Process for etching tapered polyimide vias

Abstract

A polyimide-oxide-polyimide integrated circuit structure is utilized in the process for forming openings having tapered sidewalls and predetermined controlled sizes. At least one opening size is replicated and transferred to an exposed surface in a underlying surface of the structure by first forming a thick layer of oxide over the first cured polyimide layer, anisotropically etching the thick layer of oxide to form an opening of predetermined size therethrough to the surface of the first cured polyimide layer. Next, the first layer of cured polyimide is isotropically etched to form an opening therethrough of substantially said predetermined size and exposing a portion of a thin layer of oxide underlying the first layer of cured polyimide. The thin layer of oxide is then anisotropically etched using the thick layer of oxide as an etch mask to expose an opening of said predetermined size on a surface of a second layer of cured polyimide. The second layer of cured polyimide is then anisotropically etched again using the thick layer of oxide as the etch mask to transfer and replicate the opening in the thick layer onto the surface of the underlying region. Thereafter the thick layer of oxide is removed. Metalization can then be deposited on the resulting structure to make contact to the underlying surface.