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 (phiTiN) slightly decreases with increasing nitrogen (N2) gas flow ratio, RN=N2/(Ar+N2) in the sputtering, from 17% to 100%. The experimental threshold voltage (Vth) dependence on the RNshows that the more RNoffers the lower Vthfor the TiN gate n-channel FinFETs. The composition analysis of the TiN films with different RNshowed that the more amount of nitrogen is introduced into the TiN films with increasing RN, which suggests that the lowering of phiTiNwith increasing RNshould be related to the increase in nitrogen concentration in the TiN film. The desirable Vthshift 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