Infinitely High Etch Selectivity of Si_3N_4 Layer to ArF Photoresist in Dual-Frequency Superimposed Capacitively Coupled Plasmas

摘要

Etch rates of Si_3N_4 and ArF photoresist (PR) in the CH_2F_2/H_2/Ar dual-frequency superimposed capacitively coupled plasmas are controlled by the hydrofluorocarbon layers that deposit on the Si_3N_4 and PR surfaces. The thickness of the hydrofluorocarbon layers depends on CH_2F_2 and H_2 flow rates in the plasma chemistry. The differences in etching behaviors between Si_3N_4 and PR at certain H_2 flow regimes is due to the ability of Si_3N_4 layer to consume the hydrofluorocarbon layer by forming HCN and SiF_4 etch by-products while the hydrofluorocarbon layer is deposited and not consumed on the PR surface. As a result, a process window for an infinite Si_3N_4/PR etch selectivity exits at a certain process window.