The effect of selective masking, with WO3 electron resist, upon P diffusion and oxidation at 1000C was described. Although the diffusion coefficient of P in the WO3 layer was about twice as large as that in a SiO2 layer, the WO3 resist was found to be useful for masking P diffusion at temperatures of about 1000C. On the other hand, the masking effect of the WO3 layer upon the oxidation of a Si substrate was insufficient since the diffusion coefficient of O2 molecules in the WO3 layer was about 8 times as large as that in the SiO2 layer.

M.Baba, S.Abe, T.Ikeda: Japanese Journal of Applied Physics, 1987, 26[9], 1561-4