Ultrahigh-speed etching of SiO2 with ultrahigh selectivity over Si in microwave-excited non equilibrium atmospheric pressure plasma

Etching of a SiO2 film [Boro-phospho silicate glass (BPSG)] has been performed in a continuous-wave microwave-excited nonequilibrium atmospheric pressure plasma using a microgap discharge. A NF3∕He gas mixture with added H2O was employed as the feed gas. An ultrahigh etch rate for SiO2 (BPSG) of 14μm∕min and an ultrahigh selectivity over Si(SiO2∕Si) of 200 was obtained. A mechanism for the selective etching is proposed based on results obtained using Fourier transform infrared spectroscopy and spatially imaged optical emission spectroscopy with an intensified charge-coupled device camera. This process could offer a breakthrough for ultrahigh-speed, damage-free micromachining of SiO2 in microelectromechanical system devices.