Etching properties of SrBi2Ta2O9 thin films using CF4/Ar magnetically enhanced inductively coupled plasmas for FRAM

Abstract

Using a magnetically enhanced inductively coupled plasma (MEICP) system, we etched SrBi2Ta9O9 (SBT) thin films by varying the etch parameters, such as the gas mixing ratio, the rf power: the de bias voltage, and the chamber pressure. The maximum etch rate of the SET thin films was 1850 Angstrom /min at a gas mixing ratio of CF4(10)/Ar(90). 600 W, -350 V and 10 mTorr. The selectivities of SET over photoresist and SiO2 were about 0.95 and 0.6, respectively. The etch rate decreased with increasing CF4 gas mixing ratio in CF4/Ar plasmas, but the etch rate increased with increasing de bias voltage. The chemical reactions on the etched surfaces of SET films were investigated by using X-ray photoelectron spectroscopy and secondary ion mass spectrometry.