Trenching techniques for forming vias and channels in multilayer

Abstract

Channels extending partially through and vias extending completely through an insulating layer in an electrical interconnect such as a substrate or integrated circuit can be formed in a relatively few steps with low cost etching and patterning techniques. The channels and vias can then be filled with an electrical conductor in a relatively few steps. In one embodiment a non-erodible hard mask exposing the vias and channels is placed over a polyimide layer, an erodible soft mask exposing the vias but covering the channels is placed over the hard mask, and a plasma etch is applied. The via regions are etched until the soft mask completely erodes and then both the via and channel regions are etched to provide partially etched channels and fully etched vias. Thereafter a seed layer is deposited over the interconnect, and an electrically conductive layer is electrolytically deposited over the seed layer substantially filling the channels and vias. The interconnect surface is then planarized by polishing until the electrical conductor remains only in the channels and vias.