Numerical Simulations of Topographic Evolution for Sputter Deposition into Trenches and Vias

Abstract

AbstractWe have performed 2D and quasi-3D numerical simulations of physical vapor deposition (PVD) into high aspect ratio trenches and vias used for modem VLSI interconnects. The topographic evolution is modeled using (continuum) level set methods. The level set approach is a powerful computational technique for accurately tracking moving interfaces or boundaries, where the advancing front is embedded as the zero level set (isosurface) of a higher dimensional mathematical function. First, we study the 2D case of long rectangular trenches including 3D out-of-plane target flux. The 3D flux is obtained from molecular dynamics computations for AI(100), and hence our approach represents a hybrid atomistic/continuum model. We obtain good agreement with X-TEM data. Secondly, we report results of axisymmetric 3D simulations of high aspect ratio vias which we then go on to compare with experimental data for Ti/TiN barrier layers. We find that the simulation data (using the cosine angular distribution) overpredict bottom coverage in some cases by approximately 20%-30% for both collimated and uncollimated deposition but in other cases provide a reasonably accurate comparison with experiment.