Fabrication of Nano-Piezoelectric Thin Films for MEMS Applications

Piezoelectric thin films are an important family of functional materials in MEMS because they can provide electro- mechanical conversion directly and thus are useful for all kinds of motion sensors, actuators, transducers and acoustic devices. Most important factor for piezoelectric based MEMS devices is integration of functional piezoelectric layer onto the Si-substrate. Mainly we have two challenges, first is integration of piezoelectric functional films onto Si-substrate on wafer scale at low temperature and second is the patterning/ etching of the piezoelectric films with the resolution down to micrometer range. With an ever-expanding demand for data storage, transducers, actuators and MEMS systems applications, materials with superior ferroelectric and piezoelectric responses are of great interest. However, these film show high energy loss and low piezoelectric response compared with bulk materials, mainly due to the clamping effect of substrates and limited film thickness effect. One effective approach to resolving this problem is to fabricate nano domain thin films with a preferential crystallographic orientation that results in large piezoelectric deformation.

Highly textured nano-piezoelectric thin films were fabricated for MEMS application. The PZT films were characterized for micro-structural and electrical properties. We observed the piezoresponse in the range of 60 pm/V in PZT films. We propose to use these films for piezoelectric energy sourcing devices. It has been reported that common environmental vibrations such as those found in a building exhibit moderate amplitudes (<1g), and lower frequencies, typically between 60 Hz - 200 Hz, and fabrication of piezo thin film based micro-cantilevers vibrating at these frequencies might fulfill the requirements for a continuous power source of ~ 10 μW for a typical MEMS chip.