Ansys Charge Plus What’s New 2023 R2

Workflow improvements are coming to Ansys Charge Plus in 2023 R2.

This is the first release of the renamed Ansys Charge Plus, formerly EMA3D® Charge. Charge Plus combines electromagnetic (EM) solvers, fluid solvers, and particle physics solvers to provide easy-to-use multiphysics simulation. The four main workflows are spacecraft charging, electrostatic discharge (ESD), arc extinction and generation, and plasma enhanced chemical vapor deposition (PECVD).

Charge Plus has the capability to take a closer look at:

• Space environment and radiation effects
• Electrostatic discharge
• Arc extinction
• Semiconductor plasma modeling

2023 R2 includes three main featured updates including:

• Advanced plasma and gas flow modeling
• Integrations with Ansys Chemkin-Pro
• Mesh engine updates

Advanced Plasma and Gas Flow Modeling

In the latest update, a fluid dynamics solver has been added to Charge Plus.

“Previously in 2023 R1, (the solutions) were enough to be able to model very low-density plasmas but when we deal with higher density plasmas like the ones that we find in chambers for semiconductor manufacturing, we need to introduce a new type of physics which is fluid dynamics,” said EMA Senior Scientist Kevin-Druis Merenda.

Compressible fluid dynamics has been coupled to the existing EM and particle-in-cell solvers (PIC) to tackle these higher density simulations. This integration creates an advanced simulation tool for plasma and gas flow modeling in applications such as PECVD, sputtering, and etching. It also allows users to model discharges within plasmas.

“We have E-field emission of electrons in a certain system based on the amplitude of the electric fields and then coupled to the ability to model ionization of that plasma,” Merenda said. “We’re able to model the discharge processes, not just the plasma generation but also any risk of arcing in the system.”

As a way to reach quasi-static states the three solvers co-simulate at each timestep, but it has to handle a different time scale for each solver. The EM solver requires a time scale small enough to deal with radio frequency sources while the PIC solver needs to model fast moving electrons. The fluid solver will run for much longer times.

“It’s important to be able to handle all these time scales, some of them being as large as hours while some of them being as small as picoseconds,” Merenda said.

Figure 1 shows the different time scales each solver uses.

Depending on the regime you are using when you model the plasma in a chamber or in space, this new solver co-simulating with the other solvers lets users leverage the new physics to be able to solve the problem more accurately.

Figure 1. Timescales needed for each solver in Charge Plus to make an impossible simulation practical.

Figure 2 is a look inside of a PECVD chamber showing the electron dynamic based on an RF source placed in the system. Charge Plus integration with Ansys Graphite and Discovery along with post-processing capabilities in Ansys Ensight, the user can look at the density enhancements in the system, temperature distributions, and the flow of the fluid of the chamber due to the settings that are set at the initialization of the simulation.

Figure 2. Example of electrons pulsing and the density changing based on the EM forces exerted on the system.

Integrations with Ansys Chemkin-Pro

The second highlighted new feature is integration with Ansys Chemkin-Pro. Chemkin is used for modeling complex, chemically reacting systems. It has been extensively validated in numerous chemistry applications and is well known for its extremely fast simulation time.

“We also coupled with the Chemkin API to be able to get access to the interaction rates between each of the components in the system,” Merenda said.

Ionized gas and surface reactions are captured in Charge Plus by coupling Chemkin-Pro to the PIC and the computational fluid dynamic (CFD) solvers. This provides a streamlined approach to simulating the complex chemical reactions involved in plasma-assisted processes.

Microscopic gas and plasma interactions are controlled through the Chemkin API. Each nodal location in the finite element mesh in Chemkin is treated as a closed reactor. Chemkin calculations update the Charge Plus solver which then evolves the macroscopic system. The global Charge/Chemkin system updates iteratively, providing a time dependent, self-consistent description.

The plot in Figure 3 shows the average electron temperature in the system over three cycles. One model depicts the electrons interacting with other gas species in the system, and the other is without.

Figure 3. Effect of using Chemkin on electron temperatures

“There is a drastic difference when we don’t model the interaction of these electrons with the other gas species in the system,” Merenda said. “We can see that the temperature of the electrons fluctuates drastically and reaches 10s of eV, which is way more than what you would expect.”

Merenda says that when you calculate reaction rates as a part of a system the electrons propagate less in the system and the average energy of the electrons is closer to what is expected.

Using this method, users can have 3D homogeneity mapping of the deposition rate on the wafer in the chamber, modeled with a fundamental multiphysics approach.

Mesh Engine Updates

2023 R2 includes a series of mesh engine updates.

The native Discovery mesh engine, Artemis, has been added to Charge Plus. This tightens the integration and partnership with Ansys Discovery. The integration improves the meshing speed and stability when using the time domain FEM solver.

“One of the key opportunities here is to be able to improve our radiation hardening workflow,” Merenda said. “We can now report in 3D in Ansys Charge Plus on TID, TNID, LET and also EM fields generated by the radiation from these processes.”

The second update is the ability to create a variable mesh within the finite-difference time-domain (FDTD) solver. This is the same FDTD solver used in Ansys EMC Plus. This allows users to have smaller mesh sizes in some locations to resolve tiny features and larger mesh sizes in areas without such features to allow for faster computation. Figure 4 shows the mesh, you can see the grid is smaller near the PCB and gets larger the further away you get.

Figure 4. Variable mesh grid in Charge Plus.

As an example, Charge Plus has the ability to set up an electrostatic discharge (ESD) gun to find discharges on printed circuit boards (PCB) or in enclosures. This includes both non-contact and contact discharges. Once the ESD gun is set up, users will need the variable mesh to be able to properly resolve the gaps between enclosure holes, between the ESD gun tip and the enclosure, and between the traces on the PCB.

“The ability of having the variable mesh for non-contact ESD simulations is critical,” Merenda said.

EMA has developed an Ansys Learning Hub course about ESD gun simulations. It will include step-by-step video and voice over. If you’re interested reach out to kevin.merenda@ema3d.com.

Other Updates

Additional new updates in 2023 R2 include:

• Ability to import EDB formats from SIwave.
• Ability to import solar illumination vectors from Ansys STK for a more dynamic surface charging simulation.
• Thin wire terminations.
• Relative humidity input to non-linear backgrounds.
• Table import capabilities.
• Surface charging chassis solver updates.

What’s New Webinar

EMA will be taking part in the Ansys Charge Plus 2023 R2 What’s New Webinar. It is Thursday, Sept. 21 at 9 a.m. MST. Product managers will give an in-depth look at the new features and how they will support your projects. Registration is now open, click here to get signed up.