A pre-charged CMUT structure with a built-in charge storage capacitor

Pre-charging can eliminate the need for a DC bias in capacitive micromachined ultrasonic transducers (CMUTs) and enable energy transfer to implantables. Charging by Fowler-Nordheim (FN) tunneling through an oxide layer is challenging and requires a high electric field. We designed a pre-charged CMUT structure with a built-in charge storage capacitor. In this novel design, a floating electrode is formed between the top and bottom electrodes. Charge writing is achieved by directly contacting the floating electrode to the bottom electrode. The initial results show that the proposed structure can store electrical charges without leakage and it allows operation without a DC bias.