Structural members

Abstract

To provide a structural member equipped with a protective film with excellent particle resistance.SOLUTION: A structural member 10 comprises a substrate 100, and a protective film 200 covering a surface S1 of the substrate 100. The coarseness of a surface S1 of the substrate 100 is coarseness which becomes 70 μm or more in an average length RSm.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to structural members. [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, in a plasma etching apparatus, a protective film is formed on the surface of the substrate that constitutes the inner wall of the chamber to protect the substrate from plasma. For example, oxide ceramics such as yttrium oxide (yttria) are used as such a protective film.

[0003] When a protective film is exposed to plasma, some of the deteriorated protective film breaks down into large particles that fly away, which can have a detrimental effect on the semiconductor manufacturing process. A protective film that is less susceptible to this phenomenon will be referred to below as a "protective film with excellent particle resistance." For example, a protective film that is less susceptible to deterioration even when exposed to plasma, or a protective film that, even if it does deteriorate, breaks down into particles so small that they do not cause problems in the process (i.e., a protective film that is less likely to break down into large particles), would both be called a "protective film with excellent particle resistance."

[0004] Various film formation methods, such as PVD and CVD, can be used to form protective films on the surface of substrates. In recent years, aerosol deposition has also become popular. Using aerosol deposition and other film formation methods, it has become possible to form dense, particle-resistant protective films composed of fine crystalline particles. While forming dense, particle-resistant protective films requires a longer film formation time than conventional methods, such protective films can achieve a certain lifespan even when they are relatively thin. Therefore, efforts are being made to make the protective film relatively thin. When the film thickness is thin, the shape of the protective film surface is more strongly influenced by the shape of the substrate surface. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-160097 [Patent Document 2] Japanese Patent Publication No. 2020-050536 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to suppress particle generation, irregularities on the surface of the protective film are removed and the arithmetic mean roughness Ra is reduced. Also, in order to suppress peeling of the protective film and to obtain a dense protective film, it was thought that the surface of the substrate on which the protective film is formed needed to be a smooth surface with an arithmetic mean roughness Ra of about 0.1 μm or less.

[0007] The present inventors have discovered that a structural member with excellent particle resistance can be obtained by controlling the index in the planar direction, rather than the arithmetic mean roughness Ra, which is an index in the height direction, of the surface of a substrate on which a protective film is formed.An object of the present invention is to provide a structural member provided with a protective film with excellent particle resistance. [Means for solving the problem]

[0008] In order to achieve the above object, a structural member according to the present invention includes a substrate and a protective film covering the surface of the substrate, wherein the surface roughness of the substrate is 70 μm or more in terms of average length RSm.

[0009] According to experiments conducted by the present inventors, by making the surface of the substrate 70 μm or more in average length RSm, it is possible to obtain a structural member equipped with a protective film that has excellent particle resistance, even if, for example, the arithmetic mean roughness Ra of the surface of the substrate is greater than 0.1 μm. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a structural member provided with a protective film that has excellent particle resistance. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram schematically illustrating a cross section of a structural member according to the present embodiment. [Figure 2] FIG. 2 is a diagram for explaining the surface shape of a substrate. [Figure 3] FIG. 10 is a diagram showing the results of a film formation test. [Figure 4] This is an image of the surface of the substrate photographed using a laser microscope. [Figure 5] This is an image of the surface of the substrate photographed using a laser microscope. [Figure 6] This is an image of the surface of the substrate photographed using a laser microscope. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] 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 use in semiconductor manufacturing apparatuses.

[0014] 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 the plasma.

[0015] The substrate 100 is a member that occupies substantially the entire structural member 10. In this embodiment, the substrate 100 is a ceramic sintered body containing high-purity aluminum oxide (Al2O3), but it may be made of a different type of ceramic. The substrate 100 may also be made of a material other than ceramic. In this embodiment, the surface S1 of the substrate 100 is flat, but the surface S1 may have through holes, an inclined surface, or the like.

[0016] 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 configured as a film containing polycrystalline yttrium oxide (yttria: Y2O3), but it may also be a ceramic film made of a different material. The thickness of the protective film 200 is set appropriately depending on the length of time over which durability is required to be maintained, etc. In this embodiment, the thickness of the protective film 200 is, for example, about 10 μm, but it may be thinner.

[0017] The protective film 200 of this embodiment is formed on the surface S1 of the substrate 100 by using a PVD method or an aerosol deposition method.

[0018] It is known that if the arithmetic surface roughness Ra of the surface S1 of the substrate 100 is too large, the protective film 200 cannot be formed or the protective film peels off. For this reason, it is considered necessary to smooth the surface S1 in advance, for example, before forming the film. Conventionally, the surface S1 has been polished or otherwise processed so that the surface S1 has a smooth surface with an arithmetic mean roughness Ra of 0.1 μm or less. Polishing or otherwise processing the surface S1 to achieve such a smooth surface often requires time and effort. Particularly when the thickness of the protective film is relatively thin, the surface shape of the protective film is strongly affected by the surface shape of the substrate, and therefore, it has been considered necessary to strictly control the surface shape of the substrate.

[0019] The inventors have conducted numerous experiments and studies to determine what conditions the shape of the surface S1 must satisfy in order to form the protective film 200. As a result, they have discovered a new finding: a structural member with excellent particle resistance can be obtained by controlling the index in the planar direction, rather than the arithmetic mean roughness Ra, which is an index in the height direction, of the surface S1 of the substrate 100. It is also preferable that the surface S1 of the substrate in the structural member has a root-mean-square slope Rdq of 15 μm or less.

[0020] 2 is a schematic diagram showing a cross section of the substrate 100 before film formation. The "cross section" here refers to a cross section of the substrate 100 cut along a plane perpendicular to the surface S1.

[0021] The roughness of the surfaces S1 shown in Figures 2(A) and 2(B) is approximately the same in terms of arithmetic mean roughness Ra, specifically, Ra 0.40 μm. However, the surface S1 in Figure 2(B) has fewer fine irregularities than the example in Figure 2(A). This difference in shape does not appear as a difference in the arithmetic mean roughness Ra, which is an index in the height direction. Therefore, although the two surfaces S1 shown in Figure 2 differ from each other in shape, as described above, both have an Ra of 0.40 μm. On the other hand, the surface shapes in Figures 2(A) and 2(B) can be distinguished by the mean length RSm or root-mean-square slope Rdq, which are indexes in the planar direction.

[0022] "Mean length RSm" represents the average length of the profile curve elements in a cut surface roughness curve such as that shown in Figure 2. "Root mean square slope Rdq" is an index for evaluating the magnitude of the local slope angle, and represents the root mean square of the local slope in a cut surface roughness curve such as that shown in Figure 2. The specific definitions and measurement methods for the mean length RSm and root mean square slope Rdq are as specified in JIS B 0601:2013.

[0023] In the example of Figure 2(A), the surface S1 has many small irregularities, which shortens the length of the profile curve elements and results in a calculated average length RSm that is less than 70 μm. It has been found that when the surface of a structural component's substrate has the shape shown in Figure 2(A), the structural component's particle resistance is insufficient due to factors such as peeling of the protective film and a decrease in the density of the protective film. Furthermore, the root-mean-square slope Rdq of surface S1 becomes greater than 15 μm.

[0024] On the other hand, in the example of Figure 2(B), the surface S1 has fewer fine irregularities, so the length of the profile curve element is longer, and the calculated average length RSm is greater than 70 μm. When the surface of the substrate of a structural component has the shape shown in Figure 2(B), peeling of the protective film and a decrease in its density can be suppressed, resulting in a structural component with high particle resistance. In other words, it was found that it is effective to control RSm, rather than the arithmetic mean roughness Ra, of the substrate surface of the structural component shown in Figure 2(B), to a predetermined value or less. Furthermore, the root-mean-square slope Rdq of surface S1 is reduced to 15 μm or less.

[0025] The inventors prepared three substrate 100 samples with different surface S1 shapes, and prepared structural members with protective films 200 formed on the respective surfaces S1. The substrate 100 was an alumina substrate, and the protective film was an yttria film. The arithmetic mean roughness Ra, mean length RSm, and root-mean-square slope Rdq were measured for the surface S1 of each substrate at the fracture surface of the structural member. The arithmetic mean roughness Ra, mean length RSm, and root-mean-square slope Rdq were also measured for each surface S1 before film formation, but in this test, the surface shape of the substrate in the structural member (after protective film formation) was substantially the same as the surface shape of the substrate before film formation.

[0026] The arithmetic mean roughness Ra, mean length RSm, and root mean square slope Rdq of the surface of a substrate in a structural member are measured by known methods, such as calculating the surface roughness from a cross-sectional profile of the substrate surface obtained from a cross-section of a sample, measuring the surface roughness using a white light interference microscope or a confocal laser microscope, or measuring the substrate itself before applying a film using a laser microscope or a contact surface roughness meter. As an example, first, a predetermined area of ​​the surface S1 to be measured was photographed using a laser microscope. A KEYENCE VK-X3000 laser microscope was used. A 50x objective lens was used, and 1000x images were obtained.

[0027] Next, the arithmetic mean roughness Ra, mean length RSm, and root-mean-square slope Rdq were calculated from the profile data obtained from the image (data showing the shape of the surface S1 at a cut surface similar to that shown in Figure 2). The "reference length" indicating the measurement range was set to 250 μm. The cutoff λs was set to 0.8 μm, and calculations were performed using stylus mode. The stylus tip radius was set to 2 μm, and the stylus tip angle was set to 60°. Measurements were performed at 20 different positions on the surface S1, and the arithmetic mean roughness Ra, mean length RSm, and root-mean-square slope Rdq were calculated by averaging the obtained values.

[0028] Figure 3 shows the evaluation results. For sample No. 1, the surface S1 before coating was subjected to surface grinding and then further polished by lapping. After the protective film was formed on this sample, the arithmetic mean roughness Ra of the substrate surface S1 was 0.10 μm, the mean length RSm was 93.30 μm, and the root mean square slope Rdq was 9.2 μm. Figure 4 shows an image of the surface S1 of sample No. 1 taken with a laser microscope.

[0029] For sample No. 2, the surface S1 before coating was subjected to surface grinding, followed by free abrasive processing using finer abrasive grains that did not remove the grinding waviness. After the protective film was formed on this sample, the arithmetic mean roughness Ra of the substrate surface S1 was 0.44 μm, the mean length RSm was 90.58 μm, and the root-mean-square slope Rdq was 8.2 μm. Figure 5 shows an image of the surface S1 of sample No. 2 taken with a laser microscope.

[0030] In sample No. 3, the surface S1 before coating was subjected to only surface grinding. After the protective film was formed on this sample, the arithmetic mean roughness Ra of the substrate surface S1 was 0.57 μm, the mean length RSm was 27.80 μm, and the root mean square slope Rdq was 19.6 μm. Figure 6 shows an image of the surface S1 of sample No. 3 taken with a laser microscope.

[0031] As shown in FIG. 3, both Samples No. 2 and 3 have a roughness exceeding 0.1 μm in terms of the arithmetic mean roughness Ra, which is an index of the height direction of the surface S1.

[0032] In sample No. 2, the average length RSm of each surface S1 is large, at over 90 μm, and there are fewer fine irregularities like those in the example in Figure 2(A). In contrast, in sample No. 3, the arithmetic mean roughness Ra of surface S1 is large, at over 0.1 μm, and the average length RSm is small, at just under 30 μm, and there are many fine irregularities like those in the example in Figure 2(A). As a result, the particle resistance of structural member No. 3 is inferior to that of Nos. 1 and 2. On the other hand, there was no significant difference in the particle resistance of sample No. 1, which has an arithmetic mean height Ra of around 0.1 μm, and sample No. 2, which has an arithmetic mean height Ra of more than 0.1 μm.

[0033] Thus, it was confirmed that even in a sample in which the arithmetic mean roughness Ra of the surface S1 exceeds 0.1 μm, high particle resistance can be achieved in the structural member if the mean length RSm of the surface S1 is sufficiently large. According to experiments separately conducted by the present inventors, it was confirmed that good particle resistance can be achieved in a structural member in which the roughness of the surface S1 in the mean length RSm is 70 μm or more.

[0034] Various known methods can be used to process the surface S1 to a roughness of 70 μm or more in terms of average length RSm. Examples include grinding stone polishing, lapping polishing, buffing, barrel polishing, electrolytic polishing, and sandblasting. By appropriately selecting the type and size of the abrasive used in polishing and adjusting the polishing time, the average length RSm of the surface S1 can be made 70 μm or more before the arithmetic mean roughness Ra of the surface S1 becomes 0.1 μm or less. This simplifies the surface treatment of the substrate 100 before film formation, and improves productivity, compared to processing the surface S1 until the arithmetic mean roughness Ra of the surface S1 becomes 0.1 μm or less.

[0035] Even if the surface S1 of the substrate 100 is not a flat surface but is an uneven surface such as a curved surface, it is possible to measure the average length RSm and the like of the surface S1. When the surface S1 is an uneven surface, the average length RSm and the like may be measured using, for example, the following method.

[0036] First, a portion of the substrate 100 is cut out to create a plate-shaped sample including a surface S1 that is a non-flat surface. The sample may be prepared, for example, so that the entire main surface is surface S1 and has a shape of 20 mm x 20 mm. By cutting out a portion of the substrate 100 as such a small sample, the surface S1 to be measured can be made closer to a flat surface, making it easier to observe the surface using a laser microscope, etc.

[0037] As long as the cut surface S1 can be considered to be a generally flat surface, the size of the sample may be different from the above. For example, if the surface S1 of the substrate 100 is curved and has a relatively large radius of curvature, the substrate 100 may be cut out to produce a sample of a relatively large size. On the other hand, if the radius of curvature of a portion of the surface S1 is relatively small, the sample may be created by cutting the substrate 100 so as to avoid that portion.

[0038] After preparing the small sample pieces as described above, the average length RSm of the surface S1 and the like can be measured using the same method as described above.

[0039] Even if part or all of surface S1 is curved, observation can often be made with almost no effect from the shape of surface S1 if the magnification of measurement using a laser microscope is about 1000. If the effect of the shape of surface S1 is a concern, tilt correction and background correction can be performed as necessary.

[0040] If the sample vibrates during measurement, it becomes difficult to accurately measure the average length RSm of the surface S1. Therefore, the contact surface of the sample, i.e., the surface opposite to the surface S1, can be processed to have a shape (e.g., a flat surface) that allows stable placement. This suppresses sample vibration, making it possible to measure the average length RSm of the surface S1 with high accuracy.

[0041] 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. [Explanation of symbols]

[0042] 10: Structural Components 100: Substrate 200: Protective film S1, S2: Surface

Claims

1. A structural member used in an environment exposed to plasma, A substrate; a protective film covering the surface of the substrate and protecting the surface from plasma; A structural member characterized in that the surface roughness of the substrate is 70 μm or more in terms of average length RSm.

2. 2. The structural member according to claim 1, wherein the surface has an arithmetic mean roughness Ra of more than 0.1 [mu]m.

3. 2. The structural member according to claim 1, wherein the substrate is formed from a material containing aluminum oxide.

4. 2. The structural member according to claim 1, wherein said protective film is formed of a material containing yttrium oxide.

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

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