Interface defects responsible for negative-bias temperature instability in plasma-nitrided SiON/Si(100) systems

Interface defects generated by negative-bias temperature stress (NBTS) in an ultrathin plasma- nitrided SiON/Si(100) system were characterized by using ${\mathrm{D}}_2$ annealing, conductance-frequency measurements, and electron-spin resonance measurements. ${\mathrm{D}}_2$ annealing was shown to lower negative-bias temperature instability (NBTI) than ${\mathrm{H}}_2$ annealing. Interfacial Si dangling bonds ${\mathrm{(P}}_{\text{b1}}$ and $P_{\text{b0}}$ centers), whose density is comparable to an increase in interface trap density, were detected in a NBTS-stressed sample. The NBTI of the plasma-nitrided SiON/Si system was thus shown to occur through $P_b$ depassivation. Furthermore, the nitridation was shown to increase the $P_{\text{b1}}{\mathrm{/P}}_{\text{b0}}$ density ratio and modify the $P_{\text{b1}}$ structure. Such a predominance and structural modification of $P_{\text{b1}}$ centers are presumed to increase NBTI by enhancing the $P_b–\mathrm{H}$ dissociation. Although we suggest that NBTS may also induce non-$P_b$ defects, nitrogen dangling bonds do not seem to be included in them.