Highly Sensitive PZT Thin Film Ultrasonic Micro-sensors with Grooved Diaphragm

Highly sensitive piezoelectric ultrasonic micro-sensors with a grooved multilayer membrane have been developed by Si-based MEMS technique. The groove was located at one-quarter of the membrane and opened in piezoelectric layer. The piezoelectric layer PZT is 2.2 mum thick and was prepared by sol-gel method. The prepared PZT films shows pure perovskite and high (100) textured strucure. The sensitivity of the fabricated piezoelectric ultrasonic sensor without the groove structure is 100 muV/Pa. On the other hand, the sensitivity of the ultrasonic sensor with the groove structure is about 500 muV/Pa, which is 5 times higher than that without the groove structure. The diaphragm having grooves shows a corrugate-like structure that was formed by residual stress. The high sensitivity of the membrane with the grooved diaphragm is considered to relate with the corrugate-like structure.