An ultra-high element density pMUT array with low crosstalk for 3-D medical imaging

Area of Science:

• Micro-electromechanical systems (MEMS)
• Ultrasonic transducer technology
• Materials science

Background:

• Traditional ultrasonic transducer arrays face limitations in element density and crosstalk.
• Achieving high-performance piezoelectric micromachined ultrasonic transducer (pMUT) arrays is crucial for advanced imaging.
• Existing fabrication methods often struggle with integrating dense arrays and maintaining performance.

Purpose of the Study:

• To propose and demonstrate a novel piezoelectric micromachined ultrasonic transducer (pMUT) array with ultra-high element density.
• To achieve low crosstalk and high performance in a compact pMUT array design.
• To explore the potential for integrated circuit (IC) compatibility and 3-D medical imaging applications.

Main Methods:

• Development of a nano-layer spin-coating lead zirconium titanium film technique for piezoelectric layer deposition.
• Implementation of low-stress Silicon-on-Insulator (Si-SOI) bonding and bulk silicon removal processes.
• Fabrication of fine-pitch 6 × 6 pMUT arrays with a minimum interspace of approximately 20 μm.

Main Results:

• Successful fabrication of a novel pMUT array with ultra-high element density and minimal interspace (~20 μm).
• Demonstrated uniform operation at the target frequency (~1 MHz) with high performance.
• Achieved low crosstalk, a critical factor for advanced ultrasonic applications.

Conclusions:

• The developed nano-layer spin-coating technique and fabrication processes enable high-density pMUT arrays.
• The novel pMUT arrays exhibit excellent performance, uniformity, and potential for IC integration.
• These arrays hold significant promise for ultrasound beam steering and high-quality 3-D medical imaging.