Development of 0 – D argon collisional radiative model conjoined with optical emission spectroscopy for radio frequency plasma

Plasma-based processes are becoming increasingly popular due to a rising demand for nano-scale semiconductor chips, and as a result, understanding plasma and its processes has become crucial. Multiple diagnostic tools such as Langmuir probes (LP), retarding field energy analyzers (RFEA), laser-induced fluorescence (LIF), or optical emission spectroscopy (OES) are often employed for measuring plasma parameters, which can be resource-intensive and time-consuming. Recently, a computational plasma diagnostic technique, collisional radiative model (CRM), has been gaining attention because it is a non-intrusive diagnostic technique that can compute electron properties by simulating the chemical network within a plasma system, unlike conventional OES while providing elemental and excitation or ionization levels of gases in plasma. Thus, this project aims to develop a global argon collisional radiative model (CRM) coupled with optical emission spectroscopy (OES) for various pressures. The model considers various argon states such as Arg, Ar4s, Ar4p, Ar3d, Ar5s, Ar+, Ar2+, and Ar2x and their reactions. Then, it includes particle and power balance equations to calculate the electron temperature, density, and gas temperature of radiofrequency plasmas. Two models with different density assumptions are developed to test the accuracy at different pressure regimes. Electron temperature and electron density obtained by Langmuir probe (LP) at low-pressure RF plasma by Chai are 2.17 eV and 3.43e17 m-3, while the computed values from the model with uniform density assumption are 2.23 – 2.83 eV and 1.64e17 – 3.16e17 m-3 with merit number of 8.97 % [1]. Also, electron temperature, gas temperature, and electron density measured and calculated in atmospheric-pressure microwave plasma by Jean are 1.4 eV, 1561 K, and 8e20 m-3, while the derived values from the model with non-uniform density assumption are 1.09 – 1.29 eV, 1759.65 – 2605.29 °K and 4.86e20 – 7.51e20 m-3 with merit number of 2.75 % [2]. These validation cases ensure that the model developed in this work is trustworthy for experimental measurements. The models with two density assumptions are combined to address low- and high-pressure regimes accurately and then applied to the data collected from experimental equipment in the lab. The electron temperatures obtained by LP and CRM for low-pressure RF plasma are both between 2.5 and 4.5 eV with a relatively consistent trend. Electron densities vary roughly two orders of magnitude, 1e15 and 1e17 m-3, due to the restrictions of the equipment for LP and the steady-state power balance equation for CRM. The measurement of bulk plasma is impossible, so diffused plasma is measured. However, the electron densities and trends agree once the appropriate density profile across the z-axis is applied. The electron temperatures calculated via partial Saha local equilibrium (pSLE) and CRM at atmospheric pressure are consistent between 0.5 and 1 eV. The gas temperature, however, disagrees by roughly 4000 °K because the first positive system of nitrogen is used. If the second positive system of nitrogen is utilized, the gas temperature measured will be more in agreement with the computed gas temperature. The electron densities are not measured experimentally due to time constrictions regarding equipment usage, but the derived electron density ranges between 1e19 and 1e20 m-3.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Nuclear, Plasma, Radiolgc Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Choi, Tag Sang

Contributors dc:contributor

• Ruzic, David N
• Qerimi, Dren

• Collisional Radiative Model
• Crm
• Global Model
• Argon Plasma

Statement dc:rights

• Copyright 2024 Tag Choi

Language dc:language

eng, en

Handle dc:identifier

https://hdl.handle.net/2142/127413

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/127413