Multielement Ring Array Based on Minute Size PMUTs for High Acoustic Pressure and Tunable Focus Depth.

Area of Science:

• Micro-ultrasound transducer technology
• CMOS-integrated MEMS devices
• High-frequency acoustic imaging

Background:

• Traditional ultrasound transducers face limitations in miniaturization and resolution.
• Piezoelectric micro-machined ultrasonic transducers (PMUTs) offer potential for high-frequency applications.
• Integration of PMUTs with CMOS technology enables compact and sophisticated ultrasound systems.

Purpose of the Study:

• To develop and characterize a multielement annular ring ultrasound transducer using PMUTs on CMOS.
• To achieve high-precision axial focalization and high-performance ultrasound imaging.
• To demonstrate the feasibility of PMUT-on-CMOS for advanced ultrasound applications.

Main Methods:

• Fabrication of a five-independent-ring PMUT-on-CMOS annular array using a monolithic process.
• Characterization of transducer performance including crosstalk, beam focusing, and output pressure in liquid.
• Pulse-echo experiments utilizing the central ring as a receiver for high-resolution imaging demonstration.

Main Results:

• The PMUT-on-CMOS array exhibits low crosstalk (<56 dB) and efficient beam focusing (1.4 mm to 67 µm).
• Achieved a record output pressure of 4.84 kPa/V/mm² in liquid for PMUTs.
• Demonstrated high receiving sensitivity (441.6 nV/Pa) with the central ring, surpassing commercial hydrophones.
• Successfully generated a 1D ultrasound image, confirming imaging capabilities.

Conclusions:

• The developed PMUT-on-CMOS annular array represents a significant advancement in miniaturized ultrasound transducer technology.
• The device's performance metrics, including output pressure and sensitivity, are state-of-the-art for PMUTs.
• This technology holds great promise for next-generation high-resolution ultrasound imaging systems.