Development of residual stress in sol-gel derived Pb(Zr,Ti)O3 films: An experimental study

Abstract

Access to the full text of the published version may require a subscription. Residual stresses develop in the sol-gel-derived ferroelectric thin films during the transformation of the metal-organic gel to the metal oxide upon thermal treatment and due to the thermal and elastic mismatch between the Pb͑Zr x ,Ti 1−x ͒O 3 ͑PZT͒ film and the substrate materials during cooling. In this study, residual stresses were determined using the wafer curvature method after the deposition of multilayer PZT film on platinized ͑100͒ silicon wafers. A multilayer model for stress analysis was used to calculate the residual stress in PZT films of three different compositions: x = 0.4, x = 0.52, and x = 0.6. Orientation dependent residual stresses were found in compositions containing the tetragonal phase, with x = 0.4 and x = 0.52. Depending on the fraction of ͑100͒ orientated domains low compressive or low tensile stress was found in Pb͑Zr 0.4 Ti 0.6 ͒O 3 ͑PZT 40/ 60͒. Higher residual stress was found in PZT films consisting of only rhombohedral crystallographic structure ͑PZT 60/ 40͒ while the residual stress in PZT films with morphotropic boundary composition ͑PZT 52/ 48͒ was significantly dependent on the film orientation and the phase composition and could range from 17 to 90 MPa. The effect of the film orientation on residual stress was found to be a function of the anisotropic thermal expansion coefficient of PZT. The contribution of the thermal and elastic properties of materials to the total wafer curvature was investigated and discussed. Finally, the residual stress results calculated with the four layer model were compared to the results calculated using the Stoney equation. Rights

Design and fabrication of PZT microcantilevers with freestanding structure

“…6 The residual stress of Pt electrode deposited at different temperature before and after the electrode was annealed at 700°C for 30 min Sputtering of the bottom electrode at 300°C remains a compressive stress of -0.62 GPa in the Pt electrode, and subsequent annealing at 700°C for 30 min changes the stress to be a tensile one of 1.22 GPa. After spin coating and annealing, the final PZT thick film exhibits a tensile stress of 34 MPa that is comparable with the results reported by Corkovic et al (2008). In according with all measured residual stresses in the PZT/ Pt/SO 2 structure, the bending curvature and deflection of a released freestanding microcantilever with certain length can be calculated.…”

“…The high temperature annealing normally causes tensile residual stresses in both PZT and Pt layers due to their much larger thermal expansion coefficient than that of the Si substrate (Jaffe et al 1977;Okada and Tokumaru 1984;Kirby 1991). Experiment data indicate that tensile stress in Pt bottom electrode may be over 1 GPa after the annealing of PZT films (Jeon et al 2000;Zhang et al 2004;Corkovic et al 2008). The tensile stress in CSD-derived PZT films generally changes in the range of 0-200 MPa, dependent on fabrication conditions (Zhang et al 2003;Ong and Payne 2005;Hong et al 2006;Corkovic et al 2008).…”

“…Experiment data indicate that tensile stress in Pt bottom electrode may be over 1 GPa after the annealing of PZT films (Jeon et al 2000;Zhang et al 2004;Corkovic et al 2008). The tensile stress in CSD-derived PZT films generally changes in the range of 0-200 MPa, dependent on fabrication conditions (Zhang et al 2003;Ong and Payne 2005;Hong et al 2006;Corkovic et al 2008). For a PZT freestanding microcantilever in which the substrate is completely removed, different levels of residual stresses in the PZT and Pt bottom electrode layers as well as their different elastic properties easily provoke bending or curling of the structure.…”

Effects of residual stresses on lead–zirconate–titanate (PZT) thin-film membrane microactuators

“…In fabricating these PZT thin-film devices, presence of residual stresses is unavoidable if the films are fabricated via sol-gel processes [10][11][12][13]. Stresses arise when the PZT thin film loses its solvent and shrinks substantially during the sintering process (for example, 650 • C).…”

Compositional and Optical Gradient in Films of PbZrxTi1-xO3 (PZT) Family

“…• Thermodynamically driven diffusion and/or kinetic demixing (Cabrera, and Mott, 1948;Impey et al, 1998;Ohba et al, 1994;Wagner, 1971;Watts et al, 2001 and; • Stress (e.g., lattice mismatch and misfit stress with the substrate; stress dependence of film thickness), (Corkovic et al, 2008;Izyumskaya et al, 2007;Gkotsis et al, 2007); • Nucleation processes (Izyumskaya et al, 2007;Ohba et al, 1994;. Depending on deposition processes involved, some or even all of these factors can be incorporated and accountable for gradient formation in the films.…”