Demonstration of Large Flatband Voltage Shift by Designing Al2O3/SiO2 Laminated Structures with Multiple Interface Dipole Layers

Abstract

We studied the dipole induced flatband voltage (VFB) shifts of Si MOS capacitors with Al2O3/SiO2/Al2O3/SiO2/Si laminated stacks ((Al2O3/SiO2) n /Si, n=2) designed for a large positive shift of VFB. The VFB shift caused by each dipole layer was determined from capacitance-voltage characteristics by excluding the effect of fixed charges. Due to the additivity of multiple dipole layers in the laminated stack, a large VFB shift (>1 V) was observed. In our experimental condition, the dipole layers at Al2O3-on-SiO2 interfaces were selectively formed, while those at SiO2-on-Al2O3 interfaces were effectively suppressed. The employed SiO2 deposition process was suggested to be one of the key parameters to determine the formation or suppression of interface dipole layer at SiO2-on-Al2O3 interface.