JP2010064920A - Method for producing 6h silicon carbide single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a silicon carbide single crystal formed of 6H polytype only. <P>SOLUTION: A method for producing the 6H silicon carbide single crystal comprises: a step S1 of heating a crucible to a temperature T1 at which a sublimation raw material sublimes and subsequently reducing the pressure of inert atmosphere inside the crucible to a pressure P1 lower than the atmospheric pressure and maintaining the pressure P1 until a convex surface of the silicon carbide single crystal is formed on a seed crystal; a step S2 of increasing the pressure of inert atmosphere until it exceeds the pressure P1: and a step S3 of heating the crucible to a temperature T2 that is higher than the temperature T1 after the step S2 and subsequently reducing the pressure of inert atmosphere inside the crucible until sublimation of the sublimation raw material begins. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a silicon carbide single crystal for producing a silicon carbide single crystal formed of a single crystal polymorph.

  The silicon carbide single crystal has crystal polymorphs such as 4H type, 6H type, and 15R type. Silicon carbide single crystals are chemically stable and have unique semiconductor properties depending on the crystal polymorphism. Therefore, the silicon carbide single crystal is formed with an optimal crystal polymorph depending on the application.

For example, a method of manufacturing a 4H type silicon carbide single crystal by a sublimation recrystallization method is disclosed (see Patent Document 1). Specifically, in the manufacturing method of Patent Document 1, 15R type silicon carbide is used as a seed crystal. The silicon carbide raw material sublimated under a predetermined temperature condition and atmospheric pressure is recrystallized on a 15R type seed crystal to grow a 4H type silicon carbide single crystal.
JP 7-330493 A (paragraphs [0011] to [0013])

  By the way, since silicon carbide has many crystal polymorphs as described above, it is difficult to make different crystal polymorphs. In particular, when a silicon carbide single crystal is produced by a sublimation recrystallization method, transition between crystal polymorphs tends to occur during the crystal growth process.

  For example, the 15R type crystal growth condition is close to the 6H type. Therefore, even if the crystal polymorph of the seed crystal is appropriately selected as in the manufacturing method of Patent Document 1, the 15R-type silicon carbide single crystal is formed in the initial stage of growth of the process of manufacturing the 6H-type silicon carbide single crystal. There was a problem that it was easy to grow.

  Defects in which different crystal polymorphs exist in a silicon carbide single crystal are not preferable because they deteriorate the performance as a semiconductor device.

  Accordingly, an object of the present invention is to provide a 6H-type silicon carbide single crystal manufacturing method for manufacturing a silicon carbide single crystal formed of a single 6H-type crystal polymorph.

  In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that the sublimation raw material is sublimated under an inert atmosphere in a state where a seed crystal containing silicon carbide and a sublimation raw material containing silicon carbide are contained in a crucible. A method for producing a 6H type silicon carbide single crystal in which a 6H type silicon carbide single crystal is produced by recrystallizing the sublimation raw material on the seed crystal, wherein the first temperature at which the sublimation raw material is sublimated. After the crucible is heated to the first step, the pressure of the inert atmosphere in the crucible is reduced to a first pressure lower than atmospheric pressure, so that a convex surface of the silicon carbide single crystal is formed on the seed crystal. A second step in which the pressure of the inert atmosphere is increased above the first pressure, and after the second step, the crucible is heated to a second temperature higher than the first temperature, Until the sublimation of the sublimation raw material begins And summarized in that the pressure of the inert atmosphere 堝内 has a third step is reduced.

  According to the first feature of the present invention, after the convex surface of the silicon carbide single crystal is formed on the seed crystal at the first temperature and the first pressure at which the sublimation material is sublimated, the pressure in the inert atmosphere is the first pressure. When the pressure is increased, the crystal growth is temporarily stopped. Thereafter, crystal growth is started again under a second temperature higher than the first temperature.

  That is, in the first step, the silicon carbide single crystal is grown slowly under the first temperature and the first pressure until the convex surface of the silicon carbide single crystal is formed on the plane of the seed crystal. Subsequently, in the second step, the growth of the silicon carbide single crystal is temporarily stopped. Thereafter, since the silicon carbide single crystal is grown under the temperature condition of the third step, particularly in the initial stage until the convex surface of the silicon carbide single crystal is formed on the plane of the seed crystal, the 6H type silicon carbide single crystal is grown. Occurrence of polymorphic defects in which a 15R-type silicon carbide single crystal is generated in the crystal is suppressed.

  Therefore, it is possible to produce a silicon carbide single crystal of 6H type polymorphic single.

  The second feature of the present invention is related to the first feature of the present invention, wherein the first pressure is maintained in the first step until step flow growth of the silicon carbide single crystal becomes possible. And

  A third feature of the present invention relates to the first feature of the present invention. In the second step, the pressure of the inert atmosphere is higher than the first pressure until the growth of the silicon carbide single crystal stops. The gist is that it is raised.

  The fourth feature of the present invention relates to the third feature of the present invention, and is summarized in that the pressure of the inert atmosphere is increased to atmospheric pressure in the second step.

  A fifth feature of the present invention relates to the first feature of the present invention, and is summarized in that the first temperature is 2000 ° C. or higher and 2100 ° C. or lower.

  A sixth feature of the present invention relates to the first feature of the present invention, and is summarized in that the second temperature is 2200 ° C. or higher and 2400 ° C. or lower.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the 6H-type silicon carbide single crystal which manufactures the silicon carbide single crystal formed by single 6H-type crystal polymorphism can be provided.

  Next, an embodiment of a method for producing a 6H type silicon carbide single crystal according to the present invention will be described with reference to the drawings. Specifically, (1) Configuration of manufacturing apparatus, (2) Manufacturing method of 6H type silicon carbide single crystal, (3) Examples, (4) Actions and effects, (5) Other embodiments will be described.

(1) Structure of manufacturing apparatus The manufacturing apparatus 1 of the silicon carbide single crystal shown as embodiment of this invention is demonstrated using FIG. As shown in FIG. 1, the silicon carbide single crystal manufacturing apparatus 1 includes a graphite crucible 10, a quartz tube 20 covering at least a side surface of the graphite crucible 10, and a dielectric heating coil 30 disposed on the outer periphery of the quartz tube 20. And have.

  The graphite crucible 10 is fixed inside the quartz tube 20 by a support rod 40. The graphite crucible 10 is covered with a heat insulating material (not shown). The graphite crucible 10 has a reaction vessel main body 50 and a lid 60. The reaction vessel main body 50 accommodates a seed crystal 70 containing silicon carbide and a sublimation raw material 80 used for growing the seed crystal 70.

  The reaction vessel main body 50 is cylindrical at least inside. A seed crystal 70 is disposed inside the reaction vessel main body 50. Specifically, the seed crystal 70 is bonded to the inner surface 61 of the lid 60. The lid 60 is detachably provided on the reaction vessel main body 50 by screwing.

  The inside of the reaction vessel main body 50 is filled with an inert gas such as argon to form an inert atmosphere. The pressure and temperature inside the reaction vessel main body 50 can be changed.

  The seed crystal 70 is a silicon carbide single crystal such as 4H type, 6H type, or 15R type. The sublimation raw material 80 is a silicon carbide raw material containing silicon carbide. When the inside of the graphite crucible 10 reaches predetermined temperature conditions and pressure conditions, the sublimation raw material 80 sublimates and recrystallizes on the seed crystal 70 to form the silicon carbide single crystal 100.

  As the growth progresses, silicon carbide single crystal 100 forms convex surface 100a, and eventually grows along the inside of reaction vessel body 50 to form a cylindrical silicon carbide single crystal.

(2) Method for Producing 6H Type Silicon Carbide Single Crystal FIG. 2 is an explanatory view showing a method for producing a 6H type silicon carbide single crystal. As shown in FIG. 2, the 6H-type silicon carbide single crystal manufacturing method includes a step S1, a step S2, and a step S3.

  FIG. 3 is a schematic diagram for explaining changes in temperature conditions and pressure conditions in the method for producing a 6H-type silicon carbide single crystal. The temperature condition and pressure condition in each step are based on FIG. In FIG. 3, Tr represents room temperature and P0 represents atmospheric pressure.

  In step S1, graphite crucible 10 is heated from room temperature T0 to temperature T1 at which sublimation raw material 80 sublimes. Thereafter, the pressure of the inert atmosphere in the graphite crucible 10 is reduced to a pressure P1 lower than the atmospheric pressure P0. Here, the temperature T1 is preferably 2000 ° C. or higher and 2100 ° C. or lower.

  The pressure P1 is maintained until the convex surface 100a of the silicon carbide single crystal is formed on the seed crystal 70. Specifically, in step S1, the pressure P1 is maintained on the seed crystal 70 until the silicon carbide single crystal can be step-flow grown.

  In step S2, the pressure of the inert atmosphere in the graphite crucible 10 is raised above the pressure P1. Specifically, in step S2, the pressure of the inert atmosphere is raised above the pressure P1 until the growth of the silicon carbide single crystal is stopped. In step S2, the pressure of the inert atmosphere in the graphite crucible 10 may be increased to atmospheric pressure.

  In step S3, the graphite crucible 10 is heated to a temperature T2 higher than the temperature T1. Thereafter, the pressure of the inert atmosphere in the graphite crucible 10 is reduced until sublimation of the sublimation raw material 80 starts again. In step S3, the pressure is reduced to pressure P2. In the present embodiment, the temperature T2 constitutes the second temperature. Here, the temperature T2 is preferably 2200 ° C. or higher and 2400 ° C. or lower.

  In step S3, the growth of silicon carbide single crystal 100 is resumed by reducing the pressure to pressure P2.

  As described above, according to the method for manufacturing a silicon carbide single crystal of the present embodiment, the convex surface 100a of the silicon carbide single crystal 100 is formed on the seed crystal 70 at the temperature T1 and the pressure P1 at which the sublimation raw material 80 is sublimated. Then, since the pressure of the inert atmosphere in the graphite crucible 10 is raised above the pressure P1, the growth of the silicon carbide single crystal 100 is temporarily stopped. Thereafter, sublimation of the sublimation raw material 80 starts at a temperature T2 higher than the temperature T1, and the growth of the silicon carbide single crystal 100 is resumed.

(3) Example A silicon carbide single crystal was manufactured based on the above-described method for manufacturing a silicon carbide single crystal. Silicon carbide single crystals were produced under different production conditions, and the growth rate and crystallinity were compared. Conditions relating to the production are shown below.

<Example 1>
Step S1: The temperature was maintained at T1 = 2050 ° C. and the pressure P1 = 5 kPa for 20 hours.
Step S2: Pressure of inert atmosphere in graphite crucible 10 = atmospheric pressure Step S3: Temperature T2 = 2300 ° C. and pressure P2 = 10 kPa were maintained for 50 hours.

<Comparative Example 1>
The temperature in the graphite crucible 10 was 2300 ° C., and the pressure was kept at 70 ° C. under an inert atmosphere pressure = 10 kPa.

<Comparative example 2>
The temperature in the graphite crucible 10 was 2050 ° C., and the pressure was kept at 70 ° C. under an inert atmosphere pressure = 5 kPa.

The growth rate and crystallinity of the silicon carbide single crystal produced under the above conditions were measured. The results are shown in Table 1. In addition, the half value width by X-ray diffraction was used for evaluation of crystallinity. A half value width shows that crystallinity is so favorable that a value is small.

  As shown in Table 1, according to the method for producing the 6H-type silicon carbide single crystal of Example 1, the crystallinity is good and the growth rate is a value suitable for industrial production as compared with the comparative example. And found that it can be.

(4) Action / Effect According to the method for manufacturing a 6H-type silicon carbide single crystal of the present embodiment, the convex surface 100a of the silicon carbide single crystal is formed on the seed crystal 70 at the temperature T1 and the pressure P1 at which the sublimation raw material 80 is sublimated. After the formation, the pressure of the inert atmosphere in the graphite crucible 10 is raised above the pressure P1, and the growth of the silicon carbide single crystal is temporarily stopped. Thereafter, the growth of the silicon carbide single crystal resumes under a temperature T2 higher than the temperature T1.

  That is, according to the method for manufacturing the 6H-type silicon carbide single crystal of the present embodiment, until the convex surface 100a of the silicon carbide single crystal is formed on the seed crystal 70 under the temperature T1 and the pressure P1 in step S1. A silicon carbide single crystal is slowly grown. Subsequently, in step S2, the growth of the silicon carbide single crystal is temporarily stopped. Thereafter, since the silicon carbide single crystal is grown under the temperature condition of step S3, the 6H-type silicon carbide single crystal is grown especially until the convex surface 100a of the silicon carbide single crystal is formed on the plane of the seed crystal 70. Occurrence of polymorphic defects in which a 15R-type silicon carbide single crystal is generated in the crystal is suppressed.

  Therefore, it is possible to produce a silicon carbide single crystal of 6H type polymorphic single.

  Further, in the method for producing a 6H-type silicon carbide single crystal of the present embodiment, carbonization is performed at a temperature condition at which the crystal quality is easily improved, that is, 2000 ° C. or higher and 2100 ° C. or lower in the initial stage of growth of the crystal quality of the silicon carbide single crystal. When the silicon single crystal is grown and the convex surface 100a capable of step flow growth with which the crystal quality is easy to be stabilized is formed, the silicon carbide single crystal is grown at 2200 ° C. or higher and 2400 ° C. or lower, thereby preventing deterioration of the crystal quality. It is possible to achieve both improvement of the growth rate.

(5) Other Embodiments The content of the present invention has been disclosed according to an embodiment of the present invention. However, the present invention is not limited to the above discussion and drawings. Various embodiments that will be apparent to those skilled in the art based on the above discussion and drawings are all included in the present invention.

  In the step S1 of the present embodiment, the crucible is heated to a temperature T1 at which the sublimation raw material sublimates, and then the pressure of the inert atmosphere in the crucible is reduced to a pressure P1 lower than atmospheric pressure. However, after the pressure of the inert atmosphere in the crucible is reduced to a pressure P1 lower than atmospheric pressure, the crucible may be heated to a temperature T1 at which the sublimation raw material is sublimated. Heating and decompression may be performed simultaneously.

  In the present embodiment, the pressure of the inert atmosphere in the graphite crucible 10 at the end of the step S2 has been described as being a value smaller than the atmospheric pressure P0, but may be the atmospheric pressure P0. Further, the pressure P2 has been described as a value larger than the pressure P1, but the pressure P2 may be smaller than the pressure P1 at the end of the step S2.

  The technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is a block diagram explaining the manufacturing apparatus of the silicon carbide single crystal which concerns on embodiment of this invention. It is a flowchart explaining the manufacturing method of the 6H type silicon carbide single crystal which concerns on embodiment of this invention. It is a mimetic diagram explaining change of temperature conditions and pressure conditions in a manufacturing method of 6H type silicon carbide single crystal concerning an embodiment of the invention in this application.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Manufacturing apparatus of a silicon carbide single crystal, 10 ... Graphite crucible, 20 ... Quartz tube, 30 ... Dielectric heating coil, 40 ... Support rod, 50 ... Reaction vessel main body, 60 ... Cover part, 61 ... Inner surface, 70 ... Seed crystal, 80 ... raw material for sublimation, 100 ... silicon carbide single crystal, 100a ... convex surface, Tr ... room temperature, P0 ... atmospheric pressure

Claims (6)

With the seed crystal containing silicon carbide and the sublimation raw material containing silicon carbide contained in a crucible, the sublimation raw material is sublimated in an inert atmosphere, and the sublimation raw material is re-applied on the seed crystal. A method for producing a 6H-type silicon carbide single crystal in which a 6H-type silicon carbide single crystal is produced by being crystallized.
After the crucible is heated to a first temperature at which the sublimation raw material is sublimated, the pressure of the inert atmosphere in the crucible is reduced to a first pressure lower than atmospheric pressure, and a silicon carbide single crystal is formed on the seed crystal. A first step in which a convex surface of the crystal is formed;
A second step in which the pressure of the inert atmosphere is increased above the first pressure;
After the second step, after the crucible is heated to a second temperature higher than the first temperature, the pressure of the inert atmosphere in the crucible is reduced until the sublimation raw material starts sublimation. A method for producing a 6H-type silicon carbide single crystal comprising three steps.   2. The method for producing a 6H-type silicon carbide single crystal according to claim 1, wherein in the first step, the first pressure is maintained until step flow growth of the silicon carbide single crystal becomes possible. 3.   2. The method for producing a 6H-type silicon carbide single crystal according to claim 1, wherein in the second step, the pressure of the inert atmosphere is increased above the first pressure until the growth of the silicon carbide single crystal is stopped.   The method for producing a 6H-type silicon carbide single crystal according to claim 3, wherein in the second step, the pressure of the inert atmosphere is increased to atmospheric pressure.   2. The method for producing a 6H-type silicon carbide single crystal according to claim 1, wherein the first temperature is 2000 ° C. or higher and 2100 ° C. or lower.   The method for producing a 6H-type silicon carbide single crystal according to claim 1, wherein the second temperature is 2200 ° C or higher and 2400 ° C or lower.

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