Deep dry etching of fused silica using C4F8/Ar inductively coupled plasmas

Abstract

This paper reports the etching process of fused silica by inductively coupled plasmas (ICP) for through glass via (TGV) applications. Mixed C4F8 and Ar were used as etching gases in present experiments. The effects of key factors, including etching gases, chamber pressure and substrate temperatures, on etch rate and via profile were studied. Results showed that a high etch rate of about 0.75 μm/min with smooth and vertical sidewall of TGVs can be obtained. Compared to Ar flux and chamber pressure, the effect of C4F8 flux on etch rate is more remarkable. Vertical vias (>89°) can be achieved by increasing the substrate temperature and decreasing the mixing ratio of C4F8 and Ar. Besides, micro-pillars at the bottom of via were observed when the substrate temperature was set at 0 °C. As the substrate temperature reached to 80 °C, micro-pillars were removed clearly. Optimized results indicate that the ICP etching is an effective method for fabricating TGV.