Demonstration of Large Flatband Voltage Shift by Designing Al_2O_3/SiO_2 Laminated Structures with Multiple Interface Dipole Layers

摘要

We studied the dipole induced flatband voltage (VFB) shifts of Si MOS capacitors with Al_2O_3/SiO_2/Al_2O_3/SiO_2/Si laminated stacks ((Al_2O_3/SiO_2)_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 Al_2O_3-on-SiO_2 interfaces were selectively formed, while those at SiO_2-on-Al_2O_3 interfaces were effectively suppressed. The employed SiO_2 deposition process was suggested to be one of the key parameters to determine the formation or suppression of interface dipole layer at SiO_2-on-Al_2O_3 interface.