Process for providing self-aligned doping regions by ion-implantation and lift-off

Claim 1

A process for providing ion-implanted regions in a semiconductive substrate beneath preselected regions of an existing layer on said substrate and self-aligned to preselected subsequently fabricated regions of said layer which comprises: A. providing a semiconductive substrate; B. providing a first layer of a material above said substrate, beneath preselected portion of which is to be subsequently formed said ion-implanted regions; C. providing a resist mask above said layer wherein the sidewalls of said resist mask are perpendicular to the upper surface of the substrate or are undercut; D. ion-implanting impurities through said layer in those regions not covered by said resist mask, to provide ion-implanted regions beneath said first layer; the relative thickness of said layer and the combined layer and resist mask being such that the resist mask and portion of said layer beneath it are sufficiently thick so as to prevent ions from penetrating therethrough; E. depositing by sputtering or evaporating a layer of lift-off material on said first layer and said resist layer wherein the thickness of said layer of lift-off material is less than the thickness of said resist to a sufficient extent that no lift-off material is deposited on the sidewalls of said resist and a gap is formed between the resist layer and the portion of the lift-off material which is above said first layer but not above said resist layer; F. removing said resist layer by dissolving and thereby also removing along with said resist layer, said layer of lift-off material which was deposited on said resist layer; G. removing that portion of said first layer which was beneath said resist layer; H. removing said layer of lift-off material from above said first layer; and I. obtaining thereby ion-implanted regions self-aligned at the edges to preselected fabricated regions located above the ion-implanted regions.