Fabrication of 150-nm-wide transducer gaps for disk-type resonators by single dry etching process

We have newly designed and fabricated single crystal silicon (SCS) disk-type micromechanical resonators with 150-nm-wide vertical transducer gaps. The transducer gaps have been fabricated through a simple process including a single trench etching of SCS by deep reactive ion etching (D-RIE) with a resist mask patterned by electron beam lithography. The peak resonant frequencies measured for the fabricated resonators agreed well with those predicted by finite element simulations. Furthermore, the D-RIE process conditions for transducer gaps have been improved. Using the improved D-RIE process conditions, less tapered gaps of 2 μm deep were successfully fabricated for 100-, 150-, and 200-nm-wide gap patterns. The sidewall angle was from 88 to 89° depending on the gap width.