Method of making a three-dimensional memory device using composite hard masks for formation of deep via openings

Abstract

A method of forming a structure includes forming an alternating stack of first material layers and second material layers over a substrate; forming an etch mask material layer containing an opening over the alternating stack; performing a first anisotropic etch process that etches unmasked upper portions of the alternating stack to form a via opening below the opening in the etch mask material layer; forming a combination of a non-conformal cladding liner and a conformal sacrificial spacer layer over the etch mask material layer and in peripheral portions of the via opening; performing a punch-through process that etches a horizontally-extending portion of the conformal sacrificial spacer layer from a bottom portion of the via opening; and vertically extending the via opening by performing a second anisotropic etch process that etches unmasked lower portions of the alternating stack selective to the non-conformal cladding liner and the conformal sacrificial spacer layer.

Dependencies are inferred from the claim text.