A model study of the composition of the neutral and charged components of SF6 plasma is conducted in a wide range of electron concentrations. Key plasma-chemical processes that form stationary concentrations of fluorine atoms in low- and high-density plasma conditions are identified. It is shown that optimized (reduced due to inefficient reactions) kinetic schemes provide satisfactory agreement between the calculation results and experimental data from published sources.

The influence of the initial mixture composition, gas pressure and input power on electrophysical parameters and density of fluorine atoms in SF6 + Ar + He plasma produced in an inductive-type reactor at 2 MHz was investigated. The combination of plasma diagnostics by Langmuir probes and optical emission spectroscopy allowed one to determine behaviors of electrons- and ions-related plasma characteristics vs. variable operating parameters as well as to suggest mechanisms responsible for corresponding effects. In particular, it was shown that the substitution of argon by helium at constant SF6 content in a feed gas affects the electron temperature, densities of charged species and plasma electronegativity through changes in both total ionization rate and electron energy losses during their interactions with dominant neutral particles. It was found that input power produces the maximum effect on the F atom density (by similar to 9 times at w = 800-1250 W) while the influence of the Ar/He ratio and gas pressure (especially at p < 15 mtorr) appears to be much weaker. Such situation is caused by opposite trends of electron temperature and electron density that results in rather small changes in the effective frequency of SFx + e- SFx-1 + F + e reaction family. It was found that fluxes of both fluorine atoms (Gamma(F)) and positive ions (Gamma(+)) follow changes in their densities, and the minimum Gamma(F) /Gamma(+) value in He-rich plasmas corresponds to low pressures and input powers.

A high-power source of ultrawideband radiation with elliptical polarization based on a 64-element array of spiral antennas was developed. The array was excited by a bipolar voltage pulse with an amplitude of up to 240 kV and a duration of 1 ns at a repetition rate of 100 Hz. Radiation pulses with an ellipticity coefficient of 0.64 and a peak field strength of 250 kV/m at a distance of 10 m were obtained.

The electrophysical parameters of the plasma and the kinetics of plasma-chemical processes in a CF4 + H2 + Ar mixture while varying the CF4/H2 ratio are studied. When using diagnostic methods and plasma modeling together, it is found that replacing tetrafluoromethane with hydrogen (a) leads to a decrease in the plasma density and an increase in electronegativity; and (b) it causes a disproportionately sharp drop in the concentration of fluorine atoms. The reason for the latter effect is the increase in the frequency of the death of atoms in reactions of the CHFx + F → CFx + HF type initiated by heterogeneous recombination via the CFx + H → CHFx mechanism. The simultaneous increase in the concentration of polymer-forming CHxFy (x + y < 3) radicals indicates an increase in the polymerization load of the plasma on the surfaces in contact with it.

This work discusses the influence of inert carrier gases, Ar and He, on both gas-phase plasma characteristics and ZnO etching rate under typical reactive-ion etching conditions in the hydrogen bromide environment. Plasma diagnostics by Langmuir probes and 0-dimensional plasma modeling allowed one to compare how the content of given carrier gas does influence electrons-and ions-related plasma parameters, kinetics and densities of plasma active species. It was found that the transition toward Ar- or He-rich plasmas a) causes the growth of electron temperature (due to lower electron energy losses in collisions with atomic species); b) reduces plasma electronegativity; and c) results in opposite changes in both ion density and ion flux. The last phenomenon is due to opposite changes in total ionization rates determined by sufficient difference in ionization rate coefficients for Ar and He atoms. Important features of HBr + Ar plasma at 0-80% Ar are also the slower-than-linear fall of Br atom density (due to the intensification of electron impact dissociation for both HBr and Br2 molecules) as well as an increase in H atom density (due to decreasing their loss rate in gas-phase reactions). Etching experiments indicated that the ZnO etching rate is mostly contributed by the ion-assisted chemical reaction while the reaction rate decreases faster compare with the Br atom flux. The corresponding decrease in the effective reaction probability may be related to changes in both ion bombardment intensity and hydrogen passivation effect.

In this work, we investigated the influence of fluorocarbon component ratio in the CF4 + C4F8 + O-2 gas mixture on electro-physical plasma parameters, steady-state densities of active species and silicon etching kinetics under typical reactive -ion process conditions. The combination of plasma diagnostics (double Langmuir probes, optical emission spectroscopy) and plasma modeling confirmed known peculiarities of plasma chemistry of individual fluorocarbons in the presence of oxygen as well as provided an extended analysis of both fluorine and oxygen atom kinetics in the three -component gas mixture. It was shown that the substitution of CF4 by C(4)F(8 )at the constant fraction of O-2 a) causes the weak disturbance in electrons- and ions -related plasma parameters (electron temperature, electron density, ion energy flux); b) provides drastically increasing density of polymerizing CFx (x = 1, 2) radicals; and c) results in monotonically decreasing F atoms density. The latter is due to simultaneous changes in both F atom formation rate and their loss frequency, especially in C4F8 -rich plasmas. From experiments, it was found that Si etching rate is by more than 85% controlled by its chemical component (in a form of ion-stimulated heterogeneous reaction Si + xF -> SiFx ) and decreases with increasing C4F8 fraction in a feed gas. The change in effective reaction probability contradicts with the growth of polymer deposition rate and film thickness (as it follows from changes in gas -phase plasma characteristics) but may reflect the weakening of surface passivation by oxygen atoms.

In this work, we investigated the influence of inert carrier gas on electro-physical plasma parameters, steady-state densities of active species and kinetics of their interaction with ZrO2 under the condition of "soft" reactive-ion etching in chlorine. This regime assumes the lower-than-usual negative bias voltage in order to reduce both ion bombardment energy and etched surface damage. The combination of plasma diagnostics by Langmuir probes and 0-dimensional plasma modeling allowed one to analyze formation and decay kinetics for neutral and charged species at various gas mixing ratios. It was found that the mixing of Cl-2 with Ar or He at constant total gas pressure a) causes an increase in both electron temperature and plasma density; b) increases the Cl-2 dissociation degree through the acceleration of electron-impact processes; and c) intensifies the ion bombardment by the change of ion flux. From etching experiments, it was found also that the ZrO2 etching rate is mostly composed by its chemical component, but does not correlate with the change in the Cl atom flux. The latter reveals that a) the dominant ZrO2 etching mechanism is the ion- assisted chemical reaction and b) an increase in the effective reaction probability toward Ar or He rich plasmas reflects the acceleration of ion-induced heterogeneous effects, such as the destruction of Zr-O bonds and/or the desorption of low-volatile ZrClx compounds. The lower neutral/charged ratio obtained in Ar-containing plasma allows one to assume the more anisotropic etching. It was shown that above findings are surely valid in the pressure range of 4-12 mTorr as well at bias powers of 100 - 300 W.

In this work, we performed the comparative study of electro-physical plasma parameters, densities of active species and fluorine atom kinetics in CF4 + O-2 and C4F8 + O-2 gas mixtures with variable initial compositions at constant gas pressure and input power. The combination of plasma diagnostics by Langmuir probes and plasma modeling confirmed known features of plasma properties in individual fluorocarbon gases as well as allowed one to figure out key chemical processes determining plasma parameters in the presence of oxygen. It was shown that an increase in O-2 content with a proportional decrease in the fraction of any fluorocarbon component a) causes relatively weak changes in electrons-and ions-related plasma parameters; b) results in more drastic (compared with the dilution effect) decrease in densities of fluorocarbon radicals due to their oxidation into CFxO, FO and COx compounds; and c) sufficiently influences both formation and decay kinetics of fluorine atoms. The non-monotonic (with a maximum at similar to 40-50% O-2) change in the F atom density in the CF4 + O-2 plasma repeats behavior of their formation rate after the contribution of processes involving CFxO u FO species. The monotonic increase (with a constancy region up to similar to 40-50% O-2) in the F atom density in the C4F8 + O-2 plasma contradicts with the change in their formation rate, but results from decreasing decay frequency in gas-phase atom-molecular processes. The predictive analysis of heterogeneous process kinetics was carried out using model yielded data on fluxes of plasma active species. It was found that a) the addition of oxygen always lowers the plasma polymerizing ability; and b) the C4F8 + O-2 plasma keeps the higher polymerizing ability at any feed gas composition.

The processes of plasma-chemical and reactive-ion etching of silicon in trifluoromethane (CHF 3 ) are studied using optical emission spectroscopy. The dependences of the radiation intensities of atoms and molecules on the etching time, input power, and pressure of the plasma-forming gas are obtained and analyzed.

A four-channel bipolar pulse former with an amplitude of up to 80 kV, a duration of 1 ns (2 channels) and 2 ns (2 channels) and a repetition rate of 100 Hz at 50 Ohm loads is developed. The former is designed to excite ultra-wideband antennas with an extended frequency band. A distinctive feature of its circuit from similar former circuits, using two high-pressure spark gaps in each channel, is a single spark gap used to generate four synchronous pulses of different durations. This multi-channel spark gap switches four pulse-forming lines on one side to the ground, on the other side – to the loads. The proposed former has a high stability of pulses between the channels, both in duration and amplitude. The setup time of the former is significantly shorter compared to that of the analogues.

This work investigated the influence of component ratio, input power and gas pressure on electro-physical plasma parameters, steady-state densities of active species and reactive-ion etching kinetics for SiO2 in CF4 + Ar and Cl2 + Ar plasmas. The combination of plasma diagnostics by Langmuir probes and plasma modeling indicated that the variation of processing conditions causes similar changes in physical and chemical factors influencing the reactive-ion etching (RIE) rate for SiO2. The only one exception is the opposite effect of gas pressure on densities of fluorine and chlorine atoms. The analysis of RIE kinetics was carried out using model-predicted data on fluxes of ions and chemically active species. It was found that the dominant etching mechanism in both gas mixtures is the heterogeneous chemical reaction while the reaction rate correlates with fluxes of fluorine or chlorine atoms. The effective probability for the Si + nF -SiFn reaction decreases with an increase in the ion bombardment intensity. Such situation reveals no ion-driven limiting stages while the negative effect of ion bombardment may result from desorption of F atoms under conditions of high adsorption degree and spontaneous interaction mechanism. The effective prob-ability for the Si + nCl -SiCln reaction exhibits much lower absolute values as well as always traces the change in the ion bombardment intensity. This allows one to assume the ion-assisted reaction regime which is activated by the formation and/or cleaning of adsorption sites for chlo-rine atoms.

This work investigated the influence of component ratio in the HBr + Ar gas mixture on electro-physical plasma parameters, steady-state densities of active species and reactive-ion etching (RIE) kinetics for SiO2 and Si3N4 under conditions of inductive RF (13.56 MHz) discharge. The combination of plasma diagnostics by Langmuir probes and plasma modeling indicated that an increase in Ar content at constant gas pressure and input power a) caused an increase in electron temperature and densities of charged species; b) results in increasing ion bombardment intensity; and c) leads to the nearly proportional decrease in Br atoms density and flux. It was found that variations of SiO2 and Si3N4 etching rates vs. mixture composition are qualitatively similar while the maximum difference in corresponding absolute values takes place in pure HBr plasma. The analysis of RIE mechanisms was carried out using model-predicted data on fluxes of ions and bromine atoms. It was found that the dominant SiO2 etching mechanism is the ion-assisted chemi-cal reaction which is characterized by the nearly-constant rate in the range of 0-80% Ar due to an increase in the effective reaction probability. That is why the noticeable intensification of physical sputtering with increasing Ar fraction in a feed gas causes the only weak growth of obtained SiO2 RIE rate. Oppositely, the Si3N4 etching process is mainly contributed by the physical sputtering while the efficiency of ion-stimulated chemical reaction is limited by the low reaction probability. This provides both slower etching process (especially in Ar-poor plasmas) and stronger sensitivity of etching rate to the change in mixture composition.

A comparative study of the effect of small (up to 20%) substituting additives F 2 , H 2 , and HF on the kinetics and stationary concentrations of neutral particles in 50% CF 4 + 50% Ar plasma under the typical conditions of reactive ion etching (RIE) of silicon and its compounds is carried out. It is shown that the variation of the CF 4 /F 2 and CF 4 /H 2 ratios leads to opposite, interrelated, and nonadditive changes in the concentrations of fluorine atoms and fluorocarbon radicals. This provides wide ranges of regulation of the etching rate and polymerization capacity with the minimal disturbance of the parameters of the electronic and ionic components of the plasma. In contrast, the CF 4 /HF relation has the minimal effect on the rate of surface polymerization, but noticeably changes the concentration of fluorine atoms. Thus, there is a selective effect on the rate of the heterogeneous chemical reaction.

The effects of initial composition of CHF3 + O2 gas mixture on electro-physical plasma parameters, steady-state densities of active species and fluorine atom kinetics were investigated under the condition of constant gas pressure and input power. The combination of plasma diag-nostics by Langmuir probes and model-based analysis of plasma chemistry confirmed known from previous work features of plasma composition in the absence of oxygen (in particular, the domina-tion of HF molecules in a gas phase) as well as demonstrated how the oxygen influences steady-state densities of neutral species through kinetics of both electron-impact and atom-molecular re-actions. It was shown that the addition of O2 with a proportional decrease in the content of CHF3 a) results in noticeable changes in electrons-and ions-related plasma parameters (electron temper-ature, electron density, ion flux); b) provides the effective conversion of fluorocarbon radicals (CHFx, CFx) into such compounds as CFxO, FO and COx; and b) causes an increase in the fluorine atom density up to 50% O2. The last phenomenon contradicts with the change in the total F atom formation rate, but reflects a decrease of their loss frequency in the reaction family of CHFx + F - -CFx + HF. The model-based analysis of heterogeneous process kinetics was carried out using the set of tracing parameters based on gas-phase plasma characteristics. It was found that the ad-dition of oxygen lowers the plasma polymerizing ability through both decreasing flux of polymer-izing species and accelerating the oxidative destruction of deposited polymer film.

The parameters of the gas phase and the kinetics of reactive ion etching of SiO 2 and Si 3 N 4 under conditions of an induction RF (13.56 MHz) discharge with a varying HBr/Cl 2 ratio is studied. The study includes plasma diagnostics using Langmuir probes, plasma modeling to find stationary concentrations of active particles, measuring velocities, and analyzing etching mechanisms in the effective interaction probability approximation. It is found that the substitution of HBr by Cl 2 at a constant argon content (a) is accompanied by a noticeable change in the electrical parameters of the plasma; (b) leads to a weak increase in the intensity of ion bombardment of the treated surface; and (c) causes a significant increase in the total concentration and flux density of reactive particles. It is shown that the etching rates of SiO 2 and Si 3 N 4 increase monotonically as the proportion of Cl 2 increases in a mixture, while the main etching mechanism is an ion-stimulated chemical reaction. The model description of the kinetics of such a reaction in the first approximation assumes (a) the additive contribution of bromine and chlorine atoms and (b) the direct proportional dependence of their effective interaction probabilities on the intensity of ion bombardment. The existence of an additional channel of heterogeneous interaction with the participation of HCl molecules is proposed.

Разработан мощный источник сверхширокополосного излучения субнаносекундной длительности на основе гибридной антенны с офсетным отражателем. В фокусе отражателя расположена решетка 2 × 2 комбинированных антенн, возбуждаемых четырехканальным формирователем биполярных импульсов напряжения c амплитудой 65 кВ и длительностью 0.5 нс на частоте повторения до 100 Гц. Реализованы режимы излучения с дискретным сканированием волновым пучком, а также с линейной, ортогональными и эллиптической поляризациями. Получены импульсы излучения с напряженностью поля 40–120 кВ/м на расстоянии 4.5 м.

A high-power source of ultrawideband radiation of subnanosecond duration based on a hybrid antenna with an offset reflector has been developed. At the focus of the reflector, there is an array of 2 × 2 combined antennas excited by a four-channel bipolar voltage pulse former with an amplitude of 60 kV and a duration of 0.5 ns at a repetition frequency of up to 100 Hz. Radiation modes with discrete scanning of the wave beam, as well as with linear, orthogonal, and elliptical polarizations, were implemented. Radiation pulses with a field strength of 40–120 kV/m at a distance of 4.5 m were obtained.

The paper studies the influence of the voltage pulse waveform exciting the UWB antenna, on the radiated E-field amplitude. It is shown that the radiated pulse amplitude of the combined antenna excited by bipolar voltage pulses, is higher than that excited by monopolar voltage pulses.

A comparative study of the electrophysical parameters of the plasma, the fluorine atom concentrations, and the kinetics of reactive-ion etching of silicon in CF 4 + O 2 , CHF 3 + O 2 , and C 4 F 8 + O 2 mixtures of a variable (0–75% O 2 ) initial composition is carried out. It is shown that the dominant etching mechanism is always the ion-stimulated chemical reaction Si + x F → SiF x , whose rate has a maximum in the region of 20–50% O 2 . Based on the results of plasma diagnostics, it is found that the similar behavior of the concentration of fluorine atoms is typical only for mixtures of CF 4 + O 2 and CHF 3 + O 2 , while in the C 4 F 8 + O 2 mixture, there is a nonmonotonic change in the probability of the interaction. It is assumed that the latter effect is caused by the competition between the processes of reducing the thickness of the fluorocarbon polymer film and the oxidation of the silicon surface by oxygen atoms.

The influence of the initial composition of a CF4 + CHF3 + Ar mixture and bias power on the electrical parameters of the plasma, the composition of the gas phase, and the kinetics of heterogeneous processes on the treated surface under conditions of an induction RF (13.56 MHz) discharge is studied. It is found that the variation of the CF4/CHF3 ratio does not lead to significant perturbations of the parameters of the electronic and ionic components of the plasma, but significantly changes the concentrations of fluorine atoms and polymer-forming radicals. In contrast, an increase in the bias power at a fixed initial composition of the mixture has practically no effect on the concentrations of active particles, but is characterized by a proportional change in the energy of the bombarding ions. The model analysis of the kinetics of heterogeneous processes shows that the CF4/CHF3 ratio provides wider ranges of regulation of the etching rate of the base material, as well as the deposition rate of the fluorocarbon polymer film and its thickness.