Silicon carbide crystal growth device for improving spiral dislocation defect

Abstract

The utility model provides a silicon carbide crystal growth device for improving the spiral dislocation defect. The silicon carbide crystal growth device comprises a crucible body and a plurality of graphite partition plates arranged in the crucible, and the graphite partition plates are arranged at the bottom of a raw material area of the crucible at equal intervals; the graphite clapboards are inserted into the silicon carbide powder at intervals, the heights of the graphite clapboards are in an arithmetic progression, so that the heights of the silicon carbide powder are also in an arithmetic progression, and the heights of the graphite clapboards and the silicon carbide powder in the corresponding areas are gradually reduced in the direction from the small surface area of the seed crystal to the direction far away from the small surface area. In the single crystal growth process, the silicon carbide powder in the graphite partition interlayer is heated to sublimate, and the distance between the surface of the silicon carbide powder and the growth surface of the seed crystal is reduced due to the height advantage of the silicon carbide powder in the graphite partition area with higher height, so that the growth component forms the component density advantage at the surface of the seed crystal in the area; the conversion and movement processes of screw dislocation in the crystal are effectively promoted, and the crystal quality is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor preparation, and in particular to a silicon carbide crystal growth device for improving screw dislocation defects. BACKGROUND

[0002] Silicon carbide is an ideal material for preparing high-temperature, high-frequency, high-power and high-voltage devices due to its large band gap, high critical breakdown field strength, high carrier saturation mobility and high thermal conductivity, and is widely used in the field of power electronic devices. With the global low-carbon energy transformation, flexible AC / DC power transmission technology will be widely used in power transmission and distribution networks, which will bring explosive growth in demand for silicon carbide devices. This also puts forward higher requirements for high-quality and low-defect-density silicon carbide epitaxial materials.

[0003] Silicon carbide epitaxial material is mainly high-quality epitaxial material grown on a conductive silicon carbide single crystal substrate. The core technology of silicon carbide epitaxial material growth is defect control technology, especially for defects that can cause device failure or reliability degradation. The mechanism of substrate defect extension into the epitaxial layer, the defect transfer and conversion law at the interface of the substrate and the epitaxial layer, and the defect nucleation mechanism need to be considered during epitaxial growth. The defects of silicon carbide epitaxial layer are mainly divided into two categories: crystal defects and surface morphology defects. Crystal defects, including point defects, screw dislocations, microtubule defects, and edge dislocations, are mostly derived from the diffusion of defects in the silicon carbide substrate to the epitaxial layer, so the defects in the silicon carbide substrate need to be controlled, i.e. the silicon carbide crystal needs to be regulated.

[0004] The mainstream method for preparing silicon carbide crystals is physical vapor deposition (PVT method), which heats silicon carbide powder in a crucible to realize solid-gas phase change to generate growth components such as Si, C, Si2C and SiC2, which then move to the surface of the seed crystal under the driving of the temperature gradient in the growth chamber, recrystallize to obtain silicon carbide crystals, and thus form silicon carbide crystals. However, during the growth of silicon carbide single crystals by PVT method, factors such as inheritance of seed crystal screw dislocation, inclusions appearing during growth, and thermal stress of temperature field cause the proliferation of screw dislocations in silicon carbide crystals. The extended screw dislocations, i.e. from the substrate to the epitaxial layer, may also be converted into other defects and propagate along the growth axis, affecting the performance and reliability of silicon carbide power devices. CONTENT OF THE UTILITY MODEL

[0005] The present application provides a silicon carbide crystal growth device for improving screw dislocation defects to solve the problem that, in the preparation process of silicon carbide crystals, factors such as inheritance of seed crystal screw dislocation, inclusions appearing during growth, and thermal stress of temperature field cause the proliferation of screw dislocations in silicon carbide crystals, affecting the performance and reliability of silicon carbide power devices.

[0006] The application provides a silicon carbide crystal growth device for improving screw dislocation defects, comprising:

[0007] A crucible body;

[0008] A plurality of graphite partitions arranged in the crucible body, and the plurality of graphite partitions are arranged at equal intervals at the bottom of the crucible body;

[0009] The height of the graphite partition gradually decreases in the direction from the small face region to the region far from the small face region along the seed crystal [000-1] crystal face;

[0010] In the space formed by the graphite partitions in the crucible body, the space is filled with silicon carbide powder, so that the height of the silicon carbide powder gradually decreases in the direction from the small face region to the region far from the small face region along the seed crystal [000-1] crystal face.

[0011] In some possible implementation manners, the height of the graphite partition is arranged in an arithmetic sequence.

[0012] In some possible implementation manners, the seed crystal small face region is located at the right edge of the seed crystal C-polar surface on the projection line of the [000-1] axis on the seed crystal face.

[0013] In some possible implementation manners, the seed crystal surface normal direction and the

[0001] crystal face normal direction form an included angle, and the included angle is 2-6°.

[0014] In some possible implementation manners, the height tolerance of the graphite partition is 5-15 mm.

[0015] In some possible implementation manners, the width distance of the graphite partition and the inner wall of the crucible body is 35-120 mm.

[0016] In some possible implementation manners, the distance between every two graphite partitions is 35-120 mm.

[0017] In some possible implementation manners, the number of the graphite partitions is greater than or equal to 1.

[0018] In some possible implementation manners, the thickness of the graphite partition is 2-4 mm.

[0019] In some possible implementation manners, the inner diameter of the crucible body is 100-500 mm.

[0020] In some possible implementation manners, the inner wall thickness of the crucible body is 15-35 mm.

[0021] In some possible implementation manners, the top of the crucible body is further provided with a seed crystal placement area, and the seed crystal placement area is used for placing a seed crystal.

[0022] In some possible implementation manners, the crucible body further comprises fixing clamping grooves, and the graphite partitions are fixed to the inner wall of the crucible body through the fixing clamping grooves, and the number of the fixing clamping grooves is greater than or equal to 2.

[0023] From the above, the application provides a silicon carbide crystal growth device for improving screw dislocation defects, which comprises a crucible body and a plurality of graphite partitions arranged in the crucible, and the plurality of graphite partitions are arranged at equal intervals at the bottom of a crucible raw material area; the graphite partitions are inserted into silicon carbide powder at intervals, the height of the graphite partitions forms an arithmetic sequence, so that the height of the silicon carbide powder also forms an arithmetic sequence, and the height of the graphite partitions and the corresponding area of the silicon carbide powder decreases in the direction from the seed crystal facet area to the area far from the facet. In the single crystal growth process, the silicon carbide powder in the graphite partition interlayer is heated to sublimate, and the gas phase growth components are transported to the seed crystal growth surface, wherein the silicon carbide powder in the area with higher graphite partitions has a height advantage, which causes the surface of the silicon carbide powder to be closer to the seed crystal growth surface, so that the growth components in this area will preferentially reach the seed crystal surface and form a component density advantage on the seed crystal surface in this area, thereby maintaining the nucleation advantage of this area and helping to form a stable large step flow growth mode, effectively promoting the conversion and movement process of screw dislocations in the crystal, reducing the density of screw dislocations in the crystal, and improving the crystal quality. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the application, the following will briefly introduce the drawings needed in the embodiments. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0025] Fig. 1 A schematic diagram of a silicon carbide crystal growth device for improving screw dislocation defects provided for some embodiments of the application;

[0026] Fig. 2 A top view of a silicon carbide crystal growth device for improving screw dislocation defects provided for some embodiments of the application.

[0027] Illustration: 1-crucible body; 2-graphite partition; 3-seed crystal placement area. DETAILED DESCRIPTION

[0028] Embodiments will be described in detail below with reference to examples illustrated in the accompanying drawings. When the following description refers to the drawings, same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following embodiments are not meant to represent all implementations consistent with the present disclosure. Rather, they are merely examples of systems and methods consistent with some aspects of the present disclosure as detailed in the claims.

[0029] Silicon carbide is an ideal material for high-temperature, high-frequency, high-power, and high-voltage devices due to its large band gap, high critical breakdown field strength, high carrier saturation mobility, and high thermal conductivity. It is widely used in the field of power electronic devices. With the global energy low-carbon transformation, flexible AC / DC power transmission technology will be widely used in power transmission and distribution networks, which will lead to explosive growth in demand for silicon carbide devices. This also puts forward higher requirements for high-quality, low-defect-density silicon carbide epitaxial materials.

[0030] Silicon carbide epitaxial material is mainly the growth of high-quality epitaxial material on the basis of conductive silicon carbide single crystal substrate. The core technology of silicon carbide epitaxial material growth is defect control technology, especially for defects that can cause device failure or reliability degradation. The mechanism of substrate defect extension into the epitaxial layer, the defect transfer and transformation law at the interface of the substrate and the epitaxial layer, and the defect nucleation mechanism need to be considered during epitaxial growth. The defects of silicon carbide epitaxial layer are mainly divided into two categories: crystal defects and surface morphology defects. Crystal defects, including point defects, screw dislocations, microtubule defects, and edge dislocations, are mostly derived from the diffusion of defects in silicon carbide substrate to the epitaxial layer, so the defects in silicon carbide substrate need to be controlled, i.e. the silicon carbide crystal needs to be regulated.

[0031] The mainstream method for preparing silicon carbide crystals is a physical vapor deposition method (PVT method). By heating silicon carbide powder in a crucible, solid-gas phase change is achieved to generate Si, C, Si2C, SiC2 and other growth components, which then move to the surface of a seed crystal under the driving of a temperature gradient in a growth chamber, recrystallize to obtain silicon carbide crystals, thereby forming silicon carbide crystals. In the actual growth of SiC crystals by the PVT method, there are various crystal growth modes, including mainly spiral growth mode, two-dimensional layer growth mode, three-dimensional island growth mode and step flow growth mode. The spiral growth mode is most likely to occur in the initial growth stage and is caused by a screw dislocation in the growth interface under the condition of a low supersaturation of the growth components. The spiral growth mode has the advantage of continuity of the spiral steps. When there is a single growth center, spiral growth is conducive to forming smooth steps to provide stable and continuous growth sites and helps to reduce crystal defects. However, in the actual growth process, there are usually multiple growth centers in the crystal growth interface, which causes the discontinuity of the spiral growth steps and reduces the crystal quality. The two-dimensional layer growth mode mostly occurs in the growth stage with a low and stable supersaturation. The growth components on the crystal surface grow in a layer-by-layer deposition manner. The two-dimensional layer growth mode has the advantage of forming a single crystal with high quality and low defect density. However, in the actual growth process, extremely precise and stable growth condition control technology is required to achieve the two-dimensional layer growth mode. The three-dimensional island growth mode mainly occurs in the initial growth stage under the condition of a high supersaturation. Nucleation occurs at different positions to form multiple isolated three-dimensional island structures. The island structures gradually merge as the growth proceeds. The three-dimensional island growth mode has the advantage of fast growth speed. However, the island structures have a high probability of forming grain boundaries and defects during the merging process. The step flow growth mode mainly occurs in the middle and late growth stages. The step flow growth mode has the advantage of forming a smooth crystalline surface, reducing surface defects and growing high-quality crystals. However, it is difficult to maintain a stable growth step morphology.

[0032] However, in the process of growing silicon carbide single crystals by the PVT method, the coexistence of multiple growth modes causes the proliferation of spiral dislocations in the silicon carbide crystals due to the inheritance of seed spiral dislocations, the appearance of inclusions during the growth process, thermal stress of the temperature field and other factors. The extended spiral dislocations, i.e., the ones extending from the substrate to the epitaxial layer, can also be transformed into other defects and propagate along the growth axis, affecting the performance and reliability of silicon carbide power devices.

[0033] For example, Figs. 1-2As shown, the present application provides a silicon carbide crystal growth device for improving screw dislocation defects, comprising: a crucible body 1 provided with a raw material area for loading silicon carbide powder; the silicon carbide crystal growth device further comprises a plurality of graphite partitions 2 arranged in the crucible body 1, and the plurality of graphite partitions 2 are arranged at equal intervals at the bottom of the crucible body 1; the height of the graphite partition 2 gradually decreases in the direction from the small face area to the area away from the small face area along the seed crystal [000-1] crystal surface, and the height of the graphite partition 2 can be arranged in an arithmetic sequence, and of course can be other ways, such as a geometric sequence; the space formed by the graphite partitions 2 in the crucible body 1 is filled with silicon carbide powder, so that the height of the silicon carbide powder gradually decreases in the direction from the small face area to the area away from the small face area along the seed crystal [000-1] crystal surface, and the height of the silicon carbide powder can be filled in a way that is flush with the height of the graphite partition 2 on one side, and of course can be lower than the height.

[0034] The graphite partition 2 is inserted into the silicon carbide powder in the raw material area, the height of the graphite partition 2 is in an arithmetic sequence, and the height of the graphite partition 2 decreases in the direction from the small face area to the area away from the small face area along the seed crystal. The silicon carbide crystal growth device further comprises a seed crystal placement area 3 for placing a seed crystal, and the seed crystal placement area 3 is arranged inside the crucible body 1.

[0035] The silicon carbide crystal growth device provided by the present application sets up graphite partitions 2 with different heights in the raw material area to form partitions, fills silicon carbide powder into each graphite partition 2 in turn, uses the partition structure with heights arranged in an arithmetic sequence to construct the highest material height located in the small face area on the right side of the seed crystal, and the plurality of graphite partitions 2 are arranged in an arithmetic sequence to form a raw material partition with a height tolerance of h. By setting different arithmetic arrangement of silicon carbide powder partition structures, the small face area is maintained as a nucleation center during the growth of silicon carbide crystals, the step flow growth mode is used as the main growth mode, the stable high growth step morphology is ensured, the conversion and movement probability of screw dislocations in the initial growth of the crystal is improved, the screw dislocation density in the crystal is effectively reduced, and the crystal quality is improved.

[0036] In some embodiments, the position of the small face formed by the seed crystal is on the projection line of the [000-1] axis on the seed crystal surface, is located on the right side of the seed crystal C-polar surface close to the edge position, the seed crystal surface normal direction has an angle with the

[0001] crystal surface normal direction, and the angle is 2-6°.

[0037] The off-orientation seed crystal used in the present application refers to the seed crystal surface normal direction and the

[0001] crystal surface normal direction have a certain size angle, such as 4° off-orientation seed crystal, 2° off-orientation seed crystal. The off-orientation seed crystal is used for single crystal growth, the [000-1] of the seed crystal deviates from the central axis of the thermal field, the formation of the single crystal facet occurs at the edge of the crystal, that is, on the projection line of the [000-1] axis on the seed crystal surface, located at the right side of the seed crystal C polarity surface near the edge position. The step flow gradually expands from the facet on one side of the crystal to the other side of the crystal, realizing the growth of the single crystal.

[0038] In some embodiments, the number of graphite partitions 2 is greater than or equal to 1, and the thickness of the graphite partitions 2 is 2-4 mm. Among them, the number of graphite partitions 2 needs to be set according to the actual crucible structure.

[0039] The graphite partitions 2 are arranged in the crucible body 1 along the height direction of the crucible body 1, and the plurality of graphite partitions 2 are arranged in the silicon carbide powder in a spaced manner to separate the silicon carbide powder, divide the raw material area into multiple small areas, so that the silicon carbide powder and the silicon carbide powder, and the outer wall between the silicon carbide powder and the graphite partition 2 form a conveying channel for the flow of silicon carbide gas phase.

[0040] In some embodiments, the height tolerance h of the graphite partition 2 is 5-15 mm, and the width distance of the interlayer formed by the graphite partition 2 and the inner wall of the crucible body 1 is 35-120 mm, or the spacing between every two graphite partitions 2 is 35-120 mm.

[0041] When the number of graphite partitions 2 is 1, the width distance of the interlayer formed by the graphite partition 2 and the inner wall of the crucible body 1 is 35-120 mm. When the number of graphite partitions 2 is greater than 1, the spacing g of each graphite partition 2 is a fixed value, which is set in the range of 35-120 mm, the height of the graphite partition 2 is arranged in an arithmetic progression with a tolerance h, and h is set in the range of 5-15 mm according to the actual crucible structure. The graphite partition 2 is distributed in a decreasing manner in the direction from the seed facet area to the area away from the facet.

[0042] By arranging the graphite partitions 2 in the raw material area of the crucible body 1 in an equidifference manner with a height according to the tolerance h, the raw material area is divided into multiple raw material areas. After heating the raw material areas, the silicon carbide powder in the raw material area corresponding to each graphite partition 2 sublimates, and the gas phase growth component formed after the silicon carbide powder in the graphite partition 2 with the highest height sublimates will be transported to the seed crystal growth surface under the action of the axial temperature gradient and the component concentration gradient. Since the height advantage leads to that the surface of the silicon carbide powder in the area with a higher graphite partition 2 is closer to the seed crystal growth surface, the growth component in this area will preferentially reach the seed crystal surface and form a component concentration advantage. Therefore, when the silicon carbide crystal growth device in the present application is used for crystal growth, a distribution rule that the growth component concentration decreases in turn from the seed crystal facet area to the opposite area direction will appear on the seed crystal growth surface in the initial stage of crystal growth, which corresponds to the height rule of the silicon carbide powder. Then, under the joint action of the supersaturation and the temperature, the growth component recrystallizes on the seed crystal growth surface. Similarly, at the same growth stage, since the component concentration of each area of the seed crystal surface is different, the recrystallization efficiency decreases in turn from the seed crystal facet area to the opposite area direction, which leads to that the crystal nucleation center will continuously remain in the seed crystal facet area corresponding to the area with the highest height of the silicon carbide powder in this growth structure, and since the growth component concentration is large, the probability of coalescence of the silicon carbide crystal growth steps in this area is greatly improved, thereby forming a stable large-step flow growth mode, thereby effectively promoting the conversion and movement process of the screw dislocations in the crystal, reducing the density of the screw dislocations in the crystal, and improving the crystal quality.

[0043] In some embodiments, the crucible body 1 further comprises a fixed clamping groove, and the graphite partition 2 is fixed to the inner wall of the crucible body 1 through the fixed clamping groove. The number of the fixed clamping grooves is greater than or equal to 1. In order to facilitate the perfect fit of the graphite partition 2 and the crucible body 1, the graphite partition 2 is fixed to the inner wall of the crucible body 1 through the fixed clamping groove. In some embodiments, the inner diameter of the crucible body is 100-500 mm, and the wall thickness of the crucible body is 15-35 mm.

[0044] The graphite partition 2 in the silicon carbide crystal growth device for improving screw dislocation defects in the present application is not integrally formed with the crucible body 1, but is connected in the crucible body 1 through clamping. Through this connection mode, the graphite partition 2 can be easily disassembled and cleaned.

[0045] The present application sets differentially arranged graphite partitions to form a silicon carbide powder partition structure with different heights, so that the step-flow growth mode starting from a facet region is maintained as the main mode during silicon carbide crystal growth. Under the action of a single growth center and a large step-flow growth mode, the evolution of screw dislocation defects in the crystal to SF (stacking fault) defects is greatly promoted, and with the advancement of the step flow on the radial growth surface of the seed crystal, the stacking fault defects in the crystal are pushed to the edge of the crystal and further pushed out of the growth surface of the crystal during the growth process. Therefore, by optimizing the raw material region during the growth of silicon carbide in the present application, the conversion and movement of screw dislocations to stacking faults during the growth of the crystal are improved, and the screw dislocation density in the crystal is effectively reduced, and the crystal quality is improved.

[0046] As can be seen from the above embodiments, the present application provides a silicon carbide crystal growth device for improving screw dislocation defects, which comprises a crucible body and a plurality of graphite partitions arranged in the crucible, and the plurality of graphite partitions are arranged at equal intervals at the bottom of the crucible raw material area; the graphite partitions are inserted in the silicon carbide powder at intervals, the height of the graphite partitions is an arithmetic sequence, so that the height of the silicon carbide powder also presents an arithmetic sequence, and the height of the graphite partitions and the corresponding region of the silicon carbide powder decreases in the direction from the seed facet region to the region away from the facet region. During single crystal growth, the silicon carbide powder in the graphite partition interlayer is heated to sublimate, and the gas phase growth components are transported to the seed growth surface. The silicon carbide powder in the region with higher graphite partitions has a height advantage, which causes the distance between the surface of the silicon carbide powder and the seed growth surface to be shorter, so that the growth components in this region will preferentially reach the seed surface and gather, forming a component density advantage on the seed surface in this region, which helps to form a stable large step-flow growth mode, effectively promotes the conversion and movement of screw dislocations in the crystal, reduces the density of screw dislocations in the crystal, and improves the quality of the crystal.

[0047] The similar parts among the embodiments provided by the present application can be referred to each other, and the specific embodiments provided above are only a few examples under the general concept of the present application, and do not limit the protection scope of the present application. For those skilled in the art, any other embodiments extended according to the present application scheme without creative labor are within the protection scope of the present application.

Claims

1. A silicon carbide crystal growth apparatus for improving spiral dislocation defects, characterized in that, The utility model relates to a graphite crucible for preparing silicon carbide single crystal, which comprises: a crucible body (1); a plurality of graphite partitions (2) arranged in the crucible body (1) and equidistantly arranged at the bottom of the crucible body (1); the height of the graphite partition (2) gradually decreases in the direction from the seed crystal [000-1] crystal face small area to the area far from the small area; the space formed by the graphite partitions (2) in the crucible body (1) is filled with silicon carbide powder, so that the height of the silicon carbide powder gradually decreases in the direction from the seed crystal [000-1] crystal face small area to the area far from the small area.

2. The silicon carbide crystal growth apparatus of claim 1, wherein, The height of the graphite partition (2) is arranged in an arithmetic sequence.

3. The silicon carbide crystal growth apparatus of claim 1, wherein, The seed crystal small area is in The [000-1] axis is located on the projection line of the [000-1] axis on the seed crystal face, and is located on the right side of the seed crystal C polarity face close to the edge; the seed crystal surface normal direction and the [0001] crystal face normal direction have an included angle, and the included angle is 0-6°.

4. The silicon carbide crystal growth apparatus of claim 1, wherein The height tolerance of the graphite partition (2) is 5-15 mm.

5. The silicon carbide crystal growth apparatus of claim 1, wherein The width distance of the graphite partition (2) and the inner wall of the crucible body (1) is 35-120 mm.

6. The silicon carbide crystal growth apparatus of claim 1, wherein, The number of the graphite partitions (2) is greater than or equal to 1.

7. The silicon carbide crystal growth apparatus of claim 6, wherein The thickness of the graphite partition (2) is 2-4 mm.

8. The silicon carbide crystal growth apparatus of claim 1, wherein, The inner diameter of the crucible body (1) is 100-500 mm.

9. The silicon carbide crystal growth apparatus of claim 8, wherein, The inner wall thickness of the crucible body (1) is 15-35 mm.

10. The silicon carbide crystal growth apparatus of claim 1, wherein, The crucible body (1) further comprises a fixing clamping groove, the graphite partition (2) is fixed with the inner wall of the crucible body (1) through the fixing clamping groove, and the number of the fixing clamping grooves is greater than or equal to 2.

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