Modeling electromigration as a fluid–gas system

In this paper two problems in modeling electromigration are addressed. The first problem is an issue of principle concerning counting the number of variables and the number of equations for formulating a well-posed mathematical problem. The second problem deals with setting up a system of equations which are sufficiently detailed for performing computer simulations of the local dynamics governing electromigration phenomena, and which also keep the CPU consumption within acceptable limits. A model for electromigration, which is based on a fluid–gas picture for the material transport, is proposed for dealing with both questions. The flow of matter is described as a combined flow of lattice sites and a flow of vacancies. The gas component is used to describe the vacancy flux.