Silicon deposition from SiCl 4 in a cold r.f. plasma: The effect of doping gases on deposition rates, chlorine content and the morphology of the films

Abstract

Silicon films were deposited in a cold r.f. plasma from a mixture of SiCl 4, H 2 and argon and were doped in situ by introducing B 2H 6 or PH 3 into the gas feed. The film thickness was measured by scanning electron microscopy and the content was determined by energy-dispersive X-ray analysis. The deposition rate and the chlorine content were reduced on addition of B 2H 6 and both were enhanced on addition of PH 3 to the gas mixture. The phenomena described were found to be independent of the substrate material or the deposition period. The morphology of the deposit was found to be different in the two types of films. Boron-doped films show a uniform growth proceeding by uniform coverage of the substrate, while phosphorus-doped films show an erratic growth proceeding by agglomeration of solid clusters at preferential sites. The different deposition rates are explained by differences in the surface morphology.