KR20200025449A - Method for growing semi-insulating silicon carbide single crystal ingot - Google Patents

Abstract

According to embodiment of the present invention, provided is a method of growing a semi-insulated silicon carbide (SiC) single crystal ingot, comprising the following steps: (a) charging a composition comprising a carbon-containing polymer resin, a solvent, a dopant, and SiC in a reaction vessel; (b) solidifying the composition; and (c) growing a SiC single crystal ingot on a seed crystal mounted in the reaction vessel. Accordingly, a high quality semi-insulated SiC single crystal ingot having a uniform doping concentration by thickness of the SiC single crystal ingot can be obtained.

Description

METHOD FOR GROWING SEMI-INSULATING SILICON CARBIDE SINGLE CRYSTAL INGOT}

Embodiments relate to a method of growing a semi-insulating SiC single crystal ingot after solidifying a composition comprising a carbon-containing polymer resin, a solvent, a dopant, and SiC.

Silicon carbide (SiC) has excellent heat resistance, mechanical strength, strong radiation resistance, and can be produced as a large-diameter substrate, and active research is being conducted as a substrate for next-generation power semiconductor devices. In particular, single crystal SiC has a large energy band gap and a superior break field voltage and thermal conductivity than silicon (Si). In addition, the carrier mobility of single crystal silicon carbide is comparable to that of silicon, and the saturation drift rate and breakdown voltage of electrons are also large. Therefore, single crystal hydrocarbons are expected to be applied to semiconductor devices that require high power, high efficiency, high breakdown voltage and high capacity.

In recent years, gallium nitride (GaN) and aluminum nitride (AlN) have attracted attention as materials for high frequency semiconductor devices. In such a substrate for a high frequency semiconductor device, it is essential to make the substrate highly resistant (1 × 10 ⁵ Ωcm or more), that is, to create a semi-insulated state, in order to improve the quality of the SiC substrate crystal and prevent the conduction with the device. It is an indispensable element.

Conventionally, in order to fabricate a semi-insulating SiC single crystal ingot, a method of mixing and synthesizing a dopant with SiC has been used. However, since the sublimation temperature of the dopant and SiC is different, the dopant is first sublimed. For example, the sublimation temperature of the vanadium dopant is about 1910 ° C, and the sublimation temperature of SiC is about 2700 ° C, so that vanadium is first sublimed. Therefore, since the doping concentration varies according to the ingot thickness, there is a problem that a difference in resistivity occurs depending on the ingot thickness. Specifically, the doping concentration by the thickness of the SiC single crystal ingot is changed by the excessive doping at the beginning of SiC single crystal ingot growth, less doping is done at the end of the SiC single crystal ingot growth.

In addition, during the growth of the SiC single crystal ingot, SiC may bounce toward the seed crystal due to thermal vibration or may interfere with the formation of the SiC Flux pattern. Therefore, the growth of the semi-insulated SiC single crystal ingot may be inhibited and the quality may be degraded.

In order to solve the above problems, a dopant is charged into a porous graphite container, or a method of embedding the dopant in SiC powder through synthesis has been used. However, this has a disadvantage in that the process is complicated, the cost increases, and it is difficult to improve the quality of the semi-insulated SiC single crystal ingot because it is difficult to control the doping concentration due to impurities generated in the porous graphite container. In addition, in order to solve the above problems, although the SiC and the dopant is used to grind or have a large particle size, this has the disadvantage that a separate powder heat treatment process is required.

Therefore, the research on the method of growing the semi-insulated SiC single crystal ingot which makes the semi-insulated state without degrading the quality of SiC single crystal ingot continues.

Korean Unexamined Patent Publication No. 2014-0110266

An embodiment is a high quality semi-insulating SiC single crystal ingot with a uniform doping concentration of SiC single crystal ingot by growing a semi-insulating SiC single crystal ingot after solidifying a composition comprising a carbon-containing polymer resin, a solvent, a dopant, and SiC. To provide.

According to an embodiment, a method of growing a semi-insulated SiC single crystal ingot may include: (a) charging a composition including a carbon-containing polymer resin, a solvent, a dopant, and SiC (silicon carbide) to a reaction vessel; (b) solidifying the composition; And (c) growing a SiC single crystal ingot on seed crystals mounted in the reaction vessel.

According to the method of growing a semi-insulated SiC single crystal ingot according to the embodiment, the dopant is prevented from subliming first, and the non-uniformity of the doping concentration for each thickness of the SiC single crystal ingot is improved to improve the quality of the semi-insulated SiC single crystal ingot. You can.

In addition, according to the growth method of the semi-insulated SiC single crystal ingot according to the embodiment, it is possible to suppress the incorporation of undesired impurities, it is easy to doping control.

In addition, according to the growth method of the semi-insulated SiC single crystal ingot according to the embodiment, it is easy to control the content of the dopant, it is possible to prevent the aggregation phenomenon in some areas.

1 illustrates a cross-sectional view of a reaction vessel in which a semi-insulated SiC single crystal ingot of an embodiment is grown.
2 is a cross-sectional view of a reaction vessel in which a conventional semi-insulated SiC single crystal ingot is grown.
3 shows a residual powder cross-sectional image of a semi-insulated SiC single crystal ingot of the example.
Figure 4 shows the residual powder cross-sectional image of the semi-insulated SiC single crystal ingot of the comparative example.
5 shows UV images of semi-insulated SiC single crystal ingots of the examples.
6 shows UV images of semi-insulated SiC single crystal ingots of the comparative example.
7 shows the surface image of the semi-insulated SiC single crystal ingot of the embodiment.
8 shows the surface image of the semi-insulated SiC single crystal ingot of the comparative example.

Hereinafter, the present invention will be described in detail through embodiments. The embodiments are not limited to the contents disclosed below and may be modified in various forms as long as the gist of the invention is not changed.

In the present specification, when a part "includes" a certain component, this means that it may further include other components, without excluding other components, unless specifically stated otherwise.

All numbers and expressions indicative of the amounts of ingredients, reaction conditions, and the like described herein are to be understood as being modified in all instances by the term "about" unless otherwise specified.

Conventionally, in order to grow a SiC single crystal ingot, a dopant is charged into a porous graphite container, or a method of embedding a dopant in SiC through synthesis has been used. 2 is a cross-sectional view of a reaction vessel in which a conventional semi-insulated SiC single crystal ingot is grown. FIG. 2 illustrates a structure of a reaction vessel in which a seed crystal 200 is mounted at an upper end of the inside, and a porous graphite container 500 loaded with a SiC 300 and a dopant 400 is charged at an inner lower end thereof.

However, according to the conventional method, there is a disadvantage in that the process is complicated and the cost increases, and it is difficult to improve the quality of the semi-insulated SiC single crystal ingot because it is difficult to control the doping concentration due to impurities generated in the porous graphite container. In addition, in order to solve the above problems, although the SiC and the dopant is used to grind or have a large particle size, this has the disadvantage that a separate powder heat treatment process is required.

According to one embodiment, a method of growing a semi-insulated SiC single crystal ingot is a phenomenon in which a dopant is first sublimed compared to SiC by solidifying a composition including a carbon-containing polymer resin, a solvent, a dopant, and SiC, and then growing a SiC single crystal ingot. Can be prevented. Therefore, by minimizing the nonuniformity of the doping concentration for each thickness of the SiC single crystal ingot, it is possible to improve the quality of the semi-insulated SiC single crystal ingot.

In addition, the growth method of the semi-insulating SiC single crystal ingot according to the embodiment can suppress the incorporation of undesired impurities, facilitate doping control, easily control the content of the dopant, and aggregate in some regions. This can be prevented from occurring.

Accordingly, the method of growing a semi-insulated SiC single crystal ingot according to an embodiment may provide a semi-insulated SiC single crystal ingot, while making a semi-insulated state and improving the quality of the SiC single crystal ingot.

Furthermore, through the uniform supply of raw materials, the growth rate and quality of SiC single crystal ingots are improved, as well as polymorphic control. That is, when using 4H-SiC, it is possible to lower the growth rate of 3C, 6H and 15R and to increase the growth rate of 4H.

1 illustrates a cross-sectional view of a reaction vessel in which a semi-insulated SiC single crystal ingot of an embodiment is grown. FIG. 1 illustrates a structure of a reaction vessel in which a seed crystal 200 is mounted at an inner upper end and a composition 100 solidified at an inner lower end is charged.

According to one embodiment, a method of growing a SiC single crystal ingot may include: (a) charging a composition including a carbon-containing polymer resin, a solvent, a dopant, and SiC (silicon carbide) to a reaction vessel; (b) solidifying the composition; And (c) growing a SiC single crystal ingot on seed crystals mounted in the reaction vessel.

First, in order to grow a SiC single crystal ingot, a composition containing a carbon-containing polymer resin, a solvent, a dopant, and SiC (silicon carbide) is charged to a reaction vessel (step (a)).

The reaction vessel may be a crucible and may be made of a material having a melting point above the sublimation temperature of SiC. For example, it may be made of graphite, but is not limited thereto.

The composition may be charged to the bottom of the reaction vessel.

According to one embodiment, the reaction vessel loaded with the composition may be closed. After enclosing the said reaction container with the heat insulation member of one or more layers, it puts into the reaction chamber (ex. Quartz tube etc.) provided with a heating means. The insulation member and the reaction chamber maintain the temperature of the reaction vessel at a SiC single crystal growth temperature.

The heating means may be induction heating or resistance heating means. For example, by allowing a high frequency current to flow through the high frequency induction coil, a high frequency induction coil for heating the reaction vessel to a desired temperature may be used, but is not limited thereto.

According to one embodiment, the carbon-containing polymer resin includes one or more selected from the group consisting of phenolic resins, polyacrylamide resins and thermosetting resins.

The phenolic resin may be at least one selected from the group consisting of novolak resins and resol resins, but is not limited thereto.

The polyacrylamide-based resin may be a polyamic acid resin, but is not limited thereto.

The thermosetting resin may be one or more selected from the group consisting of polyurethane resins, melamine resins, and alkyd resins, but is not limited thereto.

The composition may include 1 wt% to 40 wt% of the carbon-containing polymer resin based on the total weight of the composition. For example, the composition may include 5 wt% to 35 wt%, 5 wt% to 30 wt%, or 10 wt% to 30 wt% of the carbon-containing polymer resin based on the total weight of the composition. It is not limited to this.

According to one embodiment, the solvent may be at least one selected from the group consisting of ethanol, methanol, acetone, dimethylformamide and dimethyl sulfoxide. Specifically, the solvent may be ethanol, but is not limited thereto.

The composition may comprise 1 wt% to 20 wt% of the solvent, based on the total weight of the composition. For example, the composition may include 5 wt% to 17 wt%, 5 wt% to 15 wt%, or 10 wt% to 15 wt% of the solvent, based on the total weight of the composition, but is not limited thereto. It is not.

According to one embodiment, the dopant may be at least one selected from the group consisting of vanadium (V), chromium (Cr), manganese (Mn) and cobalt (Co). For example, the dopant may be transition elements (transition metal) or vanadium. Specifically, vanadium can form deep levels in any state of donor or acceptor in SiC crystals and compensate for shallow donor or shallow acceptor impurities, resulting in high resistance, i. Can be insulated.

The composition may comprise 1 wt% to 20 wt% dopant based on the total weight of the composition. For example, the composition may include 5 wt% to 17 wt%, 5 wt% to 15 wt%, and 10 wt% to 15 wt% of the dopant based on the total weight of the composition, but is not limited thereto. It is not.

In one embodiment, the SiC may be in the form of SiC powder.

The SiC may be in the form of SiC powder having a particle size of 10 μm to 5000 μm. Specifically, the size of the SiC particles may be 50 μm to 3000 μm, 50 μm to 2000 μm, 100 μm to 2000 μm, or 100 μm to 1000 μm, but is not limited thereto.

In one embodiment, the SiC may have a purity of 90% by weight to 99% by weight. Specifically, the SiC may have a purity of 91 wt% to 96 wt% or 92 wt% to 95 wt%, but is not limited thereto.

Next, in order to grow a SiC single crystal ingot, the composition is solidified (step (b)).

Specifically, the solidification of step (b) comprises drying the composition; Hardening; And carbonization or graphitization.

According to one embodiment, the drying may be carried out in a temperature range of 50 ℃ to 350 ℃. In addition, the curing may be carried out in a temperature range of 100 ℃ to 400 ℃. Specifically, by satisfying the drying and curing conditions, it may be advantageous to carbonize or graphitize the composition. For example, the drying may be performed for 1 hour to 5 hours in the temperature range of 50 ℃ to 350 ℃ or 50 ℃ to 300 ℃, but is not limited thereto. In addition, the curing may be performed for 1 hour to 10 hours in the temperature range of 100 ℃ to 400 ℃ or 150 ℃ to 400 ℃, but is not limited thereto.

According to one embodiment, the carbonization or graphitization is carried out at a temperature range of 200 ℃ to 2200 ℃ and pressure conditions of 1 torr to 1500 torr. Specifically, by satisfying the temperature and pressure conditions, it may be advantageous to carbonize or graphitize the composition. For example, the dopant that has undergone the drying and curing steps is subjected to a heat treatment at a temperature range of 300 ° C. to 600 ° C. and a pressure condition of 500 torr to 700 torr, followed by a temperature range of 2000 ° C. to 2200 ° C. and a 500 torr to 800 degree. It can be carbonized or graphitized under torr pressure conditions. In addition, the carbonization or graphitization may be performed for 2 to 5 hours, but is not limited thereto.

According to one embodiment, the carbonization or graphitization means heat treatment in an inert atmosphere. The inert atmosphere may be a nitrogen atmosphere or an argon atmosphere, but is not limited thereto.

According to one embodiment, the composition passed through step (b) is a solid that fills the entire inner bottom and part of the inner wall of the reaction vessel. In this case, during the growth of the SiC single crystal ingot, it is possible to prevent the SiC from sticking to the seed crystal due to the thermal vibration or preventing the formation of the SiC Flux pattern. In addition, it is possible to suppress the incorporation of inadvertent impurities and to prevent agglomeration from occurring in some regions.

According to another embodiment, the composition passed through step (b) may be a pellet-shaped solid.

According to yet another embodiment, the method may further include charging a pellet-shaped mold (a ') into the reaction vessel before step (a). The pellet shape produced from the pellet-shaped mold may be a cylindrical or polygonal columnar shape. For example, it may be a geometric shape such as a circle, a triangle, a square, a pentagon, a hexagon, an octagon, or a star, but is not limited thereto.

By separating the solidified composition that has undergone the steps (a '), (a) and (b) in a pellet-shaped mold, a pellet-shaped solid body can be obtained. Since the composition for producing the SiC single crystal ingot can be produced in a pellet-shaped solid body, it is easy to store and can also improve heat resistance and moisture resistance.

According to another embodiment, after charging the SiC to the bottom of the reaction vessel, the pellet-shaped solid body may be charged to the desired position. Specifically, the pellet-shaped solid body may be charged as in the conventional porous graphite container which was charged at the inner bottom of the reaction container in FIG. 2. Therefore, the pellet-shaped solid body is not only easy to doping control, can be freely used regardless of the structure of the reaction vessel, there is an advantage that can be easily stored, as well as heat resistance and moisture resistance.

According to one embodiment, the growth of the SiC single crystal ingot does not occur in step (b).

Next, a SiC single crystal ingot is grown on seed crystals mounted on the reaction vessel (step (c)).

The seed crystal may be mounted on the inner top of the reaction vessel. The seed crystal may be a seed crystal having various crystal structures depending on the type of crystal to be grown, such as 4H-SiC, 6H-SiC, 3C-SiC or 15R-SiC.

According to one embodiment, growing the SiC single crystal ingot in the seed crystals is a step of growing the seed crystals by sublimating the composition passed through step (b).

The sublimation point of the composition in step (c) is 2000 ℃ to 2500 ℃. Specifically, by the sublimation point of the composition satisfying the temperature range, it is possible to sublimate the dopant in a temperature range similar to SiC. For example, the sublimation point of the composition may be 2100 ° C to 2500 ° C or 2100 ° C to 2300 ° C, but is not limited thereto.

According to one embodiment, the temperature in step (b) may be 2000 ° C to 2500 ° C, 2200 ° C to 2500 ° C or 2250 ° C to 2300 ° C, but is not limited thereto. In addition, the pressure in step (b) may be 1 torr to 150 torr, 1 torr to 100 torr, or 1 torr to 50 torr, but is not limited thereto.

According to one embodiment, the SiC single crystal ingot may have a specific resistance of 0.1 Ωcm to 1 X 10 ¹⁰ Ωcm. For example, the SiC single crystal ingot may have a specific resistance of 0.1 Ωcm to 1 X 10 ⁵ Ωcm, 1 Ωcm to 1 X 10 ⁸ Ωcm or 10 Ωcm to 1 X 10 ⁵ Ωcm, but is not limited thereto. It doesn't happen.

According to one embodiment, the dopant concentration of the SiC single crystal ingot is from 5.5 X 10 ¹⁶ atoms / cc to 1 X 10 ¹⁸ atoms / cc. Specifically, the dopant concentration of the SiC single crystal ingot may be 5.5 X 10 ¹⁶ atoms / cc to 1.5 X 10 ¹⁷ atoms / cc or 1 X 10 ¹⁷ atoms / cc to 5 X 10 ¹⁷ atoms / cc, but is not limited thereto. no.

According to one embodiment, the SiC single crystal ingot has a purity of 95% to 99.9%. For example, the SiC single crystal ingot may have a purity of 95% to 99.5%, 97% to 99.5%, 98% to 99.5%, and 98% to 99%, but is not limited thereto.

The above content is described in more detail by the following examples. However, the following examples are only for illustrating the present invention, and the scope of the examples is not limited thereto.

EXAMPLE

As the carbon-containing polymer resin, 80% by weight of phenolic resin (product name: KC-5536, manufacturer: Gangnam Chemical), 18% by weight of ethanol solvent (manufacturer: OCI) and 2% by weight of vanadium dopant were mixed. After drying at 200 ° C. for 3 hours, it was cured at 400 ° C. for 2 hours. After heat treatment at 500 ° C. and 700 torr, the composition was solidified by carbonization or graphitization at 2000 ° C. and 760 torr for 5 hours.

After seed seeding was mounted on the inner top of the graphite crucible, the crucible was surrounded by a heat insulating member and placed in a reaction chamber equipped with a heating coil. After the inside of the crucible was vacuumed, argon gas was slowly injected. In addition, the temperature in the crucible was heated up to 2400 degreeC, and it heated up to 700 torr. Then, after gradually lowering the pressure to reach 30 torr, the SiC single crystal ingot was grown to seed crystals for 50 hours under the above conditions, thereby preparing a semi-insulated SiC single crystal ingot.

[Comparative Example]

A semi-insulated SiC single crystal ingot was prepared in the same manner as in the above example, except that a porous graphite container loaded with a dopant was used instead of the solidified composition.

Evaluation Example 1: Dopant Concentration Measurement

For the semi-insulated SiC single crystal ingot prepared in Examples and Comparative Examples, the concentration of the dopant was measured by using secondary ion mass spectrometry (SIM), and the results are shown in Table 1 below.

division Dopant Concentration (atoms / cc) Example 1.3 × 10 ¹⁷ Comparative example 5.3 × 10 ¹⁶

As shown in Table 1, it can be seen that the concentration of the dopant of the semi-insulated SiC single crystal ingot prepared according to the embodiment is larger than the concentration of the dopant of the semi-insulated SiC single crystal ingot prepared according to the comparative example.

 Evaluation Example 2: Evaluation of Residual Powder Sectional Image

Residual powder cross-sectional images were visually evaluated for the semi-insulated SiC single crystal ingots prepared in Examples and Comparative Examples.

Figure 3 shows the residual powder cross-sectional image of the semi-insulated SiC single crystal ingot of the embodiment, Figure 4 shows the residual powder cross-sectional image of the semi-insulated SiC single crystal ingot of the comparative example.

As shown in FIG. 3, it can be seen that the semi-insulated SiC single crystal ingot manufactured according to the embodiment evenly sublimes in the entire region. On the other hand, as shown in Figure 4, the semi-insulating SiC single crystal ingot of the comparative example can be seen that the sublimation mainly occurred at the position where the porous container.

Evaluation Example 3: UV Image Evaluation

The semi-insulated SiC single crystal ingots prepared in Examples and Comparative Examples were evaluated by visual inspection using UV lamp irradiation.

5 shows a UV image of the semi-insulated SiC single crystal ingot of the embodiment, and FIG. 6 shows a UV image of the semi-insulated SiC single crystal ingot of the comparative example.

The polymorphism control can be confirmed through the UV images of FIGS. 5 and 6. Specifically, green represents 4H, red represents 6H, and black represents 15R.

Thus, as shown in FIG. 5, the semi-insulated SiC single crystal ingot manufactured according to the embodiment was formed with the desired 4H uniformly. On the other hand, as shown in Figure 6, the semi-insulated SiC single crystal ingot prepared according to the comparative example 4H, 6H and 15H can be seen that the quality of the SiC single crystal ingot is partially formed.

 Evaluation Example 4: Surface Image Evaluation

For the semi-insulated SiC single crystal ingots prepared in Examples and Comparative Examples, surface images were evaluated using an optical microscope.

FIG. 7 shows a surface image of the semi-insulated SiC single crystal ingot of the embodiment, and FIG. 8 shows the surface image of the semi-insulated SiC single crystal ingot of the comparative example.

As shown in FIG. 7, in the growing of the SiC single crystal ingot, the concentration of the dopant was kept uniform so that precipitation of the dopant hardly occurred. On the other hand, as shown in Figure 8, the SiC single crystal ingot of the comparative example was excessively doped to precipitate the dopant.

100: solidified composition
200: seed crystal
300: SiC
400: dopant
500: porous graphite container
600: where the porous graphite container was

Claims (12)

(a) charging a composition comprising a carbon-containing polymer resin, a solvent, a dopant, and SiC (silicon carbide) into a reaction vessel;
(b) solidifying the composition; And
(c) growing a SiC single crystal ingot on seed crystals mounted to the reaction vessel. The method of claim 1,
Wherein said carbon-containing polymer resin comprises at least one member selected from the group consisting of phenolic resins, polyacrylamide resins and thermosetting resins. The method of claim 1,
The dopant comprises one or more selected from the group consisting of vanadium (V), chromium (Cr), manganese (Mn) and cobalt (Co). The method of claim 1,
Step (b) comprises drying the composition; Hardening; And a process of carbonization or graphitization. The method of claim 4, wherein
The drying is carried out in a temperature range of 50 ° C to 350 ° C. The method of claim 4, wherein
Wherein the curing is carried out in a temperature range of 100 ° C. to 400 ° C. The method of claim 4, wherein
Wherein the carbonization or graphitization is carried out at a temperature range of 200 ° C. to 2200 ° C. and pressure conditions of 1 torr to 1500 torr. The method of claim 4, wherein
Wherein said carbonization or graphitization is heat treated in an inert atmosphere. The method of claim 1,
The SiC is in powder form, the size of the powder particles is 10 ㎛ to 5000 ㎛. The method of claim 1,
Wherein the solidified composition is a pellet-shaped solid. The method of claim 1,
And the SiC single crystal ingot has a specific resistance of 0.1 Ωcm to 1 × 10 ¹⁰ Ωcm. The method of claim 1,
And the SiC single crystal ingot has a dopant concentration of 5.5 X 10 ¹⁶ atoms / cc to 1 X 10 ¹⁸ atoms / cc.

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