Cl2 reactive ion etching mechanisms studied by in situ determination of ion energy and ion flux

Abstract

An experimental study of etching mechanisms in Cl2 reactive ion etching is reported. The ion-impact energy distribution and ion current density have been measured in situ at the rf electrode of a parallel-plate reactive ion etcher. This diagnostic method has been used for the first time to unravel etch characteristics in a practical etching environment. Samples of Si, SiO2, Ti, and TiSi2 have been etched both in Cl2 and Ar discharges, and the etch rates have been related to the ion flux and impact energy distribution. The angular impact energy distribution for both ions and neutrals has been calculated numerically in order to study the contribution of fast neutrals and the angular distribution of impinging species to the etch rate. Sputter yields have been determined from the observed etch rate and the ion current density, taking into account the (angular) energy distributions of bombarding ions and neutrals. Comparison of the obtained sputter yields in Ar and Cl2 discharges with corresponding data from (chemically assisted) ion-beam sputtering gives further insight into the etching mechanisms of Si, SiO2, Ti, and TiSi2.