KR102090084B1 - Method for growing semi-insulating silicon carbide single crystal ingot - Google Patents

Abstract

An embodiment is a method of growing a semi-insulated SiC single crystal ingot, comprising: (a) loading a dopant coated with SiC (silicon carbide) and a carbon-based material into a reaction vessel equipped with a seed crystal; And (b) growing a SiC single crystal ingot on the seed crystal, whereby a high quality semi-insulated SiC single crystal ingot having a uniform doping concentration for each thickness of the SiC single crystal ingot can be obtained.

Description

How to grow semi-insulated silicon carbide single crystal ingots {METHOD FOR GROWING SEMI-INSULATING SILICON CARBIDE SINGLE CRYSTAL INGOT}

Embodiments relate to a method of growing a semi-insulated SiC single crystal ingot using a dopant coated with a carbon-based material.

Silicon carbide (SiC) has excellent heat resistance and mechanical strength, has strong properties against radiation, and has the advantage of being able to be produced as a large-diameter substrate, and is actively researched as a substrate for next-generation power semiconductor devices. In particular, single crystal silicon carbide (single crystal SiC), the energy band gap (energy band gap) is large, the maximum breakdown field (break field voltage) and thermal conductivity (thermal conductivity) is superior to silicon (Si). In addition, the carrier mobility of the single crystal silicon carbide is comparable to that of silicon, and the saturation drift rate and the 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 withstand voltage and high capacity.

Recently, 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 X 10 ⁵ Ω㎝ or more), that is, to create a semi-insulated state, in order to improve the quality of SiC substrate crystals and prevent energization with the element. It is an indispensable factor.

Conventionally, in order to manufacture a semi-insulated 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 first sublimates. For example, since the sublimation temperature of the vanadium dopant is about 1910 ° C and the sublimation temperature of SiC is about 2700 ° C, vanadium is first sublimated. Therefore, since the doping concentration varies depending on the thickness of the ingot, there is a problem that a difference in resistivity occurs depending on the thickness of the ingot. Specifically, the doping concentration for each thickness of the SiC single crystal ingot is changed due to excessive doping at the beginning of the growth of the SiC single crystal ingot and less doping at the end of the growth of the SiC single crystal ingot.

In order to solve the above problems, a dopant is loaded into a porous graphite container, or a method of incorporating a dopant into SiC powder through synthesis has been used. However, this has the disadvantage that the process is complicated and the cost increases. In addition, since it is difficult to control the doping concentration due to impurities generated in the porous graphite container, it is difficult to improve the quality of the semi-insulated SiC single crystal ingot.

Accordingly, research into a method of growing a semi-insulated SiC single crystal ingot that creates a semi-insulated state without deteriorating the quality of the SiC single crystal ingot is continuing.

Korea Patent Publication No. 2014-0110266

The embodiment is to grow a semi-insulated SiC single crystal ingot using a dopant coated with a carbon-based material to provide a high-quality semi-insulated SiC single crystal ingot having a uniform doping concentration by thickness of the SiC single crystal ingot.

A method of growing a semi-insulated SiC single crystal ingot according to an embodiment includes (a) loading a dopant coated with SiC (silicon carbide) and a carbon-based material into a reaction vessel equipped with a seed crystal; And (b) growing a SiC single crystal ingot on the seed crystal.

According to the method of growing a semi-insulated SiC single crystal ingot according to an embodiment, the dopant is prevented from subliming before SiC, and the non-uniformity of the doping concentration by thickness of the SiC single crystal ingot is minimized to improve the quality of the semi-insulated SiC single crystal ingot I can do it.

In addition, according to the method for growing a semi-insulated SiC single crystal ingot according to an embodiment, it is possible to grow a semi-insulated SiC single crystal ingot through a simple process, as well as to minimize the amount of unreacted raw materials, thereby reducing the cost There is.

1 shows a cross-sectional view of a reaction vessel for growing a semi-insulated SiC single crystal ingot of an embodiment.
2 is a sectional view showing a reaction vessel for growing a conventional semi-insulated SiC single crystal ingot.
Figure 3 shows the surface image of the semi-insulating SiC single crystal ingot of the embodiment.
4 shows a surface image of a semi-insulated SiC single crystal ingot of a comparative example.
5A to 5C show the doping concentrations in the early, middle and late stages in the step of growing the semi-insulated SiC single crystal ingot of the embodiment.
6A to 6C show the doping concentrations in the early, middle, and late stages in the step of growing the semi-insulated SiC single crystal ingot of the comparative example.
7 shows the UV image of the semi-insulating SiC single crystal ingot of the embodiment.
8 shows a UV image of a semi-insulated SiC single crystal ingot of a comparative example.

Hereinafter, the 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 is to “include” a certain component, it means that the component may further include other components, not to exclude other components, unless otherwise stated.

It should be understood that all numbers and expressions indicative of the amount of ingredients, reaction conditions, and the like described in this specification are modified in all cases with the term "about" unless otherwise specified.

Conventionally, in order to grow a SiC single crystal ingot, a dopant is loaded into a porous graphite container, or a method of incorporating a dopant into SiC through synthesis has been used. 2 is a sectional view showing a reaction vessel for growing a conventional semi-insulated SiC single crystal ingot. In FIG. 2, the structure of the reaction vessel in which the seed crystal 200 is mounted on the inner top and the porous graphite container 500 loaded with the SiC 100 and the dopant 400 is loaded on the inner bottom is illustrated.

However, according to the conventional method, there is a disadvantage that the process is complicated and costs increase. In addition, since it is difficult to control the doping concentration due to impurities generated in the porous graphite container, it is difficult to improve the quality of the semi-insulated SiC single crystal ingot.

The method of growing a semi-insulated SiC single crystal ingot according to an embodiment may prevent a phenomenon that a dopant first sublimates compared to SiC by growing a SiC single crystal ingot using a dopant coated with a carbon-based material. Therefore, by minimizing the non-uniformity 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 semi-insulated SiC single crystal ingot can be grown through a simple process using a dopant coated with a carbon-based material, and the amount of unreacted raw materials can be minimized, thereby reducing cost.

Furthermore, since the supply of raw materials is uniformly performed using a dopant coated with a carbon-based material, it is advantageous for improving the growth rate and quality of the SiC single crystal ingot, as well as for polymorphic control. That is, when using 4H-SiC, it is possible to lower the growth rates of 3C, 6H and 15R, and increase the growth rate of 4H.

Therefore, the method of growing a semi-insulated SiC single crystal ingot according to an embodiment may provide a semi-insulated SiC single crystal ingot with improved quality of the SiC single crystal ingot while creating a semi-insulated state.

1 shows a cross-sectional view of a reaction vessel for growing a semi-insulated SiC single crystal ingot of an embodiment. In FIG. 1, the structure of the reaction vessel in which the seed crystal 200 is mounted on the inner top and the dopant 300 coated with the SiC 100 and the carbon-based material is loaded on the inner bottom is illustrated.

A method of growing a semi-insulated SiC single crystal ingot according to an embodiment includes (a) loading a dopant coated with SiC (silicon carbide) and a carbon-based material into a reaction vessel equipped with a seed crystal; And (b) growing a SiC single crystal ingot on the seed crystal.

First, in order to grow a SiC single crystal ingot, a dopant coated with SiC and a carbon-based material is charged in a reaction vessel equipped with a seed crystal (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 seed crystal may be mounted on the inner top of the reaction vessel. As the seed crystal, seed crystals having various crystal structures may be used according to the type of crystal to be grown, such as 4H-SiC, 6H-SiC, 3C-SiC, or 15R-SiC.

The dopant coated with the SiC and carbon-based material may be loaded at the bottom of the reaction vessel.

According to one embodiment, the reaction vessel loaded with the dopant coated with the SiC and the carbon-based material may be sealed. After surrounding the reaction vessel with one or more insulating members, it is placed in a reaction chamber (eg, quartz tube, etc.) equipped with heating means. The heat insulating member and the reaction chamber keep 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 flowing a high frequency current to the high frequency induction coil, a high frequency induction coil may be used to heat a reaction vessel to heat a dopant coated with SiC and a carbon-based material to a desired temperature, but is not limited thereto.

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

For example, 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% to 99% by weight. Specifically, the SiC may have a purity of 91% to 96% by weight or 92% to 95% by weight, but is not limited thereto.

According to one embodiment, the carbon-based material may be carbon black, graphite, or a combination thereof.

The dopant coated with the carbon-based material is dried a composition comprising a carbon-containing polymer resin, a solvent and a dopant; Hardening; Carbonization or graphitization; And crushing.

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

The phenol-based resin may be at least one selected from the group consisting of novolac resin and resol resin, 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 resin, melamine resin and alkyd resin, but is not limited thereto.

The composition may include 1% to 40% by weight of a 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% carbon-containing polymer resin based on the total weight of the composition, , But is not limited thereto.

According to one embodiment, the solvent may be one or more 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 include 1% by weight to 20% by weight of a 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 a 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 elements), or may be vanadium. Specifically, vanadium can form a deep level in any state of a donor or acceptor in a SiC crystal, compensating for a shallow donor or shallow acceptor impurity, making the crystal highly resistant, i.e., half It can be made insulated.

The composition may include 0.5% to 10% by weight of a dopant based on the total weight of the composition. For example, the composition may include 0.5 wt% to 8 wt%, 1 wt% to 8 wt%, or 1 wt% to 5 wt% dopant based on the total weight of the composition, but is not limited thereto. It is not.

According to one embodiment, the drying may be performed in a temperature range of 50 ℃ to 350 ℃. In addition, the curing may be performed in a temperature range of 100 ℃ to 400 ℃. Specifically, by satisfying the drying and curing conditions, it may be advantageous to uniformly coat the carbon-based material on the dopant. For example, the drying may be performed for 1 hour to 5 hours in a temperature range of 50 ° C to 350 ° C or 50 ° C to 300 ° C, but is not limited thereto. In addition, the curing may be performed for 1 hour to 10 hours in a temperature range of 100 ° C to 400 ° C or 150 ° C to 400 ° C, but is not limited thereto.

According to one embodiment, the carbonization or graphitization is performed in a temperature range of 200 ° C to 2200 ° C and a pressure condition of 1 torr to 1500 torr. Specifically, by satisfying the carbonization or graphitization conditions, it is easy to coat the dopant with a carbon-based material. For example, the dopant that has undergone the drying and curing step is subjected to heat treatment under a temperature range of 300 ° C to 600 ° C and a pressure condition of 500 torr to 700 torr, and then a temperature range of 2000 ° C to 2200 ° C and 500 torr to 800 It can be carbonized or graphitized under torr pressure condition. 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 carbonized or graphitized dopant performs a process of grinding.

The pulverization may be performed by a method of a pulverization process by top-down, ball mill, jet mill, or the like, but is not limited thereto.

According to one embodiment, the particle size of the dopant coated with the carbon-based material may be 1 μm to 2000 μm. For example, the particle size of the dopant coated with the carbon-based material may be 5 μm to 1000 μm, 10 μm to 1000 μm, or 10 μm to 500 μm, but is not limited thereto.

According to an embodiment, the particles of the dopant may be coated with the carbon-based material, in whole or in part, on the outer surface. Specifically, the dopant may be entirely coated with the carbon-based material, or 50% or more of the external surface may be coated with the carbon-based material.

According to one embodiment, the coating thickness of the portion coated with the carbon-based material is 1 μm to 100 μm. Specifically, the doping concentrations of the dopants in the initial, middle, and late stages may be uniformized in the step of growing the SiC single crystal ingot by satisfying the thickness range of the coating thickness of the portion coated with the carbon-based material. For example, the coating thickness of the portion coated with the carbon-based material may be 5 μm to 50 μm, 5 μm to 40 μm, 10 μm to 40 μm, 10 μm to 30 μm, or 10 μm to 25 μm, but is not limited thereto. It does not work.

Next, a SiC single crystal ingot is grown on the seed crystal (step (b)).

According to one embodiment, the step of growing a SiC single crystal ingot in the seed crystal of step (b), sublimates the dopant coated with the SiC and carbon-based materials charged in step (a) to grow on the seed crystal This is the step.

The sublimation point of the SiC is 2000 ℃ to 2800 ℃. Further, the sublimation point of the dopant is 1800 ° C to 2000 ° C, and the sublimation point of the dopant coated with the carbon-based material is 2000 ° C to 2500 ° C. Specifically, by sublimation point of the dopant coated with the carbon-based material satisfies the above range, it is possible to sublimate the dopant within a temperature range similar to SiC. For example, the sublimation point of the dopant coated with the carbon-based material 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 Ω㎝ to 1 X 10 ¹⁰ Ω㎝. For example, the SiC single crystal ingot may have a specific resistance of 0.1 Ω㎝ to 1 X 10 ⁵ Ω㎝, 1 Ω㎝ to 1 X 10 ⁸ Ω㎝ or 10 Ω㎝ to 1 X 10 ⁵ Ω㎝, but is not limited thereto. It does not work.

According to one embodiment, the dopant concentration of the SiC single crystal ingot is 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 contents will be 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 to these.

[Example]

As a carbon-containing polymer resin, 80% by weight of a phenolic resin (product name: KC-5536, manufacturer: Gangnam Chemicals), 18% by weight of an ethanol solvent (manufacturer: OCI) and 2% by weight of vanadium dopant were mixed. After drying at 200 ° C for 3 hours, curing at 400 ° C for 2 hours. After heat treatment at 500 ° C and 700 torr, carbonization or graphitization for 5 hours at 2000 ° C and 760 torr, followed by pulverization, a dopant coated with a carbon-based material having an average particle size of 10 μm Was prepared.

After the seed crystal was mounted on the inner top of the graphite crucible, a SiC powder and a dopant coated with the carbon-based material were charged. 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. At the same time, the temperature in the crucible was raised to 2400 ° C, and the temperature was raised to 700 torr. Thereafter, the pressure was gradually lowered to reach 30 torr, and the SiC single crystal ingot was grown in a seed crystal for 50 hours under the above conditions to prepare a semi-insulated SiC single crystal ingot.

[Comparative example]

A semi-insulated SiC single crystal ingot was manufactured in the same manner as in the above example, except that a porous graphite container loaded with a dopant was used instead of a dopant coated with a carbon-based material.

[Evaluation Example 1: Dopant concentration measurement]

For the semi-insulated SiC single crystal ingots prepared in Examples and Comparative Examples, concentrations of dopants were measured using SIMS (Secondary ion mass spectrometry), and the results are shown in Table 1 below.

division Dopant concentration (atoms / cc) Example 1.1 × 10 ¹⁷ Comparative example 5.3 × 10 ¹⁶

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

[Evaluation Example 2: Surface image evaluation]

About the semi-insulated SiC single crystal ingot prepared in the above Examples and Comparative Examples, the surface image was evaluated visually using an optical microscope.

Figure 3 shows the surface image of the semi-insulated SiC single crystal ingot of the embodiment, Figure 4 shows the surface image of the semi-insulated SiC single crystal ingot of the comparative example.

As shown in FIG. 3, in the semi-insulated SiC single crystal ingot prepared according to the embodiment, the concentration of the dopant was uniformly maintained in the step of growing the SiC single crystal ingot, so that precipitation of the dopant hardly occurred. On the other hand, as shown in FIG. 4, the semi-insulated SiC single crystal ingot of the comparative example was over-doped in the step of growing the SiC single crystal ingot, and a dopant was deposited.

[Evaluation Example 3: Change of doping concentration in the growth stage]

For the semi-insulated SiC single crystal ingots prepared in the above Examples and Comparative Examples, the doping concentration change images of the initial, middle, and late stages of the step of growing the SiC single crystal ingot in seed crystals were evaluated using substrate processing.

5A to 5C show the doping concentrations of the initial, middle, and end stages in the step of growing the semi-insulated SiC single crystal ingot of the embodiment, and FIGS. 6A to 6C are the initial and middle stages in the step of growing the semi-insulated SiC single crystal ingot of the comparative example. And terminal doping concentrations, respectively.

As shown in Figures 5a to 5c, it can be seen that the semi-insulated SiC single crystal ingot prepared according to the embodiment is uniformly transparent to the entire substrate. On the other hand, as shown in Figures 6a to 6c, it can be seen that the semi-insulated SiC single crystal ingot of the comparative example has a partially dark color and non-uniform color distribution.

[Evaluation Example 4: Ingot surface and UV image evaluation]

For the semi-insulated SiC single crystal ingots prepared in Examples and Comparative Examples, the UV image was evaluated through visual inspection using UV Lamp irradiation.

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

The polymorphic control may be confirmed through the UV images of FIGS. 7 and 8. Specifically, green represents 4H, red represents 6H, and black represents 15R. Accordingly, as shown in FIG. 7, the desired 4H was uniformly formed in the semi-insulated SiC single crystal ingot prepared according to the embodiment. On the other hand, as shown in FIG. 8, it can be seen that the semi-insulated SiC single crystal ingot prepared according to the comparative example is partially formed with 4H, 6H, and 15H, so that the quality of the SiC single crystal ingot is low.

100: SiC
200: seed crystal
300: dopant coated with a carbon-based material
400: dopant
500: porous graphite container

Claims (13)

(a) loading a dopant coated with SiC (silicon carbide) and a carbon-based material into a reaction vessel equipped with a seed crystal; And
(b) growing a SiC single crystal ingot in the seed crystal,
A method of growing a SiC single crystal ingot having a coating thickness of 1 μm to 100 μm in a portion coated with the carbon-based material. According to claim 1,
The carbon-based material is carbon black, graphite or a combination thereof. According to claim 1,
The dopant coated with the carbon-based material is dried a composition containing a carbon-containing polymer resin, a solvent and a dopant; Hardening; Carbonization or graphitization; And manufactured through the process of grinding. According to claim 3,
The carbon-containing polymer resin comprises at least one member selected from the group consisting of phenolic resins, polyacrylamide resins and thermosetting resins. According to claim 3,
The drying is performed in a temperature range of 50 ° C to 350 ° C. According to claim 3,
The curing is carried out in a temperature range of 100 ℃ to 400 ℃, method. According to claim 3,
The carbonization or graphitization is performed in a temperature range of 200 ° C to 2200 ° C and a pressure condition of 1 torr to 1500 torr. According to claim 3,
The carbonization or graphitization is a method of heat treatment in an inert atmosphere. According to claim 1,
The dopant comprises one or more selected from the group consisting of vanadium (V), chromium (Cr), manganese (Mn) and cobalt (Co). According to claim 1,
The particle size of the dopant coated with the carbon-based material is 1 μm to 2000 μm. According to claim 1,
The SiC is in powder form, the size of the powder is 10 ㎛ to 5000 ㎛, the method. According to claim 1,
The SiC single crystal ingot has a specific resistance of 0.1 mm 2 to 1 × 10 ¹⁰ mm 2. According to claim 1,
The dopant is one or more selected from the group consisting of vanadium (V), chromium (Cr), manganese (Mn) and cobalt (Co),
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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