Implant mask reversal process

摘要

A reverse mask is formed after the first ion implantation step by applying a second masking material to at least fill the opening in the first mask layer and removing the second mask material to reveal at least a portion of the first mask layer. The first mask layer is then selectively removed with any superimposed second mask layer material thereon. This forms a truly inverse mask. Second conductivity impurities are then introduced through the inverse mask to form self-aligned complementary wells in a substrate.