Combined Experimental and Modeling Study of Spatial Effects in Plasma Etching: CF₄/O₂ Etching of Silicon

A combined experimental and modeling study of uniformity in CF4/O2 plasma etching of silicon is presented. The model includes detailed treatment of transport (including diffusion) and chemical kinetics. Experimental measurements of spatial variations in active species concentrations are made by spatially resolved actinometry; spatial variations in etch rates are also measured. The effect of flow rate and feed composition on etch rate uniformity is examined. Model predictions are in good agreement with observations. Diffusion and free radical recombination reactions play an important role in commercial size systems. The insight gained through the model is used to point out a pitfall in the interpretation of actinometry data. The applicability of the model as a design tool is demonstrated. © 1990, The Electrochemical Society, Inc. All rights reserved.