Presentation Title

Run-to-Run Control of Film Thickness in PECVD: Application to a Multiscale CFD Model of Amorphous Silicon Deposition

Faculty Mentor

Panagiotis D. Christofides

Start Date

18-11-2017 10:00 AM

End Date

18-11-2017 11:00 AM

Location

BSC-Ursa Minor 74

Session

Poster 1

Type of Presentation

Poster

Subject Area

engineering_computer_science

Abstract

Uniform deposition of thin film layers remains a challenge in silicon processing industries due to the lack of in situ measurements and drift in the plasma composition caused by fouling. Past research has shown that a run-to-run (R2R) control scheme applied to first principles modeling of gas phase flow reduces the offset in film thickness from 5% to 1%. However, recent advances of parallel computation motivate the application of computational fluid dynamics (CFD) to gas phase simulation for improved modeling accuracy. Consequently, we propose the application of R2R control strategy to the simulated deposition of amorphous silicon (a-Si:H) thin films using a transient, multiscale CFD model. Steady-state simulation has shown that a two-dimensional asymmetrical model is able to accurately capture the complex behavior of the PECVD reactor and to reproduce experimentally observed non-uniformities with respect to the film thickness and porosity. The R2R control strategy is applied to this model with a parallel computation scheme by updating the local temperature profile batch by batch. Growth rate functions are pre-determined by transient modeling at certain temperatures. For microscopic modeling, ten independent simulations are conducted corresponding to various radial positions on the wafer substrate. For each simulation, a hybrid kinetic Monte Carlo (kMC) method is applied to account for the complex surface interactions pertaining to thin-film growth, and to capture the heat and mass exchange accompanying a-Si:H deposition. The result shows that product offset from the desired thin-film thickness may be reduced to <1% for zones within a 7 cm radius, while the non-uniformity in the remaining reactor zones is minimized with respect to the limitations on operating temperature (i.e., within 100 K of the nominal operating conditions).

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Nov 18th, 10:00 AM Nov 18th, 11:00 AM

Run-to-Run Control of Film Thickness in PECVD: Application to a Multiscale CFD Model of Amorphous Silicon Deposition

BSC-Ursa Minor 74

Uniform deposition of thin film layers remains a challenge in silicon processing industries due to the lack of in situ measurements and drift in the plasma composition caused by fouling. Past research has shown that a run-to-run (R2R) control scheme applied to first principles modeling of gas phase flow reduces the offset in film thickness from 5% to 1%. However, recent advances of parallel computation motivate the application of computational fluid dynamics (CFD) to gas phase simulation for improved modeling accuracy. Consequently, we propose the application of R2R control strategy to the simulated deposition of amorphous silicon (a-Si:H) thin films using a transient, multiscale CFD model. Steady-state simulation has shown that a two-dimensional asymmetrical model is able to accurately capture the complex behavior of the PECVD reactor and to reproduce experimentally observed non-uniformities with respect to the film thickness and porosity. The R2R control strategy is applied to this model with a parallel computation scheme by updating the local temperature profile batch by batch. Growth rate functions are pre-determined by transient modeling at certain temperatures. For microscopic modeling, ten independent simulations are conducted corresponding to various radial positions on the wafer substrate. For each simulation, a hybrid kinetic Monte Carlo (kMC) method is applied to account for the complex surface interactions pertaining to thin-film growth, and to capture the heat and mass exchange accompanying a-Si:H deposition. The result shows that product offset from the desired thin-film thickness may be reduced to <1% for zones within a 7 cm radius, while the non-uniformity in the remaining reactor zones is minimized with respect to the limitations on operating temperature (i.e., within 100 K of the nominal operating conditions).