A QUANTITATIVE INVESTIGATION OF HYDROGEN IN THE METAL-OXIDE-SILICON SYSTEM USING NRA

The present state of development in the application of Resonant Nuclear Reaction Analysis to the direct measurement of hydrogen concentration profiles throughout the Metal-Oxide-Silicon system is presented. Detection limits of less than 1018 cm−3 (1012 cm−2) as well as a depth resolution of better than 10 nm are obtained. Limitations of the technique to study changes in the hydrogen profiles caused by ex-situ irradiation are discussed. It is shown that the method is sufficiently sensitive so as to provide the first clear measurements of the hydrogen distribution in the bulk SiO2 (500–10000 ppma). Also presented is a demonstration of the radiation induced migration of atomic hydrogen to both the Si-SiO2 and Al-SiO2 interface, under the action of the analyzing beam, at cryogenic temperatures. Preliminary results of hydrogen profiles following 2.5 MeV e− irradiation, at room temperature under positive and negative bias, suggest the migration of hydrogen as a proton. Evidence is provided which indicates that the dominating source of hydrogen for the bulk SiO2 may not be the oxidation process, rather, the surface layer formed through exposure to air, between the oxidation and evaporation processes may, in some cases, determine the bulk level, especially following a post-metallization anneal. Finally, some initial data are presented, directly relating the hydrogen content in MOS structures and the measured changes in interface and oxide charges following 60Co irradiation. It is found, for the samples studied here, that samples with greater total hydrogen content are less sensitive to radiation induced changes. © 1990 IEEE