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 in the study of changes in the hydrogen profiles caused by ex-situ irradiation are discussed. It is shown that the method is sensitive enough to provide the first clear measurements of the hydrogen distribution in bulk SiO₂ (500-1000 ppma). 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. 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