Reliability degradation mechanism of the ultra-thin tunneling oxide by the post-annealing

The effects of heat treatments on the reliability of ultrathin gate oxide and the mechanism of the reliability degradation are described. Dielectric breakdown reliability of ultrathin tunneling oxide for various post-annealing conditions is discussed. The dielectric breakdown reliability of ultra-thin tunneling oxide is degraded by high-temperature post-annealing. The charge to breakdown is reduced drastically with increasing annealing temperature and annealing time. The dielectric breakdown reliability degradation of ultrathin tunneling oxide by post-annealing can be explained by the tunneling oxide thinning and electric field concentration due to the increase of roughness at the polysilicon gate/ultrathin tunneling oxide interface. This increase of roughness is due to the grain growth of the polysilicon gate and viscous flow of oxide, which can be enhanced by increasing the annealing temperature and time