Electrical properties of vacuum annealed La2O3 thin films grown by E-beam evaporation
In this article, the conduction mechanisms of metal-oxide-semiconductor with vacuum annealed Lanthana (La2O3) oxide film are investigated. Lanthana films with thicknesses of 3.5, 4.7, and 11nm were deposited by E-beam evaporation on n-Si (100), and annealed at various temperatures (300500C) in ultra-high vacuum (10?1010?9Torr) for 90min. From the measurement of spectroscopic ellipsometry, it is found that film thickness is increased with annealing temperature, which would be cause of flat-band voltage shift (?VFB) due to the growth of interfacial layer. From the capacitance measurement, it is found that ?VFB of the film is reduced by post-deposition anneal (PDA) compared to that of as-deposited film, but increase again at high temperature annealing, especially in the case of thin film (3.5nm). From the applied voltage and temperature dependence of the leakage current of the film, with different gate electrode materials (Ag, Al, and Pt), it is shown that the leakage currents are associated with ohmic and PooleFrenkel (PF) conductions when flat-band voltage (VFB) is less than zero, and ohmic and Space-Charge-Limited Current (SCLC) conductions when VFB is greater than zero. The dielectric constants obtained from PF conduction for Al gate electrode case is found to be 11.6, which is consistent with the CV result 11.9. Barrier height of trap potential well is found to be 0.24eV from PF conduction. Based on SCLC theory, leakage currents of 3.5 and 11nm films with different PDA temperatures are explained in terms of oxide trap density.
vacuum annealing la2o3 high-k rare earth oxide poolefrenkel conduction space-charge-limited conduction