Nitrogen Gas Flow Ratio and Rapid Thermal Annealing Temperature Dependences of Sputtered Titanium Nitride Gate Work Function and Their Effect on Device Characteristics

A sputtered titanium nitride (TiN) metal gate has systematically been investigated, and the dependences of TiN work function (TiN) and device performance on nitrogen gas flow ratio [RN=N2/(N2+Ar)] in sputtering and rapid thermal annealing (RTA) temperature (TR) are clarified. It is experimentally found that TiN slightly decreases from 4.87 to 4.78 eV with increasing RN from 17 to 83%, and it markedly decreases with increasing TR. The analysis of the electrical characteristics of fabricated metal–oxide–semiconductor field-effect transistors (MOSFETs) shows that the optimal RN range is 17–50%, and a higher RN offers a lower Vth owing to the lower TiN. The origin of TiN decrease with increasing RN and TR is discussed. The obtained results indicate that TiN can be controlled by sputtering and RTA conditions, and are very useful for setting the appropriate Vth for lightly doped channel devices such as a FinFET.