阅读说明：本技术 一种大直径碳化硅单晶及其制备方法 (Large-diameter silicon carbide single crystal and preparation method thereof ) 是由 魏汝省 李斌 毛开礼 周立平 戴鑫 靳霄曦 樊晓 于 2020-12-31 设计创作，主要内容包括：本发明提供了一种大直径碳化硅单晶及其制备方法,属于结晶生长技术领域。本发明提供的方法：将结晶物料,在籽晶、保护气氛下进行结晶生长；结晶生长结束后,将所得单晶进行原位退火处理,得到所述大直径单晶；所述结晶生长在坩埚中进行；采用2个加热线圈分别对所述坩埚的顶部和底部进行加热；对所述坩埚顶部进行加热的加热线圈中心与晶体生长界面在同一水平面上。本发明采用两个感应加热线圈分别对坩埚的顶部和底部进行加热,保持坩埚的顶部和底部温度差；结晶生长过程中,保持上线圈中心与晶体生长界面在同一水平面上,维持生长界面温场稳定性,减小结晶生长过程引入热应力；结晶生长结束后,对晶体进行原位退火处理,消除晶体内部热应力。(The invention provides a large-diameter silicon carbide single crystal and a preparation method thereof, belonging to the technical field of crystal growth. The method provided by the invention comprises the following steps: carrying out crystallization growth on the crystallized material under the conditions of seed crystals and protective atmosphere; after the crystal growth is finished, carrying out in-situ annealing treatment on the obtained single crystal to obtain the large-diameter single crystal; the crystal growth is carried out in a crucible; 2 heating coils are adopted to respectively heat the top and the bottom of the crucible; the center of a heating coil for heating the top of the crucible is on the same horizontal plane with a crystal growth interface. The invention adopts two induction heating coils to respectively heat the top and the bottom of the crucible, and keeps the temperature difference between the top and the bottom of the crucible; in the crystal growth process, the center of the upper coil and the crystal growth interface are kept on the same horizontal plane, the stability of a growth interface temperature field is maintained, and the thermal stress introduced in the crystal growth process is reduced; after the crystallization growth is finished, the crystal is subjected to in-situ annealing treatment to eliminate the internal thermal stress of the crystal.)

1. A method for producing a large-diameter silicon carbide single crystal is characterized by comprising the following steps:

carrying out crystallization growth on the silicon carbide crystallization material under the conditions of seed crystals and protective atmosphere;

after the crystallization growth is finished, carrying out in-situ annealing treatment on the obtained crystal to obtain the large-diameter silicon carbide single crystal;

the crystal growth is carried out in a crucible; 2 heating coils are adopted to respectively heat the top and the bottom of the crucible;

in the crystal growth process, the center of a coil for heating the top of the crucible and a crystal growth interface are on the same horizontal plane.

2. The method according to claim 1, wherein the silicon carbide crystal mass further comprises, before the crystal growth, evacuation, temperature rise to a heating temperature and filling of a protective atmosphere, which are performed in this order.

3. The method according to claim 1, wherein the pressure for crystal growth is 5 to 50 mbar.

4. The method according to claim 1, wherein the temperature at the top of the crucible is 2000-2200 ℃ and the temperature at the bottom of the crucible is 2200-2400 ℃ during the crystal growth.

5. A production method according to claim 1 or 4, wherein the temperature at the bottom of the crucible during the crystal growth is 200 ℃ higher than the temperature at the top of the crucible.

6. The method according to claim 1, wherein a downward moving speed of a heating coil for heating the top of the crucible is 50 to 500 μm/h and a heating coil for heating the bottom of the crucible is kept in a fixed state during the crystal growth.

7. The method as claimed in claim 1, wherein the temperature at the top of the crucible is the same as the temperature at the bottom of the crucible during the in-situ annealing process.

8. The preparation method according to claim 7, wherein the pressure of the in-situ annealing treatment is 100-800 mbar and the time is 2-20 h; the temperature of the top and the temperature of the bottom of the crucible are both 2200-2400 ℃.

9. The preparation method according to claim 1, 7 or 8, characterized by further comprising cooling the obtained single crystal after the in-situ annealing treatment is finished, wherein the cooling rate is 40-100 ℃/h.

10. A large-diameter silicon carbide single crystal obtained by the production method according to any one of claims 1 to 9, wherein the diameter of the large-diameter silicon carbide single crystal is 4 to 8 inches.

Technical Field

The invention relates to the technical field of crystal growth, in particular to a large-diameter silicon carbide single crystal and a preparation method thereof.

Background

The SiC material has the characteristics of large forbidden band width, high critical breakdown field strength, high electron mobility, high thermal conductivity and the like, and becomes an ideal material for manufacturing high-temperature, high-frequency, high-power, anti-irradiation, short-wave light-emitting and photoelectric integrated devices. The unique physical properties of SiC materials determine the application of the SiC materials in important fields such as artificial satellites, rockets, radars, communication, fighters, non-interference electronic ignition devices, jet engine sensors and the like. Therefore, a great deal of manpower and material resources are invested in various countries to carry out related technical research.

The development rate of the SiC-based wide band gap semiconductor technology is faster than that predicted previously, and development efforts are attracting attention. Advances in single crystal materials and epitaxial growth techniques have resulted in ever-increasing device performance. Some high performance devices and circuits have been tried in military equipment and have acquired satisfactory test data, and many other devices have been used in white light lighting, electric vehicles, wind power generation, solar power generation and other civilian systems. With the continuous improvement and optimization of the manufacturing technology of wide-bandgap semiconductor devices, the wide-bandgap semiconductor device is expected to be widely applied to various military weaponry systems and civil fields within 5-10 years in the future, so that the system performance is greatly improved.

A common method for producing large-diameter SiC crystals is Physical Vapor Transport (PVT). The SiC powder is placed at the bottom of a closed graphite crucible, a seed crystal is fixed at the top of the crucible, and a graphite heat-insulating material is placed outside the crucible. Heating the crucible by medium frequency induction to make the powder reach sublimation point and produce Si, C and SiC₂、Si₂C molecule driven by axial temperature gradientThe surface of the source material is transmitted to the surface of the seed crystal, and the source material is condensed on the surface of the seed crystal and slowly crystallized to achieve the purpose of growing crystals.

The induction heating method commonly used in the PVT growth method is used for heating the system, and the skin effect of the induction heating causes huge internal stress in the crystal.

With the progress of SiC crystal growth and device technology, the market demand for crystal size has increased gradually, from 2 inches to 4 inches to the current 6 inches, and the increase in crystal size has led to a continuous increase in the internal stress of the crystal during growth. The 4-8 inch SiC crystal is easy to crack along a cleavage surface in the growth, cooling and processing processes, so that the yield is greatly reduced, and the cost of a single wafer is overhigh. Meanwhile, the bending Bow and the warping Warp caused by stress in the wafer processing process are large, and the yield of the wafer is reduced.

Disclosure of Invention

In view of the above, an object of the present invention is to provide a large-diameter silicon carbide single crystal and a method for producing the same, which can produce a low-stress large-diameter single crystal.

In order to achieve the above object, the present invention provides the following technical solutions:

the invention provides a preparation method of a large-diameter silicon carbide single crystal, which comprises the following steps:

carrying out crystallization growth on the silicon carbide crystallization material under the conditions of seed crystals and protective atmosphere;

after the crystallization growth is finished, carrying out in-situ annealing treatment on the obtained crystal to obtain the large-diameter silicon carbide single crystal;

the crystal growth is carried out in a crucible; 2 heating coils are adopted to respectively heat the top and the bottom of the crucible;

in the crystal growth process, the center of a coil for heating the top of the crucible and a crystal growth interface are on the same horizontal plane.

Preferably, before the silicon carbide crystal material is subjected to crystal growth, the steps of vacuumizing, heating to a heating temperature and filling a protective atmosphere are sequentially carried out.

Preferably, the pressure for crystal growth is 5-50 mbar.

Preferably, in the crystal growth process, the temperature of the top of the crucible is 2000-2200 ℃, and the temperature of the bottom of the crucible is 2200-2400 ℃.

Preferably, during the crystal growth, the temperature at the bottom of the crucible is 200 ℃ higher than the temperature at the top of the crucible.

Preferably, in the crystal growth process, the downward moving speed of the heating coil for heating the top of the crucible is 50-500 μm/h, and the heating coil for heating the bottom of the crucible is kept in a fixed state.

Preferably, during the in-situ annealing treatment, the temperature at the top of the crucible is the same as the temperature at the bottom of the crucible.

Preferably, the pressure of the in-situ annealing treatment is 100-800 mbar, and the time is 2-20 h; the temperature of the top and the temperature of the bottom of the crucible are both 2200-2400 ℃.

Preferably, after the in-situ annealing treatment is finished, the obtained single crystal is cooled at a cooling rate of 40-100 ℃/h.

The invention also provides the large-diameter silicon carbide single crystal obtained by the preparation method in the technical scheme, and the diameter of the large-diameter silicon carbide single crystal is 4-8 inches.

The invention provides a preparation method of a large-diameter silicon carbide single crystal, which comprises the following steps: carrying out crystallization growth on the silicon carbide crystallization material under the conditions of seed crystals and protective atmosphere; after the crystallization growth is finished, carrying out in-situ annealing treatment on the obtained crystal to obtain the large-diameter silicon carbide single crystal; the crystal growth is carried out in a crucible; 2 heating coils are adopted to respectively heat the top and the bottom of the crucible; in the crystal growth process, the center of a coil for heating the top of the crucible and a crystal growth interface are on the same horizontal plane. The invention adopts two induction heating coils to respectively heat the top and the bottom of the crucible, and keeps the temperature difference between the top and the bottom of the crucible; in the growth process, the downward moving speed of a coil for heating the top of the crucible is accurately controlled, the center of the coil for heating the top of the crucible and a crystal growth interface are kept on the same horizontal plane, the stability of a growth interface temperature field is maintained, and the thermal stress introduced in the growth process is reduced; after the growth is finished, carrying out in-situ annealing treatment on the crystal to eliminate the internal thermal stress of the crystal; finally, the silicon carbide single crystal with low stress is obtained.

Drawings

FIG. 1 is a sectional view of a crucible for crystal growth according to the present invention, wherein 1 is a quartz tube, 2 is a heating coil for heating the top of the crucible, 3 is a heating coil for heating the bottom of the crucible, 4 is a heat insulating material, 5 is an upper temperature measuring hole, 6 is a lower temperature measuring hole, 7 is a crucible, 8 is a seed crystal, and 9 is a crystal material;

FIG. 2 is a photograph of a 6 inch N-type SiC substrate sheet obtained in example 1.

Detailed Description

The invention provides a preparation method of a large-diameter silicon carbide single crystal, which comprises the following steps:

carrying out crystallization growth on the silicon carbide crystallization material under the conditions of seed crystals and protective atmosphere;

and after the crystal growth is finished, carrying out in-situ annealing treatment on the obtained crystal to obtain the large-diameter silicon carbide single crystal.

The invention carries out crystal growth on the silicon carbide crystal material under the atmosphere of seed crystal and protection. In the present invention, before the silicon carbide crystal material is subjected to crystal growth, it is preferable that the steps of evacuating, raising the temperature to a heating temperature and filling a protective atmosphere are sequentially performed. The vacuum degree of the vacuum pumping is not particularly limited, and the air in equipment used for crystal growth can be pumped out. In the present invention, the heating temperature includes a temperature of the top of the crucible and a temperature of the bottom of the crucible; the temperature of the top of the crucible is preferably 1400 ℃, and the temperature of the bottom of the crucible is preferably 1600 ℃; in the present invention, the vacuum state is maintained during the temperature rise to the heating temperature. When the temperature of the top and the temperature of the bottom of the crucible reach corresponding temperatures, filling a protective atmosphere, wherein the protective atmosphere is preferably argon; the flow rate of the protective atmosphere is preferably 1000 sccm; when the atmosphere is filled to 800mbar, the temperature is continuously raised to the crystal growth temperature.

In the present invention, the crystal growth is carried out in a crucible; the seed crystal is adhered to the inner part of the upper cover of the crucible; the invention adopts 2 heating coils to respectively heat the top and the bottom of the crucible; in the crystal growth process, the center of a coil for heating the top of the crucible is positioned on the same horizontal plane with a crystal growth interface; the crystal growth interface is constantly moved in the crystal growth process, the center of a coil for heating the top of the crucible and the crystal growth interface are maintained on the same horizontal plane, and high stress brought by the crystal growth process can be avoided.

In the invention, in the process of crystal growth, the temperature at the top of the crucible is preferably 2000-2200 ℃, and further preferably 2100 ℃; the temperature of the bottom of the crucible is preferably 2200 to 2400 ℃, and more preferably 2300 ℃; the temperature at the bottom of the crucible is preferably 200 ℃ higher than the temperature at the top of the crucible; the downward moving speed of the heating coil for heating the top of the crucible is preferably 50 to 500 μm/h, more preferably 300 μm/h, and the heating coil for heating the bottom of the crucible is preferably kept in a fixed state. In the invention, the pressure for crystal growth is preferably 5-50 mbar, and more preferably 10 mbar; the time for the crystal growth is preferably 100 hours.

FIG. 1 is a sectional view of a crucible for crystal growth of the present invention, wherein 1 is a quartz tube, 2 is an upper heating coil, 3 is a lower heating coil, 4 is a heat insulating material, 5 is an upper temperature measuring hole, 6 is a lower temperature measuring hole, 7 is a crucible, 8 is a seed crystal, and 9 is a crystal material.

After the crystal growth is finished, the invention carries out in-situ annealing treatment on the obtained crystal to obtain the large-diameter silicon carbide single crystal. In the invention, during the in-situ annealing treatment, the temperature at the top of the crucible is the same as that at the bottom of the crucible. In the invention, the pressure of the in-situ annealing treatment is preferably 100-800 mbar, and particularly preferably 800 mbar; the top temperature and the bottom temperature of the crucible are both preferably 2200-2400 ℃, and particularly preferably 2300 ℃; the time of the in-situ annealing treatment is preferably 2-20 hours, and more preferably 10 hours.

After the in-situ annealing is finished, the invention preferably further comprises cooling the crystal obtained by the in-situ annealing to room temperature. In the invention, the cooling rate is preferably 40-100 ℃/h, and more preferably 60 ℃/h.

In the present invention, after the temperature of the crystal is reduced to room temperature, the single crystal is preferably subjected to rounding, cutting, grinding, chamfering, polishing, chemical mechanical polishing, cleaning and packaging processes, and the parameters of the processes are not particularly limited in the present invention, and technical means known to those skilled in the art can be adopted.

The invention also provides the large-diameter silicon carbide single crystal obtained by the preparation method in the technical scheme, and the diameter of the large-diameter silicon carbide single crystal is preferably 4-8 inches.

The large-diameter silicon carbide single crystal and the method for producing the same according to the present invention will be described in detail with reference to examples, but they should not be construed as limiting the scope of the present invention.

Example 1

The first step is as follows: 2500g of high purity SiC powder was charged into a 6-inch graphite crucible for SiC single crystal growth.

The second step is that: a6 inch seed crystal was bonded to the crucible top lid, which was secured to the top of the crucible.

The third step: the crucible is placed in a single crystal growth furnace.

The fourth step: and coating graphite heat-insulating materials on the periphery of the crucible for heat insulation.

The fifth step: sealing the growth furnace; an infrared thermometer is placed at the top to test the temperature at the top of the crucible.

And a sixth step: vacuumizing and heating the crucible to 1400 ℃ at the top and 1600 ℃ at the bottom of the crucible.

The seventh step: introducing Ar gas protective gas into the furnace cavity, wherein the flow rate is 1000sccm, the pressure is 800mbar, and the crucible is continuously heated to the temperature of 2100 ℃ at the top of the crucible and 2300 ℃ at the bottom of the crucible.

Eighth step: the temperature is kept unchanged, the pressure is reduced to 10mbar of crystal growth pressure, and the silicon carbide powder begins to be decomposed into Si and SiC at high temperature₂、Si₂C, etc. gas phase component and introducing into crucibleThe crucible cover is transported, the SiC crystal starts to grow, and the growth time is 100 hours.

The ninth step: controlling the coil to move in the crystal growth process, wherein the downward moving speed of the upper coil is 300 mu m/h; the lower coil is fixed.

The tenth step: after the crystal growth is finished, filling Ar gas into the cavity to 800 mbar; meanwhile, the temperature of the top of the crucible is increased by 2300 ℃; and carrying out in-situ annealing treatment on the crystal, and maintaining for 10 hours.

The eleventh step: and (4) after the in-situ annealing treatment is finished, cooling is started, the cooling rate is 60 ℃/h, and the temperatures of the top and the bottom of the crucible are kept consistent in the cooling process.

The twelfth step: and (5) after the temperature reduction is finished, taking out the crucible and the crystal, and finishing the whole growth process.

The 6-inch N-type SiC substrate slice which can be used after opening the box is finally obtained after the processes of rounding, cutting, grinding, chamfering, polishing, chemical mechanical polishing, cleaning, packaging and the like are carried out on the crystal.

FIG. 2 is a photograph of a 6-inch N-type SiC substrate sheet obtained in this example, as seen in FIG. 2: the N-type SiC substrate piece obtained in this example did not crack, indicating that the N-type SiC substrate piece had a small stress.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.