Regulation of film thickness, surface roughness and porosity in thin film growth usingdeposition rate

摘要

This work focuses on distributed control of film thickness, surface roughness and porosity in a porousthin film deposition process using the deposition rate as the manipulated input. The deposition processincludes adsorption and migration processes and it is modeled via kinetic Monte Carlo simulation ona triangular lattice with vacancies and overhangs allowed to develop inside the film. A distributed pa-rameter (partial differential equation) dynamic model is derived to describe the evolution of the surfaceheight profile of the thin film accounting for the effect of deposition rate. The dynamics of film porosity,evaluated as film site occupancy ratio, are described by an ordinary differential equation. The developeddynamic models are then used as the basis for the design of a model predictive control algorithm thatincludes penalty on the deviation of film thickness, surface roughness and film porosity from their respec-tive set-point values. Simulation results demonstrate the applicability and effectiveness of the proposedmodeling and control approach in the context of the deposition process under consideration.