Acoustic simulation and characterization of capacitive micromachined ultrasonic transducers
In this thesis, simulation and characterization methods for capacitive micro machined ultrasonic transducers (CMUT) useable for application development are shown. A nonlinear simulation model for CMUT cells is implemented, which allows to find the best CMUT design by a genetic optimization procedure. For the verification of fabricated CMUTs against simulation results and specification sheets, acoustic measurement procedures for the characterization of CMUT cell designs are developed. They are based on decoupling the sound field from the individual cell characteristics to measure the send- and receive sensitivity of CMUTs. Another possibility to assess the acoustic characteristics is the electrical impedance measurement. A nonlinear analytic model for the electrical impedance of CMUT is invented and used for design evaluation. A wafer level test procedure for an end-of-line quality assurance based on electrical impedance measurements closes the loop from simulation to fabricated CMUT. The thesis finished with further ideas for improving the CMUT technology and measurement procedures.
Zugl.: Dresden, TU, Diss., 2017