Method of making self-aligned differently doped regions by controlled thermal flow of photoresist layer

Claim 1

A process for the self-alignment of differently doped regions in a silicon substrate, comprising the steps of: (a) coating this substrate with successive layers of thin silica, silicon nitride and photosensitive resin, (b) opening in a corresponding way windows in the resin and nitride layers, while maintaining nitride regions covered with resin, (c) causing the resin to flow in a controlled way with overflowing with respect to the nitride regions to define a first implantation mask, (d) implanting a first dopant, (e) removing by selective etching the resin layer, (f) increasing the thickness of the thin oxide layer at the positions not covered with nitride, (g) removing by selective etching the nitride regions, (h) using the second mask defined by the differences of thickness of the remaining oxide layer to implant a second dopant.