Backing material for micromachined ultrasonic transducer devices

Abstract

An ultrasonic transducer device comprising: an ultrasonic transducer array micromachined on a substrate; flexible electrical connections connected to the transducer array; and a body of acoustically attenuative material that supports the substrate and the flexible electrical connections. The acoustic backing material may contain additional features, such as tabs or notches, for use in positioning the transducer on fixtures during manufacturing or positioning the transducer within a housing during final assembly. Tabs or other features that are used only during manufacturing may be subsequently removed from the device. The MUT device itself may also be thinned so as to provide flexibility as desired. The backing material is preferably matched in acoustic impedance to the silicon wafer so as to prevent reflection at the interface of any acoustic energy propagating rearward, i.e., in the direction away from the device front surface. The backing material may also possess a high thermal conductivity to assist in removal of heat from the device.

Description

BACKGROUND OF THE INVENTION This invention generally relates to micromachined ultrasonic transducers. In particular, the invention relates to capacitive micromachined ultrasonic transducers (cMUTs). One specific application for cMUTs is in medical diagnostic ultrasound imaging systems. Conventional ultrasound imaging transducers generate acoustic energy via a piezoelectric effect in which electrical energy is converted into acoustic energy using a poled piezoelectric ceramic material. The acoustic energy that is transmitted in the forward direction, which is in the direction of the patient being scanned, is coupled to the patient through one or more acoustic matching layers. However, the acoustic energy transmitted in the direction away from the patient being scanned is typically absorbed in and / or scattered in an acoustic backing material located on the backside of the transducer array. This prevents the acoustic energy from being reflected from structures or interfaces behind th...

AI Technical Summary

Problems solved by technology

However, the acoustic energy transmitted in the direction away from the patient being scanned is typically absorbed in and / or scattered in an acoustic backing material located on the backside of the transducer array.

This prevents the acoustic energy from being reflected from structures or interfaces behind the transducer and back into the piezoelectric material, thereby reducing the quality of the acoustic image obtained from reflection within the patient.

However, PZT transducers require ceramic manufacturing processes that are different from the processing technologies used to manufacture other parts of an ultrasound system, such as semiconductor components.

A MUT device manufactured on a silicon wafer is fragile and requires great care during the manufacturing process to not become damaged.

Unevenly applied pressure can lead to fracture of the device.

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