Effects of low energy light ions on notching and charging in high-density plasma [etching]

A comparison of notching of metal etching in Cl₂-BCl ₃ and HCl plasmas was made by using a transformer coupled plasma (TCP) etcher. We found that pure HCl plasma provides both a notch-free and lower electron shading damage process with high selectivity. The neutralization of the negatively charged upper photoresist sidewalls by H⁺ ions is thought to be the reason for the reduction in electron shading damage and notching. The reduction of sidewall attack by heavy ions and the scavenging of excess Cl radicals by H radicals are also thought to be reasons for reduced notch depth in HCl plasma. It remains unclear, however, which of the three mechanisms is dominant in notch reduction in HCl plasma