This work presents the fabrication process of anodically bonded 192+192 2D row-column addressed (RCA) capacitive micromachined ultrasonic transducer (CMUT) arrays. Four large 2.1 by 2.1 cm2 arrays with a resonance frequency of 7.5 MHz in water and ⋋/2 element pitch at 95 µm are shown successfully fabricated. The arrays exhibit a 100% bond yield by anodically bonding an SOI wafer to a borosilicate glass wafer structured with CMUT cavities. A silicon nitride layer has been used at the wafer bonding interface to insulate the top and bottom electrodes for high voltage operation to at least ±200V DC bias. Electrical measurements have been performed on 192+192 RCA arrays and smaller 16+16 RCA arrays. These showed a resonance frequency of approximately 18 MHz in air at a bias of -200 V, corresponding to 80% of the pull-in voltage and 50 mV AC, with a coupling coefficient of 26.8 %.
|Title of host publication||2020 IEEE International Ultrasonics Symposium (IUS)|
|Number of pages||4|
|Publication status||Published - 2020|
|Event||2020 IEEE International Ultrasonics Symposium - Virtual symposium, Las Vegas, United States|
Duration: 6 Sep 2020 → 11 Sep 2020
|Conference||2020 IEEE International Ultrasonics Symposium|
|Period||06/09/2020 → 11/09/2020|