| Currently, there is an increasing need to improve semiconductor manufacturing process operation and yield. This need has arisen due to the increased complexity and density of devices on the wafer, which is the result of increased wafer size and smaller device dimensions. Within this manufacturing environment, thin film microstructure, including thin film surface roughness and amount of internal film defects, has emerged as an important film quality variable, which strongly influences the electrical and mechanical properties of micro-electronic devices. On one hand, surface roughness of thin films controls the interfacial layer and properties between two successively deposited films. On the other hand, the amount of internal defects, usually expressed as film porosity, plays an important role in determining the thin film microstructure. At this stage, previous research efforts have exclusively focused on control of thin film surface roughness and have not addressed the challenging issue of simultaneously regulating film surface roughness, porosity, and thickness while reducing run-to-run film variability.;This dissertation presents a unified and practical framework for modeling and control of film porosity, surface roughness, and thickness in thin film growth. Specifically, we will present novel definitions for describing film porosity, and stochastic modeling and parameter estimation techniques for constructing dynamic models for roughness, porosity, and film thickness. We will also present state/output feedback covariance control and model predictive control problem formulations and solutions which lead to a balanced trade-off in the closed-loop system between the three, possibly conflicting, control objectives of surface roughness, film thickness, and porosity regulation. The application of the proposed modeling and control methods to complex thin film deposition and sputtering processes will be discussed and simulation results will be shown to demonstrate the resulting closed-loop system performance and robustness. |
