Preparation and characterisation of aluminium zirconium oxide for metal-oxide-semiconductor capacitor

A functional type metal-oxide-semiconductor (MOS) based capacitor was fabricated and studied by using aluminium zirconium oxide (Al_xZr_yO_z) as a potential high dielectric constant (k) gate oxide, which was transformed from as-sputtered Al-Zr alloy after undergoing a wet oxidation at 400°C, 600°C, 800°C, and 1000°C in the presence of nitrogen as a carrier gas. A mixture of tetragonal ZrO₂-monoclinic Al_xZr_yO_z phases were present at 600°C while stablized tetragonal Al_xZr_yO_z phases were detected at higher temperatures with a minute micro strain change. The largest k value (21) was obtained by the film oxidised at 600°C, followed by 800°C while the lowest one at 1000°C. The discrepancy was due to the absence of tetragonal ZrO₂ in the latter films. The attainment of a k value closer to the reported value for ZrO₂ at 600°C suggested that the tetragonal ZrO₂ phase was one of the factors yielding a high k value at 600°C. However, further investigation was required for this sample because the slow trap density and total interface trap density was high despite a high k value, mainly attributed to the presence of negatively charged traps as the scattering centre in the film. The film obtained at 1000°C was not encourageable to be deployed as a passivation layer for Si MOS device due to its low k controlled by the thick interfacial layer.