Key equipment

centrotherm has developed and constructed a CVD reactor for industrial silicon production. In the chemical vapor deposition process, silicon is deposited from the gas phase. Hydrogen (H₂) and ultra-clean trichlorosilane (TCS) are used as precursors which react to deposit silicon under high temperatures and high pressure.

• improved design/engineering
• proven process/technology
• low energy consumption: < 90 kWh/kg
• high capacity: up to 170 metric tons/year

The miniature version of the CVD reactor is an ideal analysis tool for silicon quality control. The reactor is also an excellent training tool for the CVD process. It is a very popular product as it is easy to use and highly automated.

• Operating pressure according to execution: 0.3 - 0.7 barg or 1.0 - 7.0 barg
• Trichlorosilane consumption: 20 kg/cycle
• Duration of deposition process: 12 - 14 hours
• Total duration of cycle: 16 hours

In addition to CVD-reactors centrotherm also supplies STC-TCS converters. They transform the silicon tetrachloride produced in the CVD process into trichlorosilane, which in turn is recycled into the process. Silicon production costs are significantly reduced thanks to the recovery of trichlorosilane.

• high conversion efficiency per cycle >16%
• high gas throughput: 3000 kg/h

The centrotherm multi-crystalline ingot furnace is designed for the production of multi-crystalline ingots from polysilicon pieces by directional solidification based on the vertical gradient-freeze method. The multi-crystalline ingot furnace consists of a stainless steel vacuum vessel with integrated water cooling. It contains an electro-mechanical opening and closing mechanism and comes with an integrated crucible loading tool. For process control it is fully automated and includes two independent adjustable heating zones.

• ingot weight up to 450 kg without feeding
• optimized hot zone for jumbo sized crucibles of 880 mm x 880 mm x 420 mm
• two independent adjustable heating zones and one integrated active cooling device for optimal process control
• Integrated loading and unloading tool
• full automation

The centrotherm vent gas recovery unit (VGR) is used for the treatment of both reactor and converter vent gas streams.
The VGR consists of a main process area with distillation columns and condensation units, supplied by a compressor unit and a refrigeration unit. The basic design already includes enhanced condensation capacity and separate condensate tank for converter quench gas stream.

• designed for 2500 t/a polysilicon production
• Distillation column for TCS/STC separation can be integrated into the VGR unit without additional interfaces
• Ultra-low temperature processes are applied to achieve highest recovery rates for all compounds of the vent gas stream
• HCl buffer tank can be included to adjust HCl supply pressure and flow to actual needs of associated units.