The first PMMA-based membrane tunneling accelerometers were fabricated by hot embossing replication with silicon molds. The silicon molds were prepared by a combinative etching technique involving anisotropic bulk etching and modified plasma dry etching. The constructed molds hold both pyramid pits and positive profile sidewalls with smooth surfaces and steep angles, which were necessary for the hot embossing demoiding. After electrodes patterned on embossed PMMA structures, the accelerometers, 8 mm × 8 mm × 1 mm, were packaged and assembled on a measurement circuit board. The exponential relationship between tip currents and applied deflection voltages presented a tunneling barrier height of 0.17 eV. The natural frequency of sensors was about 128 Hz. The bandwidth of the feedback system was 6.3 kHz. The sensitivity of voltage over acceleration was 20.6 V/g, and the resolution was 0.2485 μg/√Hz (g = 9.8 m/s2).
Bibliographical noteFunding Information:
Manuscript received May 24, 2004; revised January 10, 2005. This work is partially supported by grants NSF/LEQSF (2001-04)-RII-02, DARPA DAAD19-02-1-0338, and NASA (2002)-Stennis-22. The experimental work was implemented at the Institute for Micromanufacturing, Louisiana Tech University, Ruston, LA 71272 USA. Subject Editor T. Kenny.
- Electron tunneling
- Hot embossing