Piezeoelectric micromachined ultrasound tranducer array for photoacoustic imaging

A piezoelectric micromachined ultrasonic transducer (pMUT) array designed for photoacoustic imaging is presented in this paper. Two-dimensional pMUT arrays containing 144 elements (12×12 array) were bulk micromachined in silicon substrate. The devices were formed using two backside masks with deep reactive ion etching to create PZT thin film membranes and suspended silicon beams. The membrane radius is 25μm, with an 80μm element pitch. The total area for the pMUT array is approximately 1.6×1.6mm². This membrane consists of 0.6μm PZT layer, 1μm elastic layer (SiO₂) and 5μm supporting layer. Impedence and vibration measurements shows the resonant frequency of the pMUT elements is around 10MHz. Acoustic signal is detected using Pulse-Echo method. This high density acoustic sensor array has high array spatial gain and wide reception angle that can be used in photoacoustic imaging systems.