Interface Analysis of Transparent Analog Capacitor Using ITO Electrodes and ALD High-k Dielectrics

For the first time, we report transparent analog capacitors using ITO electrodes and HfO2 (and/or Al2O3) high-k dielectrics. The use of ITO bottom and top electrodes did not cause the electrical degradation to the capacitor compared to TiN and Pt electrodes. In the viewpoint of analog capacitors, capacitors using ITO electrodes show a few different characteristics. The right-side inclination of a C-V curve in ITO electrodes suggests that there is a thicker depletion layer at the top interface. This is probably due to the high resistivity of the Sn-rich top ITO initial layer on the dielectric film. Before and after subsequent thermal annealing, while the C-V curve of ITO/Al2O3/ITO is hardly changed, that of ITO/HfO2(or HAH)/ITO is greatly changed. Our results demonstrate that this comes not from the crystallinity change of ITO and/or HfO2 but from the composition change (ex. Hf diffusion and oxygen deficiency) at the interface.