A key step in the overall development process is computer modeling of a machine design, which is considered as a risk reduction process by providing in-depth insights into the characteristics of a machine prior to cutting metals and spending excessive costs.
This article discusses the fabrication of a 2D axisymmetric model of an argon ICP in a PlasmaPro Estrelas100 tool from Oxford Instruments Plasma Technology. The simulation work is then validated using an HIDEN ESPION advanced Langmuir probe system as a plasma diagnostic.
Figure 1 shows the fundamental structure considered for the process. A commercial software CFD- ACE + from ESI group is used to model the discharge chamber. The software package comprises different multiphysics sub modules engineered for modeling various physical processes, including chemistry, plasma, heat transfer, gas flow, magnetic and electric fields. After defining all input parameter values needed by these modules, the solver is used to resolve the underlying equations.
Figure 1. Schematic drawing of reactor in PlasmaPro Estrelas100 tool
The solver’s output provides values of electron and ion mobility, pressure distribution, electric and magnetic field distribution, power dissipation, electron number density, electron temperature, ion and radical density inside the reactor. It is also possible to view these values utilizing a post processing tool.
Figure 2. PlasmaPro Estrelas100 Clutter System
The simulated argon ion number density distribution is illustrated in Figure 3. The result demonstrates that it is possible to reach an ion density value of 2.5x1018 m-3 at the input power of 1 kW and gas pressure of 20 mtorr.
Figure 3. Simulated ion density profile in the discharge chamber for 1 kW RF input power and argon pressure of 20 mtorr
The comparison of the simulated argon ion density radial profile near the wafer and the Langmuir probe measurement data is depicted in Figure 4. The simulation is very much in line with the measured data without the use of fitting parameters.
Figure 4. Comparison of simulated and measured argon ion density profile for 20 mtorr 1000W ICP along a radial line located 20 mm above the wafer surface
Druyvestyn method is used to derive the electron energy distribution function, as shown in Figure 5. This method utilizes the electron current’s second derivative relating to probe voltage. It is illustrated that the measured electron temperature, an average value over energy space, is around 1-2 eV for a variety of process windows.
Complex plasma chemistry such as SF6 and C4F8 discharge will be the focus of future work for real processes modeling.
This information has been sourced, reviewed and adapted from materials provided by Oxford Instruments Plasma Technology.
For more information on this source, please visit Oxford Instruments Plasma Technology.