Silane

Silane is the silicon cousin of methane: one silicon atom with four hydrogen atoms around it, SiH₄. It's a colorless gas that catches fire on its own in air, so it travels in steel cylinders and through carefully sealed pipes.

Most silane is made from trichlorosilane, the same liquid used to make ultra-pure polysilicon. Over a catalyst, trichlorosilane molecules swap hydrogen and chlorine atoms among themselves. Step by step, this redistribution gives silane plus silicon tetrachloride (SiCl₄). The silane is separated and purified, since even tiny traces of other elements would spoil electronic films. The silicon tetrachloride is recycled back into trichlorosilane.

Silane's value is that it breaks apart cleanly. Hit with heat or plasma, it leaves silicon behind and releases hydrogen gas. Alone, that gives films of amorphous silicon for the transistors in a display. Mixed with ammonia, it gives silicon nitride, the insulating and protective film. Chip factories and solar cell makers use it in the same ways.