SILC and NBTI in pMOSFETs With Ultrathin SiON Gate Dielectrics

Degradation of pMOSFETs under negative gate bias stress has been intensively studied, bearing in mind the macroscopic and phenomenological similarity between stress-induced leakage current (SILC) and negative bias temperature instability (NBTI). By investigating the electrical characteristics of small-size pMOSFETs, the microscopic mechanisms of the degradation have been vividly revealed. In particular 1) NBTI-induced positive charge generation leading to a decrease in gate hole current and 2) some kind of leak path formation giving rise to SILC are found to occur in parallel, but not simultaneously. This finding enables us to conclude that SILC and NBTI in pMOS are not linked directly at least from the microscopic perspective despite their macroscopic similarity. These results have brought about new insights into the degradation of pMOS under negative gate bias, which is now quite important to CMOS reliability