Chemical solution modified PZT thick films using hybrid deposition techniques for piezoelectric MEMS devices

There is a strong interest in introducing PZT films for applications in microelectromechanical systems (MEMS) since they have large piezoelectric coefficients and electromechanical coupling coefficients. However, stress induced in PZT thin films due to clamping of the films by the substrates and other degradation parameters such as low breakdown strength, reduced extrinsic domain wall contribution and insufficient poling have limited these thin films to be used in some MEMS applications. To develop PZT films for MEMS devices with high displacement, it is necessary to fabricate high quality PZT thick films over 10 micrometer. Some deposition techniques such as screen printing and hydrothermal depositions have been used for preparing PZT thick films, but in general PZT thick films by these methods have showed insufficient film quality for MEMS devices due to porous or low film density, poor surface morphology and bad electrical properties. To solve these drawbacks, we have performed an extensive experiment for optimized chemical solution modified hybrid deposition techniques. Based on the experimental results of the piezoelectric and dielectric properties of PZT films with these techniques, we introduce simple process design for high quality thick films for MEMS devices. Here, we also describe the property relationships between the effects of film composition and thickness on the piezoelectric and dielectric properties of high quality PZT thick films and applications in MEMS devices in detail.