Dry-etching of barium-strontium-titanate thin films

Reactive Ion Etching of Ba_0.7Sr_0.3TiO₃ (BST)-thin films was studied by using a Lam TCP^TM 9400 high density, low pressure plasma reactor. The BST films were prepared by chemical solution deposition and masked using patterned photoresist. Several parameters of the etch process were varied including: etch chemistry, total pressure, coil power, bottom power, and gas flow. Etch results were characterized using scanning electron microscopy with respect to etch rate, selectivity to photoresist mask and SiO₂, etch profile, sidewall redepositions (fence), and residues of etch products. Chlorine chemistry, high coil power and a low total pressure were needed in order to effectively suppress the forming of fences and residues. An etch process was established with an etch rate of 70 nm/min and a profile slope of about 80