Removal of the Polymer Formed at Via Hole with Via Etching Stopped on an Al layer Structure

概要

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We examined and analyzed the removal characteristics of polymer layers which were formed during the reactive ion etching (RIE) of via holes with via etching stopped on an Al layer (VESA) structure under various ashing and stripping conditions. Double metalorganic polymer layers, with and without F, were formed at the bottom of the via hole while only a homogeneous single metalorganic polymer layer with F was observed at the sidewall. The photoresist layer was almost completely removed by oxygen-based plasma ashing, while the metalorganic polymer layers containing F formed during RIE process remained. Nonuniform metal gap filling due to the residual sidewall polymer caused increased resistance due to the formation of voids at via metal lines. An additional wet stripping process was required to completely remove the sidewall polymer and to realize uniform metal gap filling. Wet stripping efficiency increased as the ashing temperature was lowered. A non-hydroxylamine (non-HA) based stripper removed the RIE-induced polymer more effectively than a HA based stripper regardless of the photoresist used. This study reveals that it is necessary to reduce the hardening of the polymer layer by lowering the ashing temperatures and to use a non-HA based stripper to realize reliable metal gap filling at via holes.
2003-03-15