Investigation of the TiN Gate Electrode With Tunable Work Function and Its Application for FinFET Fabrication

The titanium nitride (TiN) gate electrode with a tunable work function has successfully been deposited on the sidewalls of upstanding Si-fin channels of FinFETs by using a conventional reactive sputtering. It was found that the work function of the TiN (phi _TiN ) slightly decreases with increasing nitrogen (N ₂ ) gas flow ratio, R _N =N ₂ /(Ar+N ₂ ) in the sputtering, from 17% to 100%. The experimental threshold voltage (V _th ) dependence on the R _N shows that the more R _N offers the lower V _th for the TiN gate n-channel FinFETs. The composition analysis of the TiN films with different R _N showed that the more amount of nitrogen is introduced into the TiN films with increasing R _N , which suggests that the lowering of phi _TiN with increasing R _N should be related to the increase in nitrogen concentration in the TiN film. The desirable V _th shift from -0.22 to 0.22 V was experimentally confirmed by fabricating n ⁺ poly-Si and TiN gate n-channel multi-FinFETs without a channel doping. The developed simple technique for the conformal TiN deposition on the sidewalls of Si-fin channels is very attractive to the TiN gate FinFET fabrication