AGC Plasma Technology Solutions develops and industrializes novel plasma coating technologies - both for the internal needs of AGC and for external partners. The company provides complete support for transferring coating technologies from the R&D scale to the mass production scale.
The group of prof. Stephane Lucas at the Université de Namur is an internationally renowned team with many competences - development of new materials, material characterization or plasma diagnostics. The competence most relevant to this project is their ability of film growth simulation.
AGC has developed a highly innovative PECVD coating technology called PlasmaMAX™ which is based on the hollow cathode plasma. It has been demonstrated that the PECVD method produces high-purity SiO2, TiO2, ZnO, Al2O3 or DLC coatings at deposition rate over 10x higher than conventional (sputtering-based) processes.
The aim of the project is to develop a multi-scale simulation toolbox capable of predicting the behavior of the PECVD process as well as material properties, only based on the coater settings.
PlasmaSolve and Université de Namur are assisting AGC Plasma with finding answers to these questions. Their joint efforts have also been supported by the M-era.net international grant called MIST.
Results and Benefits
The project yielded several benefits to all the three partners involved in it:
AGC was provided with scaling laws and concrete recommendations for up- and down- scaling the technology.
AGC validated its hypotheses about flow distribution and plasma uniformity. Wherever possible, suggestions for improvement were given.
PlasmaSolve implemented new simulation tools for PECVD system and process simulation into its MatSight software.
Université de Namur upgraded its software Virtual Coater™ by improving its film growth simulation model NASCAM™ (NanoSCale Modeling)
Gas flow visualized in AGC's hollow cathode system. Some components have been hidden to protect sensitive IP.
The project was based on a rather ambitious simulation concept - it benefits from the fact that PlasmaSolve has extensive experience with process-level simulation while Université de Namur possesses unique film-growth simulation tools.
These tools are perfectly complementary - PlasmaSolve's software can simulate plasma distribution, gas flow distribution, even densities of various species created in the plasma. However, it does not include detailed treatment of surface chemical processes or diffusion effects at the coated surfaces.
On the contrary, the composition and structure of coatings can be predicted using the NASCAM™ software from Université de Namur. This software, in turn, requires inputs from process models - species densities and fluences.
When combined, the tools of PlasmaSolve and Université de Namur enabled prediction of coating properties based on the PECVD coater settings.
Plasma Distribution Evaluation
Understanding the plasma distribution is important because it affects the flux of ions to the surface. The flux of ions, in turn, influences the density and compactness of the resulting coating.
The plasma distribution and composition generally changes with
Gas pressure and gas flow rate
Distance between the electrode and substrate
All of these dependencies and trends were captured using a 2D plasma model.
Gas Flow Simulations
The pressure in the PECVD system varies accross several orders of magnitude - from 100 Pa to a little under 1 Pa. For gas flow simulation, this presents certain challenges because there are two methods one could use - neither of them being a perfect fit.
The DSMC (direct-simulation Monte-Carlo) method would be warranted due to the low pressure limit where the flow stops to follow the rules of the continuum. However, it is computationally unfeasible at the higher pressures, above 10 Pa.
A compressible fluid simulation with slip boundary conditions is about 200x more computationally efficient compared to DSMC, but its accuracy in the low pressure region is unknown.
For that reason, PlasmaSolve simulated an AGC coater using both the types of models and validated them against pressure readings on two distinct locations in the low pressure region.
The study revealed that the fluid simulation is very well applicable to a glass-coating PECVD reactor and both the simulation techniques showed matched the measurement very well.
The validated code was then used for several engineering studies, typically pertaining to gas flow uniformity.
Benchmarking flow simulation with measurements
Chemical composition of plasma as a function of time - only the 10 most abundant reactive neutrals and 10 most abundant positive ions are shown.
Understanding the Chemistry
The plasma-phase chemistry of the precursor - TMDSO (tetramethyldisiloxane) was previously unknown. PlasmaSolve worked with a tremendouns number of literature resources to formulate a complete plasma-kinetic system for this complex compound. The resulting system contains nearly 70 species and over 1200 plasma-chemical reactions.
The scheme was migrated into PlasmaSolve's Global Plasma Model, which is a computationally efficient tool describing the plasma in a volume-averaged approximation but with all the possible chemical processes that could take place.
Once this respectable task is completed, the Global Plasma Model can be used for
Discovering favorable reaction pathways in the system.
Adjusting coater settings to favor a concrete reaction pathway.
Providing necessary input into film-growth simulations
Modeling the film growth
The modeling of the film growth based on the results of the Global Plasma Model was made possible by an improvement of the NASCAM™ package of the software Virtual Coater™ developed by UNamur and sold by Innovative Coating Solutions (ICS).
More than 60 surface chemical reactions between condensing species were introduced into the model, whose reaction probabilities were evaluated by DFT. This enhancement, together with the capabilities already built into NASCAM, were used to determine the chemical composition, density and morphology of coatings as a function of discharge parameters and the amounts of HMDSO/TMDSO and oxygen injected into the discharge.
A detailed parametric study was carried out to determine the best settings to obtain a pure SiO2 film.
This improvement is now available and operational for any type of monomer injected into discharges with similar characteristics.
(a) Example of reaction occurring at the sample surface:
(b) Film growth for 1 coater setup
(c) 3D parametric scan to predict the film composition