SIMULATION OF SEMICONDUCTOR DEVICES AND PROCESSES Vol. 4 Edited by W. Fichtner, D. Aemmer - Zurich (Switzerland) September 12-14,1991 - Hartung-Gorre Efficient Simulation of Impurity Segregation during Oxidation of Arbitrarily Shaped Multi-Layers Structures. Dominique Collard, Bruno Baccus, and Emmanuel Dubois ISEN, 41 Boulevard VAUBAN, 59046 LILLE Cedex, FRANCE. Abstract For the multi-layers process simulation, a large flexibility is needed in the mesh generation, specially to ensure a good convergence in stress dependent oxidation modeling. This paper presents an efficient numerical treatment for the solution of dopant redistribution and segregation when the mesh is completely re-generated at each oxidation step. To be applied on up-to-date silicon technologies, the two-dimensional (2D) process simulators have to solve the impurity diffusion in all the present layers. Moreover, in order to ensure a good convergence in stress dependent oxidation modeling, a large flexibility is required for the oxide mesh generation. In this case , the moving boundary problem complicates the numerical treatment of dopant redistribution and segregation, specially in the cases of complex geometrical structures. An efficient numerical procedure has been proposed for ID simulation [1], but its extension to 2D [2] requires a arduous numerical treatment and may lead to very large discretization point numbers. This paper proposes a new and simple method, based on the finite element method, that efficiently solves the impurity diffusion and segregation even in the case of arbitrarily designed meshes needed for stress effects analysis in oxidation simulation. 1 Numerical procedure A triangular mesh is generated, using Delaunay criterion for the complete structure [3]. The same grid is used for the numerical oxidation simulation (oxidant diffusion and elasticity equations) and for the impurity diffusion. Fig. 1 shows a typical mesh used for this application. For each oxidation incremental step, the following procedure is performed: a) The interface and surface nodes motion is calculated from oxidant diffusion and elastic displacements. b) The lost impurity quantity, Q s , due to the interface motion is calculated for each oxidized layer (silicon and polysilicon). Q s , depicted infig.2(a),is calculated by an integration along the interface using the concentration and the concentration spatial derivatives in the oxidation direction given by the finite element shape function.