Analysis of substrate noise propagation in a lightly doped substrate [mixed-signal ICs]

Analysis and simulation results of substrate noise in mixed-signal ICs on lightly doped substrates are difficult to bring in agreement with measurements, even for very simple structures. In this paper, substrate noise propagation in lightly doped p-type substrates is studied with a simple test structure. Our study reveals that the current flow is multi-dimensional, and that adjacent layout details (such as nwells and metal wires) influence the propagation between two contacts. The analysis has enabled its to match the measured S₂₁ propagation with a simulation model from DC (error<8%) up to 10 GHz with an overall error smaller than 3 dB. Insight in simple structures such as the one considered here, is valuable in improving the understanding of substrate noise in lightly doped substrates.