Structural member

Abstract

Provided is a structural member which has high durability with regard to plasma. A structural member10 comprises a base material 100 and a protective film 200 which covers a surface S1 of the base material 100. The protective film 200 is formed of a polycrystalline material which contains an alkaline earth metal oxide or an alkaline earth metal halide. In the structural member10, the respective orientations of crystallites 210 present on a surface S2 of the protective film 200 are not aligned and are irregular.

Description

structural members

[0001] The present invention relates to structural members.

[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 semiconductor manufacturing equipment, a protective film is formed on the surface of a substrate that constitutes the inner wall of a chamber to protect the substrate from plasma. For example, ceramics or the like is used as the substrate. For example, yttria or the like is used as the protective film. As a method for forming a protective film on the surface of a substrate, various film formation methods can be used, such as thermal spraying, physical vapor deposition (PVD), and chemical vapor deposition (CVD).

[0003] Japanese Patent Application Laid-Open No. 2007-321183

[0004] The present inventors have been investigating the use of polycrystalline materials containing alkaline earth metal oxides or alkaline earth metal halides as the material for the protective film. Experiments conducted by the present inventors have shown that when a protective film is formed using such materials, the durability of the protective film against plasma varies significantly depending on the orientation of the crystallites on its surface. Therefore, if the orientation of each crystallite on the surface of the protective film is aligned in a specific direction, the durability of the protective film against plasma may be significantly reduced.

[0005] 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 that is highly durable against plasma.

[0006] In order to solve the above problems, the present invention provides a structural member comprising a substrate and a protective film covering the surface of the substrate. The protective film is a film formed of a polycrystalline material containing an alkaline earth metal oxide or an alkaline earth metal halide. In this structural member, the orientation of each crystallite on the surface of the protective film is irregular, not aligned.

[0007] Even in such a structural member, the multiple crystallites on the surface of the protective film may be oriented in a direction that reduces the durability of the protective film. However, since the orientation of each crystallite is irregular, even if some crystallites as described above (i.e., oriented in an undesirable direction) exist, the durability of the protective film is averaged over the entire protective film, so sufficient durability against plasma can be ensured. A protective film with irregular crystallite orientation can be formed, for example, by using an aerosol deposition method.

[0008] According to the present invention, a structural member having high durability against plasma can be provided.

[0009] 1 is a diagram schematically illustrating a cross section of a structural member according to an embodiment of the present invention; 2 is a diagram schematically illustrating crystallites on the surface of a protective film;

[0010] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions will be omitted.

[0011] The structural member 10 according to this embodiment is used as a member that constitutes 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 semiconductor manufacturing apparatuses.

[0012] 1, the structural member 10 includes a substrate 100 and a protective film 200. In a plasma etching apparatus or the like, a surface S2 of the protective film 200 is exposed to the space within the chamber. The protective film 200 is provided to protect the surface S1 of the substrate 100 from plasma.

[0013] The substrate 100 is a member that occupies almost the entire structural member 10. In this embodiment, the substrate 100 is made of high-purity aluminum oxide (Al ２ O ３), but may be made of a different type of ceramic. The substrate 100 may also be made of a material other than ceramic, such as a metal. In this embodiment, the surface S1 of the substrate 100 is flat, but the surface S1 may have irregularities or a slope.

[0014] As described above, the protective film 200 is a film formed to protect the substrate 100 from plasma. The protective film 200 is formed so as to cover the entire surface S1 of the substrate 100. In this embodiment, the protective film 200 is formed using an aerosol deposition method.

[0015] In this embodiment, the material of the protective film 200 is magnesium fluoride (MgF ２ ) as a main component is used. As the material for the protective film 200, any polycrystalline material containing an oxide of an alkaline earth metal or a halide of an alkaline earth metal other than magnesium fluoride can be used. As the "alkaline earth metal", in addition to magnesium (Mg) as in this embodiment, for example, calcium (Ca) can be used. As the "halide", in addition to fluoride as in this embodiment, for example, chloride can be used.

[0016] Specifically, the material of the protective film 200 is MgF ２ , MgCl ２ , CaF ２ , CaCl ２ , MgO, CaO, etc. can be used.

[0017] In this embodiment, the thickness of the protective film 200 is 10 μm. The thickness of the protective film 200 may be set appropriately depending on the length of time for which durability against plasma is required to be maintained.

[0018] 2 is a schematic diagram of the surface S2 of the protective film 200 as viewed from a direction perpendicular thereto. A plurality of crystallites 210 constituting the protective film 200 are arranged on the surface S2. In FIG. 2, the arrow drawn above each crystallite 210 indicates the orientation direction of the crystallite 210. The "orientation direction" refers to a direction individually defined for each crystallite 210, for example, as a direction in which the Miller indices (directional indices) have specific values.

[0019] As is well known, in the aerosol deposition method, microparticles, which are the material for the protective film 200, are dispersed in a gas to form an "aerosol," which is then sprayed toward the surface S1 of the substrate 100 and allowed to collide. At the surface S1, the impact of the collision causes deformation and fragmentation of the microparticles, causing the microparticles to bond together and gradually deposit as the protective film 200. As a result of being formed in this manner, the orientation of each crystallite 210 on the surface S2 of the protective film 200 is irregular and not aligned in any particular direction.

[0020] Note that the protective film 200 may be formed using a method other than the aerosol deposition method, as long as the orientation direction of each crystallite 210 on the surface S2 can be made irregular. For example, the protective film 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 substrate 100, and then the entire body is heated to sinter the calcined body, thereby forming the protective film 200.

[0021] The reason for making the orientation direction of the crystallites 210 irregular will be explained. The inventors have conducted extensive research into the relationship between the orientation direction of each crystallite 210 on the surface S2 of the protective film 200 and the durability of the protective film 200 against plasma. Note that "durability" here refers to the smallness of the etching rate of the protective film 200 when the protective film 200 is exposed to plasma.

[0022] As a result of the above research, it has been found that when a protective film is formed using a polycrystalline material containing an alkaline earth metal oxide or an alkaline earth metal halide, as in this embodiment, the durability of the protective film against plasma varies greatly depending on the orientation of the crystallites on its surface.

[0023] Specifically, it has been found that when the crystallites on the surface of the protective film are oriented in a specific direction, the durability of the protective film is significantly reduced (i.e., the etching rate is increased). For convenience of explanation, the "specific direction" mentioned above, i.e., the orientation of the crystallites that reduces the durability of the protective film, will also be referred to as the "specific direction" hereinafter.

[0024] If the orientation of each crystallite 210 on the surface S2 of the protective film 200 were to be aligned in the specific direction, the durability of the protective film 200 against plasma could be significantly reduced.

[0025] Therefore, in this embodiment, as described above, the protective film 200 is formed so that the orientation direction of each crystallite 210 on the surface S2 of the protective film 200 is irregular and not aligned in a specific direction.

[0026] Even in such a structural member 10, the multiple crystallites 210 on the surface S2 of the protective film 200 may include those oriented in a "specific direction" that reduces the durability of the protective film 200. Such crystallites 210 oriented in a specific direction will be referred to as "crystallites 210A" below. In Figure 2, the crystallites 210A are hatched.

[0027] As described above, the surface S2 of the protective film 200 may contain crystallites 210A, but the orientation of each crystallite 210 on the surface S2 is irregular. Therefore, even if some crystallites 210A are oriented in an undesirable direction, the proportion of the crystallites 210A on the surface S2 is relatively small, as shown schematically in Figure 2. Therefore, the durability of the entire protective film 200 is averaged, ensuring sufficient durability against plasma.

[0028] The protective film 200 may be formed directly on the surface S1 of the substrate 100 as in this embodiment, or may be formed on the surface S1 of the substrate 100 via an underlayer. As such an underlayer, for example, a ceramic film formed by PVD or CVD can be used.

[0029] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise.

[0030] 10: Structural member 100: Base material 200: Protective film 210: Crystallite S1, S2: Surface

Claims

1. A structural member comprising: a substrate; and a protective film covering the surface of the substrate, wherein the protective film is a film formed from a polycrystalline material containing an alkaline earth metal oxide or an alkaline earth metal halide, and wherein the orientation of each crystallite on the surface of the protective film is not uniform but irregular.

2. The structural member according to claim 1, wherein said protective film is formed by an aerosol deposition method.

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