High density plasma reactive ion etching of Ru thin films using non-corrosive gas mixture

• Etching of Ru films in CH3OH/Ar was investigated.
• High selectivity and etch profile with high degree of anisotropy were obtained.
• XPS analysis was examined to identify the etch chemistry.
• During etching Ru was oxidized to RuO2 and RuO3 can be easily sputtered off.

Inductively coupled plasma reactive ion etching (ICPRIE) of Ru thin films patterned with TiN hard masks was investigated using a CH3OH/Ar gas mixture. As the CH3OH concentration in CH3OH/Ar increased, the etch rates of Ru thin films and TiN hard masks decreased. However, the etch selectivity of Ru films on TiN hard masks increased and the etch slope of Ru film improved at 25% CH3OH/Ar. With increasing ICP radiofrequency power and direct current bias voltage and decreasing process pressure, the etch rates of Ru films increased, and the etch profiles were enhanced without redeposition on the sidewall. Optical emission spectroscopy and X-ray photoelectron spectroscopy were employed to analyze the plasma and surface chemistry. Based on these results, Ru thin films were oxidized to RuO2 and RuO3 compounds that were removed by sputtering of ions and the etching of Ru thin films followed a physical sputtering with the assistance of chemical reaction.