Crystal growth apparatus with enhanced crystal growth rate

Abstract

The present invention relates to a crystal growth apparatus with an enhanced crystal growth rate. More particularly, provided is a crystal growth apparatus comprising: a crucible including a seed crystal support; an insulating material surrounding the crucible; and a heat source disposed around the insulating material, wherein an air pocket is formed on the upper portion of an upper cover of the crucible.

Description

Crystal growth device with enhanced crystal growth rate

[0001] The present invention relates to a crystal growth apparatus with an enhanced crystal growth rate, and provides a crystal growth apparatus that can increase the crystal growth rate and improve the quality of the grown crystal by making the temperature gradient larger in the upper region of the crucible used for crystal growth.

[0002] Unlike system semiconductors or memory, which process and store information or signals, power semiconductors are core components that convert, store, distribute, and control power entering electronic devices. They are primarily used in inverters and converters for computers, home appliances, automobiles, solar power, and smart grids. In particular, demand is increasing significantly due to the Fourth Industrial Revolution, driven by the Internet of Things (IoT), autonomous driving, aerospace, and 5G. As power semiconductors possess such diverse application possibilities, active research and development is being conducted as a promising material.

[0003] Power semiconductor devices are broadly classified into silicon-based devices and compound-based devices. Among these, silicon (Si)-based devices are primarily used, while compound-based devices include silicon carbide (SiC), gallium nitride (GaN), and gallium oxide (Ga2O3) power semiconductor devices, which are recently on the rise. Compound-based devices possess wide band gap (WBG) characteristics, leading to their commercialization as power semiconductors. In particular, silicon carbide has a relatively advantageous position as a high-temperature, high-power semiconductor device due to its higher thermal conductivity, melting point, and wide band gap compared to conventional silicon.

[0004] Silicon carbide has various crystal structures (3C, 4H, 6H, 15R), among which 4H-SiC is mainly used in power devices. Depending on the doping, it exhibits n-type and p-type conductivity characteristics, and it is possible to fabricate inverted thermal substrates.

[0005] Methods for growing silicon carbide crystals include the PVT method (Physical Vapor Transport, sublimation method), the TSSG method (Top Seeded Solution Growth, solution growth method), and the HTCVD method (High Temperature Chemical Vapor Deposition, high temperature chemical vapor deposition method), and among these, SiC wafers grown using the PVT method have been commercialized.

[0006] The PVT method is a method of growing crystals by sublimating the lower SiC powder raw material at high temperatures and recrystallizing it at the upper SiC seed crystal. It is known that the temperature gradient inside the crucible and the flow of SiC-containing steam affect the growth rate and the quality of the grown crystals.

[0007] The driving force for crystal growth by the PVT method is the temperature gradient within the crucible, where the part near the crucible (the bottom, edge part of the raw powder) exhibits a relatively high temperature and the part far from the crucible (the top, center part of the raw powder) exhibits a relatively low temperature. During heating, sublimation begins first in the powder at the bottom and edge, and some silicon carbide vapor recrystallizes in the powder at the top center, where the temperature is relatively lower.

[0008] Previous studies reported a maximum growth rate of 1.7 mm / h for SiC single crystals with a diameter of 50 mm, but as they were communication papers, they lacked sufficient discussion regarding the operating mechanism or optimization process, and there was a problem with relatively poor crystal quality, particularly at the edges of the single crystal. Accordingly, there was a need to examine various single crystal growth apparatus structures for the growth of SiC single crystals by the high-speed PVT method and to explore conditions under which stable single crystals can be grown even during high-speed growth.

[0009] The present invention has been devised to solve the problems of the aforementioned prior art, and the objective of the present invention is to provide a crystal growth apparatus with an enhanced crystal growth rate that can increase the growth rate of SiC single crystals by forming a high temperature gradient on the crystal growth surface, thereby improving productivity and enabling the growth of more SiC single crystals per unit time.

[0010] In addition, another objective of the present invention is to provide a crystal growth apparatus with an enhanced crystal growth rate that enables the growth of a SiC single crystal with uniform and excellent quality in any part, including the edges of the grown SiC single crystal.

[0011] In addition, another objective of the present invention is to provide a crystal growth apparatus with an enhanced crystal growth rate that lowers the production cost of SiC single crystals and contributes to reducing substrate costs by improving the growth rate, thereby contributing to the commercialization and strengthening of competitiveness of SiC semiconductor products.

[0012] To achieve the aforementioned objective, the present invention provides a crystal growth apparatus comprising a crucible including a seed crystal support, an insulating material surrounding the crucible, and a heat source disposed around the insulating material, wherein an air pocket is formed in the upper part of the upper cover of the crucible in an upward direction, consisting of a first space (first region) - a second space (second region) - a third space (third region), wherein the second space is larger than the first space and the third space, thereby providing a crystal growth apparatus with an enhanced crystal growth rate.

[0013] It is preferable that the above air pocket be formed by the arrangement of insulating material.

[0014] The arrangement of the insulation material preferably includes: a first insulation material that partially contacts the upper cover of the crucible; a second insulation material that contacts the first insulation material on the upper part of the first insulation material and is configured to be shorter than the cross-sectional length of the first insulation material; and a third insulation material that partially contacts the second insulation material on the upper part of the second insulation material and is configured to be longer than the cross-sectional length of the second insulation material.

[0015] The above air pocket is formed by the arrangement of the first, second, and third insulating materials, and it is desirable to maintain a high temperature gradient during the crystal growth process by increasing the temperature difference on the crystal growth surface.

[0016] It is preferable that 1 to 2 of the above first and third insulation materials be stacked.

[0017] It is preferable that 1 to 4 of the above second insulation materials be stacked.

[0018] It is preferable that the width of the first, second, and third insulation materials is in the range of 15 to 20 mm.

[0019] It is preferable that the thickness of the first, second, and third insulation materials is in the range of 28 to 32 mm.

[0020] The first insulation material, the second insulation material, and the third insulation material are ring-shaped, and it is preferable that the inner diameter of the first insulation material and the third insulation material is 46 to 60 mm, and the inner diameter of the second insulation material is 110 to 130 mm.

[0021] The above insulation material is preferably graphite felt.

[0022] It is preferable that the above-mentioned crystal be a silicon carbide single crystal.

[0023] It is preferable that the above silicon carbide single crystal be grown using CVD-SiC as a raw material.

[0024] It is preferable that the temperature gradient (ΔT value) formed between the surface of the raw material direction of the above seed tablet and the surface of the crucible top direction is 4.0 to 7.0℃ / mm.

[0025] According to the present invention as described above, the growth rate of SiC single crystals can be increased by forming a high temperature gradient on the crystal growth surface, and thereby, an effect is expected in which productivity is improved, enabling the growth of more SiC single crystals per unit time.

[0026] In addition, the present invention is expected to have the effect of enabling the growth of a SiC single crystal with uniform and excellent quality in any part, including the edges of the grown SiC single crystal.

[0027] Furthermore, the present invention can lower the production cost of SiC single crystals by improving the crystal growth rate and contribute to reducing substrate costs; thus, it is expected to have an effect that contributes to the commercialization and strengthening of competitiveness of SiC semiconductor products.

[0028] Figure 1 is a graph showing a comparison of the physical properties of power semiconductors by material.

[0029] Figure 2 shows (a) a schematic diagram of the principle of the PVT method for crystal growth and a temperature gradient simulation, and (b) a temperature distribution diagram.

[0030] Figure 3 is a schematic diagram showing a conventional crystal growth apparatus.

[0031] Figure 4 is a diagram showing the crystals grown through the crystal growth apparatus of Figure 3.

[0032] Figure 5 is a diagram of the principle of a crystal growth apparatus applying the Mullins-Sererka instability theory.

[0033] FIG. 6 is a schematic diagram showing a crystal growth apparatus according to one embodiment of the present invention.

[0034] FIG. 7 is a diagram showing a comparison of (a) a temperature distribution diagram and (b) a temperature gradient curve graph of a crystal growth apparatus according to one embodiment of the present invention and a conventional crystal growth apparatus.

[0035] FIG. 8 is a photograph showing a crystal produced using a crystal growth apparatus according to one embodiment of the present invention.

[0036] FIG. 9 is a diagram showing (a) micro-Raman analysis results, (b) X-ray analysis results, and (c) impurity inspection results using SIMS of a crystal grown using a crystal growth apparatus according to one embodiment of the present invention.

[0037] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Furthermore, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description will be omitted.

[0038] In describing the present invention, the terms defined are defined with consideration of their functions in the present invention; however, since these may vary depending on the intent or convention of those skilled in the art, the definitions should be based on the content throughout this specification.

[0039] The present invention relates to a crystal growth apparatus, wherein the crystal referred to herein is preferably interpreted as a single crystal.

[0040]

[0041] FIG. 1 is a graph showing a comparison of the physical properties of power semiconductor materials, FIG. 2 is (a) a schematic diagram showing the principle of the PVT method for crystal growth and a temperature gradient simulation, and (b) a temperature distribution diagram, FIG. 3 is a schematic diagram showing a conventional crystal growth apparatus, FIG. 4 is a diagram summarizing the crystal grown through the crystal growth apparatus of FIG. 3, FIG. 5 is a diagram of the principle of a crystal growth apparatus applying the Mullins-Sererka instability theory, FIG. 6 is a schematic diagram showing a crystal growth apparatus according to an embodiment of the present invention, FIG. 7 is a diagram showing a comparison of (a) a temperature distribution diagram and (b) a temperature gradient curve graph of a crystal growth apparatus according to an embodiment of the present invention and a conventional crystal growth apparatus, respectively, FIG. 8 is a photograph showing a crystal manufactured using a crystal growth apparatus according to an embodiment of the present invention, and FIG. 9 is a diagram showing (a) micro-Raman analysis results, (b) X-ray analysis results, and (c) impurity inspection results using SIMS of a crystal grown using a crystal growth apparatus according to an embodiment of the present invention, respectively.

[0042]

[0043] In this invention, a CVD-SiC crushed block was used as a raw material instead of the conventional powdered SiC raw material. Since this block is not in powder form and has a very small specific surface area, it prevents carbon dust from being incorporated into the growing crystal even under strong flow conditions during rapid growth, thereby preventing the degradation of the single crystal quality.

[0044] In addition, the present invention presents a single crystal growth apparatus of Fig. 6 based on the Mullins-Sekerka instability theory of Fig. 5. A vertical temperature gradient induces the gas to move in a specific direction, thereby preventing heat accumulation on the growth plane and contributing to reducing irregularities and defects on the crystal surface that may occur due to heat accumulation according to the Mullins-Sekerka instability theory.

[0045] This design of the present invention creates a large temperature difference on the crystal growth surface to maintain a high temperature gradient during the single crystal growth process, and consequently, this high temperature gradient creates an environment in which the crystal can grow uniformly and enables the maintenance of good crystal quality even under high-speed growth conditions.

[0046] Figure 5(a) is a schematic diagram of a case where heat is discharged not only from the back surface of the crystal but also from the surroundings during crystal growth, so that the heat discharge through the crystal is ultimately small and the temperature gradient (ΔT value) in the vertical direction of the crystal is small. In this case, since heat is discharged through the crystal during crystal growth and heat is also accumulated on the crystal growth surface, it explains that radiative heat discharge from the crystal growth surface toward the raw material can be carried out to resolve this.

[0047] In contrast, Figure 5(b) is a schematic diagram showing a case where the crystal region is open only during crystal growth and the other regions are insulated, so there is a large amount of heat discharge to the back of the crystal and thus a large vertical temperature gradient (ΔT value). In this case, it explains that heat is not accumulated on the crystal growth surface during crystal growth, so radiative heat emission from the crystal growth surface to the raw material does not proceed.

[0048] Since radiative heat emission occurs on the surface of a solid and is actively generated on a rough surface with a large specific surface area, controlling radiative heat emission on the crystal growth surface can grow a single crystal of better quality, and when the air pocket proposed in the present invention is applied, the phenomenon of FIG. 5 (b) can be realized, thereby enabling high-speed growth of the crystal, and high-quality crystals can be grown despite such high-speed growth.

[0049] This is summarized in a mathematical formula as the following Mullins-Sekerka instability theory.

[0050] The Mullins-Sekerka instability theory can be explained by Equation 1 below. This is referred to as the heat flow equilibrium condition.

[0051] [Equation 1] q cry = q gas + q rad + q latent

[0052] q cry : efflux heat to the back side

[0053] q gas : influx heat from the gas phase

[0054] q rad : influx heat by radiation

[0055] q latent latent heat

[0056] Here, q represents heat flux and can be defined as the amount of heat transferred per unit area or the flow of thermal energy per unit time and area.

[0057] Here, the above q cry , q gas , q rad , q latent The breakdown is as follows.

[0058] Heat (q) transferred to the back of the crystal by penetrating it. cry ) : Heat transferred into the crystal, which is determined by the thermal conductivity of the crystal and the temperature gradient existing up and down within the crystal.

[0059] Heat from the gas phase (q gas ) : Heat transferred from a gas to a crystal surface, which is determined by the temperature difference between the gas and the crystal surface. The hotter the air or gas, the more heat is transferred to the crystal surface.

[0060] Heat (q) due to radiation rad) : Thermal radiation is a phenomenon in which an object emits or absorbs heat through electromagnetic waves (mainly infrared), and refers to the heat emitted into or absorbed from the surrounding environment by a crystal surface.

[0061] Latent heat generated by crystallization (q latent ) : This refers to the latent heat generated as the crystal grows, which is the heat released when crystallization proceeds.

[0062] q gas When >0, the surface of the crystal can be maintained stably. In other words, the flatness of the surface can only be maintained if heat absorption from the gas phase to the crystal surface occurs. If this condition is not met, radiant heat is emitted from the surface of the crystal, and crystals in the form of dendrites may be formed.

[0063] In addition, a high temperature gradient is required for the rapid growth of crystals. Through this, q gas The condition of >0 can be satisfied. Expressed as an equation, it is as shown in Equation 2 below.

[0064] [Equation 2]

[0065] Here, ΔT represents the temperature gradient within the crystal, v represents the crystal growth rate, ΔH represents the enthalpy change, and k represents the thermal conductivity of the crystal.

[0066] It can be seen from Equation 2 above that a high temperature gradient (ΔT) is required for stable high-speed crystal growth.

[0067] Equation 2 above indicates that the larger ΔT is, the higher the growth rate v can be maintained while ensuring surface stability. Since surface radiation of heat is significantly affected by the specific surface area of ​​the radiator (in this case, a crystal), surface radiation of heat increases as the specific surface area increases. Therefore, if heat is not sufficiently dissipated and accumulates on the surface of the radiator, a phenomenon occurs where the surface becomes rough in order to maximize surface radiation of heat. Consequently, the surface of the radiator is not stabilized. The present invention improves the structure of the device to stabilize the surface of such a radiator.

[0068] When ΔT is low, the emission of radiant heat from the crystal surface (q gas As <0) becomes dominant, dendrite structures are likely to form. Conversely, if ΔT is sufficiently high, the crystal surface absorbs heat from the gas phase, and q gas It can maintain a state of >0.

[0069]

[0070] The present invention has the following advantages.

[0071] In the present invention, the growth rate can be significantly increased by maintaining a high ΔT. Through simulation and experimental results, it was confirmed that high-speed growth of up to 2.56 mm / h is possible when ΔT is approximately 7.3℃ / mm or higher.

[0072] In addition, a high ΔT maintains surface flatness and suppresses dendrite formation. This is an important factor in producing high-quality single-crystal SiC bulk.

[0073] In addition, high-speed growth can shorten production time and, consequently, reduce the production cost of SiC wafers.

[0074] FIG. 6 is a crystal growth apparatus designed based on the Mullins-Sekerka instability theory of FIG. 5, which includes an air pocket structure. The air pocket structure was designed by applying the Mullins-Sekerka instability theory to increase the vertical temperature gradient, thereby enabling efficient heat management within the hot zone. This design increases the temperature difference on the crystal growth surface, thereby maintaining a high temperature gradient during the single crystal growth process. Consequently, this high temperature gradient creates an environment where the crystal can grow uniformly and maintain good crystal quality even under high-speed growth conditions.

[0075] Figure 7 illustrates the simulation results comparing a conventional model with a model using an air pocket structure according to an embodiment of the present invention. As shown, the model with an air pocket according to an embodiment of the present invention designed a hot zone that improved the temperature gradient of the gas phase on the crystal growth plane and the temperature gradient of the crystal growth surface by applying the Mullins-Sekerka instability theory through simulation. In addition, the temperature distribution inside the crucible obtained by FE analysis was compared with the conventional model.

[0076] In the case of a new design hot zone having an air pocket structure according to one embodiment of the present invention, the upper and lower temperatures of the crucible were 2175 to 2357°C, and the uppermost temperature of the raw material was 2340°C. In the case of a conventional crucible, the upper and lower temperatures of the hot zone were 2250 to 2350°C, and the uppermost temperature of the raw material was 2330°C.

[0077] The air pocket structure is a structure that can increase the amount of sublimation by enhancing heat transfer to the top of the raw material while minimizing heat loss to the outside of the crucible. In other words, by improving the heat flow inside the crucible, heat can easily reach the top of the raw material. This air pocket structure is implemented by an insulating material, and the insulating material located closest to the crucible can be named the first insulating material, the insulating material facing the first insulating material and stacked on top thereof can be named the second insulating material, and the insulating material facing the second insulating material and stacked on top thereof can be named the third insulating material.

[0078] If we assign roles to each area of ​​this air pocket structure, they are as follows.

[0079] The first region is the region immediately above the crucible, and is configured so that the upper part of the growing crystal is open while the other parts are insulated, thereby concentrating the flow of heat into the open part, that is, the upper part of the crystal.

[0080] The second zone is located just above the first zone and is a widely open area compared to the first zone. By minimizing the placement of insulation, the amount of heat accumulated is reduced, and the temperature of the space is maintained at a relatively low level. Since the temperature in the second zone is lower than that of the first zone and the crucible zone, it acts to create a large temperature gradient between the inside and outside of the crucible, which functions to facilitate the flow of heat.

[0081] The third zone is identical to the existing device structure and serves to insulate the device to prevent heat loss to the outside.

[0082] In the conventional device of Fig. 3, the temperature of the hot zone of the crucible is approximately 2250°C at the top and 2350°C at the bottom, and the temperature at the top of the raw material is approximately 2330°C. In contrast, in the device with an air pocket configured according to the present invention of Fig. 6, the temperature of the hot zone of the crucible is approximately 2175°C at the top and 2357°C at the bottom, showing a larger gap, and the temperature at the top of the raw material is maintained at approximately 2340°C, which is higher than the conventional temperature. This suggests that heat is transferred more effectively to the top of the raw material.

[0083] This resulted in a larger temperature gradient within the hot zone, and this temperature gradient facilitated heat flow, contributing to improved crystal growth efficiency and quality. Ultimately, the air pocket structure was designed to efficiently transfer heat within the crucible by optimizing heat distribution within the hot zone and concentrating heat flow to the outside of the crucible to achieve a high temperature gradient. Through this, it is expected that maintaining a high temperature at the top of the raw material will increase the amount of sublimation and contribute to improving crystal growth quality.

[0084] According to Fig. 7(b), compared to a conventional hot zone with a temperature gradient of ~4.3°C / mm between the vapor phase and the seed crystal surface, the hot zone equipped with the air pocket of the present invention showed a temperature gradient of ~7.3°C / mm, confirming that the temperature gradient is relatively large and the heat flow is excellent. This suggests that, according to the Mullins-Sekerka instability theory, the larger the temperature gradient value at the crystal surface, the smoother the heat release to the back surface becomes, thereby preventing the incorporation of polycrystalline materials and enabling the production of high-quality single crystals even under high-speed growth conditions, which can be confirmed in the graph. Therefore, by introducing the air pocket, a high temperature gradient of ~7.3°C / mm was achieved across the growth front, and the design including the air pocket also showed the effect of increasing the sublimation temperature of the raw material.

[0085]

[0086] In the present invention, a graphite felt, which is an insulating material that blocks heat from the heated graphite crucible, is placed close to the lid portion of the crucible where the temperature is relatively low. When the graphite felt is placed close in this way, it helps to maintain a high temperature gradient on the growth surface. This reduces heat accumulation in the crystal growth region and promotes stable single crystal growth.

[0087] The arrangement of the insulation material comprises: a first insulation material that partially contacts the upper cover of the crucible; a second insulation material that contacts the first insulation material on the upper part of the first insulation material and is configured to be shorter than the length of the first insulation material; and a third insulation material that partially contacts the second insulation material on the upper part of the second insulation material and is configured to be longer than the length of the second insulation material.

[0088] Below, an explanation regarding the air pocket structure and the size of the graphite felt was provided.

[0089] 1. Width and height range of insulation material (graphite felt)

[0090] The optimal range for radial thickness is approximately 15 to 20 mm. If it is less than 15 mm, the heat dissipation efficiency decreases due to the excessive size of the air pocket, and the temperature becomes uneven as ΔT becomes excessively high. Additionally, if it exceeds 20 mm, excessive heat accumulation occurs due to the reduction of the air pocket space, ΔT becomes excessively low, the growth rate slows down due to insufficient driving force, and the quality of the crystal deteriorates.

[0091] Next, regarding the graphite felt height, the optimal range is 28mm to 32mm. If it is less than 28mm, excessive heat accumulation occurs due to the reduction of air pocket space, resulting in an excessively low ΔT, slowed growth rate due to insufficient driving force, and deterioration of crystal quality. If it exceeds 32mm, heat dissipation efficiency decreases due to the excessive size of the air pockets, and the temperature becomes non-uniform as ΔT becomes excessively high.

[0092] Therefore, the width and height of the insulation material have critical significance within the above numerical range.

[0093]

[0094] 2. Number of Graphite Felt Layers and Design by Area

[0095] The first region is located directly above the crucible, and as an embodiment, the insulating material preferably consists of one to two layers. The role of the first region is to regulate initial heat release and provide a stable temperature distribution. Meanwhile, the upper part of the first region is the second region, which is a section with a larger space than the first region. As an embodiment, the insulating material of the second region preferably consists of one to four layers, and its role is to form △T and regulate heat flow. The third region is located above the second region and is a section with a narrower space compared to the second region. As an embodiment, the insulating material of the third region preferably consists of one to two layers. The role of the third region is to maintain a stable temperature and release heat after crystallization.

[0096] Here, if the first and third regions are absent, the air pocket structure is not established, and if the number of insulating materials exceeds two each, the initial heat release and heat release after crystallization do not proceed smoothly. Therefore, the number of insulating materials forming the first and third regions has critical significance within the above range.

[0097] In addition, if there is no second region, △T is less than 4.0℃ / mm, and (during high-speed growth) internal heat accumulation occurs due to excessive insulation. To dissipate the accumulated heat, the crystal planes become rough, degrading the crystal quality and increasing the FWHM value described later. Furthermore, if the insulation material in the second region exceeds four layers, the space in the second region becomes excessively large. Consequently, the temperature of the crystal growth surface located at the top of the crucible cools excessively, making it difficult to grow a single crystal stably as the crystal growth rate becomes too fast. Therefore, the insulation material in the second region is stacked in the range of 1 to 4 layers, and the insulation material in the second region has critical significance within this range.

[0098]

[0099] 3. Air pocket design

[0100] The insulation material is ring-shaped and is seated inside the device. The outer diameter of the insulation material is 180 mm, which is in accordance with the specifications of the device. The inner diameters of the first and third insulation materials are in the range of 40 to 60 mm, and the inner diameter of the second insulation material is in the range of 110 to 130 mm. If the inner diameters of the first and third insulation materials are less than 40 mm, excessive heat accumulation occurs on the surface of the crystal, affecting the quality of the crystal; if they exceed 60 mm, the purpose of the air pocket configuration is lost. Additionally, if the inner diameter of the second insulation material is less than 110 mm, excessive heat accumulation occurs on the surface of the crystal, affecting the quality of the crystal; if it exceeds 130 mm, the purpose of the air pocket configuration is lost. Therefore, the size range of the inner diameters of the first, second, and third insulation materials has critical significance within the above ranges.

[0101]

[0102] This single-crystal growth device design creates a large temperature difference at the crystal growth surface, which allows a high temperature gradient to be maintained. This high temperature gradient creates an environment for uniform crystal growth, minimizing the occurrence of irregularities or defects that may arise during the growth process.

[0103] In Fig. 8, the left photograph is an actual photograph of a SiC single crystal grown from a SiC single crystal sample. It shows the SiC single crystal attached to a graphite seed holder. The size, shape, and surface condition of the grown SiC crystal can be confirmed. The right photograph is an X-ray CT cross-sectional image of the grown SiC crystal.

[0104] In particular, the photograph on the right is a cross-sectional view of a crystal grown at a high growth rate of 2.56 mm / h, visualizing the uniformity of crystal growth. That is, the grown crystal did not exhibit microcracks, inclusions, or polycrystalline regions. Although the crystal has a convex shape in the center, it appeared flatter compared to the conventional crystal grown at the growth rate of 1.7 mm / h shown in Fig. 4. In other words, Fig. 4 indicates that a difference in growth rates between the center and the edges occurred due to the incomplete design of the temperature gradient in the crystal growth device. This suggests that the supply of raw materials occurred relatively uniformly depending on the location of the crystal, which is attributed to the smooth flow of heat without accumulation on the surface of the growing crystal. This implies that the air pocket structure was designed to maintain temperature uniformity at the bottom of the graphite and single crystal.

[0105] Figure 9(a) shows the results of micro-Raman analysis of the grown crystals. Raman spectroscopy was used to confirm the polytype of the grown crystals. As shown, when measuring five points on the top surface of the crystals, it was confirmed that single-phase 4H-SiC crystals were formed under all growth conditions, which is 204 cm⁻¹. -1 Transverse acoustic (TA) peak at 776 cm -1 and 796 cm -1 It was represented by the transverse optical (TO) peak at.

[0106] (b) is the result of X-ray analysis, which, as shown, indicates that the full width at half maximum (FWHM) value of each crystal is 19.6 arcsec in the air pocket hot zone structure. It can be seen that this value is somewhat wider than the existing full width at half maximum (FWHM) value of 18.9 arcsec shown in Fig. 4. The difference is 0.7 arcsec.

[0107] If the difference in FWHM values ​​is 0.7 arcsec, it appears to be a relatively small change. Generally, the FWHM of an XRD Rocking curve is smaller when the orientation of the lattice planes is consistent, and appears as a higher value in the case of crystals with high residual stress and significant warping. In the case of the Rocking curve in Fig. 4, the FWHM value is 18.9 arcsec; considering that the FWHM of high-quality 4H-SiC single crystals is approximately 10 to 20 arcsec, this value falls within the above range and is comparable to the FWHM values ​​of recent commercial SiC wafers (30 arcsec or less), demonstrating excellent crystallinity despite the high growth rate of 1.7 mm / h. Furthermore, in the case of the crystal grown in the device including the air pocket structure in Fig. 9, the FWHM value is 19.6 arcsec, showing good crystallinity despite the high growth rate of 2.56 mm / h, which is higher than the conventional 1.7 mm / h growth rate.

[0108] In other words, the present invention has the advantage of exhibiting excellent characteristics without degrading crystallinity, even though the growth rate has been increased.

[0109] In addition, (c) is a table showing the SIMS measurement results regarding the concentration of major impurities in the SiC crystal, and nitrogen (N), aluminum (Al), and boron (B) can be identified, and it was confirmed that they are in small amounts.

[0110] In the case of the crystal impurity concentration (Nitrogen, Boron, Aluminum) of a crystal grown using a device including an air pocket according to the present invention, nitrogen is 4.12 × 10⁻⁶. 19 atoms / cm 3 10, which is the usual range 16 ~10 18 atoms / cm 3 Compared to that, it is a level more than 2 to 3 times higher than the typical concentration. This is a doping designed to enhance n-type semiconductor characteristics. Boron is 2.58 × 10⁻⁶17 atoms / cm 3 10, which is the usual range 13 ~10 15 atoms / cm 3 This is a level more than 1,000 times higher compared to. In the case of this result, it is highly likely to be attributed to the characteristics of the raw material. Aluminum is 4.79 × 10⁻⁶ 14 atoms / cm 3 10, a typical amount 13 ~10 15 atoms / cm 3 It falls within the range. This appears to be due to the introduction of trace amounts of aluminum impurities during the growth process. However, this is a level observed in general SiC crystal growth processes and is not expected to be a major problem.

[0111]

[0112] Although the present invention has been described in more detail above with reference to examples, the present invention is not necessarily limited to these examples and can be modified in various ways within the scope of the technical concept of the present invention. Accordingly, the examples disclosed in the present invention are intended to explain, not limit, the technical concept of the present invention, and the scope of the technical concept of the present invention is not established by these examples. The scope of protection of the present invention should be interpreted by the claims below, and all technical concepts within an equivalent scope should be interpreted as being included within the scope of rights of the present invention.

Claims

1. A crystal growth apparatus comprising a crucible including a seed crystal support, an insulating material surrounding the crucible, and a heat source disposed around the insulating material, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that an air pocket is formed in the upper part of the upper cover of the above crucible in the upward direction, consisting of a first space (first area) - a second space (second area) - a third space (third area), wherein the second space is larger than the first space and the third space.

2. In Paragraph 1, A crystal growth device with an enhanced crystal growth rate, characterized in that the above air pocket is formed by the arrangement of insulating material.

3. In Paragraph 2, The arrangement of the above insulation material is, A first insulating material in partial contact with the upper cover of the crucible above; A second insulation material positioned above the first insulation material in contact with the first insulation material and configured to be shorter than the cross-sectional length of the first insulation material; and A third insulation material having a portion in contact with the second insulation material on the upper part of the second insulation material and configured to be longer than the cross-sectional length of the second insulation material; A crystal growth apparatus with an enhanced crystal growth rate, characterized by including 4. In Paragraph 3, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that the air pocket is formed by the arrangement of a first insulating material, a second insulating material, and a third insulating material, and a high temperature gradient is maintained during the crystal growth process by increasing the temperature difference of the crystal growth surface.

5. In Paragraph 3, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that the first and third insulating materials are stacked in 1 to 2 layers.

6. In Paragraph 3, A crystal growth device with an enhanced crystal growth rate, characterized in that 1 to 4 of the above-mentioned second insulating materials are stacked.

7. In Paragraph 3, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that the first, second, and third insulating materials have a width in the range of 15 to 20 mm.

8. In Paragraph 3, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that the first, second, and third insulating materials have a thickness in the range of 28 to 32 mm.

9. In Paragraph 3, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that the first, second, and third insulating materials are ring-shaped, the inner diameters of the first and third insulating materials are 46 to 60 mm, and the inner diameter of the second insulating material is 110 to 130 mm.

10. In Paragraph 1, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that the above-mentioned insulating material is graphite felt.

11. In Paragraph 1, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that the above-mentioned crystal is a silicon carbide single crystal.

12. In Paragraph 11, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that the above silicon carbide single crystal is grown using CVD-SiC as a raw material.

13. In Paragraph 1, A crystal growth apparatus with an enhanced crystal growth rate, characterized in that the temperature gradient (ΔT value) formed between the raw material direction surface of the above seed crystal and the crucible top direction surface is 4.0~7.0℃ / mm.

Images