(266e) Multiscale Computational Fluid Dynamics: Methodology and Application to Film Microstructure Control in PECVD
Motivated by the above considerations, a novel, multiscale modeling strategy is developed which allows for the concurrent simulation of both the macroscopic gas phase and the microscopic surface interactions that contribute to thin film growth, and is applied to a common manufacturing problem of drift in the thin film product thickness caused by fouling during the conditioning phase of reactor operation . In a previous publication, a detailed kinetic Monte Carlo (kMC) algorithm was developed which has been shown to accurately reproduce thin film growth rates and surface morphologies at four distinct locations across the wafer surface . In this work, we propose the addition of a computational fluid dynamics (CFD) model that can account for the complex geometry of the PECVD reactor allowing for the prediction of accurate plasma flow fields and chemistry which are required within the microscopic kMC domain. Furthermore, parallel computation is introduced through the use of the message passing interface (MPI) framework, which has made possible the simultaneous simulation of numerous reactor zones with far increased lattice dimensions. Specifically, the parallel-plate PECVD reactor of interest in this work is divided into ten discrete, radial zones, each of which interacts with both of their neighboring zones, as well as the process gas (i.e., plasma) flowing over the wafer surface. Although open-loop simulations reveal significant variability in the film thickness across the wafer surface and between successive batch deposition sequences , the multiscale model developed in this work demonstrates that through the use of a carefully designed exponentially weighted moving average (EWMA) algorithm, the offset in the product thickness can be reduced to <1% within 10 batches of reactor operation. Additionally, the run-to-run control strategy is shown to recover the desired product thickness (i.e., return to the thin film thickness set-point of 300 nm) in the presence of disturbances in the plasma quality caused by fluctuations in the radio frequency (RF) power and feed gas composition.
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