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.

[1]  Chen-Kuei Chung,et al.  High aspect ratio silicon trench fabrication by inductively coupled plasma , 2000 .

[2]  Yuichi Sakai,et al.  Improvement of sidewall roughness in deep silicon etching , 2000 .

[3]  J.R. Clark,et al.  High-Q VHF micromechanical contour-mode disk resonators , 2000, International Electron Devices Meeting 2000. Technical Digest. IEDM (Cat. No.00CH37138).

[4]  S. Pourkamali,et al.  Fully single crystal silicon resonators with deep-submicron dry-etched transducer gaps , 2004, 17th IEEE International Conference on Micro Electro Mechanical Systems. Maastricht MEMS 2004 Technical Digest.

[5]  F. Ayazi,et al.  Support loss in micromechanical disk resonators , 2005, 18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005..

[6]  Farrokh Ayazi,et al.  Vertical capacitive SiBARs , 2005, 18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005..

[7]  F. Ayazi,et al.  A high resolution, stictionless, CMOS compatible SOI accelerometer with a low noise, low power, 0.25 /spl mu/m CMOS interface , 2004, 17th IEEE International Conference on Micro Electro Mechanical Systems. Maastricht MEMS 2004 Technical Digest.

[8]  F. Ayazi,et al.  An analytical model for support loss in micromachined beam resonators with in-plane flexural vibrations , 2003 .

[9]  Patrick J. French,et al.  Advanced time-multiplexed plasma etching of high aspect ratio silicon structures , 2002 .

[10]  Farrokh Ayazi,et al.  Low-motional-impedance highly-tunable I/sup 2/ resonators for temperature-compensated reference oscillators , 2005, 18th IEEE International Conference on Micro Electro Mechanical Systems, 2005. MEMS 2005..

[11]  Ivo W. Rangelow,et al.  Dry etching with gas chopping without rippled sidewalls , 1999 .

[12]  18µM THICK HIGH FREQUENCY CAPACITIVE HARPSS RESONATORS WITH REDUCED MOTIONAL RESISTANCE , 2004 .