Theory and analysis of electrode size optimization for capacitive microfabricated ultrasonic transducers

Theoretical analysis and computer simulations of capacitive microfabricated ultrasonic transducers indicate that device performance can be optimized through judicious patterning of electrodes. The conceptual basis of the analysis is that electrostatic force should be applied only where it is most effective, such as at the center of a circular membrane. If breakdown mechanisms are ignored, an infinitesimally small electrode with an infinite bias voltage results in the optimal transducer. A more realistic design example compares the 3-dB bandwidths of a fully metalized transducer and a partially metalized transducer, each tuned with a lossless Butterworth network. It is found that the bandwidth of the optimally metalized device is twice that of the fully metalized device.

[1]  T. S. Moss,et al.  Handbook on semiconductors , 1980 .

[2]  K. Suzuki,et al.  A silicon electrostatic ultrasonic transducer , 1989, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[3]  A. S. Grove.  Physics and Technology of Semiconductor Devices , 1967 .

[4]  Piet Bergveld,et al.  Optimization of Capactive Microphone and Pressure Sensor Performance by Capacitor-electrode Shaping , 1991 .

[5]  J. Fluitman,et al.  Selective mode excitation and detection of micromachined resonators , 1992, [1992] Proceedings IEEE Micro Electro Mechanical Systems.

[6]  E. M. Jones,et al.  Microwave Filters, Impedance-Matching Networks, and Coupling Structures , 1980 .

[7]  D. Schindel,et al.  The design and characterization of micromachined air-coupled capacitance transducers , 1995, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[8]  Abdullah Atalar,et al.  Silicon micromachined ultrasonic immersion transducers , 1996 .

[9]  I. Ladabaum,et al.  The microfabrication of capacitive ultrasonic transducers , 1997, Proceedings of International Solid State Sensors and Actuators Conference (Transducers '97).

[10]  B. Khuri-Yakub,et al.  Surface micromachined capacitive ultrasonic transducers , 1998, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[11]  Michael J. Anderson,et al.  BROADBAND ELECTROSTATIC TRANSDUCERS : MODELING AND EXPERIMENTS , 1995 .

[12]  W. P. Mason.  Electromechanical transducers and wave filters , 1942 .

[13]  Dale F. Ostergaard.  Adapting available finite element heat transfer programs to solve 2-D and 3-D electrostatic field problems , 1987 .

[14]  Butrus T. Khuri-Yakub,et al.  Micromachined ultrasonic transducers: 11.4 MHz transmission in air and more , 1996 .

[15]  R. Fano.  Theoretical limitations on the broadband matching of arbitrary impedances , 1950 .

[16]  K. Sasaki,et al.  Electroacoustic model for electrostatic ultrasonic transducers with V-grooved backplates , 1995, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[17]  Christofer Hierold,et al.  Surface micromachined ultrasound transducers in CMOS technology , 1996, 1996 IEEE Ultrasonics Symposium. Proceedings.

[18]  Aaas News,et al.  Book Reviews , 1893, Buffalo Medical and Surgical Journal.

[19]  J S Heyman,et al.  Broadband electrostatic acoustic transducer for ultrasonic measurements in liquids. , 1979, The Review of scientific instruments.

[20]  C Wykes,et al.  The performance of capacitive ultrasonic transducers using v-grooved backplates , 1991 .

[21]  Pentti Mattila,et al.  Capacitive ultrasonic transducer with net backplate , 2000 .