| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 87 === Much attention has been paid to the application of ferroelectric films to the fabrication of integrated capacitors. Pulsed laser deposition (PLD) process is advantageous over other thin film deposition techniques in the accuracy in composition control and the simplicity in process control. However, improvement on the uniformity of PLD films is needed for practical application. In this study, we modified the pulsed laser deposition process for synthesizing the PZT films, emphasizing the effect of the process of multi-layer deposition on the electrical properties of PZT film.
The PZT films were prepared by pulsed laser deposition (PLD) technique (l=248 nm, Lambda Physik, Lextra 300) with an energy density of 7 J/cm2. The films were deposited at 200℃ in 0.05 mbar oxygen pressure (Po2) on Pt-coated silicon substrates, followed by rapid-thermal-annealing at 550~650℃ under 1 atm Po2. The crystallinity of the films was examined by X-ray diffractometry. The electrical polarization vs. electric field and leakage current density vs. electric field characteristics of the PZT films were measured using the Sawyer-Tower technique and H. P. 4156 parameter analyzer, respectively.
In multi-layer PLD process, the crystallinity of the PZT/Pt(Si) films is optimized when the films were PLD in 0.05 mbar Po2 (at 200℃), followed by rapid-thermal-annealing (RTA) at 550~650℃(1~60 s). XRD results indicate that it needs at least 575℃ to convert the amorphous PZT into perovskite.
Multi-layer pulsed laser deposition process has been successfully applied for growing the Pb(ZrxTi1-x)O3, PZT films. The multi-layer PZT films exhibit better ferroelectric characteristics (Pr=18 mC/cm2; Ec＝60 kV/cm) then single-layer PZT film (Pr=10 mC/cm2; Ec＝60 kV/cm).
In summary, multi-layer PLD process has been successfully applied for synthesizing PZT films. Using predeposition PZT thin film as buffer layer results in a PZT film, possessing ferroelectric properties superior to the Ec and Pr values of PZT films with one layer.
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