A novel low-cost fabrication process for bulk-mode resonators in X-ray LIGA technology

This paper presents design and fabrication process of a bulk-mode ring resonator in x-ray LIGA technology. The fabrication process is used to achieve a high aspect ratio of 25 with 3-4 μm gap spacing. Rigid graphite serves as a low-cost primary substrate and plating base of nickel as structural material. Moreover, low-cost x-ray mask is developed based on silver electroplating procedure. Through the combination of x-ray and UV lithographies, the fabrication process needs only three lithography steps with one x-ray mask and two Mylar masks. The resonant behavior of the fabricated resonator is characterized as a function of the bias voltage using a fully differential drive and sense interface circuit. The results show that, the quality factor of the fabricated resonator in the extensional wine-glass resonant mode is about 156170 using a DC-bias voltage of 90 V at a resonance frequency of 9.37 MHz and vacuum pressure of 0.10 mbar.