PVT crystal growth crucible capable of realizing flow guide

Abstract

The invention discloses a PVT crystal growth crucible capable of realizing diversion, which comprises a growth crucible, an induction coil, a seed crystal support and a diversion source device, and can effectively realize accurate control of a material transportation path through cooperation of a physical blocking platform structure with rear cavity diversion and special direction placement of seed crystals. The material is always transported along the specific direction of the growth interface step flow, so that 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 invention relates to a PVT crystal growth crucible capable of achieving flow diversion. Background Art

[0002] With the rapid development of technology, facing the requirements of higher temperature tolerance, higher voltage, higher frequency and higher power of the new generation of electronic devices, silicon (Si), the most basic and widely used material in the semiconductor industry, is increasingly unable to meet these requirements due to its own physical and chemical properties. The discovery and development of the third generation of wide bandgap semiconductor materials represented by single crystals such as silicon carbide (SiC) and gallium nitride (GaN) has brought new hope for the development of the new generation of power electronic devices.

[0003] Compared with traditional silicon single crystals, silicon carbide single crystals have the advantages of wider band gap, higher saturated electron mobility, higher breakdown field strength, higher thermal conductivity, and more stable physical and chemical properties. In addition, after decades of development, the technology for preparing silicon carbide crystals is relatively mature, and it is the only single crystal among existing compound semiconductor materials that can form silicon dioxide insulators through thermal oxidation. Therefore, electronic devices prepared using silicon carbide single crystals have gradually replaced silicon-based devices in many fields, becoming 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 crystals have been continuously improved, showing irreplaceable advantages in the fields of high-power, high-temperature, high-frequency power electronics, optoelectronics, and special semiconductor devices, and have been widely used. However, the production efficiency and preparation cost of semiconductor devices are the core factors that restrict their wider application. For this reason, how to obtain higher quality and larger size silicon carbide single crystals, how to improve the preparation yield of single crystals, and how to reduce the cost of silicon carbide single crystals are common problems currently faced by the silicon carbide industry, and are also the common goal of everyone's struggle.

[0005] At present, the PVT method is the most widely used and mature method for preparing silicon carbide single crystals. In the process of preparing silicon carbide single crystals by the PVT method, due to the presence of a large number of isomers of silicon carbide crystals, polymorphic symbiosis is easily produced during the growth process, which leads to a significant decrease in the available area of ​​the crystal. In addition, the occurrence of micro-area polymorphism often induces the generation of dislocation defects. How to further reduce the dislocation defect density is also a research direction that the silicon carbide industry has been pursuing in recent years.

[0006] During the growth process of PVT, the structural information of silicon carbide crystals comes from the exposed area of ​​the sidewall of the growth step flow. Under certain temperature field conditions, driving the sublimated and volatilized materials from the raw material area to transport mass along a certain step flow in a specific direction is a necessary condition for maintaining a single 4H polytype in the growth process of silicon carbide, and is also an effective means to inhibit the nucleation of dislocation defects at the growth interface. Therefore, guiding the volatilized materials is a necessary and effective means for the growth of high-quality silicon carbide crystals.

[0007] During the PVT growth of silicon carbide crystals, the chamber pressure is at a very low value, usually only 1~20mbar, and its Rayleigh number condition is far below the threshold required for convection to occur. In other words, mass transport in the PVT silicon carbide crystal growth process is completely accomplished by thermal diffusion. Therefore, a reasonable design of a physical barrier guide structure is the key to achieving precise control of the mass transport process. The uniform sublimation process in the traditional PVT growth process cannot achieve precise control of material transport. There is a certain randomness in the material transport process, which will also lead to the growth process of each furnace not being able to perfectly repeat the ideal process conditions, which has a certain negative impact on the stability, quality and process repeatability of the grown crystals. Summary of the invention

[0008] The object of the present invention is to provide a PVT crystal growth crucible capable of achieving flow conduction, so as to solve the problems raised in the above-mentioned background technology.

[0009] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a PVT crystal growth crucible capable of flow diversion, comprising a growth crucible, an induction coil, and a seed crystal holder box flow diversion source device, wherein the growth crucible is wrapped with insulation felt, and induction coils are arranged on both sides of the insulation felt. The bottom of the growth crucible is silicon carbide powder, and a porous graphite filter plate is arranged on the top of the silicon carbide powder. A seed crystal holder rear cavity flow diversion hole is arranged on the top cover plate of the growth crucible, a seed crystal holder is arranged under the cover plate, and a seed crystal is adhered to the seed crystal holder. The flow diversion source device comprises a porous graphite filter plate and a flow diversion graphite baffle.

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

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

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

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. Through the special material transport direction, the structural information of the growth process is effectively inherited, and the occurrence of polymorphic symbiotic defects or micro-area polymorphic symbiotic defects is suppressed.

[0014] 2. Precise and controllable reverse material transport to prevent inconsistencies between furnaces or batches during the growth process.

[0015] 3. The boring material is transported continuously and stably, and the process is not prone to sudden changes, which is extremely beneficial to the growth and thickness of the crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 Schematic diagram of the flow-guiding graphite baffle; Figure 3 It is a schematic diagram of the guide hole in the rear cavity of the seed crystal plate and the seed crystal direction when assembled; Figure 4 This is a picture of a silicon carbide crystal with a diameter of 158 mm; Figure 5 This is the dislocation test result of a silicon carbide crystal with a diameter of 158mm; Figure 6 It is a silicon carbide crystal with a diameter of 164mm; Figure 7 This is the dislocation test result of a silicon carbide crystal with a diameter of 164mm.

[0017] In the figure: 1. induction coil; 2. insulation felt; 3. growth crucible; 4. silicon carbide powder; 5. porous graphite filter plate; 6. graphite guide baffle; 7. graphite baffle; 8. seed crystal holder; 9. guide hole in the back cavity of the seed crystal holder; 10. seed crystal; 11 opening, 12 growth facet. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] See also Figure 1-3 The present invention provides a technical solution: a PVT crystal growth crucible capable of achieving flow diversion, comprising a growth crucible 3, an induction coil 1, a seed crystal holder 8 and a flow diversion source device, wherein the growth crucible 3 is wrapped with an insulation felt 2, and an induction coil 1 is arranged on both sides of the insulation felt 2, the bottom of the growth crucible 3 is silicon carbide powder 4, a porous graphite filter plate 5 is arranged on the top of the silicon carbide powder 4, a seed crystal holder rear cavity diversion hole 9 is arranged on the top cover plate of the growth crucible 3, a seed crystal holder 8 is arranged under the cover plate, a seed crystal 10 is adhered to the seed crystal holder 8, and the flow diversion source device comprises a porous graphite filter plate 5 and a flow diversion graphite baffle 6.

[0020] The porous graphite filter plate has a porosity of 40% to 75%, a diameter of 130 mm to 250 mm, and a thickness of 1 mm to 3 mm. Its diameter is equal to the inner diameter of the corresponding crucible material area used; The porosity of the guide graphite baffle 6 is less than 35%, the diameter is 130mm~250mm, the thickness is 1mm~3mm, the lower surface is 2~20mm away from the porous graphite filter plate, one side of the guide graphite baffle is opened, the arc length of the opening is one quarter to one third of the circumference of the guide graphite baffle, and the inside of the opening is provided with a graphite baffle 7 perpendicular to the porous graphite filter plate, the thickness is 1mm~3mm, the height is 10~50mm, and the distance from the plane of the graphite baffle to the seed crystal is 50~100mm; The guide hole 9 of the rear cavity of the seed crystal holder is located within one third of the circumference of one side of the guide 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 opening area is between 10 and 500 mm. 2 .

[0021] When the seed crystal is assembled, the <11-20> direction, usually the location of the growth face 12, should point to the location of the guide hole, as shown in the schematic diagram. Figure 3 ; The 6-inch silicon carbide crystal prepared by this method usually has a thickness of 10-30 mm and a diameter of 150-170 mm.

[0022] The dislocation density indexes of the 6-inch silicon carbide crystal prepared by the method are usually EPD less than 1500, TSD less than 20, and BPD less than 100.

[0023] The 8-inch silicon carbide crystal prepared by this method usually has a thickness of 10-25 mm and a diameter of 200-220 mm. Example

[0024] (1) A 158 mm diameter crystal grown using the above method; (2) The diameter of the porous graphite sheet is 182 mm. The diameter of the graphite baffle is 155 mm, the arc length of the baffle opening 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.

[0025] (3) Three guide holes with a diameter of 5 mm are opened in the rear cavity of the seed crystal holder, and the center spacing of the guide holes is 20 mm.

[0026] (4) Use a seed crystal with a diameter of 155 mm. When assembling, its <11-20> direction should point to the guide hole in the rear cavity of the seed crystal holder.

[0027] (5) When the seed crystal holder is assembled with the crucible, the guide hole in the rear cavity is located at the countermeasure position of the graphite guide plate.

[0028] (6) The crystals grown are as follows Figure 4 As shown in Figure 1, the crystal diameter is 158 mm and the effective thickness is 22 mm. The dislocation data of the wafers cut from this ingot are as follows: Figure 5 As shown, its dislocation density value is significantly lower than the industry average. Example

[0029] (1) A 163 mm diameter crystal grown using the above method; (2) The diameter of the porous graphite sheet is 182 mm. The diameter of the graphite baffle is 155 mm, the arc length of the baffle opening 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.

[0030] (3) Three guide holes with a diameter of 5 mm are opened in the rear cavity of the seed crystal holder, and the center spacing of the guide holes is 22 mm.

[0031] (4) Use a seed crystal with a diameter of 160 mm. When assembling, its <11-20> direction should point to the guide hole in the rear cavity of the seed crystal holder.

[0032] (5) When the seed crystal holder is assembled with the crucible, the position of the back cavity guide hole is located at the countermeasure position of the graphite guide plate (6) The crystals grown are as follows Figure 6 As shown in Figure 1, the crystal diameter is 164 mm and the effective thickness is 18 mm. The dislocation data of the wafers cut from this ingot are as follows: Figure 7 shown.

[0033] The surface of the growth crucible material area adopts a structure of porous graphite + special structure graphite baffle, and the opening design at a special position of the rear cavity of the seed crystal holder realizes the function of transporting the sublimated material in a specific direction.

[0034] The seed crystals are assembled in a specific direction so that the material transport direction is perpendicular to the step flow direction.

[0035] A simple and feasible PVT crystal growth process diversion device was invented and designed, which can effectively achieve precise control of the material transport path through the physical barrier structure, the rear cavity diversion and the special direction of the seed crystal placement, so that the material is always transported along the specific direction of the step flow of the growth interface, effectively improving the stability and repeatability of crystal growth, improving the crystal quality, and reducing the crystal dislocation density.

[0036] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A PVT crystal growth crucible capable of achieving flow diversion, comprising a growth crucible, an induction coil, a seed crystal holder and a flow diversion source device, wherein the growth crucible is wrapped with a heat preservation felt, and induction coils are arranged on both sides of the heat preservation felt. The bottom of the growth crucible is silicon carbide powder, and a porous graphite filter plate is arranged on the top of the silicon carbide powder. A seed crystal holder back cavity flow diversion hole is arranged on the top cover plate of the growth crucible, and a seed crystal holder is arranged under the cover plate, and a seed crystal is adhered to the seed crystal holder, wherein the characteristics are: The flow guiding source device comprises a porous graphite filter plate and a flow guiding graphite baffle.

2. The PVT crystal growth crucible capable of achieving flow diversion according to claim 1, characterized in that: The porous graphite filter plate has a porosity of 40% to 75%, a diameter of 130 mm to 250 mm, and a thickness of 1 mm to 3 mm, and its diameter is equal to the inner diameter of the corresponding crucible material area used.

3. The PVT crystal growth crucible capable of achieving flow diversion according to claim 1, characterized in that: The guide graphite baffle has a porosity of less than 35%, a diameter of 130 mm to 250 mm, a thickness of 1 mm to 3 mm, a lower surface 2 to 20 mm away from the porous graphite filter plate, a hole is opened on one side of the guide graphite baffle, and the arc length of the hole is one quarter to one third of the circumference of the guide graphite baffle. There is a graphite baffle perpendicular to the porous graphite filter plate on the inside of the hole, with a thickness of 1 mm to 3 mm and a height of 10 to 50 mm. The distance from the plane of the graphite baffle to the seed crystal is 50 to 100 mm.

4. The PVT crystal growth crucible capable of achieving flow diversion according to claim 1, characterized in that: The guide hole of the seed crystal holder rear cavity is located within one-third of the circumference of one side of the guide graphite baffle. The shape of the opening can be circular, square, rectangular or any shape. The number of openings is 1 to 20, and the total opening area is between 10 and 500 mm. 2 .

Images