Carbon tetrafluoride (CF4) is one of the most widely used components of feed gas mixtures employed for a variety of plasma-assisted material-processing applications. It has no stable excited states and, in a plasma environment, is an ideal source of reactive species, especially F atoms. To assess the behavior of CF4 in its use in manufacturing semiconductor devices and other applications, it is necessary to have accurate information about its fundamental properties and reactions, particularly its electronic and ionic interactions and its electron collision processes at low energies (<100 eV). In this article we assess and synthesize the available information on the cross sections and/or the rate coefficients for collisional interactions of CF4 with electrons. Assessed information is presented on: (i) cross sections for electron scattering (total, momentum, elastic differential, elastic integral, inelastic), electron-impact ionization (total, partial, multiple, dissociative), electron-impact dissociation (total, and for dissociative excitation), and electron attachment (total, and for specific anions); (ii) coefficients for electron transport (electron drift velocity, transverse and longitudinal electron diffusion coefficients), electron attachment, and electron-impact ionization; and (iii) cross section sets derived from analyses of electron transport data. The limited ionization data on CF4 radicals are also presented, and references are made to measurements of electron transport properties of CF4 gas mixtures. Based upon the assessment of published experimental data, recommended values for various cross sections and coefficients are generated which are presented in graphical and tabular form.

Cross sections for the production of singly charged ions by electron impact on N2O and NO have been obtained by utilizing the relative flow technique in which the accurately known values of cross sections for the production of singly charged ions of rare gases have been used for normalization. By summing the cross sections for direct ionization and dissociative ionization, the total ionization cross sections have been obtained and compared with the previously available data. Energies for the appearance of various ions have also been measured and compared with previous determinations from photoelectron spectroscopy.

An oxygen plasma sustained at 13.56 MHz in a standardized reactor with a planar induction coil was used for biological decontamination experiments. Optical emission, mass spectrometry, Langmuir probe, and electrical measurements were applied to detection of chemical species and ion-energy and flux analysis. These diagnostics identified a plasma-mode transition in the range of 13-67-Pa pressure and 100-330-W power to the induction coil. At higher pressure and lower power, the plasma was sustained in a dim mode (primarily by stray capacitive coupling). A primarily inductive bright mode was attained at lower pressure and higher power. The coupling mode of plasma operation was then monitored by emission spectroscopy on an analogous, scaled-down reactor for biological degradation tests. Plasmid DNA degradation efficacies were compared in both plasma modes. DNA removal was ∼25% more efficient in the inductively coupled mode than in the capacitively coupled mode at the same power. The fast degradation was attributed to synergetic mechanisms (photo-and ion-assisted etching by oxygen atoms and perhaps O * 2 metastable molecules). Volatilization rates of the decomposition products (CO 2 , CO, N 2 , OH, H) evolving from the microbial (Deinococcus radiodurans) and polypeptide samples exposed to the plasma were compared. A plasma sustained in Martian atmosphere is considered.

In this paper we assess and synthesize the available information on the cross sections and the rate coefficients for collisional interactions of trifiuoromethane (CHF 3 ) with electrons in an effort to build a database on electronic and ionic collision processes that will aid the understanding of the behavior of CHF 3 in its use in manufacturing semiconductor devices and other applications. The limited data on the total and partial electron impact ionization cross sections, total and partial cross sections for electron impact dissociation of CHF 3 into neutral species, electron-impact induced line and continuous light emission from CHF 3 , negative ion states of CHF 3 , and the energetics of ionization, dissociation, and attachment are summarized and discussed. Besides some recent unpublished measurements of the total electron scattering cross section below 20 eV, to our knowledge no measurements are available of the cross sections of any of the electron scattering processes (elastic, momentum, vibrational, inelastic, etc.) or the electron trans-POlt, attachment,and ionization coefficients. While thc: available illfuHnatiull is meagta, the synthesis of the existing knowledge and the background information provided in the paper can be helpful for modeling plasma reactors. Clearly, more measurements and calculations are needed of the cross sections for virtually all fundamental electron impact processes for this plasma processing gas. Measurements of the transport, attachment, and ionization coefficients over wide ranges of the density reduced electric field are also needed.

Values of cross sections for the production of positive ions resulting from electron collisions with NH3 at impact energies ranging from threshold to 1 keV have been measured using a crossed-beams apparatus. These cross sections have been normalized by using the relative flow technique and the previously determined cross sections of He and Ne. The measured values are compared with previous data available in the literature. The threshold energy for the production of each ion has been measured. Total ionization cross sections as a function of electron impact energies have been deduced from the measured partial ionization cross sections.