| The trapping behaviour of electronic defects in high-kappa, HfO 2, metal-oxide-semiconductor (MOS) capacitors was investigated using capacitance-voltage and photocurrent-voltage (photo IV) measurements. The tested capacitors had a semi-transparent aluminum gate, HfO2 deposited by metal-organic chemical vapour deposition, a SiOx intermediate layer, and a lightly doped (1 x 1015 cm-3) p-type silicon substrate. Internal photoemission was used to inject electrons from the gate and substrate electrodes for the charge injection study. The centroid of the oxide trapped charge was extracted from photo IV measurements, which confirmed that electrons are readily trapped by and detrapped from a large density of pre-existing defects (>1012 cm-3) in the bulk HfO2 layer. The effective density of trapped charge was highly dependent on stress voltage and was modeled using first-order trapping kinetics with two defects having different capture cross-sections. The results from this work validate the use of the photo IV technique for high-kappa MOS characterization. |
