Preparation and Characterization of Ferroelectric Thin Films for Memories by the Chemical Process

铁电存储器近年来引起了人们的广泛关注。溶胶-凝胶法制备铁电薄膜是一种典型的化学法制备方法。本研究开发了制备工艺，并对所得薄膜进行了表征，结果如下。(1)用乙酰丙酮和三水合乙酸铅改性Zr-和ti -丁氧化物制备PZT薄膜。发现醋酸酯在乙醇中的溶解度在单乙醇胺的存在下增加。凝胶膜在700℃下热处理，形成钙钛矿单相铁电膜。(2)在PZT薄膜实验结果的基础上，采用硝酸镧加入部分醋酸铅制备了PLZT薄膜。形成了成分分布均匀的均匀薄膜。研究了它们的铁电性和漏电流等特性与薄膜厚度的关系。(3)采用单乙醇胺稳定的双乙氧基和乙酰丙酮修饰的ti -丁氧基制备了Bi_4Ti_3O_<12>的铁电薄膜，并根据制备条件对其性能进行了研究。(4)经紫外光照射后，β -二酮修饰的凝胶膜在酸性溶液或醇溶液中的溶解度降低。这一发现适用于ZrO_2和TiO_2等单组分的精细图像化，也适用于多组分铁电薄膜的精细图像化。(5)研究了几种三官能团烷氧基硅烷在高温高湿气氛下的水解反应，并考察了溶胶-凝胶法制备的SiO_2膜的性能。

Ferroelectric memories have recently been attracting much attention. The sol-gel process, a typical chemical process, is promising for the preparation of these ferroelectric films. The present study has been done to develop the preparation process and characterize the resultant films, with the following results.(1) PZT films were prepared from Zr- and Ti-butoxides modified with acetylacetone and trihydrated lead acetate. The solubility of the acetate in ethanol was found to increase in the presence of monoethanolamine. The heat-treatment of the gel films at 700 C produced ferroelectric films of the perovskite single phase.(2) Based on the results on PZT films, PLZT films were prepared using lanthanum nitrate in a part of lead acetate. Homogeneous thin films with uniform compositional distribution have been formed. Their properties such as ferroelectricity and leak current were studied as a function of film thickness.(3) Bi-ethoxide stabilized with monoethanolamine and Ti-butoxide modified with acetylacetone were used for the preparation of Bi_4Ti_3O_<12> ferroelectric films and their properties were studied is terms of preparation conditions.(4) The UV-irradiation of gel films modified with beta-diketones was found to decrease their solubility in acidic solutions or alcohol solutions. This finding was applicable to the fine-patterning of single component such as ZrO_2 and TiO_2 and moreover ferroelectric thin films of multicomponent.(5) Hydrolysis of a number of trifuctional alkoxysilanes was studied and the properties of sol-gel derived SiO_2 films were examined in an atmosphere of high temperature and humidity.