Physical and Chemical Properties of Aluminum Oxide Film Deposited by AlCl₃-CO₂-H₂System

Abstract

The changes of structure and physico-chemical properties of aluminum oxide film with deposition and heat treatment temperatures have been investigated by infra-red spectroscopy, X-ray diffraction analysis, electron probe analysis, ellipsometry, microscopy and etch rate measurement. The films have been deposited on a heated silicon substrate in the temperature range of 400∼1000°C by AlCl3–CO2–H2 system and heat-treated in H2, O2 and Ar atmospheres between 500°C and 1300°C after deposition. Results show that the composition of the film is affected by the imperfection of reactions. By the heat treatment at high temperature aluminum oxide film crystallizes, and changes of structure and properties of the film depend on the deposition temperature as well as heat treatment procedures, and the film proceeds through various stages to α-alumina. The damage of the surface of the film by heat treatment is explained by the large thermal expansion coefficient of the film, and is also caused by vapor etch by HCl formed by the reaction between H2 gas and chlorine contained in the film deposited at low temperature. The growth of silicon dioxide film underneath aluminum oxide by oxygen heat treatment is limited by the substitutional diffusion of oxydizing species into aluminum oxide and the new formed film, and also depends on the strength of Al–O bond of aluminum oxide.