Highly reproducible zinc diffusions from 0.03 to 1.5 μm have been made into using a CVD zinc‐doped silica source capped with phosphosilicate glass. This structure permitted the use of an open‐tube, flowing inert gas diffusion system. Diffusions were made from 400° to 700°C, with surface hole concentrations from , and junction depths from 300Å to 1.5 μm. The diffusion coefficient and the hole concentration obtained by this technique are very close to those obtained by sealed ampul techniques using a source. However, this open‐tube system is more convenient to use, and gives highly reproducible results.