Characterization of the etch rate non-uniformity in a magnetically enhanced reactive ion etcher

Abstract

A constant concern in semiconductor manufacturing is plasma induced damage. A non-uniform etching plasma can induce a dc current at the wafer surface that can damage the film and therefore the device. The magnetic field in an Applied Materials magnetically enhanced reactive ion etch chamber has been enhanced to provide minimal self-bias non-uniformity. The objective of this article is to characterize the magnetic field through a comparison of experimental etch data and modeling. Both analytical and empirical modeling have been used to gain a better understanding of the particular magnetic field configuration under investigation. At low pressure the etch rate pattern correlated well with the calculated stationary magnetic field gradient. For higher pressure this model failed to predict the etch rate uniformity behavior because of contributions from other effects in the plasma. In order to characterize these effects, experiments were conducted for both stationary and rotating magnetic fields. This was done to aid process optimization with respect to the potential for damage.