We investigated the role of hetero interface of ionic high-k and covalent SiO_2 on flatband voltage (V_(fb)) and threshold voltage (V_(th)) shifts for CMOS and TFT. The V_(fb) and V_(th) of CMOS and TFT including high-k/SiO_2 gate insulator were influenced due to the bottom interface dipole which causes at high-k/SiO_2 interface. It is clear from experimental results that the direction and strength of the dipole moment strongly depend on oxygen concentration at high-k/SiO_2 interface. We also found that GIZO TFTs with an Al_2O_3/SiO_2 gate insulator exhibited positive V_(th) shift, electron mobility degradation by the fixed charge at Al_2O_3/GIZO interface and the bottom interface dipole at Al_2O_3/SiO_2 interface. The hetero interface of high-k and SiO_2 layers is very important not only for recognizing the mechanism of V_(fb) and V_(th) shifts but also for designing nano-electronic devices with high-k/SiO_2 stack structure.
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