TWI588090B - Coated graphite member - Google Patents

Description

Coated graphite member

The present invention relates to a graphite member coated (coated) with pyrolytic boron nitride (PBN), pyrolytic graphite (PG), tantalum carbide (SiC), tantalum carbide (TaC), or the like.

A graphite material coated with PBN, PG, SiC, TaC or the like has characteristics which are not obtained only by graphite, and therefore is applied to various members according to the use. In particular, a graphite material coated with PBN is excellent in heat resistance, impact resistance, chemical resistance, radiation resistance, thermal conductivity, and the like, and has electrical insulation which is not obtained only by graphite. The material of the fixture or component of the carbon system is advantageous.

Further, since PBN is synthesized by a chemical vapor deposition (CVD) method, when a PBN monomer is used as a material, the shape is restricted, and since the graphite material coated with PBN is coated with PBN on the surface of the processed graphite. Therefore, since the shape can be freely provided, it is possible to obtain a jig and a member having a complicated shape of PBN characteristics in a short time.

Therefore, the graphite material coated with PBN has a wide range of adaptation and can be used for various members. For example, it can be used as a material for a wafer tray, a vapor deposition material melting crucible, a heater, a reaction container, a heat protection member, a crystal pulling crucible, or the like. In addition, since it exhibits excellent corrosion resistance to high-temperature NH ₃ , it can also be used for a crucible for GaN single crystal growth, a jig for a GaN epitaxial film growth apparatus, and the like.

However, since a graphite material coated with PBN, PG, SiC, TaC or the like is used as a material of a jig or a member which is not applicable in the case of only graphite, it has been considered that the base graphite is not exposed well. For this reason, a coating material of PBN, PG, SiC, TaC or the like is usually coated on the entire surface of the graphite substrate. However, since the position of the support substrate cannot be covered by one application, in order to coat the graphite substrate over the entire surface, it is necessary to move the support position of the substrate after the first application for the second time. Coating. This requires twice the cost of one application, and there is a problem that it is uneconomical.

Therefore, in order to coat the entire surface of the substrate by one application, Patent Document 1 proposes a coating method in which a suspension is suspended on a cross-sectional area having a smaller diameter than a through hole provided in a substrate. On the rod, the support point of the substrate is continuously moved by the reaction process. However, this method has a problem in that it can be applied only to a substrate having a shape of a through hole at the center.

Further, Patent Document 2 discloses a method in which a SiC plate is fitted or attached to a part of a base material, and SiC is coated on the entire surface of the base material by one application using the SiC plate as a support portion. However, this method also has a problem in that extra cost is required for inserting or attaching the SiC plate, and the coating film may be peeled off from the portion to be fitted or attached.

In addition, as for the coated graphite material of PBN, PG, SiC, TaC, etc., since materials of different physical properties are combined, it is pointed out that the disadvantage is due to the high temperature region. Unlike the coefficient of thermal expansion in the low temperature region, peeling of the coating film is liable to occur. In response to this problem, Patent Document 3 describes an attempt to form a coating film of PBN by a CVD method after attempting to surface-treat a graphite material with a plasma and/or a reactive gas. However, even in such a coated graphite material, although a certain degree of improvement has been obtained, there is still a problem that peeling of the coating film is likely to occur.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] JP-A-63-134663

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2000-129444

[Patent Document 3] Japanese Laid-Open Patent Publication No. 62-207786

In view of the above problems, the inventors have found through repeated studies that the peeling problem of the coated graphite material coated with PBN, PG, SiC, TaC, etc. is the pressure difference between the inside and outside of the coating film in a device under reduced pressure or under vacuum. caused. That is, it was found that when the coated graphite material is used in a device under reduced pressure or under vacuum, when the gas in the device is subjected to the exhaust treatment, the gas existing in the gap of the coated graphite substrate is surrounded by the dense coating film. Therefore, there is a case where the exhaust speed is slow. As a result, a pressure difference occurs between the inside and the outside of the coating film, and the pressure difference causes peeling of the coating film, thereby contributing to the present invention.

Accordingly, it is an object of the present invention to provide a method that is difficult to produce under reduced pressure or vacuum. A coated graphite member having a pressure difference between the inside and the outside of the coating film and having a thermal shock resistance and causing peeling of the coating film is unlikely to occur.

The present invention is a coated graphite member in which a surface of a graphite substrate is coated with a material such as PBN, PG, SiC or TaC, and a part of the graphite substrate is exposed. Further, it is preferable that the exposed portion of the graphite base material has a countersunk hole or a screw hole shape which is concave with respect to the surface of the base material, and has an area of 1 mm ² or more and 1200 mm ² or less.

Further, it is preferable that the exposed portion of the graphite substrate is provided at a portion having a temperature of 1500 ° C or lower, or at a portion not in contact with a gas corrosive to graphite.

According to the present invention, since a portion where the graphite is exposed is provided in a part of the coated graphite member, the gas existing in the gap of the graphite material can be easily discharged even when used under reduced pressure or under vacuum, so that it is less likely to be generated. The pressure difference between the inside and the outside of the film prevents the peeling of the coating film due to the pressure difference.

1‧‧‧coated graphite members

2‧‧‧Graphite substrate

3‧‧‧Exposed Department

4‧‧‧ countersunk hole

5‧‧‧ screw holes

6‧‧‧Retaining components

7‧‧‧Disc

8‧‧‧Axis

9‧‧‧heating mechanism

1(a) to 1(f) are schematic cross-sectional views showing the shape of a countersunk hole or a screw hole in an exposed portion of a graphite substrate of the present invention.

2(a) to 2(f) are schematic cross-sectional views showing an embodiment in which an exposed portion of the graphite substrate shown in Fig. 1 is held by a holding member.

Fig. 3 is a schematic view of a coated graphite member used in the examples.

Fig. 4 is a schematic cross-sectional view showing a state in which the coated graphite member of Fig. 3 is held by a holding member.

Fig. 5 is a schematic cross-sectional view showing a state in which a coated graphite member produced is subjected to a heating and cooling test.

Embodiments of the invention are specifically described below.

The coated graphite member of the present invention is used as, for example, a wafer tray, a vapor deposition material melting crucible, a heater, a reaction container, a heat protection member, a wafer, a phosphor manufacturing container, a phosphor manufacturing jig, and a ceramic sintering. The material of the bracket, the alloy heat treatment annealing furnace, etc., but its use is not limited, and its shape can be freely designed according to the use and purpose.

In particular, the PBN-coated graphite member can be used as a GaN single crystal culture vessel, a reactor, a heater for a MOCVD apparatus for GaN growth, a carrier disk, a heat shield, and the like.

The graphite base material of the present invention is produced by forming graphite by a method such as machining. The material is isotropic graphite, extruded graphite, mold-forming graphite, carbon fiber-reinforced carbon composite (C/C composite) and the like. The manufacturing method is not limited to a method such as machining, and a part of different materials may be used in combination as a graphite substrate.

The formed graphite substrate is formed with a coating film of a different material on the surface thereof while being held by the holding member. At this time, PBN, PG, SiC, Materials such as TaC are used as the coating material, but are not limited to these materials, and a plurality of materials may be combined. In addition, it is also possible to select a suitable covering material according to its use and purpose.

Further, in the case of coating PBN, PG, SiC, or TaC, the CVD method is generally employed as the coating method, but other methods may be employed. For example, as a method of coating PBN on a graphite substrate, a method is known in which a graphite substrate is heated from 1700 ° C to 2300 ° C under a reduced pressure of 1000 Pa or less, and is made to react with BCl ₃ gas and NH ₃ gas. In contact, a vapor deposited film of PBN is formed on the graphite substrate.

The coated graphite member of the present invention is characterized in that a part of the graphite substrate is exposed. Further, by this, even if it is used under vacuum, the gas existing in the gap of the graphite substrate can be easily discharged, so that a pressure difference does not easily occur inside and outside the coating film.

The exposed portion which is a feature of the present invention can be provided by any method. The portion held by the holding member holding the graphite base material may be used as an exposed portion, or the portion not covered with the covering material may be provided by partial shielding. Further, the exposed portion may be provided by removing a portion of the covering material that has been coated. However, if the portion supported by the holding member is used as the exposed portion, the coating step can be completed once, so that it is not necessary to newly provide the exposed portion. The required working hours are preferred from the viewpoint of manufacturing efficiency. Further, such an exposed portion may be provided in one place or in a plurality of places.

The shape of the exposed portion is not particularly limited, but is preferably a counterbore or a screw hole shape that is concave with respect to the surface of the substrate. If a concave shaped counterbore or screw hole is provided in advance on the graphite substrate, and a countersunk head is provided on the holding member When the protrusion of the hole or the screw hole has a shape corresponding to the shape, the graphite substrate can be easily held by fitting the counterbore or the screw hole of the graphite base material to the protrusion of the holding member.

The shape of the counterbore may be, for example, various shapes as shown in FIGS. 1(a) to 1(f) or a combination of these. Further, when the counterbore 4 is viewed from the upper portion, the shape may be circular or polygonal, but if it is polygonal, the graphite substrate 2 can be kept in rotation. If the screw hole 5 is provided in the graphite substrate 2, an external thread of the same shape may be provided on the holding member. In this case, since the graphite base material 2 can be held more stably, it is possible to prevent the coating film coating process from being poured, thereby improving the yield of the manufacturing. Further, in the case where the graphite substrate is held by the holding member, it is usually supported by a plurality of pillars, but the graphite substrate is held by such countersunk holes or screw holes, as shown in Fig. 2(a) to Fig. 2(f) As shown in FIG. 4, the graphite base material 2 can be held by the holding member 6 at one location.

Regarding the area of the exposed portion, it is necessary to set the size so as to easily discharge the gas existing in the gap of the graphite substrate so that a pressure difference does not occur inside and outside the coating film, and therefore it is at least 1 mm ² or more. This is because if the area of the exposed portion is less than 1 mm ² , the discharge rate of the gas existing in the gap of the graphite substrate when used under vacuum is slow, and a pressure difference occurs inside and outside the coating film to cause the coating film. The hidden danger of stripping. Thus, when the area of the exposed portion is at least 1mm ² or more, more preferably 3mm ² or more, further 10mm ² or more is good, the coating film can be made to be peeled it becomes difficult to occur. In addition, depending on the size and shape of the member, if the area of the exposed portion is 30 mm ² or more, and more preferably 80 mm ² or more, the graphite substrate can be easily held by the holding member provided with the protrusion as described above. Therefore, it is better.

Further, since the coated graphite member is often used under conditions in which only the graphite substrate is not applicable, it is not desirable that the exposed portion of the graphite substrate is excessively large. In particular, when it is used in a gas atmosphere in which the graphite substrate is corrosive, since the exposed portion of the graphite substrate is consumed by the corrosive gas, the service life is shortened, so that the area of the exposed portion is preferably 1000 mm ² or less. Preferably, it is 500 mm ² or less, and further preferably 100 mm ² or less. In fact, although the peeling of the coating film does not occur even if the area of the exposed portion exceeds 1000 mm ² , it can be used. However, as the number of uses increases, the graphite substrate is continuously consumed by the corrosive gas, resulting in a shortened service life. Therefore, it is preferably 1200 mm ² or less.

Therefore, the area of the exposed portion is preferably 1 mm ² or more and 1200 mm ² or less in order to suppress peeling of the coating film, and is preferably 1 mm in order to suppress consumption of the graphite substrate and maintain a long service life. ² or more and 1000 mm ² or less.

The position of the exposed portion is not particularly limited, and may be arbitrarily selected. However, when the coated graphite member of the present invention is used in the presence of a gas corrosive to graphite, the exposed portion of the graphite substrate is preferably used. Set at a location that is not directly exposed to corrosive gases. For example, it may be provided at a portion covered by another member or a joint portion with other members. Thereby, corrosion of a graphite base material can be prevented, and it can be used stably for a long period of time.

Further, when the coated graphite member of the present invention is used in the presence of a gas which is corrosive to graphite, it is preferable to provide a portion which is provided at a temperature which is less consumed by corrosion of the graphite substrate. . At a temperature of 1000 ° C The following portions are less likely to cause corrosion of the graphite substrate and can be used for a long period of time, which is preferable. In fact, although the peeling of the coating film does not occur at a portion where the temperature exceeds 1000 ° C, it can be used. However, as the number of uses increases, the graphite substrate is continuously consumed, resulting in a shortened service life. Therefore, it is preferably placed at a temperature of 1500 ° C or less.

As described above, the position of the exposed portion is preferably a portion having a temperature of 1500 ° C or lower, and a portion having a temperature of 1000 ° C or lower is preferable in order to suppress a long life of the graphite substrate.

[Examples]

Hereinafter, embodiments of the present invention will be specifically described based on the drawings.

<Example 1>

In the first embodiment, first, the isotropic graphite was subjected to mechanical grinding processing to prepare a disk portion 7 having a diameter of 200 mm, a thickness of 10 mm, a shaft portion having a diameter of 20 mm, and a length of 50 mm as shown in FIG. A graphite substrate 2 in the shape of a disk. Then, as shown in FIG. 4, the bottom surface of the shaft portion 8 of the graphite substrate 2 is supported by the holding member 6, and after being placed in the high-temperature vapor deposition furnace, the inside of the furnace is evacuated by a vacuum pump, and the temperature is raised to about 2000 °C by heating.

Next, while maintaining the furnace temperature at about 2000 ° C and the furnace pressure at 1000 Pa or less, the surface of the graphite substrate 2 was coated with a PBN film by reacting BCl ₃ gas with NH ₃ gas. Further, since the portion supported at the time of PBN vapor deposition in this state was not coated, the PBN was coated again after the support portion was changed.

Then, after the inside of the furnace was returned to the normal temperature, the graphite member 1 having the entire surface covered with PBN was taken out and observed, and it was found that the PBN film was firmly attached to the surface of the graphite substrate 2, and peeling did not occur. Next, a part of the PBN coating film at the front end portion of the shaft portion 8 was removed by grinding, and the exposed portion 3 having a diameter of 2 mm was provided. The area of the exposed portion 3 at this time was 3.14 mm ² .

In addition, the coated graphite member 1 prepared by providing the exposed portion 3 was placed in a MOCVD apparatus for GaN film formation, and then the NH ₃ gas was blown at a flow rate of 1 L/min while evacuating the inside of the installation. In this state, a heating and cooling test was performed in which the center portion of the disk portion 7 of the carrier disk was heated to 1400 ° C at a temperature increase rate of 100 ° C / min, and then cooled to 400 ° C at a temperature decreasing rate of 50 ° C / min. FIG. 5 shows a case where the coated graphite member 1 is subjected to a heating and cooling test using the heating mechanism 9. In this test, when the center portion of the disk portion 7 of the carrier disk was 1400 ° C, the temperature of the exposed portion 3 of the graphite substrate 2 at the tip end of the shaft portion 8 was 1000 °C.

Finally, the heating and cooling test was repeated 100 times by the heating means 9, and it was confirmed that the PBN coating film was not peeled off. Further, when the heating and cooling test of the 100th time was completed, the consumption of the graphite substrate 2 was not confirmed.

<Example 2 to Example 5>

In the second to fifth embodiments, the coated graphite member 1 having the diameter and the area of the exposed portion 3 of the graphite substrate 2 changed to the size shown in Table 1 was produced in the same manner as in the first embodiment.

Then, the coated graphite member 1 produced was subjected to the same heating and cooling test as in Example 1 for 100 times, and it was confirmed that the PBN coating film was not peeled off. Moreover, regardless of which coated graphite member 1, the 100th heating and cooling is completed. At the time of the test, the consumption of the graphite substrate 2 was not confirmed.

<Example 6>

In Example 6, first, a graphite substrate 2 having a carrier disk shape of the same size as that of Example 1 was prepared. A counterbored hole 4 having a diameter of 5 mm and a depth of 5 mm was provided at the front end portion of the shaft portion 8 by machining. The area of the exposed portion 3 at this time was 98.2 mm ² . Then, the graphite base material 2 is supported by the holding member 6 having the projections that can be fitted to the formed counterbored holes 4, and is placed in the high-temperature vapor deposition furnace.

Next, the inside of the furnace is evacuated by a vacuum pump, and after heating to about 2000 ° C, the temperature in the furnace is maintained at about 2000 ° C, and the pressure in the furnace is maintained below 1000 Pa. By reacting BCl ₃ gas with NH ₃ gas, The surface of the graphite substrate 2 is covered with a PBN film.

Finally, the coated graphite member 1 produced was repeatedly subjected to the same heating and cooling test as in Example 1 for 100 times, and it was confirmed that the PBN coating film was not peeled off. Further, when the heating and cooling test of the 100th time was completed, the consumption of the graphite substrate 2 was not confirmed.

<Example 7 to Example 13>

In Example 7 to Example 13, a coated graphite member in which the diameter, depth, and area of the exposed portion 3 of the graphite substrate 2 were changed to the numerical values shown in Table 1 was produced in the same manner as in Example 6. 1.

Then, the coated graphite member 1 produced was repeatedly subjected to the same heating and cooling test as in Example 1 for 100 times, and it was confirmed that the PBN coating film was not peeled off. However, in the coated graphite members 1 of Examples 7 to 12, the end is ended. In the case of the heating and cooling test of the 100th time, the graphite substrate was not consumed. However, in the coated graphite member 1 of the thirteenth embodiment, the consumption of the graphite substrate 2 was confirmed from the end of the 90th heating and cooling test.

<Example 14>

In Example 14, the entire surface of the graphite substrate 2 was coated with PBN in the same manner as in Example 1, and then a countersunk hole 4 having a diameter of 5 mm and a depth of 5 mm was provided on the side portion of the shaft by machining. . The area of the exposed portion 3 at this time was 98.2 mm ² .

Next, the coated graphite member 1 produced was subjected to the same heating and cooling test as in Example 1. However, in this test, the central portion of the disk portion 7 was at the side portion of the shaft portion 8 at 1400 °C. The temperature of the exposed portion of the graphite substrate 2 was 1200 °C.

Finally, the coated graphite member 1 was repeatedly subjected to the above-described heating and cooling test 100 times, and it was confirmed that the PBN coating film was not peeled off. However, the consumption of the graphite substrate 2 was confirmed from the end of the 80th heating and cooling test. .

<Example 15>

In Example 15, first, a graphite substrate 2 having a carrier disk shape of the same size as that of Example 1 was prepared. Further, a counterbored hole 4 having a diameter of 5 mm and a depth of 5 mm was provided at the center portion of the disk portion 7 by machining. The area of the exposed portion 3 at this time was 98.2 mm ² . Then, the graphite substrate 2 is supported by a holding member 6 having a convex portion fitted to the formed counterbore 4, and is placed in a high-temperature vapor deposition furnace.

Next, the inside of the furnace is evacuated by a vacuum pump, and after heating to about 2000 ° C, the temperature in the furnace is maintained at about 2000 ° C, and the pressure in the furnace is maintained below 1000 Pa. By reacting BCl ₃ gas with NH ₃ gas, The surface of the graphite substrate 2 is covered with a PBN film.

Then, the coated graphite member 1 produced was subjected to the same heating and cooling test as in Example 1, and the maximum temperature of the exposed portion 3 of the graphite substrate 2 provided at the center portion of the disk portion 7 was placed in this test. It is 1400 °C.

Finally, the coated graphite member 1 produced by the heating mechanism 9 was subjected to the above-described heating and cooling test 100 times, and it was confirmed that the PBN coating film was not peeled off. However, it was confirmed from the end of the 50th heating and cooling test. Consumption of the graphite substrate 2.

<Comparative Example 1>

In Comparative Example 1, first, a graphite substrate 2 having a carrier disk shape of the same size as in Example 1 was prepared, and the bottom surface of the shaft portion 8 supporting the graphite substrate 2 was placed in a high-temperature vapor deposition furnace. The vacuum pump exhausts the furnace and heats it to about 2000 °C. Then, the temperature in the furnace was maintained at about 2000 ° C, the pressure in the furnace was maintained at 1000 Pa or less, and the surface of the graphite substrate 2 was coated with a PBN film by reacting BCl ₃ gas with NH ₃ gas.

Next, in this state, since the portion supported at the time of PBN vapor deposition is not coated, the position of the support is changed to cover the PBN again. Then, after the inside of the furnace was returned to the normal temperature, the graphite member 1 having the entire surface covered with PBN was taken out, and it was found that the PBN film was firmly adhered to the surface of the graphite substrate 2, and peeling did not occur.

In addition, in the comparative example 1, the coated graphite member 1 in which the exposed portion was not provided was repeatedly subjected to the heating and cooling test in the same manner as in the first embodiment, and the peeling of the coating film was confirmed in the third time.

2‧‧‧Graphite substrate

4‧‧‧ countersunk hole

Claims (5)

A coated graphite member is a coated graphite member coated with a different material on a surface of a graphite substrate, wherein a part of the graphite substrate is exposed, and an exposed portion of the graphite substrate is opposite to a surface of the substrate Concave shaped counterbore or screw hole shape. The coated graphite member according to claim 1, wherein an area of the exposed portion of the graphite substrate is 1 mm ² or more and 1200 mm ² or less. The coated graphite member according to the first or second aspect of the invention, wherein the exposed portion of the graphite substrate is provided at a temperature of 1500 ° C or lower. The coated graphite member according to the first or second aspect of the invention, wherein the exposed portion of the graphite substrate is provided at a portion that does not contact a gas corrosive to graphite. The coated graphite member according to claim 1 or 2, wherein the different material is at least any one of PBN, PG, SiC, and TaC.