A new lossy substrate model for accurate RF CMOS noise extraction and simulation with frequency and bias dependence

A lossy substrate model is developed to accurately simulate the measured RF noise of 80-nm super-100-GHz [f.sub.T] n-MOSFETs. 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 noise parameters before deembedding proves the lossy substrate model. The intrinsic RF noise can be extracted easily and precisely by the lossy substrate deembedding using circuit simulation. The accuracy has been justified by good agreement in terms of [I.sub.d], [g.sub.m], Y-parameters, and [f.sub.T] under a wide range of bias conditions and operating frequencies. Both channel thermal noise and resistance induced excess noises have been implemented in simulation. A white noise [gamma] factor extracted to be higher than 2/3 accounts for the velocity saturation and channel length modulation effects. The extracted intrinsic [NF.sub.min] as low as 0.6-0.7 dB at 10 GHz indicates the advantages of super-100 GHz [f.sub.T] offered by the sub-100-nm multifinger n-MOSFETs. The frequency dependence of noise resistance [R.sub.n] suggests the bulk RC coupling induced excess channel thermal noise apparent in 1-10-GHz regime. The study provides useful guideline for low noise and low power design by using sub-100-nm RF CMOS technology. Index Terms--Lossy substrate, noise, RF CMOS, RLC network.