KR102496031B1 - Silicon carbide powder, method of fabrication the same and silicon carbide single crystal - Google Patents

Abstract

A method for producing silicon carbide powder according to an embodiment includes forming a mixture by mixing a carbon source and a silicon source; heating the mixture to form a first silicon carbide powder; and grain-growing the first silicon carbide powder to form a second silicon carbide powder, wherein the grain-growing the silicon carbide powder comprises: heating to a first growth temperature; maintaining the first growth temperature; heating from the first growth temperature to a second growth temperature; and maintaining the second growth temperature.

Description

Silicon carbide powder, manufacturing method thereof, and silicon carbide single crystal

The present invention relates to silicon carbide powder, a manufacturing method thereof, and a silicon carbide single crystal.

In general, silicon carbide powder has recently been used as a semiconductor material for various electronic devices and purposes. Silicon carbide powder is particularly useful due to its high physical strength and high resistance to chemical attack. Silicon carbide powder also exhibits radiation hardness, relatively wide band gap, high saturated electron drift velocity, high operating temperature, and spectral blue, violet, and ultraviolet ) have excellent electronic properties, including absorption and emission of high-energy protons in the region.

There are various methods for producing the silicon carbide powder, and as an example, an Acheson method, a carbon thermal reduction method, a liquid phase polymer pyrolysis method, or a CVD method are used. In particular, the high-purity silicon carbide powder synthesis method uses a liquid polymer pyrolysis method or a carbon thermal reduction method.

That is, silicon carbide powder may be synthesized by mixing materials of a carbon source and a silicon source, and proceeding with a carbonization process and a synthesis process for the mixture.

Such silicon carbide powder may be used as a growth raw material when growing a silicon carbide single crystal, and defects of the silicon carbide single crystal may be related to the characteristics of the raw material silicon carbide powder.

Accordingly, there is a demand for a silicon carbide powder for single crystal growth capable of reducing defects in silicon carbide single crystals.

The present invention is to provide a silicon carbide powder having an improved angle of repose and a manufacturing method thereof.

A method for producing silicon carbide powder according to an embodiment of the present invention includes forming a mixture by mixing a carbon source and a silicon source; heating the mixture to form a first silicon carbide powder; and grain-growing the first silicon carbide powder to form a second silicon carbide powder, wherein the grain-growing the silicon carbide powder comprises: heating to a first growth temperature; maintaining the first growth temperature; heating from the first growth temperature to a second growth temperature; and maintaining the second growth temperature.

When the silicon carbide powder according to the embodiment of the present invention is filled into the crucible as a raw material for single crystal growth, the surface of the silicon carbide powder filled into the crucible can be flattened as the angle of repose decreases.

Accordingly, as the temperature gradient between the silicon carbide powder and the seed crystal becomes uniform, a silicon carbide single crystal having improved quality can be manufactured.

1 is a diagram showing a process flow diagram of a method for manufacturing silicon carbide powder according to an embodiment of the present invention.
2 and 3 are graphs showing the temperature range of the grain growth process of the silicon carbide powder of the present invention.
4 to 7 are views showing scanning electron microscope (SEM) photographs of silicon carbide powders according to Examples of the present invention and Comparative Examples.
8 is a view showing a single crystal growth apparatus using silicon carbide powder according to an embodiment of the present invention.
9 and 10 are diagrams illustrating monoscopic sections of silicon carbide according to an embodiment of the present invention and a comparative example.

In the description of the embodiments of the present invention, each layer (film), region, pattern or structure is "on" or "under/under" the substrate, each layer (film), region, pad or pattern. The description of "under" includes all forms formed directly or through another layer. The criteria for upper/upper or lower/lower of each layer will be described based on drawings.

In the drawings, the thickness or size of each layer (film), region, pattern, or structure may be modified for clarity and convenience of explanation, and thus does not entirely reflect the actual size.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 1, a method for manufacturing silicon carbide powder according to an embodiment of the present invention includes mixing a carbon source and a silicon source (ST10), preparing a first silicon carbide powder (ST20), and preparing a second silicon carbide powder. It may include a step (ST30).

In the step of mixing the carbon source and the silicon source (ST10), a mixed powder may be formed by mixing the carbon source (C source) and the silicon source (Si source).

The silicon source may include various materials capable of providing silicon. For example, the silicon source may include silica. In addition to silica, silica powder, silica sol, silica gel, quartz powder, etc. may be used as the silicon source. However, the embodiment is not limited thereto, and an organosilicon compound containing silicon may be used as a silicon source.

In addition, the carbon source may include a solid carbon source or an organic carbon compound.

The solid carbon source may include at least one of graphite, carbon black, carbon nano tube (CNT), and fullerene (C ₆₀ ).

Examples of the organic carbon compounds include phenol, franc, xylene, polyimide, polyurethane, polyvinyl alcohol, polyacrylonitrile and It may include at least one of poly(vinyl acetate). In addition, cellulose, sugar, pitch, or tar may be included.

The carbon source and the silicon source may be mixed by a wet mixing process using a solvent or a dry mixing process without using a solvent.

The silicon source and the carbon source are mixed by a method such as a ball mill or an attrition bill to recover mixed powder. The mixed powder can be recovered by being sieved by a sieve.

The silicon source and the carbon source may be mixed at a constant ratio. For example, a molar ratio of carbon included in the carbon source to silicon included in the silicon source (hereinafter referred to as “molar ratio of carbon to silicon”) may be about 1:1.5 to about 1:3. When the molar ratio of carbon to silicon exceeds about 3, the amount of carbon is large and the amount of residual carbon that does not participate in the reaction and remains increases, thereby reducing the recovery rate. In addition, when the molar ratio of carbon to silicon is less than about 1.5, the amount of silicon remaining without participating in the reaction increases due to the large amount of silicon, which may lower the recovery rate. That is, the molar ratio of carbon to silicon is determined in consideration of the recovery rate.

At this time, considering that the silicon source volatilizes in a gaseous state at a high temperature in the reaction step, the molar ratio of carbon to silicon may be about 1.8 to about 2.7.

In the step of preparing the first silicon carbide powder (ST20), the mixed powder may be heated to form the first silicon carbide powder.

The step of preparing the first silicon carbide powder may be divided into a carbonization process and a synthesis process.

In the carbonization process, carbon may be generated by carbonizing the organic carbon compound. The carbonization process may be performed at a temperature of about 600 °C to about 1200 °C. In more detail, the carbonization process may be performed at a temperature of about 800 °C to about 1100 °C. When the solid carbon source is used as the carbon source, the carbonization process may not proceed.

After that, the synthesis process proceeds. In the synthesis process, the silicon source and the solid carbon source react or the silicon source and the organic carbon compound react to form silicon carbide powder according to the overall reaction formula of reaction formula 3 according to the steps of reaction formulas 1 and 2 below. there is.

[Scheme 1]

SiO2(s) + C(s) -> SiO(g) + CO(g)

[Scheme 2]

SiO(g) + 2C(s) -> SiC(s) + CO(g)

[Scheme 3]

SiO2(s) + 3C(s) -> SiC(s) + 2CO(g)

The heating temperature may be about 1300° C. or higher so that the reaction as described above can occur smoothly. In this case, by setting the heating temperature to about 1300° C. to about 1700° C., the prepared silicon carbide powder may have a low-temperature stable beta phase. This beta phase is composed of fine particles and can improve the strength and the like of the silicon carbide powder.

The first silicon carbide powder having a particle size of about 0.1 μm to about 0.9 μm may be manufactured by the manufacturing process as described above.

In the step of preparing the second silicon carbide powder (ST30), the first silicon carbide powder may be reacted at a constant temperature. In detail, the first silicon carbide powder may be heated at a constant temperature to cause grain growth of the first silicon carbide powder.

Specifically, the second silicon carbide powder may be prepared by reacting the first silicon carbide powder at a temperature of about 1800 °C to about 2300 °C. That is, the second silicon carbide powder may be prepared by grain growth by reacting the primary silicon carbide powder at a temperature of about 1800 ° C to about 2300 ° C.

The step of grain-growing the first silicon carbide powder includes heating to a first growth temperature, maintaining the first growth temperature, heating from the first growth temperature to the second growth temperature, and It may include maintaining the growth temperature.

2 is a graph showing a temperature range during grain growth of the first silicon carbide powder.

Referring to FIG. 2 , in order to grain grow the first silicon carbide powder, it may be heated to 1 growth temperature (T1). Subsequently, a first maintenance period M1 in which the first growth temperature T1 is maintained for a predetermined time may be set. Subsequently, the first growth temperature T2 may be heated to the second growth temperature T2. Subsequently, a second maintenance period M2 in which the second growth temperature T2 is maintained for a predetermined time may be set.

That is, a section in which the first silicon carbide powder is heated to a constant temperature and a section maintained at a constant temperature may be repeated.

The second growth temperature T2 may be higher than the first growth temperature T1. Also, a difference (T2-T1) between the first growth temperature T1 and the second growth temperature T2 may be about 20°C to about 200°C.

When the difference (T2-T1) between the first growth temperature T1 and the second growth temperature T2 is less than about 20° C., process efficiency may decrease as the time to reach the final growth temperature increases. . In addition, when the difference (T2-T1) between the first growth temperature (T1) and the second growth temperature (T2) exceeds about 200 ° C., as the grain growth section of the first silicon carbide powder increases or decreases, The particle size of the silicon carbide powder can be increased.

The time of the first maintenance period M1 and the second maintenance period M2 may be about 10 minutes to about 100 minutes.

When the first maintaining period M1 and the second maintaining period M2 are less than about 10 minutes, the dispersion of grain-grown silicon carbide powder may increase, and particle uniformity may deteriorate. In addition, when the first maintaining period M1 and the second maintaining period M2 exceed about 100 minutes, process efficiency may decrease as the time to reach the final growth temperature increases.

The times of the first maintenance period M1 and the second maintenance period M2 may be the same, similar or different within the above range. In detail, in consideration of the desired particle size and distribution of the silicon carbide powder, the time of the first maintaining period M1 and the second maintaining period M2 can be controlled identically, similarly or differently within the above range. there is.

Referring to FIG. 3, the temperature range during grain growth of the first silicon carbide powder may further include heating from the second growth temperature to a third growth temperature and maintaining the third growth temperature. can

That is, the second growth temperature T2 can be heated to the third growth temperature T3, and a third maintenance period M3 in which the third growth temperature T3 is maintained for a certain period of time can be set. there is.

The third growth temperature T3 may be greater than the first growth temperature T1 and the second growth temperature T2. Also, a difference (T3-T2) between the third growth temperature T3 and the second growth temperature T2 may be about 20°C to about 200°C.

When the difference (T3-T2) between the second growth temperature T2 and the third growth temperature T3 is less than about 20° C., process efficiency may decrease as the time to reach the final growth temperature increases. . In addition, when the difference (T3-T2) between the second growth temperature (T2) and the third growth temperature (T3) exceeds about 200 ° C., as the grain growth section of the first silicon carbide powder increases or decreases, The particle size of the silicon carbide powder can be increased.

In addition, the difference (T3-T2) between the second growth temperature (T2) and the third growth temperature (T3) is the difference (T2-T1) between the first growth temperature (T1) and the second growth temperature (T2). ) and may be the same, similar or different.

For example, a difference (T3-T2) between the second growth temperature (T2) and the third growth temperature (T3) and a difference (T2) between the first growth temperature (T1) and the second growth temperature (T2) -T1) may be the same, similar or different from each other within the range of about 20 ° C to about 200 ° C.

In detail, the difference (T3-T2) between the second growth temperature (T2) and the third growth temperature (T3) and the first growth temperature (T1) in consideration of the particle size and distribution of the desired silicon carbide powder ) and the second growth temperature T2 (T2-T1) may be the same, similar or different from each other.

The time of the third maintenance period M3 may be about 10 minutes to about 100 minutes.

When the third holding period M3 is less than about 10 minutes, the dispersion of grain-grown silicon carbide powder increases, and particle uniformity may deteriorate. In addition, when the third holding period M3 exceeds about 100 minutes, process efficiency may decrease as the time to reach the final growth temperature increases.

The times of the first maintenance period M1, the second maintenance period M2, and the third maintenance period M3 may be the same, similar or different within the above range. Specifically, in consideration of the desired particle size and distribution of the silicon carbide powder, the times of the first maintaining period M1, the second maintaining period M2, and the third maintaining period M3 are within the above range. In the same, similar or different control can be.

2 and 3, the first and second growth temperatures, the first, second, and third growth temperatures, the first and second holding periods, and the first, second, and third holding periods have been described, but the embodiment is not limited thereto, It goes without saying that additional growth temperatures and holding periods, such as the fourth growth temperature and the fourth holding period, may be further set in consideration of the desired particle size and distribution of the silicon carbide powder.

According to the grain growth process, the first silicon carbide powder may be grain grown to form a second silicon carbide powder. Specifically, the particle diameter of the second silicon carbide powder may be about 200 μm to about 500 μm. In addition, the second silicon carbide powder may include alpha-phase silicon carbide powder. In detail, the second silicon carbide powder may include at least one of alpha-phase silicon carbide powder and beta-phase silicon carbide powder.

The silicon carbide powder prepared according to the embodiment of the present invention can be applied when growing a silicon carbide single crystal. In addition, the silicon carbide powder prepared according to the embodiment may reduce the angle of repose of the silicon carbide powder when the silicon carbide powder is filled in a crucible or the like.

Here, the angle of repose means an angle formed when the powder is dropped, and may be determined according to particle characteristics of the powder. That is, a decrease in the angle of repose may mean that the surface of the powder filled in the crucible or the like is gradually flattened, and an increase in the angle of repose may mean that the surface of the powder filled in the crucible or the like is gradually not flattened.

That is, as the angle of repose of the silicon carbide powder applied as a raw material during the growth of silicon carbide single crystal decreases, the height of the raw material filled in the crucible from the surface to the seed crystal becomes uniform as a whole, and the temperature between the raw material and the seed crystal becomes uniform Since the gradient can be made uniform, the quality of the silicon carbide single crystal produced thereby can be improved.

For example, the angle of repose of the silicon carbide powder may be about 30° or less. Specifically, the angle of repose of the silicon carbide powder may be about 20° or less. More specifically, the angle of repose of the silicon carbide powder may be about 10° to about 20°.

Hereinafter, the present invention will be described in more detail through a manufacturing method of silicon carbide powder according to Examples and Comparative Examples. These embodiments are only presented as examples in order to explain the present invention in more detail. Therefore, the present invention is not limited to these examples.

Example 1

A mixture was formed by mixing 10 g of fumed silica and 10 g of a phenolic resin. In addition, 6 kg of the raw material was charged into a 500φ×100H crucible.

The mixing device was a device equipped with an impeller, and the mixture was mixed by operating at an impeller speed of 200 rpm for 5 hours.

Thereafter, the temperature of the mixture was subjected to a carbonization process at a temperature of about 850 ° C. for 2 hours at a temperature of 3 ° C. / min, and a synthesis process at a temperature of about 1650 ° C. for about 3 hours at a temperature of 5 ° C. / min. Through this process, a first silicon carbide powder having a fine-grained 3C crystal phase was prepared.

Subsequently, the primary silicon carbide powder was grain grown in an argon (Ar) atmosphere at a temperature of about 1800° C. to about 2300° C. to prepare a second silicon carbide powder.

At this time, the grain growth process was performed by heating at a temperature of about 1800 ° C to about 100 ° C and maintaining the temperature at the heating temperature for about 1 hour, repeating the process to a temperature of about 2300 ° C.

Next, the prepared second silicon carbide powder was filled into a crucible, and the angle of repose of the filled silicon carbide powder was measured.

Example 2

The grain growth process was performed in the same manner as in Example 1 except that the process of heating from about 1800 ° C to about 100 ° C and maintaining the temperature for about 30 minutes at the heating temperature was repeated to a temperature of about 2300 ° C. After preparing the second silicon carbide powder, the prepared second silicon carbide powder was filled in a crucible, and the angle of repose of the filled silicon carbide powder was measured.

Example 3

The grain growth process is the same as in Example 1 except that the process of heating from about 1800 ° C to about 50 ° C and maintaining the temperature for about 30 minutes at the heating temperature is repeated until the temperature of about 2300 ° C. After preparing the second silicon carbide powder, the prepared second silicon carbide powder was filled in a crucible, and the angle of repose of the filled silicon carbide powder was measured.

Comparative Example 1

A second silicon carbide powder was prepared in the same manner as in Example 1, except that the grain growth process was heated from about 1800 ° C to about 2300 ° C at one time and then maintained at a temperature of about 2300 ° C for about 5 hours. After that, the prepared second silicon carbide powder was filled in a crucible, and the angle of repose of the filled silicon carbide powder was measured.

Particle size (㎛) scatter angle of repose (°) Example 1 258 2.6 16 Example 2 220 3.7 14 Example 3 260 2.4 18 Comparative Example 1 267 2.5 37

Referring to Table 1 and FIGS. 4 to 7 , it can be seen that the angle of repose of the silicon carbide powder according to Examples is reduced compared to that of the silicon carbide powder according to Comparative Example.

In addition, it can be seen that the particle size and distribution of the silicon carbide powder according to Examples are similar to those of the silicon carbide powder according to Comparative Example.

In detail, referring to FIG. 4 (comparative example), when the silicon carbide powder is filled in the crucible as the number of silicon carbide powders being necked increases, the phenomenon of entanglement of silicon carbide powders with each other, this necking phenomenon The angle of repose can be increased by

On the other hand, referring to FIG. 5 (Example 1), FIG. 6 (Example 2) and FIG. 7 (Example 3), the phenomenon of entanglement of silicon carbide powders, that is, the necking silicon carbide powders is reduced , Accordingly, when the silicon carbide powder is filled into the crucible, the angle of repose may be reduced due to this necking phenomenon.

Accordingly, as the angle of repose decreases, the surface of the silicon carbide powder filled in the crucible flattens, and the temperature gradient between the silicon carbide powder and the seed crystal becomes uniform, thereby producing a silicon carbide single crystal with improved quality. .

Hereinafter, referring to FIG. 8, a method for growing a silicon carbide single crystal according to an embodiment will be described.

A method for growing a single crystal of silicon carbide according to an embodiment of the present invention includes preparing silicon carbide powder for single crystal growth as a raw material, filling a crucible with the silicon carbide powder, putting the crucible into a single crystal growing apparatus, and the above steps. It may include heating the single crystal growing apparatus.

Since the step of preparing the silicon carbide powder for single crystal growth is the same as the previously described silicon carbide powder manufacturing method, that is, the second silicon carbide powder manufacturing method, the following description is omitted.

Subsequently, the crucible 100 may be filled with the silicon carbide powder 200 for single crystal growth, and the crucible accommodating the silicon carbide powder may be put into the single crystal growth apparatus 1000 .

Subsequently, in the step of heating the single crystal growth apparatus, heat may be applied to the crucible 100 . Although not shown in the drawings, a heating induction unit may be located outside the crucible 100 to apply heat to the crucible 100 . The crucible 100 may self-heat by the heat induction part. The heating induction unit may be, for example, a high-frequency induction coil. The crucible 100 may be heated by flowing a high frequency current through a high frequency induction coil. That is, the raw material accommodated in the crucible 100 can be heated to a desired temperature.

Accordingly, the silicon carbide powder accommodated in the crucible 100 sublimes and can move to the seed crystal 400 in the crucible 100, and the ingot 410 can grow from the seed crystal 400.

Specifically, a temperature gradient having different heating temperature regions is formed at the top and bottom of the crucible 100 by the heat induction part. Due to this temperature gradient, sublimation of the silicon carbide powder occurs, and the sublimated silicon carbide gas moves to the surface of the seed crystal 400 having a relatively low temperature. Due to this, the silicon carbide gas may be recrystallized and grown into an ingot 410 .

That is, the silicon carbide single crystal manufactured according to the embodiment of the present invention can reduce the size of the angle of repose (θ) of the silicon carbide powder 200 for single crystal growth filled in the crucible 100, and thus, silicon carbide Since the temperature gradient between the powder and the seed crystal becomes uniform, it is possible to manufacture a silicon carbide single crystal of improved quality.

Hereinafter, the present invention will be described in more detail through a manufacturing method of silicon carbide powder according to Examples and Comparative Examples. These embodiments are only presented as examples in order to explain the present invention in more detail. Therefore, the present invention is not limited to these examples.

Example 4

Silicon carbide single crystals were grown by the single crystal growing process using the silicon carbide powders of Examples 1 to 3.

Comparative Example 2

A silicon carbide single crystal was grown using the silicon carbide powder of Comparative Example 1 by the above single crystal growth process.

Defect Density (ea/cm2) Height difference of raw material (mm) Example 4 61 3 Comparative Example 2 640 30

Referring to Table 2, it can be seen that the defect density of the silicon carbide single crystal according to Example 4 is smaller than that of the silicon carbide single crystal according to Comparative Example 2.

In addition, in Example 4, it can be seen that the height deviation of the raw material filled in the crucible, that is, the silicon carbide powder for single crystal growth is smaller than that of Comparative Example 2.

That is, it can be seen that the silicon carbide single crystal according to FIG. 10 (Example 4) has improved quality with reduced defects compared to FIG. 9 (Comparative Example 2).

The features, structures, effects, etc. described in the foregoing embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. illustrated in each embodiment can be combined or modified with respect to other embodiments by those skilled in the art in the field to which the embodiments belong. Therefore, contents related to these combinations and variations should be construed as being included in the scope of the present invention.

In addition, although the embodiments have been described above, these are merely examples and do not limit the present invention, and those of ordinary skill in the field to which the present invention belongs can exemplify the above to the extent that does not deviate from the essential characteristics of the present embodiment. It will be seen that various variations and applications that have not been made are possible. For example, each component specifically shown in the embodiments can be modified and implemented. And differences related to these variations and applications should be construed as being included in the scope of the present invention as defined in the appended claims.

Claims (13)

mixing a carbon source and a silicon source to form a mixture;
heating the mixture to form a first silicon carbide powder having a particle size of 0.1 μm to 0.9 μm; and
Grain growth of the first silicon carbide powder to form a second silicon carbide powder,
The step of grain-growing the silicon carbide powder,
heating to a first growth temperature;
maintaining the first growth temperature;
heating from the first growth temperature to a second growth temperature;
maintaining the second growth temperature;
heating from the second growth temperature to a third growth temperature; and
maintaining the third growth temperature; Including more,
The second growth temperature is greater than the first growth temperature,
The third growth temperature is greater than the first growth temperature and the second growth temperature,
The difference between the first growth temperature, the second growth temperature, and the third growth temperature is 20 ℃ to 200 ℃ silicon carbide powder manufacturing method. delete According to claim 1,
The first growth temperature, the second growth temperature and the third growth temperature are maintained for 10 minutes to 100 minutes. According to claim 1,
Wherein the first silicon carbide powder is grain-grown at a temperature of 1800 ° C to 2300 ° C. delete According to claim 1,
The difference between the first growth temperature and the second growth temperature is equal to the difference between the second growth temperature and the third growth temperature. delete delete According to claim 1,
Wherein the first growth temperature, the second growth temperature, and the third growth temperature are maintained for the same amount of time. delete Preparing the silicon carbide powder prepared by any one of claims 1, 3, 4, 6, and 9;
filling a crucible with the silicon carbide powder;
putting the crucible into a single crystal growing apparatus; and
Including the step of heating the single crystal growing device,
The silicon carbide single crystal manufacturing method wherein the angle of repose of the silicon carbide powder filled in the crucible is 10 to 20 °. According to claim 11,
The silicon carbide single crystal manufacturing method in which the particle size of the silicon carbide powder is 200 μm to 500 μm. According to claim 11,
The silicon carbide powder is a method for producing a silicon carbide single crystal comprising an alpha-phase silicon carbide powder.

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