Method of forming a silicon nitride diffusion mask

Claim 1

In the manufacture of semiconductor devices wherein impurity atoms are selectively introduced into a surface of a semiconductor body, the improvement comprising the steps of: a. providing a body of semiconductor material having an upper surface and being of a first conductivity-type; b. forming a layer of silicon dioxide over said upper surface; c. depositing a film of silicon nitride characterized by a relatively low density on said layer of silicon surface dioxide; d. selectively etching said film and said silicon dioxide to delineate a desired masking pattern and for exposing a portion of said upper surface of said semiconductor body; e. heating said silicon nitride film to increase the density thereof and improve the masking and passivating properties of said film; f. forming by diffusion a region of opposite conductivity-type in said body underlying said exposed upper surface, and said region forming a junction with said body terminating at said upper surface and under said layer of silicon dioxide and simultaneously forming by said step of diffusion a layer of silicon dioxide over said exposed upper surface; g. etchably removing said last mentioned silicon dioxide film without exposing said junction protected by said layers of silicon dioxide and silicon nitride; and h. forming an electrical contact adhering to said exposed upper surface.