Analysis and Control of Ferroelectric/Semiconductor(Metal)Interface for Their Device-Application

通过将铁电薄膜与硅器件技术结合，研究了在开发新的存储器件中变得相当重要的界面现象。采用MOCVD法制备的Pb (Zr, Ti) O_3 （PZT）薄膜作为实验铁电物质。从这项研究中得到的重要知识可以简单概括如下。在Ir/SiO_2上沉积的PZT薄膜有良好的台阶覆盖率（76 ~ 93%），而在600℃下沉积的PZT薄膜有Pt/SiO_2台阶变形；这种变形主要是由于Pb向台阶扩散引起的。SiO_2/Si上的Ir和/或Iro_2导电膜在抑制PZT元素向SiO_2扩散方面起到了有效的屏障作用，由它们组成的底电极在SiO_2/Si上的PZT电容器具有良好的极化疲劳性能。为了使金属/铁电/半导体型场效应晶体管（MFS-FET）成功地成为非伏打存储器，必须克服两个严重的困难：(1)在F/S界面上存在的载流子陷阱的数量必须足够小，以便在S侧良好地运行场效应。(2)为了使铁电残余极化在FET沟道上有效地工作，必须设计MFS-FET的栅极F。困难(1)可以通过F膜的高介电常数来克服，而最初，关于(2)，需要进一步的研究来更详细地描述F膜或F电容器的电学特性。

This study has been performed on the interfacial phenomena that heve become of considerable importance in the development of new memory devices by technologically combining ferroelectirc films with silicon devices. The Pb (Zr, Ti) O_3 (PZT) films by MOCVD were used as the experimental ferroelectric species. The importan knowledge derived from this study can be briefly summarized as follows.1.Good step coverage (76-93%) was obtained for thin PZT films depostied on Ir/SiO_2, whereas deformation of Pt/SiO_2 steps was observed when PZT films were deposited at 600ﾟC ; this deformation was mainly caused by the diffusion of Pb into the steps.2.This conductive films of Ir and/or Iro_2 on SiO_2/Si playd the role of an effective barrier in suppressing diffusion of the PZT elements into SiO_2 and, with bottom electrodes composed of them good polarization-fatigue properties were confirmed for the PZT capacitors on SiO_2/Si.3.For Metal/Ferroelectric/Semiconductor type field effect transister (MFS-FET) to succeed as a non-voltaic memory, two serious difficulties must be overcome : (1) the amount of carrier traps existing at the F/S intreface must be small enough for the field effect to operata well at the S side.(2)The gate F Of MFS-FET must be designed so that ferroelectric remnant Polarization can operate effectively on the FET channel. The difficulty (1) can be surmounted by high dielectric constant of the F film, while initially, regarding (2), a further investigation will be needed to give more detailed descriptions of the electrical properties of F film or F Capacitor.