Chemical Reaction and Diffusion in Materials for MOSIC

在这项工作中，我们研究了电子器件和材料制造过程中的化学反应和扩散，即。，材料为MOSIC。工作内容包括：(1)硅片热氧化动力学，(2)rf溅射表征SiO_2薄膜，(3)蒸发和冷凝过程机理，(4)La_2O_3-WO_3二元氧化物体系的电致变色。这些研究的概要如下。(1)硅片热氧化动力学。CO_2环境下的氧化速率远小于O_2环境下的氧化速率。可以认为，在CO_2中氧化更适合于形成极薄的氧化膜。结果表明，氧化反应速率受氧化剂在SiO_2中的扩散控制，氧化产物分别为O_2和CO_2气体分子。(2)射频溅射表征SiO_2薄膜。与传统的真空沉积法不同，溅射法的薄膜生成速率是恒定的。估计O_2的折射率和扩散系数与热生长氧化物的折射率和扩散系数基本相同。(3)蒸发冷凝过程机理。采用真空沉积法研究了蒸发冷凝速率与源温度和基材温度的关系。当源物质为LiBO_2 - b_2o_3时，根据热力学和气体动力学理论，推测其蒸汽组分为LiBO_2。(4) La_2O_3-WO_3二元氧化物体系的电致变色。介绍了La_2O_3-WO_3二元氧化体系的电致变色特性。目前正在研究EC细胞的产生机制和特性。

In this work, we have studied chemical reaction and diffusion in the manufacturing process of electronic devices and materials,i.e.,the materials for MOSIC. The work contains the following contents:(1)the kinetics of thermal oxidation of Si wafers, (2)the characterization of SiO_2 films by rf-sputtering,(3)the mechanism of evaporation and condensation process,and (4)the electrochromism of the La_2O_3-WO_3 binary oxide system. The outlines of these studies are mentioned as follows.(1)Kinetics of thermal oxidation of Si wafers.The oxidation rate in the ambient of CO_2 was much smaller than that in that of O_2.It can be considered that the oxidation in CO_2 is more suitable to the formation of very thin oxide-film. It was estimated that the reaction rate of the oxidation was controlled by the diffusion of the oxidant in SiO_2 and the species were O_2 and CO_2 gas molecules,respectively.(2)Characterization of SiO_2 films by rf-sputtering.The peoduction rate of the film by sputtering was constant, unlike that by the conventional vacuum deposition method. The values of the refractive index and the diffusion coefficient of O_2 were estimated to be almost the same with those of the thermally grown oxides.(3)Mechanism of evaporation and condensation process.The dependence of the evaporation- and condensation-rate on the source- and the substrate-temperaure were investigated with the use of the vacuum deposition method. When the source material was Li_2O-B_2O_3,the vapor species was estimated to be LiBO_2 by virtur of thermodynamics and the kinetic theories of gases.(4)Electrochromism of the La_2O_3-WO_3 binary oxide system.The electrochromism(EC) of the La_2O_3-WO_3 binary oxide system was presented. The production mechanism and the characte-ristics of the EC cells are now being studied.