Ultrathin Silicon Oxynitride Film Formation by Plasma Immersion Nitrogen Implantation

A novel method is proposed to prepare ultrathin silicon oxynitride films for gate dielectrics used in deep submicron MOSFET device structures, namely plasma immersion N implantation into SiO sub 2 films. Plasma immersion implantation pulse voltages in the range 200 to 1000 V, and fluences from 10 sup (16) to 10 sup (17) N dot cm sup (-2) were implanted into thermally grown SiO sub 2 films, with thickness between 3 and 6 nm. The areal densities of N and O in the resulting oxynitride films were determined by nuclear reaction analysis, before and after annealing in high-vacuum. N, O, and Si profiles in the films were determined with sub-nanometric depth resolution by medium energy ion scattering. The results indicate that plasma immersion N implantation allows for shallow and controlled deposition of significant amounts of nitrogen (up to 3.8 nm of equivalent Si sub 3 N sub 4 thickness). Implantation is accompanied by moderate damage at the oxynitride/Si interface which can be recovered by thermal annealing.