Defining Conditions for the Etching of Silicon in an Inductive Coupled Plasma Reactor

Abstract

In high-density fluorinated plasma processes, the mechanisms that fundamentally limit the etching of silicon are poorly understood. In an effort to improve our understanding of limits to the performance of such systems, the etching of silicon wafers in an inductive coupled plasma reactor, using SF₆, has been studied. A systematic empirical investigation has allowed us to define many of the experimental parameters that control the etching rate.

There is little temperature dependence of etching which suggests a diffusion limited process. Systematic variation of parameters controlling the rate of etching: total pressure in the reactor, flow rate, partial pressure of reactive species and the rf power supplied to the discharge enable us to accurately define the performance of the system. Experiments, which segregate the physical and chemical components of the etching process, support the conclusion that etching is dominated by electrically neutral species. These various results are interpreted in terms of accepted models for the reactive chemistry in plasmas containing SF₆.

The MEMS industry is placing ever greater demands on etching processes, and there is a need to achieve the high degrees of anisotropy, and critical dimension control, at high etch-rates. The approach outlined allows us to develop effective strategies for evolving improved systems for the high rate plasma etching of silicon.