Power harvesting using piezoelectric MEMS generator with interdigital electrodes

The energy harvesting from ambiance to power the tiny sensor devices by MEMS generator is becoming practical due to the power consumption of low power VLSI (very large scale integration) circuits is going down to tens to hundreds mu W for integrated wireless sensor devices. In this paper, we present the design and process development of a piezoelectric MEMS generator that has the ability to scavenge mechanical energy of ambient vibrations and transform it into electrical energy. The piezoelectric MEMS generator comprises a beam structure based on the silicon wafer with laminated PZT (lead zirconate titanate) material and interdigital electrodes on the top of the PZT layer, to transform mechanical strain energy into electrical charge using the d(33) mode of PZT. An in-house developed PZT deposition chamber which could deposit PZT thin film up to tens micron in minutes was used to deposit the piezoelectric layer on the beam structure of the piezoelectric MEMS generator. The output power performance and output voltage with varied gaps of the interdigital electrodes are evaluated and detailed in this paper.