JP7580926B2 - Method for manufacturing a joint of SiC-coated graphite members - Google Patents

Description

The present invention relates to a method for manufacturing a bonded SiC-coated graphite member that combines a composite material having a CVD-SiC layer on the surface of a graphite substrate.

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 wear 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 a composite material, 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 parts where they fit together are filled with CVD deposits and are bonded together, so that there is no 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.
On the other hand, when a thin CVD-SiC layer is used, the gaps cannot be filled sufficiently, resulting in a trade-off that reduces airtightness. Therefore, it is difficult to manufacture a bonded body of SiC-coated graphite material that simultaneously satisfies the bonding strength, dimensional accuracy, and airtightness requirements.

In view of the above problems, the present invention aims to provide a method for manufacturing 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, the present invention provides a method for producing a joined body of SiC-coated graphite members, the CVD-SiC layer comprising a first CVD-SiC layer covering a surface of a substrate made of graphite, and a second CVD-SiC layer joining a plurality of the substrates, the method comprising the steps of:
The joined body includes a combining step of combining a plurality of SiC-coated graphite members each having a first CVD-SiC layer on a combining surface, and a joining step of covering the combined plurality of SiC-coated graphite members with a second CVD-SiC layer from the outside, wherein at least one of the SiC-coated graphite members has a convex portion higher than the surrounding area on one end side of the combining surface, and a concave portion on the other end side that opens to the outside by being combined with another SiC-coated graphite member, and the second CVD-SiC layer has a first joining portion that joins the plurality of SiC-coated graphite members along the outer surface of the joined body outside the convex portion of the combining surface, and a second joining portion that penetrates into the concave portion of the combining surface from the outside and joins opposing surfaces of the SiC-coated graphite members to each other.
The above-mentioned combination surfaces include the surfaces where the SiC-coated graphite members come into contact when they are combined, and refer to the surfaces where the two members face each other, and include convex portions and concave portions.

According to the method for manufacturing a joint of SiC-coated graphite members of the present invention, at least one of the SiC-coated graphite members has a convex portion higher than the surroundings on one end side of the combining surface, and has a joining portion (second CVD-SiC layer) that joins the multiple SiC-coated graphite members along the outer surface of the joined body outside the convex portion of the combining surface. Therefore, gaps are unlikely to form in the portion where the convex portions of the combining surfaces contact, and the second CVD-SiC layer joins the base materials along the outer surface of the joined body on the outside, so that a thin, highly airtight CVD-SiC layer is obtained on one end side of the combining surfaces.
In addition, the other end side has a second joining portion (second CVD-SiC layer) that penetrates into the recess from the outside of the recess that opens to the outside and joins the opposing surfaces of the SiC-coated graphite members by combining it with another SiC-coated member, so that the joining portion can be firmly bonded and a strong bond can be obtained.

In other words, according to the manufacturing method of the present invention for a joint of SiC-coated graphite members, a second CVD-SiC layer, which is a thin CVD-SiC layer but has the role of maintaining airtightness at one end and ensuring bonding strength at the other end, can be formed on a combination of SiC-coated graphite members having a first CVD-SiC layer, and a joint of SiC-coated graphite members having high bonding strength and airtightness can be obtained.

In the manufacturing method of the present invention for joining SiC-coated graphite members, it is desirable to have a first CVD-SiC layer on the surfaces of both graphite substrates at the above-mentioned joining surface.

In the resulting bonded body of SiC-coated graphite members, the second CVD-SiC coating layer is formed in the recess formed in the SiC-coated graphite member on the other end side, with the coating layer being thicker toward the inlet side and thinner toward the inside. Therefore, if the first CVD-SiC layer is not formed on the surfaces of both graphite substrates, exposed graphite is likely to be formed. However, in the manufacturing method of the bonded body of SiC-coated graphite members of the present invention, if the first CVD-SiC layer is formed on the surfaces of both graphite substrates at the above-mentioned combined surfaces, the coating layer made of the first CVD-SiC layer is formed around the substrates before they are combined, eliminating the exposed graphite and forming a second bonding portion (second CVD-SiC layer) that penetrates into the recess and bonds the opposing surfaces of the SiC-coated graphite members.

In the method for producing a bonded body of SiC-coated graphite members of the present invention, it is preferable that the first CVD-SiC layer on the surface of the top of the protrusion is a polished surface.
When a CVD-SiC layer is formed on a substrate, the surface is rough and difficult to process, so unless a polished surface is formed on the CVD-SiC layer on the surface of the top of the convex portion, it is difficult to obtain a highly airtight joint even when the convex portion is pressed against another mating surface.
However, in the method for manufacturing a joined SiC-coated graphite member of the present invention, if the first CVD-SiC layer on the surface of the top of the convex portion is a polished surface, a highly accurate, flat top can be easily obtained, and the top of the convex portion can easily adhere to other SiC-coated graphite members with which it comes into contact, making it easy to obtain a highly airtight SiC-coated graphite member.

In the method for producing a joined body of SiC-coated graphite members of the present invention, it is preferable that the tops of the protrusions are on the same plane.
In the method for manufacturing a joint of SiC-coated graphite members of the present invention, when the tops of the protrusions are on the same plane, the tops of the mating surfaces become one plane. Therefore, processing after film formation can be handled by simply flattening, and the parts where the protrusions are formed become highly accurate mating surfaces without gaps through simple processing. Therefore, a SiC-coated graphite member with high airtightness can be obtained.

In the method for manufacturing a 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 materials on the convex portion side and the ends on the other side at the joining surfaces be 40 to 100 μm.
In the method for producing a joined body of SiC-coated graphite members of the present invention, when the difference in distance between the ends of the base materials on the convex side and the ends of the base materials 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 can be 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.

According to the manufacturing method of the present invention for manufacturing a joint of SiC-coated graphite members, a second CVD-SiC layer, which is a thin CVD-SiC layer but has the role of maintaining airtightness at one end and ensuring bonding strength at the other end, can be formed on a combination of SiC-coated graphite members having a first CVD-SiC layer, and a joint of SiC-coated graphite members having high bonding strength and airtightness can be obtained.

FIG. 1( a ) is a perspective view showing an example of a substrate for producing 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 first CVD-SiC layer is formed. FIG. 3 is a cross-sectional view that shows a schematic view of a state in which two SiC-coated graphite members on which a first CVD-SiC layer is formed are combined together. FIG. 4(a) is a perspective view showing a schematic diagram of a joined body of SiC-coated graphite members having a second CVD-SiC layer formed thereon, and FIG. 4(b) is a cross-sectional view taken along line B-B of the joined body of SiC-coated graphite members shown in FIG. 4(a). 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 manufacturing method of the bonded body of SiC-coated graphite members of the present invention will be described in detail below with respect to each embodiment. However, the present invention is not limited to the following embodiments, and can be modified as appropriate within the scope of the present invention.

The method for producing a joined body of SiC-coated graphite members of the present invention is a method for producing a joined body of SiC-coated graphite members, the CVD-SiC layer comprising a first CVD-SiC layer covering a surface of a substrate made of graphite, and a second CVD-SiC layer joining a plurality of the substrates,
The method includes a combining step of combining a plurality of SiC-coated graphite members each having a first CVD-SiC layer on a combining surface, and a joining step of covering the combined plurality of SiC-coated graphite members with a second CVD-SiC layer from the outside, wherein at least one of the SiC-coated graphite members has a convex portion higher than the surrounding area on one end side of the combining surface, and a concave portion on the other end side that opens to the outside by being combined with another SiC-coated graphite member, and the second CVD-SiC layer has a first joining portion that joins the plurality of SiC-coated graphite members along the outer surface of the joined body outside the convex portion of the combining surface, and a second joining portion that penetrates into the concave portion of the combining surface from the outside and joins opposing surfaces of the SiC-coated graphite members.

The manufacturing method of the present invention for manufacturing a joint of SiC-coated graphite members includes an assembly process in which multiple SiC-coated graphite members each having a first CVD-SiC layer on the joining surface are assembled, and a joining process in which the assembled multiple SiC-coated graphite members are further covered from the outside with a second CVD-SiC layer.

In the manufacturing method of the present invention for a bonded body of SiC-coated graphite members, a first CVD-SiC layer formation process is first carried out before the assembly process, in which a first CVD-SiC layer is formed so as to cover the surface of the graphite member, which is the base material.

The type of graphite that constitutes the 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 the substrate 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 first CVD-SiC layer is easily impregnated into the open pores, and the first 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 an appropriate amount of open pores, the first CVD-SiC layer is easily filled into the open pores, and the coating layer made of the first 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.

In the manufacturing method of the present invention for a bonded body of SiC-coated graphite members, a first CVD-SiC layer is formed with a substantially uniform thickness on the surface of the substrate, but the basic shape of the SiC-coated graphite member on which the first CVD-SiC layer is formed is the same as the shape of the substrate. Therefore, the parts of the substrate that correspond to the SiC-coated graphite member (protrusions, recesses, etc.) are given the same names as the components that make up the SiC-coated graphite member.

The shape of the substrate is not particularly limited, but at least one of the substrates (hereinafter referred to as the first 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.

The manufacturing method of the present invention for manufacturing a bonded body of SiC-coated graphite members will be explained below using the substrates shown in Figures 1(a) and (b) as examples, but later, other substrates (SiC-coated graphite members) will also be explained using the bonded body of SiC-coated graphite members as examples.

FIG. 1( a ) is a perspective view showing an example of a substrate for producing 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.
The substrate 10 is a substrate for manufacturing a joint of tubular SiC-coated graphite members having a through hole for passing a fluid therethrough, and has a groove 15 formed in the center as a through hole, and walls 12 for forming a mating surface formed on both sides of the groove. The walls 12 on both sides are composed of a protrusion 13 and a recess 14, and the top 13a of the protrusion 13 is flat. The protrusion 13 and the recess 14 are stepped, and the protrusion 13 is formed one step higher than the recess 14.
In the manufacturing method of a joined body of SiC-coated graphite members described below, since it is difficult to see the state of the coating from a perspective view, the method will be described based only on the cross-sectional view of line A-A described above.

(First CVD-SiC layer formation process)
A first CVD-SiC layer is formed on the surface of the substrate having the above-mentioned shape.
The method for forming the first CVD-SiC layer by the CVD method is not particularly limited, and examples thereof include thermal CVD, plasma organic CVD, photo CVD, low pressure CVD, metal organic CVD, and CVI (chemical vapor impregnation).

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 a first 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 first CVD-SiC layer can penetrate into the open pores of the substrate as well, forming a CVD-SiC layer that is not easily peeled off.

The thickness of the first CVD-SiC layer to be formed is preferably 20 to 100 μm.
The first CVD-SiC layer may be formed on the entire surface of a substrate made of graphite, or may be formed on the other surfaces except for the bottom surface 10a that is in contact with the support by being placed on the support of the CVD apparatus.

FIG. 2 is a cross-sectional view that typically shows a SiC-coated graphite member on which a first CVD-SiC layer is formed.
2, a first CVD-SiC layer 26 is formed with a substantially uniform thickness over the entire surface, including the bottom surface 10a, of the substrate 10. That is, this SiC-coated graphite member 20 also has a groove 25 serving as a through hole in the center, and walls 22 for forming a combination surface are formed on both sides of the groove 25. The walls 22 on both sides have a protrusion 23 that is higher than the surrounding area on one end side, and a recess 24 that opens to the outside by being combined with another SiC-coated graphite member on the other end side.

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

(Combination process)
In the combining step, a plurality of SiC-coated graphite members having a first CVD-SiC layer on a combining surface are combined.
FIG. 3 is a cross-sectional view that shows a schematic view of two SiC-coated graphite members each having a base material and a first CVD-SiC layer formed on the surface thereof, which are combined together.
3, two SiC-coated graphite members 20 are combined such 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. The protrusions 23 and the recesses 24 form a second CVD-SiC layer and play an important role in joining the two SiC-coated graphite members.

In FIG. 3, two SiC-coated graphite members 20 (substrates 10) of exactly the same shape and configuration are combined, but as described above, the other SiC-coated graphite member may have a surface that can abut against the convex portion of one SiC-coated graphite member, and the shapes of the other SiC-coated graphite member may be different as long as the combination of the two members forms a concave portion that is open to the outside.
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 SiC-coated graphite members are joined by combining multiple SiC-coated graphite members and then forming a second CVD-SiC layer.

(Joining process)
In the bonding process, the periphery of the assembled multiple SiC-coated graphite members is covered with a second CVD-SiC layer.

Figure 4(a) is a perspective view showing a schematic diagram of a bonded body of SiC-coated graphite members in which a second CVD-SiC layer is formed on the surface of a substrate, and Figure 4(b) is a cross-sectional view of the bonded body of SiC-coated graphite members shown in Figure 4(a) along line B-B.

As shown in Figures 4(a) and (b), in the joined body 200 of SiC-coated graphite members, two SiC-coated graphite members 20 each having a first CVD-SiC layer 26 are combined, and the entire outer surfaces and internal recesses of the two combined SiC-coated graphite members 20 are covered with a second CVD-SiC layer 28, thereby forming the joined body 200 of SiC-coated graphite members.

That is, in this joined body 200 of SiC-coated graphite members, the second CVD-SiC layer 28 has a first joining portion 28a that joins the two SiC-coated graphite members 20 outside the convex portion 23 of the combining surface along the outer surface of the joined body, and has a second joining portion 28b that penetrates into the concave portion 24 of the combining surface from outside and joins the opposing surfaces of the SiC-coated graphite members to each other. Therefore, a joined body of SiC-coated graphite members having high joining strength and airtightness can be obtained.
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 method for forming the second CVD-SiC layer is similar to the method for forming the first 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-based gas such as methyltrichlorosilane around the SiC-coated graphite member or spraying it onto the SiC-coated graphite member to form the second CVD-SiC layer on the surface of the SiC-coated graphite member.
The thickness of the second CVD-SiC layer to be formed is preferably 20 to 100 μm.

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.
In Figure 5 (a), it is intended to combine two identically shaped SiC-coated graphite members 30 each having a first CVD-SiC layer 36 formed thereon. However, the surface of the tops 33a of the convex portions 33 of the first 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 a second 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 a second CVD-SiC layer 38 is formed as shown in FIG. 5(d). By forming the second CVD-SiC layer 38 in this manner, a joint 300 of SiC-coated graphite members can be formed.

In this embodiment, the second CVD-SiC layer 38 is not formed throughout 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 outside convex portion 33, and a second bonding portion 38b is formed in region B, penetrating into concave portion 34 and bonding the two SiC-coated graphite members together, resulting in a bonded body 300 of SiC-coated graphite members in which two SiC-coated graphite members are firmly bonded together, which also has excellent airtightness.

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 first 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 their flattened tops abut against each other, and a second CVD-SiC layer 48 is formed on the inside and outer periphery of the cylinder.
In this embodiment, the second CVD-SiC layer 48 is not formed throughout 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 outside the convex portion 43, and a second bonding portion 48b is formed in region B, penetrating into the concave portion 44 and bonding the two SiC-coated graphite members together, 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 having a tapered lower portion is combined with a flange-shaped SiC-coated graphite member 60 having 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 a second CVD-SiC layer.
The SiC-coated graphite member 50 has a substrate 51 coated with a first CVD-SiC layer 56 , and the SiC-coated graphite member 60 has a substrate 61 coated with a first CVD-SiC layer 66 .

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 a second CVD-SiC layer 58 is formed on the outside of the protrusions 53 and 63 and on the entire inside of the recess formed by 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 a first CVD-SiC layer 76 formed on the surface of a base material 71 are combined at their combining surfaces, a second CVD-SiC layer 78 is formed in the recess 74, and the two SiC-coated graphite members 70 are joined together by this second CVD-SiC layer 78.
When forming the second CVD-SiC layer 78 on the SiC-coated graphite member 70, the source gas is supplied to the recess 74 from the right side (outside) of the drawing, but since the concentration of the source gas 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 portion, no bonding portion is formed in the recess 74, leaving a cavity. However, the first bonding portion is formed on the convex side of the second bonding portion 78b and the photograph, resulting in a bonded body of SiC-coated graphite members that has high bonding strength and airtightness.

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 first CVD-SiC layer sandwiched between the substrates 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 surfaces.

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 a second 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) with a flat mating surface. The distance d2 is about half that of the combination example shown in Figure 9(a), and while it is easy to form a second CVD-SiC layer that covers the concave portions, it is easy to form a second CVD-SiC layer only at the entrance to the concave portions. In addition, substrate 91, which has a flat mating surface, 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 convex portion of a slightly different shape, but in which the convex portion of one SiC-coated graphite member is combined with a lower surface of the other SiC-coated graphite member on which no convex portion is formed. Since the volume of the concave portion is small and the distance d2 between the two members is closer, when the second CVD-SiC layer is formed, a second joint can be easily formed in the concave portion, but a cavity is likely to be formed. In addition, in this combination example, since the shapes are fitted together, there is little misalignment in the setting when the second CVD-SiC layer is formed, and handling during manufacturing is easy.

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 the second CVD-SiC layer can easily be formed over the entire recess.

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 26, 36, 46, 56, 66 First CVD-SiC layer 28, 38, 48, 58, 78 Second CVD-SiC layer 28a, 38a, 48a, 58a First bonding portion 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 method for producing a joined body of SiC-coated graphite members, the CVD-SiC layer comprising a first CVD-SiC layer covering a surface of a substrate made of graphite, and a second CVD-SiC layer joining a plurality of the substrates, comprising:
a combining step of combining a plurality of SiC-coated graphite members each having a first CVD-SiC layer on a combining surface;
and a bonding step of covering the combined SiC-coated graphite members from the outside with a second CVD-SiC layer;
a combination surface of at least one of the SiC-coated graphite members includes 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 by being combined with another SiC-coated graphite member;
The second CVD - SiC layer is
a first bonding portion that bonds the plurality of SiC-coated graphite members along an outer surface of the bonded body outside the convex portion of the combination surface;
a second joining portion that penetrates into the recess from the outside of the recess of the mating surface and joins the opposing surfaces of the SiC-coated graphite members;
having
a top of each of the protrusions being on the same plane, and a ratio of an area of the top of each of the protrusions to an area of the joining surfaces being 5 to 60% . The method for manufacturing a joint of SiC-coated graphite members according to claim 1, characterized in that at the joining surface, a first CVD-SiC layer is formed on the surface of both graphite substrates. The method for manufacturing a joint of SiC-coated graphite members described in claim 2, characterized in that the first CVD-SiC layer on the surface of the top of the protrusion is a polished surface. The method for manufacturing a joint of SiC-coated graphite members according to claim 3, characterized in that the tops of the protrusions are on the same plane.

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