Preparation of Ferroelectric PZT Thin Films by Photoenhanced CVD and an Application to Memory Devices

光增强CVD铁电PZT薄膜的制备及其在存储器件中的应用

基本信息

批准号：
04452176
负责人：
SHIOSAKI Tadashi
金额：
$ 3.52万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04452176/
关键词：
Photo-MOCVD PZT thin film O_3 breakdown voltage two step growth process PbTiO_3 buffer layr switching time reversed domain Pb(Zr,Ti)0_3薄膜光励起CVD 比誘電率 D-Eヒステリシスメモリデバイススイッチング特性ペロブスカイト

项目摘要

In photo-MOCVD of PZT,effects of a use of O_3 as an oxidizing gas instead of O_2 and a photoirradiation on the growth were investigated. A decrease in the growth temperature and an improvement in the crystallinity of the PZT thin films were not observed. However, when O_3 and O_3+UV irradiation during the growth run were used, an improvement in the breakdown voltage was observed. This improvement may have been caused by microscopic change in film structure.At high Zr content region, ZrO_2 and pyrochlore phase films were grown and it required high growth temperature to grow rhombohedral PZT thin films. In order to obtain perovskite rhombohedral PZT thin films at high Zr content regions, a two step growth process was proposed. In this method, at first stage, PbTiO_3 buffer layr as an intial layr were deposited and in succeeding process PZT film were grown. Rhombohedral PZT thin films were successfully obtained at higher Zr content regions and at lower substrate temperatures than when this two step growth process was not used.The pulse switching kinetics of ferroelectric PZT thin films grown by MOCVD was also investigated. The switching time was proportionally shortened as the area of ferroelectric thin film capacitor became smaller. On the other hand, both the switching time and the switched charge density had an activation-field dependence on the pulse voltage. It was proven that the pulse switching speed of ferroelectric PZT films is determined by the nucleation rate of reversed domains because the nucleation rate is lowered by the large effective time constant of the measurement system.

在PZT的Photo-MOCVD中，研究了O_3用作氧化气体而不是O_2的影响以及对生长的光照射的影响。未观察到生长温度的降低和PZT薄膜结晶度的改善。但是，当使用在生长运行过程中O_3和O_3+UV辐射时，观察到分解电压的改善。这种改进可能是由于膜结构的显微镜变化引起的。在高ZR含量区域，ZRO_2和Pyrochlore相膜的种植中，需要高生长温度才能生长菱形PZT PZT薄膜。为了在高ZR含量区域获得钙钛矿菱形PZT薄膜，提出了两步生长过程。在这种方法中，在第一阶段，将PBTIO_3缓冲液作为Intial Layr沉积，并在成功的过程中生长PZT膜。与未使用这两个步骤生长过程相比，在较高的ZR含量区域和较低的底物温度下成功获得了菱形的PZT薄膜。还研究了MOCVD生长的铁电PZT PZT薄膜的脉冲开关动力学。随着铁电薄膜电容器的面积变小，切换时间被按比例缩短。另一方面，切换时间和开关电荷密度都对脉冲电压都具有激活场的依赖性。事实证明，铁电PZT膜的脉冲开关速度取决于反向域的成核速率，因为成核速率通过测量系统的较大有效时间常数降低。