Impact of Nitrogen Incorporation on Low-Frequency Noise of Polycrystalline Silicon/TiN/HfO2/SiO2 Gate-Stack Metal--Oxide--Semiconductor Field-Effect Transistors

The impact of nitrogen incorporation into HfO 2 /SiO 2 gate dielectrics in the gate-stack fabrication process on the low-frequency noise of the drain current of polycrystalline silicon (poly-Si)/TiN (10 nm)/HfO 2 /SiO 2 gate-stack metal--oxide--semiconductor field-effect transistors (MOSFETs) is studied, considering the scaling of an equivalent oxide thickness with the reduction in interfacial layer SiO 2 thickness and the plasma nitriding of gate dielectrics. The nitriding combined with nitrogen plasma and nitrogen diffusion from a 10-nm-thick TiN layer increases the normalized noise power spectral density owing to carrier mobility fluctuation, and decreases the slope $\gamma$ of the $1/f^{\gamma}$ noise spectrum owing to the increase in the number of trapped carriers at the bulk trap site in the gate dielectric layer. The reduction in SiO 2 thickness from 1.5 to 0.8 nm showed less impact on the mentioned phenomena with TiN. These results suggest that nitrogen incorporation into HfO 2 /SiO 2 gate dielectrics in the device fabrication process for poly-Si/metal nitride/HfO 2 /SiO 2 gate stacks requires careful attention to suppress the power density of low-frequency noise.