Deep reactive ion etching of Pyrex glass using SF₆ plasma

Deep reactive ion etching of Pyrex glass has been characterized in sulfur hexafluoride plasma (SF₆). High etch rate (approx. 0.6 μm/min) was demonstrated under a condition of low pressure (0.2 Pa) and high self-bias (-390 V) by using a magnetically enhanced inductively coupled plasma reactive ion etching. Vertical etch profile (taper angle approx. 88°), high aspect ratio (> 10) and through-wafer etching of Pyrex glass (200 μm in thickness) were achieved under the condition by using thick (20 μm) and vertical electroplated nickel film as mask. The vertical etch profile was achieved when the mask opening is narrower than 20 μm because the deposition of nonvolatile product on the sidewall is reduced. A novel etching technique 'scoop-out etching' was demonstrated by using the present etching characteristics.