Bimorph Piezoelectric Micromachined Ultrasonic Transducers

Patent Status

Brief Description

Piezoelectric Micromachined Ultrasonic Transducers (pMUTs) have attracted industry attention for their good acoustic matching, large bandwidth, miniaturization, and low cost-by-batch fabrication. pMUTs have the advantages of low power consumption and large deflection for high-acoustic power applications. However, low electromechanical coupling has been a serious drawback for pMUT applications, in some cases foreclosing key opportunities. 

In response to this challenge, researchers at UC Berkeley have developed a bimorph pMUT with unique advantages which dramatically improve the device capabilities: the bimorph pMUT utilizing two active AlN layers in a CMOS-compatible process. This innovative design is the first bimorph pMUT with two active piezoelectric layers separated by a common electrode. 

The prototype bimorph pMUT has a resonant frequency of 198.8 kHz and central displacement of 407.4 nm/V. Under the differential drive scheme using the dual electrodes at low frequency, the measured central displacement is 13.0 nm/V, which is about 400% higher than that of a unimorph AlN pMUT. This revolutionary dual electrode bimorph pMUT presents a new class of design/fabrication for exciting pMUT applications, including range finders and gesture recognition devices.

Applications

- Ultrasonic gesture recognition
- Range finding
- Finger print identification
- Medical imaging
- Energy harvesting

Advantages

- 10X improved linearity
- 400% improvement central displacement
- 4X performance enhancement