Dielectric relaxation and Charge trapping characteristics study in Germanium based MOS devices with HfO2 /Dy2O3 gate stacks

摘要

In the present work we investigate the dielectric relaxation effects andcharge trapping characteristics of HfO2 /Dy2O3 gate stacks grown on Gesubstrates. The MOS devices have been subjected to constant voltage stress(CVS) conditions at accumulation and show relaxation effects in the whole rangeof applied stress voltages. Applied voltage polarities as well as thicknessdependence of the relaxation effects have been investigated. Charge trapping isnegligible at low stress fields while at higher fields (>4MV/cm) it becomessignificant. In addition, we give experimental evidence that in tandem with thedielectric relaxation effect another mechanism- the so-called Maxwell-Wagnerinstability- is present and affects the transient current during theapplication of a CVS pulse. This instability is also found to be fielddependent thus resulting in a trapped charge which is negative at low stressfields but changes to positive at higher fields.