Set Of Electron Collision Cross Sections Research Articles

Electron collision cross section set for N2 and electron transport in N2, N2/He, and N2/Ar

Electron collision cross section set for N2 is proposed. The proposed set consists of vibrational elastic momentum transfer cross section and cross sections for 31 rotational excitation, 29 rotational deexcitation, 10 vibrational excitation, 17 electronic excitation, 2 neutral dissociation, and 5 ionization collision processes. Electron transport coefficients in N2, N2/He, and N2/Ar are calculated by Monte Carlo method with considering anisotropic inelastic electron scattering and partitioning of the residual energy after the ionization collision on the basis of experimental results. The reliability of the proposed electron collision cross section set is demonstrated by comparing the calculated and measured electron transport coefficients in a wide range of reduced electric fields, E/N (E: electric field strength, N: number density of gas molecules). Comparison of the values of the electron transport coefficients in N2 calculated from eight individual cross section sets partly provided on LXCat with the measured values is also carried out. Furthermore, the effect of anisotropic inelastic electron scattering on the electron transport coefficients is examined. The electron transport coefficients in N2 are found to be affected by considering anisotropic electron scattering with increasing E/N values, and the longitudinal third-order transport coefficient is found to be sensitive to considering anisotropic electron scattering even at middle E/N values.

Electron collision cross section set of Cl2 gas and electron transport analysis in Cl2 gas and Cl2/N2 mixtures

A detailed and reliable electron collision cross section set of Cl2 gas is constructed. The present cross section set consists of one elastic momentum transfer, three vibrational excitation, eight dissociative electronic excitation, two electronic excitation, one ion-pair formation, one dissociative electron attachment, and four ionization cross sections. The electron drift velocity, longitudinal diffusion coefficient, ionization coefficient, and electron attachment coefficient in both Cl2 gas and Cl2/N2 mixtures and the electron attachment rate coefficient in mixtures of N2 gas and a minute amount of Cl2 gas are calculated by Monte Carlo simulation using the present cross section set, and then the reliability of the present cross section set is demonstrated by comparing calculated and measured electron transport coefficients and rate coefficients. Furthermore, the rate coefficients for both elastic and inelastic electron collisions and the mean energy of electrons in Cl2 gas are calculated from the present cross section set and are provided.

Dissociative reactions induced by electron impact and electron transport in TEOS vapor

Reactions for dissociative ionization and neutral dissociation collisions between an electron and a tetraethoxysilane [Si(OC2H5)4, TEOS] molecule are reported, and neutral dissociation cross sections are calculated by applying the classical Rice–Ramsperger–Kassel theory. Detailed electron collision cross section set of TEOS vapor, including 18 neutral dissociation cross sections and 20 ionization cross sections, is constructed. Electron transport coefficients, such as the mean-arrival-time drift velocity, bulk drift velocity, longitudinal bulk diffusion coefficient, and ionization coefficient, and rate coefficients for both elastic and inelastic collisions in TEOS vapor are calculated from the present cross section set using a Monte Carlo method. The validity of the present cross section set is demonstrated by comparing the calculated electron transport coefficients with measured data. Furthermore, fragmentation of TEOS molecules by electron impact is simulated, and then the number of fragments produced in the simulation is compared with the measured mass spectra.

Electron Collision Cross Sections for the TRIES Molecule and Electron Transport Coefficients in TRIES-Ar and TRIES-O2 Mixtures

A reliable set of low-energy electron collision cross sections for the triethoxysilane (TRIES) molecule was derived based on the measured electron transport coefficients for a pure TRIES molecule by using an electron swarm method and a two-term approximation of the Boltzmann equation. The electron transport coefficients calculated using the derived set are in good agreement with experimental value over a wide range of E/N values (ratio of the electric field E to the neutral number density N). The present electron collision cross section set for the TRIES molecule, therefore, is the most reliable so far for plasma discharges and for materials processing using the TRIES molecule. Moreover, the electron transport coefficients for the TRIES-Ar and the TRIES-O2 mixtures were also calculated and analyzed over a wide range of E/N for the first time.

Measurement of electron swarm coefficients in chlorine and its mixtures with nitrogen

We have measured the electron drift velocity, density-normalized longitudinal diffusion and effective ionization coefficients for electrons in Cl2 and Cl2–N2 mixtures over the combined E/N range from 3 to 450 Td, using a pulsed Townsend apparatus especially designed to withstand the action of corrosive gases. Our measurements for the electron drift velocity and the effective ionization coefficient are compared with the only two previous measurements available, one of them indirect. In view of the present incompleteness and uncertainty in the electron collision cross section set for Cl2, Cl2–N2 mixtures with Cl2 contents from 1% to 80% have been measured in the aim of shedding more light into the completeness and reliability of the cross section set by testing the cross sections derived for pure Cl2 with those of the Cl2–N2 mixture for which the cross sections for N2 are well known.

Determination of the electron collision cross section set for the C2F6 molecule

The electron drift velocity and the density-normalized longitudinal diffusion coefficient in the pure C2F6 molecule over the E/N range of 0.1-100 Td have been measured using a double shutter drift tube, where E is the electric field and N is the neutral number density. Our electron drift velocity values are in good agreement with those reported in a previous work on the C2F6 molecule. The negative differential conductivity phenomenon was found in the electron drift velocity. The results of our new measurements on the pure C2F6 molecule, along with the available electron transport coefficients, in 0.524 and 5.47 % C2F6 - Ar mixtures were used to successfully obtain the most reliable set of electron-collision cross sections for the C2F6 molecule by using a multi-term Boltzmann analysis.

Determination of the electron collision cross-section set for the C4F6 molecule by using an electron swarm study

A set of electron collision cross-sections for the C4F6 molecule has been successfully determined for the first time by using an electron swarm method with a two-term approximation of the Boltzmann analysis. The set is evaluated by fitting the calculated electron drift velocities in pure C4F6 and in C4F6-Ar mixtures to the experimental data in the E/N range of 0.35 — 1200 Td (1 Td = 10−17 Vcm2), where E/N is the ratio of the electric field (E) to the neutral number density (N). The set is confirmed to be reliable due to our ability to reproduce satisfactorily the electron drift velocities in pure C4F6 and in 0.1, 0.5, 1, 5, and 10% C4F6-Ar mixtures with deviations of ±5%. The set may be the best available so far for use in the quantitative numerical modeling of a4 plasma discharge for various processing procedures with materials containing C4F6 molecules.

Electron Collision Cross Sections for the Cl2 Molecule from Electron Transport Coefficients

The measured electron transport coefficients (electron drift velocity, Townsend first ionization coefficient, electron attachment coefficient, and density-normalized effective ionization coefficient) in pure Cl 2 have been analyzed to derive the currently best available electron collision cross section set of the elastic and inelastic electron collision cross sections for the Cl 2 molecule using an electron swarm study and a two-term approximation of the Boltzmann equation for energy. The electron transport coefficients calculated using the derived cross sections are consistent with the experimental data over a wide range of E / N values (ratio of the electric field E to the neutral number density N ). The present electron collision cross section set for the Cl 2 molecule is the best available so far for quantitative numerical modeling plasma discharges for processing procedures with materials containing Cl 2 molecules.

Ionization and excitation collision processes of electrons in liquid water

This paper reports on Monte Carlo simulations of electrons in liquid water using a set of electron collision cross-sections constructed with data published recently. The track history of electrons having initial energy ranged from 1keV to 10keV is investigated looking at the ionization and excitation processes. The results show that the ratio of the ionization and excitation events per track history is unique independent of the initial electron energy above a couple of 100eV and these inelastic processes occur with low energy electrons frequently below 100eV. In particular, the excitation processes are dominated by the electrons below 50eV. Flight distance distributions between the inelastic collisions are also discussed.

Development of the electron impact cross section set for CHF3. Monte Carlo simulation of the swarm experiments in pure CHF3 and CHF3/Ar mixtures

Trifluoromethane (CHF3) is widely used in semiconductor processing. However, electron collision cross section set in CHF3 is not finally completed and verified yet. Cross section sets developed before were tested only in pure CHF3 and calculations with these sets do not describe swarm parameters in CHF3 diluted by Ar. In this work a numerical code based on the Monte Carlo method has been developed and used to calculate swarm parameters in pure CHF3 and Ar/CHF3 mixtures. Calculations in CHF3 diluted in Ar allowed us to validate the absolute value of vibration cross sections. The values and the shapes of momentum transfer, attachment and dissociation cross sections in CHF3 were renormalized on the base of the thorough analysis of all available experimental data and quantum-mechanical calculations. As a result physically well-grounded cross section set for CHF3 was developed and verified on various swarm experiments in CHF3 and CHF3/Ar mixtures.

Electron swarm coefficients in SF6and CF4gas mixtures from Monte Carlo method

In order to save the computing time of Monte Carlo simulation, traditional null collision method is improved in which only one cross section needs to be evaluated at each collision speed. By this method, the electron swarm parameters such as effective ionization coefficient, , drift velocity and diffusion coefficient of SF6 and CF4 gas mixtures are calculated over the E/N range from 150 Td to 500 Td. A set of electron collision cross-sections that gives transport parameters in agreement with measurements for the pure gases is used. The simulation results are then compared with our experiment data, and show excellent agreements.

Swarm derived electron collision cross section set for the perfluorocyclobutane molecule

The cross section set of perfluorocyclobutane (c-C4F8) is determined by the electron swarm method. The modification is applied to the vibrational excitation cross section and the elastic momentum transfer cross section. Our previously measured electron swarm parameters (drift velocities, longitudinal diffusion coefficients and effective ionization coefficients) in 0.468% and 4.910% c-C4F8/Ar mixtures are used for the determination of the vibrational excitation cross section. The measured drift velocity and longitudinal diffusion coefficient in pure c-C4F8 are used to determine the correct elastic momentum transfer cross section. The calculated electron transport coefficients were derived using the Monte Carlo simulation method.

Database in low temperature plasma modeling

This article is composed of recommended sets of electron collision cross-sections and reaction cross-sections of excited species assessed by a swam method and of information on transport coefficients and reaction rates (cross-sections) of ions, which are needed in low temperature plasma modeling. These data have been piled up by the Investigation Committee on “Discharge Plasma Electron Collision Cross-sections”, IEE Japan, and the author’s laboratory. The gases taken for the assessment in this work are rare gases, Hg, N 2, O 2, CO 2, CF 4, CH 4, GeH 4, SiH 4, SF 6, C 2H 6, Si 2H 6, c-C 4F 8 and CCl 2F 2.

Electron transport coefficients in SF6 and c-C4F8 mixtures

The ionization alpha , electron attachment eta and other electron transport coefficients for SF6 and perfluorocyclobutane (c-C4F8) gas mixtures have been calculated by a three-term Boltzmann equation method over the E/N range 283-707 Td. A set of electron collision cross-sections that gives transport parameters in agreement with measurements for the pure gases is used. The calculation is performed for important experimental conditions, i.e. the steady-state Townsend (SST), pulsed Townsend (PT) and time-of-flight (TOF) methods. It is found that the greater the reduction in E/N the more pronounced is the peak of eta values of mixtures, e.g. at E/N=283 Td the peak appears at the SF6 partial pressure k around 20%, though alpha values show monotonical variation with k, at a fixed E/N for the E/N range studied here. As a result, the E/N value at which alpha = eta , i.e. the limiting E/N of 20% SF6 and 80% c-C4F8, can exceed the values for the respective pure gases. This fact suggests that this combination may be one desirable synergistic mixture since the limiting E/N is an important parameter for predicting the dielectric characteristics in electronegative gases.

Validity of the continuous-slowing-down approximation in electron degradation, with numerical results for argon.

The electron degradation spectrum plays a key role in describing the electron slowing-down processes in matter. The validity of a method to obtain the electron degradation spectrum approximately, i.e., the continuous-slowing-down approximation with full accounting of electron production, is examined. Numerical results derived with this method are compared with the direct solution of the Spencer-Fano equation for argon using the same set of electron-collision cross sections. The method is effective at electron kinetic energies much higher than the first ionization threshold but fails at low electron kinetic energies even when the kinetic energy of an incident electron is high. Reasons for this failure are discussed in detail.

Analysis of Discharge Properties in CCl2F2 by the Boltzmann Equation Method

In order to make detailed analysis by the Boltzmann equation possible, a set of electron collision cross-sections for CCl2F2, an important material in various fields, is determined for the first time. In spite of the lack of available cross-section data, Boltzmann equation analysis using the set of values determined here gives calculated values which agree well with measurements of the swarm parameters of CCl2F2, indicating the validity of the cross-section set and the method of analysis. In addition, the accuracy of the set of values was checked by test calculations, and the Boltzmann equation method was then applied to CCl2F2+N2 gas mixtures, giving results which explain the flashover properties of the mixtures very well.

Application of the ZBA-10 electron-beam exposure system in the production of precision photomasks with pattern element dimensions in the submicron range : S. A. Inozemtsev, A. S. Korablin, V. M. Sutyrin and P. Hahmann. Jena Rev.2/1979, 62

This paper reports on Monte Carlo simulations of electrons in liquid water using a set of electron collision cross-sections constructed with data published recently. The track history of electrons having initial energy ranged from 1 keV to 10 keV is investigated looking at the ionization and excitation processes. The results show that the ratio of the ionization and excitation events per track history is unique independent of the initial electron energy above a couple of 100 eV and these inelastic processes occur with low energy electrons frequently below 100 eV. In particular, the excitation processes are dominated by the electrons below 50 eV. Flight distance distributions between the inelastic collisions are also discussed.