Esgee Technologies will be presenting at this year’s Society of Automotive Engineers (SAE) WCX World Congress Experience held in Detroit, Michigan from April 5th to 7th. Our paper, “Modeling of Switching Characteristics of Hydrogen-Nitrogen Filled DC Contactor Under External Magnetic Field,” was chosen from hundreds of submissions to be featured at the event.
WCX is among the top annual gatherings which provides an intersectional forum between automotive engineers, researchers, scientists, and technical innovators. This year’s topics include EV technology and electrical infrastructure, energy storage and battery disposition, as well as design and safety for automated vehicles.
We sat down with Dr. Rakesh Ranjan, who will be presenting on behalf of EsgeeTech this year, in order to learn more about the applications for this research and how they align with the conference’s goals:
What applications are there for EV relay arcs? And why choose SAE to discuss them?
SAE is the biggest confluence of engineers dedicated to enhancing our mobility in an environmentally friendly manner. If you are excited about the prospect of buying a cleaner vehicle which won’t contribute to environmental pollution, it’s likely that the EV technologies behind it started as concepts presented at an SAE conference. Technologies for the future of mobility have their beginnings right here at SAE conferences.
As for EV relays, it is a critical component for the safety of electric vehicles. With increasing power needs for electric vehicles, there comes an increase in things like battery size and voltage levels required to drive vehicles. An increase in voltage means that electric isolation of safety-critical components would be delayed due to prolonged arcing. So, how safe your vehicle is could ultimately depend on how quickly the arc channel inside the EV relay quenches.
Perhaps it may not be the first feature that consumers think of when it comes to vehicle safety, but for manufacturers and anyone involved in future maintenance on the vehicle, arc-resistant equipment is key to creating a safe environment. For the owner of an electric vehicle, arc-quenching is also a means of decreasing or completely removing the risk of damage from arc flash events. That, of course, is desirable because it means lowered maintenance costs and higher longevity for critical automotive components.
What is the quick takeaway from your talk?
A one-minute synopsis of my talk would be about the use of hydrogen-nitrogen mixtures for quenching of arcs. One typically associates hydrogen with flammability, but it also has fantastically high diffusive properties which could lead to quicker arc quenching. We report how hydrogen concentration leads to smaller arc lifetimes, which in turn improves a circuit’s interruption performance. We simulated contact separation in hydrogen-enriched and pure air environments using VizSpark™ which showed us that a strong external magnetic field can stretch the arc and reduce its extinction time.
You mention that you used VizSpark™ in your research. Why choose VizSpark™ specifically? What scenarios / applications is it useful for?
VizSpark™ is a multiphysics CFD solver which is capable of capturing the interaction between the plasma and flow with high fidelity. One thing which I really like about it is its robustness for a wide range of thermal plasma problems. You can throw in tough multiphysics problems: permanent magnets, high voltages and currents, supersonic flows, conjugate heat transfer. In terms of industrial applications, I could think of EV Relays, fuses, and high-voltage circuit breakers. It could also be used for safety assessment in high-voltage applications. For example, if there is local arcing inside a battery pack and you want to assess the root-cause through V-I traces, you could potentially do it in VizSpark™.
WCX ’22 Attendees can view Dr. Ranjan’s presentation in the “Electric Motor & Power Electronics” session from 10:00 AM to 10:30 AM CDT on Wednesday, April 6th.
Thanks for reading! If you’re still curious about the topics discussed in this article, check out the following journal papers (and ask us for a free copy!):
Ranjan, Rakesh, et al. Modelling of switching characteristics of hydrogen-nitrogen filled DC contactor under external magnetic field. No. 2022-01-0728. SAE Technical Paper, 2022.
Interested in learning more about plasma flow simulations? Click here to take a look at our previous article. Feel free to follow us on Twitter and LinkedIn for more related news, or reach out to us directly at info@esgeetech.com.
In the fight against airborne particulates, semiconductor manufacturers face the unrelenting threat of contamination within their labs and facilities. Airflow, microfiltration, air ionization, air pressure, humidity controls, polymer toolsets, anterooms / air showers, and cleanroom suits are just a few of the considerations that manufacturers must make, all in the name of isolating lab processes from the outside world. Despite extensive procedures and costly investments, it is nearly impossible to produce an environment completely devoid of pollutants, and the most common of all pollutants is microscopic, fine particles of solid matter known simply as “dust.”
Unlike the dusty plasmas found in the Earth’s mesosphere and among celestial bodies that fascinate astrophysicists, dusty plasmas in labs here on Earth are a constant source of frustration within the semiconductor industry. Their presence within reactors and manufacturing equipment continues to threaten contamination of wafers and other critical components.
Perhaps someday in the future, the presence of dusty plasmas in semiconductor manufacturing facilities will cease to be, either by way of technological innovation or perfection of cleanroom procedure. But until that time, simulations must account for every piece of relevant physics in order to create a realistic model of these environments.
Making the Dust Fly for Semiconductor Manufacturers
Dust particles are common contaminants of plasma processing discharge chambers used in the semiconductor industry for etching and deposition. These particles can range from several nanometers to several hundred micrometers in size, accrue a relatively large negative charge in the plasma, and consequently are electrostatically trapped in the plasma. Large particles usually accumulate near the sheath edge, while small particles accumulate in the center of the discharge chamber where the electrostatic potential is usually the most positive.
Trajectories of particles (a) with Wafer Bias and (b) without Wafer Bias. Size of particles ranges from 0.15 microns to 0.5 microns. Image Source: Kobayashi et al.
For semiconductor manufacturers, formation of particles within a plasma and the effect of dust particles on a semiconductor’s processing surface are determining factors for overall process quality and yield. Developing macro-particle kinetic models that account for all associated physics (macro-particle growth, charge-up, and transport within a plasma) is a necessity in modern semiconductor processing reactor design.
As a result, the applications for studies surrounding dusty plasmas focus primarily on particle transport and plasma distribution. This is the case in plasma etching / deposition systems, where particle behavior can be expressed through calculation of measured gas temperature distribution and thermophoretic force. Thermophoretic force can then be controlled using plasma distribution controls, and by changing gas temperature distributions across wafers.
It was only until recently that these breakthroughs in particle control and plasma distribution relied on expensive and elaborate experiments. Now, particle-based simulations through software like VizGrain are able to predict these behaviors while including the core features necessary for creating a computational model:
A multi-subdomain capability, where multiple solids and gas regions can be described simultaneously.
Unstructured meshing for representing complex topologies with fine geometric features.
Modeling of static electric and magnetic fields as well as electromagnetic waves through coupling with an electromagnetics solver.
Treating subsets of the overall gas composition as a continuum through coupling with a classical fluid flow solver and a plasma solver.
VizGrain: A Versatile Computational Tool for Particle Simulations
A unique aspect of VizGrain is that it allows computational modeling of particle dynamics in a variety of systems, including:
VizGrain allows working with atomic-size particles as well as particles with finite macroscopic sizes. The former approach is used to model rarefied gas dynamics and conventional non-equilibrium plasmas, while finite-size macro-particles are considered for models of dusty plasmas, aerosols, and droplets to name a few. In this latter case, there is also consideration for electrical charge-up of particles in a plasma environment. Additionally, these models feature a comprehensive variety of drag forces that can act on both atomic and macro-particles.
VizGrain solves governing equations that describe the transport (motion and collisions) as well as the generation and destruction of particles in a specified domain. A number of different particle types, both “atomic” and “macro-scale,” can be solved.
Dusty plasma dynamics in a capacitively coupled plasma (CCP) reactor generated using VizGlow™ (fluid) and VizGrain (dust particles).
Electrically neutral species and radicals, as well as electrically charged species like electrons and positive and negative ions are atomic particle types that can be considered simultaneously. Macro-scale particle types, however, include molecular cluster and larger micron-to-millimeter scale dust particles.All such particles have mass, charge, and size attributes. The mass of atomic particles is immutable, while those of macro-scale particles can change based on governing laws. Similarly, the atomic particle charge is fixed while macro-scale particle charge can change based on charge-up processes.
In VizGrain, all the particles in a swarm are classified according to “particle type.” All particles of a particular type have individual properties such as mass, charge, and size (diameter or cross section). Extensive use of object-oriented programming principles means that implementation is modular, and extending the list of properties is possible whenever necessary.
VizGrain also offers flexibility in representing practical applications through complex geometries. Cells can be made from a mesh using triangles and quadrilaterals (for 2D), as well as tetrahedra, hexahedra, prisms, pyramids, or even a mixture of all the aforementioned cell types together.
Additionally, meshes can be prepared in a variety of formats that are used commonly by practitioners and imported into VizGrain. The code also outputs the maximum number of particles that exist in a cell over the whole mesh at selected screen output intervals, with warnings for severely skewed cells in the mesh that could portend poor quality solutions (especially in the case of electrostatic potential in PIC simulations). Note that the accuracy of pure particle simulation results are usually insensitive to the quality of the mesh, which has been confirmed in VizGrain simulations.
Thanks for reading! If you’re still curious about the topics discussed in this article, check out the following journal papers (and ask us for a free copy!):
Levko, Dmitry, et al. “VizGrain: a new computational tool for particle simulations of reactive plasma discharges and rarefied flow physics.” Plasma Sources Science and Technology 30.5 (2021): 055012.
Kobayashi, Hiroyuki, et al. “Investigation of particle reduction and its transport mechanism in UHF-ECR dielectric etching system.” Thin Solid Films 516.11 (2008): 3469-3473.
Merlino, Robert. “Dusty plasmas: from Saturn’s rings to semiconductor processing devices.” Advances in Physics: X 6.1 (2021): 1873859.
Merlino, Robert L., and John A. Goree. “Dusty plasmas in the laboratory, industry, and space.” PHYSICS TODAY. 57.7 (2004): 32-39.
Interested in learning more about plasma flow simulations? Click here to take a look at our previous article. Feel free to follow us on Twitter and LinkedIn for more related news, or reach out to us directly at info@esgeetech.com.
Humans took a big leap forward when we learned to control fire and use it for our daily needs. A similar leap happened when we learned to generate and handle plasmas, the fourth and most abundant state of matter found mostly in stars.
Today, every consumer electronic device and computing hardware relies on plasmas in their core manufacturing technology. The semiconductor industry isn’t the only industry to be revolutionized by plasma and its limitless applications; the metallurgical, aerospace, automotive, chemical and medical industries also rely on plasma technologies.
Plasma can be generated in several ways; one of the common forms of plasma used in industrial applications is Inductively Coupled Plasma (ICP). As its name suggests, the energy for producing and sustaining the plasma is provided by induction coils to which high-frequency alternating current is supplied. This type of plasma can be produced at a wide range of operating pressures, flow rates, and feed-gas compositions. As a result of its versatility, ICP’s are especially favored among semiconductor manufacturers to produce high-density plasmas for etching, deposition, and other processes in the fabrication of invisible electronic components embedded in very large-scale integrated circuits that constitute logic, memory, and other types of chips. A similar class of ICP’s discharges, albeit much bigger in size, is also used in the manufacture of flat panel displays and solar panels.
Plasma discharge, flow, and electromagnetic simulations are challenging on many accounts: transient electromagnetic fields, spatio-temporal variations in electron and ion densities due to chemical reactions, complex circuit configurations for power supply, and a plethora of surface reactions all need to be taken into account. The industrial researchers and product developers desire nothing less than highest fidelity simulations for understanding the plasma behavior at a wide range of length-scales.
Over the past 15 years, at Esgee Tech, we have developed our flagship simulation software VizGlow™ to accomplish the most challenging objectives as desired by the semiconductor industry. VizGlow™ is capable of simulating ICPs at a great fidelity by coupling plasma, electromagnetics, reactive flow, surface chemistry, and circuit dynamics. It supports large-scale 3D unstructured mesh of accurate and complex industrial wafer-processing reactors. In addition, various modifications to the classical ICP are possible such as multiple turn coils (this study), pulsing, multi-frequency input power, RF biasing at select surfaces, application of permanent magnetic fields, and operation in cavity resonant modes. All of these modifications can be simulated using VizGlow™.
In this blog post, we discuss a large-scale multi (dual) coil ICP reactor simulated using VizGlow™.
Large-Scale ICP Reactor: An Industrially-Relevant Problem
An ICP reactor is a workhorse for several semiconductor, flat panel, and solar industrial applications. The advantage of inductive power coupling is that there is low plasma potential drop across sheaths, generation of high-density plasma at lower electron temperature, which leads to higher ion flux and reduced ion bombardment energy at the wafer surfaces. Additionally, multiple spatially distributed inductive coils with multiple turns each helps generate a more uniform plasma covering a wider volume and processing surface area. Using multiple coils also allows for the generation of a complex and deliberately tailored spatial distribution of the electromagnetic fields that in turn enables exploitation of interesting properties of electromagnetic wave interference patterns for generating plasmas. Several parameters such as: position of the coils, coil structure, and current direction, could be altered to optimize the design of an ICP plasma. These are merely a few of the large number of parametric studies that one could explore using VizGlow™.
VizGlow™ enables large-scale reactor simulations such as the reactor discussed here, which measures 2.03m x 1.54m x 0.805m (LxWxH), and is used for processing wide area substrates such as for flat panel displays and solar panels. The computational domain is divided into following regions/sub-domains:
Coils: two spiral excitation coils are operated in-phase at a frequency of 13 MHz and power of 1 kW to generate EM waves.
Coil cage: a Faraday cage which houses two coils
Plasma: the region with an initial pressure of ~1 Torr in which argon plasma is generated
Window: an interface between the coil cage and plasma that isolates plasma and coils
Substrate: the surface that is exposed to the generated plasma for processing
Detailed Insights into Plasma Field
Plasma uniformity across a wide area is essential for generating uniform ion fluxes and radical fluxes at the wafer surface. The figure on the right illustrates that a dense plasma is generated directly underneath the coil and is highest underneath the dielectric window where the electromagnetic waves are introduced. VizGlow™ is able to capture the electromagnetic skin effect, i.e, shielding of the electromagnetic waves by high density plasma. Moreover, power deposition only occurs at a small zone within the skin depth. The active radicals and the ions then diffuse from this generation zone to the substrate usually located at the bottom of the chamber.
The results indicate that this fundamental ICP property is well represented by VizGlow™.
In an electromagnetic field, Poynting Vectors represent the electromagnetic energy flux and its direction. It is particularly important to understand the flow of energy as it is critical to the design and optimization of the plasma devices. Results obtained by VizGlow™ can be viewed in an immersive environment in the figure on top to see how these three-dimensional vectors carry the energy from the coils and deposit it in the plasma field. The color of the vector indicates the strength of the vector. These three-dimensional visualizations allow researchers to comprehend the plasma field in greater detail.
If you are someone as excited about plasma flow simulations as we are, feel free to follow us at LinkedIn or reach out to us at info@esgeetech.com.
Meanwhile, if you are curious about the latest developments in plasma flow simulations, feel free to go through the following journal papers (do ask us for a free copy!):
D. Levko, C. Shukla, R.R. Upadhyay, L.L. Raja, Computational study of plasma dynamics and reactive chemistry in a low-pressure inductively coupled CF4/O2 plasma, Journal of Vacuum Science & Technology B 39, 042202 (2021), https://doi.org/10.1116/6.0001028
T. Iwao, P.L.G. Ventzek, R.R. Upadhyay, L. L. Raja, H. Ueda, & K. Ishibashi, “Measurements and modeling of the impact of radical recombination on silicon nitride growth in microwave plasma assisted atomic layer deposition”, Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, vol. 36(1), pp. 03DB01, 2018, https://doi.org/10.1116/1.5003403
L. L. Raja, S. Mahadevan, P.L.G. Ventzek, and J. Yoshikawa, “Computational modeling study of the radial line slot antenna microwave plasma source with comparisons to experiments,” Journal of Vacuum Science &Technology A, vol. 31, no. 3, p. 031304, 2013, https://doi.org/10.1116/1.4798362
VizSpark is used to model a non-transferred direct current plasma torch in pure argon gas assuming axi-symmetry along the central axis. A steady state thermal plasma with temperatures from 15-20,000 Kelvin forms a supersonic, under expanded jet in the ambient region with visible Mach diamonds.
Plasma torches are devices that produce a steady thermal plasma jet. There are many applications for plasma torches including arc cutting, wielding, plasma spraying and waste treatment.
A plasma torch works by passing a high current between a working gas, typically an inert gas such as argon, helium, hydrogen or a mixture of inert gases. The high current arc heats the gas mixture to high temperatures (15-20,000 K) which then exits the device forming a jet of high temperature plasma. Plasma torches typically use direct-current (DC) power source applied through a central (hot) powered electrode. A plasma torch can either user a transferred arc, where the working material located outside the device acts as the anode, or a non-transferred arc where the anode is located inside the torch housing.
The simulation demonstrated here is for a direct-current, non-transferred arc using pure argon as the working gas.
Fig. 1 shows a typically plasma torch device as well as the domain and mesh for the simulation presented here. For this simulation, an axi-symmetric assumption was made to simplify the mesh and reduce the computational cost. The domain consists of a 2.5 mm radius tube that expands to a 5 mm. A 2.0 mm radius pin powered electrode is placed along the axis in the wider tube region. The walls of the tube act as the anode. Argon gas is fed into the tube from the bottom boundary at a total pressure of 3 bar, and the ambient outer region is kept at a pressure of 1 bar.
Fig. 2 shows the plasma temperature (top) and gas pressure (bottom) after a quasi-steady state has been reached. Gas temperatures exceed 20, 000 Kelvin inside the device while gas temperatures in the ambient jet are on the order of 15,000 Kelvin. The gas leaves the torch housing at supersonic flow velocities (4000 m/s) with pressures higher than the ambient. This results in an under expanded jet with Mach diamonds clearly visible in Fig.2 (middle) and Fig. 2 (bottom).
VizSpark software fully support parallel capabilities using a domain decomposition approach. Fig. 3 compares the mesh and resulting temperature for the same simulation conditions using 1 core (serial) and 48 cores (parallel). Note that the results between the serial and parallel simulation are identical between demonstrating that there is no loss in correctness when using parallel vs serial.
Fig. 4 is a plot of the simulation speedup (strong scaling) for the 80,000 cell plasma torch problem for processor counts varying between 1 and 48. 8 times speedup can be obtained for 24 cores and 16 times speedup is achieved when 48 cores are used.
VizSpark Plasma Modeling Software Package is part of the Overviz framework suite which provides an intuitive interface to set-up a project to be solved using VizSpark, manipulate multiple projects for parametric studies. VizSpark is provably fast, robust, and easy-to-use software and currently a leading industrial plasma simulation tool.
This application note illustrates the transient development of microwave field in an air-filled waveguide with an L-bend geometric feature. The Time-Domain Electromagnetic Wave Solver Module of the VizEM Electromagnetics Modeling Software Package developed by Esgee Technologies Inc. is used for this problem.
The 2D planar waveguide geometry and the computational mesh used for the simulations of this problem are shown in Figure 1. The waveguide is 100 cm long in the horizontal direction (x-direction) and 55 cm in the vertical (y-direction). The waveguide channel width is 10 cm in along the horizontal length and 18 cm along the vertical direction. The geometry comprises a wave inlet to the right and perfect electric conducting side walls along the length of the waveguide. The waveguide is terminated with a perfect conductor. The computational mesh has approximately 6,900 cells and comprises a single sub-domain for the wave propagation. The maximum of the mesh size is determined by the frequency of the microwave. For this particular simulation, the drive frequency is 1.5 GHz with in a vacuum wavelength of about 20 cm. The mesh resolution is such that about 40 mesh cells (5 mm length) resolve a single wavelength. It is important to note that the problem geometry does not accommodate a perfect integer number of wave lengths. Hence a true standing wave pattern at the drive frequency of 1.5 GHz is not expected for this problem.
For the time-domain solver a time-step of 10-12 sec is used. This corresponds to an approximate CFL number of 0.3 for the time-step. The simulation is run to a final time of 84 ns.
A wave is launched from the right inlet boundary with a non-zero wave field component in the y-direction. The wave travels down the waveguide (in the –x direction) and negotiates the L-bend and further propagates up the waveguide in the +y direction. Finally the wave interacts with the perfect electric conductor termination and is reflected back down the waveguide to form a standing wave in the waveguide. As mentioned above the geometry is such that a stationary (steady) standing wave can never be achieved in this geometry. Figure 2 shows a snapshot of the wave at 0.6 ns after the wave is launched at the inlet (the initial conditions being a wave-free domain). The wavelength is observed to be about 20 cm and is exactly the vacuum wavelength for the 1.5 GHz excitation. At a perfect electric conducting wall the tangential component of the wave field is zero while the normal component is non-zero. This feature is clearly seen in the wave at this time.
Figure 3 shows the transient development of the wave field at various times after the wave is launched at the inlet. At 6.6 ns the wave has reflected off the termination boundary and formed a standing wave pattern within the wave guide. Note that the perfect conducting waveguide wall in the vertical section of the waveguide dictates that the y-component of the wave field is zero, which results in a wave pattern that looks different from the horizontal section of the waveguide.
As seen in Figure 3, the amplitude of the standing wave grows in time until about 13 ns following which the amplitude decreases to reach a minimum at about 60 ns. After 60 ns the amplitude of the standing wave starts increasing again and the pattern repeats itself. Essentially the transient snapshots in Figure 3 show the occurrence of a lower frequency modulation of the standing wave indicating that a stationary (steady) standing wave is not established in this geometry as mentioned earlier.
This problem demonstrates the importance of using a time-accurate (time-domain) simulation of the electromagnetic wave phenomena and ability to capture higher and lower harmonic transients that are not resolved by a frequency-domain solution.
The VizEM software package provides a very robust environment to solve such problems with quick turnaround. The VizEM software is available through the Overviz framework. This framework features an easy-to-use interface that provides utilities for problem set-up, problem solution, and post-processing of the solution. Once a mesh is available, the problem discussed in this note can be set-up within a matter of a few minutes.
