Deep reactive ion etching of pyrex glass using a bonded silicon wafer as an etching mask

A new dry-etching method for fabricating an anisotropic deep groove in Pyrex^® glass is described. In the method, a 200-μm-thick silicon wafer bonded to a Pyrex glass wafer by anodic bonding is used as an etching mask. Inductively coupled plasma generated by C₄F₈ and CHF₃ gases is also used. The measured etching rate showed that the necessary deep reactive ion etching conditions for a high etching rate are low gas pressure, high gas flow rate, high antenna power, and high bias power. The measured groove profile also showed that the sidewall angle of an etched groove is 80 degrees, which is slightly inclined off the vertical sidewall, and a fractional difference in width between the mask opening and etched groove can be found when C₄F₈ plasma is used. C₄F₈ plasma is therefore more suitable for precise groove fabrication. Even with a 430-μm-deep groove, a 135-μm-thick silicon mask still remained enough to fabricate a deeper groove. Consequently, our etching method using a bonded silicon mask and C₄F₈ plasma enables fabricating a deeper Pyrex glass groove.