TCAD study of back-gate biasing in UTBB

We have shown here a comprehensive set of results on the coupling factor in a UTBB technology based on TCAD simulation. An interesting result is the degree to which the coupling factor is not constant across the possible realistic range of biases, and that not only back-gate depletion may play a role, but fixed charges and work function variation change the behavior. This suggests that these dependencies may be used to characterize those important variables, and also indicates that use of the back-gate in circuit operation must take into account the variation in coupling factor across the practical operating range.