JP5198171B2 - Method for manufacturing silicon carbide joined body - Google Patents

Description

The present invention relates to a silicon carbide bonded body and a method for manufacturing the same. In particular, the present invention relates to a joined body suitable for a member that requires airtightness and high adhesion at a joint. For example, the present invention can be applied to a liquid recovery unit in an immersion exposure apparatus and a shower plate that is a gas supply unit such as a CVD apparatus.

Silicon carbide is excellent in heat resistance and corrosion resistance, and is often used as a member for semiconductor manufacturing equipment, but silicon carbide has a high sintering temperature and the atmosphere is also under an inert gas. There is a limit in size to form. Therefore, various joining techniques have been proposed.

For example, Patent Document 1 discloses that an air-pressure-sintered SiC sintered body having a bulk density of 2.8 g / cm ³ or more is joined to Si, and open pores that open to the joint surface of the normal-pressure sintered SiC sintered body. And a technique for joining via a filling part made of Si integral with the joint part, in which granular Si having a particle size of 0.05 mm is mixed with ethanol to form a paste, An example in which 02 mm plate-like Si is interposed between SiC sintered bodies and joined is shown.

Further, Patent Document 2 discloses a technique of coating a metal on the surface of carbide ceramics and metalizing, and joining the carbide ceramics to each other. As an example, a thickness of 500 μm is provided between silicon carbide sintered bodies. It is shown that a 10 × 10 mm square Si wafer was sandwiched and heated at 1600 ° C. and 4 × 10 torr for 20 minutes to be bonded.

JP 2002-145679 A JP-A-60-161384

However, as disclosed in these documents, it is difficult to make the filling rate of the metal silicon powder constant, and it is difficult to control the positional deviation after the bonding in the method of filling and bonding the metal silicon powder. there were. In addition, there is a problem that voids are likely to be generated in the bonding layer when the metal silicon powder is melted, thereby reducing the bonding strength and airtightness. In addition, in order to prevent voids, when a large amount of bonding material is used, the amount of seepage from the bonded portion increases. For example, in the case of a bonded body having a hollow portion, the shape accuracy of the hollow portion cannot be obtained and is blocked. There was a problem.

Although an example in which metal silicon of a plate material is used as a bonding material is given, shape accuracy such as thickness and parallelism of the plate material is strictly required when sandwiching the plate material. Furthermore, since the shape of the plate cannot match the shape of the joint, there is inevitably a gap between the members in the state before melting, so that the joint strength and airtightness are the same as in the powder filling method. There was a possibility that it could not be obtained.

In addition, since the amount of metallic silicon that melts and oozes out cannot be controlled, there is a problem that in joining of members having fine and complicated shapes, shape accuracy cannot be obtained due to oozing, and grooves and holes are buried. It was happening. In particular, in an immersion exposure apparatus, a CVD apparatus, or the like, there are members having a shape that is difficult to be integrally formed such that a fine groove or hole for supplying or recovering liquid or gas is formed and a hollow portion is formed. In order to form such a fine structure, the positional relationship between the members to be joined must be precisely adjusted, so that the shape defect after joining has been a big problem.

The present invention has been made in view of these problems, and has a small positional deviation after joining, a high joining strength and airtightness, and a joined body excellent in shape accuracy of the hollow part even when it has a hollow part. The manufacturing method of the silicon carbide joined body from which is obtained is provided.

In order to solve these problems, the present invention is a silicon carbide joined body in which a first silicon carbide sintered body and a second silicon carbide sintered body are joined via a joining layer made of metallic silicon. The first silicon carbide sintered body has a bonding surface on which a metal silicon layer is formed, and the second silicon carbide sintered body has a bonding surface in contact with the metal silicon layer, Each bonding surface of the first and second silicon carbide sintered bodies has a surface roughness Ra of 0.6 μm or less, and is bonded through a bonding layer formed by heat-treating the metal silicon layer. A silicon carbide joined body is provided.

In the present invention, the bonding surface of the silicon carbide sintered body is processed to have a surface roughness Ra of 0.6 μm or less. Usually, an oxide film is formed on the surface of the silicon carbide sintered body, and as it is, the wettability with metal silicon is insufficient, so that reduction treatment is performed with carbon or the like. However, in the present invention, joining is possible without such reduction treatment. By setting Ra within the above range, wettability is exhibited to the extent that sufficient bonding strength is obtained, and bonding is achieved.

Moreover, in joining such sintered bodies, it is common to perform a process of roughening the joining surface by blasting or the like. This is to increase the bonding strength by causing an anchor effect between the bonding surface and the bonding material. However, in the present invention, the surface roughness is reduced. The reason for this is that a protective film is formed on the surface of the silicon carbide sintered body by oxidation to reduce the wettability with metallic silicon. This is because the influence of the protective oxide film formed on the surface of the bonded body can be extremely reduced.

In Patent Documents 1 and 2, metal silicon is used as a bonding material, but the present invention differs from these techniques in that a metal is bonded to the bonding surface of one silicon carbide sintered body before the sintered bodies are bonded to each other. A silicon layer is formed. As described in Patent Documents 1 and 2, if the silicon carbide sintered bodies are to be joined simultaneously with the melting of the metal silicon powder or the metal silicon plate, the positional deviation when the metal silicon powder or the like is melted is significant. Later shape is likely to be out of order. On the other hand, in the present invention, since the metal silicon layer is formed in advance, the misalignment can be suppressed to a small extent even after remelting.

In addition, by adjusting Ra within the above range and forming the metal silicon layer in advance, it is possible to minimize seepage during bonding, so that positional displacement can be prevented and there is a hollow portion near the bonding layer. Even in some cases, problems such as blockage can be prevented.

In this way, seepage and misalignment can be suppressed by reducing the surface roughness and increasing the contact between the metal silicon layer and the silicon carbide sintered body, thereby reducing the volatilization of metal silicon by heat treatment in vacuum. It seems that it can be suppressed. Such an effect seems to be obtained even if the metal silicon plate is used for bonding without forming the metal silicon layer, but there is little contact between the metal silicon plate and the silicon carbide sintered body and the open part. If it is large, the volatilization of the metal silicon increases, so that bleeding and positional deviation are likely to occur, and voids are also likely to occur. As in the present invention, volatilization can be suppressed by once forming a metal silicon layer.

The metal silicon layer can be formed by a normal film forming method such as CVD, PVD, or thermal spraying. Further, a metal powder or a metal plate may be melted. Furthermore, it is preferable to adjust the thickness by grinding the metal silicon layer. By grinding, the surface of the metal silicon layer is ground to remove the layer that hinders the melting of the oxide film, the carbide film, etc., so that melting occurs smoothly. More preferably, the surface roughness of the metal silicon layer is also set to 0.6 μm or less. Since contact with the joint surface of the second silicon carbide sintered body increases, volatilization of metal silicon can be suppressed, and joint strength and airtightness can be improved.

Moreover, it is desirable that the metal silicon layer has a relative density of 90% or more. This is because if the relative density is small, the bonding layer tends to contain bubbles and the bonding strength is lowered. It has been found that when the relative density is low, there is a large amount of seepage during heat treatment. This seems to be because wettability changes remarkably by including bubbles inside.

The bonding layer of the silicon carbide bonded body preferably has a thickness of 30 to 150 μm. In addition to the above surface roughness and relative density, a bonded body having excellent bonding strength can be obtained by adjusting the thickness of the bonding layer to such a range.

Further, the silicon carbide joined body of the present invention has a four-point bending strength of 250 MPa or more in accordance with JIS R1624. As described above, such a silicon carbide bonded body can be obtained by adjusting the formation of the metal silicon layer, the surface roughness of the bonding surface, the relative density, and the bonding layer thickness.

The present invention also includes a step of processing each bonding surface of the first and second silicon carbide sintered bodies to a surface roughness Ra of 0.6 μm or less, and a relative density on the bonding surface of the first silicon carbide sintered body. The step of forming a metal silicon layer having a thickness of 90% or more and a thickness of 50 to 200 μm , the bonding surface of the second silicon carbide sintered body and the metal silicon layer are brought into contact with each other , and are heated at 1410 to 1500 ° C. in vacuum. And a step of heat-treating at a temperature within a range .

As described above, by reducing the surface roughness of each joint surface of the silicon carbide sintered body, deterioration of the wettability of the metal silicon by the oxidation protective film on the surface of the silicon carbide sintered body is suppressed, Since the number of open portions to the atmosphere can be reduced, volatilization during heat treatment can be prevented, and a bonded body with high bonding strength and airtightness can be obtained.

Metal silicon layer has a thickness of 50 to 200 [mu] m. With such a range, it is possible to obtain a bonding strength and airtight assembly, also, it is possible to reduce the occurrence of voids and exudation.

In the present invention, the thickness of the bonding layer formed between the bonding surfaces of the silicon carbide sintered body after the heat treatment is 50 to 80% of the metal silicon layer. By adjusting the surface roughness of the sintered body and the relative density of the metal silicon layer, voids in the bonding layer can be eliminated and bleeding can be suppressed, so that dimensional changes before and after bonding can be reduced. Moreover, even if it is a joined body which has a hollow structure, obstruction | occlusion by the oozing to a hollow part does not arise, Therefore Even if it is a hollow part which is difficult to process after joining, the outstanding shape precision can be achieved.

Provided is a method for joining silicon carbide sintered bodies in which a positional deviation after joining is small, joining strength and airtightness are high, and a joined body having a hollow portion having excellent shape accuracy can be obtained even when the hollow portion is provided. it can.

Hereinafter, the silicon carbide sintered body joining method of the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic view showing a joining method of the present invention.

FIG. 1 (A) shows the first silicon carbide sintered body 11 and the second silicon carbide sintered body 12 and their joint surfaces 11a and 12a.

Silicon carbide sintered bodies 11 and 12 can be produced by a molding method such as press molding, CIP molding, and cast molding, and a sintering method such as atmospheric pressure sintering, pressure sintering, and reaction sintering. The surface roughness of the joint surfaces 11a and 12a can be adjusted by grinding with a surface grinder, machining center or the like, and further by lapping or the like.

FIG. 1B shows a state in which the metal silicon layer 13 is formed on the joint surface 11 a of the first silicon carbide sintered body 11. As described above, the metal silicon layer may be formed by melting metal powder or a metal plate in addition to normal film formation such as sputtering, CVD, PVD, and thermal spraying.

As a method for adjusting the relative density of the metal silicon layer, the sputtering method uses metal silicon as a target, and controls the ionization voltage of the rare gas and the distance between the targets on the bonding surface to form a film, thereby depositing a relative density of 90% or more. A film can be formed. In the CVD method, the temperature control of the bonding surface serving as the target substrate, the concentration and flow rate of the gas phase gas, and the like are appropriately adjusted according to the size of the bonding surface. The melting method can be adjusted by the degree of vacuum during heating. A metal silicon layer having a relative density of 90% or more can be obtained with a degree of vacuum of about 100 kPa. The heat treatment temperature is preferably 1410 to 1500 ° C. at which metal silicon melts, and the heat treatment time is preferably 10 to 60 minutes.

As a method for adjusting the thickness of the metal silicon layer, in the sputtering method and the CVD method, the thickness is controlled by time from the film formation rate. In the melting method, when metal silicon powder is used, it can be controlled by calculating the thickness after melting from the powder filling rate.

The metal silicon layer may be processed as necessary to adjust the shape such as thickness. By processing in this way, airtight bonding with sufficient strength with the other silicon carbide sintered body becomes possible. By setting the thickness of the metal silicon layer to 50 to 200 μm, it is possible to reliably bond without causing a gap in a part of the position due to the positional deviation. In addition, since the bleeding of the bonding material can be suppressed, it is possible to prevent inconveniences such as inaccuracy and blockage of fine holes, and it is possible to obtain a bonded body having excellent hollow portion shape accuracy even when it has a hollow portion. it can.

The purity of the metal silicon is preferably 97% or more, more preferably 99% or more, and still more preferably 99.9% or more. This is because when there are many impurities, the melting temperature is lowered, and problems such as seepage occur.

Next, the bonding surface 12a of the second silicon carbide sintered body 12 is brought into contact with the metal silicon layer 13 and is heated and bonded. Since the metal silicon layer 13 is formed on the first silicon carbide sintered body 11, for example, even when joining with a curved surface as shown in FIG. 2, a joined body can be obtained without any problems. When a metal silicon powder or a metal silicon plate is used as the bonding material, when melted, the metal silicon flows out along the curved surface or a liquid pool is generated, which may cause a bonding failure such as a gap. On the other hand, in the present invention, metallic silicon is difficult to bleed out and can be joined without voids.

As in the metal silicon layer forming step, the heating in the bonding step is preferably in vacuum, the heat treatment temperature is preferably 1410 to 1500 ° C. at which the metal silicon melts, and the heat treatment time is preferably 30 to 60 minutes. Moreover, it is desirable to apply a load of 4 to ²⁰ g / cm ² at the time of joining. When a load larger than this is applied, silicon carbide is generated at the joint and the joint strength is likely to be lowered, which is not preferable.

FIG. 1C shows a joined body obtained by the joining method of the present invention. The thickness of the bonding layer 14 formed between the bonding surfaces is 50 to 80% of the metal silicon layer. By adjusting the surface roughness of the sintered body and the relative density of the metal silicon layer, voids in the bonding layer can be eliminated and bleeding can be suppressed, so that dimensional changes before and after bonding can be reduced.

Hereinafter, the present invention will be described with reference to test examples of bonding strength and airtightness.

The silicon carbide sintered body was formed by a CIP method using a commercially available silicon carbide powder (UF-10 manufactured by Stark) and fired at 2100 ° C. in argon. A silicon carbide sintered body (silicon carbide sintered body 31: φ50 mm, thickness 25 mm, counterbore 31b: φ5, depth 2 mm, silicon carbide sintered body 32: φ50 mm, thickness 25 mm) as shown in FIG. 3 is produced. did. These shape processings were performed by a known method such as surface grinding or a machining center to adjust the surface roughness of the joint surface.

Next, a method for forming the metal silicon layer will be described. As the CVD method, using a CVD film forming apparatus, SiCl ₄ is used as the source gas, hydrogen is used as the carrier gas, the source gas concentration is 20%, and the substrate temperature serving as the bonding surface is controlled, whereby the metal silicon layer The relative density was adjusted. The film thickness was 50 μm. As a method of melting, a silicon wafer having a purity of 99.99% and a thickness of 0.5 mm is cut to φ50 mm, provided in a through hole of φ5 mm in the center, placed on the bonding surface, and 1450 in vacuum. Heat treatment was carried out at 10 ° C. for 10 minutes. The molten metal silicon layer was subjected to a known method such as surface grinding, machining center or the like to adjust the metal silicon layer thickness.

By the above method, the bonded body was manufactured by changing the surface roughness of the bonded surface of the silicon carbide sintered body and the relative density of the metal silicon layer. For comparison, a bonded body was prepared using the metal silicon powder described above as a bonding material and a metal silicon plate (thickness 0.2 mm) without forming a metal silicon layer.

About the joining layer, the cut surface was observed with the optical microscope, and the thickness and hollow part were investigated. For the bonding strength, a test piece (3 mm × 4 mm × 40 mm) was cut out from the bonded body, and a four-point bending test (JISR1624 compliant) with a lower span of 30 mm and an upper span of 10 mm was performed to determine the bonding strength. The airtightness test was performed by a bombing method in accordance with JISZ2331. Regarding the observation of the hollow part, the joined body was cut so as to pass through the hollow part having a diameter of 5 mm and a depth of 2 mm, and the presence or absence of clogging of the hollow part with metallic silicon was visually observed. The results are shown in Table 1.

In No.1-10, 16-19, and No.21-23 which are in the scope of the present invention, the bonding strength was 253 to 284 MPa and a high value of 250 MPa or more. In No.1-10 which used CVD for metal silicon layer formation, the value of 253-284MPa and 250MPa or more was shown. In addition, No. 1 using a melting method. In 16-19 and No.21-23, the value of 274-281 MPa and 270 MPa or more was shown. In addition, the thickness of these joining layers was 32-135 micrometers, and satisfy | filled 30-150 micrometers.

On the other hand, in No.11-13 and No.20 with large surface roughness of a joining surface, a space | gap was recognized by the joining layer and the joining strength showed the low value which is less than 200 MPa. In particular, in No. 13 having a surface roughness of 1.20 μm, huge voids existed and unbonded portions were observed. Poor surface roughness of the bonding surface makes the influence of the oxide film on the silicon carbide bonding surface prominent, lowering the wettability of the metal silicon layer, and increasing the volatilization of the metal silicon. It is done.

In No. 14, where the relative density of the metal silicon layer was small, voids were observed in the bonding layer, and the bonding strength was as low as 100 MPa. This is because the bonding layer contains many bubbles because the relative density is small.

In No. 25 and 26 which joined without forming a metal silicon layer, joining strength showed the low value of 100 Mpa or less.

Regarding the airtightness and the hollow portion, in Nos. 1 to 10, and 16 to 19, and 21 to 23, which are within the scope of the present invention, the equivalent reference leak amount is from 1 × 10 ⁻⁶ Pa · m ³ / s. Small and no leakage was observed. Further, no blockage was observed in the hollow part.

On the other hand, in Nos. 11-15, 20, 25, and 26, which are outside the scope of the present invention, the equivalent reference amount is 1 × 10 ⁻⁶ Pa · m ³ / s or more, and a He leak was observed.
The cause of the leak seems to be that in Nos. 11 to 13 and 20, since the surface roughness of the bonding surface is 0.6 μm or more, the wettability with the metal silicon is poor and voids are formed in the bonding layer. . In No. 14, the relative density of the bonding layer was low, and in No. 15, the metal silicon layer was thin.

Furthermore, in No. 24-26, obstruction | occlusion of the hollow part was recognized in the hollow part observation of the cut surface of a conjugate | zygote. In No. 24, although there was no leakage by the airtight test, it seems that excess metal silicon oozes out into the hollow portion because the metal silicon layer is thick. In Nos. 25 and 26 in which the metal silicon layer is not formed, the volatilization of the metal silicon is increased, which is considered to be due to seepage, positional deviation, and voids.

Schematic which showed the joining method of this invention. Schematic which showed the example of application of the joining method of this invention. Schematic which showed the silicon carbide joined body shape of the Example.

Explanation of symbols

10; Bonded bodies 11 and 12; Silicon carbide sintered bodies 11a and 12a; Bonded surface 13; Metal silicon layer 14;

Claims (2)

A step of processing each bonding surface of the first and second silicon carbide sintered bodies to a surface roughness Ra of 0.6 μm or less;
Forming a metal silicon layer having a relative density of 90% or more and a thickness of 50 to 200 μm on the bonding surface of the first silicon carbide sintered body;
Contacting the joint surface of the second silicon carbide sintered body and the metal silicon layer, and heat-treating in vacuum at a temperature in the range of 1410 to 1500 ° C . ;
A method for producing a silicon carbide joined body comprising: 2. The method for manufacturing a silicon carbide bonded body according to claim 1 , wherein a thickness of a bonding layer formed between bonded surfaces of the silicon carbide sintered body after heat treatment is 50 to 80% of the metal silicon layer.

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