A new model for thin oxide degradation from wafer charging in plasma etching

Abstract

Plasma nonuniformity can lead to surface charging and damaging currents through thin oxides. In poly-Si etching, surface currents across the wafer prevent damage until just before endpoint when current collected in halo regions around the mask can lead to gate charging and excessive tunneling current through the oxide. During overetching, additional damage is minimal because of the small collection area. This model is supported by plasma measurements, SPICE simulations, and etching damage results.<>