A new method for self-aligned Si-Zn diffusion was described. In this method, closed-tube Si diffusion was carried out by using a sputtered SiNx film. Then, Zn diffusion which was self-aligned to the Si diffusion window was carried out by re-using the SiNx film as a mask. The key factor was that the SiNx film should have the correct refractive index profile.

W.X.Zou, R.Boudreau, H.T.Han, T.Bowen, S.S.Shi, D.S.L.Mui, J.L.Merz: Journal of Applied Physics, 1995, 77[12], 6244-6