Effects of Etching Gases and Bias Frequency on Notching and Charging in High-Density Plasma

Abstract

Effects of etching gas chemistry and bias frequency on notching and electron shading damage in metal etching were investigated by using high-density plasma etching tools. It was found that employing HCl-containing plasma in the overetching process and/or lowering the bias frequency could reduce notching and electron shading damage. The results of optical emission spectroscopy and the electron shading damage evaluation suggest that low-energy H+ ions play an important role. The ion energy distribution function is bimodal at low bias frequency or high plasma density, and the minimum ion energy decreases as both the bias frequency and the ion mass decrease. Therefore, the decrease in the ion energy at the electrode contributes to the reduction of electron shading damage and notching. The neutralization of the negatively charged photoresist sidewalls by low-energy light ions is considered to be the reason for the reduction in electron shading damage and notching.