JP6598111B2 - Method for producing SiC single crystal - Google Patents

Description

  The present invention relates to a method for producing a SiC single crystal using a solution method.

  SiC is attracting attention as a material for next-generation power devices. In order to use this SiC as a material for electronic devices, it is necessary to obtain a high-quality SiC single crystal. There are various methods for producing single crystals, but the solution method (solution pulling method) is similar to the production of single crystals of silicon that produce single crystals by the melt method, and efficiently produces large single crystals of high quality. It is an effective way to do this. However, when the solution method is applied to the production of a single crystal of SiC, if SiC is used as a starting material, SiC is sublimated at 2000 ° C. when heated under normal pressure, and does not become a melt. Therefore, a single crystal of SiC cannot be produced simply by a method using a general solution method.

For this reason, the conventional method for producing a SiC single crystal by the solution method is to supply silicon (Si), which is a composition material, to a crucible made of graphite, and then melt the Si to produce a SiC single crystal. It is a method to do. In this manufacturing method, graphite (C) is melted into a Si melt from a crucible, so that C is supplied to Si and a SiC single crystal grows.
However, the amount of C (carbon) that dissolves from the graphite crucible into the Si melt is very small (less than 0.01% at 1500 ° C and about 0.45% at 2050 ° C), so that the growth rate of SiC single crystals can be improved. It is necessary to dissolve more C in the Si melt. A method that is considered as a method for efficiently dissolving C in the Si melt is a method that makes C easily dissolve in the Si melt by adding Cr, Ti, or Al to the Si melt (patent) Literature 1, 2, 3). According to this method, C can be efficiently dissolved in a Si melt from a graphite crucible, and a SiC single crystal can be formed.

However, the method using a graphite crucible has a problem that as the SiC grows, Si components are gradually lost from the Si-C solution and the composition of the solution changes. In addition, there is a problem that excessive dissolution of C from the graphite crucible into the melt causes a change in the composition of the Si-C solution, and a crystal dislocation occurs due to the change in the solution composition, resulting in a complete single crystal. There is also a problem.
As a method for solving these problems, there are a method of supplying SiC after the start of SiC growth (Patent Document 4), a method of using a crucible containing SiC as a main component (Patent Document 5), and the like.

JP 2000-264790 A JP 2004-2173 A JP 2008-303125 A JP 2011-98553 A JP2015-110501A

  An object of the present invention is to provide a method for producing an SiC single crystal by a solution method without causing a change in the composition of Si and C in the solution.

A method for producing a SiC single crystal according to the present invention is a method for producing a SiC single crystal by a solution method using a material made of SiC and using the material and a solvent metal, on the material. Place and heat only the solvent metal, position the solvent metal melt on top of the material, contact a SiC seed crystal with the solvent metal melt, and place the solvent metal melt in the solvent metal melt. By eluting Si and C from the material, SiC is precipitated on the seed crystal to grow a single crystal of SiC.

In the method for producing a SiC single crystal according to the present invention, a method for growing a SiC single crystal by containing a material and a solvent metal in a crucible and a method for growing a SiC single crystal without using a crucible are possible. .
In the method using a crucible, the SiC single crystal is grown by disposing the material on the bottom side of the crucible, disposing the solvent metal on the material and heating.
As the crucible, a crucible made of graphite can be suitably used. In this method, a SiC single crystal can be grown by using a crucible made of graphite and suppressing the dissolution of carbon from the crucible into the solvent metal melt.

In the method not using a crucible, a solidified body made of block-shaped SiC is used as the material, and only the solvent metal is placed on the material and heated, and the melt of the solvent metal is formed on the material. By holding, a single crystal of SiC is grown without using a crucible.
In this method, the solvent metal melt is held by surface tension on the top surface of the material. A SiC single crystal can be grown by bringing the seed crystal into contact with the melt held in the material. The solidified body in the form of a block means that a material capable of maintaining shape retention is used as the material, and the solidified body has an arbitrary three-dimensional shape such as a columnar shape or a prismatic shape. The formation method of the solidified body is not limited to the sintering method, and a solidified body can be used as appropriate.

As the solvent metal, a metal capable of eluting SiC from the material is used. The following 1) to 5) are listed as properties required for the solvent metal.
1) A material capable of dissolving Si and C in a solvent metal melt. In particular, those having a high solid solubility limit of Si and C and being almost equivalent are preferable.
2) Solvent metal component is difficult to segregate in SiC crystal (not taken in) or has a very low amount of contamination.
3) A solvent metal component and Si and C are less likely to form a compound, or SiC is easier to form than a compound with a solvent metal.
4) Those which are difficult to evaporate or sublime at high temperatures in the form of a solvent metal component alone or a compound with Si or C.
5) The melting point of the solvent metal is below the decomposition point of SiC (2780 ° C).
Examples of solvent metals that satisfy these conditions include Cr (chromium) and Ni (nickel).

  According to the method for producing a SiC single crystal according to the present invention, the SiC single crystal can be produced without changing the composition ratio of Si and C in the solution in the crystal growth step. Since the composition ratio of Si and C in the solution does not change, a high-quality SiC single crystal can be produced.

It is explanatory drawing which shows 1st Embodiment of the manufacturing method of a SiC single crystal. It is a cross-sectional photograph of a crucible in a state where SiC ceramics and a solvent metal are housed in a crucible and the solvent metal is melted and then cooled to room temperature. It is a figure which shows the analysis result (carbon distribution) of EPMA (electron beam microanalyzer) of the crucible surface after temperature-falling to room temperature. It is a figure which shows the analysis result (chromium distribution) of the EPMA of the crucible surface after temperature-falling to room temperature. It is a figure which shows the analysis result (silicon distribution) of the EPMA of the crucible surface after making it cool to room temperature. They are a photograph (a) of the end face of the support shaft after the crystal growth experiment and a Raman spectrum (b) of the end face. They are a photograph (a) and a Raman spectrum (b) immediately below the seed crystal of the crucible after the crystal growth experiment. It is explanatory drawing which shows 2nd Embodiment of the manufacturing method of a SiC single crystal.

(First embodiment)
The method for producing a SiC single crystal according to the present invention relates to a method for producing a SiC single crystal by a solution pulling method, using a solid made of SiC as a material, and using a solid of SiC and a solvent metal. Manufacture single crystals of SiC.
FIG. 1 shows the configuration of a first embodiment of a method for producing a SiC single crystal according to the present invention. In the method for producing an SiC single crystal shown in FIG. 1, a material 20 made of SiC solid (sintered body) is housed in a crucible 10 made of graphite (carbon), and a solvent metal 30 is placed on the material 20. SiC single crystal is manufactured.

  In FIG. 1, a crucible 10 is set inside a resistance-heating type carbon heater 12 formed in a cylindrical shape, and a support means 16 for supporting a SiC seed crystal 14 is disposed above the center position of the crucible 10. The support means 16 includes an elevating mechanism that positions the elevating position of the seed crystal 14. The seed crystal 14 is attached to the lower end of the support means 16.

The characteristic feature of the crystal manufacturing method shown in FIG. 1 is that a material 20 made of SiC is placed on the bottom of the crucible 10, a solvent metal 30 is placed on the material 20 and heated, thereby melting the solvent metal 30. The liquid and the material 20 are brought into contact with each other, and Si and C are eluted from the material into the melt of the solvent metal 30 to grow a SiC single crystal.
The height of the seed crystal 14 is controlled by the support means 16 so as to be immersed in the melt of the solvent metal 30 in the vicinity of the surface of the melt of the solvent metal 30. Si and C are eluted from the material 20 into the melt of the solvent metal 30 and SiC is deposited on the seed crystal 14, and a SiC single crystal grows from the seed crystal.

In the method for producing a single crystal of SiC according to the present embodiment, a crucible 10 made of graphite is used as a crucible containing the material 20 and the solvent metal 30. Therefore, carbon may be dissolved from the crucible 10 into the melt of the solvent metal 30 during the growth of the SiC single crystal.
Figure 2 shows a crucible after containing SiC ceramic B as a material in crucible A, supplying Cr powder as solvent metal C onto SiC ceramic B, heating to about 1950 ° C, and then cooling to room temperature. FIG.
In Fig. 2, when the interface part between the solvent metal and the SiC material (dotted square: D part) is seen, the surface of the SiC ceramic becomes uneven, and SiC elutes from the SiC ceramic into the melt of the solvent metal (Cr). Indicates that

On the other hand, when looking at the interface between the inner surface of the carbon crucible (the square part of the inner wall: E portion) and the solvent metal, the shape of the inner surface of the crucible remains as it is, and the melt of solvent metal from the crucible remains. There is no trace of carbon leaching.
This experimental result shows that, under the above experimental conditions, the dissolution of carbon from the crucible into the solvent metal (Cr) melt is suppressed, and Si and C are prioritized from the SiC sintered body to the solvent metal melt. It is dissolved.

  That is, according to the method of producing a SiC single crystal by setting a SiC material and a solvent metal in a graphite crucible, it is possible to suppress elution of carbon from the crucible into the solvent metal melt. Si and C can be preferentially eluted into the melt from the material made of SiC contained in the crucible. Since SiC is preferentially eluted from the material composed of SiC into the solvent metal melt and carbon from the crucible is suppressed, Si and C in the melt are prevented during the single crystal growth process. Therefore, it is possible to produce a high-quality SiC single crystal.

  3, 4 and 5 show the results of analysis by EPMA (electron beam microanalyzer) on the sample surface shown in FIG. 2 (the central portion of the surface of the melted solidified portion). 3 shows the element distribution of C (carbon), FIG. 4 shows the element distribution of Cr (chromium), and FIG. 5 shows the element distribution of silicon (Si). 3, 4, and 5, it can be seen that the distribution of silicon and carbon is completely the same, and in the distribution region of silicon and carbon, the distribution of silicon and carbon is higher than that of chromium. This measurement result shows that SiC was formed by the melting operation. That is, in the form shown in FIG. 2, it is suggested that SiC is crystallized from the melt by immersing the SiC seed crystal in the solvent metal melt and a SiC single crystal is grown.

  As described above, using SiC material, placing the solvent metal on the material, melting the solvent metal, and contacting the seed crystal with the solvent metal melt to produce SiC single crystal from the seed crystal According to this method, it is possible to grow a SiC single crystal with almost no change in the composition ratio of Si and C in the melt. In the conventional solution method, C is eluted from the crucible into the melt. Therefore, the problem that the composition of the Si and C melt changes during the growth of the single crystal can be solved.

  Further, as shown in FIG. 2, the amount of the solvent metal disposed on the upper portion (upper surface) of the material is such that the upper surface of the material made of SiC is covered thinly by the melt of the solvent metal (the depth of the melt becomes shallow). ) Can increase the ratio of Si and C in the melt (the amount of Si and C dissolved with respect to the melt), making it easier for SiC to precipitate on the seed crystal, and the crystal growth rate. The SiC single crystal can be manufactured more efficiently.

  In the SiC single crystal manufacturing method of this embodiment, SiC is deposited on the seed crystal while maintaining a state in which a molten metal melt is always present above the material. Therefore, the material gradually elutes from the upper side into the solvent metal melt and shrinks in the height direction, and a SiC single crystal grows. That is, the amount of SiC material is reduced (the height of the material is reduced), and the SiC single crystal grows. As a solvent metal, by using a metal that is not taken into the SiC single crystal, or even if it is taken in, the amount taken up is very small, and the amount of evaporation during the growth process of the single crystal is small. A single crystal of SiC can be grown efficiently using the whole amount of material made of SiC while suppressing the amount.

In addition to materials provided as sintered bodies such as SiC ceramics, SiC powders, powdered SiC powders, etc., SiC single crystals can be used for the production of SiC single crystals. Parts that have not been used in products such as SiC polycrystals produced during the manufacturing process can also be used as materials.
Moreover, although the example which uses a graphite crucible as a container which accommodates a material and a solvent metal was shown in the said embodiment, it is also possible to use the crucible which consists of SiC as a container.

(Experimental example)
A SiC single crystal is grown by a method in which a material composed of an SiC sintered body is placed in a crucible and Cr is placed as a solvent metal on the crucible, and a SiC seed crystal is brought into contact with the melt while the solvent metal is melted. The experiment was conducted.
The crystal growth temperature was 1800 ° C., the growth time was 120 min, the rotation speed of the support shaft supporting the single crystal was 2.0 rpm, and the rotation speed around the crucible axis was −2.0 rpm. The crystal growth temperature is the temperature below the crucible 10 in FIG. 1 (the temperature of the support portion that supports the crucible). The temperature of the part to which the molten metal is supplied is higher than this, and is estimated to be about 1950 ° C. The support shaft for supporting the single crystal was made of a high-purity carbon material, and the crucible for supporting the shaft was rotated around the axis in opposite directions.

FIG. 6 shows a photograph (FIG. 6 (a)) of the end face of the support shaft lifted from the crucible after the experiment and a Raman spectrum (FIG. 6 (b)) of the end face. A disk-like SiC single crystal was used as a seed crystal. The part indicated by point-1 in the photo is the seed crystal part, and point-2 is the part where the crystal has grown.
In FIG. 6B, the spectrum of the SiC single crystal is shown as a reference spectrum. A sharp spectrum similar to that of a SiC single crystal is obtained at the seed crystal site (point-1). In addition, although the crystal growth site (point-2) is not sharp compared to the SiC single crystal, a peak corresponding to the SiC single crystal is seen, indicating that the SiC single crystal has grown.

  FIG. 7 shows a Raman spectrum (FIG. 7 (b)) of the upper part of the crucible on the side of the crucible after the experiment, a photograph just below the seed crystal (FIG. 7 (a)). Point-3 is the part where the seed crystal remains, and point-4 and point-5 are the parts where the crystal growth seems to have occurred. At point-3, a sharp peak equivalent to the Raman spectrum of SiC single crystal is observed. Sharp peaks are not seen at point-4 and point-5, but peaks corresponding to SiC single crystals are seen.

  In the method of growing a crystal by bringing a SiC single crystal into contact with a melt of a solvent metal melted on the material, it is difficult to control the positioning of the SiC single crystal accurately in contact with the surface of the melt. The above experimental results did not lead to the growth of a complete SiC single crystal because the positioning control was not always accurate, but it was partially in both the SiC seed crystal and the crucible. The result of crystal growth could be observed. That is, the possibility of growing a SiC single crystal by a method of bringing a SiC seed crystal into contact with a molten metal melt is shown.

(Second Embodiment)
FIG. 8 shows a second embodiment for producing a SiC single crystal by a solution method.
In the first embodiment described above, a SiC single crystal was manufactured by accommodating a material 20 made of SiC and a solvent metal 30 in a graphite crucible 10. In the present embodiment, a SiC single crystal is manufactured without using a crucible containing the material.

  As shown in FIG. 3, the SiC single crystal manufacturing apparatus of this embodiment includes a cylindrical resistance heating type carbon heater 12 and support means 16 disposed inside the carbon heater 12. The support means 16 includes an elevating mechanism that positions the elevating position of the seed crystal 14. The seed crystal 14 is attached to the lower end of the support means 16.

In the present embodiment, a solidified SiC body having shape retention is used as the material 20a for producing a SiC single crystal, and the solvent metal 30 is disposed on the top (upper surface) of the material 20a made of the solidified SiC body. Thus, a SiC single crystal is manufactured.
In the present embodiment, the material 20a is formed in a cylindrical shape having a flat upper surface, but the shape and size of the material 20a can be set as appropriate. What was made into arbitrary solid shapes, such as column shape and polygonal column shape, can be used.
As the solidified body of SiC, in addition to those formed as SiC sintered bodies such as SiC ceramics, those formed as having a certain shape retaining property by powder molding or the like can be used.

  The material 20a produces a SiC single crystal while disposing the solvent metal 30 on the upper portion (upper surface) and holding the melt of the solvent metal 30 on the upper portion. In order to support the melt of the solvent metal 30 on the upper surface of the material 20a, the material 20a holds the holding surface for holding the solvent metal 30 in a horizontal direction. Since the melt of the solvent metal 30 is supported on the upper surface of the material 20a by surface tension, the amount of the solvent metal 30 supplied to the upper portion (upper surface) of the material 20a is supplied in accordance with the amount that can be held on the upper surface of the material 20a. .

When growing the SiC single crystal, as shown in FIG. 8, the solvent metal 30 is melted by the carbon heater 12, and the support means 16 is moved up and down so that the seed crystal 14 contacts the surface of the melt of the solvent metal 30. Control the position.
At the interface between the material 20a and the melt of the solvent metal 30, Si and C are gradually eluted from the material 20a into the melt, and SiC is deposited on the seed crystal 13 to grow a SiC single crystal. The action of SiC eluting from the material 20a into the melt of the solvent metal 30 to grow a SiC single crystal is the same as in the first embodiment.

  In the present embodiment, since a SiC single crystal is manufactured using only the material 20a and the solvent metal 30 without using a container (crucible) for storing the material, the material 20a and the solvent are produced in the process of manufacturing the SiC single crystal. No material other than the metal 30 is mixed. That is, according to this method, it is possible to produce a SiC single crystal by eliminating the problem that excessive carbon is dissolved and mixed, such as the dissolution of carbon from the crucible into the melt. Since the composition ratio of Si and C in the melt of the solvent metal 30 does not change at all in the growth process of the SiC single crystal, it is possible to manufacture a high-quality SiC single crystal.

  In this embodiment, since the SiC single crystal is manufactured while holding the melt of the solvent metal 30 on the upper portion of the material 20a, the SiC single crystal is formed in accordance with the size of the SiC single crystal to be manufactured. It is necessary to prepare the material 20a.

  In each of the above embodiments, the carbon heater 12 is used as a means for heating the material and the solvent metal, but the means for heating the material and the solvent metal is not limited to the example using the carbon heater. For example, it is of course possible to use a high-frequency heating method using a high-frequency coil and a heating element. Also, methods can be used as appropriate for the structure of the heating furnace, temperature control in the SiC single crystal growth process, and the like.

10 Crucible 12 Carbon heater 14 Seed crystal 16 Support means 20, 20a Material 30 Solvent metal

Claims (5)

A method for producing a single crystal of SiC by a solution method using a material comprising SiC and using the material and a solvent metal,
Place and heat only the solvent metal on the material, position the solvent metal melt on top of the material,
The SiC seed crystal is brought into contact with the melt of the solvent metal, and Si and C are eluted from the material in the melt of the solvent metal, so that SiC is deposited on the seed crystal to grow a SiC single crystal. A method for producing a SiC single crystal, characterized by comprising:   The SiC single crystal according to claim 1, wherein a SiC single crystal is grown by disposing the SiC material on the bottom side of the crucible, disposing the solvent metal on the material and heating the material. Crystal production method.   The method for producing a SiC single crystal according to claim 2, wherein a crucible made of graphite is used as the crucible. As the material, using a solidified body made of block-shaped SiC,
The SiC single crystal is grown without using a crucible by placing and heating only the solvent metal on the material and holding the solvent metal melt on top of the material. The method for producing a SiC single crystal according to claim 1.   The method for producing a SiC single crystal according to any one of claims 1 to 4, wherein Cr is used as the solvent metal.