Fabrication of semiconductor devices

Claim 1

Process for fabricating semiconductor devices which comprises: a. providing a semiconductor substrate; b. applying to the front surface of said substrate a laminated impurity diffusion masking system consisting of a layer of Si3N4 sandwiched between layers of SiO2; c. etching diffusion windows through said diffusion masking system to expose diffusion surfaces of said substrate; d. depositing a layer of SiO2 over the back surface of said substrate and another layer of SiO2 over the front of said substrate; e. heat treating the structure of step (d); f. depositing a layer of impurity oxide onto said layer of SiO2 deposited on the front surface of said substrate in step (d); g. depositing a layer of SiO2 onto said layer of impurity oxide; h. heating the structure of step (g) to diffuse impurities from said impurity oxide into said semiconductor; i. etching from the structure of step (h) the oxide layers deposited in steps (d), (f) and (g); j. depositing a layer of SiO2 over the front surface of said substrate; k. etching windows through the SiO2 layer deposited in step (j) to expose selected areas of said substrate previously diffused with impurities by step (h); l. diffuse an additional amount of said impurities into said selected areas of said substrate; m. applying ohmic contact material in the desired pattern to the front surface of said substrate and in contact therewith at said selected areas; n. applying ohmic contact to the back surface of said substrate; o. affixing electrical leads to an external circuit and p. encapsulating the device.