PVT crystal growth crucible capable of realizing flow guiding

Abstract

The application discloses a PVT crystal growth crucible capable of realizing flow guiding, which comprises a growth crucible, an induction coil, a seed crystal holder and a flow guiding source device. The PVT crystal growth crucible can effectively realize precise control on a material transport path through cooperation of a physical blocking dam structure, rear cavity flow guiding and special direction placement of a seed crystal, so that the material is always transported along a specific direction of a growth interface step flow, the stability and repeatability of crystal growth are effectively improved, the crystal crystallization quality is improved, and the crystal dislocation density is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to a PVT crystal growth crucible capable of guiding flow. BACKGROUND

[0002] With the rapid development of technology, in the face of new generation of electronic devices higher temperature resistance, higher voltage, higher frequency and higher power requirements, as the most basic and widely used material in the semiconductor industry-silicon (Si) due to its own physical and chemical properties of the limitations, more and more difficult to meet these needs. The discovery and development of the third generation of wide band gap semiconductor materials represented by silicon carbide (SiC), gallium nitride (GaN) and other single crystals have brought new hope for the development of new generation of power electronic devices.

[0003] Compared with the traditional silicon single crystal, silicon carbide single crystal has wider band gap, higher saturation electron mobility, higher breakdown field strength, higher thermal conductivity, and more stable physical and chemical properties. In addition, after decades of development, silicon carbide crystal preparation technology is relatively mature, and it is the only single crystal that can form silicon dioxide insulator by thermal oxidation among existing compound semiconductor materials, so electronic devices prepared by silicon carbide single crystal have gradually replaced silicon-based devices in many fields, and have become one of the most important third-generation semiconductor materials recognized internationally.

[0004] In recent years, with the continuous improvement of silicon carbide single crystal preparation technology, the size and quality of the prepared silicon carbide single crystal have been continuously improved, and it has shown irreplaceable advantages in the fields of high-power, high-temperature, high-frequency power electronics, optoelectronics, and special semiconductor devices, and has been widely used. However, the production efficiency and preparation cost of semiconductor devices are the core elements that restrict their more extensive application. Therefore, how to obtain higher quality and larger size silicon carbide single crystal, and how to improve the yield of single crystal preparation and reduce the cost of silicon carbide single crystal are the common problems faced by the silicon carbide industry, and the common goal of everyone's struggle.

[0005] At present, PVT method is the most widely used and most mature method for preparing silicon carbide single crystal. In the process of preparing silicon carbide single crystal by PVT method, due to the existence of a large number of silicon carbide crystal homomorphs, it is easy to produce polymorphism during growth, which further leads to a significant decrease in available crystal area. In addition, the occurrence of micro-zone polymorphism often induces the generation of dislocation defects, and how to further reduce the dislocation defect density is also the research direction pursued by the silicon carbide industry in recent years.

[0006] The structure information of the silicon carbide crystal in the PVT growth process is derived from the side wall exposure area of the growth step flow, under certain temperature field conditions, the material volatilized from the raw material zone is driven to transport mass in a certain step flow specific direction, which is the necessary condition for maintaining the single 4H polytype of the silicon carbide growth process, and is also an effective means to inhibit the nucleation and formation of dislocation defects at the growth interface. Therefore, the flow guide of the volatilized material is a necessary and effective means for the growth of high crystalline quality silicon carbide crystal.

[0007] In the process of PVT growth of silicon carbide crystal, the chamber pressure is very low, usually only 1~20mbar, and the Rayleigh number condition is far below the threshold required for convection to occur. In other words, the mass transport in the PVT growth process of silicon carbide crystal is completely completed by thermal diffusion. Therefore, designing a reasonable physical barrier guide structure is the key to realizing the precise control of the mass transport process, and the uniform sublimation process in the traditional PVT growth process cannot realize the precise control of the material transport. The material transport process has certain randomness, which will also lead to the fact that the growth process of each furnace cannot perfectly repeat the ideal process conditions, and has a certain negative impact on the stability, quality and process repeatability of the grown crystal. SUMMARY

[0008] The purpose of the present application is to provide a PVT crystal growth crucible capable of realizing flow guide to solve the problems raised in the above background.

[0009] To achieve the above purpose, the present application provides the following technical scheme: a PVT crystal growth crucible capable of realizing flow guide, comprising a growth crucible, an induction coil, a seed crystal holder box flow guide source device, the growth crucible is wrapped with insulation felt, the two sides of the insulation felt are provided with an induction coil, the inside bottom of the growth crucible is filled with silicon carbide powder, a porous graphite filter plate is arranged on the upper part of the silicon carbide powder, a seed crystal holder box flow guide hole is arranged on the top cover plate of the growth crucible, a seed crystal holder is arranged below the cover plate, a seed crystal is adhered to the seed crystal holder, and the flow guide source device comprises a porous graphite filter plate and a flow guide graphite baffle.

[0010] Preferably, the porosity of the porous graphite filter plate is 40%~75%, the diameter is 130mm~250mm, and the thickness is 1mm~3mm, and the diameter is equal to the inner diameter of the corresponding used crucible material area.

[0011] Preferably, the flow guide graphite baffle has a porosity less than 35%, a diameter of 130mm-250mm, a thickness of 1mm-3mm, a distance of 2-20mm from the lower surface to the porous graphite filter plate, an opening on one side of the flow guide graphite baffle, an opening arc length of one fourth to one third of the circumference of the flow guide graphite baffle, a graphite baffle inside the opening perpendicular to the porous graphite filter plate, a thickness of 1mm-3mm, a height of 10-50mm, and a distance of 50-100mm from the plane of the graphite baffle to the seed crystal.

[0012] Preferably, the seed crystal holder rear cavity flow guide hole is located within one third of the circumference of the flow guide graphite baffle, the opening shape can be circular, square, rectangular or any shape, the number of openings is 1-20, and the total opening area is 10-500mm 2 .

[0013] Compared with the prior art, the present application has the following beneficial effects:

[0014] 1. The special material transport direction realizes effective inheritance of structure information in the growth process, and inhibits the occurrence of polytypic coexisting defects or micro-area polytypic coexisting defects.

[0015] 2. The accurate controllability of the reverse material transport prevents the inconsistency of furnace or batch in the body growth process.

[0016] 3. The boring and continuous and stable transport is not prone to process mutation, which is extremely beneficial to the growth of crystal thickness. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structural schematic diagram of the present application;

[0018] Figure 2 is a schematic diagram of the flow guide graphite baffle;

[0019] Figure 3 is a schematic diagram of the seed crystal plate rear cavity flow guide hole and the seed crystal direction during assembly;

[0020] Figure 4 is a silicon carbide crystal with a diameter of 158mm;

[0021] Figure 5 is a dislocation test result graph of a silicon carbide crystal with a diameter of 158mm;

[0022] Figure 6 is a silicon carbide crystal with a diameter of 164mm;

[0023] Figure 7 is a dislocation test result graph of a silicon carbide crystal with a diameter of 164mm.

[0024] In the figure: 1, induction coil; 2, insulation felt; 3, growth crucible; 4, silicon carbide powder; 5, porous graphite filter plate; 6, graphite flow guide baffle; 7, graphite baffle; 8, seed crystal holder; 9, seed crystal holder rear cavity flow guide hole; 10, seed crystal; 11 opening, 12 growth facet. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0026] Please refer to Figures 1-3 , the present application provides a technical solution: a PVT crystal growth crucible capable of realizing flow guiding, comprising a growth crucible 3, an induction coil 1, a seed crystal holder 8 and a flow guiding source device, the growth crucible 3 is wrapped with insulation felt 2, the two sides of the insulation felt 2 are provided with the induction coil 1, the bottom of the inside of the growth crucible 3 is provided with silicon carbide powder 4, the upper part of the silicon carbide powder 4 is provided with a porous graphite filter plate 5, the top cover plate of the growth crucible 3 is provided with a seed crystal holder rear cavity flow guide hole 9, the lower part of the cover plate is provided with the seed crystal holder 8, the seed crystal holder 8 is adhered with a seed crystal 10, and the flow guiding source device comprises the porous graphite filter plate 5 and a flow guiding graphite baffle 6.

[0027] The porosity of the porous graphite filter plate is 40% to 75%, the diameter is 130 mm to 250 mm, and the thickness is 1 mm to 3 mm, and the diameter is equal to the inner diameter of the corresponding used crucible material area;

[0028] The porosity of the flow guiding graphite baffle 6 is less than 35%, the diameter is 130 mm to 250 mm, the thickness is 1 mm to 3 mm, the distance from the lower surface of the flow guiding graphite baffle to the porous graphite filter plate is 2 to 20 mm, one side of the flow guiding graphite baffle is provided with an opening, the opening arc length is one fourth to one third of the circumference of the flow guiding graphite baffle, the inside of the opening is provided with a graphite baffle 7 perpendicular to the porous graphite filter plate, the thickness of the graphite baffle is 1 mm to 3 mm, the height is 10 to 50 mm, and the distance from the plane of the graphite baffle to the seed crystal is 50 to 100 mm;

[0029] The seed crystal holder rear cavity flow guide hole 9 is located within one third of the circumference of the flow guiding graphite baffle 6, the shape of the opening can be circular, square, rectangular or any shape, the number of openings is 1 to 20, and the total passage area of the openings is 10 to 500 mm 2 .

[0030] When the seed crystal is assembled, the <11-20> direction, usually the position of the growth facet 12, is directed to the position of the flow guide hole, as shown in detail Figure 3 ;

[0031] The 6-inch silicon carbide crystal prepared by the method has a thickness of 10-30 mm and a diameter of 150-170 mm.

[0032] The 6-inch silicon carbide crystal prepared by the method has a dislocation density index of EPD less than 1500, TSD less than 20, and BPD less than 100.

[0033] The 8-inch silicon carbide crystal prepared by the method has a thickness of 10-25 mm and a diameter of 200-220 mm.

[0034] Embodiment:

[0035] (1) The diameter of the crystal grown by the above method is 158 mm;

[0036] (2) The diameter of the porous graphite sheet is 182 mm. The diameter of the graphite flow guide baffle is 155 mm, the arc length of the opening of the flow guide baffle is 145 mm, the height of the graphite baffle is 30 mm, and the distance between the plane of the graphite baffle and the seed crystal is 70 mm.

[0037] (3) Three flow guide holes with a diameter of 5 mm are opened in the rear cavity of the seed crystal holder, and the center distance of the flow guide holes is 20 mm.

[0038] (4) A 155 mm diameter seed crystal is used, and the <11-20> direction of the seed crystal points to the position of the flow guide hole in the rear cavity of the seed crystal holder during assembly.

[0039] (5) When the seed crystal holder is assembled with the crucible, the position of the flow guide hole in the rear cavity is located at the position of the graphite flow guide baffle.

[0040] (6) The grown crystal is shown in Figure 4 , the diameter of the crystal is 158 mm, and the effective thickness of the crystal is 22 mm. The dislocation data of the wafer cut from the crystal ingot is shown in Figure 5 , and the dislocation density value is significantly lower than the average level in the industry.

[0041] Embodiment:

[0042] (1) The diameter of the crystal grown by the above method is 158 mm;

[0043] (2) The diameter of the porous graphite sheet is 182 mm. The diameter of the graphite flow guide baffle is 155 mm, the arc length of the opening of the flow guide baffle is 150 mm, the height of the graphite baffle is 30 mm, and the distance between the plane of the graphite baffle and the seed crystal is 75 mm.

[0044] (3) Three flow guide holes with a diameter of 5 mm are opened in the rear cavity of the seed crystal holder, and the center distance of the flow guide holes is 22 mm.

[0045] (4) The seed crystal with a diameter of 160 mm is used, and the <11-20> direction of the seed crystal points to the position of the guiding hole in the rear cavity of the seed crystal holder.

[0046] (5) When the seed crystal holder is combined with the crucible, the position of the guiding hole in the rear cavity is located at the position of the graphite guiding plate.

[0047] (6) The crystal obtained by growth has a diameter of 164 mm and an effective thickness of 18 mm, as shown in Figure 6 The dislocation data of the wafer cut from the crystal ingot are shown in Figure 7

[0048] The porous graphite and the special structure graphite baffle are used on the surface of the material zone of the growth crucible, and the hole design in the special position of the rear cavity of the seed crystal holder realizes the function of transporting the sublimated material in a specific direction.

[0049] The seed crystal is combined in a specific direction, so that the reverse material transport is perpendicular to the direction of the step flow.

[0050] The application designs a simple and feasible guiding device for the PVT crystal growth process, which can effectively control the material transport path by the physical barrier step blocking structure, the rear cavity guiding and the special direction placement of the seed crystal, so that the material is always transported along the specific direction of the growth interface step flow, thereby effectively improving the stability and repeatability of the crystal growth, improving the crystal quality and reducing the dislocation density of the crystal.

[0051] Although the embodiments of the application have been shown and described, it is to be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the application, and the scope of the application is defined by the appended claims and their equivalents.​

Claims

1. A PVT crystal growth crucible capable of current conduction, comprising a growth crucible, an induction coil, a seed crystal holder, and a current conduction source device, wherein the growth crucible is wrapped with an insulating felt, induction coils are provided on both sides of the insulating felt, the bottom of the growth crucible contains silicon carbide powder, a porous graphite filter plate is provided on the upper part of the silicon carbide powder, a current conduction hole is provided in the rear cavity of the seed crystal holder on the top cover plate of the growth crucible, a seed crystal holder is provided below the cover plate, and a seed crystal is adhered to the seed crystal holder, characterized in that: The flow source device comprises a porous graphite filter plate and a flow-guiding graphite baffle. The porous graphite filter plate has a porosity of 40%~75%, a diameter of 130mm~250mm, and a thickness of 1mm~3mm. Its diameter is equal to the inner diameter of the corresponding crucible material area. The flow-guiding graphite baffle has a porosity of less than 35%, a diameter of 130mm~250mm, a thickness of 1mm~3mm, and a distance of 2~20mm between its lower surface and the porous graphite filter plate. The flow-guiding graphite baffle has an opening on one side, with an arc length of one-quarter to one-third of the circumference of the flow-guiding graphite baffle. Inside the opening, there is a graphite baffle perpendicular to the porous graphite filter plate, with a thickness of 1mm~3mm and a height of 10~50mm. The distance from the plane of the graphite baffle to the seed crystal is 50~100mm.

2. The PVT crystal growth crucible capable of flow guidance according to claim 1, characterized in that: The seed crystal holder's rear cavity guide hole is located within one-third of the circumference of the guide graphite baffle. The shape of the hole can be circular, square, rectangular, or any shape. The number of holes is 1 to 20, and the total through area of ​​the holes is between 10 and 500 mm². 2 .

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