Control of electric charge at the interface in the RTO and low temperature oxidation of SOI

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In the rapid thermal oxidation (RTO) and in the low temperature thermal oxidation of silicon, the incomplete relaxation of intrinsic stress leads to the emission of a lot of interstitial atoms. Consequently, some properties of oxide films and the interface states vary from time to time, which causes it difficult to explain the oxidation behavior with the usual linear-parabolic model. Moreover, in case of the SOI,the complex stress states due to the existence of buried oxide makes it difficult to obtain an oxide layr of good quality. From such a background we constructed the experimental apparatus which was suited for the dynamic analyzes of the thermal oxidation process and established an experimental methodology to study the oxidation mechanism and to control the properties of oxide layr. As a consequence, we obtained many interesting basic data and new knowledge and information in the low temperature thermal oxidation of silicon as follows :1.The oxidation parameters were analyzed from the oxidation curves measured ith an in-situ ellipsometer, and the difference in the oxidation mechanism between the high and the low temperature thermal oxidation was experimentally verified.2.It was found that the emission of interstitial silicon atoms ruled the oxidation rate.3.A stress related model for the emission of interstitial atoms was proposed and experimentally confirmed.4.The orientation dependencies of oxidation rates in varied temperature and oxidation species revealed the roles of intrinsic stress in the oxidation process.5.The addition of an appropriate amount of NF3 in the oxidizing gas reduced the residual stress in the oxide films and improved the C-V characteristics.6.By using an X-ray diffraction technique we found different oxide structures depending on the oxidation temperature, species and the wafer orientation.