DRY-ETCHING OF (BA,SR)TIO3 WITH CL-2, SF6, AND CF4

The dry etch behavior of MOCVD (Ba,Sr)TiO3 (BST) films has been invest igated with Cl-2/SF6 and Cl-2/CF4 gas mixtures. The etch response of b lanket films was evaluated as a function of gas mix, self-bias voltage , and chamber pressure. Plasma deposition effects interfered with pris tine etching by the Cl-2/CF4 gas mixes. Etch rates for the Cl-2/SF6 ga s mixes exhibited a weak maxima at 10% SF6, which then dropped to a lo cal minima at 20% SF6. The strongest etch response occurred with respe ct to self-bias voltage, where the etch rate exhibited a dependence th at was approximately linear. Finally, at low rf powers the etch rate d ecreased monotonically with increasing pressure. However, at high powe r a weak maxima appeared at 20 mT. Overall, these power and pressure r esponses are consistent with physical sputtering. Therefore, it should be expected that the etch effluent of BST films will form sidewall re deposits on steeply sloped patterned structures in high dielectric con stant capacitor DRAM memory applications.