Study on mechanical characteristics of PZT thin film for sensors and actuators

摘要

Abstract: Piezoelectric thin films are very promising materials for MEMS applications because they have application flexibility and compatibility with semiconductor and micromachining processes. How to design MEMS devices with piezoelectric thin films, the mechanical characteristics, and how those characteristics can be controlled by process conditions is discussed in this paper. In addition, piezoelectric/electric characteristics must be understood. With this background, mechanical characteristics (Young's modulus and built-in stress) measurements of sputtered Pb(Zrx, Ti1 $MIN x) O$-3$/ thin film, one of piezoelectric materials, have been carried out using the load-deflection method. Relationships between post anneal conditions and those characteristics are discussed. It was shown from the experiment results that Young's modulus increases as anneal temperature/time increases. The maximum value was 76.6 GPa(700 degrees C/3600 sec) which is more than three times larger than that of as-depo film. Built-in stress is also affected by post anneal process and ranges from 0.04 GPa(as-depo) to 0.41 GPa(700 degrees C/60 sec). SEM observation results made it clear that it was caused by film shrinkage due to grain enlargement during anneal process. !6