CN113122930A

CN113122930A - Expandable crucible for heat treatment of silicon carbide powder

Info

Publication number: CN113122930A
Application number: CN202010294353.2A
Authority: CN
Inventors: 张炳圭; 朴钟辉; 梁殷寿; 崔正宇; 高上基; 具甲烈; 金政圭
Original assignee: SKC Co Ltd
Current assignee: Sanik Co.
Priority date: 2020-01-15
Filing date: 2020-04-15
Publication date: 2021-07-16
Also published as: KR20210091885A; KR102367710B1

Abstract

本发明实例的坩埚可扩大内部直径，从而，当进行碳化硅粉末的热处理时，不会发生因膨胀及收缩导致的坩埚的损伤。因此，利用上述坩埚来获取碳化硅粉末的烧结体，基于此，可使单晶碳化硅锭生长，由此可提高工序的有效性。The crucible of the example of the present invention can be enlarged in inner diameter, so that damage to the crucible due to expansion and contraction does not occur when heat treatment of silicon carbide powder is performed. Therefore, by using the above-described crucible to obtain a sintered body of silicon carbide powder, a single crystal silicon carbide ingot can be grown based on this, thereby improving the efficiency of the process.

Description

Expandable crucible for heat treatment of silicon carbide powder

Technical Field

Examples of the present invention relate to a crucible for heat treatment of silicon carbide powder and a method for producing a silicon carbide single crystal ingot. And more particularly, to a heat treatment method of silicon carbide powder as a raw material for producing a silicon carbide single crystal ingot, a crucible for the same, and a method of producing a silicon carbide single crystal ingot using the heat-treated silicon carbide powder as a raw material.

Background

Silicon carbide (SiC), silicon (Si), gallium nitride (GaN), aluminum oxide (Al)₂O₃) Single crystals (single crystals) such as gallium arsenide (GaAs) and aluminum nitride (AlN) exhibit characteristics that cannot be exhibited by polycrystalline crystals (polycrystals), and thus, the demand in the industrial field is increasing day by day.

In particular, single crystal silicon carbide (SiC) has an advantage that an energy band gap (energy band gap) is large, and a maximum breakdown voltage (breakdown voltage) and a thermal conductivity (thermal conductivity) are more excellent than those of silicon (Si). In addition, single crystal silicon carbide has the same carrier mobility as silicon, and has a high saturation floating rate of electrons and a high internal pressure. Due to such characteristics, single crystal silicon carbide is suitable for semiconductor devices requiring high efficiency, high internal pressure, and large capacity.

As a method for producing such a single crystal, for example, japanese laid-open patent publication No. 2001-114599 discloses that a single crystal ingot is grown on a seed crystal by heating the seed crystal in a vacuum vessel (heating furnace) into which argon gas is introduced by a heater and sublimating the raw material powder by maintaining the temperature of the seed crystal at a temperature 10 to 100 ℃ lower than the temperature of the raw material powder.

Recently, in the case of growing the single crystal ingot, in order to prevent defects caused by scattering of the silicon carbide powder as a raw material, it is preferable to perform a step of improving the bonding force between particles by heat-treating the silicon carbide powder in advance, and then improving the growth rate and quality of the grown single crystal ingot using the silicon carbide powder as a raw material.

Disclosure of Invention

Referring to fig. 7, as a pretreatment of silicon carbide powder for preparing a silicon carbide single crystal ingot, silicon carbide powder 210 is put in a crucible 400 and heat treatment is performed under high temperature conditions, during which the crucible 400 is expanded by heat, and the silicon carbide powder will also expand and form a sintered body 220. However, during the subsequent cooling process, the crucible will exhibit a tendency to shrink, and on the contrary, the silicon carbide powder forms the sintered body 220 mass without being shrunk, and therefore, a greater stress is applied to the crucible 400, and as a result, there is a problem that the crucible develops cracks 410. Even if no crack occurs during the cooling process, the possibility of a crack occurring in the crucible during the subsequent growth of the single crystal ingot is extremely high due to the residual stress.

Accordingly, an object of an example of the present invention is to provide a crucible that is free from damage due to expansion and contraction when silicon carbide powder is heat-treated. An object of an embodiment of the present invention is to provide a method for heat-treating a silicon carbide powder using the crucible and a method for producing a single crystal silicon carbide ingot.

According to an embodiment, the crucible includes a first reaction vessel and a second reaction vessel, the first reaction vessel is disposed in the second reaction vessel, and the crucible has a structure in which the inner diameter of the first reaction vessel can be enlarged.

According to still another embodiment, the present invention provides a heat treatment method of silicon carbide powder, including: charging silicon carbide powder into a first reaction vessel disposed inside a second reaction vessel; and a step of heat-treating the silicon carbide powder, wherein the inner diameter of the first reaction vessel is enlarged when the heat treatment is performed.

According to another embodiment, the present invention provides a method for producing a silicon carbide single crystal ingot, the method comprising: charging silicon carbide powder into a first reaction vessel disposed inside a second reaction vessel; obtaining a sintered body of silicon carbide powder by heat-treating the silicon carbide powder; and growing a silicon carbide single crystal ingot in a seed crystal from the sintered body of the silicon carbide powder, wherein the inner diameter of the first reaction vessel is enlarged when the heat treatment is performed.

The crucible of the above example can have an enlarged inner diameter, so that when the heat treatment of the silicon carbide powder is performed, damage of the crucible due to expansion and contraction does not occur. According to a preferred embodiment, the crucible can be contracted as necessary after the inner diameter is enlarged, and thus can be easily reused. Therefore, by obtaining a sintered body of silicon carbide powder using the crucible, a single crystal silicon carbide ingot can be grown, and the process efficiency can be improved.

Drawings

Fig. 1 is a sectional view showing (a) and (b) before and after heat treatment of a crucible of an example.

Fig. 2 is a perspective view of a first reaction vessel showing a crucible of an example.

Fig. 3 is a plan view showing various division methods of the first reaction vessel.

Fig. 4 is a sectional view showing (a) and (b) before and after heat treatment of a crucible of still another example.

Fig. 5 is a sectional view showing a first reaction vessel of another example.

Fig. 6 shows a method for producing an example of a silicon carbide single crystal ingot.

FIG. 7 illustrates a prior art method of heat treating silicon carbide powder.

Description of reference numerals

110: a first reaction vessel

111: cut noodles

120: second reaction vessel

130: (insertion type) plate

140: (support type) Flat Panel

210: silicon carbide powder (before heat treatment)

220: sintered body of silicon carbide powder (after heat treatment)

310: body of the third reaction vessel

320: cover of third reaction vessel

321: seed crystal bracket

322: silicon carbide single crystal seed crystal

400: crucible in prior art

410: crack(s)

d 1: internal diameter of first reaction vessel (before Heat treatment)

d 2: internal diameter of the first reaction vessel (after Heat treatment)

Detailed Description

Examples are described in more detail below with reference to the accompanying drawings. In the drawings, sizes, intervals, etc. may be enlarged for facilitating understanding, may be different from actual sizes, and may be omitted as apparent to those of ordinary skill in the art to which the present invention pertains.

In the following description of the examples, the description that one structural element is formed on the upper or lower portion of the other structural element includes that one structural element is directly formed on the upper or lower portion of the other structural element or is indirectly formed through another structural element.

In the present specification, unless otherwise specified, "including" a structural element means that other structural elements may be included, and does not mean that other structural elements are excluded.

It should be understood that all numerical ranges indicating physical properties, dimensions, and the like of the constituent elements described in the present specification should be modified by "about" in all cases unless otherwise specified.

In this specification, unless otherwise specified, singular expressions include singular or plural ones as explained in the context.

Crucible pot

Referring to fig. 1, a crucible according to an embodiment of the present invention includes a first reaction container 110 and a second reaction container 120, the first reaction container 110 is disposed inside the second reaction container 120, and the inner diameter d1 of the first reaction container 110 can be enlarged.

Hereinafter, each structural element of the crucible of the above example will be specifically described.

Enlargement of the first reaction vessel

The interior of the first reaction vessel can be expanded.

Referring to fig. 1, the first reaction vessel 110 may have an enlarged inner diameter d2 after heat treatment relative to an inner diameter d1 before heat treatment.

For example, the inner diameter of the first reaction vessel may be enlarged more than 1 time, 1.001 times or more or 1.01 times or more than the initial diameter, and may be enlarged 1.2 times or less, 1.1 times or less, 1.05 times or less, 1.02 times or less or 1.015 times or less than the initial diameter.

Specifically, the inner diameter of the first reaction vessel can be enlarged by a factor of more than 1to 1.02 times or less as compared with the initial stage. When the amount is within the above range, there is an advantage in terms of expansion of the inner diameter corresponding to thermal expansion of the silicon carbide powder, and after the heat treatment, it is easier to separate the sintered body of the silicon carbide powder and load it into the growth crucible.

More specifically, the inner diameter of the first reaction vessel described above can be enlarged by a ratio of 1.001 to 1.015 times as compared with the initial stage.

Additionally, the inner diameter of the first reaction vessel may have a structure capable of expanding and contracting. Specifically, the inner diameter of the first reaction vessel may be contracted after the expansion. In this way, the inner diameter of the first reaction vessel can be restored to the state before the expansion by the heat treatment, and the first reaction vessel having the restored inner diameter can be reused for the heat treatment of another silicon carbide powder as described above.

Division of the first reaction vessel

The first reaction vessel may have a structure that can be divided into two or more parts. That is, the first reaction vessel may be divided into 2 or more parts, so that the inner diameter can be enlarged.

Fig. 2 is a perspective view of a first reaction vessel showing a crucible of an example. Referring to fig. 2, the first reaction vessel 110 may have 2 or more dividing surfaces 111 along a vertical direction (a height direction of the vessel).

Fig. 3 is a plan view showing various division methods of the first reaction vessel. Referring to fig. 3, the first reaction vessel may be divided into 2 to 8. Thus, the first reaction vessel may have a bottom surface divided into 2 or more.

In this case, the first reaction vessel may further include a flat plate disposed on the bottom surface.

Referring to fig. 4, the crucible further includes a plate 130 inserted into the bottom surface of the first reaction container, and the plate may be connected to the divided bottom surface. Specifically, even if the insert-type plate 130 is divided by the enlargement of the first reaction vessel, the continuity of the bottom surface can be maintained. Accordingly, when the first reaction vessel is expanded during the heat treatment, the insert-type plate 130 may improve the coupling force between the divided portions of the bottom surface and prevent the silicon carbide powder 210 from leaking.

Fig. 5 is a sectional view showing a first reaction vessel of another example.

Referring to fig. 5, the crucible further includes a flat plate 140 placed on the bottom surface of the first reaction container to contact the silicon carbide powder. That is, the crucible may further include a flat plate disposed on a bottom surface of the first reaction vessel, and the flat plate may cover a surface of the divided bottom surface.

As described above, when the bottom surface is divided during the heat treatment, the first reaction container 110 supporting the form of the silicon carbide powder can effectively prevent the silicon carbide powder 210 loaded into the first reaction container 110 from leaking downward through the dividing surface 111 (see the dotted circle in part (a) of fig. 5).

In this case, the diameter of the plate 140 may be larger than the inner diameter of the first reaction vessel 110 when it is expanded, and at least a portion of the edge of the plate 140 may be inserted into the body of the first reaction vessel 110. Such insertion of the plate edge portion may improve the coupling force between the respective divided portions of the bottom surface when the first reaction vessel is enlarged during the heat treatment.

The body of the first reaction vessel may have an inner space formed at a position where the edge of the plate is inserted. Referring to parts (b) to (d) of fig. 5, the inner space (dotted circle) may be designed in various structures.

Accordingly, the contact portion between the first reaction vessel and the edge portion of the flat plate can be minimized, and thus, various adverse effects caused by contact with the flat plate can be prevented in the process of expanding the first reaction vessel.

Material of first reaction vessel

Since the first reaction vessel is charged with the silicon carbide powder to perform the heat treatment, the first reaction vessel may be made of a material that can withstand high temperature conditions when the silicon carbide powder is heat-treated, for example, a carbon-based material.

On the other hand, since the inner diameter of the first reaction vessel can be enlarged as necessary, it is not necessary to consider the thermal expansion coefficient of the reaction vessel. For example, the first reaction vessel may be made of a material that expands and contracts greatly by heat treatment. As another example, the material of the first reaction vessel may be a material that does not substantially expand or contract due to heat treatment.

Specifically, the first reaction vessel may be made of one or more materials selected from the group consisting of graphite carbon, tantalum carbide, hafnium carbide, niobium carbide, titanium carbide, zirconium carbide, tungsten carbide, and vanadium carbide, or may be a graphite crucible coated with the above materials.

Second reaction vessel

The second reaction vessel protects the first reaction vessel disposed therein and prevents silicon carbide powder from leaking to the outside due to the division of the first reaction vessel.

The inner diameter of the second reaction vessel may be larger than the inner diameter of the first reaction vessel. Specifically, the inner diameter of the second reaction vessel may be the same as or slightly larger than the inner diameter of the first reaction vessel when it is maximally expanded.

The second reaction vessel may be made of a material that can withstand high temperature conditions when the silicon carbide powder is heat-treated, as in the first reaction vessel.

The material of the second reaction vessel may be the same as or different from that of the first reaction vessel. Specifically, the material of the second reaction vessel may be one or more selected from the group consisting of graphite carbon, tantalum carbide, hafnium carbide, niobium carbide, titanium carbide, zirconium carbide, tungsten carbide, and vanadium carbide, or may be a graphite crucible coated with the material.

Use and Effect

As described above, the crucible having the first reaction vessel and the second reaction vessel may be used to heat-treat silicon carbide powder as a raw material before preparing a silicon carbide single crystal ingot.

The crucible of the above example can enlarge the inner diameter so that damage of the crucible due to expansion and contraction does not occur when the heat treatment of the silicon carbide powder is performed. According to a preferred embodiment, after the inner diameter of the crucible is enlarged, it is also contracted as required, so that it can be easily reused. Therefore, the sintered body of the silicon carbide powder can be obtained by using the crucible, and based on this, a single crystal silicon carbide ingot can be grown, whereby the process effectiveness can be improved.

Heat treatment method of silicon carbide powder

Referring to fig. 1, a method for heat-treating silicon carbide powder according to an embodiment of the present invention includes: a step of charging silicon carbide powder 210 into first reaction vessel 110 disposed inside second reaction vessel 120; and a step of heat-treating the silicon carbide powder 210, wherein the inner diameter d1 of the first reaction vessel 110 is enlarged when the heat treatment is performed.

Hereinafter, the method of the above example will be described in detail in terms of the respective steps.

Charging of silicon carbide powder

First, silicon carbide powder is charged into a first reaction vessel disposed inside a second reaction vessel.

In the method of the above example, the crucible having the first reaction vessel and the second reaction vessel described above can be used, and the material, the characteristics, and the arrangement relationship thereof can be referred to the above examples.

The silicon carbide powder is not limited to a high purity powder or a low purity powder, and for example, the purity of the silicon carbide powder may be 90% or more, specifically, 90% to 99.9%, 90% to 99%, or 90% to 98%.

Heat treatment of silicon carbide powder

And (3) carrying out heat treatment on the silicon carbide powder.

The temperature condition for the above heat treatment may be 1800 to 2500 ℃. When in the above temperature range, necking (necking) between the plurality of particles of the raw material powder is more advantageous. Specifically, the temperature condition for the above heat treatment is 2000 ℃ to 2500 ℃, more specifically, may be 2100 ℃ to 2400 ℃.

Also, the pressure condition for the above heat treatment may be 400torr to 750torr, more specifically, 500torr to 700 torr.

When the heat treatment is performed, the inner diameter of the first reaction vessel is enlarged.

The expansion of the inner diameter of the first reaction vessel may be achieved in accordance with the expansion of the silicon carbide powder by the heat treatment.

By the heat treatment, the silicon carbide powder is strongly bonded through necking between ions as it expands. In this way, the heat treatment step can form the silicon carbide powder into a sintered body of silicon carbide powder. Even if the temperature is lowered thereafter, the sintered body of the silicon carbide powder is hardly shrunk.

The sintered body of silicon carbide powder prepared by the above heat treatment can have high purity by removing impurities at high temperature. For example, the sintered body of the silicon carbide powder may have a purity of 99% or more. Specifically, the sintered body of the above silicon carbide powder may have a purity of 99.5% or more or 99.9% or more. The sintered body of the silicon carbide powder as described above can be used as a high-purity raw material in the step of growing a silicon carbide single crystal ingot.

On the other hand, the growth process of the silicon carbide single crystal ingot may be performed using an additional crucible, instead of the crucible used for the heat treatment.

In this regard, the method of the above example may further include: separating the sintered body of the silicon carbide powder from the first reaction vessel after the heat treatment step; and a step of contracting the inner diameter of the first reaction vessel.

The contraction of the inner diameter of the first reaction vessel restores the inner diameter of the first reaction vessel to the state before the expansion by the heat treatment, and the first reaction vessel restored in the inner diameter can be reused for the heat treatment of another silicon carbide powder as described above.

Method for growing silicon carbide single crystal ingot

A method for producing a silicon carbide single crystal ingot according to an embodiment of the present invention includes: charging silicon carbide powder into a first reaction vessel disposed inside a second reaction vessel; obtaining a sintered body of silicon carbide powder by heat-treating the silicon carbide powder; and growing a silicon carbide single crystal ingot in a seed crystal from the sintered body of the silicon carbide powder, wherein the inner diameter of the first reaction vessel is enlarged when the heat treatment is performed.

In the method for producing a silicon carbide single crystal ingot of the above example, the above-described step of loading the silicon carbide powder and the step of obtaining a sintered body of the silicon carbide powder by heat treatment may be performed under the same conditions as the above-described method for heat treatment of the silicon carbide powder.

From the sintered body of the silicon carbide powder, a silicon carbide (SiC) single crystal ingot is grown in a seed crystal.

The growth of the silicon carbide single crystal ingot may be performed by an additional third reaction vessel instead of the first reaction vessel or the second reaction vessel.

Specifically, in the heat treatment step, a sintered body of silicon carbide powder is taken out from a first reaction vessel, the sintered body is separated from the first reaction vessel, and then the sintered body is loaded into a third reaction vessel to grow a silicon carbide single crystal ingot.

The above-mentioned third reaction vessel may have a structure of a general crucible for growth of a silicon carbide single crystal ingot, specifically, may be made of graphite, and has a structure in which the inner diameter is not changed by heat treatment.

Meanwhile, the inner diameter of the third reaction vessel may be the same as the diameter of the sintered body of the silicon carbide powder. The inner diameter of the third reaction vessel may be slightly larger than the diameter of the sintered body of the silicon carbide powder.

Since the sintered body of the silicon carbide powder is in a state in which the bonding between the powders is fixed, expansion due to additional heat treatment hardly occurs. Therefore, the growth of the single crystal ingot using the sintered body may be performed in a general crucible having a reaction vessel with a fixed inner diameter.

After the sintered body of silicon carbide powder is charged into the third reaction vessel, a seed crystal may be attached to the upper end of the inside of the third reaction vessel.

Referring to fig. 6, the sintered body 220 of silicon carbide powder may be loaded into the body 310 of the third reaction vessel, and a single crystal seed crystal 322 of silicon carbide may be mounted on a seed crystal holder 321 provided in the lid 320 of the third reaction vessel.

As the seed crystal, a seed crystal having a plurality of crystal structures can be used depending on the kind of crystal which can be grown as desired, such as 4H-SiC, 6H-SiC, 3C-SiC, or 15R-SiC.

When the seed crystal is mounted, the third reaction vessel may be sealed.

In addition, the third reaction vessel may be surrounded by a heat insulating material and may be placed in a reaction chamber (quartz tube, etc.) having a heating unit.

The insulating material and the reaction cavity are arranged outside the reaction container, and the temperature of the reaction container can be maintained at the crystal growth temperature. Since the crystal growth temperature of silicon carbide (SiC) is very high, the insulating material can be produced by pressing graphite carbon fibers into a tubular cylindrical graphite carbon felt having a predetermined thickness. In addition, the heat insulating material may surround the crucible by forming a plurality of layers. The heating means may be disposed outside the reaction chamber. For example, the heating means may be a heating coil or a resistance heating unit, and for example, a high-frequency induction coil may be used. The high-frequency induction coil is supplied with a high-frequency current to heat the crucible, thereby heating the raw material to a desired temperature.

Thereafter, the sintered body of the silicon carbide powder charged into the third reaction vessel is sublimated under high temperature conditions to grow a silicon carbide single crystal ingot on the seed crystal.

As for the temperature and pressure conditions for the growth of the silicon carbide (SiC) single crystal ingot, for example, the temperature and pressure conditions for the growth of the silicon carbide (SiC) single crystal ingot may be in the range of 2000 ℃ to 2500 ℃ and 1torr to 200torr, in the range of 2200 ℃ to 2400 ℃ and 1torr to 150torr, in the range of 2200 ℃ to 2300 ℃ and 1torr to 100torr, or in the range of 2250 ℃ to 2300 ℃ and 1torr to 50 torr.

The growth of the silicon carbide (SiC) single crystal ingot utilizes the principle that a silicon carbide (SiC) raw material substance (sintered body of silicon carbide powder) is sublimated into silicon carbide (SiC) gas under a high temperature condition, and then the silicon carbide (SiC) gas is grown into a single crystal ingot on a seed crystal under a reduced pressure condition, and therefore, the temperature and pressure conditions for the growth of the silicon carbide (SiC) single crystal ingot can be used without limitation as long as the pressure and temperature conditions are reduced with respect to the temperature and pressure conditions for the sublimation of the silicon carbide (SiC) raw material substance. That is, when the temperature and pressure conditions are higher than the above-described specific ranges, the same effect can be obtained by adjusting the pressure conditions to be appropriately higher in proportion to the higher temperature conditions.

The silicon carbide (SiC) single crystal ingot prepared according to the method of the above example may have high quality characteristics. For example, the silicon carbide (SiC) single crystal ingot may have a purity of 99% or more, 99.5% or more, or even 99.9% or more.

Claims

1. A crucible is characterized in that a crucible body is provided,

comprises a first reaction vessel and a second reaction vessel,

the first reaction vessel is disposed inside the second reaction vessel,

the first reaction vessel has a structure capable of expanding the inner diameter thereof.

2. The crucible according to claim 1, wherein the inner diameter of the first reaction vessel is enlarged by a ratio of 1to 1.02 times or less as compared with the initial stage.

3. The crucible according to claim 1, wherein the first reaction vessel has a structure capable of expanding and contracting an inner diameter thereof.

4. The crucible of claim 1, wherein the first reaction vessel has a structure that can be divided into two or more parts.

5. The crucible of claim 1, wherein the crucible is used for heat-treating silicon carbide powder as a raw material before preparing a silicon carbide single crystal ingot.

6. A heat treatment method of silicon carbide powder is characterized in that,

the method comprises the following steps:

charging silicon carbide powder into a first reaction vessel disposed inside a second reaction vessel; and

a step of heat-treating the silicon carbide powder,

7. The method of heat-treating silicon carbide powder according to claim 6, wherein the expansion of the inner diameter of the first reaction vessel is performed in accordance with the expansion of the silicon carbide powder by the heat treatment.

8. The method of heat-treating a silicon carbide powder according to claim 6, wherein in the heat-treating step, the silicon carbide powder is formed into a sintered body of the silicon carbide powder.

9. The method for heat treating silicon carbide powder according to claim 8, further comprising, after the heat treating step:

separating the sintered body of the silicon carbide powder from the first reaction vessel; and

and contracting the inner diameter of the first reaction vessel.

10. The method for heat-treating silicon carbide powder according to claim 6,

the above heat treatment step is carried out at a temperature of 1800 c to 2500 c,

the sintered body of the silicon carbide powder has a purity of 99% or more.