Sol-gel Derived PZT Thin Films Research Articles

Preparation and properties of sol-gel derived PZT thin films for decoupling capacitor applications

Abstract The use of ceramic thin films as decoupling capacitors offers the possibility of capacitor integration within the integrated circuit (IC) package, and potentially, directly onto the IC itself. Since these configurations minimize series inductance, higher operational speeds are possible. In the present study we have investigated the dielectric and leakage characteristics of sol-gel PZT films. For compositions near the morphotropic phase boundary, dielectric constants of 1000, and loss tangents of about 0.02, were observed. The current-voltage behavior of the capacitors was characterized by a non-linear response, and significant asymmetry in both the leakage and breakdown characteristics as a function of bias sign was observed. Breakdown fields for PZT 53/47 thin films were typically ∼800 kV/cm at 25°C. We have also studied the effects of La and Nb dopant additions and alternate firing strategies on film leakage characteristics. Donor doping at 2–5 mol% lowered leakage currents by a factor of 103 F...

An I-V measurement method and its application for characterizing ferroelectric PZT thin films

Abstract A static I-V measurement method for ferroelectric thin films is developed to distinguish the leakage current from the switching current. The initial polarization state and the exponential decay behavior of the switching current are considered in this method. The feasibility of this I-V measurement method is investigated by examining fatigue effects on sol-gel derived PZT thin films. Changes in polarization due to fatigue are correlated with the changes in the switching current and the leakage current.

Effect of Microstructure on the Electrical Characteristics of Sol-Gel Derived PZT Thin Films

ABSTRACTThe effects of the microstructure of PZT sol-gel thin films, processed using different solutions, on their material and electrical properties have been studied. The films have different degrees of preferred orientation of the perovskite crystals as well as different grain size. The material characteristics are evaluated using SEM micrographs and XRD. Correlation of these material properties with the electrical properties for both NVRAM and DRAM applications is made.

Effect of post-metallization annealing on the ferroelectric properties of sol-gel derived PZT thin films

A series of monolithic Pt-PZT-Pt capacitors was prepared based on sol-gel derived PZT 53/47 films fired to 700 C. After deposition of top Pt electrodes, the capacitors were subjected to post-metallization annealing (PMA) temperatures of 100 C to 700 C. Dielectric and ferroelectric (FE) characterizations were performed. Increasing the PMA temperature produced lower values of spontaneous and remanent polarizations, dielectric constant and leakage currents. The observations are correlated with a proposed FE capacitor model.

Total-dose radiation effects on sol-gel derived PZT thin films

Sol-gel derived PZT (lead zirconate-titanate) thin films were irradiated to a total-dose of 1 Mrad(Si) or 86 krad(PZT) under open-circuit bias. An asymmetric distortion in the hysteresis curves was observed. The distortion depends on the polarization state of the capacitor before irradiation. Postirradiation electrical cycling makes the hysteresis loops symmetric initially, but results in fatigue effects. The leakage and switching current behavior after irradiation and post-rad cycling were studied using a static current versus voltage measurement. Retention and fatigue properties are not worsened after irradiation except for the polarization reduction. The radiation effects are consistent with the sheet charge model. The fatigue effects due to post-rad cycling are consistent with an increase in the space-charge regions near the electrodes or oxygen-deficient dendrite growth. >

Optimization of Sol-Gel Derived PZT thin Films by the Incorporation of Excess PBO

ABSTRACTA series of PZT precursor solutions was prepared which incorporated excess PbO to give the composition Pb1+xZr0.53Ti0.47O3+x, where 0 < × < 0.3. These solutions were spin coated on platinized Si wafers and fired at elevated temperatures up to 750C for 30 mins. After crystallization into single-phase perovskite, the films were studied using XRD, optical microscopy and electrical characterization techniques (hysteresis loops and dielectric properties). It was found that the presence of excess PbO significantly improved the PZT films in terms of phase assemblage, microstructure and electrical properties. Under optimized conditions, films with dielectric constants of around 3000 can be obtained.

Microstructural Evolution of Sol-Gel Derived PZT Thin Films

AbstractTransmission electron microscopy (TEM) was used to investigate the microstructural evolution of sol-gel derived ferroelectric PZT films. Aggregates of perovskite crystals nucleated and grew out of a pyrochlore matrix at 550°C. A dense, single-phase perovskite PZT film was obtained by fast firing the film at 650°C for 30 minutes. The grain size of this film was approximately 0.2-0.4 μm. Hot-stage TEM observed disappearance of ferroelectric domains as the temperature approaching 325°C.

Fatigue and Aging in Sol-Gel Derived PZT Thin Films

ABSTRACTTypical fatigue and aging characteristics are reported for thin PZT films prepared using sol-gels. The fatigue process occurs in two steps. There is an initial period, during which the domain matrix of the as formed film is restructured by the cycling and the polarization generally increases, followed by a period in which the polarization decays. The polarization decay may be due, in part, to the formation of dielectric layers at the electrodes. The effects of voltage and temperature on fatigue are reported. Aging is examined as a function of temperature. Measurements of internal bias fields do not support the view that they are the primary cause of aging. Neither fatigue nor aging are temperature sensitive making identification of specific physical processes difficult.