Deep Structures Wet Etched Into Lithium Niobate Using A Physical Mask

The present work is an investigation and characterization of a new technique for etching and masking lithium niobate (LiNbO3) to realize high aspect ratio structures. LiNbO3 is a single crystal, optically clear (from 350 nanometer to 5 micrometer wavelength) piezoelectric and electro-optical material. It is inert to most reactants and has a high Curie temperature. These properties allow LiNbO3 to be used as a sensor or actuator in harsh environments or as an optical modulator. Multi-level lithium niobate deep etching techniques are currently unavailable or limited. The present work uses a chrome gold mask with a solution of hydrofluoric acid and nitric acid at 80 °C to etch the LiNbO3. The novel wet etch method developed yields an etch rate of 30 micrometer per hour on the -z face and less than 250 nm per hour on the +z face. In the experimentation done with this research trenches 80 micrometers deep were fabricated. Experimental etch and results are detailed.