Development of Atomic-Scale, Infrared Reflection Spectroscopic Techniques for Characterization of Semiconductor Surfaces

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We have investigated and developed a method of characterizing in the atomic scale the chemical states of silicon wafer surfaces using infrared absorption spectroscopy (IRAS) in the multiple internal reflection geometry (MIR). Because of its high surface sensitivity, IRAS-MIR is a powerful tool for investigating the chemical nature of semiconductor surfaces. The main aim of this study is to develop a monitoring system for measuring in-situ the surface chemical state of silicon wafers whilestored in vacuum, air and solution, and furthermore to determine the performance of the system.As a result, we have for the first time succeeded to monitor the surface chemical states of silicon wafers during storage in hydrofluoric acid (HF) solution with the developed monitoring system. We have demonstrated that the surface while immersed in HF solution is not completely terminated with hydrogen and water rinsing leads to the perfect hydrogen termination. Using the developed monitoring system which enables us to measure the chemical state of Si surfaces in atmospheric environment, we have also investigated the initial stages of oxidation of Si surfaces during storage in air. We demonstrated that the oxidation of the topmost layr of the hydrogen-terminated surface is strongly affected by the moisture of air, and that the oxidation of the surface Si-H bonds leads to the formation of native oxide film.