DRY OXIDATION MECHANISMS OF THIN DIELECTRIC FILMS FORMED UNDER N2O USING ISOTOPIC TRACING METHODS

We investigated the mechanisms of thermal reoxidation in dry O-2 Of si licon oxynitride films prepared by processing Si(100); wafers in a rap id thermal furnace in a pure nitrous oxide (N2O) ambient, using isotop ic tracing of oxygen and nitrogen. Standard nuclear reaction analyses for the measurement of the total amounts of the different isotopes, an d very narrow resonant nuclear reactions for high resolution (1 nm) de pth profiling of these elements were used. The silicon oxynitride film s grown in pure (N2O)-N-15-O-16 were 8-nm thick, with a small amount o f nitrogen localized near the interfacial region. Under reoxidation in dry O-18(2), the thickness of the dielectric film increased while a p ronounced isotopic exchange took place between the O-18 from the gas a nd the O-16 from the film, as well as a significant loss of N-15. This is in contrast with the reoxidation in dry O-2 Of pure SiO2 films, wh ere the oxygen exchange is rather small as compared to that observed i n the present case. (C) 1996 American Institute of Physics.