Optical emission measurements of H2-N2 rf glow discharge plasmas

• Main Authors: Nakada, H., Suda, K., Motohashi, M.
• Format: Conference Proceeding
• Language: English
• Subjects: Glow discharges; Optical variables measurement; Plasma measurements; Plasmas; Radio frequency; Stimulated emission; Temperature measurement
• ISSN: 0730-9244; 2576-7208
• DOI: 10.1109/PLASMA.2012.6383915

Summary form only given. H 2 -N 2 rf glow discharge plasmas are used for the surface etching and modification of low-dielectric-constant (low-k) materials and silicon-based materials. It is well known that the radicals and ions in the plasmas play an important role in the surface treatment. Therefore, the analysis of these species (ions and radicals) is important. However, the diagnosis of H 2 -N 2 plasmas is very difficult because the mechanisms of decomposition and excited state reactions are very complicated. In this study, we evaluated an H 2 -N 2 rf glow discharge plasma by using optical emission spectroscopy (OES). In addition, the decomposition and excited state reactions were studied. Diode-type CVD and source gas separated plasma CVD (SSP-CVD) methods were used to generate the H 2 -N 2 plasma. These methods were based on a charge-coupled plasma excited at a frequency of 13.56 MHz. The gas flow rate ratio y [N 2 /(H 2 + N 2 )] and the rf power were varied. The emission species produced by the N 2 * 1st positive system, the N 2 * 2nd positive system, the N2+ 1st negative system, H2*, and H* (Hα and Hβ) were observed. Then, the emission intensity of the species, I(N 2 * 1st Pos.), I(N 2 * 2nd Pos.), I(N 2 + 1st Neg.), I(H 2 *), I(Hα), and I(H β ), was measured by OES. We found that the ratio of I(N 2 * 2nd Pos.) to I(N 2 * 1st Pos.) and the ratio of I(H β ) to I(H α ) are constant regardless of the type of CVD reactor. I(N 2 + 1st Neg.) in diode CVD was greater than that in SSP-CVD. I(H 2 *) in SSP-CVD was greater than that in diode CVD. In other words, while the intensity of emission is decided by the energy level, it is also related to the internal reactions among species in the plasma discharge. In addition, it was found that the optical emission characteristics of the species change when the energy of the species is high (above approximately 13 eV). In the H 2 -N 2 glow discharge plasma, the optical emission intensities of N 2 + and H 2 * depend on the type of chamber used. It was found that it is important to make observations in the range above about 13 eV for this plasma. In addition, the electron temperature and density were measured by using a Langmuir single probe in order to discuss the relation between the species and the electron in the plasma. It was found that the ratio of I(N 2 + 1st Neg.) to I(N 2 * 1st Pos.) is related to the electron temperature and density.