Dry etching of (Ba,Sr)TiO₃ with Cl₂, SF₆, and CF₄

Abstract

The dry etch behavior of MOCVD (Ba,Sr)TiO3 (BST) films has been investigated with Cl2/SF6 and Cl2/CF4 gas mixtures. The etch response of blanket films was evaluated as a function of gas mix, self-bias voltage, and chamber pressure. Plasma deposition effects interfered with pristine etching by the Cl2/CF4 gas mixes. Etch rates for the Cl2/SF6 gas mixes exhibited a weak maxima at 10% SF6, which then dropped to a local minima at 20% SF6. The strongest etch response occurred with respect to self-bias voltage, where the etch rate exhibited a dependence that was approximately linear. Finally, at low rf powers the etch rate decreased monotonically with increasing pressure. However, at high power a weak maxima appeared at 20 mT. Overall, these power and pressure responses are consistent with physical sputtering. Therefore, it should be expected that the etch effluent of BST films will form sidewall redeposits on steeply sloped patterned structures in high dielectric constant capacitor DRAM memory applications.