Polysilicon / TCS / monosilane
Degree of purity of more than 99.9999 %. If required,
electronic grade also possible.
Silicon is a constituent of many minerals. Indeed it is the second most common element in the earth’s crust after oxygen. Elemental silicon is used and classified in various degrees of purity. The solar industry manufactures and processes solar grade silicon (Sisg). Its impurities amount to less than 0.0001 percent. The solar industry is increasingly using even higher purities, even up to electronic grade (Sieg).
The EPC Group’s portfolio of services covers not only the planning and provision of equipment for synthesizing TCS and vent gas recovery systems, but also rectification units, which require the know-how of experienced experts. We also provide you with the ancillary plants, infrastructure systems and construction planning services for complete factories. Production methods for TCS and polysilicon Elemental silicon is obtained on an industrial scale by reducing silicon dioxide with activated carbon in a melt. This produces silicon that is sufficiently pure for metallurgical purposes. However, the silicon has to be purified even further to obtain polycrystalline silicon (Sisg). This is done e.g. with the aid of a Siemens method that has been further developed by EPC.
The first step is to mix the metallurgical silicon with gaseous hydrogen chloride. This produces hydrogen, which is removed, and trichlorosilane, which is purified in further distillation stages. In the subsequent CVD process, gaseous TCS is fed into separation reactors in which ultrapure silicon is deposited on up to 54 hot silicon rods.
The production cycle of each CVD reactor finishes after about 4 days, after which the polycrystalline silicon is “harvested”. Silicofluidizedn tetrachloride is formed as a byproduct. This is converted back to trichlorosilane in a fluidized bed-reactor, and fed back into the production cycle. This conversion reactor can also be designed to be the sole source of TCS.
Polysilicon and TCS – EPC offers turnkey plants for your PolySi production. They have the following advantages:
- A degree of purity greater than 99.9999%, electronic grade is also possible if required
- Intelligent revamping concepts reduce the total per kg cost of producing Si
- Overall energy consumption is reduced by, for example, recovering energy
- In-house TCS production, mainly supplied by hydrogenation conversion, including separation and rectification
- Integration into the existing production location and the existing infrastructure
- Extension of the existing value chain (ingots, wafers, cells)
- Greater competitiveness in the world market