In order to calibrate an RSM with measured data from a fabrication unit, not only its control and response variables have to be accessible, but also internal parameters of the RSM need to be accessible. For this purpose, the RSM EVE class provides access to the coefficients of the RSM in terms of names that are constructed from the control variables they are attached to. For example, when modeling the threshold voltage (vth) as a function of the gate length (lg) and the threshold adjust implant dose (dose) with a polynomial model of second order, possible control names would be c-lg-2, c-lg-dose, c-dose-2, and c-vth-0. If a conflict arises with names already used as control or response variable names of the model, these standard assignments can be overwritten.
Fitting the coefficients of a RSM to experimental data is a powerful method for modeling the overall behavior of a fabrication process [Mas95].