[geomark]

Ok. I was never a process guy, but worked with some back in the day and they told me that one of their phosphorus sources was phosgene gas.

[wrycoder]

Silane, phosphene, and diborane gases are used to form epitaxial layers on silicon wafers. Those are truly dangerous gases. However, a simple wafer process using the reagents I mentioned can produce very credible ICs, if one buys the epi wafers.