Dry etching of SrBi2Ta2O9 thin films in Cl2/NF3/O2/Ar inductively coupled plasmas

Abstract

A parametric study of high density plasma etching of SrBi2Ta2O9 (SBT) thin films was carried out in a planar type inductively coupled plasma (ICP) etcher with different chemistries of Cl2/Ar, Cl2/NF3/Ar, and Cl2/NF3/O2/Ar. The etch rate was a strong function of gas concentration, ICP source power, and rf chuck power. Both Cl2/NF3/Ar and Cl2/NF3/O2/Ar plasmas showed maximum etch rates of ∼1600 Å/min at 5 mTorr, 700 W ICP power, and 150 W rf chuck power. The addition of NF3 and O2 into the Cl2/Ar mixture played an important role in not only enhancing the etch rate, but also smoothing the etched surface by reducing the kinetic energy of ions. Electrical properties of the SBT films were quite dependent of plasma chemistries: Cl2/NF3/O2/Ar showed the least damage in the films and resulted in overall the best polarization-electric field hysteresis loop compared to other chemistries.