Investigation of SiO Etch Characteristics by CF/Ar/O Plasmas Generated Using Inductively Coupled Plasma and Capacitively Coupled Plasma.

The etching properties of CF/Ar/O 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. When the SiO masked with ACL was etched with CF, 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 CF, tapered SiO etch profiles were observed. In the case of the ICP system, due to the higher dissociation of CF and O compared to the CCP system, the etching of SiO required a much lower ratio of O/CF (1.0) while showing a higher maximum SiO 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 etch profiles could be obtained at the optimized condition of the O/CF ratio (1.0).