Characterization of positive bias temperature instability concerning interfacial layer thickness of HfSiON/SiO2 nMOSFET

Abstract

This paper investigates how interfacial layer (IL) thickness of HfSiON/SiO2 nMOSFETs affects their responses to positive bias temperature instability. Experimental results show that stress-induced traps and secondary-hole trapping were generated more in a thicker IL nMOS than in a thinner IL nMOS. From these results, the thicker IL nMOS had larger threshold voltage-shift AVd, and lower time exponent n than the thinner IL nMOS at the same oxide field E. At high E, the thicker IL nMOS had shorter lifetime (t(L)) due to larger Delta V-th than the thinner IL nMOS. At low E-ox, related to operating voltage, the thicker IL nMOS had longer tL due to lower n than the thinner IL nMOS. Thus, thickening the IL is applicable to increase t(L) of HfSiON/SiO2 nMOSFET.