Principles of substrate crosstalk generation in CMOS circuits

Substrate noise injection is evaluated for a 0.25-mu m CMOS technology, to determine the mechanisms that contribute to substrate crosstalk. At the tra nsistor level, we find that impact ionization current and capacitive coupli ng from the junctions are the most significant contributors to substrate cu rrent injection. An investigation of substrate fluctuations at a circuit le vel included switching transients, capacitive damping, and separate substra te biasing. This investigation revealed that voltage transients on power-su pply lines can be the dominant source of substrate fluctuations. Finally, a statistical analysis of signal cancellation in an integrated circuit was p erformed. The results indicate that more cancellation will take place for t he high-frequency noise components than for the average and low-frequency c omponents. As a consequence, the dc and low-frequency components of the tra nsient that results from an individual switching event can not be neglected even if they are a relatively small fraction of the single transient.