The Effects of the Addition of CF4, Cl2, and N2 TO O2 ECR Plasma on the ETCH Rate, Selectivity and Etched Profile of RuO2 Film

ABSTRACTIn this study, we investigated the effects of the addition of CF4, Cl2, and N2 gases to oxygen electron cyclotron resonance (ECR) plasma on the reactive ion etching (RIE) properties of RuO2 film such as etch rate, selectivity, and etched profile. The concentration of the etching species in the plasma was analyzed with an optical emission spectroscopy (OES) and a quadrupole mass spectrometer (QMS). The etch product was also examined with QMS.The addition of a small amount of CF4, Cl2, or N2 to the O2 plasma increases the concentration of oxygen radicals and accordingly increases the etch rate of the RUO2 films appreciably. The etch rate of the RuO2 film was enhanced more with the addition of a small amount of CF4 and CI2 than with the addition of N2. On the contrary, the etched profile obtained in O2/N2 plasma was superior, without any damaged layer at the sidewall, to O2/CF4 and O2/Cl2 plasma. The selectivity of RuO2 to Si)2 mask was over 20:1 for each of the additive gas proportion at which the etch rate was maximum for each plasma system.