Nanoscale investigations: Surface potential of rare-earth oxide (Re2O3) thin films by kelvin probe force microscopy for next generation CMOS technology

Abstract

Here, the surface morphology, quantitative surface charge injection in nanoscale regime, spreading, decay and physical significance of trap charges are systematically investigated on furnace annealed (FA) and rapid thermal annealed (RTA) ultrathin rare earth oxide (Re2O3), Er2O3/Si structure by Kelvin probe force microscopy (KPFM). The computed charge decay and contact potential difference (CPD) are found as a strong function of injected charges along with the type of subjected post deposition annealing treatment. The RTA treated Er2O3 films showed higher CPD value (∼266mV) and lowest charge spreading (∼2.1µm) for trapped holes than the FA (CPD ∼196mV and charge spreading ∼2.27µm). The CPD for negative bias are computed higher (∼196mV and ∼266mV) than that of the corresponding positive (∼–184mV and ∼-229mV) in both FA and RTA treated Er2O3/Si structures, respectively. It reveals easier holes trapping than electrons and n-type nature of sputtered Er2O3 ultrathin films. There is a significant ∼80% vertical charge decay and ∼20% lateral spreading for first 60min due to conjunction of effective injected and polarization charges. Thus, the FA and RTA treated Er2O3 films are potential candidates for CMOS and NVRAM applications, respectively.