The present work describes new methodology to solve this metrology problem, using TiO2 as an example metal oxide. The approach involves synthesis of a thin film of the semiconductor on an underlying silicon substrate by methods such as chemical vapor deposition or atomic layer deposition. A Schottky diode structure is then fabricated on the film to obtain the doping concentration from high frequency capacitance-voltage measurements. For TiO2, this approach has been implemented with aluminum contacts to the TiO2 and indium-gallium eutectic alloy contacts to the underlying silicon.
The novelty of the structure lies in its compatibility with oxide semiconductors having widely varying doping levels, and the use of easily applied electrical contacts. Oxide thickness, uniformity, and crystal structure can be precisely tailored to suit the subsequent choice of reaction chemistry. A wide variety of fabrication issues have been characterized, including surface and interface preparation, contact metal type, and method of contact metal deposition. Detailed current-voltage measurements confirm diode-like behavior that is free from spurious artifacts and amenable to standard Mott-Schottky analysis. Values for the depletion width, barrier height, and series resistance are reported for the example case of TiO2 synthesized from titanium tetraisopropoxide (TTIP) and O2.