Deep reactive ion etching of Pyrex glass

We have developed a deep reactive ion etching of Pyrex glass in SF₆ plasma. High etch rate (approximately 0.6 μm/min) and smooth surface (Ra to approximately 4 nm) were achieved at low pressure (0.2 Pa) and high self-bias (-390 V). This result indicates energetic ions for physical sputtering and for enhancing chemical reactions are required to etch materials which produce nonvolatile reaction products. Vertical etch profile (base angle approximately 88°), high aspect ratio (>10) and through-out etching of Pyrex glass (200 μm in thickness) were achieved when the mask opening is narrower than 20 μm. Relatively low selectivity to the mask material due to the energetic ion is overcame using thick and vertical electroplated Ni film as a mask. We also find out the base angle of the etch profile depends on the mask profile and the opening width.