Operation Parameters of Inductively Coupled C₄F₆/SF₆ Plasma Etching Process for Si Substrate Material

To avoid the scallop effect caused by Bosch etching process and reduce GWPs carried by etching gas, an environmentally friendly electronic etching gas, C₄F₆, is introduced into the etching process. The Si substrate was etched by using a pseudo-Bosch process with simultaneous etching and passivation. And the effects of ICP power, RIE power, cavity pressure and flow rate of C₄F₆/SF₆ on etching rate, photoresist/Si etch selection ratio and etch morphology were investigated. The results show that increasing ICP power and RIE power can improve the plasma density and physical bombardment effect, respectively; the chamber pressure has a large impact on the mean free diameter of particles, and the increase of C₄F₆ flux could strengthen the sidewall protection mechanism. Under the optimized etching condition, flat sidewalls, smooth surface, and high perpendicularity etching profile with 2.8 μm/min silicon etching rate and 3.1 photoresist/Si etching selection ratio can be obtained.