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

Summary A functional type metal‐oxide‐semiconductor (MOS) based capacitor was fabricated and studied by using aluminium zirconium oxide (AlxZryOz) 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 AlxZryOz phases were present at 600°C while stablized tetragonal AlxZryOz 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. Silicon‐based metal‐oxide‐semiconductor (MOS) capacitor using AlxZryOz as a potential high dielectric constant gate oxide was studied with regards to interface trap density, oxide trapped charges, dielectric constant as well as crystalline phases, oxide thickness, composition, and energy band gap. Interfacial layer formation was impeded and defect formation was suppressed by nitrogen and hydrogen, respectively. Oxygen vacancy formation and annihilation as well as interstitial oxygen formation affected generation of charged traps.