Carrier injection into the oxide-film on a semiconductor, transport in the oxide, trapping of the injected carriers, detrapping and changes in the film produced by these phenomena are subject of extensive work of many researchers in the last 25 years. The studies [524][523][521][507][484][447][419][337][336][335][334][330][263][199][129][128][124][102][101][100][46][45][31] represent some milestones in this effort. All these effects normally occur in MOSFETs. In spite of a large effort made to explain the hot-carrier degradation effects and a remarkable progress in the last decade, these phenomena are not well understood [197][107], particularly from the physical aspect [127]. Nevertheless, as a result of a lot of studies, we have been learning how to design devices resistant to hot-carrier aging under regular operating conditions [400][338][225][72].
A specific problem in studying the degradation of MOSFETs is a strong localization of the damaged region close and/or within the drain (source) junction, as opposed to the uniform studies on MOS capacitors and MOSFETs. Several experimental techniques have been developed to analyze the damaged region in MOSFETs:
), transconductance (
), threshold
voltage (
) and subthreshold
slope [499][481][329][328][299][217][108][29][1].
It is believed today, that the hot-carrier injection produces at least three classes of localized damage in MOSFETs, e.g. [426][310][197][107][105][104][103][77][30]:
or 
-channel). The impurity profile in the
semiconductor, the quality of the gate oxide and the spacer oxides and the type
of the gate also play an important role.
Among exhaustive experimental work, a considerable attention has been paid to numerical and analytical modeling of the hot-carrier effects in past. Because of the complex physics involved at the hot-carrier problem and the limited knowledge on the real physical causes, particularly for the trap-creation processes, the state of the art in modeling lays behind the experimental experience in this area. The theoretical methods to tackle the hot-carrier problem in MOSFETs cover
and interface traps
[478][414][215][195][175][33][10].
In this study we restrict ourselves to the charge-pumping techniques. By employing the numerical model, described in Section 3.2, we explored potentials of the charge-pumping measurements to extract information on the damaged region in MOSFETs. Applicability, limitations and sensitivity of the present charge-pumping methods are evaluated in a rigorous manner for the first time.
-Channel LDD MOSFETs