Effects of stress annealing on the electrical and the optical properties of MOS devices

Abstract

In this paper we show the results of a study of the effects of high-temperature stress annealing in nitrogen on the refraction index of SiO2 layers and electrical properties in metal-oxide-semiconductor (MOS) devices. We have experimentally characterized the dependence of the reduced effective contact potential difference (ECPD), the effective oxide charge density (Neff), and the mid-gap interface trap density (Dit) on the annealing conditions. Subsequently, we have correlated such properties with the dependence of the refraction index and oxide stress on the annealing conditions and silicon dioxide thickness. Also, the dependence of mechanical stress in the Si-SiO2 system on the oxidation and annealing conditions has been experimentally determined. We consider the contributions of the thermal-relaxation and nitrogen incorporation processes in determining changes in the SiO2 layer refractive index and the electrical properties with annealing time. This description is consistent with other annealing studies carried out in argon, where only the thermal relaxation process is present.