Conductive-atomic force microscopy characterization of Ta₂O₅/SiO₂stacks and the effect of microwave irradiation

Abstract

The local electrical properties of ultrathin (4 nm) sputtered Ta2O5 on Si was studied by the conductive atomic force microscopy (C-AFM) technique. A current degradation during the repeatedly applied ramped voltages on the same dielectric point was observed, and the current increase was interpreted as stress-induced leakage current. With increasing applied voltages the impact of more leaky regions in the current map is stronger due to defect generation and the start of trapping/detrapping processes in these defects. Short exposure (seconds) to microwave irradiation acts as an annealing process of nanoscale level electrically active centres. The individual effect of both interfacial SiO2-like and bulk Ta2O5 layers on the current–voltage (I–V) characteristics, and the difficulties in the data interpretation when using the known methods typical of macroscopic measurements were discussed. If the stack parameters used in the I–V curves fitting procedure are not known accurately the conclusion on the mechanism of conductivity is uncertain. Therefore, C-AFM as a novel characterization technique should be further developed to make it adequate for high-k stacks I–V data interpretation.

Nanoscaled Electrical Characterization

“…Depending on the coating or shape of the tip e.g. Co/Cr, Pt/Ir or diamond, the values for the emission area in literature range from 10 to 500 nm 2 [34,35].…”