Trichlorosilane (TCS) is an inorganic compound with the formula HCl3Si. It is a colourless, volatile liquid. Purified trichlorosilane is the principal precursor to ultrapure silicon in the semiconductor industry. In water, it rapidly decomposes to produce a siloxane polymer while giving off hydrochloric acid. Because of its reactivity and wide availability, it is frequently used in the synthesis of silicon-containing organic compounds.[2]
Tank car of trichlorosilane. UN number: 2988 (Chlorosilanes). ADR hazard identification number: X338 (Highly flammable liquid, corrosive, which reacts dangerously with water)
It is also produced from silicon tetrachloride in a direct chlorination process:[3][4]
Si + 3 SiCl4 + 2 H2 → 4 HCl3Si
Both methods are widely used. The first method is cheaper but yield is hard to control. The second method doesn't require as much control, but needs twice as much capital investment and consumes 120 to 200 kWh/kg compared to 65-90 kWh/kg for the first method. The distillation of TCS purifies it substantially and with it, most of the impurities in the silicon are removed.[3]
Uses
Trichlorosilane is the basic ingredient used in the production of purified polysilicon.
Via hydrosilylation, trichlorosilane is a precursor to other useful organosilicon compounds:
RCH=CH2 + HSiCl3 → RCH2CH2SiCl3
Some useful products of this or similar reactions include octadecyltrichlorosilane (OTS), perfluoroctyltrichlorosilane (PFOTCS), and perfluorodecyltrichlorosilane (FDTS). These reagents used in surface science and nanotechnology to form self-assembled monolayers. Such layers containing fluorine decrease surface energy and reduce sticking. This effect is usually exploited as coating for MEMS and microfabricated stamps for a nanoimprint lithography (NIL) and in injection molding tools.[7]
Organic synthesis
Trichlorosilane is a reagent in the conversion of benzoic acids to toluene derivatives. In the first step of a two-pot reaction, the carboxylic acid is first converted to the trichlosilylbenzyl compound. In the second step, the benzylic silyl derivative is converted to the toluene derivative with base.[8]
↑George S. Li, David F. Ehler, R. A. Benkeser "Methyl Groups By Reduction Of Aromatic Carboxylic Acids With Trichlorosilane - Tri-n-propylamine: 2-methylbiphenyl" Org. Synth. 1977, volume 56, pp. 83. doi:10.15227/orgsyn.056.0083
