Modeling 3D effects of substrate topography on step coverage and film morphology of thin metal films

Abstract

This paper presents the use of three-dimensional (3D)-films to investigate 3D effects of microstructure and topography on the deposition of metal films over integrated circuit topography. 3D-films is a fully 3D thin film growth simulator which models both the evolution of the surface profile and the internal microstructure of the film. The simulator produces a detailed depiction of the film, including grain and columnar structure, and is capable of producing density and porosity information. This paper first presents the application of this simulator to specific problems posed by the sputter deposition of refractory metals as barriers and the filling of contacts and vias by electroplating of copper and CVD of tungsten. Specific problems addressed are step coverage over a variety of dual damascene topographies, the formation of notches and poor step coverage using directed sputtering and conformal filling of features. The program is used to address the ramifications of using geometric optimization of the via/contact geometry and the application of resputtering fluxes. Finally, issues concerning incomplete filling of dual damascene structures using CVD and plating are addressed. © 2002 Elsevier Science B.V. All rights reserved.