Electron Impact Ionization of SiCl_x and TiCl_x (x = 1–4): Contributions from Indirect Ionization Channels

Abstract

We measured absolute partial cross sections for the formation of various singly charged positive ions produced by electron impact on SiCl x (x = 1–4) using two different experimental techniques, a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam apparatus. The energy range covered was from the threshold to 900 eV in the TOF-MS and to 200 eV in the fast neutral beam apparatus. In the case of SiCl4, the absolute cross sections obtained by the two different experimental techniques were found to agree very well. The ionization of the SiCl x (x = 1–3) free radicals can only be studied using the fast-beam technique. Some of the partial cross section curves were found to exhibit an unusual energy dependence with a pronounced low-energy maximum at an energy around 30 eV, which is in some cases followed by a shallow minimum at about 40 eV and a broad second maximum at around 100 eV. This pronounced low-energy maximum is indicative of the presence of an indirect ionization channel and is similar to what has been observed earlier for TiCl4 and the TiCl x (x = 1–3) radicals. Similarities in the contribution of the indirect ionization channel to the formation of the various SiCl x + and TiCl x + (x = 1–4) ions will be highlighted in this paper.

Numerical Investigation of SiO2 Coating Deposition in Wafer Processing Reactors with SiCl4/O2/Ar Inductively Coupled Plasmas

“…Finally, since there is typically no bias applied for SiO 2 coating deposition, the sputter yield is not very high and, for the conditions under study in this paper, it could be concluded that ions do not have a significant influence on the deposition process and that sputtering effects are [17,20] e þ Si ! Si þ þ 2e s(E) [8] e þ SiO !…”

“…Comparing these density profiles indicates a stepwise dissociation process from SiCl 4 towards SiCl in the bulk plasma. Indeed, it is more likely to create SiCl 3 from SiCl 4 , SiCl 2 from SiCl 3 and so on, abstracting only one Cl atom or Cl + ion each time . This explains the maxima of the densities of SiCl 1–3 since the gas is injected towards the center of the wafer and then disperses in the lateral direction.…”

Electron-impact ionization of SiCl, SiCl₂ and SiCl₄ molecules

“…From experimental side a few results are available [10][11][12][13][14] for these molecules. Comparisons are made of present results with experimental results and the theoretical results of DM formalism [10,12] and the CSP-ic model of Kothari et al [16].…”

“…Becker et al [11] have measured electron impact ionization of SiCl x (x=1-4) using a time-of-flight mass spectrometer (TOF-MS) and a fast-neutral-beam techniques. The energy range covered in the TOF-MS was from the ionization threshold to 900 eV and up to 200 eV in fast-neutralbeam apparatus.…”

“…From theoretical side, the authors [10][11][12] have calculated the total ionization cross sections using DM formalism. Deutsch et al [15] have calculated the ionization cross sections of SiCl x (x=1-4) using a modified additivity rule (MAR) in the energy range from 30 to 200 eV.…”