Damage-Free Vertical Microfabrication of α-Quartz via HF Gas-Phase Catalyst Etching

Vertical microfabrication of α-quartz is typically performed via reactive-ion etching; however, ion irradiation from a plasma source etches the hard mask and disrupts the crystal structure of the etched surface. Thus, the microstructures fabricated via the conventional process have limitations in terms of the taper angle, depth, and crystallinity, which limits technological innovation in quartz devices. In this study, we introduce a plasma-free gas-phase catalyst etching for α-quartz using HF gas and a patterned photoresist as a catalyst. This method realizes vertical etching without depth limitations, regardless of the crystal orientations because the etching reaction in the catalyst contact area on the quartz is dominant over the crystal anisotropy. Therefore, high-aspect-ratio deep microstructures were fabricated on the α-quartz without forming damage layers, e.g., amorphization or chemical-state changes. Our findings may lead to inventions in material and device design using microfabricated α-quartz.