Simulating the chlorine plasma etching profile of high-aspect-ratio trenches in Si

Abstract

We simulate etching trenches in Si with a high (over 15) aspect ratio, i.e., the ratio between the trench depth and width in Cl2 plasma in wide ranges of the ratio between the flows of Cl atoms and Cl+ ions (3–300) and ion energies (50–250 eV). We demonstrate that the trenches with a high aspect (HA) ratio (~20) and almost vertical walls can be formed at the maximum energies of E i = 250 eV and R = 300. At the lower values of these parameters, etching an HA-ratio trench is accompanied by its narrowing, curvature, or bending. We discuss the origin of the HA-trench bending effect at small R values and a high energy of the incident ions.