Intrinsic and Passivation-Induced Trench Tapering during Plasma Etching

Sidewall tapering is often observed during plasma trench etching. In this paper, two types of trench tapering, intrinsic tapering and passivation-induced tapering, are discussed based on numerical simulations and theory of surface evolution. Intrinsic tapering occurs when the etch rate C(0) decreases rapidly as the slope angle 0 approaches that of the vertical surface (i.e., 0 = ± π/2). It is the dominant mechanism for the formation of tapered sidewalls when the sticking coefficient &is small. For a larger sticking coefficient, passivation-induced tapering becomes more dominant. Quantitative relations between etched trench profiles and some system parameters such as sticking coefficients, etch rates, and re-emission distributions are also presented. © 1994, The Electrochemical Society, Inc. All rights reserved.