Structural member

Abstract

To provide a structural member with high durability against plasma.SOLUTION: A structural member 10 includes a base material 100 that is a ceramic, a base layer 200 that covers a surface S1 of the base material 100, and a protective film 300 that covers a surface S2 of the base layer 200. On the base layer 200, the orientation of each crystallite 210 on the surface S2 on the protective film 300 is irregular and not aligned.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a structural member. [Background technology]

[0002] Structural members having a protective film on the surface of a substrate are used in various fields such as semiconductor manufacturing equipment. For example, as described in Patent Document 1 below, in a semiconductor manufacturing equipment, a protective film is formed on the surface of a substrate constituting an inner wall of a chamber to protect the substrate from plasma. As the substrate, for example, ceramics such as alumina are used. As the protective film, for example, yttria, yttrium fluoride, etc. are used. As a method for forming a protective film on the surface of the substrate, various film formation methods such as aerosol deposition method and physical vapor deposition method (PVD) can be adopted. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-321183 A Summary of the Invention [Problem to be solved by the invention]

[0004] A number of crystallites are exposed on the surface of the substrate made of a ceramic material, and the protective film is formed to cover these. The size and orientation of the crystallites on the surface of the substrate change depending on the firing conditions of the substrate, etc.

[0005] The present inventors have found that the orientation of the crystallites on the surface of the substrate has a large effect on the durability of the protective film covering it. Specifically, it has been found that when the crystallites are oriented in a specific direction, the durability of the protective film formed directly thereon is significantly reduced. For the sake of convenience, the "specific direction" in the above, that is, the orientation of the crystallites that reduces the durability of the protective film formed directly thereon, is also referred to as "specific direction" below.

[0006] In order to improve the durability of the entire protective film, it is preferable to make the orientation of all crystallites on the surface of the substrate different from the specific direction. However, it is difficult to adjust the orientation of the crystallites over the entire surface of the substrate, which is a large member.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a structural member having high durability against plasma. [Means for solving the problem]

[0008] In order to solve the above problems, the structural member according to the present invention includes a ceramic substrate, an underlayer covering the surface of the substrate, and a protective film covering the surface of the underlayer. The underlayer has crystallites on the surface facing the protective film that are not aligned in the same direction and are therefore irregular.

[0009] In such a structural member, the protective film does not directly cover the surface of the substrate, but is formed to cover the surface of the undercoat layer formed between the substrate and the protective film. On the surface of the undercoat layer, the orientation of each crystallite is not uniform and is irregular. Therefore, even if many crystallites on the substrate surface are oriented in a specific direction, the durability of the protective film is not reduced by the influence of the orientation.

[0010] Although crystallites oriented in a "specific direction" may exist in a part of the underlayer, they exist only locally, so that a protective film with low durability against plasma is not formed over a wide area. For example, by reducing the crystallite size of the underlayer, it is possible to suppress the effect of crystallites oriented in a specific direction to a negligible level. Effect of the Invention

[0011] According to the present invention, a structural member having high durability against plasma can be provided. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic cross-sectional view of a structural member according to the present embodiment. [Diagram 2] FIG. 2 is a diagram showing a schematic diagram of the arrangement of crystallites on the surface of an underlayer. [Diagram 3] FIG. 2 is a diagram showing a schematic diagram of the arrangement of crystallites on the surface of a substrate. [Figure 4] 11A and 11B are diagrams for explaining the effect of providing a base layer. [Diagram 5] 4A to 4C are diagrams for explaining a method for manufacturing a structural member according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.

[0014] The structural member 10 according to this embodiment is used as a member constituting the inner wall of a processing chamber in a semiconductor manufacturing apparatus (not shown) such as a plasma etching apparatus. Note that the use of such a structural member 10 is merely an example, and is not limited to use in semiconductor manufacturing apparatus.

[0015] 1, the structural member 10 includes a substrate 100, an underlayer 200, and a protective film 300. In a plasma etching device or the like, a surface S3 of the protective film 300 is exposed toward the space inside a chamber. The protective film 300 is provided for the purpose of protecting a surface S1 of the substrate 100 from plasma.

[0016] The substrate 100 is a member that occupies almost the entirety of the structural member 10. In this embodiment, the substrate 100 is made of high-purity aluminum oxide (Al 2 O 3) is a ceramic sintered body containing the above-mentioned sintered body, but it may be a ceramic of a different type. In addition, the surface S1 of the substrate 100 is a flat surface in this embodiment, but the surface S1 may have irregularities or a slope.

[0017] The underlayer 200 is a layer formed so as to cover the surface S1 of the base material 100. The protective film 300 described below is formed so as to cover the surface S2 of the underlayer 200, rather than directly covering the surface S1 of the base material 100. The underlayer 200 is made of polycrystalline yttria (Y 2 O 3 ) and is formed by an aerosol deposition method. The reason for interposing the underlayer 200 between the substrate 100 and the protective film 300 will be explained later.

[0018] As described above, the protective film 300 is a film formed to protect the substrate 100 from plasma. The protective film 300 is formed so as to cover the entire surface S2 of the underlayer 200. The protective film 300 is made of polycrystalline yttria (Y 2 O 3 ) and is formed by physical vapor deposition (PVD). The thickness of the protective film 300 is appropriately set depending on the period during which durability against plasma is required to be maintained. In this embodiment, the thickness of the protective film 300 is 10 μm. The protective film 300 and the underlayer 200 may be formed of the same material as in this embodiment, but may also be formed of different materials.

[0019] 2 is a schematic diagram of the surface S2 of the underlayer 200 as viewed from a direction perpendicular thereto. A plurality of crystallites 210 constituting the underlayer 200 are arranged on the surface S2. The protective film 300 is formed so as to cover the surface S2 of FIG. 2 from the front side of the page. In FIG. 2, the arrows drawn on each crystallite 210 indicate the orientation direction of the crystallite 210. The "orientation direction" refers to a direction that is individually defined for each crystallite 210, for example, as a direction in which the Miller indices (directional indices) have specific values.

[0020] As is well known, in the aerosol deposition method, microparticles, which are the material of the layer 200, are dispersed in a gas to form an "aerosol," which is then sprayed toward the surface S1 of the substrate 100 to collide with it. On the surface S1, the microparticles are deformed and crushed by the impact of the collision, and the microparticles bond together and gradually accumulate as the underlayer 200. As a result of being formed in this manner, the orientation of each crystallite 210 on the surface S2 of the underlayer 200 is irregular and not aligned in a specific direction.

[0021] FIG. 3 is a schematic diagram of the surface S1 of the substrate 100 viewed from a direction perpendicular thereto. A plurality of crystallites 110 constituting the substrate 100 are arranged on the surface S1. The underlayer 200 is formed so as to cover the surface S1 of FIG. 3 from the front side of the paper. In FIG. 3 as well as in FIG. 2, an arrow is drawn on each crystallite 110 to indicate the orientation direction of the crystallite 110. The definition of "orientation direction" is the same as that of the crystallite 210. In this embodiment, the orientation direction of the crystallites 110 on the surface S1 is also irregular, not aligned in a specific direction. Instead of such an embodiment, the orientation direction of the crystallites 110 may be aligned in one direction.

[0022] 2 and 3, the average crystallite size of the underlayer 200 (FIG. 2) is smaller than the average crystallite size of the substrate 100 (FIG. 3). The "average crystallite size" refers to the average value of the diameters of multiple crystallites that appear in a cross section when each member (underlayer 200 or substrate 100) is cut.

[0023] The crystallite size can be calculated, for example, by taking a transmission electron microscope (TEM) image at a magnification of 400,000 times or more and calculating the average diameter of 15 crystallites in this image by circular approximation. In this case, if the sample thickness during focused ion beam (FIB) processing is sufficiently thinned to about 30 nm, the crystallites can be more clearly identified. The magnification for photography can be appropriately selected within the range of 400,000 times or more.

[0024] The reason for interposing the underlayer 200 between the substrate 100 and the protective film 300 will be described. Fig. 4(A) shows an example of a case where the protective film 300 is formed directly on the surface S1 of the substrate 100 without interposing the underlayer 200, as a comparative example of this embodiment. In this figure, the cross section of the crystallite 110 is drawn only in the vicinity of the surface S1 of the substrate 100, and the crystallite 110 is omitted in the part inside (the lower side in the figure).

[0025] The protective film 300 is formed so as to cover each of the crystallites 110 exposed on the surface S1. The entire portion of the protective film 300 that covers one (i.e., a common) crystallite 110 from directly above is defined below as a "small region 310." The protective film 300 is divided into a plurality of small regions 310, one for each of the crystallites 110 on the surface S1. In FIG. 4(A), the boundaries between adjacent small regions 310 are indicated by dotted lines.

[0026] The protective film 300 formed by physical vapor deposition grows while being influenced by the orientation of the crystallites 110 directly below it, i.e., the crystallites 110 that are the starting points of film formation. Therefore, the properties of the protective film 300 are not uniform throughout the entire protective film 300, but differ for each small region 310.

[0027] The present inventors have conducted extensive research into the relationship between the orientation of the crystallites 110 and the durability of the protective film 300 formed directly thereon. As a result, they have found that the orientation of the crystallites 110 on the substrate surface has a significant effect on the durability of the protective film 300 against plasma. Specifically, they have found that when the crystallites 110 are oriented in a specific direction, the durability of the protective film formed directly thereon is significantly reduced. For convenience of explanation, the "specific direction" in the above, that is, the orientation of the crystallites 110 that reduces the durability of the protective film formed directly thereon, is also referred to as the "specific direction" below. The orientation of the crystallites 210 is defined in the same way.

[0028] In Fig. 4(A), a crystallite 110 whose orientation is in a specific direction is marked with an "x". Such a crystallite 110 will be referred to as "crystallite 111" below. Also, a small region 310 directly above the crystallite 111 will be referred to as "small region 311" below.

[0029] The small regions 311 are portions in which the durability against plasma is significantly reduced due to the influence of the orientation direction of the crystallites 111. The shape of the small regions 311 in top view is generally the same as the shape of the crystallites 111 directly below it. For this reason, when the crystallites 111 are large, the range of the small regions 311 with low durability also becomes large, and the durability of the entire protective film 300 becomes low.

[0030] Also, the crystallites 110 may be oriented in a specific direction. In this case, almost all of the crystallites 110 become crystallites 111, and the protective film 300 thereon becomes small regions 311. Therefore, regardless of the size of the crystallites 110, the durability of the entire protective film 300 becomes low.

[0031] In order to improve the durability of the protective film 300, it is preferable to make the orientation direction of all the crystallites 110 different from a specific direction. However, it is often difficult to adjust the orientation direction of the crystallites 110 over the entire surface of the substrate 100, which is a large member.

[0032] Therefore, in this embodiment, an underlayer 200 is interposed between the substrate 100 and the protective film 300, and the durability of the protective film 300 is improved by adjusting the orientation direction of the crystallites 210 in the underlayer 200, etc.

[0033] In Fig. 4(B), the configuration of the structural member 10 according to this embodiment is illustrated in a schematic manner similar to that of Fig. 4(A). In the example of Fig. 4(B), the surface S1 of the substrate 100, which is the same as that of the example of Fig. 4(A), is covered with an underlayer 200. In Fig. 4(B), a cross section of the crystallites 210 is illustrated only in the vicinity of the surface S2 of the underlayer 200, and the crystallites 210 are not illustrated in the part inside (the lower side in the figure).

[0034] In FIG. 4(B), crystallites 210 whose orientation is in a specific direction are marked with an "x". Such crystallites 210 are hereinafter also referred to as "crystallites 211". The protective film 300 in FIG. 4(B) is divided into a plurality of small regions 310 for each crystallite 210 on the surface S2. The small region 310 directly above the crystallite 211 is the "small region 311" with low durability. For convenience of illustration, only the small region 311 out of the plurality of small regions 310 is shown in FIG. 4(B).

[0035] As described above, on the surface S2 of the underlayer 200, the orientation of each crystallite 210 is not uniform but irregular. Therefore, even if many crystallites 110 are oriented in a specific direction on the surface S1 of the substrate 100, the durability of the protective film 300 is not reduced due to the influence. Although crystallites 211 oriented in a "specific direction" may exist in a part of the underlayer 200, they exist only locally, so that a small region 311 with low durability against plasma is not widely formed directly above them.

[0036] Furthermore, in this embodiment, the average crystallite size of the underlayer 200 is smaller than the average crystallite size of the substrate 100. The crystallites 211 facing a specific direction are small, and the small regions 311 directly above them are also small, so that the effect on the durability of the entire protective film 300 is kept negligibly small.

[0037] The underlayer 200 is provided to adjust the distribution and size of the small regions 311 in the protective film 300, and therefore only needs to have a minimum thickness that can withstand the formation of the protective film 300. For this reason, the underlayer 200 is thinner than the protective film 300, and in this embodiment, the thickness is 5 μm or less. By keeping the thickness of the underlayer 200 to the minimum thickness, the time and cost required for forming the underlayer 200 can be suppressed.

[0038] A method for manufacturing the structural member 10 will be described with reference to Fig. 5. First, as shown in Fig. 5(A), a substrate 100 is prepared. It is preferable that the surface roughness, etc. of the surface S1 of the substrate 100 is adjusted in advance to such an extent that the underlayer 200 can be formed thereon stably later.

[0039] 5(B), the underlayer 200 is formed so as to cover the surface S1 of the substrate 100. As described above, in this embodiment, the underlayer 200 is formed by using the aerosol deposition method. As a result, the crystallites 210 of the underlayer 200 are formed so as to have irregular orientations that are not aligned.

[0040] As long as the orientation direction of the crystallites 210 can be made irregular, the underlayer 200 may be formed by other methods. For example, the underlayer 200 may be formed by PVD or CVD. Alternatively, a method may be employed in which a plate-shaped calcined body is arranged so as to cover the surface S1 of the base material 100, and then the entire body is heated to sinter the calcined body, thereby forming the underlayer 200.

[0041] It is preferable that the surface roughness, etc. of the surface S2 of the underlayer 200 is adjusted in advance so that the protective film 300 can be formed thereon in a stable manner.

[0042] 5(C), the protective film 300 is formed so as to cover the surface S2 of the underlayer 200. As described above, in this embodiment, the protective film 300 is formed by using physical vapor deposition (PVD). Each part of the protective film 300 grows while being influenced by the surface S2 of the underlayer 200 located immediately below it. As described above, the protective film 300 may have small regions 311 with low durability against plasma, but the areas of these regions are small and they are distributed, so that the durability of the protective film 300 is sufficiently ensured.

[0043] The protective film 300 may be formed by a method other than the physical vapor deposition method. For example, the protective film 300 may be formed by a method such as CVD or ALD. However, when the protective film 300 is formed by the physical vapor deposition method as in the present embodiment, it is preferable because a dense protective film 300 can be formed at a relatively low cost.

[0044] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Any design modifications made by a person skilled in the art to these specific examples are also included within the scope of the present disclosure as long as they have the features of the present disclosure. The elements of each of the above-mentioned specific examples and their arrangements, conditions, shapes, etc. are not limited to those exemplified and can be changed as appropriate. The combination of each of the elements of each of the above-mentioned specific examples can be changed as appropriate as long as no technical contradiction occurs. [Explanation of symbols]

[0045] 10: Structural members 100: Base material 200: Base layer 210: Crystal 300: Protective film S1,S2,S3:Surface

Claims

1. A substrate that is a ceramic; A base layer covering a surface of the substrate; a protective film covering a surface of the underlayer, The undercoat layer is A structural member, characterized in that the orientation of each crystallite on the surface on the protective film side is not uniform but irregular.

2. The structural member according to claim 1 , wherein the average crystallite size of the underlayer is smaller than the average crystallite size of the substrate.

3. 2. The structure according to claim 1, wherein said undercoat layer is thinner than said protective film.

4. 2. The structural member according to claim 1, wherein the undercoat layer is formed by an aerosol deposition method.

5. 2. The structural member according to claim 1, wherein the protective film is formed by a physical vapor deposition method.

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