KR20210082020A - Manufacturing method of High-purity SiC particulate material - Google Patents

Abstract

The present invention relates to a method of manufacturing a high-purity silicon carbide powdered material and, more specifically, to a method of manufacturing a high-purity silicon carbide powdered material which is used as a material for manufacturing silicon carbide (SiC) single crystals. The method of manufacturing a high-purity silicon carbide powdered material includes: a first step of depositing silicon carbides (SiC) on a deposition platform of a graphite material by using a silicon carbide (SiC) precursor as a material in a deposition chamber; a second step of collecting the deposition platform in which the silicon carbides are deposited; a third step of separating powder or grains of the deposited silicon carbides from the collected deposition platform; a fourth step of controlling the size of the separated powder of the silicon carbides; and a fifth step of removing and refining impurities from the silicon carbide powder, of which the size has been controlled.

Description

Manufacturing method of high-purity SiC particulate material

The present invention relates to a method for manufacturing a high-purity silicon carbide powdery raw material, and more particularly, to a method for manufacturing a high-purity silicon carbide powdery raw material used as a manufacturing raw material for a silicon carbide (SiC) single crystal.

Silicon carbide (SiC) semiconductor has a large band gap (~3.2 eV), semiconductor size reduction due to high dielectric breakdown, low power loss, and high temperature stability. Since it is possible to realize a device that can be used even at ~500°C, it is expected as a solution according to the limitations of Si semiconductor characteristics. to be.

For this, it is essential to develop efficiency and saving technology in the field of electric energy, which accounts for 30 to 35% of the total energy consumed. In this field, the development and practical use of power semiconductor devices using SiC-semiconductor is currently a silicon wafer. It is expected to lower the semiconductor conversion loss from 12% to 3%. In addition, SiC devices are being applied to applications with a rated voltage of 1000V or higher, especially in air conditioners, solar power generation, and inverters for electric vehicles. SiC single crystal wafers are certain to be applied to power devices such as electric vehicles and hybrid cars, energy conversion devices for solar devices, power devices for various electronic products that require energy saving, LED/LD devices, and high-frequency devices. As the market is expected, development is being actively carried out mainly in advanced materials such as the US, Japan, and Europe.

Recently, SiC power semiconductor technology development has reached maturity and the market is blooming, so the supply of SiC wafers is increasing. However, the manufacturing cost is still high compared to Si wafers, so the need for technology to reduce the manufacturing cost is high.

6-inch class 4H-SiC single crystal growth (POSCO) and 6N5 class high-purity powder technology have been developed through the WPM project “ultra-high-purity SiC material” of the Ministry of Knowledge Economy, launched in 2009. It has a near-level SiC single crystal manufacturing technology.

SiC single crystals are usually produced by the PVT (Sublimation Recrystallization, Physical Vapor Transport method) method in which SiC powder is sublimated and then recrystallized to the seed crystal phase. In this case, the quality level such as particle size and purity of the SiC powder used is manufactured. Since it has a decisive effect on the quality of the single crystal, it is necessary to manufacture a high-purity powder.

In general, when single crystals are grown using the PVT method, the larger and more uniform the particle size of the raw material powder is, the greater the packing density increases, which is advantageous for long-axis single crystal growth. known to be advantageous.

In the case of SiC powder containing a large amount of impurities, various defects (pores, micropipe defects, dislocations, polytypes, grain boundaries) may occur during the crystal growth process due to the influence of impurities. Due to this, problems such as material breakage during material processing after the growth process, non-uniform epi-thick formation during epi-growth, yield drop due to leakage current during device formation, and reduced lifespan are occurring.

For the synthesis of high-purity and ultra-high purity SiC powder, direct reaction method of Si and C, SiO ₂ carbothermal reduction method, carbothermal reduction method using sol-gel process, and organosilicon pyrolysis method have been developed. Due to the problems of the synthesis process, a mass production system cannot be established.

In addition, in the prior art, a deposition process for depositing SiC on graphite parts using a silicon carbide precursor such as _{methyltrichlorosilane (MTS, CH 3} SiCl _{3 ) gas in a deposition chamber was performed, but in this case, thick deposition was performed.} A technology for uniformly forming a layer has been developed, and there is no technology capable of directly manufacturing a high-purity SiC powder phase using a vapor deposition method.

Korean Patent No. 10-0827970

In order to solve the problems of the prior art as described above, a method for producing high-purity silicon carbide powder or granular (hereinafter referred to as powder phase) raw material having a size and economic feasibility suitable for producing a silicon carbide (SiC) single crystal by the PVT method. intended to provide

In addition, by using the deposition process used in the conventional SiC thick film manufacturing process, it is possible to manufacture a powdery raw material rather than a thick film process, so that a variety of particle size distributions in the range of several millimeters to several tens of microns required for SiC single crystal growth and high purity SiC powder An object of the present invention is to provide a method for producing a high-purity silicon carbide powdery raw material capable of producing a phase.

The technical problems to be solved by the invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the description below. will be able

The method for manufacturing a high-purity silicon carbide powder material of the present invention comprises: a first step of depositing silicon carbide (SiC) on a deposition table of a graphite material using a silicon carbide (SiC) precursor as a raw material in a deposition chamber; a second step of recovering the deposition zone on which the silicon carbide is deposited; a third step of separating the powder phase of the deposited silicon carbide grains or powder from the recovered deposition stage; a fourth step of adjusting the size of the separated silicon carbide powder phase; and a fifth step of purifying by removing impurities from the size-controlled silicon carbide powder phase.

By means of solving the above problems, the method for producing a high-purity silicon carbide powder raw material of the present invention has the effect of enabling mass production of a high-purity SiC powder phase for single crystal growth with a particle size according to the purpose of the user.

In addition, it is not necessary to separately add a process for additionally growing SiC powder with a small particle size of about a few microns or to manufacture at a high price with a low-yield process, thereby increasing the efficiency of the operation.

In addition, since SiC powder having a wide particle size distribution for controlling the filling rate suitable for single crystal growth can be easily obtained, there is an effect of making single crystal growth more economical and high quality production possible.

1 is a diagram showing silicon carbide deposition according to the present invention.
2 is a diagram of another embodiment showing the silicon carbide deposition of the present invention.
3 is a view showing a form using an intermediate layer when depositing silicon carbide according to the present invention. (In FIG. 3, the rough part is the part where powdery silicon carbide is deposited, and the smooth part is the overlapped and not deposited part.)

Specific details including the problems to be solved for the present invention as described above, means for solving the problems, and the effects of the invention are included in the embodiments and drawings to be described below. Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings.

Hereinafter, a method for manufacturing the high-purity silicon carbide powdery raw material will be described with reference to drawings and examples.

1 is a diagram showing silicon carbide deposition of the present invention, FIG. 2 is a diagram of another embodiment showing silicon carbide deposition of the present invention, and FIG. 3 is a diagram showing a form using an intermediate layer during silicon carbide deposition of the present invention. .

First, in the first step, silicon carbide (SiC) is deposited using a silicon carbide (SiC) precursor as a raw material in a deposition chamber. Specifically, silicon carbide is deposited using a silicon carbide precursor as a raw material in a deposition chamber using a deposition table made of graphite, which is a substrate to be deposited.

The deposition stage includes a graphite rod and a graphite structural material. The graphite rod is used as a heat source by flowing an electric current, and the graphite structural material allows current to flow but a powder phase is deposited as a non-heat source.

Graphite rods and graphite structural materials for the deposition use extruded graphite or isotropic graphite for resistance heating.

The deposition table may use not only graphite, isotropic graphite, extruded graphite for resistance heating, but also carbon fiber insulation and flexible graphite sheet, but it may be difficult to deposit a large amount due to the difficulty in maintaining strength due to the characteristics of the material.

In addition, the deposition table may provide an intermediate layer on the surface. The intermediate layer uses a carbon fiber insulating material (Felt) or a flexible graphite sheet to facilitate separation between the SiC powder deposition and the graphite deposition table.

The deposition is preferably performed for 5 to 25 hours at a process temperature of 1200 to 2100° C. while flowing a current of 0.05 to 300 A/cm 2 .

When an electric current flows through the deposition table, which is a substrate on which SiC deposition is performed, a SiC seed is generated or becomes difficult to grow, so that a smooth deposition is not formed.

Therefore, when an electric current is passed through, deposition proceeds centering on the already grown nuclei, so that it grows in the shape of a bunch of grapes.

Such growth is preferably carried out within the above range because the shape of the particles changes depending on the current and temperature.

More specifically, in the case of the same current, the higher the temperature and the higher the current density in the case of the same temperature, the more nucleation and growth are suppressed as shown in FIG.

In addition, in the case of the same current, the lower the temperature and the lower the current density in the case of the same temperature, the more nucleation and growth are promoted, as shown in FIG. 2 , so that the deposition in the form of a lump having a larger particle size is made.

Therefore, it is preferable to perform deposition at a temperature and current within the ranges given above in consideration of the deposition rate and particle size.

Next, in the second step, the deposition zone on which the silicon carbide is deposited is recovered. Specifically, the graphite material deposition stage (including SiC powder product and thick film) on which SiC is deposited in the chamber is recovered.

Next, in the third step, the deposited silicon carbide powder phase is separated from the recovered deposition stage. Specifically, the powder phase of the deposited SiC grains or powder is separated from the recovered deposition stage.

At this time, as shown in FIG. 3 , when an intermediate layer is included in the deposition table, separation (rough side is the powder-like side, smooth side is the back side) can be easily performed.

Next, in the fourth step, the size of the separated silicon carbide powder phase is adjusted. Specifically, the size suitable for using the separated silicon carbide powder phase as a raw material is adjusted according to the purpose of the user.

That is, it is preferable to adjust the silicon carbide powder phase to a size suitable for use as a raw material for producing a single crystal by a PVT (Sublimation Recrystallization Method, Physical Vapor Transport method) method.

The fourth step includes a 4-1 step of classifying the size of the silicon carbide powder phase, and a 4-2 step of pulverizing the silicon carbide powder phase according to the classification.

In the step 4-1, the size of the SiC powder phase is classified according to the standard, and in the step 4-2, the powder phase having large particles among the classification objects is pulverized to adjust the size.

It is preferable that the size-adjusted particles have a size of 50 μm to 15 mm.

Next, in the fifth step, impurities are removed from the size-controlled silicon carbide powder phase and purified. Specifically, impurities such as excess carbon (graphite), SiO2, and metal powder are removed from the silicon carbide powder phase whose size is adjusted for purification.

In more detail, the purification of the silicon carbide powder phase is carried out by heat treatment in at least one of an oxidizing atmosphere, a neutral atmosphere, and a reducing (hydrogen) atmosphere to gasify and remove the remaining carbon and silicon carbide using a single or complex acid At least one of the steps of removing metal impurities.

Refining through heat treatment in an oxidizing atmosphere can remove carbon by oxidizing carbon at a high temperature in the atmosphere. The heat treatment for the high temperature is preferably 500 to 950 ℃. When the heat treatment is performed at the above temperature, it can be confirmed that weight loss occurs, and thus it can be seen that residual impurities can be removed.

In addition, purification through heat treatment can be performed even in a neutral atmosphere or a reducing (hydrogen) atmosphere.

(Formula 1)

C + 2H₂ →CH₄

In particular, carbon, which is an impurity, can be removed by hydrogenating carbon through the reaction shown in Chemical Formula 1 above.

Factors involved in the reaction include H2 partial pressure, the degree and temperature of graphite. High H2 partial pressure and low graphitization promote methanogenic reaction. In addition, although the above reaction is basically an exothermic reaction, it is preferable to maintain a high temperature in order to obtain a high reaction rate. The heat treatment for the high temperature is preferably 500 to 950 ℃.

In addition, silicon carbide and metal impurities can be removed using a single or complex acid. Specifically, after adding the purification target to a solution of a single or complex acid (nitric acid, hydrochloric acid, hydrofluoric acid, etc.), stirring at room temperature for 2 to 3 hours, filtering it under reduced pressure with a Buchner funnel, and heating it to a temperature of 70 ° C in an oven 16 Purification is carried out by drying time.

The high-purity silicon carbide powder phase prepared as described above has a purity of at least 5N (five-nine, 99.999%) or more, and has a purity of 5N5 to 6N or more according to the purification process.

As such, those skilled in the art to which the present invention pertains will understand that the above-described technical configuration of the present invention may be implemented in other specific forms without changing the technical spirit or essential characteristics of the present invention.

Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the following claims rather than the above detailed description, and the meaning and scope of the claims and their All changes or modifications derived from the concept of equivalents should be construed as being included in the scope of the present invention.

Claims (7)

a first step of depositing silicon carbide (SiC) on a deposition table made of graphite using a silicon carbide (SiC) precursor as a raw material in a deposition chamber;
a second step of recovering the deposition zone on which the silicon carbide is deposited;
a third step of separating the powder phase of the deposited silicon carbide grains or powder from the recovered deposition stage;
a fourth step of adjusting the size of the separated silicon carbide powder phase;
A fifth step of purifying by removing impurities from the size-adjusted silicon carbide powder phase, high-purity silicon carbide powder raw material manufacturing method comprising the The method of claim 1,
The deposition is a high-purity silicon carbide powder raw material manufacturing method, characterized in that at a process temperature of 1200 to 2100° C., flowing a current of 0.05 A/cm 2 or more to the deposition table of graphite material for 5 to 25 hours The method of claim 1,
The deposition table is made of graphite material,
High-purity silicon carbide powder raw material manufacturing method comprising a graphite rod used as a heat source and a graphite structural material 4. The method of claim 3,
The graphite rod and graphite structural material is a high-purity silicon carbide powder raw material manufacturing method, characterized in that using at least any one of extruded graphite for resistance heating, isotropic graphite, carbon fiber insulation, and flexible graphite sheet 4. The method of claim 3,
The deposition table further comprises an intermediate material,
The intermediate material is a high-purity silicon carbide powder raw material manufacturing method, characterized in that using at least one of a carbon fiber insulation material and a flexible graphite sheet The method of claim 1,
Adjusting the size of the silicon carbide powder phase,
Step 4-1 of classifying the size of the silicon carbide powder phase;
A high-purity silicon carbide powder raw material manufacturing method comprising; a 4-2 step of pulverizing the silicon carbide powder phase according to the classification The method of claim 1,
The purification of the silicon carbide powder phase,
gasifying and removing carbon remaining by heat treatment in at least one of an oxidizing atmosphere, a neutral atmosphere, and a reducing atmosphere; and
removing silicon carbide and metal impurities using a single or complex acid; High-purity silicon carbide powdery raw material manufacturing method comprising at least one of

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