Surface stress relaxation in SiO2 films by plasma nitridation and nitrogen distribution in the film

We have investigated the surface stress evolution under nitridation process of silicon oxide by plasma exited nitrogen. The compressive surface stress, which had been formed by thin oxide on Si(1 0 0) were relaxed by the nitridation. During the nitridation, more than 40% of the initial compressive stress in 3 nm oxide was relaxed. We measured the stress evolution for plasma oxide films and thermal oxide films with thickness of 2–5 nm and found the same amount of the relaxation of oxide stress. Less than 3% of nitrogen was incorporated in SiO2, and not located at the SiO2/Si interface but uniformly distributed in the film with forming a N–Si2O bonding.