Effects of high field electron injection into the gate oxide of P-channel metal–oxide–semiconductor transistors

Abstract

Electron injection at high field and moderate fluence into the gate oxide of P-channel metal–oxide–semiconductor transistors creates net positive charges and related interfacial states as it has often been reported. A threshold electric field at around 7.2 MV/cm is found for the generation of positive charges. For this same oxide field the interfacial state density increases abruptly. For an average oxide field in the 8–9-MV/cm range, the densities of positive charges and interfacial states increase linearly with the fluence for F<1016 e/cm2 and saturate for F≳1017 e/cm2. The positive charge density is more important near the channel edges. The interfacial state density seems to be homogeneously distributed along the channel. The density of electron traps is negligible for the studied dry gate oxide except in the overlaps above drain and source and in some cases near the channel edges. The negative space charge, resulting from electron trapping in these regions, reduces the length of the electron injection and in some cases the surface of the channel which contributes to the charge pumping current. Two types of relaxation have been observed.