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