Study of High- $k$ /Metal-Gate Work Function Variation in FinFET: The Modified RGG Concept

Because the existing ratio of average grain size to gate area (RGG) method is not applicable for calculating the work function variation (WFV) in nonplanar device structures, a modified RGG method is used to quantitatively estimate the WFV in a high-k/metal-gate (HK/MG) FinFET. A plot of the calculated WFV against the RGG for the FinFET with a TiN gate-stack is validated by previous simulation results. The standard deviation of the WFV, σ(WFV), of the nonplanar multigate device structure (e.g., the FinFET) is lower than that of a planar device structure by ~30%.