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Containing nano high κ Frequency dependence of Ta2O5 dielectric MOS capacitor characteristics

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Document pages: 11 pages

Abstract: When studying the voltage and frequency dependence, the capacitance of metal insulator silicon structure containing high dielectric constant dielectric shows complex behavior. From our study of metal (al, Au, w) - Ta2O5 SiO2 – Si structure, we find that the serial C-R measurement mode is more convenient to use than the parallel C-R measurement mode commonly used to characterize similar structures. A strong frequency dependence is observed, which is not caused by the actual change of dielectric constant of each layer. Due to the leakage in Ta2O5 layer, the capacitance at low frequency is very high. We find that the above observations are mainly due to different leakage current mechanisms in the two different layers constituting the stack. This effect is highly dependent on the applied voltage because of the leakage currentre strongly nonlinear functions of the electric field in the layers. Additionally, at low frequencies, transition currents influence the measured value of the capacitance. From the capacitance measurements several parameters are extracted, such as capacitance in accumulation, effective dielectric constant, and oxide charges. Extracting parameters of the studied structures by standard methods in the case of high-κ interfacial layer stacks can lead to substantial errors. Some cases demonstrating these deficiencies of the methods are presented and solutions for obtaining better results are proposed.

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