THE DESIGN AND CHARACTERIZATION OF MICROMACHINED AIR-COUPLED CAPACITANCE TRANSDUCERS

Air coupled capacitance transducers have been manufactured using aniso tropically etched silicon backplates and commercially available dielec tric films (Kapton and Mylar). The small backplate pits which result f rom etching, provide well ordered and highly uniform air layers betwee n the backplate surface and thin dielectric film. Such uniformity allo ws the transducers to be manufactured with reproducible characteristic s (a property difficult to achieve through conventional manufacturing. Impulse response studies in generation and detection, have indicated well-damped, wideband behavior, with bandwidths extending from <100 kH z to 2.3 MHz (at the -6 dB points). These bandwidths are investigated as a function of excitation pulse width, applied bias potential, and d ielectric him thickness. An estimate of detection sensitivity is also provided by comparison with a calibrated laser interferometer.