the pellicle film will damage the pellicle film due to the force applied. Therefore, employing a manufacturing method that involves forming holes in the border and then joining the border containing the holes to the pellicle film is difficult.

When manufacturing a pellicle using pellicle material, a process is carried out to join the frame to the pellicle material's border. The position of the frame relative to the pellicle material's border is industrially controlled. Specifically, the frame's position relative to the border is adjusted so that the center of gravity of the inner surface of the holes in the border aligns with the center of gravity of the inner surface of the holes in the frame. Furthermore, the frame's position relative to the border is adjusted so that, when viewed in plan, the inner surface of the holes in the border aligns with the inner surface of the holes in the frame. Afterward, the frame is joined to the border.

The wet etching method used to form holes in the border is isotropic etching. The inner surface of the holes in the border has a complex shape because it is eroded during wet etching. Due to this complex shape, adjusting the position of the frame relative to the border was difficult when joining the frame to the border. As a result, conventional pellicle materials had the problem of not being easy to join frames to.

Furthermore, to prevent erosion during wet etching, a method of forming a protective film (a passivation film to prevent erosion) on the inner surface of the holes in the border could be considered. However, with this method, it was difficult to geometrically form the passivation film in the desired position. In addition, this method would lead to increased costs due to the increased manufacturing process. Therefore, this method was not practical.

The present invention aims to solve the above problems, and its objective is to provide a pellicle that allows for easy joining of a frame to the pellicle material .

A pellicle according to one aspect of the present invention comprises a pellicle material and a frame, which are joined to a photomask via a frame , wherein the pellicle material comprises a pellicle film having one main surface and another main surface, a first support having a first hole and made of a silicon-containing material, the first support supporting the pellicle film from the other main surface side of the pellicle film, a second support having a second hole connected to the first hole, and a joining layer joining the first support and the second support , the second support being a member for joining to the photomask via a frame, the other main surface of the pellicle film exposed at the bottom of the first hole, and when viewed in cross-section cut by a plane perpendicular to one main surface of the pellicle film, the width of the first hole increases from the pellicle film side of the first support to the second support side of the first support , and further comprises another joining layer joining the second support and the frame .
Preferably, in the above pellicle, the bonding layer includes an amorphous layer containing silicon.
Preferably, in the above-described pellicle, the pellicle film comprises at least one material selected from the group consisting of silicon, carbon, boron, and nitrogen.
Preferably, in the above-described pellicle, the total thickness of the first support, the bonding layer, and the second support is greater than 0 and 1 mm or less.
Preferably, in the above pellicle, the arithmetic mean roughness Ra of the first support side of the second support is greater than 0 and 2 nm or less.
Preferably, the pellicle further comprises a mask layer formed on the second support side of the first support, wherein the mask layer is insoluble in at least one of a chemical solution containing an acid and hydrofluoric acid that have an oxidizing effect on silicon, and an alkaline aqueous solution composed only of components that do not have an oxidizing effect on silicon.
Preferably, the pellicle described above includes a silicon oxide layer with a thickness of 1 nm to 15 μm.
Preferably, in the above pellicle, the bonding layer includes a sintered glass body with a thickness of 0.5 μm to 100 μm.
Preferably, in the above pellicle, when the first support is viewed from the side facing the second support, the contour line of the inner surface of the first hole in the first support includes each of the first, second, third, and fourth linear portions extending in a linear manner, the first linear portion and the second linear portion being parallel to each other, and the third linear portion and the fourth linear portion being parallel to each other; when the second support is viewed from the side opposite to the side facing the first support, the contour line of the inner surface of the second hole in the second support includes each of the fifth, sixth, seventh, and eighth linear portions extending in a linear manner, the fifth linear portion and the sixth linear portion being parallel to each other, and the seventh linear portion and the eighth linear portion being parallel to each other; and the arithmetic mean roughness Ra of the inner surface of the first hole in the first support is greater than the arithmetic mean roughness Ra of the inner surface of the second hole in the second support.
Preferably, in the above-described pellicle, when the pellicle material is viewed from the second support side, the entire inner circumferential surface of the first hole in the first support is covered by the second support.
Preferably, in the above-described pellicle, at least a portion of the surface of the second support facing the first support faces the inner circumferential surface of the first hole in the first support.
Preferably, in the above-described pellicle, when viewed in cross-section cut by a plane perpendicular to one main surface of the pellicle film, the width of the first pore from the pellicle film side of the first support to the second support side of the first support is always greater than or equal to the width of the second pore.
Preferably, the pellicle further comprises a recess formed by the inner circumferential surface of the first hole in the first support and the surface of the second support facing the first support.

According to the present invention, it is possible to provide a pellicle in which a frame can be easily joined to the pellicle material .

This is a cross-sectional view showing the structure of the pellicle 1 when it is cut with a plane perpendicular to the main surface 11a of the pellicle film 11, according to one embodiment of the present invention. This is a plan view showing the configuration of the border 12 and the sub-border 13. This is a cross-sectional view showing the first step of a method for manufacturing the pellicle 1 according to one embodiment of the present invention. This is a cross-sectional view showing a second step in a method for manufacturing the pellicle 1 according to one embodiment of the present invention. This is a cross-sectional view showing a third step in a method for manufacturing a pellicle 1 according to one embodiment of the present invention, and moreover, it shows how a border 12 and a sub-border 13 are joined using glass frit. This is a cross-sectional view showing a first modification of the third step of a method for manufacturing a pellicle 1 in one embodiment of the present invention, and shows how the border 12 and the sub-border 13 are joined using a surface activation bonding method. This is a cross-sectional view showing a second modification of the third step of the method for manufacturing the pellicle 1 in one embodiment of the present invention, and shows how the border 12 and the sub-border 13 are joined using a hydrophilic bonding method. This is a cross-sectional view showing the fourth step of a method for manufacturing the pellicle 1 according to one embodiment of the present invention. This is a cross-sectional view showing the fifth step of a method for manufacturing the pellicle 1 according to one embodiment of the present invention. This is a plan view showing a fifth step in a method for manufacturing the pellicle 1 according to one embodiment of the present invention, and is a plan view showing the adjustment of the position of the frame 15 with respect to the subborder 13. This is a partial cross-sectional view showing the configuration of the pellicle 1 in first and second modified examples of one embodiment of the present invention. This is a partial cross-sectional view showing the configuration of the pellicle 1 in third and fourth modified examples of one embodiment of the present invention.

The embodiments of the present invention will be described below with reference to the drawings. In this specification, the expression "formed on a surface" means that it is formed in contact with that surface. The expression "formed on the surface side" means both that it is formed in contact with that surface and that it is formed without contact with that surface (at a distance from that surface). The sizes of each component shown in the drawings are conceptual sizes and may differ from the actual dimensions of each component.

Figure 1 is a cross-sectional view showing the structure of the pellicle 1 when cut with a plane perpendicular to the main surface 11a of the pellicle film 11 in one embodiment of the present invention. Figure 1(a) is a cross-sectional view showing the overall structure of the pellicle 1. Figure 1(b) is an enlarged cross-sectional view of the area near the border 12 (part A in Figure 1(a)).

Referring to Figure 1, the pellicle 1 (an example of a pellicle) in this embodiment is a pellicle mainly used in photolithography using EUV light. The pellicle 1 prevents foreign matter from adhering to the photomask PM (an example of a photomask) by covering the photomask PM. The pellicle 1 comprises a pellicle material 2 (an example of a pellicle material), a frame 15 (an example of a frame), and a bonding layer 16, etc. The pellicle material 2 is a material bonded to the photomask PM via the frame 15. The pellicle material 2 includes a pellicle film 11 (an example of a pellicle film), a border 12 (an example of a first support), a sub-border 13 (an example of a second support), and a bonding layer 14 (an example of a bonding layer), etc.

The pellicle film 11 includes two main surfaces 11a (an example of one main surface of the pellicle film) and 11b (an example of the other main surface of the pellicle film) facing opposite directions. The pellicle film 11 is made of any material. Preferably, the pellicle film 11 contains at least one material selected from the group consisting of Si, C, B (boron), and N (nitrogen). More preferably, the pellicle film 11 contains Si and C. The pellicle film 11 may include a film made of a carbon-based material such as carbon nanotubes, diamond, diamond-like carbon, amorphous carbon, graphite, graphene, or carbon silicide. The pellicle film 11 may include a film made of a silicon-based material such as single-crystal Si, polycrystalline Si, amorphous Si, metal silicide, single-crystal SiC, polycrystalline SiC, or amorphous SiC. The pellicle film 11 may also include a film made of BN. The pellicle film 11 may include a film made of SiN. The pellicle film 11 may also include multiple films. For example, the pellicle film 11 may include a main film made of, for example, single-crystal SiC, and a protective film made of, for example, a carbon-based material, formed on at least one of the two main surfaces of the main film.

The border 12 supports the pellicle membrane 11 from the main surface 11b side, for example, the outer peripheral end of the pellicle membrane 11. The border 12 includes a hole 121 (an example of a first hole) and has a closed curved planar shape surrounding the hole 121. The border 12 further includes two main surfaces 12a and 12b facing opposite directions, an inner peripheral surface 12c of the hole 121, and an outer peripheral surface 12d. Main surface 12a is the surface facing the pellicle membrane 11, and main surface 12b is the surface facing the sub-border 13. The pellicle membrane 11 is formed on the main surface 12a side of the border 12. The main surface 11b of the pellicle membrane 11 is exposed at the bottom of the hole 121. The outer peripheral surface 12d of the border 12 extends perpendicularly to each of the main surfaces 12b and 13b.

The border 12 is made of a material containing Si, and is preferably made of Si. The border 12 may also contain an _SiO2 (silicon oxide) film or a SiN film. If the border 12 is made of Si, the main surface 12a of the border 12 may have an exposed (100) plane, (111) plane, or (110) plane of Si.

The sub-border 13 is a member for joining to the photomask PM via the frame 15. The sub-border 13 is joined to the border 12. The sub-border 13 is provided on the main surface 12b side of the border 12 via the joining layer 14. The sub-border 13 includes a hole 131 (an example of a second hole) and has a closed curved planar shape surrounding the hole 131. The hole 131 is connected to the hole 121 of the border 12. The border 12 and the sub-border 13 have similar shapes when viewed in plan. The sub-border 13 includes two main surfaces 13a and 13b facing opposite directions, an inner circumferential surface 13c of the hole 131, and an outer circumferential surface 13d. Main surface 13a is the surface on the border 12 side, and main surface 13b is the surface on the frame 15 side. The outer circumferential surface 13d of the sub-border 13 extends perpendicularly to each of the main surfaces 12b and 13b. When viewing the pellicle material 2 from the main surface 13b side, the outer circumferential surface 13d of the sub-border 13 and the outer circumferential surface 12d of the border 12 are located in overlapping positions.

The sub-border 13 is made of any material. The sub-border 13 is a component for joining to the photomask PM via the frame 15, and is not a component directly joined to the photomask PM.

The bonding layer 14 is the layer that joins the border 12 and the sub-border 13. The bonding layer 14 is the trace of the joining of the border 12 and the sub-border 13. The bonding layer 14 is formed between the main surface 12b of the border 12 and the main surface 13a of the sub-border 13. The composition of the bonding layer 14 varies depending on the joining method between the border 12 and the sub-border 13.

Due to structural constraints of the EUV exposure apparatus, the total thickness w of the border 12, sub-border 13, and bonding layer 14 is greater than 0 and less than or equal to 1 mm.

The frame 15 is joined to the sub-border 13. The frame 15 is provided on the main surface 13b side of the sub-border 13 via a joining layer 16. The frame 15 includes a hole 151 and has a closed curved planar shape surrounding the hole 151. The hole 151 connects to the hole 131 in the sub-border 13. The sub-border 13 and the frame 15 have substantially the same shape when viewed in plan. The frame 15 includes two main surfaces 15a and 15b facing opposite directions, and the inner circumferential surface 15c of the hole 151. Main surface 15a is the surface facing the sub-border 13, and main surface 15b is the surface facing the photomask PM.

The frame 15 is made of any material, for example, aluminum. The frame 15 is a component directly bonded to the photomask PM. The frame 15 has a thickness of at least 1 mm.

The sub-border 13 and frame 15 are distinguished by whether or not they are directly bonded to the photomask PM, and whether or not they have a thickness exceeding 1 mm.

The holes 121 in the border 12, 131 in the sub-border 13, and 151 in the frame 15 constitute one hole in the pellicle 1 that reaches the pellicle membrane 11. The hole in the pellicle 1 formed by holes 121, 131, and 151 may be a single hole, as shown in Figure 1, or it may be multiple holes. If multiple holes are formed, they may be arranged in a mesh pattern.

The bonding layer 16 is the layer that joins the sub-border 13 and the frame 15. The bonding layer 16 is the trace of the joining between the sub-border 13 and the frame 15. The bonding layer 16 is formed between the main surface 13b of the sub-border 13 and the main surface 15a of the frame 15. The composition of the bonding layer 16 varies depending on the joining method between the sub-border 13 and the frame 15.

When viewing the pellicle material 2 from the main surface 13b side, it is preferable that the entire inner circumferential surface 12c of the border 12 is covered by the sub-border 13, and the inner circumferential surface 12c of the border 12 is not visible. It is preferable that at least a portion of the main surface 13a (the surface on the border 12 side) of the sub-border 13 faces the inner circumferential surface 12c of the hole 121 in the border 12. When viewed in the cross-section of Figure 1, it is preferable that the width d1 of the hole 121 from the main surface 12a (the surface on the pellicle film 11 side) to the main surface 12b (the surface on the sub-border 13 side) of the border 12 is always greater than or equal to the width d2 of the hole 131. Furthermore, it is preferable that a recess 17 (an example of a recess) is formed, consisting of the inner circumferential surface 12c of the hole 121 in the border 12 and the main surface 13a of the sub-border 13. The recess 17 extends from the inner circumferential surface 13c of the hole 131 toward the outer circumferential end of the pellicle material 2 (to the left in Figure 1(b)).

Figure 2 is a plan view showing the configuration of the border 12 and the sub-border 13. Figure 2(a) is a plan view showing the configuration of the border 12 as seen from the main surface 12b side. Figure 2(b) is a plan view showing the configuration of the sub-border 13 as seen from the main surface 13b side.

Referring to Figures 1 and 2, each of the pellicle membrane 11, border 12 and holes 121, and sub-border 13 and holes 131 have an arbitrary planar shape, such as a circular, elliptical, or polygonal shape. In this embodiment, each of the pellicle membrane 11, border 12 and holes 121, and sub-border 13 and holes 131 have a substantially rectangular shape.

In particular, as shown in Figure 2(a), when viewed from the main surface 12b of the border 12 (the surface on the sub-border 13 side), the contour line of the inner circumferential surface 12c of the hole 121 in the border 12 includes linear portions 126, 127, 128, and 129 (examples of the first, second, third, and fourth linear portions), which are linearly extending parts. Linear portions 126 and 127 are parallel to each other. Linear portions 128 and 129 are parallel to each other. Each of the intersections of linear portions 126 and 128, linear portion 126 and 129, linear portion 127 and 128, and linear portion 127 and 129 constitutes one of the four corners of the rectangle of the hole 121.

In particular, as shown in Figure 2(b), when viewed from the main surface 13b of the subborder 13 (the surface opposite to the surface on the border 12 side), the contour line of the inner circumferential surface 13c of the hole 131 in the subborder 13 includes linear portions 136, 137, 138, and 139 (examples of the 5th, 6th, 7th, and 8th linear portions), which are linearly extending parts. Linear portions 136 and 137 are parallel to each other. Linear portions 138 and 139 are parallel to each other. The inner circumferential surface 13c of the hole 131 in each of the linear portions 136, 137, 138, and 139 extends linearly. Each of the intersections of straight section 136 and straight section 138, straight section 136 and straight section 139, straight section 137 and straight section 138, and straight section 137 and straight section 139 forms an angle with a radius of curvature R of less than 0.5 mm.

Because the holes 121 are formed by wet etching, which is an isotropic etching process, the inner surface 12c of the holes 121 is eroded during the wet etching process. Specifically, when viewed in the cross-section of Figure 1, the width d1 of the holes 121 increases from the main surface 12a (the surface on the pellicle film 11 side) of the border 12 to the main surface 12b (the surface on the sub-border 13 side). The shape of the inner surface 12c of the holes 121 when viewed in the cross-section of Figure 1 is also called a "shoreline shape." The inner surface 12c of the holes 121 in the border 12 has a more complex shape compared to the inner surface 13c of the holes 131 in the sub-border 13.

On the other hand, the width d2 of the hole 131 is constant throughout the entire sub-border 13, from the main surface 13a to the main surface 13b. The arithmetic mean roughness Ra of the inner surface 12c of the hole 121 in the border 12 is greater than the arithmetic mean roughness Ra of the inner surface 13c of the hole 131 in the sub-border 13.

The arithmetic mean roughness Ra is defined in JIS (Japanese Industrial Standards) B 0601. The arithmetic mean roughness Ra is measured at four points on the surface being measured using a 3D measuring laser microscope "LEXT OLS4000" (manufactured by Olympus Corporation) under the following conditions: evaluation length: 4 mm, cutoff: λc 800 μm, λs 2.5 μm, λf none, filter: Gaussian filter, analysis parameters: roughness parameters, objective lens: ×50.

Next, the manufacturing method of the pellicle 1 in this embodiment will be explained using Figures 3 to 10.

Referring to Figure 3, prepare a plate-shaped border 12 without holes.

Next, the pellicle film 11, including the main surfaces 11a and 11b, is formed on the main surface 12a of the border 12. The border 12 supports the pellicle film 11 from the side of its main surface 11b.

Specifically, a pellicle film 11 that contacts the main surface 12a of the border 12 is epitaxially grown. If the pellicle film 11 is made of SiC, it is deposited on a SiC underlayer obtained, for example, by carbonizing the main surface 12a of the border 12, using methods such as MBE (Molecular Beam Epitaxy) or CVD (Chemical Vapor Deposition). Alternatively, the pellicle film 11 may be deposited on the main surface 12a of the border 12 using methods such as MBE or CVD.

In particular, when the pellicle film 11 is made of SiC epitaxially grown on the main surface 12a of the border 12, the pellicle film 11 is made of polycrystalline SiC or single-crystal SiC (3C-SiC) having a 3C-type crystal structure. When the pellicle film 11 is made of SiC, it has a thickness of 10 nm to 100 nm, preferably 15 nm to 30 nm.

After the pellicle film 11 is formed, a protective film 92, for example made of Si, is formed on the main surface 11a of the pellicle film 11.

Next, a mask layer 91 made of SiC or the like is formed on the outer periphery of the main surface 12b of the border 12. Using the mask layer 91 as a mask, the central RG1 of the main surface 12b of the border 12 is removed. The removal of the central RG1 is performed by any method, such as mechanical polishing including sandblasting.

As a result of removing the central RG1, a hole 122 (an example of a first hole) is formed in the main surface 12b of the border 12, with the material constituting the border 12 as its base. The hole 122 has a depth that does not penetrate the border 12. Due to the presence of the hole 122, the thickness of the central part of the border 12 becomes thinner than the thickness of the outer edges of the border 12.

Furthermore, the pellicle film 11 and protective film 92 may be formed after the holes 122 have been formed.

Referring to Figure 4, after the formation of the pellicle film 11, the bottom surface RG2 of the hole 122, which is part of the border 12, is removed by wet etching. As a result of removing the bottom surface RG2, hole 122 becomes hole 121. The main surface 11b of the pellicle film 11 is exposed at the bottom surface of hole 121. By employing wet etching as the method for removing the bottom surface RG2, damage to the pellicle film 11 during the removal of the bottom surface RG2 can be suppressed. Alternatively, hole 121 may be formed on the plate-shaped border 12 using only wet etching, without forming hole 122 by any other method.

After forming the holes 121, the mask layer 91 is removed as needed. The mask layer 91 can be removed at any time after the formation of the central RG1. The removal of the mask layer 91 is not always necessary. For example, SiC may be used as the mask layer 91, and its thickness may be made sufficiently thin. In this case, after forming the holes 121 in the border 12 using wet etching, only the portion of the mask layer 91 in contact with the main surface 12b of the border 12 remains. The portion of the mask layer 91 protruding inward from the main surface 12b of the border 12 is automatically removed during wet etching. Therefore, removal of the mask layer 91 becomes unnecessary.

For wet etching of the bottom surface RG2, a mixed acid containing oxidizing acids such as hydrofluoric acid and nitric acid, or an aqueous solution of potassium hydroxide (KOH) can be used. To prevent etching of the pellicle film 11 and to improve the quality of the pellicle film 11, it is preferable to use a mixed acid consisting of hydrofluoric acid and nitric acid as the wet etching solution for the border 12.

During wet etching of the bottom surface RG2, the portion RG3 of the inner circumferential surface 12c of the hole 121 in the border 12 is removed along with the bottom surface RG2 of the hole 122 in the border 12. Removal of the portion RG3 results in a tapered shape for the hole 121. That is, the width d1 of the hole 121 (Figure 1) increases from the main surface 12a to the main surface 12b of the border 12.

When wet etching the bottom surface RG2, it is preferable to move the pellicle film 11 and border 12 relative to the chemical solution used for wet etching. In particular, to avoid damage to the pellicle film 11 due to pressure from the chemical solution while the pellicle film 11 and border 12 are being moved, it is preferable to move the pellicle film 11 and border 12 in a direction within a plane parallel to the main surface 11a of the pellicle film 11. Spin etching is the most preferred method of wet etching.

When removing the bottom surface RG2 by spin etching, the border 12 is fixed so that the main surface 12b side (mask layer 91 side) faces upward. The pellicle film 11 and border 12 are then rotated around a rotation axis extending perpendicular to the main surface 12b. While the pellicle film 11 and border 12 are rotated in this manner without changing their positions, the etching solution used for wet etching is injected into the bottom surface RG2 of the hole 122. The rotation speed of the pellicle film 11 and border 12 is set to, for example, approximately 500 to 1500 rpm.

In particular, when the pellicle film 11 is thin, roughness of the reaction surface of the border 12 adversely affects the pellicle film 11. Specifically, roughness of the reaction surface of the border 12 applies uneven stress to the pellicle film 11, making it easy for cracks to form in the pellicle film 11 or for the pellicle film 11 to peel off from the border 12 during wet etching.

During wet etching of the bottom surface RG2, by moving the pellicle film 11 and border 12 relative to the chemical solution used for wet etching, it is possible to suppress the local accumulation of the chemical solution and bubbles on the reaction surface of the border 12, thereby suppressing roughness of the reaction surface of the border 12. As a result, it is possible to suppress the application of non-uniform stress to the pellicle film 11, and to thin the pellicle film 11 without damaging it.

In particular, when spin etching is used as the wet etching method for the bottom surface RG2, the main surface 11a of the pellicle film 11 is not exposed to the chemical solution during wet etching. Therefore, damage to the pellicle film 11 by the chemical solution can be minimized. As a result, damage to the pellicle film 11 can be suppressed, and the pellicle film 11 can be made thinner.

On the other hand, when spin etching is used as the wet etching method for the bottom surface RG2, the chemical solution injected into the bottom surface RG2 of hole 122 collides with the inner circumferential surface 12c of hole 122 in the border 12 due to the centrifugal force of rotation. The inner circumferential surface 12c of hole 122 in the border 12 becomes particularly susceptible to erosion. The volume of the portion RG3 removed at the inner circumferential surface 12c of hole 122 in the border 12 increases. The increase in the width d1 of hole 121 from the main surface 12a to the main surface 12b of the border 12 becomes larger.

The mask layer 91 only needs to be made of a material that is insoluble in at least one of the following: a chemical solution containing an acid and hydrofluoric acid that have an oxidizing effect on Si, and an alkaline aqueous solution composed only of components that do not have an oxidizing effect on Si. This protects the main surface 12b, which is the bonding surface, during spin etching of the bottom surface RG2, and maintains the flatness of the main surface 12b. The mask layer 91 may be made of, for example, SiC, SiN, _SiO2 , or photoresist.

Referring to Figure 5, a sub-border 13 is prepared with a support substrate 93 provided on its main surface 13b. Next, the border 12 and the sub-border 13 are joined together, connecting the holes 121 in the border 12 to the holes 131 in the sub-border 13. The method of joining the border 12 and the sub-border 13 is arbitrary. Examples of joining methods include glass frit joining, fusion joining, surface activation joining, plasma joining, or joining using an adhesive. When joining the border 12 and the sub-border 13 using an adhesive, it is preferable to use a resin-based adhesive such as acrylic resin or epoxy resin. To achieve good joining, the arithmetic mean roughness Ra of the main surface 13a (the surface on the border 12 side) of the sub-border 13 is preferably greater than 0 and 2 nm or less. The arithmetic mean roughness Ra of the main surface 12b (the surface on the sub-border 13 side) of the border 12 is preferably greater than 0 and 2 nm or less. Note that the support substrate 93 is not required on the sub-border 13.

Here, the border 12 and the sub-border 13 are joined using glass frit in the following manner. Glass frit 141 (an example of glass frit) is applied to at least one of the main surfaces 12b of the border 12 (the surface facing the sub-border 13) and the main surface 13a of the sub-border 13 (the surface facing the border 12), for example, using a screen printing method. Next, the main surface 12b of the border 12 and the main surface 13a of the sub-border 13 are bonded together via the applied glass frit 141, as indicated by arrow AR2. After bonding, the glass frit 141 is heated to melt it (in other words, the glass frit 141 is sintered). After sintering, the glass frit 141 becomes a bonding layer 14 containing a sintered glass body. This bonding layer 14 has a thickness of 0.5 μm to 100 μm. Preferably, this bonding layer 14 has a thickness of 1 μm to 20 μm.

Alternatively, after heating the glass frit 141 to melt it, the main surface 12b of the border 12 and the main surface 13a of the sub-border 13 may be bonded together via the glass frit 141.

Furthermore, if spin etching is used as the wet etching method for the bottom surface RG2, and glass frit is applied to the main surface 12b of the border 12, the glass frit may be applied to the main surface 12b of the border 12 before spin etching.

By employing glass frit bonding, a strong bond can be achieved. Therefore, even when the pellicle material 2 is subjected to force during bonding of the frame 15 to the pellicle material 2 or during the movement of the pellicle 1 during exposure, the bond between the border 12 and the sub-border 13 is maintained. By employing glass frit bonding, high durability at high temperatures up to approximately 800°C can be achieved. Furthermore, since glass frit does not contain organic materials such as adhesives, it does not become a source of contamination by releasing gases in the exposure atmosphere (for example, in a reduced-pressure hydrogen atmosphere of approximately 5 Pa). In addition, when glass frit is applied using a screen printing method, the bonding throughput can be improved, and the manufacturing cost of the pellicle material 2 can be reduced.

Referring to Figure 6, the border 12 and the sub-border 13 may be joined using a surface activation bonding method in the following way: A protective film 146 is formed on the main surface 11b of the pellicle film 11. Examples of the protective film 146 include resist and very thin polycrystalline Si. When resist is used as the protective film 146, or when the surface roughness of the polycrystalline Si is large, it is preferable to selectively remove the protective film 146 on the main surface 12b of the border 12 before bonding. Then, in a reduced pressure atmosphere of 1 × ^10⁻⁵ Pa or less, preferably 1 × ^10⁻⁶ Pa or less, and at room temperature (for example, a temperature of 10°C to 30°C), energy particles are irradiated onto the main surface 12b of the border 12 (the surface on the sub-border 13 side) and the main surface 13a of the sub-border 13 (the surface on the border 12 side), as shown by arrow AR3. In this step, the protective film 146 formed on the main surface 11b of the pellicle film 11 is also irradiated with energy particles. Irradiation with energy particles removes adsorbed substances such as gas, water, organic matter, or oxygen from the main surface 12b of the border 12 and the main surface 13a of the sub-border 13. The energy particles consist of, for example, ions, neutral atoms such as Ar (argon), Kr (krypton), or Ne (neon), or cluster ions. It is preferable that the energy particles consist of Ar.

Here, when energy particles are irradiated onto the main surface 12b of border 12, an amorphous layer 142 (an example of a first amorphous layer) is formed on the main surface 12b of border 12. When energy particles are irradiated onto the main surface 13a of sub-border 13, an amorphous layer 143 (an example of a second amorphous layer) is formed on the main surface 13a of sub-border 13. Each of the amorphous layers 142 and 143 has a thickness, for example, greater than 0 and less than or equal to 5 nm.

The amorphous layer 142 is formed when the material constituting the border 12 on the main surface 12b becomes amorphous due to collisions with energy particles. The amorphous layer 142 is continuous with the border 12. The appearance of the amorphous layer 142 causes the main surface 12b of the border 12 to recede slightly toward the main surface 12a.

The amorphous layer 143 is formed when the material constituting the sub-border 13 on the main surface 13a becomes amorphous due to collisions with energy particles. The amorphous layer 143 is continuous with the sub-border 13. The appearance of the amorphous layer 143 causes the main surface 13a of the sub-border 13 to recede slightly toward the main surface 13b.

After irradiating with energy particles, amorphous layer 142 and amorphous layer 143 are brought into contact with each other, as indicated by arrow AR2. This joins the main surface 12b of border 12 and the main surface 13a of sub-border 13, revealing the joint layer 14. When using the surface activation bonding method, the joint layer 14 includes amorphous layer 142, which is an amorphous layer of the material constituting border 12, and amorphous layer 143, which is an amorphous layer of the material constituting sub-border 13. Amorphous layer 142 contains Si and is formed on the main surface 12b of border 12. Amorphous layer 143 is formed between amorphous layer 142 and the main surface 13a of sub-border 13. Amorphous layers 142 and 143 can be observed using TEM (Transmission Electron Microscopy) or similar methods.

Referring to Figure 7, the border 12 and the sub-border 13 may be joined using a hydrophilic bonding method in the following way. The hydrophilic bonding method is also called Fusion Bonding or Silicon Direct Bonding (SDB). A SiO2 layer ₁₄₄ (first silicon oxide layer) is formed on the main surface 12b of the border 12 (the surface facing the sub-border 13). A SiO2 layer 145 (second silicon oxide layer) is formed on the main surface _13a of the sub-border 13 (the surface facing the border 12). Each of the _SiO2 layers 144 and 145 may be formed by a method such as CVD, by forming a Si layer on the underlying surface (main surface 12b or 13a) and thermally oxidizing the Si layer, or by thermally oxidizing the underlying surface. Furthermore, if the border 12 is made of Si and the pellicle film 11 is made of SiC, then by thermal oxidation of these materials, a thermal oxide film can be selectively formed only on the exposed surface of the border 12, including the main surface 12b.

After forming the _SiO2 layers 144 and 145, each of the _SiO2 layers 144 and 145 is subjected to a hydrophilic treatment. After the hydrophilic treatment, the _SiO2 layer 144 and the _SiO2 layer 145 are brought into contact with each other, as indicated by arrow AR2. This joins the main surface 12b of the border 12 and the main surface 13a of the sub-border 13, and a bonded layer 14 appears. When the hydrophilic bonding method is used, after bonding, a bonded layer 14 is obtained in which the _SiO2 layer 144 and the _SiO2 layer 145 are integrated. The bonded layer 14 contains an _SiO2 layer with a thickness of 1 nm to 100 μm. Preferably, the bonded layer 14 contains an _SiO2 layer with a thickness of 1 nm to 15 μm.

Furthermore, as a hydrophilic bonding method similar to the method described above, a method may be used in which the _SiO2 layers 144 and 145 are brought into contact with each other in hydrogen peroxide water without applying a hydrophilic treatment to each of _{the SiO2 layers} 144 and 145. Alternatively, a method may be used in which the main surface 12b of the border 12 is directly hydrophilized without forming each of the SiO2 layers 144 and 145.

Referring to Figure 8, after joining the border 12 and the sub-border 13, the protective film 92 is removed from the main surface 11a of the pellicle film 11, and the support substrate 93 is removed from the main surface 13b of the sub-border 13. This yields the pellicle material 2.

Furthermore, when the border 12 and sub-border 13 are joined using a surface activation bonding method, the protective film 146 may be removed after the support substrate 93 is removed. If the protective film 146 is made of resist, it is removed using a registry remover or the like. If the protective film 146 is made of very thin Si, it is removed by immersion in hydrofluoric acid for a very short time (dip etching), etc.

Furthermore, when the border 12 and the sub-border 13 are joined using a hydrophilic bonding method, a _SiO2 layer 144 may remain on the main surface 11b of the pellicle film 11 after the support substrate 93 is removed. For this reason, the remaining SiO2 layer ₁₄₄ on the pellicle film 11 may be removed by immersing the pellicle film 11 in hydrofluoric acid or the like.

Referring to Figure 9, when manufacturing the pellicle 1 using the pellicle material 2, the sub-border 13 of the pellicle material 2 and the frame 15 are joined together, thereby connecting the holes 131 in the sub-border 13 to the holes 151 in the frame 15. The method of joining the border 12 and the sub-border 13 is arbitrary; for example, they can be joined by adhesive. When the sub-border 13 and the frame 15 are joined by adhesive, a joining layer 16, consisting of an adhesive layer, is formed between the main surface 13b of the sub-border 13 and the main surface 15a of the frame 15.

In cases where the sub-border 13 and the frame 15 are joined by adhesive, the main surface 15a of the frame 15 may be provided with recesses for applying adhesive. The lower surface of the frame 15 may be provided with a material made of polybutene resin, polyvinyl acetate resin, acrylic resin, or silicone resin for attachment to the photomask.

Referring to Figures 9 and 10, when joining the frame 15 to the pellicle material 2, an automated mounting device is used, for example. The automated mounting device includes a computer (image recognition device). The computer recognizes the shape of the inner surface 13c of the holes 131 in the subborder 13 based on an image of the holes 131 in the subborder 13. The computer also recognizes the shape of the inner surface 15c of the holes 151 in the frame 15 based on an image of the holes 151 in the frame 15. Next, the automated mounting device adjusts the position of the frame 15 relative to the subborder 13 so that the inner surface 13c of the holes 131 in the subborder 13 and the inner surface 15c of the holes 151 in the frame 15 overlap each other. The adjustment of the frame 15's position is indicated by arrow AR4. After adjusting the position of the frame 15, the automated mounting device joins the frame 15 to the subborder 13 as indicated by arrow AR5.

The main surface 15b of the frame 15 may be provided with engaging parts for alignment with the photomask PM, and recesses for applying adhesive. When attaching the frame 15 to the photomask PM, an adhesive made of polybutene resin, polyvinyl acetate resin, acrylic resin, or silicone resin may be used.

[Effects of the Embodiment]

Referring to Figure 2(a), the inner circumferential surface 12c of the hole 121 in the border 12 has a complex shape because it is eroded during wet etching. Specifically, the width d1 of the hole 121 (Figure 1) increases from the main surface 12a to the main surface 12b of the border 12, and the inner circumferential surface 12c of the hole 121 has a "shoreline shape". Therefore, when viewing the border 12 from the main surface 12b side, a double contour line appears: a narrow contour line L1 of the inner circumferential surface 12c of the hole 121 at a depth position near the main surface 12a, and a wider contour line L2 of the inner circumferential surface 12c of the hole 121 at a depth position near the main surface 12b. In addition, due to the effect of wet etching when forming the hole 121, the arithmetic mean roughness Ra of the inner circumferential surface 12c of the hole 121 in the border 12 is large, and the irregularities of the inner circumferential surface 12c of the hole 121 in the border 12 are large. Therefore, the linearity of the straight sections 126, 127, 128, and 129 when viewed from the main surface 12b is low, and the shape of the corners of the inner circumferential surface 12c of the hole 121 is rough.

As described above, the inner circumferential surface 12c of the hole 121 in the border 12 has a complex shape. Therefore, when adjusting the position of the frame relative to the border, as in conventional methods, so that the center of gravity of the inner circumferential surface of the hole in the border and the center of gravity of the inner circumferential surface of the hole in the frame overlap, the position of the frame relative to the border tended to deviate from the intended position. Furthermore, when viewed in plan view, it was difficult to adjust the position of the frame relative to the border so that the inner circumferential surface of the hole in the border and the inner circumferential surface of the hole in the frame overlapped.

Furthermore, when directly joining the frame to the border as in conventional methods, if the main surface of the frame is pressed against the border, and the pressure is applied to the position directly above the inner circumferential surface of the border's hole on the frame's main surface, the pressing force is not sufficiently transmitted to the border.

As a result, conventionally, it has been difficult to join the frame to the pellicle material.

Referring to Figure 2(b), according to the above-described embodiment, the frame 15 is joined to the sub-border 13, which is a separate member from the border 12. The inner circumferential surface 13c of the hole 131 in the sub-border 13 is not affected by wet etching when forming the hole 121 in the border 12. Therefore, the inner circumferential surface 13c of the hole 131 in the sub-border 13 can be freely designed to have a simple shape. Specifically, the arithmetic mean roughness Ra of the inner circumferential surface 13c of the hole 131 in the sub-border 13 can be reduced. Therefore, the linearity of each of the straight portions 136, 137, 138, and 139 of the inner circumferential surface 13c when the sub-border 13 is viewed from the main surface 13b side can be increased. Furthermore, the radius of curvature at each of the intersections of straight section 136 and straight section 138, straight section 136 and straight section 139, straight section 137 and straight section 138, and straight section 137 and straight section 139 can be less than 0.5 mm. Also, the width d2 of the hole 131 (Figure 1) may be constant from the main surface 13a to the main surface 13b of the sub-border 13.

As described above, the inner circumferential surface 13c of the hole 131 in the sub-border 13 can be freely designed to have a simple shape. Therefore, the position of the frame 15 relative to the sub-border 13 can be easily adjusted so that the center of gravity of the inner circumferential surface 13c of the hole 131 in the sub-border 13 and the center of gravity of the inner circumferential surface 15c of the hole 151 in the frame 15 overlap with each other. In addition, when viewed in plan view, the position of the frame 15 relative to the sub-border 13 can be easily adjusted so that the inner circumferential surface 13c of the hole 131 in the sub-border 13 and the inner circumferential surface 15c of the hole 151 in the frame 15 overlap with each other.

Furthermore, when joining the frame 15 to the sub-border 13 and pressing the main surface 15b of the frame 15, sufficient pressure can be transmitted to the sub-border 13.

As a result, according to the above-described embodiment, the frame 15 can be easily joined to the pellicle material 2.

[Different Version]

Figure 11 is an enlarged cross-sectional view showing the configuration of the pellicle 1 in the first and second modifications of one embodiment of the present invention. Figure 11(a) is the first modification, and Figure 11(b) is the second modification. Figure 12 is an enlarged cross-sectional view showing the configuration of the pellicle 1 in the third and fourth modifications of one embodiment of the present invention. Figure 12(a) is the third modification, and Figure 12(b) is the fourth modification. Note that Figures 11 and 12 are enlarged cross-sectional views of the area near the border 12 (part A in Figure 1(a)). Line L3 in Figure 11 is the contour line of the outer circumferential surface 13d of the sub-border 13 when the pellicle material 2 is viewed from the main surface 13b side. Line L4 in Figure 12 is the contour line of the inner circumferential surface 13c of the sub-border 13 when the pellicle material 2 is viewed from the main surface 13b side.

Referring to Figure 11(a), in the first modified example, the outer circumferential surface 12d of the border 12 extends perpendicularly to the main surfaces 12b and 13b, respectively. The outer circumferential surface 13d of the sub-border 13 protrudes outward (to the left in Figure 11) than the outer circumferential surface 12d of the border 12. The outer circumferential surface 13d of the sub-border 13 extends perpendicularly to the main surfaces 12b and 13b, respectively.

Referring to Figure 11(b), in the second modification, the outer circumferential surface 12d of the border 12 protrudes outward from the main surface 12b toward the main surface 12a. When viewing the pellicle material 2 from the main surface 13b side, the end of the outer circumferential surface 12d on the main surface 12a side may be located outside line L3 or inside line L3 (right side in Figure 11). The outer circumferential surface 13d of the sub-border 13 protrudes outward more than the outer circumferential surface 12d of the border 12. The outer circumferential surface 13d of the sub-border 13 extends perpendicularly to the main surfaces 12b and 13b, respectively.

Referring to Figure 12(a), in the third modification, the outer circumferential surface 12d of the border 12 extends perpendicularly to the main surfaces 12b and 13b, respectively. The outer circumferential surface 13d of the sub-border 13 protrudes outward from the main surface 13a toward the main surface 13b. The inner circumferential surface 13c of the sub-border 13 protrudes inward from the main surface 13a toward the main surface 13b. In this case, line L4 is formed by the end of the inner circumferential surface 13c on the main surface 13b side. When viewing the pellicle material 2 from the main surface 13b side, it is preferable that the end of the inner circumferential surface 12c of the border 12 toward the main surface 12a is located outside line L4 (left side in Figure 12), but it may also be located inside line L4 (right side in Figure 12).

Referring to Figure 12(b), in the fourth modification, the outer circumferential surface 12d of the border 12 extends perpendicularly to the main surfaces 12b and 13b, respectively. The outer circumferential surface 13d of the sub-border 13 protrudes outward from the main surface 13b toward the main surface 13a. The inner circumferential surface 13c of the sub-border 13 protrudes inward from the main surface 13b toward the main surface 13a. In this case, line L4 is formed by the end of the inner circumferential surface 13c on the main surface 13a side. When viewing the pellicle material 2 from the main surface 13b side, it is preferable that the end of the inner circumferential surface 12c of the border 12 toward the main surface 12a is located outside line L4 (left side in Figure 12), but it may also be located inside line L4 (right side in Figure 12).

In each of the first to fourth modified examples, the shapes of the outer circumferential surface 12d of the border 12, the inner circumferential surface 12c of the sub-border 13, and the outer circumferential surface 12d of the sub-border 13 can be combined with each other.

Furthermore, the configurations in the modified examples shown in Figures 11 and 12, other than those described above, are the same as those in the embodiments described above, and therefore will not be repeated in their explanation.

[others]

The embodiments and their respective modifications described above can be combined as appropriate.

The embodiments and modifications described above should be considered in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended to be included.

1. Pellicle (an example of a pellicle)
2. Materials for the pellicle (Examples of materials for the pellicle)
3. Intermediate 11. Pellicle membrane (an example of a pellicle membrane)
11a, 11b Main surfaces of the pellicle membrane (an example of one main surface and the other main surface of the pellicle membrane)
12. Border (an example of the first support structure)
12a, 12b Main surface of the border 12c Inner surface of the hole in the border 12d Outer surface of the border 13 Sub-border (an example of a second support)
13a, 13b Main surface of the subborder 13c Inner surface of the hole in the subborder 13d Outer surface of the subborder 14 Bonding layer (an example of a bonding layer)
15 Frame (Example of a frame) 15a, 15b Main surface of the frame 15c Inner surface of a hole in the frame 16 Joining layer 17 Recess (Example of a recess)
91 Mask layer 92, 146 Protective film 93 Support substrate 121, 122 Border holes (example of the first hole)
126, 127, 128, 129 Straight sections of the contour lines of the inner circumferential surface of the hole in the border (examples of the first, second, third, and fourth straight sections)
131 Holes in the sub-border (an example of a second hole)
136, 137, 138, 139 Straight sections of the contour lines of the inner surface of the hole in the sub-border (examples of the 5th, 6th, 7th, and 8th straight sections)
141. Glass frit (an example of glass frit)
142, 143 Amorphous layers (Amorphous layers, and examples of the first and second amorphous layers)
144, 145 SiO ₂ layers (a silicon oxide layer, and an example of the first and second silicon oxide layers)
151 Frame holes L1, L2, L3, L4 Contour lines PM Photomask (Example of a photomask)
RG1: Center of the main surface of the border RG2: Bottom surface of the hole in the border RG3: Inner circumferential surface of the hole in the border d1: Width of the hole in the border d2: Width of the hole in the sub-border

Claims (5)

A pellicle comprising a pellicle material joined to a photomask via a frame, and the frame ,
The aforementioned pellicle material is,
A pellicle film including one main surface and the other main surface,
A first support comprising a silicon-containing material and including a first pore, the first support supporting the pellicle film from the other main surface side of the pellicle film,
A second support having a second hole connected to the first hole,
It includes a bonding layer that joins the first support and the second support,
The second support is a member for joining to the photomask via the frame,
The other main surface of the pellicle membrane is exposed at the bottom of the first hole.
When viewed in cross-section of the pellicle membrane cut by a plane perpendicular to one of the main surfaces, the width of the first pore increases from the pellicle membrane side of the first support toward the second support side of the first support .
A pellicle further comprising another bonding layer for joining the second support and the frame. The pellicle according to claim 1, wherein the bonding layer includes an amorphous layer containing silicon. The pellicle according to claim 1, wherein the pellicle film comprises at least one material selected from the group consisting of silicon, carbon, boron, and nitrogen. The pellicle according to claim 1, wherein the total thickness of the first support, the bonding layer, and the second support is greater than 0 and less than or equal to 1 mm. When the first support is viewed from the side facing the second support, the contour line of the inner circumferential surface of the first hole in the first support includes each of the first, second, third, and fourth linear portions that extend in a straight line,
The first straight section and the second straight section are parallel to each other, and the third straight section and the fourth straight section are parallel to each other.
When the second support is viewed from the side opposite to the side facing the first support, the contour line of the inner circumferential surface of the second hole in the second support includes each of the fifth, sixth, seventh, and eighth linear portions that extend in a straight line.
The fifth straight section and the sixth straight section are parallel to each other, and the seventh straight section and the eighth straight section are parallel to each other.
The pellicle according to claim 1, wherein the arithmetic mean roughness Ra of the inner surface of the first hole in the first support is greater than the arithmetic mean roughness Ra of the inner surface of the second hole in the second support .