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 Ǻ. Equivalent oxide thickness values of around 11.5 Ǻ 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.