The contribution of border traps to the threshold voltage shift in pMOS dosimetric transistors

The instability of pMOS dosimetric transistors in the form of threshold voltage drift could be an important source of errors in low dose measurements. The source of the drift is, according to the recent nomenclature, switching states concerned with near-interfacial oxide traps (border traps), and we have investigated them for 10 different types of specially prepared pMOS transistors. It has been found that the density of these states depends on the received dose, the bias during irradiation, the temperature, and the thickness of the gate oxide and its hydrogen content. A tunneling model that successfully describes the threshold voltage drift and explains these experimental results is presented. The possible physical picture of border traps and two specific structural models of defects in the SiO/sub 2/ which could be concerned with these experimental results are also discussed.