Improved automatic differentiation method for efficient model compiler

The growing complexity of semiconductor devices presents a serious challenge to model developers. Compact device model compilers have been developed over the years to address this challenge. However, those compilers cannot generate very computationally efficient device models. In this paper, we present several effective techniques to improve the automatic differentiation method of model compiler MCAST so that it can generate very efficient device models. Those techniques include function strength reduction, minimum division, minimum function calls, and hierarchical automatic differentiation. Experimental results in modeling industry level semiconductor devices such as BSIM3, BSIM4 and B3SOI, demonstrated that the presented techniques lead to very computationally efficient models that are comparable to manually tuned ones