Processing Effects for Integrated PZT: Residual Stress, Thickness, and Dielectric Properties

Abstract

Processing effects on the dielectric properties of sol-gel-derived PbZrO 3 -PbTiO 3 (PZT) films integrated onto Pt/Ti/SiO 2 //Si substrates are reported. Sol-gel synthesis and deposition conditions were designed to produce films of varying thickness (95-500 nm) with consistent chemical composition (Pb (Zr 0.53 Ti 0.47 )O 3 ), phase content (perovskite), grain size (B110 nm), crystallographic orientation (nominally (111) fiber textured), and measured residual stress. The Stoney method, using laser reflectance to determine wafer curvature, derived biaxial tensile stress values of 150 and 180 MPa for PZT films after a baseline correction for electrode interactions during thermal processing was employed. The PZT films were of high dielectric quality, with low losses and negligible dispersion. Calculated values of dielectric constant ( K 0 ) were found to decrease from 960 to 600 with decreasing film thickness. A series-capacitor model successfully recovered a room-temperature K 1 0 for the PZT (1,170) in good agreement with bulk reports but was unable to reproduce the expected dielectric anomaly near 3801C. This discrepancy and the resulting diffuse phase transformation were attributed to the biaxial tensile stress present in the PZT films. 2839J ournal

Suspension high velocity oxy-fuel spraying of TiO 2 : A quantitative approach to phase composition

“…The negative values of F(110) for TG72, TG85 and TG101 coatings indicate that the measured intensity is less than in the randomly oriented sample [45]. On the other hand F(101), for the same three coatings, reach ~0.2 values which are virtually the same as reported for plasma sprayed TiO2 coatings by Li and…”

Residual stress effects on piezoelectric response of sol-gel derived lead zirconate titanate thin films

“…For comparison between films, an assumption of circular grains resulted in calculated average grain diameters of 124, 125, and 122 nm for the films with thicknesses of 190, 350, and 500 nm, respectively. Furthermore, x-ray diffraction testing, presented in full for the same films by Ong et al, 22 confirmed that phase-pure perovskite existed for all three films.…”

“…Measurements from SEM micrographs indicated a consistent grain density across each of the thicknesses, with an average grain diameter of ϳ110 nm based on a linear intercept method. 22 Results from standard dielectric tests performed 25,26 on each specimen using a Precision LCR meter ͑Hewlett-Packard 4824A͒ are also included in Table I. These values reflect the average of tests taken from a number of electrodes across the specimen.…”

“…However, no evidence of grain size changes was found from SEM cross-sectional micrographs. In addition, a series-dilution model analysis 22 of the dielectric response determined that a constant impedance factor existed between the films, which indicates dense films with no variation in properties between layers.…”

“…Spierings et al 1,20 and Zhang et al 21 have reported on the need for correction of the base line curvature ͑R 0 ͒ when determining residual stresses in PZT films deposited on Pt/ Ti/ SiO 2 ʈ Si substrates. Following a process described in detail by Ong et al, 22 at least two identical PZT/ Pt/ Ti/ SiO 2 ʈ Si specimens were fabricated ͑at each thickness͒ so that one could be used for further analysis, and the other could have the PZT film removed by an etchant, to reveal the radius of curvature of the heat-treated Pt/ Ti/ SiO 2 ʈ Si substrate alone. Removal of the PZT thin film was achieved with a solution of hydrochloric acid and ammonium bifluoride in water.…”