CVD & Converter Process Technology

Process Technology for Silicon Production

Poly Plant Project (PPP) provides our customers with an advanced, proven technology package for high yield, high purity silicon production. The silicon production process technology package contains two (2) components: Reactor Building Configuration and Polysilicon Formation by Trichlorosilane (TCS) Decomposition Technology. PPP’s technology has been implemented at multiple plants successfully.

Reactor Building Layout

Through experience at multiple polysilicon plants, PPP developed an optimized building, piping, and equipment layout design. PPP’s design reduces the capital expense (Capex) by minimizing the footprint required per kilogram of polysilicon produced. PPP’s design also reduces the operating expense (Opex) by efficiently locating equipment and piping to minimize the turn-around time during each Reactor cycle.

Polysilicon Formation by Trichlorosilane (TCS) Decomposition:

The production of polysilicon is a batch process. For ease of understanding, the following overview describes conditions during the deposition phase, when the Reactor is in operation.

The process begins when liquid TCS and Hydrogen Gas are pumped separately into the Reactor Building from local storage tanks. The purified liquid TCS is routed into a common header that feeds each of the Reactors in the Reactor Building. From the header, the liquid TCS is piped to the Fluid Delivery System (FDS). The FDS supplies a controlled amount of liquid TCS and hydrogen gas to the Reactor to ensure fastest, most efficient growth rate. The TCS vaporizer uses steam to change the liquid TCS/hydrogen mixture into superheated vapor. The TCS/hydrogen mixture is piped to the deposition Reactor at a pressure. This TCS/hydrogen mixture is injected into the Reactor through special inlet nozzles designed to optimize gas distribution in the Reactor. The TCS then decomposes onto silicon filaments to form heterogeneous (poly) silicon crystal.

Unreacted gases, consisting of TCS, Silicontetrachloride (STC), hydrogen, and anhydrous hydrogen chloride (HCl) are removed from the Reactor. This high temperature effluent gas mixture is sent through an off-gas cooling system and then sent to a Vent Gas Recovery (VGR) system for recycle. The vent gases are recycled and reused.