Combined Experimental and Modeling Study of Spatial Effects in Plasma Etching: CF4/02 Etching of Silicon

A combined experimental nd 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 pre-dictions 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. Although plasma etching/deposition processes are now used routinely in the manufacture of integrated circuits, theoretical understanding of the physical and chemical phenomena that determine plasma behavior s still incom-plete. This is caused by the well-documented complexity of a plasma process which arises from the coupling be-tween charged-particle physics and chemistry, neutra