Polysilicon production process status and development trend

At present, the main international polysilicon production process is to improve the Siemens process, which accounts for more than 85% of the total production capacity. In 2010, polysilicon produced using this technology accounted for 86.6% of the world's total output of 167,000 tons.

The technology matured in the 1970s. After nearly 20 years of silence, along with the development of the photovoltaic industry, all countries in the world carried out secondary innovations on this technology. For example, Silicon Hightech broke through the large-scale low-temperature hydrogenation technology, large-scale energy-saving reduction furnace technology, High-efficiency pressurization distillation purification technology, high-pressure trichlorosilane synthesis technology, tail gas dry recovery technology, silicon tetrachloride production of gas-phase white carbon black technology and comprehensive utilization of thermal energy. With large-scale production, this technology still has room for improvement.

In recent years, with the expansion of its output, the improved Siemens technology has strengthened its competitiveness, and its mainstream craftsmanship has become more stable. It will remain the mainstream technology in the next 20 years or more. The improved Siemens process can meet the requirements of large-scale, safe and environmentally-friendly production because of its high purity and low production cost, and it has become the market's preferred mainstream process. From the cost point of view, the costs of WACKER and REC have been basically close, showing that the technology has a strong vitality. Here are some of the major polysilicon production methods.

1 Improved Siemens Process—Closed-loop trichlorosilane hydrogen reduction method The modified Siemens process uses chlorine and hydrogen to synthesize hydrogen chloride (or purchased hydrogen chloride), hydrogen chloride and industrial silicon powder to synthesize trichlorosilane at a certain temperature, and then The trichlorosilane is separated and purified by distillation, and the purified trichlorosilane is subjected to a CVD reaction in a hydrogen reduction furnace to produce high-purity polysilicon.

Most existing polysilicon plants at home and abroad use this method to produce electronic grade and solar grade polysilicon.

2 Silane Method - Silane thermal decomposition method Silane (SiH4) is prepared by hydrogenation of silicon tetrachloride, decomposition of silicon alloy, hydride reduction, and direct hydrogenation of silicon. The purified silane gas is then purified to produce rod-shaped polysilicon having a higher purity in a pyrolysis furnace. In the past, only Komatsu Japan had mastered the technology and did not continue to expand production after a serious explosion. However, American Asimi and SGS companies still use silane gas thermal decomposition to produce electronic grade polysilicon products with higher purity.