A Comparative Study of Nitrogen Gas Flow Ratio Dependence on the Electrical Characteristics of Sputtered Titanium Nitride Gate Bulk Planar Metal–Oxide–Semiconductor Field-Effect Transistors and Fin-Type Metal–Oxide–Semiconductor Field-Effect Transistors

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Sputtered titanium nitride (TiN) metal gates fabricated at different nitrogen gas flow ratios [$R_{\text{N}}=\text{N$_{2}$}/(\text{N$_{2}$}+\text{Ar})$] from 17 to 100% have systematically been investigated, and the $R_{\text{N}}$ dependence on the electrical characteristics of fabricated TiN metal gate bulk planar metal–oxide–semiconductor field-effect transistors (MOSFETs) and fin-type MOSFETs (FinFETs) are clarified. It is experimentally found that the electrical characteristics of FinFETs such as subthreshold slope (S-slope) and mobility are almost independent of $R_{\text{N}}$, while those of bulk planar MOSFETs markedly deteriorate with increasing $R_{\text{N}}$. These experimental results are discussed from the viewpoint of the device structure differences and the direction of energetic nitrogen atoms in sputtering. The threshold voltage ($V_{\text{th}}$) of FinFETs can be adjusted to about 100 mV by controlling $R_{\text{N}}$ without device performance degradation. These results are very useful in setting an appropriate $V_{\text{th}}$ for TiN gate-last FinFETs.
2009-05-25