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▼ [5p-C11-3] Anomalous temperature dependence of dipole layer strength at the Al2O3/SiO2 interface
Keywords:dipole, temperature dependence, Al2O3
Several models have been developed to explain the physical origin of the dipole layer formation at high-k/SiO2 interfaces. One of the possible models considers the relative difference in oxygen density at high-k/SiO2 interface as the driving force of the dipole layer formation. However, none of those models reported on the effect of temperature on the interface dipole layer strength. For a wider range of application, it is crucial to comprehend its behavior with the change in temperature. In this study, we investigated the temperature dependence of dipole layer strength in Al2O3/SiO2/Si MOS stacks from 100K to 400K.
A series of Vfb was obtained from various Al2O3 thicknesses and extrapolated to the point where the Al2O3 thickness became zero, to determine the dipole layer strength of Al2O3/SiO2 by removing the influence of fixed charges in the stacks. From 100K to 300K, the dipole strength changed approximately at the rate of 2-3 mV/K, though the rate reduced at higher temperatures. This rate is surprisingly larger than what we expected from a simple consideration of volume expansion. The dipole strength can be increased by lengthening the distance between two opposite charges; however, the thermal expansion coefficient for Al2O3 and SiO2 only ranges in the order of 10-6 K-1 , and 10-7 K-1 , respectively. Thus, it is clear that other anomalous factors contributed to the unexpectedly large change of dipole strength at Al2O3/SiO2 interfaces with temperature.
A series of Vfb was obtained from various Al2O3 thicknesses and extrapolated to the point where the Al2O3 thickness became zero, to determine the dipole layer strength of Al2O3/SiO2 by removing the influence of fixed charges in the stacks. From 100K to 300K, the dipole strength changed approximately at the rate of 2-3 mV/K, though the rate reduced at higher temperatures. This rate is surprisingly larger than what we expected from a simple consideration of volume expansion. The dipole strength can be increased by lengthening the distance between two opposite charges; however, the thermal expansion coefficient for Al2O3 and SiO2 only ranges in the order of 10-6 K-1 , and 10-7 K-1 , respectively. Thus, it is clear that other anomalous factors contributed to the unexpectedly large change of dipole strength at Al2O3/SiO2 interfaces with temperature.