Process for growing phi 8'' solar-grade Czochralski silicon by using 18-inch thermal field

Abstract

The invention discloses a process for growing phi 8'' solar-grade Czochralski silicon monocrystalline by using an 18-inch thermal field. By adopting the 18-inch thermal-shielding thermal field and an upper-shaft magnetic fluid sealing device with a cooling system and combining the optimized parameter conditions of crystal-pulling processes, the invention enables the thermal field to have good heat preservation and obviously reduced energy consumption, enables gas to smoothly flow to be beneficial for the exhaustion of volatile matter, stabilizes crystallization, prolongs the service life of equipment and reduces the production cost; and in addition, the invention reduces magnet demagnetization and the evaporation of a magnetic fluid to avoid the air leakage and the slag dropping of the sealing of the magnetic fluid affecting the growth of the Czochralski silicon monocrystalline, improves the sealing performance and prolongs the service life, thereby ensuring the crystal-pulling processes of crystal leading, diameter equalization, shoulder rotation and the like to be stable and improving production efficiency and yield.

Description

technical field [0001] The invention relates to the technical field of direct silicon single crystal technology, in particular to a process for growing a Φ8" solar-grade Czochralski silicon single crystal in an 18-inch thermal field. Background technique [0002] At present, the mainstream product of Czochralski monocrystalline silicon in the world is 8 inches, gradually transitioning to 12 inches, and the development level reaches 16-18 inches. According to statistics, the global consumption of 8-inch silicon wafers accounts for about 60%, 6-inch silicon wafers account for about 20%, and the rest account for about 20%. [0003] The overall level of Czochralski monocrystalline silicon products in China is still low, and the product structure is dominated by 4-inch, 5-inch, and 6-inch silicon monowafers. The market demand for 6-inch and 8-inch silicon wafers is growing very strongly. The solar wafer market Growth is the main source of motivation. However, there are very few...

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Problems solved by technology

[0012] Disadvantages of the 18-inch open thermal field: poor heat preservation of the thermal field, resulting in high energy consumption; unsmooth gas flow, which is not conducive to the discharge of volatiles, unstable crystal formation, and low yield; longitudinal temperature at the head and tail of the single crystal The gradient changes greatly, the casting speed drops greatly, the overall casting speed is low, and the production efficiency is low; due to the high power used, the service life of the graphite parts in the thermal field is low, which increases the production cost

[0014] The problems of the above-mentioned magnetic fluid sealing device: due to the certain limitation of the working environment and service conditions of the magnetic fluid seal, its service life will be affected if it exceeds the range. Crystal growth, the main reason is that the temperature of the working environment of the magnetic fluid seal is too high, and the working temperature of the magnetic fluid should generally not be higher than 105°C; and now all TDR-80 and JRDL-800 models use a Φ18″ thermal field, and the furnace The temperature of the internal thermal field can reach more than 1700°C, and the radiant heat keeps the magnetic fluid sealed in a high-temperature environment. The increase in temperature will lead to the demagnetization of the magnet and the evaporation of the magnetic fluid

[0016] Defects of the prior art Φ18″ open thermal field Φ8″ silicon single crystal growth process: short seeding length results in insufficient removal of dislocations, crystals are prone to broken edges in the middle; the average pulling speed of equal diameters is low, and the efficiency is too low; Too fast, it is easy to cause the crystal formation interface to be unstable when pulling a large-diameter single crystal

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