Appearance colourless liquid Molar mass 135.45 g/mol Density 1.34 g/cm³ UN number 1295 | Formula HCl3Si Boiling point 31.8 °C Autoignition temperature 185 °C (365 °F; 458 K) | |
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Trichlorosilane is an inorganic compound with the formula HSiCl3. 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 silicone 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.
Contents
Production
Trichlorosilane is produced by treating powdered metallurgical grade silicon with blowing hydrogen chloride at 300 °C. Hydrogen is also produced, as described in the chemical equation:
Si + 3 HCl → HCl3Si + H2Yields of 80-90% can be achieved. The major byproducts are silicon tetrachloride (chemical formula SiCl4), hexachlorodisilane (Si2Cl6), and dichlorosilane (H2SiCl2), from which trichlorosilane can be separated by distillation.
It is also produced from silicon tetrachloride:
Si + 3 SiCl4 + 2 H2 → 4 HSiCl3Applications
Trichlorosilane is the basic ingredient used in the production of purified polysilicon.
Ingredient in hydrosilylation
Via hydrosilylation, trichlorosilane is a precursor to other useful organosilicon compounds:
RCH=CH2 + HSiCl3 → RCH2CH2SiCl3Some useful products of this or similar reactions include octadecyltrichlorosilane (OTS), perfluoroctyltrichlorosilane (PFOTCS), and perfluordecyltrichlorosilane (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 an injection molding tools.
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 with base to the toluene derivative with base.