KR102187817B1 - Recycling method of SiC by-product from the deposition process into the source of single crystal - Google Patents

Abstract

The present invention relates to a method of regenerating a silicon carbide by-product generated in a deposition process as a single crystal raw material, and more particularly, after completing the deposition process using a silicon carbide precursor as a raw material in a deposition chamber, silicon carbide in the chamber is deposited. Retrieving the part; Collecting deposited silicon carbide from the recovered part; Selecting silicon carbide of a size suitable for a PVT method single crystal raw material from the collected silicon carbide; And it provides a method for regenerating the silicon carbide by-product generated in the deposition process, characterized in that it comprises a step of refining the selected silicon carbide as a single crystal raw material.

Description

Recycling method of SiC by-product from the deposition process into the source of single crystal}

The present invention relates to a method of regenerating a silicon carbide by-product generated in a deposition process as a single crystal raw material, and more particularly, after completing the deposition process using a silicon carbide precursor as a raw material in a deposition chamber, silicon carbide in the chamber is deposited. Retrieving the part; Collecting deposited silicon carbide from the recovered part; Selecting silicon carbide having a size suitable for a PVT method single crystal raw material from the collected silicon carbide; And it provides a method for regenerating the silicon carbide by-product generated in the deposition process, characterized in that it comprises a step of refining the selected silicon carbide as a single crystal raw material.

SiC semiconductors have a large band gap (~3.2 eV) and have a reduction in semiconductor size due to high insulation breakdown, low power loss, and high temperature stability, so the temperature is much higher than the maximum operating temperature of the Si device of 250℃, which is 300℃ ~ 500℃. It is expected to be a solution due to the limitations of Si semiconductor characteristics as it can realize a device that can be used in the US and Japan. As a result, SiC single crystal substrates are focused on the US and Japan, and the product market using SiC substrates is expanding.

To this end, it is essential to develop efficiency and saving technologies in the electric energy field, which accounts for 30 to 35% of the total energy consumption. It is expected to reduce the semiconductor conversion loss from 12% to 3%. In addition, devices made of SiC are applied in applications with rated voltages of 1000V or higher, especially air conditioners, solar power generation, and inverters for electric vehicles. SiC single crystal wafers are expected to be applied to power devices such as electric vehicles and hybrid cars, energy conversion devices of solar devices, power devices for various electronic products requiring energy saving, LED/LD devices, and high-frequency devices. As the market is promising, development is actively underway, especially in advanced countries such as the United States, Japan, and Europe.

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

6-inch grade 4H-SiC single crystal growth (POSCO) and 6N5 grade high-purity powder technology development has been progressed through the WPM project of the Ministry of Knowledge Economy started in 2009, “Ultra-high purity SiC material”. It is in a situation where it has a close level of SiC single crystal manufacturing technology.

SiC single crystals are usually manufactured by sublimation recrystallization (PVT; Physical Vapor Transport method) in which SiC powder is sublimated and then recrystallized on a seed crystal. At this time, the quality level such as particle size and purity of the SiC powder used is manufactured. Since it has a decisive influence on the quality of single crystal, it is necessary to manufacture high-purity powder.

In general, when a single crystal is grown using the PVT method, the larger the particle size of the raw material powder is, the more the packing density increases, which is advantageous for the growth of single crystals on the long axis, and the amount of sublimation is uniformly increased, so it is known to be advantageous for high quality single crystals.

In the case of SiC powder containing a large amount of impurities, various defects (pore, micropipe, dislocation, polytype, grain boundary) can be generated by the influence of impurities during the crystal growth process. As a result, there are problems such as damage to the material during processing of the material after the growth process, the formation of an uneven epitaxial film during epitaxial growth, a decrease in yield due to the occurrence of a leakage current during device formation, and a decrease in lifespan.

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 for the synthesis of high-purity and ultra-high purity SiC powder. Due to the problem of the synthesis process, it is not possible to establish a mass production system.

The ultra-high purity SiC powder developed as a WPM business realized 6N5 class high-purity powder, but it is not suitable as a SiC powder applied for RF devices, so the development of V-doped high-purity SiC powder as a strategic core material business is underway separately, and the recent business goal In order to achieve this, the need for N-free high-purity SiC powder is being raised. However, the high-quality powder for 6N5 single crystal growth developed as a WPM business has reached the level of commercialization, but it is required to propose a new method that can lower the process cost due to the high process cost.

Republic of Korea Patent Application No. 10-2014-0183368 Republic of Korea Patent Application No. 10-2013-0063427

The present invention was conceived to solve the problems of the prior art described above, and the present invention aims to make it possible to easily obtain a powder without performing a separate process for synthesizing a silicon carbide powder for single crystal growth of high difficulty. To do.

In addition, another object of the present invention is to make it possible to easily obtain a silicon carbide powder or pulverized product having a particle size required for single crystal growth.

In addition, another object of the present invention is to obtain a high-purity silicon carbide raw material from parts of a deposition equipment that are randomly discarded, and furthermore, to regenerate it as a raw material for single crystal growth.

In order to achieve the above object, the present invention comprises the steps of: after completing a deposition process using a silicon carbide precursor as a raw material in a deposition chamber, recovering a component on which silicon carbide is deposited in the chamber; Collecting deposited silicon carbide from the recovered part; Selecting silicon carbide having a size suitable for a PVT method single crystal raw material from the collected silicon carbide; And it provides a method for regenerating the silicon carbide by-product generated in the deposition process, characterized in that it comprises a step of refining the selected silicon carbide as a single crystal raw material.

It is preferable that the component is an electrode.

The electrode is preferably made of graphite for resistance heating.

In the step of collecting the deposited silicon carbide; it is preferable to collect the silicon carbide grown in the form of grains.

In the step of selecting the silicon carbide; it is preferable to select the silicon carbide grown in the form of grains having a particle size of at least 200 μm.

Selecting the silicon carbide; It is preferable to further include a step of pulverizing the selected silicon carbide afterwards.

Purifying the selected silicon carbide; is a step of gasifying residual carbon by heat treatment in an oxidizing atmosphere or a hydrogen atmosphere; is preferably.

The silicon carbide deposited on the component preferably has a purity of at least 6N (six-nine).

The step of purifying the selected silicon carbide; is preferably carried out in a rotary kiln.

The purification temperature is preferably in the range of 650 ~ 850 ℃.

In addition, the present invention provides a regenerated silicon carbide single crystal nucleus, characterized in that it is regenerated by the above-described regeneration method and purified to have a purity of at least 5N (five-nine) level.

According to the present invention as described above, it is not necessary to separately perform a process of synthesizing the silicon carbide powder for single crystal growth of high difficulty, and an effect of allowing the powder to be easily obtained can be expected.

In addition, it is possible to expect an effect of making it possible to easily obtain a silicon carbide powder or pulverized product having a particle size required for single crystal growth.

In addition, it is possible to obtain a high-purity silicon carbide raw material from parts of the deposition equipment that are randomly discarded, and furthermore, an effect of regenerating it as a raw material for single crystal growth can be expected.

Until now, powder prepared by synthesis has been used as a raw material for single crystal growth, but this is very expensive because it has to perform a high-level synthesis process, and the process is not simple because it must be synthesized in a certain size or more. It is possible to obtain purified raw materials of high purity without performing the same process, and because raw materials of the same quality can be secured at a very low price, as well as waste treatment costs can be reduced, a significant economic effect is expected. There has never been an attempt like this.

1 is a graph showing the sublimation amount according to the size of SiC.
2 is a TG-DSC analysis graph of silicon carbide powder according to an embodiment of the present invention.
3 is a conceptual diagram of a rotary kiln used in the process of refining silicon carbide powder according to an embodiment of the present invention.
4 is a microstructure photograph taken after decarburizing the silicon carbide powder obtained according to an embodiment of the present invention at each temperature.
5 is a graph of XRD analysis after decarburization of silicon carbide powder obtained according to an embodiment of the present invention at each temperature.
6 is a graph showing particle size analysis of silicon carbide powder obtained according to an embodiment of the present invention after decarburization at each temperature.
7 is an illustration of a PVT process profile for performing a single crystal growth process using the silicon carbide powder obtained according to an embodiment of the present invention after decarburization at each temperature.
FIG. 8 shows a single crystal photograph produced according to the PVT process profile according to FIG. 7 together with a single crystal photograph produced using the conventional synthesized powder and the powder obtained in the present invention.

An object of the present invention is to collect and purify high-purity raw materials deposited on waste deposition chamber components and recycle them as raw materials for single crystal growth.

In addition, although it is limited to the PVT method, it is not necessarily limited thereto, and may be applied to other single crystal process raw materials.

Recently, CVD-SiC polycrystalline materials, which are widely applied as members for Si semiconductor processing, are grown into polycrystals in a temperature range of 1500°C or lower, which is a raw material vaporized from a liquid source such as MTS to form a high-purity polycrystalline thick film/bulk. Is manufactured.

Meanwhile, the demand for solid SiC components such as SiC ring, SiC wafer, and SiC shower head is increasing in order to extend the lifespan and improve the yield of parts for MOCVD for LED and silicon Epi susceptors for semiconductor or plasma etcher chamber.

High-purity SiC incidental to the CVD-SiC process is coated on graphite members or heating elements, for example, and all graphite members and heating elements must be replaced after one operation.Therefore, tens of tons of high-purity SiC coated graphite per month are expensive Is paying and processing.

Due to the characteristics of the CVD method, high-quality SiC polycrystals of 7N or higher are coated, and a method of recycling them as a single crystal raw material by controlling the particle size by crushing and reprocessing graphite impurities has been proposed, leading to the present invention.

Using such recycled raw materials is expected to provide low-cost, high-purity powder for semi-insulated substrates for communication RF devices, including conventional conductive single crystals for high voltage power devices. In addition, according to the present invention, it is possible to supply high-purity single crystal raw materials using CVD-SiC facilities that are already built/operated, so technological progress that can change the market trend is expected, and the commercialization prospect is expected to be excellent.

Hereinafter, the present invention will be described in more detail with preferred embodiments.

The present invention comprises the steps of: after completing a deposition process using a silicon carbide precursor as a raw material in a deposition chamber, recovering a component on which the silicon carbide is deposited in the chamber; Collecting deposited silicon carbide from the recovered part; Selecting silicon carbide having a size suitable for a PVT method single crystal raw material from the collected silicon carbide; And purifying the selected silicon carbide.

(1) SiC deposits derived from CVD process

Development of a series of raw materials for refining high-purity CVD-SiC bulk/thick film/assembly powders from chemical vapor deposition (CVD) processes, which are commonly used as polycrystalline bulk materials, into single crystal growth powders, and verification of the raw materials as single crystal raw materials. It is an object of the present invention to perform SiC single crystal growth for. The above SiC deposited layer has a purity of at least 6N (six-nine).

Polycrystalline SiC deposits derived from the CVD process are deposited in various properties depending on their location, and SiC particles (grains) or dense deposition layers grow on a graphite member (for example, an electrode made of graphite for resistance heating). . In this way, the SiC particles or the graphite member on which the dense deposition layer has been grown is recovered, and SiC deposited material is collected therefrom.

(2) Collection (collection) of deposits

In the present invention, a series of process techniques have been proposed in which granular (particle) deposits that are relatively easy to collect compared to the dense vapor deposition layer of SiC are collected and applied as a single crystal raw material. However, although a dense deposition layer has a meaning of collection, there may be a problem in that impurities are mixed more than particles in the process of collecting them, and thus more resources may be put into the purification process. There is no restriction on the method of collection, but the granular deposits grown by the simplest mechanical method were collected.

(3) Grinding and particle size selection

As shown in FIG. 1, in the case of growing single crystals using the PVT method in general, the packing density increases as the particle size of the raw material powder becomes larger and uniform, which is advantageous for the growth of single crystals in the long axis and is sublimated. Since the amount is uniformly increased, it is advantageous for high quality single crystal.

However, as a raw material for single crystal growth, the concentration of impurities in the raw material may increase due to mixing of the pulverizing medium in the process of performing a mechanical pulverization process to control the particle size. For example, metal impurities are micropipes and screw dislocations inside the single crystal after growth. , As it causes defects such as basal dislocation, a processing process to lower the concentration of metallic impurities to 0.5ppm or less can be applied.

SiC synthesized by the CVD method is expected to have a low content of impurities in the process, but since it may exist as deposited on the graphite surface, carbon is present as an impurity. Therefore, the amount of SiO ₂ generated on the surface of SiC is determined. A process capable of decarburizing while minimizing should be attempted.

The particle size of the thus-collected or pulverized SiC deposit is selected to obtain particles having a size of at least 200 μm. Only when it is larger than the above size can the single crystal grow smoothly.

(4) Removal of residual carbon and impurities

SiC powder, which has been subjected to the primary heat treatment for purification (removal of residual carbon and impurities) after collection, has a size of about 10 µm. Since carbon was added in an excessive amount during the initial mixing, it was confirmed that all of them were synthesized as β-SiC except that a graphite peak appeared weakly around 26° on XRD.

(5) evaluation

TG-DSC analysis was performed to determine the appropriate temperature for removing graphite and is shown in FIG. 2. As a result of the analysis, it was confirmed that weight loss occurred around 700℃.

In addition, heat treatment was performed at temperatures of 700°C, 750°C, and 800°C, respectively, in order to know the exact temperature for removing graphite, and the microstructure was confirmed (FIG. 4), and XRD analysis was performed (FIG. 5). In addition, C/O analysis was conducted to determine whether carbon was removed.

As shown in FIG. 5, after immersing SiC powder in a crucible and heat-treating at 700° C. for 12 hours in an oxygen atmosphere, XRD analysis showed that graphite peaks remained around 26° on XRD. In the case of heat treatment by containing SiC powder in a crucible, carbon easily reacts with oxygen on the surface and is removed as CO gas, but the internal SiC powder does not contact oxygen, so carbon cannot be removed even when heat treatment is performed for a long time.

However, in the case of removing carbon using a rotary kiln shown in FIG. 3, since all SiC powder may be exposed to oxygen as the kiln rotates, it was effective to remove excess carbon.

As shown in Fig. 4, after heat treatment at 700℃, 750℃, and 800℃ for 4 hours using a rotary kiln to remove carbon, the shape and particle size changes of the particles were observed. SiC at 700℃, 750℃ and 800℃ No change in powder was observed. Here, heat treatment was performed in an oxygen atmosphere (in air), but heat treatment may be performed in a hydrogen atmosphere for decarburization. In this case, it is expected that decarburization will occur in the form of methane gas (CH ₄ ).

As shown in FIG. 5, it was confirmed that excess carbon was removed in all three conditions (700°C, 750°C, 800°C) as a result of XRD, and it was confirmed that the carbon content was reduced by about 4% in C/O analysis. (Table 1). As a result of the above experiment, it was confirmed that the case of 700°C and 4 hr was the condition to remove carbon with the least oxidation. That is, there was no need to raise the temperature to 750°C or 800°C. Nevertheless, the heat treatment temperature range of 650 ~ 850 ℃ was significant.

Sample name Test analysis items Test analysis result SiC Raw C(%) 32.50 O(%) 0.125 SiC 700℃ C(%) 29.76 O(%) 0.148 SiC 750℃ C(%) 29.76 O(%) 0.179 SiC 800℃ C(%) 29.67 O(%) 0.219

Using the thus purified SiC powder, a single crystal was grown through the schedule as shown in FIG. 7, and as a result, there was no difference from the single crystal prepared using the synthesized SiC powder, and the microstructure was also the same. It was also measured to have a purity of 5N or more.

FIG. 8 shows a single crystal photograph produced according to the PVT process profile according to FIG. 7 together with a single crystal photograph produced using the conventional synthesized powder and the powder obtained in the present invention. The left side is manufactured using synthetic powder, and the right side is manufactured using the powder obtained according to the present invention.

As shown, it is almost equal in appearance, and therefore, it is expected that a single crystal capable of being commercialized can be prepared using the powder obtained by the present invention.

Although the present invention has been described in more detail with reference to examples above, the present invention is not necessarily limited to these embodiments, and various modifications may be made without departing from the spirit of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention.

Claims (11)

After completing the deposition process using a silicon carbide precursor as a raw material in a deposition chamber by a CVD process, recovering a component on which the silicon carbide is deposited in the chamber;
Collecting silicon carbide grown in grain form from the recovered parts;
Selecting silicon carbide having a size suitable for a PVT method single crystal raw material by growing in the form of grains having a particle size of at least 200 μm from the collected silicon carbide; And
Purifying the silicon carbide selected in the rotary kiln;
Consists of including,
The part is an electrode rod made of graphite for resistance heating,
The silicon carbide deposited on the part has a purity of at least 6N (six-nine) level, and a silicon carbide by-product generated in the deposition process is recovered as a single crystal raw material, characterized in that to obtain silicon carbide having a purity of at least 5N. Way. delete delete delete delete The method of claim 1,
Selecting the silicon carbide; Since the
The method of regenerating the silicon carbide by-product generated in the deposition process as a single crystal raw material, further comprising: pulverizing the selected silicon carbide. The method of claim 1,
Purifying the selected silicon carbide;
The step of gasifying residual carbon by heat treatment in an oxidizing atmosphere or a hydrogen atmosphere; a method of regenerating a silicon carbide by-product generated in the deposition process as a single crystal raw material, characterized in that. delete delete The method of claim 1,
The refining temperature is in the range of 650 ~ 850 ℃ method for regenerating silicon carbide by-products generated in the deposition process as a single crystal raw material.

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