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.