KR20190101346A - Method for growing silicon carbide single crystal ingot with large diameter - Google Patents

Abstract

A method for disposing a seed crystal of SiC single crystal with a carbonaceous protective film in a reaction vessel without adhesion and growing the SiC single crystal from a SiC raw material on the seed crystal does not attach the seed crystal to a holder, so that a large-diameter single crystal ingot can be grown due to no warpage or cracks caused during heating. Particularly, according to the embodiment, the carbonaceous protective film is formed in multiple layers, and physical properties of the layers are different, thereby having enhanced the film quality, adhesion between the seed crystal and the protective film, thickness and heat resistance of the protective film than the same obtained when forming the protective film in a single layer.

Description

METHOD FOR GROWING SILICON CARBIDE SINGLE CRYSTAL INGOT WITH LARGE DIAMETER}

Examples relate to methods of growing SiC single crystal ingots from silicon carbide (SiC) raw materials, and seed crystals used therein. More specifically, the embodiment relates to a method of growing a large diameter SiC single crystal ingot from a SiC raw material to seed crystals, and a seed crystal having a protective film used therein.

Single crystals such as silicon carbide (SiC), silicon (Si), gallium nitride (GaN), sapphire (Al ₂ O ₃ ), gallium arsenide (GaAs) and aluminum nitride (AlN) are polycrystals thereof. The demand in the industrial sector is increasing because it shows unpredictable characteristics.

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. Due to these characteristics, single crystal silicon carbide is expected to be applied to semiconductor devices requiring high efficiency, high breakdown voltage and high capacity.

As a method of producing such a single crystal, for example, Japanese Patent Laid-Open No. 2001-114599 discloses that the temperature of the seed crystal is 10 to 10 to the temperature of the raw material powder while heating by a heater in a vacuum vessel (heating furnace) into which argon gas can be introduced. It is disclosed to grow single crystal ingots on seed crystals by keeping them at a low temperature of 100 ° C.

In order to grow single crystal ingots, the seed crystals are generally pasted in advance. For example, in the conventional process, referring to FIG. 7, after the adhesive 150 is applied between the seed crystal holder 190 and the seed crystal 110 and pressed, the seed crystals are adhered to each other, and then inside the reaction vessel 200. The single crystal ingot was grown on the front surface of the seed crystal 110 by heating and subliming the raw material 300.

Japanese Laid-Open Patent Publication No. 2001-114599 (2001.04.24)

In the conventional method of adhering the seed crystal to the holder on the upper part of the reaction vessel, warpage or crack occurs due to residual stress due to the difference in the coefficient of thermal expansion (CTE) between the seed crystal and the holder. There is a difficulty in growing a large-diameter single crystal ingot because it grows further increases as the diameter increases.

In addition, according to the conventional method, the seed crystal is adhered to the holder on the upper part of the reaction vessel by using an adhesive, so that problems such as deterioration of quality during seed growth of the single crystal ingot, seed crystal detachment, and contamination of the seed crystal surface are also caused by the adhesive. there was.

Thus, the embodiment seeks to provide a method for growing large diameter and high quality SiC single crystal ingots by growing single crystal ingots without adhering the seed crystals to the holders.

In addition, the embodiment is to provide a seed crystal with a protective film used in the method and a manufacturing method thereof.

According to one embodiment, (1) forming a protective film on the back of the seed crystal of the silicon carbide (SiC) single crystal; (2) charging a SiC raw material to the bottom of the reaction vessel, and disposing the seed crystals on top of the reaction vessel without adhesion; And (3) growing a SiC single crystal ingot from the SiC raw material over the seed crystal, wherein the protective film comprises a first carbonaceous layer and a second carbonaceous layer, wherein the first carbonaceous layer And the second carbonaceous layer is provided with a method of growing a SiC single crystal ingot having different physical properties.

According to another embodiment, (a) preparing a first composition and a second composition containing a binder resin and a filler; (b) coating the first composition on the backside of the seed crystals of silicon carbide (SiC) single crystals and carbonizing to graphitizing to form a first carbonaceous layer; (c) coating the second composition on the surface of the first carbonaceous layer and carbonizing or graphitizing to form a second carbonaceous layer, wherein the first carbonaceous layer and the second carbonaceous layer Silver provides a method for producing seed crystals having a protective film, having different physical properties.

According to another embodiment, a seed crystal of a silicon carbide (SiC) single crystal, and a protective film formed on the back of the seed crystal, wherein the protective film is a first carbonaceous layer in contact with the back of the seed crystal, and the first carbon And a second carbonaceous layer formed on the vaginal layer, wherein the first carbonaceous layer and the second carbonaceous layer have different physical properties, and seed crystals with a protective film are provided.

According to the growth method of the SiC single crystal ingot of the above embodiment, since seed crystals are not attached to the holder, there is no warpage or crack due to residual stress caused by the difference in thermal expansion coefficient during the heating process, so that a large diameter single crystal ingot can be grown. have. In addition, according to the above embodiment, since it is not necessary to apply the adhesive to the seed crystals, the degradation of the quality due to the adhesive can also be prevented.

In addition, according to the embodiment, since the carbonaceous protective film is formed on the rear surface of the seed crystal, it is possible to prevent loss of the rear surface of the seed crystal which may occur during heating for growth. Particularly, according to the embodiment, the carbonaceous protective film is formed in multiple layers and the physical properties of each layer are different, so that the adhesion between the film quality, the seed crystal and the protective film, and the thickness and heat resistance of the protective film can be improved compared to the case of forming the protective film in a single layer. Can be. Accordingly, it is possible to more effectively suppress the stress that may occur during the growth of the single crystal ingot, thereby preventing the deterioration of the quality such as the occurrence of cracking of the ingot.

1 illustrates a method of forming a protective film on seed crystals according to an embodiment.
2a and 2b is a reaction vessel configuration for producing a SiC single crystal ingot according to the embodiment.
3 and 4 respectively observe the surface of the protective film provided in the seed crystals prepared in Example 1 and Comparative Example 1.
5 is a cross-sectional view of a seed crystal provided with a protective film prepared in Example 1.
6 is a photograph of a SiC single crystal ingot prepared in Example 2.
7 is a configuration of a reaction vessel for producing a SiC single crystal ingot according to a conventional method.

In the following description of the embodiments, the reference for the top or bottom of each component will be described with reference to the drawings. In addition, in the accompanying drawings, sizes, intervals, etc. may be exaggeratedly displayed for clarity, and the descriptions of those skilled in the art may be omitted.

Manufacturing method of seed crystal with protective film

According to an embodiment of the present invention, a method of preparing seed crystals includes: (a) preparing a first composition and a second composition containing a binder resin and a filler; (b) coating the first composition on the back side of silicon carbide (SiC) seed crystals and carbonizing to graphitizing to form a first carbonaceous layer; (c) coating the second composition on the surface of the first carbonaceous layer and carbonizing or graphitizing to form a second carbonaceous layer, wherein the first carbonaceous layer and the second carbonaceous layer Has different physical properties.

Hereinafter, each step will be described in more detail.

(a) Preparation of Coating Composition

In step (a), a first composition and a second composition containing a binder resin and a filler are prepared.

The binder resin forms a main component of the coating composition for preparing the protective film. The binder resin may be, for example, a phenol resin, a polyacrylonitrile resin, a pitch resin, a polyvinyl chloride resin, a polyacrylic acid resin, a furan resin, an epoxy resin, or a mixed resin thereof.

It is preferable that the binder resin has a high actual carbon ratio. For example, the binder resin may have a residual amount of 5 to 50%, or 10 to 30% in an inert atmosphere.

In addition, the binder resin is preferably a curable resin, for example, may be a thermosetting resin.

The filler promotes carbonization during heat treatment after coating of the composition and prevents excessive shrinkage, thereby preventing cracks from forming.

The filler may be, for example, a carbonaceous filler, a metal filler, or a composite filler thereof. Specifically, the filler is impression graphite, earth graphite, expanded graphite, carbon black, carbon nanotubes, graphene, tantalum (Ta), tungsten (W), rhenium (Re), molybdenum (Mo), hafnium (Hf), It may contain components such as tantalum carbide (TaC) and tungsten carbide (WC).

The first composition may include 20 to 300 parts by weight, or 50 to 200 parts by weight of a filler based on 100 parts by weight of the binder resin.

In addition, the second composition may include a filler 10 to 200 parts by weight, or 30 to 150 parts by weight with respect to 100 parts by weight of the binder resin.

When the composition is within the above preferred range, it may be more advantageous to prevent surface shrinkage or cracks during heat treatment after coating, while having excellent coating properties of the composition.

As a more specific example, a phenol resin is used as the binder resin, graphite is used as the filler, and the first composition includes 100 to 180 parts by weight of a filler relative to 100 parts by weight of the binder resin, and the second composition is It may include 50 to 120 parts by weight of the filler relative to 100 parts by weight of the binder resin.

As another specific example, a phenol resin is used as the binder resin, impression graphite is used as the filler, and the first composition includes 120 to 150 parts by weight of a filler relative to 100 parts by weight of the binder resin, and the second The composition may include 80 to 100 parts by weight of the filler relative to 100 parts by weight of the binder resin.

The composition is preferably a liquid composition for the efficiency of the coating.

Accordingly, the composition may contain a solvent such as ethanol, methanol, acetone, dimethylformamide (DMF), dimethyl sulfoxide (DMSO).

At this time, the solid content of the composition may be 1 to 50% by weight, or 5 to 30% by weight.

The first composition and the second composition may have different solids content or viscosity. Preferably, the first composition may have a lower solids content than the second composition. Accordingly, the first composition may have a relatively low viscosity to improve adhesion to seed crystals.

At this time, the solid content of the first composition may be 1 to 30% by weight, or 1 to 20% by weight. In addition, the solid content of the second composition may be 5 to 50% by weight, or 5 to 30% by weight.

As a preferred example, the first composition has a solids content of 5-15% by weight and the second composition has a solids content of 8-18% by weight, wherein the first composition has a lower solids content than the second composition. It may have a content.

The composition may further contain a wet dispersant, an antifoaming agent, and the like.

In addition, the third composition, the fourth composition, and the like, which are different from the first composition and the second composition, may be further prepared to achieve various layer configurations of the protective film.

(b) formation of a first carbonaceous layer

In step (b), the first composition is coated on the rear surface of silicon carbide (SiC) seed crystals and carbonized to graphitized to form a first carbonaceous layer.

In the present specification, the term "front" of a seed crystal generally refers to a side on which a single crystal ingot grows on both sides of a seed crystal having a wide and flat shape, and on the contrary, the "back side" of a seed crystal refers to an opposite side to a surface on which a single crystal ingot grows. do.

Specifically, as shown in (a) to (c) of FIG. 1, the first composition is coated on the back surface 112 of the seed crystal 110 of SiC single crystal to obtain a first coating film 121 ′, and then heat treatment. By drying and curing, and carbonization to graphitization to form the first carbonaceous layer 121. At this time, the first coating film may have a thickness of 1 ~ 40 ㎛, 1 ~ 20 ㎛, or 1 ~ 10 ㎛.

As the seed crystal, seed crystals having various crystal structures may be used depending on the kind of crystals to be grown, such as 4H-SiC, 6H-SiC, 3C-SiC, or 15R-SiC.

The seed crystals may be subjected to a cleaning step before coating. The silicon dioxide oxide film formed by the reaction of silicon with oxygen may be formed on the surface of the seed crystal. Since the seed crystal may deviate or cause defects when the single crystal ingot is grown in a subsequent process, it is preferable to remove it in advance by washing. The washing may be performed using acetone, alcohol, distilled water, acid solution, and the like, may be performed by sonication or dipping, and may be performed once or twice or more.

When the washing is completed, the coating of the first composition may be performed on the back of the seed crystals.

The coating may use conventional coating methods such as spin coating and tape casting.

In addition, the coating may be carried out in a thickness range of 0.1 ~ 2000 ㎛, or a thickness range of 20 ~ 1500 ㎛. If the coating thickness is too small compared to the above preferred range, there is a possibility that it may not play a role of the protective film after the heat treatment. On the contrary, if the coating thickness is too large, bubbles may be contained during the heat treatment, cracks, peeling off of the coating, and the like.

Thereafter, the first composition coated on the rear surface of the seed crystals is carbonized to graphitized to form a first carbonaceous layer.

For example, the first composition may be heat-treated at a temperature of 300 ° C. or higher, for example, 300˜2200 ° C., followed by drying and curing, and carbonization to graphitization may be performed.

The binder resin contained in the first composition is carbonized or further graphitized by the heat treatment to form a first carbonaceous layer. In addition, the filler in the composition may prevent cracks that may occur during heat treatment and promote carbonization to graphitization.

The heat treatment temperature may be more specifically 400 ° C or higher, 500 ° C or higher, or 600 ° C or higher, for example, 400 to 1500 ° C, 500 to 1000 ° C, 1500 to 2500 ° C, or 2000 to 2500 ° C. In addition, the heat treatment may be performed for 1 to 10 hours, or 1 to 5 hours.

In one embodiment, the heat treatment may be carried out at a temperature increase rate of 0.5 ~ 5 ℃ / min and temperature conditions of 500 ℃ or more or 600 ℃ or more, for example, the temperature is raised to a temperature of 500 ~ 1000 ℃, and maintain the temperature After heating for 1 to 5 hours, it can be carried out by cooling at a rate of 0.5 ~ 5 ℃ / min.

In another embodiment, the heat treatment may be carried out at a temperature increase rate of 1 ~ 5 ℃ / min and temperature conditions of more than 1500 ℃ or more than 2000 ℃, for example, up to a temperature of 1500 ~ 2500 ℃ or a temperature of 2000 ~ 2500 ℃ After heating, maintaining the temperature and heating for 1 to 5 hours, it can be carried out by cooling at a rate of 1 ~ 5 ℃ / min.

The heat treatment may be performed in an inert gas atmosphere, for example, may be performed in an argon gas or a nitrogen gas atmosphere.

The heat treatment may be performed by induction heating or resistance heating. That is, the heat treatment may be performed in an induction heating kiln, or may be performed in a resistance heating kiln.

(c) formation of a second carbonaceous layer

In the step (c), the second composition is coated on the surface of the first carbonaceous layer and carbonized to graphitize to form a second carbonaceous layer.

Specifically, as shown in (d) and (e) of FIG. 1, the second composition is coated on the surface of the first carbonaceous layer 121 to obtain a second coating film 122 ′, and then dried by heat treatment. And through hardening, carbonization to graphitization to form the second carbonaceous layer 122. At this time, the second coating film may have a thickness of 11 ~ 100 ㎛, 11 ~ 50 ㎛, or 11 ~ 30 ㎛.

In addition, specific conditions of the process for forming the second carbonaceous layer may employ the conditions exemplified in the process of forming the first carbonaceous layer.

The first carbonaceous layer and the second carbonaceous layer may have different amounts of fillers. Preferably the second carbonaceous layer may have a greater amount of filler than the first carbonaceous layer. That is, the amount of the total filler contained in the second carbonaceous layer may be greater than the amount of the total filler contained in the first carbonaceous layer.

Thus, by containing a relatively large amount of filler in the second carbonaceous layer it is possible to ensure the heat resistance required at high temperature growth.

In order to increase the amount of filler contained in the second carbonaceous layer, the filler content (%) of the second carbonaceous layer may be increased or the thickness of the second carbonaceous layer may be increased. Accordingly, the second carbonaceous layer may have a higher filler content or a larger thickness than the first carbonaceous layer.

In addition, as needed, an additional carbonaceous layer may be further formed on the second carbonaceous layer 122. In this case, the additional carbonaceous layer may be formed using the raw material composition (second composition) of the second carbonaceous layer, or may be formed using another composition (third composition, fourth composition, etc.).

For example, one to eight or one to four additional carbonaceous layers may be further formed on the second carbonaceous layer, where the additional carbonaceous layers may be formed using the second composition.

Through such a repeating process of forming the carbonaceous layer, the seed crystal 110 is provided with a multi-layered carbonaceous protective film 120.

With shield Seed crystal

Seed crystal provided with a protective film according to an embodiment includes a seed crystal of silicon carbide (SiC) single crystal, and a protective film formed on the back of the seed crystal, wherein the protective film is a first carbonaceous layer in contact with the back of the seed crystal, and And a second carbonaceous layer formed on the first carbonaceous layer, wherein the first carbonaceous layer and the second carbonaceous layer have different physical properties.

The first carbonaceous layer and the second carbonaceous layer are different from each other in terms of physical properties such as thickness, adhesion, and heat resistance.

The first carbonaceous layer may have excellent adhesion to seed crystals to prevent peeling from occurring during heat treatment and ingot growth after coating. Specifically, the first carbonaceous layer may have a relatively higher adhesion than the second carbonaceous layer.

In addition, the second carbonaceous layer may have excellent heat resistance to high temperature, thereby preventing cracks or disappearing in the protective layer during heat treatment and ingot growth after coating. Specifically, the second carbonaceous layer may have a relatively higher heat resistance than the first carbonaceous layer.

In addition, the first carbonaceous layer and the second carbonaceous layer may have different thicknesses. Preferably, the second carbonaceous layer may have a larger thickness than the first carbonaceous layer.

In this case, the thickness of the first carbonaceous layer may be 0.1-20 μm, 0.2-15 μm, or 0.3-10 μm. In addition, the thickness of the second carbonaceous layer may be 1 to 50 μm, 2 to 30 μm, or 3 to 20 μm.

As a specific example, the first carbonaceous layer may have a thickness of 0.5 to 5 μm, and the second carbonaceous layer may have a thickness of 6 to 15 μm.

The protective film may be carbonized to graphitized composition comprising a binder resin and a filler. That is, the first carbonaceous layer and the second carbonaceous layer may be a carbonized to graphitized composition comprising a binder resin and a filler.

Accordingly, the carbonaceous protective layer may include uncrystallized carbon or crystallized carbon (eg, graphitized carbon). That is, the carbonaceous protective film may include carbide or graphite of the binder resin.

In this case, the binder resin may be a phenol resin, a polyacrylonitrile resin, a pitch resin, a polyvinyl chloride resin, a polyacrylic acid resin, a furan resin, an epoxy resin, and a mixed resin thereof. In addition, the filler may be a carbon-based filler, a metal-based filler, or a composite filler thereof.

In addition, the first carbonaceous layer and the second carbonaceous layer may have different amounts of fillers. Preferably the second carbonaceous layer may have a greater amount of filler than the first carbonaceous layer.

In addition, the first carbonaceous layer and the second carbonaceous layer are carbonized to graphitized liquid first composition and second composition, respectively, wherein the first composition has a lower solids content than the second composition. Can have

The protective layer may further include 1 to 8 additional carbonaceous layers in addition to the first carbonaceous layer and the second carbonaceous layer. That is, the passivation layer may further include additional carbonaceous layers, such as a third carbonaceous layer and a fourth carbonaceous layer, on the second carbonaceous layer.

In this case, the additional carbonaceous layers may have the same or different physical properties as the first carbonaceous layer or the second carbonaceous layer. For example, the additional carbonaceous layers may have the same physical properties as the second carbonaceous layer.

The total thickness of the multilayer carbonaceous protective film may be, for example, in the range of 10 to 1500 µm, or in the range of 15 to 1000 µm, or in the range of 20 to 500 µm.

As a preferred example, the protective film may further include 1 to 8 additional carbonaceous layers, and the protective film may have a total thickness of 20 to 1500 μm.

As such, by forming the carbonaceous protective film in multiple layers and configuring different physical properties for each layer, the carbonaceous protective film can be improved in terms of adhesion between the film quality, seed crystal and the protective film, and thickness and heat resistance of the protective film, rather than forming a single protective film.

SiC Single Crystal Ingot Growth Method

SiC single crystal ingot growth method according to the embodiment, (1) forming a protective film on the back of the seed crystal of silicon carbide (SiC) single crystal; (2) charging a SiC raw material to the bottom of the reaction vessel, and disposing the seed crystals on top of the reaction vessel without adhesion; And (3) growing a SiC single crystal ingot from the SiC raw material over the seed crystal, wherein the protective film comprises a first carbonaceous layer and a second carbonaceous layer, wherein the first carbonaceous layer And the second carbonaceous layer have different physical properties.

(1) Preparation of seed crystals equipped with a protective film

In the step (1), a protective film is formed on the rear surface of the seed crystal of the silicon carbide (SiC) single crystal.

As a preferred example, step (1) comprises the steps of (a) preparing a first composition and a second composition containing a binder resin and a filler; (b) coating the first composition on the backside of the seed crystal of SiC single crystal and carbonizing to graphitizing to form a first carbonaceous layer; And (c) coating the second composition on the surface of the first carbonaceous layer and carbonizing or graphitizing to form a second carbonaceous layer.

In this case, the first composition may have a lower solids content than the second composition, and the second carbonaceous layer may have a larger amount of filler than the first carbonaceous layer.

Specific process conditions of steps (a) to (c) are as described above.

In addition, the specific configuration of the resulting seed crystal provided with a protective film as described above.

(2) Charging SiC raw material and disposing of seed crystal

In step (2), the silicon carbide (SiC) raw material is charged to the lower portion of the reaction vessel, and the seed crystal is disposed on the upper portion of the reaction vessel without adhesion.

As such, the method according to the embodiment does not adhere seed crystals to the holder.

Preferably, the reaction vessel is not provided with a holder for the adhesion of seed crystals.

As an example, referring to Figure 2a, the reaction vessel 200 is provided with a cradle 250 on the upper inner wall without a seed crystal holder, the seed crystal 110 is to be placed on the cradle 250 without adhesive Can be. In this case, the seed crystal 110 may be disposed to face the front surface of the seed crystal with respect to the SiC raw material. That is, the rear surface of the seed crystal (surface with a protective film) may be disposed to face the upper portion of the reaction vessel 200 such that the front surface (growth surface) of the seed crystal 110 faces the lower portion of the reaction vessel 200. . The cradle 250 is not particularly limited in shape, but may have, for example, a flat shape. In addition, the holder 250 may be formed in such a way that a part of the upper inner wall of the reaction vessel 200 protrudes.

As another example, referring to Figure 2b, the reaction vessel 200 is provided with a cradle 250 is grooved in the upper portion without a seed crystal holder, the seed crystal may be disposed without being fitted into the groove of the holder. . In this case, the seed crystal 110 may be disposed to face the front surface of the seed crystal with respect to the SiC raw material. That is, the rear surface of the seed crystal (surface with a protective film) may be disposed to face the upper portion of the reaction vessel 200 such that the front surface (growth surface) of the seed crystal 110 faces the lower portion of the reaction vessel 200. . The cradle 250 is not particularly limited in shape, but may have, for example, a shape in which a groove is recessed in a cross-section in a "c" shape.

In this case, the reaction vessel may have an open top structure and may employ a method in which the reaction vessel is sealed by the seed crystal. For example, the reaction vessel 200 is closed by a seed crystal (seed crystal provided with a protective film) fitted into a groove of the holder 250 while having no cover or an open lid 220 thereon. It may also be employed.

The reaction vessel may be a crucible and is made of a material having a melting point above the sublimation temperature of SiC. For example, the reaction vessel may be composed of a carbonaceous component, specifically, a graphite component. In addition, the holder may be made of the same or different carbonaceous components as the components of the reaction vessel.

In addition, the SiC raw material may be SiC powder, for example.

The reaction vessel may then be enclosed with a heat insulator and placed in a reaction chamber (quartz tube, etc.) having heating means.

In this case, the heating means may be, for example, an induction heating coil or a resistance heating means.

(3) growth of SiC single crystal ingot

In step (3), a SiC single crystal ingot is grown from the SiC raw material to the entire surface of the seed crystal.

The SiC single crystal ingot may be grown on the seed crystal by sublimation of the raw material.

Temperature and pressure conditions for the growth of the SiC single crystal ingot, for example, the step of growing the SiC single crystal ingot is a condition in the range of 2000 ~ 2500 ℃ and 1 ~ 200 torr, 2200 ~ 2400 ℃ and 1 ~ 150 torr It can be carried out by heating to the conditions of, the conditions of 2200 ~ 2300 ℃ and 1 ~ 100 torr, or the conditions of 2250 ~ 2300 ℃ and 1 ~ 50 torr.

However, the growth of SiC single crystal ingot is based on the principle that the SiC raw material is sublimed into SiC gas at high temperature, and then SiC gas is grown to single crystal ingot on seed crystal under reduced pressure, so the temperature and pressure for the growth of SiC single crystal ingot The conditions may be employed without particular limitation as long as the pressure is reduced under the temperature and pressure conditions at which the SiC raw material is sublimed.

That is, when the temperature and pressure conditions exemplified in the specific numerical ranges above are performed at higher temperature conditions, the same effects can be achieved by adjusting the pressure and pressure conditions appropriately in proportion thereto.

In this way, the seed is also heated together during heating for growth, and if a protective film is not provided, part of the seed crystal may be lost by sublimation. That is, since the SiC gas sublimed from the raw material is continuously supplied to the front surface (growth surface) of the seed crystals, the rear surface of the seed crystals is affected by heating even if there is no problem. However, according to the embodiment, since the carbonaceous protective film is formed on the rear surface of the seed crystal, it is possible to prevent loss of the rear surface of the seed crystal due to heating.

In addition, according to the embodiment, by forming the carbonaceous protective film in a multi-layered structure, the physical properties of each layer may be different, so that the film quality, adhesion between the seed crystal and the protective film, and the thickness of the protective film may be improved, compared with the case of forming a single protective film. . Accordingly, it is possible to more effectively suppress the stress that may occur during the growth of the single crystal ingot, thereby preventing the deterioration of the quality such as the occurrence of cracking of the ingot.

In particular, according to the embodiment, since the seed crystal is not attached to the holder, the SiC single crystal ingot can be manufactured in a large diameter. For example, the SiC single crystal ingot after the growth step according to the embodiment may have a diameter of at least 2 inches, at least 3 inches, at least 4 inches, at least 5 inches, and even at least 6 inches. As an example, SiC single crystal ingots prepared according to embodiments may have apertures in the range of 2-10 inches, 2-8 inches, 4-8 inches, or 4-6 inches.

Moreover, according to the method of the Example, since an adhesive agent is not apply | coated to a seed crystal, SiC single crystal ingot can be manufactured with high quality. For example, the SiC single crystal ingot prepared according to the embodiment may have a purity of 99% or more, 99.5% or more, and even 99.9% or more.

Hereinafter, more specific embodiments will be described by way of example.

The materials used in Example 1 below are as follows:

-Binder Resin: Phenolic Resin, KC-5536, Gangnam Hwaseong

Filler: impression graphite, purity 80 ~ 99%, D ₅₀ 2.5 ㎛

Solvent: Ethanol, OCI

-SiC single crystal seed crystal: diameter 100 ~ 150 mm, crystal structure 4H-SiC, thickness 350 ~ 1000 ㎛

-SiC raw material powder: purity 99.99% or more, D ₅₀ 100 ㎛

Example 1: Preparation of seed crystals equipped with a protective film (multilayer, filler added)

Step (1): Preparation of Coating Composition

First, a binder resin is mixed with a solvent to prepare a solution having a solid content of about 10% by weight, then about 135 parts by weight of a filler is added to 100 parts by weight of the binder resin, and additives such as a wet dispersion agent and an antifoaming agent are added within 5 parts by weight. Mixing and dispersing gave a first composition.

In addition, after the binder resin is mixed with the solvent to prepare a solution having a solid content of about 13% by weight, about 90 parts by weight of filler is added to 100 parts by weight of the binder resin, and additives such as a wet dispersion agent and an antifoaming agent are added within 5 parts by weight. Mixing and dispersing gave a second composition.

Step (2): Formation of the First Carbonaceous Layer

The first composition was spin coated on the rear surface (opposite side of the growth surface) of silicon carbide seed crystals to obtain a first coating film having a thickness of 5 μm. The coated seed crystals were put in an oven and heated at a rate of 1 ° C./min to reach 600 ° C., followed by heat treatment for 2 hours to carbonize the first coating film. Thereafter, cooling was performed at a rate of 1 ° C./min to obtain seed crystals in which a first carbonaceous layer was formed on the rear surface.

Step (3): Formation of Second Carbonaceous Layer

The second composition was spin coated on the surface of the first carbonaceous layer to obtain a second coating layer having a thickness of 20 μm. The coated seed crystals were put in an oven and heated at a rate of 1 ° C./min to reach 600 ° C., followed by heat treatment for 2 hours to carbonize the second coating layer. After cooling at a rate of 1 ° C./min, seed crystals were formed in which the first carbonaceous layer and the second carbonaceous layer were sequentially formed on the rear surface.

Step (4): Formation of Additional Carbonaceous Layer

In the same manner as in the step (3), the procedure of spin coating the second composition on the surface of the second carbonaceous layer and then heat-treating was repeated to further form an additional carbonaceous layer.

Comparative Example 1 Preparation of Seed Crystal with Protective Film (Single Layer, No Filler Added)

On the back side of the silicon carbide seed crystal, without mixing the filler with the liquid phenolic resin Spin coating was performed to obtain a coating film having a thickness of 400 μm. The coated seed crystals were put in a heater to heat up at a rate of 1 ° C./min to reach 600 ° C., and then heat treated for 2 hours to carbonize the coating film. Thereafter, the mixture was cooled at a rate of 1 ° C./min to obtain seed crystals having a single layer of carbonaceous protective film formed on the rear surface thereof.

Example 2: Growth of Silicon Carbide Monocrystalline Ingot (Simple Fermentation)

A graphite crucible having a holder on the upper inner wall was prepared. SiC powder was charged as a raw material in the lower part of the crucible. In addition, the seed holder with the protective film prepared in Example 1 was placed on the upper holder in the crucible (see FIG. 2A). At this time, the seed crystal did not perform any adhesion with the holder and was placed on the holder. In addition, the rear surface of the seed crystal (surface with a protective film) was directed toward the top of the crucible, and the growth surface of the seed crystal (surface without a protective film) was directed toward the lower crucible.

The crucible was covered with a lid, surrounded by a heat insulator and placed in a reaction chamber equipped with a heating coil. After making the inside of the crucible into a vacuum state, argon gas was slowly injected to reach atmospheric pressure and gradually reduced in pressure. In addition, the temperature in the crucible was heated up to 2300 degreeC with this. Thereafter, SiC single crystal ingots were grown on the surface not provided with a seed protective film for 100 hours at 2300 ° C. and 20 torr. As a result, as shown in FIG. 6, a SiC single crystal ingot of 4 to 6 inches diameter was obtained.

Test Example 1 Evaluation of Physical Properties of Protective Film

The physical properties of the protective film provided in the seed crystals prepared in Example 1 were evaluated.

The protective film was measured using a thermal diffusivity measuring instrument (LFA447, NETZCH) to determine the thermal diffusivity of 143 mm 2 / s. The protective film was also measured to have a thermal conductivity of 158.5 W / mK, a density of 1.3 g / cm 3, and a specific heat of 0.85 J / gK.

Test Example 2: Observation of the cross section of the protective film

The cross section of the seed crystal provided with the protective film prepared in Example 1 was observed with an electron microscope.

As a result, as shown in Figure 5, it was confirmed that a multi-layered protective film formed on the back of the seed crystal.

Test Example 3: Evaluation of Protective Film Surface

The surface of the protective film provided in the seed crystals prepared in Example 1 and Comparative Example 1 was observed. As a result, the protective film produced in Example 1 was excellent in the surface state without peeling and a crack, as shown to Fig.3 (a). On the other hand, in the protective film prepared in Comparative Example 1, as shown in Fig. 4 (a), peeling and cracks occurred, the surface state was poor.

In addition, after the single crystal ingot growth of Example 2, the surface of the protective film provided in the seed crystal was observed. As a result, as shown in Fig. 3B, no hole generation or disappearance was observed in the protective film even after single crystal ingot growth.

In addition, after the single crystal ingot was grown according to the procedure of Example 2 using the seed crystal provided with the protective film prepared in Comparative Example 1, the surface of the protective film was observed. As a result, as shown in (b) of FIG. 4, in the comparative example, holes were formed in the protective film after single crystal growth, and disappearance was observed.

Test Example 4: Crack Evaluation of Single Crystal Ingot Surface

About the SiC single crystal ingot obtained by the said Example 2, the crack of the ingot surface was expanded and confirmed using the naked eye or an optical microscope. As a result, no crack was found on the surface of the ingot.

110: seed crystal, 111: front of seed crystal, 112: rear of seed crystal,
120: protective film, 121 ': first coating film, 121: first carbonaceous layer,
122 ': second coating film, 122: second carbonaceous layer, 150: adhesive,
190: seed crystal holder, 200: reaction vessel, 210: reaction vessel body,
220: open cover, 250: holder, 300: raw material.

Claims (7)

(a) preparing a first composition and a second composition containing a binder resin and a filler;
(b) coating the first composition on the backside of the seed crystals of silicon carbide (SiC) single crystals and carbonizing to graphitizing to form a first carbonaceous layer of 0.5 to 5 μm thickness;
(c) coating the second composition on the surface of the first carbonaceous layer and carbonizing to graphitizing to form a second carbonaceous layer having a thickness of 6 to 15 μm,
The second carbonaceous layer has a greater amount of filler than the first carbonaceous layer,
The first carbonaceous layer and the second carbonaceous layer has a different physical properties, the method of producing seed crystals with a protective film. The method of claim 1,
The first composition has a lower solids content than the second composition, a method for producing seed crystals with a protective film. The method of claim 1,
The binder resin is a phenol resin, a polyacrylonitrile resin, a pitch resin, a polyvinyl chloride resin, a polyacrylic acid resin, a furan resin, an epoxy resin, and a mixed resin thereof;
A method for producing seed crystals with a protective film, wherein the filler is a carbon filler, a metal filler, or a composite filler thereof. The method of claim 1,
After step (c), further comprising forming one to eight additional carbonaceous layers on the second carbonaceous layer,
Wherein the additional carbonaceous layers are formed using the second composition. Seed crystal of silicon carbide (SiC) single crystal, and
It includes a protective film formed on the back of the seed crystal,
Where the protective film is
A first carbonaceous layer in contact with the back of the seed crystal, and
A second carbonaceous layer formed on the first carbonaceous layer,
The first carbonaceous layer has a thickness of 0.5 to 5 μm, the second carbonaceous layer has a thickness of 6 to 15 μm,
The second carbonaceous layer has a higher amount of filler than the first carbonaceous layer,
The first carbonaceous layer and the second carbonaceous layer has different properties, seed crystals with a protective film. The method of claim 5,
The first carbonaceous layer and the second carbonaceous layer is a seed crystal having a protective film, carbonized to graphitized composition comprising a binder resin and a filler. The method of claim 6,
The binder resin is a phenol resin, a polyacrylonitrile resin, a pitch resin, a polyvinyl chloride resin, a polyacrylic acid resin, a furan resin, an epoxy resin, and a mixed resin thereof;
Seed crystal with a protective film, wherein the filler is a carbon-based filler, a metal-based filler, or a composite filler thereof.

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