Deep reactive ion etching of borosilicate glass using an anodically bonded silicon wafer as an etching mask

A new dry-etching method for fabricating anisotropic deep grooves on a borosilicate glass wafer is reported. The method uses a 200 µm thick bulk silicon wafer bonded to a borosilicate glass wafer by anodic bonding as an etching mask and inductively coupled plasma generated by C 4 F 8 or CHF 3 gases for etching. The measured etching rate showed that the deep reactive ion etching conditions for achieving a high etching rate are low gas pressure, high gas-flow rate, high antenna power and high bias power. The measured groove profile revealed that the sidewall angles of the etched grooves were less than 80° and C 4 F 8 plasma provided a slight difference in width between the mask opening and etched groove. These results indicate that C 4 F 8 plasma is suitable for precise groove fabrication. Even after fabrication of a 430 µm deep groove, enough silicon mask (135 µm thickness) remained to fabricate a deeper groove. Consequently, our etching method using an anodically bonded silicon mask and C 4 F 8 plasma enables the fabrication of very deep grooves in borosilicate glass.