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|Enhanced Structure Stabilization and Piezoelectric Properties of PZT Thin Films for MEMS Applications|
|Keywords: MEMS, PZT Thin Films, Piezoelectricity|
|Piezoelectric thin films have been key components of high precision sensors, actuators and ultrasonic probes which play an important role in the maintenance of many critical industrial processes for MEMS. Generally the bulk micromachining and surface micromachining processes are used to make the 3-dimensional structure type devices for MEMS. These MEMS processes are done by stacking structure type, which have top and bottom electrode. However, there have been serious adhesion problems between piezoelectric thin films and metal electrodes during the patterning or etching process because of the different stress levels and different lattice parameters from various thin film materials. These phenomena have been serious obstacles to realize MEMS devices. To solve these drawbacks, we systematically investigated the influence of oxygen addition during the Pt or conductive oxide top electrode deposition and the selection of appropriate adhesion layer for bottom electrode structure. It is found that oxygen controlled Pt top electrodes or conductive oxide electrodes and stable bottom electrode structure for PZT thin films can be achieved excellent adhesion properties and induce excellent ferroelectric and piezoelectric properties for piezoelectric MEMS devices Polarization hysteresis loops of the PZT films show excellent squareness and high remanent polarization in 4 micrometer-thick films, which indicate switching kinetics of these PZT films are closer to the ideal hysteretic behavior. The measured d33 values of 4 micrometer-thick PZT films are 250 ~ 260 pC/N, which are comparable with those of bulk materials.|
|Seung-Hyun Kim, Vice President
Ansan, Gyeonggi 426-901,
Republic of Korea