Structural Effects on a Submicron Trench Process

Abstract

Recently, silicon trenches have been widely used for device isolation or three‐dimensional capacitors in dynamic memories. In this work, trenches with submicron openings have been fabricated and several structure‐dependent effects were discovered. A reactive ion etching rate in the vertical direction inside a trench decreases significantly as the aspect ratio (depth/width) becomes larger. A bottle‐shaped profile due to undercutting starts to appear with trenches whose openings are smaller than a micrometer and becomes worse as the width decreases. A film thickness on sidewalls for refilling trenches shows no strong dependence on the structural aspect when chemically vapor deposited at low pressure.