Fabrication of a metal-oxide-semiconductor-type capacitive microtip array using SiO₂ or HfO₂ gate insulators

Capacitive tip arrays having a metal-insulator-semiconductor capacitor structure were fabricated using thermally oxidized SiO₂ or atomic-layer-deposited HfO₂ gate dielectric films for their application to scanning-probe-array-type memory devices. The SiO₂ film showed a nonuniform thickness distribution over the flat and tip areas of the arrays owing to the different oxidation speeds of the flat and tip Si surfaces. This resulted in a smaller sensing margin of the device. However, the high-dielectric HfO₂ film showed not only a higher capacitance value but also a more uniform growth behavior over the whole area, which would result in a better device performance. The capacitance-voltage characteristics of both devices coincide well with the simulation results based on conventional metal-insulator-semiconductor theories.