Material removal modeling in chemical mechanical planarization using contact stress analysis

Chemical mechanical planarization (CMP) has emerged in the past decade as one of the corner stones of the manufacturing of semiconductor devices, and this fundamental role is even more critical since the development of copper damascene technology. CMP, as suggested by its name, is a mixed chemo-mechanical process, and is widely used to planarize metals and dielectrics in multi-level-metal interconnections (ICs) processes. It has expanded into an integral component of the design, development and integration of process modules necessary to manufacture and yield cost-effective leading-edge products. The purpose is to remove high areas on the wafer without affecting the low areas, thereby allowing the surface to become isotropic and planar, locally and globally.; Material removal mechanisms during CMP involve complex mechanical and chemical actions. In this research, it is assumed that the slurry, which contains nanoparticles suspended in an aqueous media, softens the wafer surface and transports the abrasive particles as well as the abraded material. The objective is to develop a model (that uses experimental results for calibration) to predict removal rates. We describe a physics-based mechanical material removal model based on contact stress analysis. The model includes abrasive wear by slurry particles, asperity and bulk pad deformations, compliant wafer and carrier film deformations, and fluid flow. The material removal rate on the wafer is computed as a function of position and the results are used to simulate the evolution in time of the surface of representative features. A variational approximation procedure for the contact stress analysis of an asperity and a feature is investigated.; As device sizes shrink and demands on chip performance increase, understanding the fundamental mechanisms involved in the CMP process will help industry meet the stringent requirements for manufacturing cutting edge ICs. Furthermore, process development could be faster and less expensive through the use of physics-based models and computer simulations. This thesis, by enabling a better understanding of the basic polishing mechanisms in CMP and by developing a comprehensive model for material removal that takes into account the micro and macroscopic nature of the CMP process, is a contribution towards these efforts.