Plasma sources capacitively driven at very high frequencies (VHF, e.g.
100MHz) have attracted much interest for semiconductor device fabrication.
These sources have the advantage of high efficiency plasma generation since
power couples efficiently with electrons and with lower ion energy loss
through sheath acceleration. This is beneficial for processes requiring
reduced ion energy, high ion and radical flux. At the same time, spatial
variations in plasma density and sheath voltage can arise leading to
non-uniformities at the wafer. The root cause of VHF plasma non-uniformity
is related to both electromagnetic wave and sheath coupling effects.
Unfortunately, most previous plasma fluid models that include
electromagnetic wave effects have found it challenging to simulate this
physics. Predictive models that can capture these effects are important for
plasma properties and their uniformity in industrial systems. We have
recently developed approaches that have succeeded in reproducing how VHF
power influences plasma uniformity by hybridizing electrostatic and
electromagnetic power delivery in a plasma fluid model with no loss of
self-consistency. These simulations also demonstrate how low frequency added
to VHF impacts uniformity through a sheath-wave interaction mechanism.
Accurate predictions of the Ion Energy and Angular Distributions (IEADFs), are essential for a range of critical applications in thin films deposition and etching. Ion generation and flux is determined by ionization rates that depend on reactor-level parameters. Ion energy and angle depends on the acceleration of the ions across the sheath, driven by potential differences governed by the spatial plasma distribution. The IEADF at the wafer surface sensitively depends on rare collisional events such as charge exchange and ion-neutral collisions during the ion’s transit across the sheath. Using ion transport parameters computed using standard fluid modeling techniques can significantly misrepresent the actual IEADFs at surfaces. In this study we use a hybrid approach where we employ VizGlow, a fluid based plasma solver, to simulate a (pulsed) Inductively Coupled Plasma (ICP) source with a (pulsed) RF bias. Then we use VizGrain, a companion particle solver, to compute the IEADFs using the test-particle approach. We study the effect of pressure, pulse width and duty cycle and the staggering of the source and bias pulsing cycles on the IEADFs using Argon plama. We compare the simulation results to measurements of IEADFs on a test plasma platform for validation purposes.
Esgee Technologies gave a talk on “High-Fidelity Modeling of Spark Plug Ignition and Erosion” at the VERIFI workshop on Ignition for Internal Combustion Engines during July 27-28, at the Argonne National Lab in Chicago, Illinois. The talk focused on recent developments for modelling spark ignition kernels using a fully coupled plasma ignition model and a modelling approach for simulating lifetime erosion of spark plugs using an arc plasma model.
Ignition kernel in cross-flow with arc channel and iso-octane fuel-air mass fraction. The arc physics and combustion ignition kinetics are solved simultaneously in a fully coupled manner.
Esgee Technologies will present “High-Fidelity Numerical Modeling of Spark Plug Erosion” at the SAE International World Congress Experience 2019, April 9-11, at the Cobo Center in Detroit, Michigan.
Abstract
Spark plug erosion is critical in determining the overall efficiency of a spark ignition engine. Over its lifetime, a spark plug is subject to millions of firings. Each spark event results in material erosion due to several mechanisms such as melting, vaporization, sputtering and oxidation. With electrode wear, the inter-electrode spacing increases and a larger voltage difference is required to initiate the spark. The probability of engine misfires also increases with electrode erosion. Once a critical gap is reached, the energy in the ignition coil is not enough to cause a spark breakdown, and the spark plug must be replaced. Due to the long relevant time scales over which erosion occurs, and the difficulty of analyzing the spark plug environment during operation, determining spark plug lifetime typically requires extensive field testing. A high fidelity commercial thermal plasma solver, VizSpark is used simulate electrode erosion due to spark events. The model preserves key arc physics such as current conservation, conjugate heat transfer, fluid flow and electrode ablation. The solution framework includes the capability of coupling high fidelity arc physics with a dynamically deforming spark-plug electrode. A phenomenological model for electrode erosion based on energy is derived from prior experimental work on single-pulse electrode erosion. The energy-based electrode erode model is validated against experimental results, and 3-D electrode erosion simulations in stationary and cross-flow were performed.
There has been an increased interest in understanding the initial stages of flame kernel formation in internal combustion engines as it offers a potential way of improving their thermal efficiency. For spark-ignited engines, the dynamics that govern the initial spark and its transition into a flame kernel play an important role in determining the overall engine efficiency. In this regard, this paper presents a computational model developed to simulate a spark discharge formed in a premixed fuel air mixture. Additionally, by simultaneously modeling the reactive fluid dynamics that governs combustion with the electromagnetics that governs the spark, the overall objective of this paper is to consistently simulate spark-initiated combustion in a premixed fuel-air mixture. Two different fuel-oxidizer mixtures are considered in this study, hydrogen-oxygen and methane-oxygen. Key mechanisms via which the spark channel ignites the mixture are identified and studied in detail.
Sample Results
Temperature kernel evolution during spark ignition
Water concentration evolution during spark ignition
Esgee Technologies Inc. is excited to announce the production release of OverViz Simulation Suite v2.3. Our latest version of industry leading plasma-fluid-electromagnetic-particle simulation software provides significant performance improvements over previous versions, along with many new features and enhancements.
Users can expect significant improvements in solver run time compared to the previous version for many simulation applications. The plot above shows 3x-5x improvement for our standard CCP, ICP, and MWP examples and up to 8x for some electromagnetic simulations. Note that the performance improvement strongly depends on the application, mesh size, selected physics, chemistry, and computing hardware.
Esgee is excited to introduce ChemView, our new user interface for editing and visualizing chemistry mechanisms. ChemView is designed to improve user experience in working with chemical reaction mechanisms. It simplifies the process of editing, adding, and deleting reactions and their parameters. ChemView allows user to quickly enable/disable reactions, visualize and compare reaction parameters (e.g. rate coefficients), and easily export for use in plasma simulation.
A new reactive flow modeling capability is now available in VizSpark. Users can simulate spark ignited combustion, with full coupling to the arc physics.
New hybrid plasma modeling is now available in the OverViz Suite in which any species can be freely set as fluid or particle. In the hall thruster example above, the electrons are solved as fluid and other species (Xe, Xe+, and Xe++) are solved as particles.
Below is a list of additional new features and enhancements that can be found in v2.3:
More robust electrostatic potential solver
New single-seat Unlimited Parallel (UP) licensing option
Enhanced Particle-in-Cell (PIC) and hybrid fluid-particle plasma modeling
Tecplot outputs now use TecIO binary formatting for efficient post processing
Monte Carlo Collision (MCC) modeling with charge exchange and fast neutral particle treatment
Improved coupled circuit solver in VizGlow
Particle boundary emission in VizGrain
Improved magnetized plasma solver
CUF support for VizGrain inflow boundaries
User interface simplifications and enhancements
VizGrain particle charge-exchange reactions
Nonlinear magnet model for 2D transverse electric polarization in VizGlow
2D no electric polarization option for electromagnetic waves in VizGlow
Support IEDFs from CUP for VizGrain inflow boundaries
Current driven boundary condition for ICP electromagnetics
Ability to write EADF data to multiple transient output files in VizGlow
Define spatially dependent reaction rate multiplier for specified reactions in VizGlow
Simplified VizFlow UI panel
New quasineutral sheath boundary condition options
Improved particle parallel simulation efficiency
Ability to specify different statistical weights for individual species in VizGrain
Many new and improved simulation examples were added for all OverViz physics modules.
New installers and installation instructions are available for download from the Esgee Corporate Portal. Please contact us if you have any questions, need help accessing the Portal, or are interested in learning more about v2.3.
