Investigation of SiO 2 Etch Characteristics by C 6 F 6 /Ar/O 2 Plasmas Generated Using Inductively Coupled Plasma and Capacitively Coupled Plasma.

The etching properties of C 6 F 6 /Ar/O 2 in both an inductively coupled plasma (ICP) system and a capacitively coupled plasma (CCP) system were evaluated to investigate the effects of high C/F ratio of perfluorocarbon (PFC) gas on the etch characteristics of SiO 2 . When the SiO 2 masked with ACL was etched with C 6 F 6 , for the CCP system, even though the etch selectivity was very high (20 ~ infinite), due to the heavy-ion bombardment possibly caused by the less dissociated high-mass ions from C 6 F 6 , tapered SiO 2 etch profiles were observed. In the case of the ICP system, due to the higher dissociation of C 6 F 6 and O 2 compared to the CCP system, the etching of SiO 2 required a much lower ratio of O 2 /C 6 F 6 (~1.0) while showing a higher maximum SiO 2 etch rate (~400 nm/min) and a lower etch selectivity (~6.5) compared with the CCP system. For the ICP etching, even though the etch selectivity was much lower than that by the CCP etching, due to less heavy-mass-ion bombardment in addition to an adequate fluorocarbon layer formation on the substrate caused by heavily dissociated species, highly anisotropic SiO 2 etch profiles could be obtained at the optimized condition of the O 2 /C 6 F 6 ratio (~1.0).