Interface structures generated by negative-bias temperature instability in Si/SiO2 and Si/SiOxNy interfaces

We used a density functional method to investigate the mechanism of negative-bias temperature instability (NBTI) and resultant structural changes of ${\mathrm{Si/SiO}}_2$ and ${\mathrm{Si/SiO}}_x{\mathrm{N}}_y$ interfaces. The reaction energies for the water- and hydrogen-originated instabilities of several interface defects show that water-originated reactions of oxygen and nitrogen vacancies occur most easily. The larger instability of the ${\mathrm{Si/SiO}}_x{\mathrm{N}}_y$ interface, compared with the ${\mathrm{Si/SiO}}_{\mathrm{2}}$ interface, can be understood in terms of the difference in reaction energies. According to the calculated nitrogen $\text{1s}$ core-level shifts of the nitrogen atoms at the ${\mathrm{Si/SiO}}_x{\mathrm{N}}_y$ interface, it is possible to identify a NBTI-generated structure at the ${\mathrm{Si/SiO}}_x{\mathrm{N}}_y$ interface by x-ray photoelectron spectroscopy.