Lamb wave devices using capacitive micromachined ultrasonic transducers

Lamb wave devices based on capacitive micromachined ultrasonic transducers (CMUTs) have been built on 500-mum-thick silicon wafers for frequencies in the vicinity of 1 MHz. CMUTs have been used to both excite and detect Lamb waves in the substrate. This configuration eliminates the need for piezoele ctric materials, which are not compatible with the existing integrated circ uit (IC) fabrication techniques, and allows easy integration of Lamb wave d evices and electronics on the same wafer. Finite element analysis of the de vices shows that the lowest order antisymmetric Lamb wave (A(0)) is the dom inant mode in the substrate in this frequency range. This result is also co nfirmed by demonstration experiments. (C) 2001 American Institute of Physic s.