2 MeV electron irradiation effects on the electrical characteristics of metal–oxide–silicon capacitors with atomic layer deposited Al2O3, HfO2 and nanolaminated dielectrics

Abstract

The effects of 2MeV electron irradiation on the electrical characteristics of atomic layer deposited (ALD) high permittivity (high-k) layers of Al2O3, HfO2 and a nanolaminate of them are evaluated. Metal–oxide–semiconductor capacitors with a nominal dielectric physical thickness of 10nm were fabricated on different p-type and n-type silicon substrates. The capacitance–voltage (C–V) and current–voltage (I–V) characteristics of the different structures are analyzed as a function of electron irradiation. A progressive negative shift of the C–V characteristics is observed with increasing electron irradiation, indicating the generation of effective positive charges. Similar generation rates for effective trapped charges and interface states are obtained for all the different high-k dielectric layers studied. The hysteresis of the C–V curves after irradiation increases in the case of Al2O3 samples, for HfO2 decreases while the irradiation has little impact on the hysteresis of the nanolaminate stack. A progressive increase of the leakage current with electron irradiation dose is observed for all the studied dielectrics. The analysis of the current–voltage characteristics measured at different temperatures point to Poole–Frenkel as the dominant conduction mechanism. Under the studied conditions, no impact of electron irradiation fluence on dielectric breakdown voltage has been appreciated.