A method for the assessment of oxide charge density and centroid in metal-oxide-semiconductor structures after uniform gate stress

Abstract

A method for the extraction of the oxide charge density and distribution centroid based on the exploitation of the Fowler plot derivative characteristics is proposed. To this end, the modification of the tunnel transparency due to the presence of charge within the tunneling region is accounted for. Simple analytical formulas which enable the oxide charge density and centroid to be extracted from the maximum Fowler derivative and its electric field position are derived. The comparison with the DiMaria method confirms the overall consistency of the new approach. The impact of negative charge within the oxide on the apparent Fowler barrier height, which can be deduced from the slope of the Fowler plots after uniform gate stress is also analyzed. Finally, it is pointed out that this method permits the oxide trapping properties to be studied even though only one bias polarization can be utilized for the test structure.