Fluorine-free high-resolution selective plasma etching of silicon-oxide layers on silicon substrates

Highly selective and vertical dry etching of SiO 2 structures on silicon substrates is reported using a mixture of C 2 H 2 and H 2 gases in a direct current plasma reactor and at elevated temperatures ranging from 420 to 620 °C. Good anisotropic etching of SiO 2 features can be achieved by this process without a need for fluorocarbon-based gases which are used to increase the selectivity of etching and to avoid the removal of the underlying silicon. The vertically etched patterns of SiO 2 have been accomplished with a high selectivity over the Si and Si 3 N 4 layers. The etch rate can be adjusted to obtain values between 2 and 20 nm min −1 depending on the temperature as well as the gas composition and plasma conditions.