Reseach On Leakage Current Characteristics Of PZT Thin Films

Lead Zirconate Titanate(Pb(Zr_xTi_1-x)O₃, short for PZT) thin film is one of the most prospective electronic functional thin films. It was widely applied in Non-Volatile FeRAM, sensors, microactuator, infrarad detectors and electro-optic modulators, due to its high remnant polarization, high dielectric constant, and widely usage temperature range. It is very important to prepare PZT films with highly condensed, smooth surface, and low leakage current, which is an important foundation for developing thin-film devices based on PZT films. Because leakage current characteristics of thin film materials directly reflects the electronic electrical properties of functional thin film materials, hence researching the leakage current characteristics of PZT films is an important technical means for improving performance of PZT films and developing thin-dilms devices. The present paper aimed at leakage current behavior of PZT films to carry out contents as follows:1. We prepared the PZT samples on Pt/Ti/SiO₂/Si substrates by RF magnetron sputtering with various deposition parameters and annealing parameters, and reseached the influence of virious parameters on the structure, morphology and electrical properties of PZT thin films, Then we carried on theory analysis on the effect rules combined with the defect chemistry of PZT. The results showed that the gas flow ratio in depositon process, annealing ambience, annealing temperature and annealing times had a huge influenced on the structure, morphology of PZT thin films, and further influenced the electric properties of PZT thin films. The PZT thin films with surface smoothness, compact structure, minimum leakage current density（J） and optimal Feroelectric, dielectric performance were obtained, which the PZT thin films were prepared under the sputtering atmosphere of Ar/O₂=45:0.65, the annealing atmosphere of Ar/O₂=1:1 and annealed at 650℃ for 60 s in rapid thermal process.2. We analyzed the characteristics of leakage current of PZT thin film which was prepared under the optimum process conditions, and research the leakage current mechanism by analyzing the leakage current density-voltage（J-V） curves and leakage current density-time（J-t） curves. And the results showed that, when V<VT, the mechanism of leakage current obeys ohm’s law; when VT <V< VTFL,which VTFL is the trap filled limit voltage, the mechanism of leakage current obeys space charge limited current（SCLC） with exponential distribution traps; when V> VTFL, the mechanism of leakge current changes to space charge limited current without traps. And the changing of the mechanism of leakage cuerrent will change the characteristics of the J-t curves.3. We analyzed the leakage current-temperature characteristics of PZT thin films, and further proof the leakage current mechanism of PZT thin films, and the position of fermi level was given. And the results showed that, when V<VT, the leakage current increases with the increase of temperature due to the carrier concentration increases with the increase oftemperature, which was in line with Ohm’s Law. And combined with relations we calculated that the fermi level of PZT thin films below 0.6624 eV the conduction band. When V<VT, the leakage current decreases with the increase of temperature, which was in line with the theory of SCLC.