Residual stress and structure characteristics in PZT ferroelectric thin films annealed at different ramp rates

Abstract

Ferroelectric Pb(Zr 0.55Ti 0.45)O 3 (PZT) thin films were deposited on Pt/Ti/SiO 2/Si(100) by radio-frequency-magnetron sputtering at room temperature and then annealed at 600 °C for 30 s with different ramp rates 1 °C/s, 5 °C/s, 10 °C/s, 20 °C/s and 30 °C/s. The crystallographic orientation and residual stress in PZT films were investigated using an X-ray diffraction technique. The preferred orientation changed from (110) to (111) as the ramp rate increased. In residual stress analysis, both ψ splitting and oscillations were observed in the d − sin 2 ψ curves. Triaxial stress analysis indicated the normal stress components to be significant tensile in all films. The normal stress components in the films increased with the increasing ramp rate before the ramp rate of 10 °C/s, but when the ramp rate rose to 20 °C/s, the normal stresses decreased. The mean grain sizes were obtained by Williamson–Hall plots. The same tendency was observed. A simple calculation indicates that the thermal stresses imposed by the substrates are the same in all films. Therefore, the changes of the residual stresses in the films are mainly due to the variation of grain size and the crystallographic orientation caused by the different ramp rates.