CN-122013310-A - Method and device for adjusting balance of HTCVD long-crystal carbon and silicon

CN122013310ACN 122013310 ACN122013310 ACN 122013310ACN-122013310-A

Abstract

The invention provides a method and a device for adjusting balance of HTCVD long crystal carbon silicon. The device for adjusting the HTCVD long-crystal carbon silicon balance comprises a long-crystal furnace body, a seed crystal lifting mechanism, an air inlet structure and a heat insulation structure, wherein the air inlet structure comprises an air inlet passage formed by inner and outer double air passages which are concentrically arranged, a built-in cooling section can stably keep high-byproduct gas below a cracking temperature and delay the cracking time of the high-byproduct gas after entering the furnace, and the air inlet structure can also effectively improve the mixing efficiency and convey mixed growth gas upwards to a seed crystal area in a uniform mode. The method for adjusting the balance of the HTCVD grown crystal carbon and silicon is characterized in that the growth gas is subjected to split-flow cooling and mixing at the initial stage of being introduced into the grown crystal furnace, and the gas discharge position is dynamically adjusted, so that the growth gas in the grown crystal furnace is fully mixed, the exposure time of the growth gas in a high-temperature area is reduced, and the generation of byproducts is effectively reduced.

Inventors

SHI YUCHEN
LIU XINYU
YUAN ZHENZHOU

Assignees

江苏超芯星半导体有限公司

Dates

Publication Date: 20260512
Application Date: 20260120

Claims (6)

1. A method for adjusting the balance of HTCVD long crystal carbon and silicon is characterized by comprising the following steps: Step 1, determining a by-product of a growth gas, namely selecting a corresponding carbon source gas and a silicon source gas according to the requirement of a crystal growth process, determining the cracking temperature T 1 of the carbon source gas and the cracking temperature T 2 of the silicon source gas, setting the carbon-silicon ratio of the growth gas, wherein C is Si=0.9-1.1:1, growing the silicon carbide crystal according to the preset condition of the crystal growth, checking the by-product condition at the crystal position after the end, and estimating the mass ratio of the carbon-containing by-product to the silicon-containing by-product; Dividing the growth gas paths, namely dividing the two growth gases into high-byproduct growth gas and low-byproduct growth gas by comparing the mass of the carbon-containing byproducts and the mass of the silicon-containing byproducts, and independently conveying the two growth gases without mixing before the growth gases are introduced into a crystal growth furnace; Step 3, arranging a growth gas inlet path, which specifically comprises the following steps: Step 3A, arranging a path I, namely conveying the growth gas with high byproducts in the growth furnace in the earlier stage, inserting the bottom end of the path I into the air inlet end of the growth furnace, determining the isotherm position of the growth gas inlet side reaching max (T 1 ,T 2 ) in the growth furnace according to the simulation result of the thermal field in the growth furnace, and enabling the distance between the isotherm position and the bottom end of the path I to be h 1 , wherein the length of the path I is l 1 , and adopting water cooling from the bottom end to the top end for cooling, wherein l 1 ＞h 1 ; Step 3B, arranging a second path, wherein the second path is used for conveying low-byproduct growth gas in the crystal growth furnace in the earlier stage, the bottom end of the second path is inserted into the air inlet end of the crystal growth furnace, and the distance between the starting position of the second path tapered structure and the bottom end is l 2 , wherein l 2 ＞l 1 ; Step 3C, arranging a transition structure, wherein the top ends of a first path and a second path are both opened, then the growth gas is mixed and introduced into the transition structure from the same path, the bottom end of the transition structure is communicated with the first path and the second path, the transition structure is a conical gradually-expanding structure from the bottom end to the top end, a plurality of through holes are formed in the top end of the transition structure in the direction facing to the seed crystal, and the transition structure is used for improving the deposition uniformity of the growth gas and controlling particles; And 4, regulating and controlling carbon-silicon balance of the growth gas, namely leading the fully mixed growth gas to a seed crystal, then growing the silicon carbide crystal, and regulating and controlling the preset condition of the grown crystal according to the defect condition of the crystal so that no obvious defect exists at the crystal.
2. The method for adjusting the balance of HTCVD long crystal carbon silicon according to claim 1, wherein the specific balance adjusting and controlling method in the step 4 is as follows: Step 4A, setting a carbon-silicon ratio of the growth gas, wherein the carbon-silicon ratio meets the requirement that C is Si=0.9-1.1:1, starting the growth of silicon carbide crystals after the two growth gases are fully mixed, and dividing the total time length of the growth stage of the silicon carbide crystals into i time units at equal intervals, wherein the unit names are T (i); Step 4B, enabling the distance between the seed crystal and the bottom end of the path I to be l 4 , enabling the distance between the top end of the transition structure and the bottom end of the path I to be l 5 , and enabling 2/3l 4 ≥l 5 to be always met, so that the distance l 3i between the top of the transition structure and the seed crystal is regulated; Step 4C, after the growth of the silicon carbide crystal is completed, dividing the silicon carbide crystal into different growth sections, recording the crystal height H (i) corresponding to each time unit T (i), and detecting the defect condition in the different growth sections; Step 4D, selecting two adjacent groups of data according to the crystal defect condition and the crystal height H (i), and recording the corresponding distances l 3n and l 3（n+1） between the top of the transition structure and the seed crystal; And 4E, repeating the steps 4A-4D, and controlling the distance between the top of the transition structure and the seed crystal to be kept between l 3n and l 3（n+1） obtained in the previous step D in the second and subsequent balance regulation methods until a silicon carbide crystal growth section without obvious defects is obtained.
3. The method of claim 2, wherein in step 4B, the distance between the seed crystal and the bottom of the path is l 4 , and the distance between the top of the transition structure and the bottom of the path is l 5 , wherein 2/3l 4 ≥l 5 is always satisfied.
4. The device for adjusting the balance of HTCVD long crystal carbon and silicon according to any of claims 1 to 3, which is characterized by comprising a long crystal furnace body, a seed crystal lifting mechanism and an air inlet structure; The seed crystal lifting structure comprises a seed crystal lifting rod and a seed crystal seat, wherein the seed crystal lifting rod is vertically inserted into the top of the crystal growing furnace body, one side of the seed crystal seat is arranged at the end part of the seed crystal lifting rod, which is close to one side of the center of the crystal growing furnace body, and the other side of the seed crystal seat is bonded with the seed crystal; The air inlet structure comprises an air inlet passage, a main air inlet pipe and a transition structure, wherein the air inlet passage is inserted at the bottom of the crystal growth furnace body, the air inlet passage is formed by an inner air passage and an outer air passage which are concentrically arranged, the inner air passage of the air inlet passage is a first path, the outer air passage of the air inlet passage is a second path, the bottom ends of the first path and the second path are respectively and hermetically inserted at the bottom of the crystal growth furnace body, the positions of the first path from the bottom end to the top end are respectively water-cooled sections, the starting position of the contracted structure is l 2 from the bottom end, l 2 ＞l 1 , the top ends of the first path and the second path are respectively opened, one end of the main air inlet pipe is connected with the top end of the second path, the other end of the main air inlet pipe is connected with the bottom end of the transition structure, the transition structure is in a conical gradually-expanded structure from the bottom end to the top end, and a plurality of through holes are formed in the direction facing the seed crystal.
5. The device of claim 4, wherein the second top opening is higher than the first top opening, the second top opening is tapered, and the first top opening, the second top opening, the main air inlet pipe and the transition structure are connected to each other.
6. The device for adjusting HTCVD long crystal carbon silicon balance of claim 4, further comprising a heat preservation structure, wherein the heat preservation structure comprises a heat preservation crucible and an induction heating coil, the heat preservation crucible is arranged above the bottom of the long crystal furnace body, the heat preservation crucible is arranged outside the air inlet structure and the seed crystal in a surrounding manner, and the induction heating coil is arranged outside the outer wall surface of the long crystal furnace body in a surrounding manner and is used for heating the heat preservation crucible in the long crystal furnace body to keep the growth temperature of the silicon carbide crystal.

Description

Method and device for adjusting balance of HTCVD long-crystal carbon and silicon Technical Field The invention belongs to the field of silicon carbide crystal growth, and relates to a method and a device for adjusting balance of HTCVD long crystal carbon silicon. Background Silicon carbide (SiC) is used as a representative of a third-generation wide-bandgap semiconductor material, and has great application potential in the fields of power electronic devices, radio frequency devices and the like due to the advantages of excellent wide bandgap, high breakdown field strength, high thermal conductivity, high electron saturation drift speed, chemical stability, low defect density and the like. A high quality, large size SiC single crystal substrate is therefore the core foundation for the fabrication of the high performance devices described above. At present, the mainstream method for industrially preparing the SiC monocrystal substrate is a Physical Vapor Transport (PVT) method, however, the PVT method has some inherent limitations, such as high difficulty in controlling the purity of a growth environment, slow growth rate, difficulty in monitoring and accurately regulating the growth process in real time and the like. To overcome PVT disadvantages, part of the growth work uses high temperature chemical vapor deposition as an alternative growth technique, which is typically carried out at temperatures up to 2200 ℃ to 2500 ℃, with high purity silane (SiH 4), ethylene (C 2H4), ethane (C 2H6) or propane (C 3H8) gases as precursors for the silicon and carbon sources, carried directly to the high temperature deposition zone with an inert carrier gas such as argon or hydrogen. Under the high-temperature environment, the precursor gas is subjected to thermal decomposition and chemical reaction to generate silicon and carbon active groups, chemical vapor deposition is carried out on the surface of the seed crystal, and finally the homoepitaxial growth of the silicon carbide single crystal is realized. However, in the process of growing SiC crystals by HTCVD, the silicon source gas and the carbon source gas need to be mixed and cracked in a high temperature reaction chamber, and since the temperature of the growth region is typically higher than 2000 ℃, which is much higher than the cracking temperature of the growth gas, part of the growth gas will be converted into by-products that have an effect on the crystal quality in advance before cracking synthesis. Meanwhile, as the cracking temperature and the cracking rate of the two growth gases are different, the cracking efficiency is difficult to control, and under the condition of the same carbon-silicon ratio, the rest single carbon source or silicon source gas is not deposited on the seed crystal to form SiC, and a layered structure is deposited on the furnace wall, the crucible edge and the thermal field structure, so that the waste of raw material gas, the service life of the internal structure of the furnace body and the like are caused. Therefore, it is now necessary to develop a method and a device for adjusting HTCVD long-crystal carbon silicon balance, which can avoid the generation of more byproducts of the growth gas due to the excessively high ambient temperature, improve the mixing efficiency of the two growth gases, and adjust the carbon silicon proportion within the balance range. Disclosure of Invention The invention aims to solve the technical problems of the prior art and provides a method and a device for adjusting the balance of HTCVD long crystal carbon silicon, which are characterized in that the method comprises the steps of carrying out split-flow cooling and mixing on the growth gas at the initial stage of introducing the growth gas into a long crystal furnace, and the gas discharge position is dynamically regulated, so that the growth gas in the crystal growth furnace is fully mixed, the exposure time of the growth gas in a high-temperature area is reduced, the generation of byproducts is effectively reduced, and the risk of producing a wrapper is reduced. In order to solve the technical problems, the invention adopts the following technical scheme: the invention provides a method for adjusting balance of HTCVD long crystal carbon silicon, which comprises the following steps: And 1, determining a by-product of a growth gas, namely selecting a corresponding carbon source gas and a silicon source gas according to the requirement of a crystal growth process, determining the cracking temperature T 1 of the carbon source gas and the cracking temperature T 2 of the silicon source gas, setting the carbon-silicon ratio of the growth gas, wherein C is Si=0.9-1.1:1, performing silicon carbide crystal growth according to the preset condition of crystal growth, checking the by-product condition at the crystal position after the end, and estimating the mass ratio of the carbon-containing by-product and the silicon-containing by-product. And 2, dividing the