Platinum etching using a $TiO2$ hard mask in an $O2/Cl2/Ar$ plasma

The dry etch behavior of Pt films using a $TiO2$ hard mask was investigated with an $O2/Cl2/Ar$ gas chemistry in an inductively coupled plasma. The variations in etch rates and etch profiles of both the Pt films and the $TiO2$ masks were examined as a function of $Cl2$ and $O2$ concentration. It was found that the ratio of $O2$ to $Cl2$ concentration strongly influenced the etch selectivity of the Pt film relative to the $TiO2$ mask. X-ray photoelectron spectroscopy indicates that the addition of $O2$ to the gas mix causes a decrease in the $TiO2$ etch rate as a result of the oxidation of $Ti2O3$ and TiO species. It is proposed that these oxides arise via the reduction of $TiO2$ in the presence of a $Cl2/Ar$ plasma. A 1 μm $×1$ μm minimum feature size was successfully etched with this $TiO2$ mask material, yielding a sidewall of approximately 75° in slope that did not exhibit redeposition or residue.