Atomic layer deposition temperature dependent minority carrier generation in ZrO2/GeO2/Ge capacitors

Abstract

Low leakage ZrO2 dielectrics with a thickness of 7 nm are grown by means of atomic layer deposition (ALD) on GeO2-passivated Ge substrates. Substrate temperatures during the deposition of ZrO2 are set to 150 and 250 °C, respectively. The influence of the deposition temperature on electrical and structural properties of metal-oxide-semiconductor capacitors is investigated. A significant impact of the ALD temperature on the high frequency capacitance in inversion is demonstrated. The deposition at 250 °C leads to a substantial loss of interfacial GeOx indicated by time-of-flight secondary ion mass spectroscopy. The loss, which gives rise to trap levels near the oxide/Ge interface, shifts the thermal activation energy of minority carrier generation from a full Ge-bandgap energy to midgap energies.