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Monolithic Ultrasound Array

IP.com Disclosure Number: IPCOM000089475D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Katyl, RH: AUTHOR

Abstract

Most ultrasonic transducer arrays are formed from discrete elements in a hybrid-type structure, but such construction is expensive and generally lacks the resolution necessary for many applications. It has been found that an ultrasonic transducer array can be fabricated on a silicon wafer with many more elements than are available currently. There are two key elements to such a transducer array: silicon membrane structure and piezoelectric zinc-oxide film.

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Monolithic Ultrasound Array

Most ultrasonic transducer arrays are formed from discrete elements in a hybrid-type structure, but such construction is expensive and generally lacks the resolution necessary for many applications. It has been found that an ultrasonic transducer array can be fabricated on a silicon wafer with many more elements than are available currently. There are two key elements to such a transducer array: silicon membrane structure and piezoelectric zinc-oxide film.

A cross section of a transducer cell is shown in Fig. 1. The silicon wafer is etched so that a number of cells are formed, each cell consisting of an etched pit covered on one side by a thin silicon membrane which is perhaps two microns thick. The membrane is much more flexible than the silicon wafer, being analogous to a deflectable loudspeaker cone. When it is driven normal to the wafer, it excites ultrasonic waves. (In practice a coupling fluid may be used adjacent to the silicon.)

The exciting structure is the thin-film zinc-oxide layer. The metal electrode structure which overlays the zinc-oxide film couples the electric drive potential to the mechanical disturbance. Such a structure could be used for transmitting or receiving ultrasound because of the reciprocity of the piezoelectric effect.

The completed transducer would consist of a packaged silicon chip which contains the silicon membrane transducer cells and drive and control electronics. An illustration of the package is shown in Fig. 2. The chip is mounted over an opening in a support plate. The lower portion of the package is filled wit...