IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Plasma Science Monday Sessions
       Session PS-MoP

Paper PS-MoP1
Molecular Structure of Fluorocarbon Deposits Analyzed by EIMS and CIMS Combined with Thermal Desorption Technique

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Plasma Diagnostics and Plasma-Surface Interactions Poster Session
Presenter: K. Sasaki, Nagoya University, Japan
Authors: N. Takada, Nagoya University, Japan
K. Sasaki, Nagoya University, Japan
K. Shibagaki, Nagoya University, Japan
K. Kadota, Nagoya University, Japan
Correspondent: Click to Email
In order to understand plasma-surface interaction in fluorocarbon plasmas, the analysis of fluorocarbon deposits is an important issue. To date, x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) are exclusively adopted for the analysis of fluorocarbon films. However, detail of the molecular structure of fluorocarbon films cannot be understood by XPS and FTIR. In the present work, we adopted electron-impact mass spectrometry (EIMS) and chemical ionization mass spectrometry (CIMS) for the analysis of the molecular structure of fluorocarbon films produced by C@sub 4@F@sub 8@ and C@sub 4@F@sub 8@-H@sub 2@ plasmas. A thermal desorption technique was used to evaporate fluorocarbon molecules from samples. In EIMS, thermally desorbed molecules were ionized by an electron beam with an energy of 70 eV. In CIMS, isobutene is ionized by electron impact to produce slow electrons. Negative fluorocarbon ions were produced via dissociative electron attachment of the slow electrons. The threshold temperature for thermal desorption of fluorocarbon molecules from a sample produced by a C@sub 4@F@sub 8@ plasma was 100-160 °C. Many peaks corresponding to mass numbers up to 800 were observed in the EIMS spectrum. The major peaks were classified into two groups having structures of CF@sub 3@(CF@sub 2@)@sub n@@super +@ and CF(CF@sub 2@)@sub m@@super +@. This result indicates that molecules desorbed from the sample contain the polymerized structure of CF@sub 2@. The overall shape of the CIMS spectrum of the fluorocarbon sample was similar to that of perfluorokerosene (PFK), which has a molecular structure of CF@sub 3@(CF@sub 2@)@sub n@CF@sub 3@. This suggests that fluorocarbon molecules desorbed from the sample have a molecular structure similar to PFK. By comparing the CIMS spectra of the sample and PFK, the mass number of the desorbed molecule was estimated to be 1100.