JP7580925B2 - Joint of SiC-coated graphite members - Google Patents

Description

The present invention relates to a joint of SiC-coated graphite members in which a composite material having a CVD-SiC layer on the surface of a substrate is bonded with a CVD-SiC layer.

In order to supply high-quality products in semiconductor manufacturing, thereby improving the yield of semiconductor products and ensuring stable operations, composite materials in which a CVD-SiC layer is coated on the surface of a graphite base material are widely used for semiconductor device parts such as susceptors, jigs, and furnace components used in the heat treatment process of silicon wafers, etc. Materials such as graphite and SiC do not dope silicon even when mixed with silicon, and do not change the electrical conductivity, so they have little effect on the quality of the resulting wafers, and both SiC and graphite are stable at high temperatures and therefore wear out little, making them suitable for use as semiconductor device parts.

Graphite is easy to process and can easily be made into complex shapes, but it has the drawback of being easily worn away by contact with oxygen, water, hydrogen, etc. On the other hand, SiC is characterized by being easy to form a thin oxide film on its surface and being resistant to wear from oxygen, water, hydrogen, etc., but it has the drawback of being hard and difficult to process. A composite material in which a CVD-SiC layer is formed on the surface of a substrate made of graphite makes good use of these characteristics and drawbacks. With such composite materials, the substrate itself is very easy to process, so complex shapes can be easily obtained, and the surface is covered with a CVD-SiC layer, making it a durable composite material that can be used in a variety of atmospheres.

Patent Document 1 describes a component for semiconductor manufacturing equipment, which is a tube for a semiconductor diffusion furnace having a shape in which one end side of a long cylindrical portion is tapered, and which is characterized in that a tapered portion made of silicon carbide or graphite is joined to one end of a long cylinder made of silicon carbide or graphite by a CVD film of silicon carbide, and at least the entire inner circumferential surface of the tube is coated with the CVD film.
It is described that such semiconductor manufacturing equipment parts are covered with a high-purity, dense SiC coating, and that the gaps between the assembled parts are filled with CVD precipitates and joined together, eliminating any rattling of the parts.

Japanese Unexamined Patent Publication No. 62-200722

However, in the above-mentioned invention, since the gap is filled with the CVD-SiC layer, a sufficient thickness of the CVD-SiC layer is required to create a sufficient gap in advance and completely fill the gap. However, there is a problem that the dimensional accuracy deteriorates when the CVD-SiC layer is made thick.
In addition, when a thin CVD-SiC layer is used, the gaps cannot be filled sufficiently, resulting in a trade-off in reduced airtightness, and there was a problem in that it was difficult to obtain a bonded body of SiC-coated graphite material that simultaneously satisfied the bonding strength, dimensional accuracy, and airtightness requirements.

In view of the above problems, the present invention aims to provide a bonded body of SiC-coated graphite material that has high bonding strength, excellent dimensional accuracy, and high airtightness.

In order to solve the above problems, a joined body of SiC-coated graphite members of the present invention is a joined body of SiC-coated graphite members in which a CVD-SiC layer covers a surface of a base material made of graphite, and a plurality of the base materials are joined by the CVD-SiC layer via a mating surface,
At least one of the substrates has a convex portion on one end side of the combination surface that is higher than the surrounding area, and a concave portion on the other end side that opens to the outside when combined with the other substrate, and the CVD-SiC layer has a first bonding portion that bonds the substrates along the outer surface of the bonded body outside the convex portion of the combination surface, and a second bonding portion that penetrates into the concave portion outside the concave portion of the combination surface and bonds the substrates to each other with their opposing surfaces.
The above-mentioned mating surfaces refer to the surfaces that face each other when the substrates having the CVD-SiC layers to be joined are combined, and include a convex portion and a concave portion.

According to the joined body of SiC-coated graphite members of the present invention, one end of the joining surface has a convex part higher than the surrounding area, and the CVD-SiC layer joins the substrates along the outer surface of the joined body outside the convex part of the joining surface, so that the part sandwiched between the convex parts of the substrates is unlikely to have a gap, and the CVD-SiC layer joins the substrates along the outer surface of the joined body on the outside, so that a first joining part of the thin and highly airtight CVD-SiC layer is obtained on one end of the joining surface. Also, on the other end side, when joined with another substrate, the CVD-SiC layer penetrates into the recessed part that opens to the outside, and a second joining part is provided that joins the opposing surfaces of the substrates, so that the joining part can be firmly joined, and a strong joining can be obtained.
In other words, according to the joined body of SiC-coated graphite members of the present invention, despite being a thin CVD-SiC layer, by dividing the roles of maintaining airtightness at the first joint on one end side and ensuring bonding strength at the second joint on the other end side, it is possible to provide a joined body of SiC-coated graphite members that has high bonding strength and airtightness.

In the bonded SiC-coated graphite member of the present invention, it is desirable that the combined surface has a CVD-SiC layer on the surface of the substrate made of both graphites.

The CVD-SiC layer of the bonded SiC-coated graphite member of the present invention is composed of an outer CVD-SiC layer and an inner CVD-SiC layer. Specifically, the surface of each graphite substrate is covered with a coating layer of the inner CVD-SiC layer to form a SiC-coated member, and the outer CVD-SiC layer is obtained by bonding each of the SiC-coated members. Note that in areas other than the combined surfaces, the inner CVD-SiC layer and the outer CVD-SiC layer are simply laminated and integrated.

In a joint of SiC-coated graphite members, the coating layer of the outer CVD-SiC layer is formed thicker toward the entrance side and thinner toward the inside in the recess having the CVD-SiC layer on the other end side, so cavities are likely to form toward the back. Therefore, if the inner CVD-SiC layer is not formed on the surface of the substrates made of both graphite, exposed graphite is likely to form. However, in the joint of SiC-coated graphite members of the present invention, if the surfaces of the substrates made of both graphite have an inner CVD-SiC layer on the above-mentioned combined surface, the coating layer made of the inner CVD-SiC layer is formed around the substrates before they are combined, so that exposed graphite can be eliminated, and a second joint can be formed by the outer CVD-SiC layer that penetrates into the recess and joins the opposing surfaces of the SiC-coated graphite members.

In the bonded body of SiC-coated graphite members of the present invention, it is preferable that the CVD-SiC layer on the surface of the top of the protrusion is a polished surface.
The surface of the CVD-SiC layer formed on the substrate is rough, hard, and difficult to process, so unless a polished surface is formed on the inner CVD-SiC layer on the surface of the top of the convex portion, it is difficult to obtain a highly airtight joint even if the CVD-SiC layers formed on the surfaces of the convex portions are pressed together.
However, in the joined SiC-coated graphite members of the present invention, if the CVD-SiC layer on the surface of the top of the convex portion is a polished surface, the surface of the CVD-SiC layer becomes flat with high precision, and a highly airtight SiC-coated graphite member can be easily obtained.

In the joined SiC-coated graphite members of the present invention, it is desirable that the surface of the CVD-SiC layer formed on the top of the convex portion be flush with the surface of the CVD-SiC layer formed on the surface of the other substrate.
In the bonded body of SiC-coated graphite members of the present invention, when the surface of the CVD-SiC layer formed on the top of the convex portion is on the same plane as the surface of the CVD-SiC layer formed on the surface of the other substrate, the surfaces of the CVD-SiC layers formed on the convex portions are in a single plane. Therefore, processing after film formation can be handled by simply flattening, and the portion where the convex portion is formed becomes a highly accurate combination surface without gaps through simple processing. Therefore, a SiC-coated graphite member with high airtightness is obtained.

In the joined body of SiC-coated graphite members of the present invention, it is desirable that the difference in distance between the ends of the opposing base members on the convex portion side and the ends on the other side at the joining surfaces be 40 to 100 μm.
In the joined body of SiC-coated graphite members of the present invention, when the difference in distance between the ends of the opposing base members on the convex side and the ends of the opposing base members on the other side at the joining surfaces is 40 μm or more, a CVD-SiC layer penetrating into the recesses is easily obtained, and a joined body of high strength is obtained. When the difference in distance is 100 μm or less, the recesses are easily filled with a thin CVD-SiC layer, and a joined body of SiC-coated graphite members with high dimensional accuracy is obtained.

In the method for producing a joined body of SiC-coated graphite members of the present invention, the ratio of the area of the tops of the protrusions to the area of the joining surfaces is preferably 5 to 60%.
In the method for producing a joint of SiC-coated graphite members of the present invention, when the ratio of the area of the tops of the protrusions to the area of the mating surfaces is 5% or more, fewer cavities are formed and stress concentration is unlikely to occur around the protrusions, making it possible to make it difficult for distortion to be applied to the CVD-SiC layer on one end side. Also, when the ratio of the area of the tops of the protrusions to the area of the mating surfaces is 60% or less, the joining surface can be made large, and a high-strength joint can be obtained.

The SiC-coated graphite member joint of the present invention has a thin CVD-SiC layer, but by dividing the roles of maintaining airtightness at the first joint on one end and ensuring joint strength at the second joint on the other end, it is possible to provide a SiC-coated graphite member joint that has high joint strength and airtightness.

FIG. 1(a) is a perspective view showing an example of a substrate for a bonded body of SiC-coated graphite members, and FIG. 1(b) is a cross-sectional view of the substrate shown in FIG. 1(a) taken along line AA. FIG. 2 is a cross-sectional view that typically shows a SiC-coated graphite member on which a CVD-SiC layer is formed. FIG. 3(a) is a perspective view showing a schematic diagram of a joined body of SiC-coated graphite members of the present invention, FIG. 3(b) is a cross-sectional view taken along line B-B of the joined body of SiC-coated graphite members shown in FIG. 3(a), and FIG. 3(c) is a cross-sectional view in which the distinction between the inner CVD-SiC layer and the outer CVD-SiC layer in the cross-sectional view shown in FIG. 3(b) has been eliminated. FIG. 4 is a cross-sectional view showing a schematic configuration of two SiC-coated graphite members each having an inner CVD-SiC layer formed thereon. 5(a) to 5(d) are cross-sectional views each showing a schematic process of a method for producing a joined body of SiC-coated graphite members according to another embodiment of the present invention. FIG. 6( a ) is a perspective view illustrating a joined body of SiC-coated graphite members of the present invention according to another embodiment, and FIG. 6( b ) is a cross-sectional view taken along line CC of the joined body of SiC-coated graphite members shown in FIG. 6( a ). FIG. 7( a ) is a perspective view illustrating a joined body of SiC-coated graphite members of the present invention according to another embodiment, and FIG. 7( b ) is a cross-sectional view taken along line D-D of the joined body of SiC-coated graphite members shown in FIG. 7( a ). FIG. 8( a ) is a polarizing microscope photograph showing a cross section of a joined body of SiC-coated graphite members of the present invention, and FIG. 8( b ) is a cross-sectional view showing a schematic configuration of the joined body of SiC-coated graphite members shown in FIG. 8( a ). 9(a) to 9(d) are cross-sectional views showing examples of combinations of SiC-coated graphite members other than the combinations of SiC-coated graphite members shown in FIGS. 1 to 7, respectively.

The bonded body of SiC-coated graphite members of the present invention will be described in detail below in each embodiment, but the present invention is not limited to the following embodiments, and can be modified as appropriate within the scope of the present invention.

The joined body of SiC-coated graphite members of the present invention is a joined body of SiC-coated graphite members in which a CVD-SiC layer covers a surface of a base material made of graphite, and a plurality of the base materials are joined by the CVD-SiC layer via a mating surface,
At least one of the substrates has a convex portion on one end of the combination surface that is higher than the surrounding area, and a concave portion on the other end that opens to the outside when combined with the other substrate, and the CVD-SiC layer has a first bonding portion that bonds the substrates along the outer surface of the bonded body outside the convex portion of the combination surface, and a second bonding portion that penetrates into the concave portion outside the concave portion of the combination surface and bonds the substrates to each other with their opposing surfaces.

In the bonded SiC-coated graphite members of the present invention, the CVD-SiC layer is composed of an outer CVD-SiC layer and an inner CVD-SiC layer. Specifically, the surface of each graphite substrate is covered with an inner CVD-SiC coating layer to form a SiC-coated member, and the outer CVD-SiC layer is obtained by bonding each of the SiC-coated members. Note that in areas other than the combined surfaces, the inner CVD-SiC layer and the outer CVD-SiC layer are simply stacked and integrated.

At the combined surface, the inner CVD-SiC layers are not bonded because they are manufactured separately, but are bonded by the outer CVD-SiC layer to obtain a bonded body. For the purposes of the following explanation, the CVD-SiC layer may be divided into an inner CVD-SiC layer and an outer CVD-SiC layer, but the outer CVD-SiC layer tends to form continuously even when coated on top of the inner CVD-SiC layer, and the boundary between them is not necessarily clearly identifiable.

First, the substrate constituting the bonded body of SiC-coated graphite members will be described.
FIG. 1(a) is a perspective view showing an example of a substrate for a bonded body of SiC-coated graphite members, and FIG. 1(b) is a cross-sectional view of the substrate shown in FIG. 1(a) taken along line AA.

This substrate 10 is a substrate that constitutes a joint of tubular SiC-coated graphite members, which is one embodiment of the present invention, and has a groove 15 that serves as a through hole in the center, and walls 12 that form a combination surface on both sides of the groove. The walls 12 on both sides are composed of a convex portion 13 and a concave portion 14, and the top 13a of the convex portion 13 is flat. The convex portion 13 and the concave portion 14 are stepped, and the convex portion 13 is formed one step higher than the concave portion 14.

The type of graphite that constitutes this substrate is not particularly limited, but isotropic graphite material with low anisotropy is preferable. When such isotropic graphite material with low anisotropy is used as the substrate, there is little deviation in mechanical properties depending on the direction, so damage is less likely to occur and it can be used stably for a long period of time.

The isotropic graphite material is a graphite material having an isotropic structure and characteristics, and can be produced, for example, by CIP (Cold Isostatic Press). Specifically, for example, the raw material powder of the isotropic graphite material is packed into a rubber bag in a pressure vessel, and molded by applying pressure with water or the like, and then sintered and graphitized.
In the above-mentioned isotropic graphite material, the average particle size of the raw material powder is, for example, 10 to 50 μm, and the isotropic graphite material is characterized by having a fine structure.

When the substrate is made of graphite, it is preferable that the material has a porosity of 5 to 20% and a bulk density of 1.70 to 1.90 g/cm ³ .
When the porosity of the substrate is 5% or more, the substrate contains open pores, so that the inner CVD-SiC layer is easily impregnated into the open pores, and the inner CVD-SiC layer is firmly attached to the substrate due to the anchor effect. On the other hand, when the porosity of the substrate is 20% or less, the pore content is not too high, so that the substrate itself has high mechanical strength.

Furthermore, when the bulk density of the substrate is 1.70 g/ ^cm3 or more, the substrate has excellent mechanical properties even if it has pores. When the bulk density of the substrate is 1.90 g/ ^cm3 or less, the substrate contains open pores in an appropriate range, the inner CVD-SiC layer is easily filled into the open pores, and the coating layer made of the inner CVD-SiC layer has excellent adhesion.

The substrate may be a C/C composite material reinforced by filling gaps in the carbon fiber aggregate with a carbon matrix. The type of carbon fiber as the aggregate is not particularly limited, and may be PAN-based carbon fiber or pitch-based carbon fiber.
The C/C composite material can be obtained, for example, by depositing pyrolytic carbon on a carbon fiber substrate, impregnating a carbon fiber substrate with a resin and then carbonizing it, etc. Since the C/C composite material is reinforced with high-strength carbon fibers, it has fracture toughness even at high temperatures and can maintain its mechanical strength.

The shape of the substrate is not particularly limited, but as described above, at least one of the substrates (hereinafter referred to as the one substrate) has a convex portion that is higher than the surrounding area and a concave portion that is relatively lower than the convex portion on one end side of the mating surface.
The top of the convex portion is preferably a flat surface. The concave portion may be a flat surface that is one step lower than the convex portion, and the convex portion and the concave portion may be stepped, or an inclined surface may be formed so as to gradually decrease in height from the convex portion.
The combination surface of another substrate to be combined with the substrate may be a simple flat surface, and may have the same shape as the substrate, but the two do not necessarily have to have the same shape.

In the case of the bonded SiC-coated graphite members of the present invention, a bonded SiC-coated graphite member of the present invention is manufactured using a SiC-coated graphite member having a CVD-SiC layer formed on the surface of the base material.

Figure 2 is a cross-sectional view that shows a schematic diagram of a SiC-coated graphite component on which a CVD-SiC layer is formed. Note that, since it is difficult to see the state of the coating in a perspective view of a SiC-coated graphite component, the following explanation will be based on the cross-sectional view shown above.

Furthermore, in the SiC-coated graphite member 20 shown in FIG. 2, the inner CVD-SiC layer 26 is formed with a substantially uniform thickness over the entire surface, including the bottom surface 10a, so the basic shape is the same as that of the substrate. Therefore, the relevant parts of the SiC-coated graphite member 20 having the inner CVD-SiC layer will also be referred to as the groove portion 25, wall portion 22, protrusion portion 23, and recess portion 24.

That is, in this SiC coated graphite member 20 as well, a groove 25 serving as a through hole is formed in the center, and walls 22 for forming a mating surface are formed on both sides of the groove 25 .
The wall portions 22 on both sides have a protrusion 23 that is higher than the surrounding area and a recess 24 that is lower than the protrusion 23 on one end side.

Figure 3(a) is a perspective view showing a schematic diagram of a bonded body of SiC-coated graphite members of the present invention using the above-mentioned SiC-coated graphite members, Figure 3(b) is a cross-sectional view taken along line B-B of the bonded body of SiC-coated graphite members shown in Figure 3(a), and Figure 3(c) is a cross-sectional view in which the distinction between the inner CVD-SiC layer and the outer CVD-SiC layer in the cross-sectional view shown in Figure 3(b) has been eliminated.

In the SiC-coated graphite member joint 200 of the present invention, as shown in Figures 3(a) and (b), the joint is formed by combining SiC-coated graphite members 20 of the same shape via their joining surfaces and forming a CVD-SiC layer around them.

The SiC-coated graphite member 20 has a convex portion 23 that is higher than the surrounding area on one end side of the combination surface, and a concave portion 24 that opens to the outside on the other end side, and the joined body 200 of the SiC-coated graphite members has a first joining portion 28a that joins along the outer surface of the joined body 200 of the SiC-coated graphite members in region A outside the convex portion 23 of the combination surface, and has a second joining portion 28b in region B that penetrates into the concave portion 24 of the combination surface from the outside and joins the opposing surfaces of the substrates together.
In the drawing, the region where the first bonded portion 28a is formed is shown as region A, and the region where the second bonded portion 28b is formed is shown as region B.

The first bond 28a and the second bond 28b are formed in the outer CVD-SiC layer 28, but in the manufactured SiC-coated graphite member bond 200, the two CVD-SiC layers are integrated, and it is difficult to identify the boundary between the two CVD-SiC layers.
Therefore, the produced joint of SiC-coated graphite members has substrates of the above-mentioned shape embedded inside with their protrusions facing each other, a CVD-SiC layer formed on the surface, a through hole with a rectangular cross-section perpendicular to the length direction, and a tubular body with a constant tube thickness.

Therefore, as shown in FIG. 3(c), in the joined body 200 of SiC-coated graphite members of the present invention, when viewed from the center of the substrate 10 constituting the joined body 200 of SiC-coated graphite members, the substrate 10 has a convex portion 13 on one end of the joining surface that is higher than the surrounding area and a concave portion 14 on the other end that opens to the outside, and the CVD-SiC layer 27 has a first joining portion that joins along the outer surface of the outside of the convex portion 13, and a second joining portion that penetrates into the concave portion of the joining surface from the outside and joins the opposing surfaces of the substrates. Note that the portion where the top 23a of the convex portion 23 abuts is not joined even after manufacturing, because it is difficult for the raw material gas to penetrate into the inside.

Next, a method for producing a bonded body of SiC-coated graphite members according to the present invention will be described.
The bonded body of SiC-coated graphite members of the present invention is manufactured through an inner CVD-SiC layer forming step, an assembling step, and a bonding step. Each step will be described below.

(Inner CVD-SiC layer formation process)
In the inner CVD-SiC layer forming step, an inner CVD-SiC layer is formed on the surface of the base material shown in FIG.
The method for forming the inner CVD-SiC layer by the CVD method is not particularly limited, and may be a thermal CVD method, a plasma organic CVD method, a photo CVD method, a low pressure CVD method, an organic metal CVD method, a CVI method (chemical vapor impregnation method), or the like. ) etc.

When the CVI method is used, the graphite substrate is heated to about 800 to 1400°C, and a source gas consisting of an organosilane gas such as methyltrichlorosilane is circulated around the substrate or sprayed onto the substrate to form an inner CVD-SiC layer on the surface or in the open pores of the substrate. The source gas may be diluted with an inert gas such as argon or hydrogen.
By setting conditions that facilitate impregnation into the open pores and using the CVI method, the inner CVD-SiC layer can penetrate into the open pores of the substrate, forming a CVD-SiC layer that is difficult to peel off.

The thickness of the inner CVD-SiC layer to be formed is preferably 20 to 200 μm.
The inner CVD-SiC layer does not have to be formed on the entire surface of the substrate made of graphite, but it is preferable that the inner CVD-SiC layer is formed on the entire surface.
By undergoing this inner CVD-SiC layer forming step, the SiC-coated graphite member 20 shown in FIG. 2 is manufactured.

In the present invention, since graphite is used as the substrate, processing can be easily carried out before the inner CVD-SiC layer is formed, and a SiC-coated graphite component having a substrate of any shape can be obtained.
In the present invention, inner CVD-SiC layers are also formed on a plurality of other substrates to be joined, thereby producing a plurality of SiC-coated graphite members each having an inner CVD-SiC layer formed thereon.

(Combination process)
In the combining step, a plurality of SiC-coated graphite members having inner CVD-SiC layers on their combining surfaces are combined.
FIG. 4 is a cross-sectional view showing a schematic configuration of two SiC-coated graphite members each having an inner CVD-SiC layer formed thereon.
As shown in Fig. 4, two SiC-coated graphite members 20 are combined so that the tops 23a of the protrusions 23 constituting the combining surface abut against each other. The combining surface refers to both the protrusions 23 and the recesses 24. This is because the recesses 24 form an outer CVD-SiC layer and play an important role in joining the two SiC-coated graphite members.

In Figure 4, two SiC-coated graphite members 20 (substrates 10) of exactly the same shape and configuration are combined, but the other SiC-coated graphite member may have a different shape as long as it has a surface that can abut against the convex portion of one SiC-coated graphite member and a concave portion that is open to the outside is formed by combining the two.
In addition, three or more SiC-coated graphite members, including one SiC-coated graphite member, may be combined, so long as the structure is such that the members are joined by combining multiple SiC-coated graphite members and then forming an outer CVD-SiC layer.

(Joining process)
In the bonding process, the assembled SiC-coated graphite members are further covered from the outside with an outer CVD-SiC layer.

The method for forming the outer CVD-SiC layer is the same as the method for forming the inner CVD-SiC layer, and involves heating the graphite substrate to approximately 800 to 1400°C, and either circulating a source gas consisting of an organosilane gas such as methyltrichlorosilane around the SiC-coated graphite member or spraying it onto the SiC-coated graphite member to form the outer CVD-SiC layer on the surface of the SiC-coated graphite member.
In this manner, a bonded body 200 of SiC-coated graphite members shown in FIGS. 3( a ) and 3 ( b ) is produced.

5(a) to 5(d) are cross-sectional views each showing a schematic diagram of each step in manufacturing a joined body of SiC-coated graphite members according to another embodiment of the present invention.
In Figure 5 (a), two identically shaped SiC-coated graphite members 30 each having an inner CVD-SiC layer 36 are being combined, but the surface of the tops 33a of the convex portions 33 of the inner CVD-SiC layer 36 tends to become rough, and even when the tops 33a are brought into contact with each other, gaps tend to form, making it difficult to maintain airtightness of the combined portion even when an outer CVD-SiC layer is formed.

Therefore, as shown in FIG. 5(b), the top 33a is polished to form a flattened top 330a having a flat surface. Then, as shown in FIG. 5(c), two SiC-coated graphite members 30 are combined so that the flattened tops 330a abut against each other, and an outer CVD-SiC layer 38 is formed as shown in FIG. 5(d). In this way, by forming the outer CVD-SiC layer 38, a joint 300 of SiC-coated graphite members can be formed.

In this embodiment, the outer CVD-SiC layer 38 is not formed over the entire inside of the recess 34, but is formed only at the entrance of the recess 34, and a cavity 39 is formed inside.
However, a first bonding portion 38a is formed in region A, and a second bonding portion 38b is formed in region B, penetrating into recess 34 and bonding the two SiC-coated graphite members, resulting in a bonded body 300 of SiC-coated graphite members in which the two SiC-coated graphite members are firmly bonded together.

Looking at the manufactured joint of SiC-coated graphite members, a CVD-SiC layer of a predetermined thickness is formed on the surface of a base material having a convex portion and a concave portion, and the CVD-SiC layer has a first joint portion that joins the base material along the outer surface of the joint outside the convex portion of the combined surface, and a second joint portion that penetrates into the concave portion outside the concave portion of the combined surface and joins the opposing surfaces of the base material, resulting in a joint of SiC-coated graphite members with a cavity formed inside. Note that the flattened top portion 330a is not joined even after it is manufactured, because it is difficult for the raw material gas to penetrate into the inside.

Figure 6(a) is a perspective view showing a schematic diagram of a bonded body of SiC-coated graphite members according to another embodiment of the present invention, and Figure 6(b) is a cross-sectional view of the bonded body of SiC-coated graphite members shown in Figure 6(a) taken along line C-C.

In the SiC-coated graphite member joint 400 of this embodiment, the SiC-coated graphite member 40 having the substrate 41 and the inner CVD-SiC layer 46 is cylindrical in shape, with the convex portion 43 forming one end being formed on the central axis side and the concave portion 44 forming the other end being formed on the outer periphery side.
The top of the convex portion 43 is polished to remove any protrusions formed on the surface of the CVD-SiC layer and to provide a flat surface.

In this SiC-coated graphite member joint 400, as shown in FIG. 6(b), two SiC-coated graphite members 40 are combined so that the tops of the convex portions 43 abut against each other, and an outer CVD-SiC layer 48 is formed on the inside and outer periphery of the cylinder.
In this embodiment, the outer CVD-SiC layer 48 is not formed over the entire inside of the recess 44, but is formed only at the entrance of the recess 44, and a cavity 49 is formed inside.
However, a first bonding portion 48a is formed in region A, and a second bonding portion 48b is formed in region B, penetrating into recess 44 and bonding the two SiC-coated graphite members, resulting in a bonded body 400 of SiC-coated graphite members in which two SiC-coated graphite members 40 are firmly bonded together.

Figure 7(a) is a perspective view showing a schematic diagram of a bonded body of SiC-coated graphite members according to another embodiment of the present invention, and Figure 7(b) is a cross-sectional view of the bonded body of SiC-coated graphite members shown in Figure 7(a) taken along line D-D.

In the SiC-coated graphite member joint 500 of this embodiment, a pipe-shaped SiC-coated graphite member 50 with a tapered lower portion is combined with a flange-shaped SiC-coated graphite member 60 with an inclined surface formed so as to approximately fit into the tapered portion of the SiC-coated graphite member 50, and the two are joined together by forming an outer CVD-SiC layer.

A convex portion 53 that serves as one end is formed on the central axis side of the tapered portion of the pipe-shaped SiC-coated graphite member 50, and a concave portion 54 that serves as the other end is formed on the outer periphery side.
Also, on the inclined surface of the flange-shaped SiC-coated graphite member 60, a convex portion 63 which becomes one end is formed on the central axis side, and a concave portion 64 which becomes the other end is formed on the outer periphery side. These tops are flattened by a method such as co-grinding.

The SiC-coated graphite member 50 and the SiC-coated graphite member 60 are assembled so that the protrusions 53 and 63 of the SiC-coated graphite member 50 and 60 are in contact with each other, and an outer CVD-SiC layer 58 is formed on the outside of the protrusions 53 and 63 and on the entire inside of the recesses 54 and 64, and the SiC-coated graphite member 50 and the SiC-coated graphite member 60 are joined to form a joint body 500 of SiC-coated graphite members.

FIG. 8( a ) is a polarizing microscope photograph showing a cross section of a joined body of SiC-coated graphite members of the present invention, and FIG. 8( b ) is a cross-sectional view showing a schematic configuration of the joined body of SiC-coated graphite members shown in FIG. 8( a ).
According to FIG. 8( b ), SiC-coated graphite members 70 each having an inner CVD-SiC layer 76 formed on the surface of a base material 71 are combined at their mating surfaces, and an outer CVD-SiC layer 78 is formed in the recess 74, with the two SiC-coated graphite members 70 being joined together by this outer CVD-SiC layer 78.
When forming the outer CVD-SiC layer 78 on the SiC-coated graphite member 70, a source gas is supplied to the recess 74 from the right side (outside) of the drawing, but since the source gas concentration usually decreases the deeper into the recess 74, depending on the source gas conditions, after the second bonding portion 78b is formed in the surface layer, no bonding portion is formed in the recess 74, and a cavity may result. However, the second bonding portion 78b and the first bonding portion, not shown in the photograph, are formed on the convex side, resulting in a bonded body of SiC-coated graphite members that has high bonding strength and is airtight.

9(a) to (d) are cross-sectional views showing examples of combinations of SiC-coated graphite members other than the combinations of SiC-coated graphite members shown in FIGS. 1 to 7 when manufacturing a joint of SiC-coated graphite members.
9(a) to (d), d1 indicates the distance between the substrates at the convex portions when the SiC-coated graphite members are assembled, and d2 indicates the longest distance between the substrates at the concave portions. A short d1 means that the thickness of the sandwiched inner CVD-SiC layer is thin. In addition, (d2-d1) is the difference in distance between the ends on the convex portion side and the ends on the other end side (concave portion side) on the assembled surface.

Figure 9(a) shows an example of a combination in which substrates 81 (SiC-coated graphite members 80) of the same shape with convex and concave portions are combined. In this example of combination, the distance d2 is large, and a concave portion with a large capacity is formed, making it easy to form an outer CVD-SiC layer inside the concave portion.

Figure 9(b) shows an example of a combination of a substrate 81 (SiC-coated graphite member 80) with convex and concave portions formed thereon and a substrate 91 (SiC-coated graphite member 90) whose mating surface is flat. The distance d2 is about half that of the combination example shown in Figure 9(a), and while it is easy to form an outer CVD-SiC layer that covers the concave portions, it is easy to form a second outer CVD-SiC layer only at the entrance to the concave portions. In addition, substrate 91, whose mating surface is flat, is easy to process because of its simple shape.

Figure 9 (c) shows an example of a combination of a substrate 81 (SiC-coated graphite member 80) having a convex portion and a substrate 101 (SiC-coated graphite member 100) having a slightly different shape but also having a convex portion. However, the convex portion of one SiC-coated graphite member is combined with the lower surface of the other SiC-coated graphite member where no convex portion is formed, and since the volume of the concave portion is small and the distance d2 between the two members is closer, when the outer CVD-SiC layer is formed, a second joint can be easily formed in the concave portion, but a cavity is likely to be formed. Also, in this combination example, since the shapes are fitted together, there is little misalignment in the setting when the outer CVD-SiC layer is formed, making it easy to handle during manufacturing.

Figure 9(d) shows an example of a combination of a substrate 111 (SiC-coated graphite member 110) with a recess having an inclined surface that gradually becomes lower from the top of the protrusion, and a substrate 91 (SiC-coated graphite member 90) with a flat mating surface. Since the cross-sectional area of the recess is gradually reduced, the source gas can easily penetrate deep into the recess, and an outer CVD-SiC layer can easily be formed over the entire recess.

As shown in Figures 9(a) to (d), two SiC-coated graphite members are combined and an outer CVD-SiC layer is formed to form a bonded SiC-coated graphite member of the present invention.

10, 31, 41, 51, 61, 71, 81, 91, 101, 111 Base material 10a Bottom surface 12, 22 Wall portion 13, 23, 33, 43, 53, 63 Convex portion 13a, 23a, 33a Top portion 14, 24, 34, 44, 54, 64, 74 Concave portion 15, 25 Groove portion 20, 30, 40, 50, 60, 70 SiC-coated graphite member 80, 90, 100, 110 SiC-coated graphite member 27 CVD-SiC layer 26, 36, 46, 56, 76 Inner CVD-SiC layer 28, 38, 48, 58, 78 Outer CVD-SiC layer 28a, 38a, 48a, 58a First joint 28b, 38b, 48b, 58b, 78b Second joint 39, 49 Cavity 200, 300, 400, 500, 700 Joint of SiC-coated graphite members 330a Flattened top

Claims (4)

A joint of SiC-coated graphite members, in which a CVD-SiC layer covers a surface of a substrate made of graphite, and a plurality of the substrates are joined by the CVD-SiC layer via a combination surface,
The combination surface of the at least one base material has a convex portion on one end side of the combination surface that is higher than the surrounding area, and a concave portion on the other end side that opens to the outside of the combination surface when combined with another base material,
The CVD - SiC layer is
a first bonding portion that bonds the base material along an outer surface of the bonded body outside the convex portion of the mating surface;
a second joining portion that penetrates the recess of the mating surface outside the recess and joins the opposing surfaces of the substrates ;
A joined body of SiC-coated graphite members, characterized in that the tops of the protrusions are on the same plane, and the ratio of the area of the tops of the protrusions to the area of the joining surfaces is 5 to 60% . A joint of SiC-coated graphite members as described in claim 1, characterized in that the surfaces of the substrates made of both graphites have a CVD-SiC layer at the joining surface. The bonded body of SiC-coated graphite members described in claim 2, characterized in that the CVD-SiC layer formed on the top of the convex portion is a polished surface. The joined body of SiC-coated graphite members as described in claim 3, characterized in that the surface of the CVD-SiC layer formed on the top of the convex portion is on the same plane as the surface of the CVD-SiC layer formed on the surface of the other substrate.

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