A study of low-frequency noise on high-k/metal gate stacks with in situ SiOx interfacial layer

Low-frequency noise of HfO₂/TiN nMOSFETs with different SiO_x interfacial layer (IL) thicknesses is presented. It is observed that chemically formed thin ILs (0.4 nm, 0.45 nm and 0.5 nm) show a noise level close to a reference thermal IL(1 nm). This is shown to relate to the dominant contribution of the high-k HfO₂ traps in comparison to the IL traps. The average extracted values for effective trap densities in these wafers are N_t= 7×10¹⁸, 1×10¹⁹, 2×10¹⁹ and 4.8×10¹⁹ for thermal oxide, 0.5 nm, 0.45 nm and 0.4 nm chemical oxide wafers respectively.