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

概要

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A sputtered titanium nitride (TiN) metal gate has systematically been investigated, and the dependences of TiN work function ($\phi_{\text{TiN}}$) and device performance on nitrogen gas flow ratio [$R_{\text{N}}=\text{N$_{2}$}/(\text{N$_{2}$}+\text{Ar})$] in sputtering and rapid thermal annealing (RTA) temperature ($T_{\text{R}}$) are clarified. It is experimentally found that $\phi_{\text{TiN}}$ slightly decreases from 4.87 to 4.78 eV with increasing $R_{\text{N}}$ from 17 to 83%, and it markedly decreases with increasing $T_{\text{R}}$. The analysis of the electrical characteristics of fabricated metal–oxide–semiconductor field-effect transistors (MOSFETs) shows that the optimal $R_{\text{N}}$ range is 17–50%, and a higher $R_{\text{N}}$ offers a lower $V_{\text{th}}$ owing to the lower $\phi_{\text{TiN}}$. The origin of $\phi_{\text{TiN}}$ decrease with increasing $R_{\text{N}}$ and $T_{\text{R}}$ is discussed. The obtained results indicate that $\phi_{\text{TiN}}$ can be controlled by sputtering and RTA conditions, and are very useful for setting the appropriate $V_{\text{th}}$ for lightly doped channel devices such as a FinFET.
2008-04-25