CHF³ Dual-Frequency Capacitively Coupled Plasma by Optical Emission Spectroscopy

We investigate the intermediate gas phase in the CHF₃ 13.56MHz/2MHz dual-frequency capacitively couple plasma (CCP) for the SiCOH low dielectric constant (low-k) film etching, and the effect of 2MHz power on radicals concentration. The major dissociation reactions of CHF₃ in 13.56MHz CCP are the low dissociation bond energy reactions, which lead to the low F and high CF₂ concentrations. The addition of 2MHz power can raise the probability of high dissociation bond energy reactions and lead to the increase of F concentration while keeping the CF₂ concentration almost a constant, which is of advantage to the SiCOH low-k films etching. The radical spatial uniformity is dependent on the power coupling of two sources. The increase of 2MHz power leads to a poor uniformity, however, the uniformity can be improved by increasing 13.56MHz power.