Effect of the Fixed Charge Distribution on the Mobility Degradation of the High-k Dielectric MOSFETs

Abstract

The effects of the fixed charge in the high-k dielectric layer near a SiO2 layer on the mobility degradation mechanisms were investigated by using a full three-dimensional technology computer aided design simulator. The electron density and the electric field in the channel region were significantly affected due to the fixed charge in the SiO2 layer and the interface between SiO2 and HfO2 layers. The electron density in a channel increased with increasing fixed charge concentration, resulting in a decrease in the mobility. The variation of the vertical electric field due to the fixed charge in the high-k dielectric layer was attributed to the degradation effect. The electric field in a channel deteriorated the electron mobility due to the electron attraction to the heterointerface of the substrate and the interfacial layer. The mobility decreased with increasing fixed charge concentration near the heterointerface of the substrate and the SiO2 layer. The effect of the fixed charge distribution on the mobility degradation of the high-k dielectric MOSFETs was described on the simulation results.