Abstract
Plasma etch of silicon is utilized in forming deep trenches which are used as storage capacitors in many types of memory applications. The effects of noble gas addition to the etchant gases (which include HBr, NF 3 and O 2) on sub-0.15 μm feature size deep trench (aspect ratio >40) etch characteristics are studied. Information from simple systems is used to explain results from the multi-component system used here. Partial replacement of HBr with Ar resulted in modifications in the trench profile: sidewall passivation film thickness, trench depth and oxide mask erosion increased while selectivity decreased. Oxygen was found to be the rate limiting component for passivation layer formation; NF 3 was the controlling factor for etch rates of both silicon and oxide. Partial replacement of HBr with noble gas is useful for enhancing throughput capabilities where the process is not limited by mask thickness or selectivity. Introduction of He showed similar behavior to Ar but the etch rates of silicon and oxide were higher resulting in lower selectivity.
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