JP3693739B2 - High frequency induction furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency induction heating furnace that performs crystal growth or heat treatment of silicon carbide (SiC, silicon carbide) for semiconductors.
[0002]
[Prior art]
A conventional high-frequency induction heating furnace for crystal growth or heat treatment of silicon carbide for semiconductors has a heat treatment part 1 such as a graphite crucible or susceptor made of a quartz tube as shown in a schematic partial sectional view of FIG. The reaction tube 2 is installed in the formed reaction tube 2 with a support 3, a high-frequency current is passed through the heating coil 4 wound around the reaction tube 2, and is in contact with a crucible or susceptor that has been heated to high temperature by induction heating. A sample (not shown) is heated to a high temperature to perform crystal growth or heat treatment. Note that the quartz tube forming the reaction tube 2 has a double structure, and cooling water is passed between them to suppress the temperature rise of the reaction tube 2. Although not shown in the drawing, the reaction tube 2 is provided with a communication pipe connected to a gas inlet or a vacuum device, and a predetermined amount of a required gas is allowed to flow during the reaction to control the pressure.
[0003]
Typical case of the method, by heating the SiC single crystal as a seed on the susceptor in the normal 1500 ° C. or less, containing silicon into the reaction tube 2 gas in the furnace put that crystal growth (e Hoon Takisharu growth) (Silane etc.) and carbon containing gas (propane etc.) are introduced, and SiC is grown on the seed crystal by a chemical reaction by heat. In the case of the sublimation method, which is another method, the SiC powder in the crucible is heated at 2000 ° C. or higher to be sublimated and then solidified, and crystals are grown on the substrate in the space in the crucible. .
[0004]
In the case of heat treatment, the reaction tube 2 is filled with a non-reactive gas such as argon gas or nitrogen gas, and SiC is heated to about 2000 ° C.
However, when crystal growth or heat treatment is performed, if the temperature of the heat treatment unit 1 such as a crucible or susceptor becomes high and the temperature difference between the reaction tube 2 and the outside air becomes large, a large amount of radiant heat is emitted. This causes a problem that heat is lost outside the furnace and heating loss is large. Therefore, when using the crucible pressurized thermal processing unit 1, as shown in FIG. 4, the periphery and the bottom of the crucible 5, the heat shield of the cylindrical carbon felt consisting of excellent graphite warmth-insulation effect In some cases, a means for shielding the heat by reflecting the radiant heat by covering with a heat shield plate 7 of the same type as that of the disk 6 may be provided. In FIG. 4, 8 is SiC powder, 9 is a substrate, 10 is a cylindrical heat shield, 11 is a crucible carbon felt lid, and 12 is a crucible support.
[0005]
[Problems to be solved by the invention]
However, when the heating furnace is used at a temperature of 1500 ° C. or higher, the carbon felt heat shield 6 is also at a considerably high temperature, so that impurities mixed in the carbon felt and the carbon felt itself are released, resulting in a high-purity atmosphere. There was a problem that the required furnace was contaminated and impurities were mixed into the heated sample. Therefore, when the temperature of the heating furnace is used at 1500 ° C. or lower, the above-described carbon felt heat shield 6 is used in order to keep the atmosphere in the furnace at a high purity even if the loss of radiant heat is sacrificed to some extent. I try not to. However, when used at a high temperature around 2000 ° C., the carbon felt heat shield 6 must be used even if the purity of the atmosphere in the furnace is sacrificed to some extent.
[0006]
Further, during the crystal growth of silicon carbide for semiconductors, the above-described reaction gas necessary for crystal growth is flowed, and polycrystalline SiC as an undesirable byproduct is deposited and deposited on the inner wall of the reaction tube 2 by the action of this reaction gas. There's a problem. That is, the reaction tube 2 becomes opaque due to the adhesion / deposition of polycrystalline SiC, and the reaction tube 2 is cracked due to the difference in thermal expansion coefficient between the quartz constituting the reaction tube 2 and the deposited / deposited polycrystalline SiC. There is a problem of cracking.
Further, in the step of adding a dough Pas cement during the crystal growth, using the dough Pas cement material gas that A in a certain step, when using a different dough Pas cement material gas that B was used in the next step above dough Pas cement that a ends up depositing on the inner wall of the reaction tube 2 with polycrystalline SiC, which during the subsequent step is diffused, there is a problem that mixed crystal of manufacturing. Therefore, it is necessary to periodically clean the reaction tube 2 with chemicals.
The present invention provides a high-frequency induction heating furnace that effectively solves such problems in the case of crystal growth or heat treatment of silicon carbide for semiconductors .
[0007]
[Means for Solving the Problems]
In the high frequency induction heating furnace according to the present invention, a crucible or a susceptor is installed in a reaction tube formed of a quartz tube, and a high frequency current is supplied to a heating coil arranged on the outer periphery of the reaction tube to supply the crucible or susceptor. In a high-frequency induction heating furnace that performs crystal growth or heat treatment of silicon carbide for semiconductors, a heat shield tube made of silicon carbide is provided in the reaction tube so that the crucible or susceptor is installed therein. It is characterized by having.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a cross-sectional view schematically showing one embodiment of a high-frequency induction heating furnace (vertical type) according to the present invention. The same parts as those in FIG. In FIG. 1, reference numeral 13 denotes a cylindrical silicon carbide heat shielding tube made of high-purity silicon carbide. A heat treatment unit 1 such as a crucible or a susceptor (the heat treatment unit 1 in FIG. 1 shows an example of a susceptor). .) Is accommodated in a non-contact manner. The silicon carbide heat shield tube 13 is preferably made of high-purity silicon carbide having high heat resistance and few impurities. Further, in order to improve the performance of the silicon carbide heat shield tube 13, it is desired that at least the inner peripheral surface thereof be subjected to SiC coating treatment. For this SiC coating, a method of forming a high-purity SiC film having a dense structure and low impurities by chemical vapor deposition is employed. The SiC film can be formed to a thickness of several μm to several mm, but a thickness of about 50 to 200 μm is usually appropriate.
[0009]
Further, the silicon carbide heat shield tube 13 is arranged by providing a positioning guide (not shown) on the support base 14 provided in the heating furnace, but the lower surface of the reaction tube 2 is directly arranged as the support portion 15. You may make it do. Further, in order to increase the heat shielding efficiency in the silicon carbide heat shielding tube 13, a doughnut-like heat shielding plate 16 made of silicon carbide is provided on the upper portion of the silicon carbide heat shielding tube 13 as shown in FIG. A heat shielding plate 17 on a disk made of silicon carbide is provided below the tool 3. 1 shows a susceptor, a crucible may be provided instead of the susceptor. A sample 18 is placed on the heat treatment unit 1 (susceptor), and a gas inlet 20 and the like are provided in the sealing unit 19 at the top of the reaction tube 2.
[0010]
FIG. 2 schematically shows a high-frequency induction heating furnace (horizontal type) according to another embodiment of the present invention. FIG. 2 (a) is a front sectional view, and FIG. 2 (b) is a side sectional view in which a heating coil is omitted. It is. In the structure of FIG. 2, a pair of rails 21 made of quartz are provided in the longitudinal direction of the reaction tube 2 inside the reaction tube 2 made of a double-structured quartz tube, and on this rail 21, silicon carbide is used. A configured susceptor base 22 is provided in the reaction tube 2 so that it can be taken in and out. On this susceptor base 22, a semi-cylindrical heat shielding cover 23 made of silicon carbide and having a partial opening in the longitudinal direction for engaging with the base is provided. The cylindrical heat shielding cover 23 forms a substantially cylindrical silicon carbide heat shielding cylinder. Inside this, a susceptor 24 made of graphite is supported by six columnar support jigs 25a to 25f made of silicon carbide, and a sample to be heat-treated is placed on this upper surface. The reason why the susceptor 24 is provided on the right side in the drawing is that the material gas is supplied from the right direction.
In the embodiment of FIG. 2, the heat shielding by silicon carbide is divided into two bodies, a susceptor base 22 and a semi-cylindrical heat shielding cover 23, but this is constituted by an integral heat shielding tube. A susceptor may be inserted inside using a rail or the like.
[0011]
In the present invention, since the heat treatment unit 1 such as a crucible or a susceptor is covered with the substantially cylindrical heat shielding cylinder made of the silicon carbide heat shielding tube 13 or the separable silicon carbide. It serves as a reflector that shields radiated heat and reflects radiated heat. Therefore, it is possible to promote soaking in the vicinity of the sample inside the high-temperature furnace and to efficiently heat the heat treatment unit. In particular, since the SiC coating film having high SiC purity is formed by performing SiC coating on the surfaces of the silicon carbide heat shielding tube 13, the heat shielding cover 23, and the susceptor pedestal 22 by chemical vapor deposition, the silicon carbide heat shielding tube 13 or the heat Impurities slightly contained in the silicon carbide constituting the shielding cover 23 are not released to the outside, and the atmosphere in the heating furnace can be further increased in purity.
[0012]
Further, when the material gas is introduced into the reaction tube 2 during the crystal growth of silicon carbide, the active gas generated in the heat treatment unit 1 is directly generated because the silicon carbide heat shielding tube 13 or the heat shielding cover 23 is installed. Since the quartz tube constituting the reaction tube 2 is not touched, the polycrystalline SiC is prevented from being deposited on the inner surface of the quartz tube. Therefore, there is no problem that the quartz tube is cracked or broken.
Further, polycrystalline SiC that occurs during the crystal growth described above is to be deposited on the inner surface of the silicon carbide heat shielding pipe 13 or the heat shielding cover 23, when in step is changed changing the type of dough Pas cement, heat shield tube 13 or the heat shield cover 23 so as to replace each time, it is possible to prevent mixing of the dough Pas cement from different processes. At the same time, since polycrystalline SiC is not deposited on the quartz tube, the frequency of cleaning the quartz tube can be reduced.
[0013]
【The invention's effect】
As described in detail above, the present invention uses a silicon carbide heat shield tube or a substantially cylindrical heat shield tube that can be divided as a heat shield member, so that high-temperature heat treatment of a sample at 2000 ° C. or more can be performed efficiently and It can be performed in a high purity atmosphere. In addition, the silicon carbide heat shielding tube or the like also serves as a reflector that reflects radiant heat, and can promote soaking in the vicinity of the sample in the high temperature furnace.
Moreover, when the present invention is applied to a high temperature furnace of about 1500 ° C., unnecessary polycrystalline SiC can be prevented from being deposited on the inner wall of the quartz tube constituting the reaction tube, and the quartz tube is not required to be cleaned. crack preventive quartz tube is achieved, and is intended to achieve the extremely remarkable effect and preventing contamination of the dough Pas cement from different steps of the sample is achieved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing one embodiment of a high frequency induction heating furnace of the present invention.
FIG. 2 is a front sectional view and a side sectional view schematically showing another embodiment of the high frequency induction heating furnace of the present invention.
FIG. 3 is a cross-sectional view schematically showing an example of a conventional high-frequency induction heating furnace.
FIG. 4 is a cross-sectional view schematically showing an example of a crucible used in a conventional high-frequency induction heating furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heat processing part 2 such as a crucible or a susceptor 2 Reaction tube 3 Support tool 4 Heating coil 5 Crucible 6 Cylindrical carbon felt heat shield 7 Disc-shaped carbon felt heat shield plate 8 SiC powder 9 Substrate 10 Heat radiation shield 11 Carbon Felt lid 12 Crucible support portion 13 Silicon carbide heat shield tube 14 Support base 15 Support portion 16 Donut-like heat shield plate 17 Disc-like heat shield plate 18 Sample 19 Sealing portion 20 Gas inlet 21 Rail 22 Susceptor base 23 Cover 24 Susceptor 25 Support jig

Claims (3)

Crystal growth of silicon carbide for semiconductors supplied to the crucible or susceptor by installing a crucible or susceptor in a reaction tube formed by a quartz tube and passing a high-frequency current through a heating coil disposed on the outer periphery of the reaction tube Or in a high-frequency induction furnace that performs heat treatment ,
A high-frequency induction heating furnace comprising a heat shield tube made of silicon carbide provided in the reaction tube so that the crucible or susceptor is installed therein. The high frequency induction heating furnace according to claim 1, wherein a SiC film is formed on at least an inner peripheral surface of the heat shield tube by chemical vapor deposition.   The high-frequency induction heating furnace according to claim 1 or 2, wherein the heat shield tube is formed as a substantially cylindrical heat shield cylinder that can be divided into a plurality of parts.

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