Alternative Interpretation of Plasma Processing Damage Data to Facilitate Comparisons Between Oxide Etchers

Plasma processing damages devices by driving current through the thin gate oxides. During contact and via oxide etching processes, direct electrical contact between the plasma and the device junctions is made only during the overetch period when the thick oxide layer is removed. Anecdotal evidence indicates that high-plasma density oxide etchers cause more device damage than do low- or medium- density reactors. We need to understand whether the processing damage is an unavoidable consequence of the high plasma density or merely due to a relatively immature reactor design that has not yet been optimized to minimize damage. In this paper, we show alternative ways to interpret oxide etching and device damage data in ways that we hope will enable a more direct comparison of the damage caused by different oxide etchers. We estimate the bias current as the ratio of the bias power to V sub (dc). Oxide etching rates scale linearly with bias current when the process is not reactant limited.