Effect of nitridation on low-frequency (1/f) noise in n- and p-MOSFETS with HFO₂ gate dielectrics

The nitridation effects on low-frequency (1/f) noise in metallorganic chemical vapor deposited HfO₂ n- and p-metal oxide-semiconductor field effect transistors (MOSFETs) are reported. Devices with a postdeposition anneal (PDA), performed after HfO₂ deposition, in a N₂ or NH₃ ambient were investigated. A significant variation in noise was observed when different PDAs were employed. Devices annealed with N₂ showed lower input referred noise S_VG (∼ 125 μV ²/Hz) for |V_G-V_T| ∼ 0.1 V, close to the ITRS specifications when compared to NH₃ anneals (∼ 1100 μV²/Hz). Carrier trapping is shown to be the origin of the 1/f fluctuations for most n-MOSFET process splits. For p-MOSFETs, no significant impact of the PDA was observed, yielding a constant S_VG (∼ 200 μV²/Hz). Additionally, two types of interfacial layers were considered for n-MOSFETs, i.e., nitrided and non-nitrided interfaces, prepared by a decoupled plasma nitridation before HfO₂ deposition. Different trap density profiles were derived from the noise spectra for the nitrided- and non-nitrided-interface n-MOSFETs. This suggests that nitridation can induce nitrogen-related defects which lead to a variation in the concentration of oxygen vacancies in the bulk HfO₂. The binding configuration between the atoms may also play an important role.