WO2021129270A1 - Silicon carbide single crystal, substrate and device for preparation - Google Patents

Abstract

Disclosed is a crucible assembly for preparing a single crystal by using a PVT method, the crucible assembly comprising a crucible and a seed crystal column (6) arranged in the crucible, wherein a side wall of the crucible comprises an interlayer, the interlayer comprises an inner side wall (8) and an outer side wall (2), the porosity of the inner side wall (8) is higher than that of the outer side wall (2), the interlayer forms a raw material cavity (4), the extension direction of the seed crystal column (6) and that of the central axis of the crucible are approximately the same, and a crystal growth cavity is provided between the seed crystal column (6) and an inner surface of the inner side wall (8); and the crucible assembly and a crystal growth furnace can efficiently and rapidly prepare a silicon carbide single crystal that is large in size with an extremely low defect density, and a substrate of the silicon carbide single crystal, thereby laying the technical foundation for large-scale commercialization of the high-quality and low-cost silicon carbide substrate. The silicon carbide single crystal has a zero microtube with a spiral dislocation of less than 100 cm-2 and an edge dislocation density of less than 220 cm-2.

Description

Silicon carbide single crystal, substrate and preparation device Technical field

The application relates to a silicon carbide single crystal, a substrate and a preparation device, and belongs to the field of semiconductor material preparation.

Background technique

The existing silicon carbide preparation technology is mainly based on the physical vapor transmission (PVT) method. The PVT method is formed by sublimating and decomposing the silicon carbide raw material placed at the bottom and transferring it to the seed crystal along the axial temperature gradient for crystallization. The flake seed crystal used in the PVT method in the prior art is placed on the top of the crucible, and the silicon carbide single crystal grows vertically downward along a certain radial direction of the single crystal when it grows.

Since the silicon carbide single crystal grows downwards due to the limitation of the distance between the single crystal growth surface and the raw material surface, the crystal growth thickness is usually in the range of 20-50 mm, and the yield rate of the substrate made of the silicon carbide single crystal is low. In addition, since defects such as microtubules and dislocations in the silicon carbide seed crystals penetrate the silicon carbide single crystal and the seed crystals prepared therefrom along the <0001> direction. These defects will continue to be inherited into the newly grown single crystal during the single crystal growth process and continue to form through defects. Therefore, it is difficult to control the defect density in the single crystal and the substrate, and the cost is high, and it is difficult to improve the quality of the substrate.

Nature reported on the preparation of silicon carbide single crystals that avoid the inheritance of defects such as microtubules and dislocations through crystal cross-sectional growth. However, the preparation process of this method is cumbersome. Although it can reduce the defect density, the cost is high, and it is not suitable for industrial production processes. .

Summary of the invention

In order to solve the above problems, this application proposes a silicon carbide single crystal, a substrate and a preparation device for PVT method to prepare a silicon carbide single crystal. The preparation device includes a crucible assembly and a crystal growth furnace. The crucible assembly and crystal growth furnace can efficiently and quickly prepare large-size, low-defect density silicon carbide single crystals and their substrates, thereby laying a technical foundation for the large-scale commercialization of high-quality, low-cost silicon carbide substrates.

According to one aspect of the present application, there is provided a crucible assembly for preparing a single crystal by the PVT method. When the single crystal is prepared by the PVT method, the crucible assembly has a large thickness of the single crystal, so that the substrate is made of the single crystal. When used to prepare silicon carbide single crystals, it is not only highly efficient, but also has low defect density of the prepared silicon carbide single crystals, laying a technical foundation for the large-scale commercialization of silicon carbide single crystal substrates.

The crucible assembly for preparing single crystals by PVT method includes a crucible and a seed crystal column arranged in the crucible; the side wall of the crucible includes an interlayer, and the interlayer includes an inner side wall and an outer side wall. The porosity of the outer side wall is high, and the interlayer forms a raw material cavity; the extension direction of the central axis of the seed crystal column and the crucible is approximately the same, and a long length is formed between the seed crystal column and the inner surface of the inner side wall. Crystal cavity.

Optionally, the seed crystal column is made by cutting and polishing a single crystal column, and the surface of the seed crystal column is a smooth crystal surface.

Optionally, the interlayer is arranged corresponding to the height of the seed crystal column, and the seed crystal column shares a central axis with the crucible.

Optionally, the distance D1 between the inner side wall and the outer side wall is 50-300 mm, and the distance D2 between the inner surface of the inner side wall and the opposite surface of the seed crystal column is 100-300 mm.

Further, the lower limit of the D1 value range is selected from 70mm, 100mm, 120mm, 140mm, 160mm, 180mm, 200mm, 220mm, 240mm, 260mm or 280mm, and the upper limit is selected from 70mm, 100mm, 120mm, 140mm, 160mm, 180mm, 200mm , 220mm, 240mm, 260mm or 280mm. Furthermore, the D1 is 120mm-200mm, preferably the D1 is 140mm-180mm.

Further, the lower limit of the D2 value range is selected from 120mm, 140mm, 160mm, 180mm, 200mm, 220mm, 240mm, 260mm or 280mm, and the upper limit is selected from 120mm, 140mm, 150mm, 160mm, 170mm, 180mm, 200mm, 220mm, 240mm. , 260mm or 280mm. Furthermore, the D1 is 150mm-240mm, preferably the D1 is 170mm-220mm.

Optionally, the interlayer extends upward from the bottom of the crucible, and the seed column extends upward from the bottom of the crucible. Preferably, the interlayer extends from the bottom of the crucible to the top of the crucible, and the seed crystal column extends from the bottom of the crucible to the top of the crucible.

Optionally, the bottom and/or the top of the crucible are distributed with clamping grooves to install the seed crystal columns. Preferably, the card slot is an equilateral hexagon corresponding to the seed crystal column.

Optionally, the seed crystal is set as a hexagonal crystal system seed crystal, and the single crystal is a hexagonal crystal system single crystal. Optionally, the seed crystal column is configured as a hexagonal prism including six equivalent crystal planes

Optionally, the seed crystal column is configured as a hexagonal prism including six equivalent crystal planes.

Optionally, the width of the equivalent crystal plane is 5-20 mm. Preferably, the width of the equivalent crystal plane is 7-15 mm.

Preferably, the crystal face index of the long crystal face is the same, and the obtained single crystal has the same shape as the crystal form of the seed crystal column.

Preferably, the six equivalent crystal planes of the seed crystal column are respectively <1120><11-20><-1120><1-120><-1-120><1-1-20>; or The six equivalent crystal planes of the seed crystal column are <10-10><01-10><-1100><-1010><0-110><1-100>.

Optionally, the seed crystal column is a silicon carbide seed crystal column, and the single crystal is a silicon carbide single crystal. Preferably, the silicon carbide single crystal is an alpha silicon carbide single crystal, which has a hexagonal crystal system structure.

Optionally, the crucible is a graphite crucible. Preferably, the side wall of the crucible is a porous graphite plate, the porosity of the inner side wall is 40%-60%, and the pore size of the inner side wall is not higher than 1 um. The porosity of the outer side wall is not more than 10%, and the pore size of the outer side wall is not more than 1 um.

Optionally, the seed crystal column is arranged in one piece or spliced along the axial direction of the seed crystal column. The seed crystal columns can be directly stacked or bonded between the seed crystal columns. Due to the limitation of seed crystal preparation, multiple seed crystal columns can be spliced along the axial direction to increase the length of the seed crystal column, thereby increasing the thickness of the manufactured silicon carbide single crystal. The prepared single crystal is cut into a sheet-like single crystal substrate along its radial direction, and the single crystal defects grown at the splicing site can be removed; in order to improve the utilization rate of the single crystal, the removed defect single crystal can be used as a single crystal preparation raw material.

Optionally, the axial length of the seed crystal column is not less than 100 mm, and the axial length of the single crystal is not less than 100 mm. Preferably, the axial length of the seed crystal column is not less than 120 mm, and the axial length of the single crystal is not less than 120 mm. More preferably, the axial length of the seed crystal column is not less than 150 mm, and the axial length of the single crystal is not less than 150 mm.

According to one aspect of the present application, there is provided a crystal growth furnace comprising any of the above crucible components. The heating method of the crystal growth furnace is to make the side wall of the crucible heat, thereby heating the raw material in the interlayer to sublimate to the seed crystal column for crystal growth. , The thickness of the prepared single crystal is large, and the number of substrates prepared from the single crystal is large; when used in the preparation of silicon carbide single crystal, not only is high efficiency, but also the defect density of the prepared silicon carbide single crystal is small, which is The large-scale commercialization of silicon carbide single crystal substrates lays the technical foundation.

The crystal growth furnace includes a crucible assembly, a heating coil, a furnace body and a heat preservation structure. The crucible assembly includes a crucible and a seed crystal column arranged in the crucible. The crucible, the heat preservation structure, the furnace body and the heating coil are arranged from the inside to the outside. The side wall of the crucible includes an interlayer, the interlayer includes an inner side wall and an outer side wall, the inner side wall has a higher porosity than the outer side wall, and the interlayer forms a raw material cavity; the seed column and the crucible The extending direction of the central axis of the crucible is approximately the same, the crystal growth cavity is formed between the seed crystal column and the inner surface of the inner side wall; the heating coil inductively heats the side wall of the crucible, so that the raw material in the raw material cavity is sublimated After passing through the inner side wall, the gas phase is transported to the surface of the seed crystal column in the radial direction in the crystal growth cavity for crystal growth.

The crystal growth furnace includes any of the above crucible components, and further includes a heating coil and a heat preservation structure, the crucible is sheathed with a heat preservation structure, and the heating coil is arranged around the side wall of the heat preservation structure. The induction coil is an intermediate frequency induction coil.

Optionally, the crystal growth furnace includes a furnace body, and the furnace body is a quartz furnace. After the crucible assembly is provided with a heat preservation structure, it is placed in the furnace body, and an induction coil is arranged around the side wall of the furnace body.

According to one aspect of the present application, there is provided an application of any one of the above-mentioned crystal growth furnaces in the preparation of single crystals by the PVT method.

Preferably, the single crystal includes a silicon carbide single crystal. The crystal growth furnace can efficiently and quickly prepare silicon carbide single crystals and their substrates with extremely low defect density, thereby laying a technical foundation for the large-scale commercialization of high-quality, low-cost silicon carbide substrates.

According to one aspect of the present application, a method for preparing silicon carbide single crystals is provided. The preparation method can prepare silicon carbide single crystals of any volume, especially large volume and high thickness, high crystal growth efficiency, and cutting substrates. The number of pieces is large; the silicon carbide single crystal produced by this method has zero microtubes, screw dislocations below 100cm ^-2 and edge dislocation density below 220cm ^-2 , and the defect density can even reach zero; this method is high quality, The large-scale commercialization of low-cost silicon carbide substrates lays the technical foundation.

The preparation method of the silicon carbide single crystal includes the following steps:

1) Using the crucible assembly described in the above one, the crucible assembly includes a crucible and a seed crystal column;

2) Load the raw materials into the raw material cavity formed by the interlayer on the side wall of the crucible, install the seed crystal column in the crucible, and put it into the crystal growth furnace after assembly;

3) Increase the temperature of the crystal growth furnace so that the sublimation gas after the sublimation of the raw material passes through the inner side wall of the interlayer and is transported to the surface of the seed crystal column in the gas phase along the radial direction to grow the silicon carbide single crystal.

Optionally, the raw material is a silicon carbide raw material, or the raw material includes a silicon carbide raw material and a dopant. Optionally, the dopant includes a solid phase dopant contained in the raw material cavity and/or a gas phase dopant filled into the crucible.

Optionally, the solid phase dopant is selected from at least one of phosphorus element, germanium element, tin element, arsenic element, phosphorus compound, germanium compound, tin compound, and arsenic compound, and/or the gas phase doping The agent is nitrogen.

Preferably, the solid phase dopant contains low-resistance silicon single crystal powder.

Optionally, during the crystal growth process, the temperature difference between the inner surface of the inner side wall and the surface of the seed crystal is 50-300°C. Preferably, during the crystal growth process, the temperature difference between the inner surface of the inner side wall and the surface of the seed crystal is 100-200°C. The setting of the temperature is such that there is a sufficient temperature gradient between the inner surface and the seed crystal as a driving force to transfer the sublimated gas phase components laterally to the seed crystal in the center of the crucible.

Preferably, the crystal growth temperature is 2000-2300°C, and the crystal growth pressure is 5-50 mbar.

Preferably, inert gas and dopant gas are passed into the crucible. Preferably, the inert gas is nitrogen or helium, and the doping gas is nitrogen. The dopant gas is nitrogen to produce conductive N-type silicon carbide single crystals, and the amount of nitrogen is determined according to the resistivity of the silicon carbide single crystals obtained. Of course, the dopant gas can also be any gas that needs to be doped into the silicon carbide single crystal.

According to another aspect of the present application, a silicon carbide seed crystal column is provided, which includes the seed crystal column used in any of the above-mentioned preparation methods.

According to another aspect of the present application, there is provided a silicon carbide single crystal, which is prepared by any one of the above-mentioned methods, the axial length of the silicon carbide single crystal is not less than 100 mm, and the silicon carbide single crystal Zero microtubules, screw dislocation is less than 100cm ^-2 . Preferably, the screw dislocation of the silicon carbide single crystal is lower than 90 cm ^-2 ; more preferably, the screw dislocation of the silicon carbide single crystal is lower than 70 cm ^-2 .

Preferably, the resistivity of the silicon carbide single crystal is 10-20 mΩ. More preferably, the resistivity of the silicon carbide single crystal is 10-15 mΩ.

Preferably, the concentration of nitrogen in the silicon carbide single crystal is 10 ¹⁸ cm ^-3 -10 ²⁰ cm ^-3 and the concentration of phosphorus in the silicon carbide single crystal is 10 ¹⁷ cm ^-3 %-10 ¹⁹ cm ^-3 ; or

The concentration of nitrogen in the silicon carbide single crystal is 10 ¹⁹ cm ^-3 -10 ²⁰ cm ^-3 .

More preferably, the concentration of nitrogen in the silicon carbide single crystal is 10 ¹⁹ cm ^-3 -10 ²⁰ cm ^-3 and the concentration of phosphorus in the silicon carbide single crystal is 10 ¹⁸ cm ^-3 %-10 ¹⁹ cm ^-3 ; or

The nitrogen concentration in the silicon carbide single crystal is 10 ¹⁹ cm ^-3 -10 ²⁰ cm ^-3 .

Optionally, the edge dislocation of the silicon carbide single crystal is less than 220 cm ^-2 . Preferably, the screw dislocation of the silicon carbide single crystal is less than 180 cm ^-2 . More preferably, the screw dislocation of the silicon carbide single crystal is less than 130 cm ^-2 .

According to another aspect of the present application, there is provided a silicon carbide single crystal substrate, which is made by cutting and polishing any one of the above-mentioned silicon carbide single crystals. The silicon carbide single crystal substrate is Single crystal zero microtube, screw dislocation is less than 100cm ^-2 . Preferably, the screw dislocation of the silicon carbide single crystal substrate is lower than 90 cm ^-2 ; more preferably, the screw dislocation of the silicon carbide single crystal substrate is lower than 70 cm ^-2 .

Optionally, the edge dislocation of the silicon carbide single crystal substrate is less than 220 cm ^-2 . Preferably, the screw dislocation of the silicon carbide single crystal substrate is less than 180 cm ^-2 . More preferably, the screw dislocation of the silicon carbide single crystal substrate is less than 130 cm ^-2 .

The beneficial effects that this application can produce include, but are not limited to:

1. The crucible assembly provided by this application has a single crystal that can be produced in any size, especially a large thickness, which can be greater than 100mm, so that the number of substrates made from a single crystal is large, which is the size of a single crystal substrate. Large-scale commercialization lays the technical foundation.

2. When the crucible assembly provided by the present application is used to prepare silicon carbide single crystals, it not only has high efficiency, but also has low defect density of the prepared silicon carbide single crystals.

3. In the crystal growth furnace provided by this application, the heating method is that the side wall of the crucible generates heat, so that the raw material in the interlayer sublimates to the seed crystal column to grow the crystal. The single crystal produced can be of any size, especially if the thickness is large. It can be larger than 100mm, so that the production rate of substrates made of single crystals is high, which lays a technical foundation for the large-scale commercialization of silicon carbide single crystal substrates.

4. The crystal growth furnace provided by this application, when used to prepare silicon carbide single crystals, not only has high efficiency, but also the produced silicon carbide single crystals have low defect density, and produce zero microtubes and screw dislocations lower than 100cm ^-2 and the edge dislocation density less than 220cm ^-2-quality silicon carbide single crystal, the defect density can be close to zero.

5. The silicon carbide single crystal provided by this application can be of any size, especially any thickness, and the thickness can be greater than 100mm, with zero microtubules, screw dislocations less than 100cm ^-2 and edge dislocation density less than 220cm ^-2 , can be as low as zero.

6. The monocrystalline silicon carbide provided by the present application, the high quality of the substrate, low defect density, and the zero microtubules, less than 100cm ^-2 screw dislocation and the edge dislocation density less than 220cm ^-2, defect density can be as low zero.

7. The silicon carbide single crystal provided by this application achieves low resistance through co-doping with gas phase dopants and solid phase dopants; in addition to dopants, low resistance silicon single crystals doped with phosphorus can be selected. The material is mixed with conventional SiC powder to realize the co-doping of silicon and phosphorus. While increasing the doping, the reaction material is supplemented by the reaction of silicon and excess carbon to improve the crystal quality.

Description of the drawings

The drawings described here are used to provide a further understanding of the application and constitute a part of the application. The exemplary embodiments and descriptions of the application are used to explain the application, and do not constitute an improper limitation of the application. In the attached picture:

Fig. 1 is a schematic diagram of a crucible assembly involved in an embodiment of the application.

Detailed ways

In order to explain the overall concept of the application more clearly, a detailed description will be given below by way of example in conjunction with the accompanying drawings of the specification.

In order to be able to understand the above objectives, features and advantages of the application more clearly, the application will be further described in detail below with reference to the accompanying drawings and specific implementations. It should be noted that the embodiments of the application and the features in the embodiments can be combined with each other if there is no conflict.

In the following description, many specific details are set forth in order to fully understand this application. However, this application can also be implemented in other ways different from those described here. Therefore, the scope of protection of this application is not covered by the specific details disclosed below. Limitations of the embodiment.

In addition, in the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal" "," "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings , Is only for the convenience of describing the application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the application.

In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , Or integrated; it can be a mechanical connection, it can be an electrical connection, it can also be communication; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal communication of two components or the interaction relationship between two components . For those of ordinary skill in the art, the specific meanings of the above-mentioned terms in this application can be understood according to specific circumstances.

In this application, unless expressly stipulated and defined otherwise, the first feature “on” or “under” the second feature may be in direct contact with the first and second features, or the first and second features may be indirectly through an intermediary. contact. In the description of this specification, descriptions with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean specific features described in conjunction with the embodiment or example , The structure, materials, or characteristics are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above-mentioned terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

The crucible assembly of the present application is used in the physical vapor transmission method (PVT method) to prepare single crystals. The type of single crystal is not limited to silicon carbide single crystals. Any single crystal that can be prepared by the physical vapor transmission method can use the crucible assembly. When using the crucible assembly, the non-silicon carbide single crystal is different from the silicon carbide single crystal in that the shape of the seed crystal column 6 is the shape of the non-silicon carbide single crystal, such as when the non-silicon carbide single crystal is a cubic crystal system. , The seed crystal column 6 is cubic.

The following uses silicon carbide single crystal as an example to illustrate the structure and use of the crucible assembly and the crystal growth furnace.

1, the embodiment of the present application discloses a crucible assembly for preparing a single crystal by PVT method, which includes a crucible and a seed crystal column 6 arranged in the crucible; the side wall of the crucible includes an interlayer, and the interlayer includes an inner side wall 8 And the outer side wall 2, the inner side wall 8 has a higher porosity than the outer side wall 2, and the interlayer forms the raw material cavity 4; the axial direction of the seed crystal column 6 extends along the side wall of the crucible, between the inner surface of the seed crystal column 6 and the inner side wall 8 Form a growth cavity. The crucible assembly can produce single crystals with a large thickness when single crystals are prepared by the PVT method, so that the number of substrates prepared from single crystals is large; when used for preparing silicon carbide single crystals, the efficiency is high, and the obtained The defect density of the silicon carbide single crystal is low, which lays the technical foundation for the large-scale commercialization of silicon carbide single crystal substrates.

Optionally, part or all of the height area of the side wall is set as an interlayer. When a part of the height area of the side wall is set as an interlayer, the interlayer can be set at any height position of the side wall.

In order to improve the crystal growth efficiency and the uniform shape of the obtained single crystal, the interlayer and the seed crystal column 6 are arranged at corresponding heights. The seed crystal column 6 has a crucible common axis, so that the sidewalls of the seed crystal column 6 grow crystals at the same time.

In an embodiment not shown, the interlayer extends upward from the bottom of the crucible, that is, the inner side wall 8 and the outer side wall 2 extend upward from the bottom of the crucible and connect with the remaining part of the side wall of the crucible. Preferably, referring to FIG. 1, the interlayer extends from the bottom of the crucible to the top of the crucible, the seed column 6 extends from the bottom of the crucible to the top of the crucible, and the seed column 6 is arranged corresponding to the interlayer. The arrangement of the interlayer can efficiently produce large-volume single crystals, and the fixing method of the seed crystal column 6 is simple.

As an embodiment, the interlayer including the inner side wall 8 and the outer side wall 2 forms a raw material cavity 4, and the raw material cavity 4 is used to contain raw materials, such as silicon carbide powder used in the preparation of silicon carbide single crystals. Preferably, the distance D1 between the inner side wall 8 and the outer side wall 2 is 50-300mm, and the setting of D1 makes the side wall of the crucible heat up, which can ensure the efficient transfer of heat from the outer side wall 2 to the seed crystal column 6, and at the same time ensure the sublimation of the raw material The temperature and the temperature of the crystal growth surface of the seed crystal column 6 are within the required crystal growth temperature range, with low energy consumption and low cost.

As an embodiment, a crystal growth cavity is formed between the seed crystal column 6 and the inner surface of the inner side wall 8, and the distance D2 between the inner surface of the inner side wall 8 and the opposite surface of the seed crystal column 6 is 100-300 mm. The setting of D2 can ensure the quality, volume and efficiency of crystal growth. Preferably, the crucible has a substantially cylindrical structure, and the interlayer has a cylindrical ring structure. The combination of D1 and D2 can efficiently produce large-volume and high-quality single crystals.

In order to fix the seed crystal column 6 in the crucible, the position where the seed crystal column 6 needs to be fixed, such as the bottom and/or the top of the crucible, is distributed with clamping grooves, so that the seed crystal column 6 can be inserted into the clamping groove and fixedly installed. The shape of the clamping groove is different from that of the crucible. The shape of the cross section of the seed column 6 matches. As an embodiment, when the seed crystal column 6 is in the shape of a hexagonal prism, the locking groove is arranged in an equilateral hexagon corresponding to the seed crystal column 6. The clamping groove can be arranged in a convex or concave structure with respect to the inner surface of the bottom wall of the crucible.

The seed crystal can be any crystal type, and the material type and crystal type of the seed crystal and the single crystal are the same, and the shape of the seed crystal column 6 can be any columnar structure, such as a square prism, a cylinder, or a hexagonal prism. Preferably, the seed crystal is arranged as a hexagonal crystal seed crystal, and the single crystal is a hexagonal crystal system single crystal; more preferably, the seed crystal column 6 is arranged as a symmetrical hexagonal prism with six equivalent crystal faces, and the seed crystal column 6 is shaped like a hexagonal prism. The setting allows the uniform growth of the obtained single crystal to the periphery. Optionally, the width of the equivalent crystal plane is 5-20 mm. Preferably, the width of the equivalent crystal plane is 7-15 mm. The setting of the width of the equivalent crystal plane makes the setting of the width of the equivalent crystal plane so that the crystal can grow laterally and equally in a uniform thermal field with the crucible axis as the center of symmetry, so as to maintain the same axial position of the crystal, that is, subsequent The on-chip quality consistency and uniformity of the processed substrate. The equivalent crystal plane is used as the seed crystal growth plane to grow, which can avoid the traditional inheritance of dislocations and microtubules during growth along the <000-1>, thereby effectively reducing the dislocation density; at the same time, when the crystal is grown laterally The thickness is determined by the height of the seed crystal column, which greatly improves the crystal preparation efficiency.

In order to make the silicon carbide single crystal grow uniformly around the seed crystal column 6, when preparing the seed crystal column 6, the crystal face indices of the six equivalent planes of the seed crystal column 6 are respectively <1120><11-20><-1120 ><1-120><-1-120><1-1-20>; or the six equivalent crystal planes of the seed column 6 are <10-10><01-10><-1100><- 1010><0-110><1-100>, but not limited to the above six equivalent crystal planes, and other hexagonal symmetric crystal planes can be as long as they meet the crystal growth conditions.

As an embodiment, the seed crystal column 6 is a silicon carbide seed crystal column, and the single crystal is a silicon carbide single crystal. Preferably, the silicon carbide single crystal is an alpha silicon carbide single crystal, which has a hexagonal crystal system structure. Use a hexagonal crystal column as the seed crystal column 6 for crystal growth. The surface of the seed crystal column 6 is respectively <1120><11-20><-1120><1-120><-1-120><1-1-20> Six equivalent crystal planes. The silicon carbide single crystal block is polished to form a smooth crystal surface suitable for the vapor phase growth of the silicon carbide single crystal, and the six crystal faces replace the sheet wafer seed crystal in the conventional PVT method. The seed crystal column 6 can be processed from a silicon carbide crystal rod, the side length of the seed crystal column 6 is 5-20 mm, and the length is determined by the initial silicon carbide crystal rod.

As an embodiment, the crucible is a graphite crucible, the inner side wall 8 is a porous graphite plate, the porosity of the inner side wall 8 is 40%-60%, the pore size of the inner side wall 8 is not higher than 1um, and the porosity of the outer side wall 2 is not greater than 10%, the aperture of the outer side wall 2 is not higher than 1um. The porosity of the inner side wall 8 is greater than that of the outer side wall 2, so that the inner side wall 8 serves as a gas-phase transmission channel for the decomposition and sublimation of the raw material.

As an embodiment, the seed crystal column 6 is made by cutting and polishing a single crystal column. For example, the seed crystal column 6 is processed from a silicon carbide crystal rod. The side width of the seed crystal column 6 is 5-20 mm, and the length is changed from the initial Determined by silicon carbide ingot.

In order to set the seed crystal column 6 of any length, the seed crystal column 6 is integrated or spliced along the axial direction of the seed crystal column 6. The splicing method includes: the seed crystal pillars 6 can be directly stacked or the seed crystal pillars 6 can be bonded.

In order to obtain a high-length silicon carbide seed crystal column, a plurality of seed crystal columns 6 can be spliced along the axial direction to lengthen the length of the seed crystal column 6, thereby increasing the thickness of the silicon carbide single crystal obtained. For example, a plurality of identical silicon carbide seed crystal columns 6 can be spliced together up and down, and the spliced seed crystal columns 6 pass through the uppermost and lower end of the crystal column respectively to the hexagonal graphite hole in the center of the graphite cover in the crucible. The grooves are connected and fixed, and the height of the connected crystal column is the thickness of the silicon carbide crystal that can be grown.

When preparing a single crystal substrate, it can be cut along the radial direction of the single crystal to form a sheet-like single crystal substrate, and the defect single crystal grown at the splicing site can be removed; in order to improve the utilization rate of the single crystal, the removed defect single crystal can be used Used as a raw material for preparing single crystals.

The length of the seed crystal column 6 in the crucible assembly of this application determines the length of the produced single crystal, and the seed crystal column 6 of this application can be spliced in multiple stages, so the thickness of no less than 100mm, 120mm and 150mm can be obtained through one growth. The axial length of the crystal is no less than 100mm, 120mm and 150mm, and the length of the obtained single crystal is much longer than the length of 20-50mm of the single crystal obtained by the traditional disk seed crystal fixed on the top of the crucible. The length of the manufactured single crystal of the crucible assembly is large, so that the number of substrates manufactured from the single crystal is large.

Referring to Figure 1, a crystal growth furnace including any of the above crucible components also includes a heating coil, a furnace body and a heat preservation structure; after the crucible component is sheathed with the heat preservation structure, it is placed in the furnace body, and the side wall 2 of the furnace body is surrounded by induction Coil. Preferably, the furnace body is a quartz furnace, and the induction coil is an intermediate frequency induction coil. In the crystal growth furnace, the side wall of the crucible is heated by a heating coil, and the sublimation gas A after the sublimation of the raw material in the raw material cavity 4 passes through the inner side wall 8 and flows to each surface of the seed crystal column 6 for crystal growth; preferably, crystal growth The crystal plane indices of the faces are the same. The single crystal produced by the crystal growth furnace has a large thickness, and the number of substrates produced by the single crystal is large. When the crystal growth furnace is used to prepare silicon carbide single crystals, it not only has high preparation efficiency, but also has low defect density of the prepared silicon carbide single crystals, which lays a technical foundation for the large-scale commercialization of silicon carbide single crystal substrates.

As an embodiment, the crystal growth furnace includes a crucible, a heat preservation structure, a furnace body, a heating coil, and a seed crystal column 6 arranged from the inside to the outside; the side wall of the crucible includes an interlayer, and the interlayer includes an inner side wall 8 and an outer side wall 2. The wall 8 has a higher porosity than the outer side wall 2, and the interlayer forms a raw material cavity; the seed crystal column 6 is placed in the crucible, and the extension direction of the seed crystal column 6 and the center axis of the crucible is approximately the same. A crystal growth cavity is formed between the surfaces; the heating coil inductively heats the side wall of the crucible, so that the raw material in the raw material cavity passes through the inner side wall after sublimation, and the gas phase is transferred to the surface of the seed column in the crystal growth cavity along the radial direction for crystal growth . The crystal growth furnace can produce single crystals with a large thickness when single crystals are prepared by the PVT method, so that the number of substrates prepared from single crystals is large; when used for preparing silicon carbide single crystals, the efficiency is high, and the preparation The resulting silicon carbide single crystal has a low defect density, which lays a technical foundation for the large-scale commercialization of silicon carbide single crystal substrates.

When preparing the silicon carbide single crystal, the graphite outer side wall 2 is induction heated by an intermediate frequency coil and the heat is transferred to the silicon carbide powder raw material in the interlayer, and the heat is further directed to the porous graphite inner side wall 8 and the seed crystal column 6. Since the outer wall 2 of the crucible generates heat, there is a certain temperature gradient along the radial direction of the crucible. The growth rate of the silicon carbide single crystal is determined by the inner wall 8 and the seed crystal column 6 and the outer growth surface of the grown single crystal. The initial radial temperature The gradient, that is, the temperature difference between the inner wall 8 of the crucible and the surface of the seed crystal column 6 is controlled between 50-300°C. Due to the presence of the radial temperature gradient, the powder in the raw material cavity 4 is decomposed and sublimated and transferred along the radial temperature gradient to the crystal face of the seed crystal column 6 to recrystallize, and the surface of the single crystal will follow the radial temperature gradient to the inner side wall 8 is expanded to grow into a silicon carbide single crystal of the desired size.

The growth temperature of the silicon carbide single crystal is controlled at 2000-23000℃, the pressure is controlled at 5-50mbar, and an inert gas such as argon or helium is passed into the growth chamber as a protective gas; if the conductive N-type silicon carbide single crystal is prepared, it is inert A certain amount of nitrogen can be used as the doping gas in the gas, and the doping amount can be determined according to the actual required resistivity.

When the silicon carbide single crystal is prepared as a doped type, low resistance can be achieved by doping at least one of a gas phase dopant and a solid phase dopant. As an embodiment, the solid phase dopant phosphorus, phosphorus compound or a mixture of phosphorus and low-resistance silicon single crystal material and the gas phase dopant nitrogen are used for doping at the same time; the flow of nitrogen is adjusted to pass into the crucible Doping is carried out in the growth chamber after the growth chamber; the solid dopant is directly placed in the raw material chamber, preferably mixed with the raw material. Phosphorus-doped low-resistance silicon single crystal material is mixed with conventional SiC powder to realize the co-doping of silicon and phosphorus. While increasing the doping, the reaction material is supplemented by the reaction of silicon and excess carbon to increase the doped silicon carbide single crystal. quality.

Since defects such as microtubules and penetrating dislocations in the silicon carbide single crystal or silicon carbide seed column 6 are along the [0001] direction, lateral growth can avoid the inheritance of defects such as microtubules and dislocations, thereby obtaining extremely low defect density. Silicon carbide crystal ingots; preferably, zero microtubes, screw dislocations of less than 100cm ^-2 , and edge dislocation density of less than 220cm ^-2 silicon carbide single crystals and substrates can be obtained, preferably, silicon carbide single crystal substrates with screw positions The dislocation is less than 90 cm ^-2 ; more preferably, the screw dislocation of the silicon carbide single crystal substrate is less than 70 cm ^-2 . Preferably, the screw dislocation of the silicon carbide single crystal substrate is less than 180 cm ^-2 . More preferably, the screw dislocation of the silicon carbide single crystal substrate is less than 130 cm ^-2 . The defect density even approaches zero.

Example 1

As a method for preparing silicon carbide single crystal from any of the above crucibles and seed crystal columns, the method includes the following steps:

1) Provide crucible and silicon carbide seed crystal column;

2) Put the silicon carbide powder into the raw material cavity formed by the interlayer on the side wall of the crucible, install the silicon carbide seed crystal column in the crucible, and put it into the crystal growth furnace after assembly;

3) Increase the temperature of the crystal growth furnace to 2000-2300°C so that the sublimation gas after the sublimation of the raw material passes through the inner side wall of the interlayer and is transported to the surface of the seed crystal column in the radial gas phase. The temperature difference between the inner surface of the inner side wall and the surface of the seed crystal T is 50-300℃, and the silicon carbide single crystal is obtained by crystal growth;

Among them, D1 position is 50-300mm, D2 is 100-300mm, the seed crystal column is a hexagonal prism including six symmetrical equivalent planes, the width of the equivalent crystal plane D3 is 5-20mm, and the axial length of the seed crystal column is not low At 100mm.

Example 2

Take the preparation of the seed crystal column with a length of 150mm as an example to illustrate the preparation method. According to the method of Example 1, the preparation of silicon carbide single crystal 1#-7#, and the comparison of silicon carbide single crystal D1#-D5#, are different from the method of the embodiment. The point is in Table 1.

Table 1

sample	Temperature difference T/℃	D1/mm	D2/mm	D3/mm
Silicon carbide single crystal 1#	50	180	170	15
Silicon carbide single crystal 2#	150	180	170	15
Silicon carbide single crystal 3#	300	180	170	15
Silicon carbide single crystal 4#	150	160	170	15
Silicon carbide single crystal 5#	150	180	190	15
Silicon carbide single crystal 6#	150	180	170	7
Silicon carbide single crystal 7#	150	180	220	15
Compare with silicon carbide single crystal D1#	150	320	170	15
Compare with silicon carbide single crystal D2#	150	180	280	15
Compare with silicon carbide single crystal D3#	150	180	170	15
Compare with silicon carbide single crystal D4#	150	180	170	3
Compare with silicon carbide single crystal D5#	330	180	170	15

The 6-inch microtubes of the prepared silicon carbide single crystal 1#-7# and the comparison silicon carbide single crystal D1#-D5# are zero, screw dislocation (TSD) density, edge dislocation (TED) density and XRD characterization The crystal quality was tested, and the test results are shown in Table 2.

Table 2

It can be seen from the above that the laterally grown silicon carbide single crystal, when the radial temperature gradient, that is, the lateral driving force is larger, D1 is the loading amount is larger, D2 is the transmission distance is moderate, and the seed crystal equivalent crystal plane is relatively large. For a long time, it is easy to obtain high-quality silicon carbide single crystals with excellent crystalline quality and low dislocation density. This is due to the sufficient amount of material, large lateral growth driving force and appropriate transmission distance to help maintain the balance of C/Si ratio at the crystal growth interface, while the larger equivalent crystal plane size avoids polycrystalline planes The dislocations induced during the merger of the atomic step flow improve the quality of the silicon carbide single crystal.

Example 3

The difference between this embodiment and the preparation method in embodiment 2 is that the raw materials are silicon carbide powder, the dopant gas phase dopant nitrogen and the solid phase dopant phosphorus P. Doped silicon carbide single crystal 1#-7# and contrast silicon carbide single crystal D1#-D5# were doped to prepare doped silicon carbide single crystal 1#-7#, and contrast doped silicon carbide single crystal D1 #-D5#, see Table 3 for details.

table 3

sample	Temperature difference T/℃	D1/mm	D2/mm	D3/mm
Doped silicon carbide single crystal 1#	50	180	170	15
Doped silicon carbide single crystal 2#	150	180	170	15
Doped silicon carbide single crystal 3#	300	180	170	15
Doped silicon carbide single crystal 4#	150	160	170	15
Doped silicon carbide single crystal 5#	150	180	190	15
Doped silicon carbide single crystal 6#	150	180	170	7
Doped silicon carbide single crystal 7#	150	180	220	15
Contrast doped silicon carbide single crystal D1#	150	320	170	15
Contrast doped silicon carbide single crystal D2#	150	180	280	15
Contrast doped silicon carbide single crystal D3#	150	180	170	15
Contrast doped silicon carbide single crystal D4#	150	180	170	3
Contrast doped silicon carbide single crystal D5#	330	180	170	15

For the prepared doped silicon carbide single crystals 1#-7# and contrast doped silicon carbide single crystals D1#-D5#, the 6-inch microtubes are zero, screw dislocation (TSD) density, and edge dislocation (TED) Density and XRD characterize the crystal quality and resistivity for testing. The testing results are shown in Table 4.

Table 4

It can be seen from the above that the laterally grown silicon carbide crystal, when the radial temperature gradient, that is, the lateral driving force is large, D1, that is, the loading amount is large, D2, that is, the transmission distance is moderate, and the equivalent crystal surface of the seed crystal is long, It is easy to obtain high-quality silicon carbide single crystals with excellent crystalline quality and low dislocation density. This is due to the sufficient amount of material, large lateral growth driving force and appropriate transmission distance to help maintain the balance of C/Si ratio at the crystal growth interface, while the larger equivalent crystal plane size avoids polycrystalline planes Dislocations induced during the merger of the atomic step flow, thereby improving the crystal quality. The crystal resistivity is determined by the electroactive impurities introduced into the crystal and the intrinsic defects in the crystal. A higher flow doping atmosphere and more solid phase doping reactants will significantly reduce the crystal lattice position. Resistivity, increase its conductivity, until it reaches the solubility of electroactive impurities in the crystal.

Claims (15)

1. A crucible assembly for preparing single crystals by PVT method, characterized in that it comprises a crucible and a seed crystal column arranged in the crucible;

   The side wall of the crucible includes an interlayer, the interlayer includes an inner side wall and an outer side wall, the inner side wall has a higher porosity than the outer side wall, and the interlayer forms a raw material cavity;

   The extension direction of the central axis of the seed crystal column and the crucible is substantially the same, and a crystal growth cavity is formed between the seed crystal column and the inner surface of the inner side wall.
2. The crucible assembly according to claim 1, wherein the interlayer is arranged corresponding to the height of the seed crystal column, and the seed crystal column and the crucible have a common axis.
3. The crucible assembly according to claim 2, wherein the distance D1 between the inner side wall and the outer side wall is 50-300 mm;

   The distance D2 between the inner surface of the inner side wall and the opposite surface of the seed crystal column is 100-300 mm.
4. The crucible assembly according to claim 1, wherein the seed crystal column is a hexagonal crystal system seed crystal, and the single crystal is a hexagonal crystal system single crystal.
5. The crucible assembly according to claim 4, wherein the seed crystal column is configured as a hexagonal prism including six equivalent crystal planes.
6. The crucible assembly of claim 5, wherein the width of the equivalent crystal plane is 5-20 mm.
7. The crucible assembly according to claim 5, wherein the crucible is a graphite crucible, the seed crystal column is a silicon carbide seed crystal column, and the single crystal is a silicon carbide single crystal.
8. The crucible assembly according to claim 1, wherein the seed crystal column is arranged in one piece or formed by splicing along the axial direction of the seed crystal column.
9. The crucible assembly according to claim 1, wherein the axial length of the seed crystal column is not less than 100 mm, and the axial length of the single crystal is not less than 100 mm.
10. A crystal growth furnace, characterized in that it comprises a crucible component, a heating coil, a furnace body and a heat preservation structure, the crucible component comprises a crucible and a seed crystal column arranged in the crucible, the crucible, the heat preservation structure, the furnace body and The heating coil is set from the inside to the outside;

    The side wall of the crucible includes an interlayer, the interlayer includes an inner side wall and an outer side wall, the inner side wall has a higher porosity than the outer side wall, and the interlayer forms a raw material cavity;

    The extension direction of the central axis of the seed crystal column and the crucible is substantially the same, and a crystal growth cavity is formed between the seed crystal column and the inner surface of the inner side wall;

    The heating coil inductively heats the side wall of the crucible, so that the raw material in the raw material cavity passes through the inner side wall after sublimation, and the gas phase is transported to the surface of the seed crystal column in the radial direction in the crystal growth cavity for crystal growth .
11. The use of the crucible assembly of any one of claims 1-9 or the crystal growth furnace of claim 10 in the preparation of single crystals by the PVT method, the single crystals comprising silicon carbide single crystals.
12. A silicon carbide single crystal, characterized in that the axial length of the silicon carbide single crystal is not less than 100 mm, and the screw dislocation of the silicon carbide single crystal zero microtubes is less than 100 cm ^-2 .
13. The silicon carbide single crystal of claim 12, wherein the resistivity of the doped silicon carbide single crystal is 10-20 mΩ.
14. The silicon carbide single crystal of claim 12, wherein the concentration of nitrogen in the doped silicon carbide single crystal is 10 ¹⁸ cm ^-3 -10 ²⁰ cm ^-3 , and the doped silicon carbide single crystal The concentration of phosphorus in the phosphate is 10 ¹⁷ cm ^-3 %-10 ¹⁹ cm ^-3 ; or

    The mass percentage of nitrogen in the doped silicon carbide single crystal is 10 ¹⁹ cm ^-3 -10 ²⁰ cm ^-3 .
15. A silicon carbide single crystal substrate, characterized in that it is prepared by cutting and polishing the silicon carbide single crystal according to any one of claims 12-14, and the silicon carbide single crystal substrate is Single crystal zero microtube, screw dislocation is less than 100cm ^-2 .

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