KR102089460B1 - Manufacturing method for silicon carbide single crystal - Google Patents

Abstract

A method of manufacturing a silicon carbide single crystal according to an embodiment of the present invention comprises the steps of forming a silicon-based melt by mixing a silicon raw material having a first average diameter, and a metal additive raw material having a second average diameter, and species in the silicon-based melt. Contacting crystals to obtain a silicon carbide single crystal, wherein the first average diameter is from about 5 mm to about 60 mm, and the second average diameter is from about 1 mm to about 40 mm.

Description

Manufacturing method of silicon carbide single crystal {MANUFACTURING METHOD FOR SILICON CARBIDE SINGLE CRYSTAL}

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

The power semiconductor device is a core device in a next generation system that uses electrical energy such as an electric vehicle, a power system, and high-frequency mobile communication. For this, it is necessary to select materials suitable for high voltage, high current, and high frequency. Silicon single crystals have been used as power semiconductor materials, but due to physical limitations, silicon carbide single crystals that can be driven in a more extreme environment with less energy loss are attracting attention.

For growth of silicon carbide single crystal, for example, silicon carbide is used as a raw material to sublimate at a high temperature of 2000 ° C or higher (sublimation) to grow a single crystal, a solution growth method using a crystal pulling method, and a chemical using a gas source A vapor deposition method or the like is used.

However, if the chemical vapor deposition method is used, it can be grown only to the level of a thin film with a limited thickness, and when the sublimation method is used, defects such as micro pipes and lamination defects are likely to occur, thereby limiting production cost. Accordingly, research is being conducted on a solution growth method that is known to have a lower crystal growth temperature than a sublimation method and is advantageous for large diameter curing and high quality.

The present invention is to provide a method for producing a silicon carbide single crystal capable of obtaining a silicon carbide single crystal of excellent quality.

In addition, the technical problem to be solved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned are clearly understood by those skilled in the art from the following description. Will be understandable.

A method of manufacturing a silicon carbide single crystal according to an embodiment of the present invention comprises the steps of forming a silicon-based melt by mixing a silicon raw material having a first average diameter, and a metal additive raw material having a second average diameter, and species in the silicon-based melt. Contacting crystals to obtain a silicon carbide single crystal, wherein the first average diameter is from about 5 mm to about 60 mm, and the second average diameter is from about 1 mm to about 40 mm.

The first average diameter may be from about 10 mm to about 55 mm.

The second average diameter may be from about 1 mm to about 35 mm.

The volume of pores included in the obtained silicon carbide single crystal may be about 15% or less.

The silicon raw material and the metal additive raw material may further include charging in a crucible, and the initial filling rate of the silicon raw material and the metal additive raw material charged in the crucible may be about 35% or more.

The at% ratio of the silicon raw material and the metal additive raw material may be about 3: 7 to about 7: 3.

The crucible is a graphite material, and may further include dissolving carbon in the silicon-based melt.

It may include a silicon carbide single crystal prepared by the above-described method.

The volume of pores formed in the silicon carbide single crystal may be about 15% or less.

According to the above embodiment, the obtained silicon carbide single crystal may not contain bubbles and may have excellent quality.

1 is a cross-sectional view of an apparatus for manufacturing a silicon carbide single crystal according to an embodiment.
2 is a cross-sectional image of a coagulation product according to Example 1, FIG. 3 is a cross-sectional image of a coagulation product according to Example 2, and FIG. 4 is a cross-sectional image of a coagulation product according to Comparative Example 1.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in the description of the present description, descriptions of already known functions or configurations will be omitted for clarity.

Hereinafter, a method of obtaining a silicon carbide single crystal using the silicon carbide single crystal manufacturing apparatus shown in FIG. 1 will be described.

First, a silicon raw material and a metal additive raw material are prepared. The metal additive raw material may be any metal for improving the solubility of carbon in a silicon-based melt. The silicon raw material and the metal additive raw material may be provided in required equivalents, for example, at% may be provided to have a ratio of about 3: 7 to 7: 3.

The silicon raw material according to an embodiment may have a first average diameter. The first average diameter may be about 5 mm to about 60 mm, preferably about 10 mm to about 55 mm. In addition, the metal additive raw material according to an embodiment may have a second average diameter. The second average diameter may be about 1 mm to about 40 mm, preferably about 1 mm to about 35 mm.

In the process of depositing a silicon carbide single crystal by contacting a silicon carbide seed crystal with an existing melt, there is a problem that bubble defects are formed inside the silicon carbide single crystal. Bubble defects appear to be formed by bubbles remaining in the melt during the process of charging the initial raw material or by the atmospheric gas located between the silicon carbide seed crystal and the contact surface of the melt.

However, according to one embodiment, by controlling the average diameter (particle size) of the initial raw material to the above-described numerical range, it is possible to reduce the bubbles caused by the space formed in the initial raw material state, thereby reducing the bubbles remaining inside the melt.

Specifically, each of the silicon raw material and the metal additive raw material may have an amorphous powder or a lump form. When the initial raw material having this form is charged in a crucible, an empty space is formed between the powder or the lump. As the crucible is heated, some of the empty space remains inside the melt without being able to escape to the outside.

In particular, when the average diameter of the initial raw material is smaller than the above-described numerical range, the number of spaces formed between the initial raw materials is large, and accordingly, the amount of air bubbles remaining in the melt may be increased. Therefore, the silicon carbide single crystal may cause a problem including a significant amount of bubble defects.

In addition, if the average diameter of the initial raw material is larger than the above-described numerical range, the space formed between the initial raw materials may be small, but the initial filling rate in the crucible may not be good. According to this, the manufacturing cost may increase or the process time required to obtain the same amount may increase.

However, according to an embodiment of the present invention, by reducing the bubbles formed therein even after the initial raw materials charged to the crucible are formed of a melt while having a predetermined filling rate, it is possible to provide a silicon carbide single crystal of improved quality.

Thereafter, the initial raw material described above is introduced into the crucible 300. The initial raw material input to the crucible 300 may occupy about 35% or more of the inner volume of the crucible 300. That is, the filling rate of the initial raw material may be about 35% or more.

The crucible 300 on which the initial raw material is mounted is heated using a heating member 400 in an inert atmosphere such as argon gas. Upon heating, the initial molten raw material in the crucible 300 changes to a silicon-based melt. In addition, according to an example, when the crucible 300 is a graphite material, carbon may be eluted from the crucible 300.

After the crucible 300 reaches a predetermined temperature, the temperature of the melt in the crucible 300 gradually decreases, and the solubility of carbon in the melt decreases. For this reason, when the silicon carbide becomes supersaturated near the seed crystal 210, a silicon carbide single crystal grows on the seed crystal 210 using the supersaturation degree as a driving force.

As the silicon carbide single crystal grows, the conditions for depositing silicon carbide from the melt may change. At this time, silicon and carbon may be added to match the composition of the melt over time to maintain the melt in a composition within a certain range. The silicon and carbon to be added can be added continuously or discontinuously.

The silicon carbide single crystal precipitated through the manufacturing process may include less bubble defects, and specifically, the volume of the bubble defects may be about 15% or less of the total volume occupied by the silicon carbide single crystal.

Hereinafter, a manufacturing apparatus used in a method for manufacturing a silicon carbide single crystal will be briefly described with reference to FIG. 1.

Referring to FIG. 1, a silicon carbide single crystal manufacturing apparatus according to an embodiment includes a reaction chamber 100, a crucible 300 positioned inside the reaction chamber 100, and a seed crystal 210 extending into the crucible 300 , It may include a heating member 400 for heating the seed crystal support 230 and the moving member 250 and the crucible 300.

The reaction chamber 100 is a closed shape including an empty interior space, and the interior of the reaction chamber 100 may be maintained in an atmosphere such as a constant pressure. Although not shown, a vacuum pump and a gas tank for controlling the atmosphere may be connected to the reaction chamber 100. After the inside of the reaction chamber 100 is vacuumed using a vacuum pump and a gas tank for controlling the atmosphere, an inert gas such as argon gas may be filled.

The silicon carbide seed crystal 210 may be located inside the crucible 300 by being connected to the seed crystal support 230 and the moving member 250, which will be described later, and may be arranged to contact the melt provided in the crucible 300. You can.

According to an embodiment, a meniscus may be formed between the surface of the silicon carbide seed crystal 210 and the melt. The meniscus refers to a curved surface formed on the melt by the surface tension generated when the lower surface of the silicon carbide seed crystal 210 is slightly lifted after contact with the melt. When a silicon carbide single crystal is grown by forming a meniscus, generation of polycrystals can be suppressed to obtain a higher quality single crystal.

The silicon carbide seed crystal 210 is made of a silicon carbide single crystal. The crystal structure of the silicon carbide seed crystal 210 is the same as that of the silicon carbide single crystal to be manufactured. For example, when manufacturing a 4H polycrystalline silicon carbide single crystal, the 4H polycrystalline silicon carbide seed crystal 210 may be used. When using the 4H polycrystalline silicon carbide seed crystal 210, the crystal growth plane is a (0001) plane or a (000-1) plane, or an angle of 8 degrees or less from the (0001) plane or (000-1) plane. It can be a photo side.

The seed crystal support 230 connects the silicon carbide seed crystal 210 and the moving member 250. One end of the seed crystal support 230 may be connected to the moving member 250 and the other end may be connected to the seed crystal 210.

The seed crystal support 230 may be made of a material that is a conductor, and for example, may be made of graphite, silicon carbide, or a metal alloy material.

The seed crystal support 230 is connected to the moving member 250 and can move in the vertical direction along the height direction of the crucible 300. Specifically, the seed crystal support 230 may be moved inside the crucible 300 for the growth process of the silicon carbide single crystal, or may be moved outside the crucible 300 after the growth process of the silicon carbide single crystal is finished. In addition, this specification has described an embodiment in which the seed crystal support 230 moves in the vertical direction, but is not limited thereto, and may move or rotate in any direction, and may include known means for this.

The crucible 300 is provided inside the reaction chamber 100 and may be in the form of an open container on the upper side, and may include an outer circumferential surface 300a and a lower surface 300b excluding the upper surface. Of course, the crucible 300 may be any shape for forming a silicon carbide single crystal without limitation to the above-described shape. The crucible 300 may be accommodated by charging a molten raw material such as silicon or silicon carbide powder.

The crucible 300 may be a material containing carbon, such as graphite or silicon carbide, and the crucible 300 itself may be used as a source of carbon raw materials. Alternatively, it is not limited thereto, and a crucible made of ceramic may be used, and at this time, a material or a source for providing carbon may be separately provided.

 The heating member 400 may heat the crucible 300 to melt or heat the material accommodated in the crucible 300.

The heating member 400 may use a resistance heating means or an induction heating means. Specifically, the heating member 400 itself may be formed of a resistance type that generates heat, or the heating member 400 may be formed of an induction coil and may be formed by an induction heating method of heating the crucible 300 by flowing a high-frequency current through the induction coil. . However, it is needless to say that any heating member may be used without being limited to the above-described method.

The silicon carbide manufacturing apparatus according to an embodiment may further include a rotating member 500. The rotating member 500 is coupled to the lower surface of the crucible 300 to rotate the crucible 300. High-quality silicon carbide single crystals can be grown on the silicon carbide seed crystal 210 as it is possible to provide a melt having a uniform composition through rotation of the crucible 300.

Hereinafter, Examples 1 and 2 and Comparative Example 1 will be described with reference to Table 1 and FIGS. 2 to 4.

Example 1 Example 2 Comparative Example 1 First average diameter of silicon raw material 20 mm 50 mm 2 mm 2nd average diameter of metal additive 5 mm 30 mm 1 mm At% ratio of silicon raw material and metal additive raw material 6: 4 6: 4 6: 4 Internal crucible filling rate 50% 40% 55% Air bubble area ratio 10% 8% 40%

Referring to Table 1, according to Examples 1 and 2, the first average diameter of the silicon raw material included in the initial raw material is about 20 to 50 mm, and the second average diameter of the metal additive raw material is about 5 to 30 mm. The first average diameter of the silicon raw material according to Comparative Example 1 is about 2 mm, and the second average diameter of the metal additive raw material is about 1 mm. In each of Example 1, Example 2, and Comparative Example 1, the silicon raw material and the metal additive raw material were mixed in an at% ratio of 6: 4.

As a result of loading each initial raw material according to Example 1, Example 2, and Comparative Example 1 in a crucible, Examples 1 and 2 showed an internal filling rate of about 40 to 50%, and Comparative Example 1 of about 55%. The internal filling rate was shown.

Next, Example 1, Example 2, and Comparative Example 1 were melted in a crucible, and silicon carbide single crystals were obtained, and then bubble defects formed therein through the coagulum remaining in the crucible were examined.

2 and 3, respectively, it was confirmed that the cross-section of the coagulated product according to Example 1 and Example 2 had some bubbles (indicated in black) between the silicon carbide crystals. As shown in Table 1, it was confirmed that the area occupied by the bubbles in the cross section of the coagulated product according to Example 1 was about 10%. In addition, it was confirmed that the area occupied by the bubbles in the cross-section of the coagulum according to Example 2 was about 8%.

On the other hand, referring to Figure 4, it was confirmed that the cross-section of the coagulated product according to Comparative Example 1 is almost half a bubble. Specifically, it was confirmed that the area occupied by the bubbles in the cross-sectional image was about 40%.

In the case of Examples 1 and 2, since the average diameter was large, it was confirmed that the number of spaces formed between the initial raw materials may be small, and accordingly, the number of bubbles contained in the coagulated material remaining in the melt or finally left may be small. . However, in Comparative Example 1, since the average diameter of the initial raw materials is small, the number of spaces formed between the initial raw materials may be relatively large. Therefore, it was confirmed that the number of bubbles contained in the solidified product remaining in the melt or finally left may be large.

In summary, it was confirmed that the silicon raw material and the metal additive raw material according to the embodiment satisfy a predetermined initial filling rate when charged in a crucible, but have fewer bubbles.

In the foregoing, although specific embodiments of the present invention have been described and illustrated, the present invention is not limited to the described embodiments, and it is common knowledge in the field of this technology that various modifications and modifications can be made without departing from the spirit and scope of the present invention. It is obvious to those who have it. Therefore, such modifications or variations should not be individually understood from the technical spirit or viewpoint of the present invention, and the modified embodiments should belong to the claims of the present invention.

100: chamber
210: seed crystal
300: crucible
400: heating member
500: rotating member

Claims (9)

Forming a silicon-based melt by mixing a silicon raw material having a first average diameter and a metal additive raw material having a second average diameter, and
And contacting the seed crystal with the silicon-based melt to obtain a silicon carbide single crystal,
The first average diameter is 5mm to 60mm, the second average diameter is 1mm to 40mm method of manufacturing a silicon carbide single crystal. In claim 1,
The first average diameter of 10 mm to 55 mm silicon carbide single crystal production method. In claim 1,
The second average diameter of 1mm to 35mm silicon carbide single crystal manufacturing method. In claim 1,
The volume of pores included in the obtained silicon carbide single crystal is 15% or less. In claim 1,
The silicon raw material and the metal additive raw material further includes charging in a crucible,
The method of manufacturing a silicon carbide single crystal having an initial filling rate of the silicon raw material and the metal additive raw material charged in the crucible is 35% or more. In claim 1,
The method of manufacturing a silicon carbide single crystal in which the at% ratio of the silicon raw material and the metal additive raw material is 3: 7 to 7: 3. In claim 5,
The crucible is a graphite material,
The method of manufacturing a silicon carbide single crystal further comprising the step of eluting carbon in the silicon-based melt. A silicon carbide single crystal made of any one of claims 1 to 7,
The volume of pores formed in the silicon carbide single crystal is 15% or less silicon carbide single crystal. delete

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