Etch characteristics of CoFeB magnetic thin films using high density plasma of a H2O/CH4/Ar gas mixture

• Development of H2O/CH4/Ar etch gas to etch CoFeB magnetic thin films by inductively coupled plasma reactive ion etching.
• Etch mechanism of CoFeB films in H2O/CH4/Ar gas mixture.
• High etch rate and high etch selectivity of CoFeB thin films.
• Extremely high degree of anisotropy of CoFeB films without redeposition or etch residue in etch profile.

Etch characteristics of CoFeB magnetic thin films patterned with TiN hard masks were investigated using inductively coupled plasma reactive ion etching in H2O/Ar and H2O/CH4 gas mixes. As the H2O concentration in the H2O/Ar gas increased, the etch rates of CoFeB and TiN films decreased simultaneously, while the etch selectivity increased and etch profiles improved slightly without any redeposition. The addition of CH4 to the H2O gas resulted in an increase in etch selectivity and a higher degree of anisotropy in the etch profile. X-ray photoelectron spectroscopy was performed to understand the etch mechanism in H2O/CH4 plasma. A good pattern transfer of CoFeB films masked with TiN films was successfully achieved using the H2O/CH4 gas mix.