ABSTRACT
Pulse-modulated plasma etching of copper masked using SIO2 films was conducted via a CH3COOH/Ar. The etch characteristics were examined under pulse-modulated plasma. As the duty ratio of pulse decreased and the frequency of pulse increased, the etch selectivity and etch profile were improved. X-ray photoelectron spectroscopy and indicated that more copper oxides (Cu2O and CuO) and Cu(CH3COO)2 were formed using pulse-modulated plasma than those formed using continuous-wave (CW) plasma. As the concentration of CH3COOH gas in pulse-modulated plasma increased, the formation of these copper compounds increased, which improved the etch profiles. Optical emission spectroscopy confirmed that the active ingredients of the plasma increased with decreasing pulse duty ratio and increasing frequency. Therefore, the optimized pulsed plasma etching of copper via a CH3COOH/Ar gas provides better etch profile than that by CW plasma etching.
ABSTRACT
Inductively coupled plasma reactive ion etching (ICPRIE) of copper thin films masked with photoresist (PR) and SiO2 thin films was performed in H2/Ar gas. As the H2 concentration increased, the etch rates of copper films significantly decreased. The etch profiles show heavy redeposition on the sidewall of the etched films in low H2 concentration but steep etch profiles without redeposition and etch by-product were obtained in high H2 concentration. The systematic variation of the etch parameter such as ICP source power, dc-bias voltage to substrate, and process pressure was carried out to characterize the copper etching in H2/Ar gas. Based on the etch characteristics of copper films, Langmuir prove analysis, and X-ray photoelectron spectroscopy, it was revealed the physical sputtering by ions and the formation of the volatile copper compound and the protection layer had great influence on achieving a good etch profile.
