Factors affecting profile evolution in plasma etching of SiO2 - Modeling and experimental verification

We present a complete modeling methodology applied to the simulation of the dry-etching process of SiO2 substrates. We formulated and implemented in a profile evolution solver a surface model for the erosion of SiO2 as consequence of the exposure to fluorocarbon plasmas. The model takes into account the concurrent ion-enhanced chemical etching of the adsorbed film and the deposition of an inhibitor film. Expressions for ion, neutral, and polymer fluxes and for the erosion yields are evaluated as global variables with respect to the profile itself. Therefore, the etch rate is calculated consistently at each profile point P and it is used as speed law F(P) in the profile solver algorithm. The model features are discussed in detail considering the effects of the variations of the physical and geometrical conditions on the overall profile evolution. The simulation results are compared with experimental etching processes we performed using a dual-frequency diode reactor etcher. In order to make our code a useful tool for the etching process development, the model parameters are related to the real machine parameters. Comparisons between simulations and scanning electron microscopy analysis of the etched profiles demonstrate the reliability of the approach.