Stress measurements of Pt/PZT/Pt thin-film stack on oxidized silicon substrate for micro-actuator

The residual stresses in Pt/PZT/Pt thin-film stack coated on an oxidized Si substrate for micro-actuator were investigated. The thin-film stack was prepared with sputtering Pt/Ti films as bottom and top electrodes, and with sol-gel coating of PbZr 0.52 Ti 0.48 O 3 (PZT) film using a three-step heat-treatment process. The residual stresses in the film stack were then measured from the changes in the radius of curvature of the wafer. The Pt/Ti electrodes effect strongly to the residual stress in the thin-film stack and the largest stress was found after the first PZT layer's coating ( ≈ - 700 MPa, compressive) because of the simultaneous annealing of the Pt/Ti bottom electrode. The residual stress decreased from the second PZT layer's coating, and finally showed a compressive stress ( ≈ - 150 MPa) in the whole Pt/PZT/Pt thin-film stack.