Plasma-assisted atomic layer deposition of nanolaminates for gate dielectric applications

Abstract

Thin [(x)Al2O3 + (y)TiO2] nanolaminates (NLs) films of various TiO2 and Al2O3 volume fractions were deposited on n-Si substrates at 250 °C using remote plasma-assisted atomic layer deposition. While the overall thickness of the dielectric was held relatively constant at ∼16 nm, the relative ratio of Al2O3 to TiO2 in the NL was varied by changing the number of deposition cycles of each component. This permitted the evaluation of changes in the dielectric constant κ, index of refraction Nf, optical band gap, Eg, and the electrical performance of the resulting oxides. Capacitance–voltage and current–voltage results on 100 μm diameter circular capacitors were obtained. The data reveals that the high-content TiO2 films show limited evidence of oxide charge trapping and relatively large dielectric constants (k ∼ 15) with reduced reverse-biased leakage current, whereas the high-content Al2O3 films offer a larger optical band-gap and excellent insulating character with reduced leakage currents. In addition, the authors present composition assessments of the oxides by x-ray photoelectron spectroscopy, transmission electron microscopy, and electron energy loss spectroscopy.