Several consequences of Ding´s etch rate expression: ion beam etching, etch rate control and selectivity

Summary form only given. Ding et al. (1996) have argued that the etch rate of SiO/sub 2/ by fluorocarbon plasma in high density-low pressure etch tools can be described by a simple expression which contains 3 coefficients: R=AJ/sub i/E[1-C(J/sub d//J/sub e/)/sup 2/]/(1+BJ/sub i/E/J/sub e/) where J/sub i/ is the ion flux, E is the ion energy, J/sub e/ is the etching neutral flux and J/sub d/ is the flux of deposition neutrals or ions. All quantities are measured near the wafer surface. It was found the coefficients A and B had the same values in ECR, inductive and helicon tools and did not depend on the type of the tool. A similar expression has been found for Si etching with somewhat different coefficients. This result suggests that Si-SiO/sub 2/ selectivity, i.e. the relative etch rates of Si and SiO/sub 2/, can be described by simple expressions with universal local coefficients and that selectivity can also be described by tool independent expressions involving local plasma parameters. In this paper, the consequences of this description for ion beam etching, for etch rate control, for selectivity, are explored.