JP5847671B2 - Method for producing SiC single crystal - Google Patents

Description

  The present invention relates to a method for producing an SiC single crystal, and more particularly to a method for producing an SiC single crystal by a solution growth method.

  As a method for producing a SiC single crystal, there is a solution growth method. In the solution growth method, a SiC seed crystal made of a SiC single crystal is brought into contact with a Si—C solution. Here, the Si—C solution refers to a solution in which carbon (C) is dissolved in a melt of Si or Si alloy. Then, in the Si—C solution, the vicinity of the SiC seed crystal is brought into a supercooled state, and an SiC single crystal is grown on the surface of the SiC seed crystal.

  In order to improve the quality of the SiC single crystal, for example, it is conceivable to adjust the chemical composition of the Si—C solution.

For example, in the method for producing a silicon carbide single crystal described in Japanese Patent Application Laid-Open No. 2004-2173, a seed crystal substrate is immersed in an alloy melt to grow a single crystal on the seed crystal substrate. The melt contains Si, C, and Ti. The atomic ratio between Si and Ti is 0.1 ≦ x ≦ 0.25 when expressed as Si _1-x Ti _x . According to the said manufacturing method, the solubility of C improves. Therefore, a good quality silicon carbide bulk single crystal with few crystal defects can be stably manufactured at a practical growth temperature and growth rate.

  Moreover, in the manufacturing method of the SiC single crystal described in Japanese Patent Application Laid-Open No. 2005-82435, a Si melt added with 1 to 30 wt% of Ag is used. In this case, a SiC single crystal having a flat growth surface can be grown.

  Moreover, in the growth method of the silicon carbide single crystal described in International Publication No. 2009/69564, a Si—Cr—Ni—C melt is used. The content of Cr is 30 to 70 at%. The Ni content is 1 to 25 at%. According to the above growth method, the morphology of the surface of the silicon carbide single crystal is improved and polycrystallization is suppressed.

JP 2004-2173 A JP 2005-82435 A International Publication No. 2009/69564

  However, in recent years, it has been required to further improve the quality of SiC single crystals.

  The objective of this invention is providing the manufacturing method of a SiC single crystal which can improve the quality of a SiC single crystal.

A method for producing a SiC single crystal according to an embodiment of the present invention is a method for producing a SiC single crystal by a solution growth method. The manufacturing method includes a step of preparing a crucible in which a raw material of the Si—C solution is accommodated, a step of melting the raw material in the crucible by heating to produce a Si—C solution, and a SiC seed crystal in the Si—C solution. And a step of growing a SiC single crystal. The Si—C solution contains C and Si and Ti satisfying the formula (1), and at least one or two or more selected from the group consisting of Ni, Ag and Cu are removed from C. %, More than 1% and not more than 20%.
0.11 ≦ Ti / Si ≦ 0.33 (1)
For each element symbol in formula (1), the content of the corresponding element (at% excluding C) is substituted.

  The SiC single crystal manufacturing method according to the embodiment of the present invention can improve the quality of the SiC single crystal.

FIG. 1 is a schematic diagram of a manufacturing apparatus used in a method for manufacturing a SiC single crystal according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

  The manufacturing method of the SiC single crystal according to the embodiment of the present invention is based on the solution growth method. The manufacturing method includes a preparation process, a generation process, and a growth process. In the preparation process, a manufacturing apparatus is prepared. In the generation step, an Si—C solution is generated. In the growth step, the SiC seed crystal is brought into contact with the Si—C solution to grow a SiC single crystal. Hereinafter, details of each process will be described.

[Preparation process]
In the preparation step, a manufacturing apparatus used for the solution growth method is prepared. FIG. 1 is a schematic diagram of a manufacturing apparatus 10 used in a method for manufacturing a SiC single crystal according to an embodiment of the present invention. A manufacturing apparatus 10 shown in FIG. 1 is an example of a manufacturing apparatus used for the solution growth method. Therefore, the manufacturing apparatus used for the solution growth method is not limited to the manufacturing apparatus 10 shown in FIG.

  The manufacturing apparatus 10 includes a chamber 12, a crucible 14, a heat insulating member 16, a heating device 18, a rotating device 20, and a lifting device 22.

  The chamber 12 accommodates the crucible 14. When manufacturing a SiC single crystal, the chamber 12 is cooled.

  The crucible 14 accommodates the raw material of the Si—C solution 15. Preferably, the crucible 14 contains carbon. In this case, the crucible 14 becomes a carbon supply source to the Si—C solution 15.

  The heat insulating member 16 is made of a heat insulating material and surrounds the crucible 14.

  The heating device 18 is a high frequency coil, for example, and surrounds the side wall of the heat insulating member 16. The heating device 18 induction-heats the crucible 14 to generate the Si—C solution 15. The heating device 18 further maintains the Si—C solution 15 at the crystal growth temperature. The crystal growth temperature is the temperature of the Si—C solution 15 when an SiC single crystal is grown. Crystal growth temperature is 1600-2000 degreeC, for example, Preferably, it is 1900-2000 degreeC.

  The rotating device 20 includes a rotating shaft 24 and a drive source 26.

  The rotating shaft 24 extends in the height direction of the chamber 12 (up and down direction in FIG. 1). The upper end of the rotating shaft 24 is located in the heat insulating member 16. A crucible 14 is disposed at the upper end of the rotating shaft 24. The lower end of the rotation shaft 24 is located outside the chamber 12.

  The drive source 26 is disposed below the chamber 12. The drive source 26 is connected to the rotation shaft 24. The drive source 26 rotates the rotation shaft 24 around the central axis of the rotation shaft 24.

  The lifting device 22 includes a seed shaft 28 and a drive source 30.

  The seed shaft 28 extends in the height direction of the chamber 12. The upper end of the seed shaft 28 is located outside the chamber 12. A SiC seed crystal 32 is attached to the lower end surface of the seed shaft 28.

  The drive source 30 is disposed above the chamber 12. The drive source 30 is connected to the seed shaft 28. The drive source 30 moves the seed shaft 28 up and down. The drive source 30 rotates the seed shaft 28 around the central axis of the seed shaft 28.

  In the preparation step, an SiC seed crystal 32 is further prepared. The SiC seed crystal 32 is made of a SiC single crystal. Preferably, the crystal structure of SiC seed crystal 32 is the same as the crystal structure of the SiC single crystal to be manufactured. For example, when producing a 4H polymorphic SiC single crystal, a 4H polymorphic SiC seed crystal 32 is used. When the 4H polymorphic SiC seed crystal 32 is used, the crystal growth plane is the (0001) plane or (000-1) plane, or 8 ° or less from the (0001) plane or (000-1) plane. The surface is preferably inclined at an angle. In this case, the SiC single crystal grows stably.

  When the manufacturing apparatus 10 and the SiC seed crystal 32 are prepared, the SiC seed crystal 32 is attached to the lower end surface of the seed shaft 28.

  Next, the crucible 14 is disposed on the rotating shaft 24 in the chamber 12. At this time, the crucible 14 contains the raw material of the Si—C solution 15.

[Generation process]
Next, the Si—C solution 15 is generated. First, the chamber 12 is filled with an inert gas. And the raw material of the Si-C solution 15 in the crucible 14 is heated with the heating apparatus 18 more than melting | fusing point. When the crucible 14 is made of graphite, when the crucible 14 is heated, carbon dissolves in the melt from the crucible 14 and an Si—C solution 15 is generated. When the carbon in the crucible 14 dissolves in the Si—C solution 15, the carbon concentration in the Si—C solution 15 approaches the saturation concentration. The chemical composition of the Si—C solution 15 will be described later.

[Growth process]
Next, the seed shaft 28 is lowered by the drive source 30 to bring the SiC seed crystal 32 into contact with the Si—C solution 15. At this time, the SiC seed crystal 32 may be immersed in the Si—C solution 15.

  After bringing the SiC seed crystal 32 into contact with the Si—C solution 15, the Si—C solution 15 is maintained at the crystal growth temperature by the heating device 18. Furthermore, the vicinity of the SiC seed crystal 32 in the Si—C solution 15 is supercooled to bring SiC into a supersaturated state.

  The method for supercooling the vicinity of the SiC seed crystal 32 in the Si—C solution 15 is not particularly limited. For example, the heating device 18 is controlled so that the temperature in the region near the SiC seed crystal 32 in the Si—C solution 15 is lower than the temperature in other regions. Further, the vicinity of the SiC seed crystal 32 in the Si—C solution 15 may be cooled by a refrigerant. Specifically, the refrigerant is circulated inside the seed shaft 28. The refrigerant is, for example, an inert gas such as helium (He) or argon (Ar). If the coolant is circulated in the seed shaft 28, the SiC seed crystal 32 is cooled. When the SiC seed crystal 32 is cooled, the vicinity of the SiC seed crystal 32 in the Si-C solution 15 is also cooled.

  The SiC seed crystal 32 and the Si-C solution 15 (the crucible 14) are rotated while SiC in the region near the SiC seed crystal 32 in the Si-C solution 15 is in a supersaturated state. By rotating the seed shaft 28, the SiC seed crystal 32 rotates. By rotating the rotating shaft 24, the crucible 14 rotates. The rotation direction of the SiC seed crystal 32 may be opposite to the rotation direction of the crucible 14 or the same direction. Further, the rotation speed may be constant or may vary. The seed shaft 28 gradually rises while rotating. At this time, a SiC single crystal is generated and grown on the crystal growth surface of the SiC seed crystal 32 immersed in the Si—C solution 15. The seed shaft 28 may rotate without being raised. Further, the seed shaft 28 may not be raised or rotated.

[Chemical composition of Si-C solution]
The chemical composition of the Si—C solution 15 used in the manufacturing method will be described. The Si-C solution 15 contains C and Si and Ti satisfying the formula (1), and further, one or more selected from the group consisting of Ni, Ag, and Cu is excluded from C. At%, more than 1% and not more than 20%.
0.11 ≦ Ti / Si ≦ 0.33 (1)
For each element symbol in formula (1), the content of the corresponding element (at% excluding C) is substituted.
Here, “at% excluding C” means at% in the remaining chemical composition excluding C in the chemical composition of the Si—C solution 15.

  In the method for producing a SiC single crystal according to the present embodiment, when the Si—C solution to be used satisfies the formula (1), the solubility of C is improved and the SiC single crystal is easily generated. Furthermore, the quality of a SiC single crystal can be improved by containing 1 type, or 2 or more types selected from the group which consists of Ni, Ag, and Cu within the above-mentioned range in a Si-C solution. Hereinafter, these points will be described in detail.

[Regarding Formula (1)]
When satisfy | filling Formula (1), the solubility of C improves. When Ti / Si is smaller than the lower limit of formula (1), the solubility of C decreases. When Ti / Si is larger than the upper limit of the formula (1), a Ti-containing layer (for example, TiC) is easily formed on the SiC seed crystal 32. As a result, there is a high possibility that the growth of the SiC single crystal is inhibited. Therefore, Ti / Si satisfies the formula (1).

[About Ni, Ag and Cu]
By satisfy | filling Formula (1), the solubility of C of the Si-C solution 15 can be raised, and the SiC solute can be increased in the Si-C solution 15. Here, the SiC solute is a combination of Si and C (for example, SiC). However, as the SiC solute increases, the SiC solute tends to aggregate.

  When the SiC solute aggregates, for example, a SiC dimer is generated. In addition, SiC dimers may agglomerate. When the SiC dimer aggregates, the size of the SiC solute increases.

  As the size of the SiC solute increases, the quality of the SiC single crystal decreases. This point will be described below.

  The SiC single crystal undergoes step flow growth. In step flow growth, step bunching occurs when growth in the upper step catches up with growth in the lower step. As the step bunching proceeds, inclusion occurs due to incorporation of the Si—C solution or the like. As a result, the quality of the produced SiC single crystal is lowered. Therefore, in order to improve the quality of the SiC single crystal, it is necessary to suppress step bunching.

  Here, when the size of the SiC solute is large, the SiC solute is easily supplied from the terrace of the upper step to the terrace of the lower step. Therefore, the growth of the upper step can easily catch up with the growth of the lower step. As a result, step bunching is likely to occur.

  On the other hand, when the size of the SiC solute is small, it is difficult to supply the SiC solute from the upper step terrace to the lower step terrace. Therefore, it becomes difficult for the growth of the upper step to catch up with the growth of the lower step. As a result, step bunching is suppressed.

  Therefore, in order to suppress step bunching and improve the quality of the SiC single crystal, it is effective to reduce the size of the SiC solute.

  Here, the Si-C solution 15 is one or two or more selected from the group consisting of Ni, Ag and Cu, at% excluding C, in a range of more than 1% and less than 20%. Contained within. When two or more elements are contained, the total amount may be within the above range.

  Ni, Ag and Cu all have low affinity with C. Therefore, when these elements are present in the Si—C solution, bonds between carbons are weakened in the aggregated SiC solute. Therefore, the aggregation of the SiC solute is dissolved (for example, the aggregation of the SiC dimer is dissolved), and the size of the SiC solute is reduced. As a result, step bunching is suppressed and the quality of the SiC single crystal is improved.

  If the total content is too small, the above effect cannot be obtained effectively. On the other hand, if the total content is too high, TiC is likely to be generated. As a result, the SiC single crystal is difficult to grow and the quality of the SiC single crystal is lowered.

  If the content of one or more selected from the group consisting of Ni, Ag and Cu is within the above range, step bunching can be suppressed and the quality of the SiC single crystal can be improved.

  Si—C solutions having various chemical compositions were produced, and SiC single crystals were produced from the respective Si—C solutions. And the quality of the manufactured SiC single crystal was evaluated.

[Test method]
The remaining chemical composition excluding C was a Si-C solution having the chemical composition shown in Table 1.

  The chemical composition of the Si—C solutions of Examples 1 to 4 (remaining chemical composition excluding C) was within the scope of the present invention. The chemical composition of the Si—C solutions of Comparative Examples 1 and 2 (the remaining chemical composition excluding C) was outside the scope of the present invention.

  A SiC single crystal was manufactured using the Si-C solution described above. The crystal structure of the SiC seed crystal was 4H polymorph. The crystal growth surface of the SiC seed crystal was the (000-1) plane, that is, the C plane. The crystal growth temperature was the temperature shown in Table 1, and was almost the same temperature.

[Evaluation method]
If the surface of the manufactured SiC single crystal is observed at a magnification of 50 times using an optical microscope, and if there is no macroscopic surface step or inclusion intrusion due to step bunching, step bunching is It was determined that the quality of the SiC single crystal was improved. In addition, when the surface of the SiC single crystal could not be observed visually, it was determined that the quality of the SiC single crystal was not improved.

  The chemical composition (remaining chemical composition excluding C) of the Si-C solutions of Examples 1 to 4 was appropriate. Therefore, the quality of the SiC single crystal was high. This is thought to be because step bunching was suppressed because Ni, Ag and Cu weakened the bond between carbons in the SiC solute and the size of the SiC solute was reduced.

  On the other hand, when the Si—C solutions of Comparative Examples 1 and 2 were used, the quality of the SiC single crystal was not improved. In the raw material of Comparative Example 1, the Ni content was too small. Therefore, the quality of the SiC single crystal was low. On the other hand, in the raw material of Comparative Example 2, the Ni content was too high. Therefore, the SiC single crystal did not grow and the surface of the SiC single crystal could not be observed.

  As mentioned above, although embodiment of this invention has been explained in full detail, these are illustrations to the last and this invention is not limited at all by the above-mentioned embodiment.

10: manufacturing apparatus, 14: crucible, 15: Si-C solution, 32: SiC seed crystal

Claims (1)

A manufacturing method for manufacturing a SiC single crystal by a solution growth method,
Preparing a crucible in which a raw material of the Si-C solution is stored;
Melting the raw material in the crucible by heating to produce the Si-C solution;
Bringing the SiC seed crystal into contact with the Si-C solution and growing a SiC single crystal,
The Si-C solution is
C
Containing Si and Ti satisfying the formula (1) , and
One or more selected from the group consisting of A g and Cu, in at% except for the C, more than 1%, and contains 20% or less, the manufacturing method of the SiC single crystal.
0.11 ≦ Ti / Si ≦ 0.33 (1)
For each element symbol in formula (1), the content of the corresponding element (at% excluding C) is substituted.

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