A scalable BSIM3v3 RF model for multi-finger NMOSFETs with ring substrate contact

We propose a scalable RF subcircuit FET model using BSIM3v3 by adding one of BSIM4´s Intrinsic Input Resistance (IIR) models (rgateMod=3) for S₁₁ scalability as well as a simple RC substrate network with well defined intrinsic FET´s parasitic estimation including partitioned junction diodes for S₂₂ scalability. Using this simple model, we could achieve a reasonable scalability with variations of L, W, V_GS, and V_DS for S₁₁ up to 25 GHz. We also suggest new S-parameter test structure for FETs with Ring Substrate Contact (RSC). This new layout scheme allows for improved S₂₂ scalability up to about 10 GHz; as well as reduces the punch through effect in DC I-V characteristic of large width NFETs. In addition, comparing to NFETs without RSC, we also report substantial R_sub lowering, FT and NF_min worsening, and C_sub influence on S₂₂ contours for NFETs with RSC in detail.