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Polykrystalline silicon (PKS) production

Polykrystalline silicon (PKS) is a strategic raw material of semiconductor industry. Mainly PKS is used for the receipt of monokrystalline silicon (MKS) and multisilicon (MS). In quality PKS divides into silicon of «sun» qualities and «electronic» qualities.

 
PKS of «electronic» qualities with the mass stake of admixtures - 10-7 ÷ 10-8 % is used in modern microelectronics, industrial and power electronics.
 
PKK of «sun» qualities is used in energy for the production of sun batteries.
 
The silicon of «metallurgical quality» with a purity to 98-99% is a raw material for the production of PKS.
 
The companies of the USA, Japan, Germany and Italy control more than 90% of world market of polykrystalline silicon.
 
Presently there is a deficit of PKS in the world, in this connection the programs on development of silicon production are accepted in a number of countries.
 
Before the USSR produced to 12% of world polykrystalline silicon, basic production capacities bedded in Ukraine and Kirghizia.
 
Is it possible to list Russian producers of polykrystalline silicon:
  • Podolsk chemical and metallurgical plant
  • Krasnoyarsk mining and chemical industrial complex (Zheleznogorsk city)
  • «Usolye-Sibirskiy Silicon» LTD of NITOL Group
 
Presently at enterprises of Russia monokrystalline silicon is produced from high-purity foreign raw material, therefore the development of polykrystalline silicon production remains an actual question.
 
The receipt of clean and ultrapure silicon requires the preliminary synthesis of the cleanest initial connections of silicon (SiCl4, SiHCl3, SiH4), from which silicon is extracted by renewal or thermal decomposition.
 
Traditionally “Siemens C” technology is used for the receipt of polykrystalline silicon, to which the basic part (>70%) of world production of polykrystalline silicon is belonged.
 
Trichlorosilane is synthesized by chlorinating from technical silicon which is clearing up by multistage rectification from the by-products of trichlorosilane synthesis - Н2, НСl, tetrachloride of silicon and is sending to the reactor of hydrogen renewal, where a process of subsidence of silicon on foundation bars is happening.
 
Selected at cleaning of synthesized trichlorosilane by-products return back in the cycle of production of PKS. Chlorous hydrogen returns to the synthesis of trichlorosilane, synthesized tetrachloride of silicon and part of hydrogen head for conversion of tetrachloride of silicon (transformation of tetrachloride of silicon to trichlorosilane ), other hydrogen is given to hydrogen renewal of silicon.
 
 
In the process of renewal of silicon in reactors besides a product – pure polykrystalline silicon – by-products appear that is a tetrachloride of silicon and chlorous hydrogen, which in mixture with uncreated hydrogen and trichlorosilane, and also with the products of conversion of tetrachloride of silicon head to the units, where a separation of Н2, НСl, and also division of circulating chlorosilanes at trichlorosilane and tetrachloride of silicon, which are returned in a technological process.

Circulating trichlorosilane with hydrogen go back into the reactors of renewal of silicon, chlorous hydrogen – to the synthesis of trichlorosilane, and the circulating tetrachloride of silicon is sent to converters for transformation to the trichlorosilane.

In 2007-2009 years two projects of polykrystalline silicon production with power 300 and 3000 t/year are executed by «LENNIIKHIMMASH» LTD.

The units of condensation of chlorosilane and fractionation of gas-vapour mixture were developed by the specialists of «LENNIIKHIMMASH» LTD on an original process flowsheet., including the receipt of high-pure products - tetrachlorated silicon, trichlorosilane, hydrogen and chlorous hydrogen with the purpose of their further return to the production cycle of polykrystalline silicon and also the unit of cleaning and neutralization of industrial effluents and off-gas, providing protecting of environment from harmful emissions.

The method of calculation of clearance of off-gases and utilization of industrial effluents of polykrystalline silicon production developed by «LENNIIKHIMMASH» LTD is applicable and for other products of semiconductor group.

LTD. «LENINIIKHIMMASH» also it A greater part of basic technological equipment of units, pipeline armature, and also devices of automation and testing equipment were developed, made and put on a ground by «LENNIIKHIMMASH» LTD.

Constructing of these units is presently conducted on. «Usol'e-Sibirskiy Silicon» LTD of NITOL Croup companies.