Capacitance and Interface Analysis of Transparent Analog Capacitor Using Indium Tin Oxide Electrodes and High-k Dielectrics

Abstract

Transparent analog capacitors using indium tin oxide (ITO) electrodes and HfO2 (and Al2O3) high-k dielectrics were examined for optical device applications. The adoption of ITO bottom and top electrodes for the capacitors did not degrade the electrical properties of the capacitors compared to titanium nitride (TiN) and Pt electrodes. Compared to conventional analog capacitors using TiN electrodes, capacitors using ITO electrodes show a larger capacitance at the negative voltages in the capacitance-voltage (C-V) curve. This suggests the presence of a thicker depletion layer at the top electrode, which is probably due to the high resistivity of the Sn-rich top ITO initial layer on the dielectric film. Before and after a subsequent thermal annealing, the C-V curve of ITO/Al2O3/ITO was barely changed, while that of ITO/HfO2/ITO showed significant variations. This was attributed to the change in the composition at the interface (i.e., Hf diffusion and oxygen deficiency) rather than to the change in the crystallinity of ITO and HfO2. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3425806] All rights reserved.