Fabrication of a true-Gaussian-shaped quartz crystal resonator

In this paper, a simple fabrication method for a Gaussian-shaped quartz crystal resonator was developed based on the surface tension of the photoresist. First, the photoresist profile on a quartz wafer was changed to a lens shape by the photoresist reflow. By changing the viscocity of the photoresist with propylene glycol monomethyl ether acetate, the photoresist profile on the quartz wafer was adjusted to create a Gaussian shape. Finally, the Gaussian-shaped QCR was fabricated by transferring the shape onto the quartz wafer using a reactive ion etching.