A lossy substrate model for sub-100 nm, super-100 GHz fT RF CMOS noise extraction and modeling

A lossy substrate model is developed to accurately simulate the measured RF noise of 80 nm, super-100 GHz f_T nMOSFETs. A substrate RLC network built in the model plays a key role responsible for the nonlinear frequency response of noise in 1∼18 GHz regime, which did not follow the typical thermal noise theory. Good match with the measured S-parameters, Y-parameters, and NF_min before de-embedding proves the lossy substrate model. The intrinsic RF noise can be extracted easily and precisely by the lossy substrate de-embedding using circuit simulation. The accuracy has been justified by good agreement in terms of I_d, g_m, Y-parameters, and f_T under a wide range of bias conditions and operating frequencies. The extracted intrinsic NF_min as low as 0.6∼0.7 dB at 10 GHz indicates the advantages of super-100 GHz f_T offered by the sub-100 nm multi-ringer nMOS. The frequency dependence of noise resistance R_n suggests the substrate RC coupling induced excess channel thermal noise apparent in 1∼10 GHz regime. The study provides a useful guideline for low noise and low power design by using sub-100 nm RF CMOS technology.