Comparison of plasma chemistries for dry etching of Ta2O5

Inductively coupled plasma etching of Ta2O5 was performed in a variety of different chemistries, including SF6 with additions of O2, Ar, CH4 or H2; Cl2/Ar; N2/Ar; and CH4/H2/Ar. Etch rates up to ∼1200 Å min−1 were achieved with either SF6- or Cl2-based chemistries. Under these conditions the etch rates for Si were approximately four to seven times faster, although equirate etching was achieved at low source powers and low halogen gas percentages in the plasma chemistry. The etched Ta2O5 surfaces were smooth (root mean square roughness ⩽0.5 nm) over a broad range of conditions of source power, chuck power, and process pressure. The etch rates with N2/Ar and CH4/H2/Ar were an order of magnitude lower than with SF6 or Cl2. There was no effect of postdeposition annealing on the Ta2O5 etch rates, at least up to 800 °C.