Supersensitive Ultrasound Probes for Medical Imaging by Piezoelectric MEMS with Complemented Transmitting and Receiving Transducers

We propose an innovative piezoelectric micromachined ultrasonic transducer (PMUT) with complemented transmitting (Tx) and receiving (Rx) elements. By separating the Tx and Rx elements, hence giving an independent degree of freedom design to the material and structure, the sensitivity and bandwidth of the transducer are significantly improved. To demonstrate this, we fabricate an element of a 10 MHz range 1D array transducer. The Tx-chip is processed to be diaphragms after depositing a 2.6 μm PZT thin film on a silicon on insulator substrate. The Rx-PMUT chip consists of a 4.6 μm P(VDF-TrFE) thin film, which is directly coated and crystalized on a complementary metal-oxide-semiconductor circuit. The Tx and Rx chips are placed side-by-side in proximity. We evaluate the single element acoustic characteristics, Tx sensitivity, Rx sensitivity, and instantaneous loop gain (ILG) in water. As a result, we realized a higher ILG of +29 dB and a wider bandwidth compared to a conventional 1D array.