Patent Number: 6,295,247

Title: Micromachined rayleigh, lamb, and bulk wave capacitive ultrasonictransducers

Abstract: A micromachined capacitive ultrasonic transducer is used to generate anddetect Rayleigh, Lamb, and bulk waves in a solid substrate. The transducercontains a substrate with a conductive back electrode, a support materialon the substrate, a membrane supported above the substrate by the supportmaterial, and a conductive film on the membrane. The support materialcontains parallel edges defining elongated gaps over which the membrane issupported. Unsupported free regions of the membrane above the gaps arevibrated by applying an electrical signal between the conductive film andconductive back electrode, and stresses are coupled into the substrate atthe attachment edges of the membrane. Acoustic modes of the substrate areexcited by the stresses, and ultrasonic waves propagate in a directionperpendicular to the parallel edges. By properly choosing the membranewidth, material, and thickness, the gap separation distance, and thesupport material height and thickness, a particular acoustic mode can beselected for a required operating frequency. The gaps may be separated bya distance equal to the wavelength or half-wavelength of the desiredacoustic mode. Alternately, the gaps may be grouped, with each groupseparated by a wavelength or half-wavelength. The transducer can be usedin many applications, including filtering and chemical sensing.

Inventors: Khuri-Yakub; B. T. (Palo Alto, CA), Degertekin; F. Levent (Millbrae, CA)


International Classification:

Expiration Date: 09/25/2013