Plasma etching characteristics of sputtered MoSi2 films

Plasma etching of sputtered MoSi2 films using CF4/O2 mixtures was studied in a barrel-type reactor. The etch rate in pure CF4 was very low (≲100 Å/min) and insensitive to applied power. The addition of a small percentage (<10%) of O2 dramatically increased the etch rate. For CF4/4% O2, and etch rate of ∼920 Å/min was measured at 100 W. A near-linear etch rate dependence on rf power was observed, indicating that the controlling factor is the generation rate of etching radicals. For CF4/8% O2, the etch rate nearly doubled and showed saturation at high rf power, indicating the increased role of the surface reaction rate. Postdeposition anneal results in a 10–20% decrease in etch rate. An etch rate selectivity of 14–22 for MoSi2 vs SiO2 and of 2–3 for doped poly-Si vs MoSi2 were measured.