Simultaneous Regulation of Surface Roughness and Porosity in Thin Film Growth

Gangshi Hu,  Gerassimos Orkoulas,  Panagiotis Christofides
University of California, Los Angeles


Abstract

This work focuses on simultaneous control of surface roughness and film porosity in a porous thin film deposition process modeled via kinetic Monte Carlo simulation on a triangular lattice. The microscopic model of the thin film growth process includes adsorption and migration processes. Vacancies and overhangs are allowed inside the film for the purpose of modeling thin film porosity. Appropriate closed-form dynamic models are first derived to describe the evolution of film surface roughness and porosity and used as the basis for the design of a model predictive control algorithm that includes penalty on the deviation of surface roughness and film porosity from their respective set-point values. Closed-loop simulations demonstrate that when simultaneous control of surface roughness and porosity is carried out, a balanced trade-off is obtained in the closed-loop system between the two control objectives of surface roughness and porosity regulation.