UV assisted low temperature nitridation and post deposition oxidation technique for hafnium oxide gate dielectric

An evaluation of a low temperature method (∼400 °C) for synthesis of nitrogen incorporated hafnia gate dielectric has been reported. This method is based on metal film growth in ammonia ambient and subsequent oxidation under ultraviolet (UV) irradiation. X-ray photoelectronic spectroscopy confirmed the presence of nitrided interface layer with a thickness of ∼12 ?. Equivalent oxide thickness values of around 11.5 ? and leakage current densities lower than 1 × 10⁻⁴ A/cm² at an operation voltage (−1 V) were achieved. The post deposition ultraviolet oxidation process was performed to check the interface oxidation resistance. The interface growth rate showed that as the interface bonding characteristics changed from Si-N to Si-O predominant bonding system of nitrogen incorporated films, the activation energy for oxygen diffusion changed from 18.0 kJ/mol to 9.8 kJ/mol and the activation energy of undoped hafnia films was 2.3 kJ/mol in every growth region.