Authors: Y. Ma, M-C Jeng and Z. Liu
Affilation: Cadence Design System, Inc., United States
Pages: 645 - 648
Keywords: SOI, substrate current, Model
Two competing factors affect the body bias dependence of substrate current in SOI devices. One is through drain current. The other is through electric field in channel near drain side. It is shown that with the increase of body voltage, threshold voltage of the device decreases, so the total drain current is increased. Therefore, substrate current caused by impact ionization is also increased. This causes negative resistance of body current with respect with body voltage, which is a potential issue during circuit simulation to cause convergence problem with BsimSOI model. On the other hand, increased body bias also decreases the electric field near drain region, which causes the decreasing of substrate current. The current available model in BsimSOI is used to demonstrate the two competing factors. It is concluded that a good modeling approach including both factors and model parameter extraction methodology are important to accurately characterize substrate current body bias dependence.