Nitrogen incorporated hafnia gate dielectric thin film and titanium based metal gate electrode for dual gate application

We evaluated the effect of nitridation temperature on interface layer (IL) quality of Hf-silicate gate dielectric has been reported. An increase in IL density and IL roughness was observed as the nitridation temperature was increased. Preferential interface reaction at dielectric-Si interface at higher temperatures was analyzed. The progressive increase in IL roughness finally led to degradation of breakdown voltage, shift in flat band voltage (0.54V) and deterioration of electron channel mobility by 20% in samples nitrided at 1123 K. To reduce the interface degradation of thermal nitridation process, a low temperature process (623 K) for nitrogen incorporation in hafnia gate dielectric has been proposed. This method is based on post-deposition nitridation under ultraviolet light illuminated NH3 ambience. Uniformity of nitrogen distribution in the film was measured. Moreover, the amount of nitrogen incorporated by this process was comparable to that of high temperature thermal nitridation, maintaining low interface roughness (0.3 nm).;An evaluation of Ti based gate metals has been reported. The effective metal work function were 4.27, 4.56 and 5.08 eV for Ti, TiN and TiB2 , respectively. Regardless of gate electrodes, the conduction mechanism of the samples fitted with Poole-Frenkel model which is related to oxygen vacancies in the film. Ti gate electrode was found to be more favorable for NMOS device and TiB2 gate electrode can be used for PMOS. Further research for thermal stability of TiB2 gate electrodes was conducted. The extracted effective metal work function for TiB2 gate was about 5.08 eV. The work function showed almost identical values and sharp interface between metal and dielectric was confirmed after post deposition annealing by 1273 K. The work function lowering (4.91 eV) at 1373 K was caused by metal-dielectric intermixing and oxygen vacancy formation. TiB2 gate electrode was found to be suitable for use in PMOS device.;Finally, Uniaxial-mechanical-strain altered gate leakage current and dielectric constant of MOS device are measured. Uniaxial stress is applied using four-point wafer bending along one zero plane direction. The gate leakage current and dielectric constant are found to increase by up to 2% under tensile and compressive stress direction.