A CMOS-compatible piezoelectric vibration energy scavenger based on the integration of bulk PZT films on silicon

This paper presents the micro-fabrication and testing of a CMOS-compatible high-performance piezoelectric inertial power generator. This is believed to be the first wafer-level micro-scale generator integrating a bulk piezoelectric ceramic, PZT. The technology offers advantages in fabrication flexibility and device performance over existing piezoelectric thin film deposition methods. The process involves aligned solder-bonding and thinning of bulk PZT pieces on Si. By conserving the bulk piezoelectric properties of the PZT material, high generator output voltage and high output impedance are obtained, simplifying rectification and regulation. Additional benefits of this process include the capability to obtain thick (5μm to 100μm) piezoelectric films without chemical patterning. Here, we describe a harvester with a Si proof mass, which generates 0.15μW from an input acceleration of 0.1g at 263Hz, and 10.2μW from an input acceleration of 2g at 252Hz. The unpackaged active volume of the generator (beam + mass) is 12.1mm³. The fabricated device has the highest Normalized Power Density for a PZT-based MEMS harvester reported to date, to the authors´ knowledge.