Single-mask reduced-gap capacitive micromachined devices

This paper presents single mask capacitive micromechanical devices with dry-etched deep-sub-micron gaps. Thick oxide mask layer with sub-micron openings suitable for etching deep narrow trenches is fabricated using a gap-reduction technique. Less than 100nm openings are realized while the original feature sizes are defined by conventional optical lithography. This method combined with modified high aspect ratio DRIE recipes shows a great potential for batch-fabrication of high-frequency low-impedance single crystal silicon resonators on SOI substrates. Results measured from various resonator structures with frequencies as high as 205 MHz, Q values as high as 68,000, and 200nm gaps with aspect ratio of 60:1 are demonstrated.