Single crystal silicon and polysilicon technology

The difference between monocrystalline silicon and polysilicon is that when the molten silicon is solidified, the silicon atoms are arranged in a lattice of diamonds into a plurality of crystal nuclei, and if these crystal nuclei grow into crystal grains with the same crystal plane orientation, single crystal silicon is formed. If these crystal nuclei grow into crystal grains with different crystal orientations, polysilicon is formed. The difference between polysilicon and monocrystalline silicon is mainly manifested in the physical properties. For example, in terms of mechanical properties, electrical properties, etc., polysilicon is not as good as monocrystalline silicon. Polysilicon can be used as a raw material for drawing monocrystalline silicon. Monocrystalline silicon can be regarded as the purest substance in the world. General semiconductor devices require silicon purity of more than six. The requirements for large-scale integrated circuits are higher, and the purity of silicon must reach nine nines. At present, people have been able to produce single crystal silicon with a purity of twelve nines. Monocrystalline silicon is an indispensable basic material in modern science and technology such as electronic computers and automatic control systems.

High-purity silicon is extracted in quartz. For example, monocrystalline silicon is extracted through the following process: quartz sand, metallurgical grade silicon, purified and refined, deposited polycrystalline silicon ingot, monocrystalline silicon, and silicon wafer.

The refining of metallurgical grade silicon is not difficult. Its preparation is mainly made by reducing quartz sand with carbon in an electric arc furnace. The purity of the silicon thus recovered is about 98-99%, but the silicon used in the semiconductor industry must also be highly purified (the purity of the electronic grade polysilicon requires 11 9 and the solar cell grade only requires 6 9). In the purification process, a key technology of “trichlorosilane reduction method (Siemens method)” has not yet been mastered in China. Without this technology, more than 70% of the polysilicon in the refining process in China is emitted through chlorine. Not only the refining costs are high, but the environmental pollution is very serious. Every year, China extracts a large amount of industrial silicon from quartz stones and exports them to countries such as Germany, the United States, and Japan at a price of US$1 per kilogram. These countries process industrial silicon into high-purity crystalline silicon materials for US$46-80. / Kilogram price sold to our solar energy companies.

After high-purity polycrystalline silicon is obtained, it is smelted in a single crystal furnace into single crystal silicon, which is then sliced ​​for use in integrated circuit manufacturing and the like.

What is monocrystalline silicon

It can be used in the production and deep processing of diode-level, rectifier-level, circuit-level and solar cell-level single crystal products. Its follow-up products integrated circuits and semiconductor separation devices have been widely used in various fields, and also occupy an important position in military electronic equipment. .

With the rapid development of photovoltaic technology and micro-miniaturized semiconductor inverter technology, solar cells produced using silicon single crystals can directly convert solar energy into light energy, thus realizing the beginning of the green energy revolution. The Beijing 2008 Olympic Games will display the “Green Olympics” as an important display for the world. The use of monocrystalline silicon will be a very important part of this. Now, foreign solar photovoltaic power plants have reached the theoretical maturity stage and are transitioning to the practical application stage. The utilization of solar silicon single crystals will be universally available and the market demand is self-evident. The Ningjin Single Crystal Silicon Industrial Park in Hebei responds to this international trend and provides the world with a single crystal silicon product with excellent performance and complete specifications.