Hydrogen-containing plasmas are widely employed during advanced interconnect fabrication for post-etch cleaning and pre-barrier surface preparation. While the interaction of hydrogen plasma with porous organosilicate dielectrics has been extensively studied, the influence of framework architecture on plasma-induced degradation remains poorly understood. Understanding this relationship is essential for the rational design of next-generation porous low-k dielectrics, where framework architecture is increasingly used to tailor electrical and mechanical properties while maintaining plasma compatibility. In this work, the response of two representative porous low-k materials—methyl-terminated organosilicate glass (OSG) and ethylene-bridged periodic mesoporous organosilica (PMO)—to pure H2 capacitively coupled plasma was investigated using Fourier-transform infrared spectroscopy, spectroscopic ellipsometry, ellipsometric porosimetry, dielectric measurements, and DFT calculations.Hydrogen plasma exposure induces progressive removal of organic groups, transient formation of Si–H species, restructuring of the Si–O–Si network, film shrinkage, pore densification, and increased moisture uptake in both materials. DFT calculations show that VUV photons preferentially cleave Si–C bonds, whereas rupture of the Si–O–Si backbone is energetically much less favorable. The transient evolution of Si–H is consistent with a consecutive reaction model involving VUV-induced formation of silicon dangling bonds, hydrogen passivation, and subsequent reconstruction of the silica network.Despite these common transformation pathways, PMO exhibits significantly slower degradation kinetics, delayed Si–H formation, and greater resistance to structural collapse than OSG. These differences are attributed to the distinct framework architecture of PMO, where ethylene bridges incorporated into the network retard hydrogen-assisted structural modification. The increase in dielectric constant is shown to arise predominantly from moisture adsorption during post-plasma exposure to ambient air rather than from intrinsic changes in the silica network.These results demonstrate that framework architecture governs not only the kinetics of hydrogen-plasma-induced structural evolution but also the resulting moisture sensitivity and dielectric degradation of porous low-k dielectrics.

Modern plasma technologies applied for nm-size devices require localizing ions' impact within up to atomic layer to avoid uncontrollable damage of underlying structures. The decrease in energy of ions incident on a surface is one of the ways to achieve this. In this work, SiO2 sputtering by Ar+, Kr+, and Xe+ ions at energies of 20-200 eV was studies in the low-pressure ICP-discharge at a plasma density typical for plasma processing. The rf-bias waveform tailoring due to high discharge asymmetry allowed generating and controlling ion narrow energy spectrum with FWHM 5 +/- 2 eV. Real time in-situ control over ion composition and flux as well as sputtering rate provided accurate determination of the SiO2 sputtering yield, Y(Ei). It is shown that at ion energy above similar to 70 eV, the "classical" kinetic sputtering mechanism prevails. In this case, Y(Ei) rapidly grows with ion energy, while decreasing with the decrease in ion mass. Below similar to 70 eV, the change of Y(Ei) is strongly slow down while the sputtering yield still stays high enough (>10(-3)), demonstrating the plasma impact on the sputtering mechanism. The obtained trends of Y(Ei) under the plasma exposure are discussed in light of possible SiO2 surface modification studied by AFM and angular XPS analysis.

The spatio-temporal dynamics of plasma in a symmetrical dual-frequency 81 MHz/1.76 MHz capacitive discharge under the influence of a low-frequency 1.76 MHz field has been studied. Using phase-resolved optical emission spectroscopy, the dynamics of argon and xenon emission intensity in the plasma was obtained. Measurements of the electron energy probability function (EEPF) at the center of the discharge were performed using a Langmuir probe, and electron density measurements were made using a hairpin probe. The main result is the dynamics of the intensity ratios of selected argon and xenon lines under different conditions: at pressures of 40, 200, and 400 mTorr, low-frequency voltage amplitudes of 100, 200, and 400 V, and input power at 81 MHz of 3 and 15 W. The dynamics of high-energy electrons was investigated based on a two-temperature approximation of the electron energy probability function.

H- ion dynamics in the positive column of H2 dc glow discharge was studied by the laser photodetachment technique in a wide range of pressure, 0.1–3 Torr, and current, 1-30 mA which cover a range of E/N from ~ 40 Td up to ~ 170 Td. Using partial modulation of discharge current it is shown that the H– concentration follows H atom dynamics due to fast detachment reaction with the atoms: the higher H density, the lower H-/ne ratio. Dynamics of H atom density at discharge modulation was measured by the time-resolved actinometry on Ar atoms while H2vibrational temperature was estimated by comparing measured and simulated H2 VUV absorption spectra. The analysis of the experimental dependencies of H– and H/H2 on the discharge parameters allowed estimating the effective rate constant of H– production in the discharge as a function of the reduced electric field. For this the discharge model including self-consistently state-to-state vibrational kinetics as well as H2 highly excited electronic states was developed. The main processes, that contribute to H– production and loss, are discussed in detail. Dissociative attachment to vibrationally excited H2(v) molecules is the main channel of H- production but occurs via the excitation of the well-known low-energy (εth ≈ 3 eV) shape resonance of H2-(X2Σu+) only at low E/N. At high E/N, the H- production mostly occurs via the excitation of the high-energy H2- states, such as H2-(B2Σg+, A2Σg+, C2Πu) and Feshbach resonances similar to H2-(2Σg+) Rydberg state.

The paper deals with the experimental and theoretical study of the interaction of quasi-two-dimensional MoS2 films with nitrogen and oxygen plasmas in order to reveal the main mechanisms of their surface functionalization and to analyze its effects on the structure and properties of the films. Diagnostics of samples before and after treatment with radicals and ions was performed ex situ by Raman spectroscopy, spectroscopic ellipsometry, atomic force microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results of the experimental study showed that nitrogen and oxygen plasma treatment of ultrathin MoS2 films leads to the modification of the near-surface layers of the samples due to the removal of sulfur and the incorporation of incident atoms into forming vacancies. Nitrogen and oxygen ions with even low (less than 30 eV) energy causes partial removal of upper layers of the films leading to their partial destruction, while remote plasma (mainly by thermal radicals) guarantees more ‘soft’ treatment of films. The obtained spectroscopic data also indicated different effects of radicals (thermal O and N atoms) on the MoS2 surface. To analyze these effects, the computer modelling with density functional theory method was carried out. Its results enables to reveal the main mechanisms of the surface functionalization of MoS2 monolayers and to explain the experimental data.

Numerical and analytical approaches to plasma density determination from the ion current to cylindrical Langmuir probe are validated on hairpin probe measurements. An argon inductively coupled plasma discharge in a pressure range from 4.5 mTorr to 27 mTorr is studied. The discharge input power is varied in the range from 200 to 800 W, giving a plasma density in the range from 10 9 to 10 11 cm −3 . The approaches used for plasma density determination are analytical collisionless orbital motion limit theory, fluid semianalytical model of ion radial motion with ion collisions and particle-in-cell with a Monte Carlo collisions model of ion current collection by the cylindrical Langmuir probe. The relative error of different models is shown. The ion collisions should be taken into account, even at relatively low pressures, in order to get a reliable plasma density value from the ion current to the Langmuir probe.

Atomic layer plasma technologies require localizing ions' impact within nanometers up to an atomic layer. The possible way to achieve this is the decrease in the ion energy up to surface binding energy. At such low ion kinetic energies, the impact of different plasma effects, causing the surface modification, can be of the same order as kinetic ones. In this work, we studied the sputtering of amorphous silicon films by Ar+, Kr+, and Xe+ ions at energies of 20–200 eV under the low-pressure inductively coupled plasma discharge in pure argon, krypton, and xenon, respectively, at a plasma density of 1–1.5 × 1010 cm−3. Under the plasma conditions, a high asymmetry of discharge allowed to form ion flux energy distribution functions with narrow energy peak (5 ± 2 eV full width at half maximum). Real time in situ control over the ion composition and flux as well as the sputtering rate (the ratio of the film thickness change to the sputtering time) provided accurate determination of the sputtering yields Y(Ei). It is shown that at ion energy above ∼70 eV, the “classical” kinetic sputtering mechanism prevails. In this case, Y(Ei) grows rather rapidly with ion energy, increasing with the decrease in the ion mass: the closer the ion mass to the target atom mass, the higher the Y(Ei). Below 70 eV, the growth of Y(Ei) strongly slows down, with Y(20eV) being still high (>10−3), indicating the impact of plasma. The obtained trends of Y(Ei) are discussed in light of surface modification studied by atomic force microscopy and angular x-ray photoelectronic spectroscopy.

The chemical kinetics of oxygen atoms and ozone molecules were investigated in a fully-modulated DC discharge in pure oxygen gas in a borosilicate glass tube, using cavity ringdown spectroscopy (CRDS) of the optically forbidden O(P-3(2))?O(D-1(2)) absorption at 630 nm. Measurements were made over a range of tube temperatures (10 degrees C and 50 degrees C) gas pressures (0.5-4 Torr) and discharge current (10-40 mA). The discharge current was square-wave modulated (on for 0.2 s and off for 1 s), allowing the build-up to steady-state and the decay in the afterglow to be studied. This paper focusses on the afterglow period. The O atom density decays non-exponentially in the afterglow, indicating a surface loss probability dependent on incident active particle fluxes. The oxygen atom absorption peak lies on a time-varying absorption continuum due (in the afterglow) to the Chappuis bands of ozone. The ozone density passes through a maximum a few 100 ms into the afterglow, then decays slowly. An existing time-resolved self-consistent 1D radial model of O-2 positive column discharges was modified to interpret the new results. The ozone behaviour in the afterglow can only be modelled by the inclusion of: (1) surface production of O-3 from the reaction of O-2 molecules with adsorbed O atoms, (2) reactions of vibrationally-excited ozone with O atoms and with O-2(a(1)?(g)) molecules, and (3) surface loss of ozone with a probability of around 10(-5).

Modification of spin-on-deposited porous PMO(periodic mesoporous organosilica) ultralow-k(ULK) SiCOHfilms (k= 2.33) containing both methyl terminal and methylenebridging groups by vacuum ultraviolet (VUV) emission from Xeplasma is studied. The temporal evolution of chemical composition,internal defects, and morphological properties (pore structuretransformation) is studied by using Fourier transform infraredspectroscopy, in situ laser ellipsometry, spectroscopic ellipsometry,ellipsometric porosimetry (EP), positron-annihilation lifetimespectroscopy (PALS), and Doppler broadening positron-annihila-tion spectroscopy. Application of the different advanced diagnosticsallows making conclusions on the dynamics of the chemical composition and pore structure. The time frame of the VUV exposure inthe current investigation can be divided into two phases. During thefirst short phase,film loses almost all of its surface methyl andmatrix bridging groups. An increase of material porosity due to removal of methyl groups with simultaneous matrix shrinkage isfound by in situ ellipsometry. The removal of bridging bonds leads to an increase of matrix intrinsic porosity. Nevertheless, when thetreated material is exposed to the ambient air, the sizes of micro- and mesopores and pores interconnectivity decrease with the VUVexposure time according to PAS and EP data. The last is the result of the additionalfilm shrinkage caused by atmosphere exposure.During the second phase the increase of mesopore size is detected by both EP and PAS. The increase of mesopore size goes all thetime as it is expected from in situ ellipsometry, but it is masked by the air exposure.

Radio-frequency (rf) plasma with additional ionization by an electron beam (EB) is considered as a possible method for the independent control of plasma density, mean electron energy and mean ion energy. In this study, spatial transition from EB to rf-power-controlled dual-frequency capacitively coupled plasma (DFCCP) was studied using the following movable diagnostics: Langmuir and hairpin probes, a retarding field energy analyzer and optical emission spectroscopy. The beam (1.1–1.4 keV) is generated by a runaway EB module placed near the plasma chamber wall, while the plasma transition is caused by EB degradation with the distance from the EB module. The study was conducted in Ar at 200 and 400 mTorr gas pressures in 81 and 12 MHz DFCCP. When the EB is on, a significant decrease in the mean electron energy is observed, from 6 eV in the rf plasma down to 0.2–0.8 eV in the EB plasma. The EB also changes the shape of the electron energy probability function, from Druyvesteyn-like in rf plasma to Maxwellian-like. When both EB and rf power are applied, the mean electron energy increase and the electron density decrease, with the distance from the EB module, are observed due to the beam degradation. The ion energy distribution at the bottom electrode in rf plasma peaks at 25–30 eV and shifts down to a few eV in EB plasma. As in conventional DFCCP, the ion energy distribution can be fine-tuned by the application of a low-frequency rf bias. However, the use of an EB allows us to reduce the range of ion energies down to a few eV, which cannot be achieved in conventional rf discharges.

Effects of hydrogen atoms and UV radiation (λ > 210 nm) on nanoporous organosilicate glass (OSG) low-k films are studied in the temperature range from 20 °C to 300 °C. The purpose of the study is to understand the mechanisms of low-k films modification that can happen during the cleaning from carbon containing residues formed from sacrificial porogen and accumulated during the air storage. It is shown that exposure of low-k films to hydrogen atoms at low temperature leads to slight modification of hydrocarbon bonds in hydrocarbon residues not bonded to Si. At high temperature (T ⩾ 300 °C), the relative concentration of –CH x bonds changes in a complex way and depends on the amount and structure of the carbon-containing compounds. The general trend is relatively rapid decrease of –CH2 bonds concentration, while the terminal –CH3 groups are more stable. Temperature also initiates the reaction of hydrogen atoms with low-k with partial modification of low-k matrix breaking Si–O bonds. The destruction of Si–O and Si–CH2 groups leads to the formation of oxygen-deficient centers, followed by the formation of Si–(CH3)2 groups due to their interaction with methyl groups. At 300 °C, the total number of Si–CH3 + Si–(CH3)2 groups starts to decrease indicating on partial removal of the methyl groups bonded to silicon. Besides with increasing temperature a slight modification of the structure of matrix under exposure to H atoms is also observed. UV radiation has almost no effect on these processes in the studied conditions. Thus, there exist the ‘optimal’ conditions for H atom impact on OSG low-k films which allows improving film performance by removing porogen residue without damage.

One of the crucial challenges facing modern microelectronics is to provide plasma surface treatment at the single atomic level. To minimize defects in the underlying layers, these processes require ions with very low energies—lower than in conventional radio-frequency (rf) plasma and close to the binding energy of atoms. A conventional rf dual-frequency capacitively coupled plasma (df CCP) discharge with additional ionization by an electron beam is considered as a possible solution to this problem. This paper contains a study on the electron beam effect on 81 & 12 MHz plasma parameters such as electron energy probability function, plasma density, electron temperature and ion energy distribution at an rf-biased electrode. The experimental part of the study includes measurements carried out in an asymmetric rf df CCP discharge in Ar at 100 mTorr pressure using a Langmuir probe, a hairpin-probe, and a retarding field energy analyzer. The behavior of plasma parameters is considered in the different types of plasma: electron beam plasma, when no rf power is applied, as well as rf plasma with and without an electron beam. The 1D PIC MCC simulation is used to analyze the effect of an electron beam on the df rf plasma. The obtained results showed that the electron temperature and, accordingly, the energy of ions coming at the electrode surface can be lowered. The use of an electron beam in a df CCP discharge allows to control the plasma density, electron temperature and ion energy spectrum in the low-energy range, which can be of essential interest for atomic layer etching and atomic layer deposition technologies.

The paper presents the results of the experimental study of O, N, and H atom interaction with ultra-thin MoS 2 films demonstrating changes in properties of the surface layer of samples under investigation. Keywords: quasi-two-dimensional materials, molybdenum disulfide, plasma, ions, surface modification.

We present a detailed study of the density and kinetics of O-2(b(1)sigma(g) (+)) in steady-state and partially-modulated DC positive column discharges in pure O-2 for gas pressures of 0.3-10 Torr and 10-40 mA current. The time-resolved density of O-2(b(1)sigma(g) (+)) was determined by absolutely-calibrated optical emission spectroscopy (OES) of the A-band emission at 762 nm. Additionally, the O-2(b(1)sigma(g) (+)) density was determined by VUV absorption spectroscopy using the Fourier-transform spectrometer at the DESIRS beamline at Synchrotron Soleil, allowing the absolute calibration of OES to be confirmed. The O(P-3) atoms were detected by time-resolved sub-Doppler cavity ringdown spectroscopy (CRDS) using the O(P-3(2)) -> O(D-1(2)) transition at 630 nm. The CRDS measurements were synchronized to the discharge modulation allowing the O(P-3) dynamics to be observed. As a function of gas pressure the O-2(b(1)sigma(g) (+)) density passes through a maximum at about 2 Torr. Below this maximum, the O-2(b(1)sigma(g) (+)) density increases with discharge current, whereas above this maximum it decreases with current. The gas temperature increases with pressure and current, from 300 to 800 K. These observations can only be explained by the existence of fast quenching process of O-2(b(1)sigma(g) (+)) by O(P-3), with a rate that increases strongly with gas temperature, i.e. with a significant energy barrier. The data are interpreted using a 1D self-consistent model of the O-2 discharge. The best fit of this model to all experimental data (including the O-2(b(1)sigma(g) (+)) average density as a function of pressure and current, the radial profiles, and the temporal response to current modulation) is achieved using a rate constant of k (Q) = 10(-10) exp(-3700/T) cm(3) s(-1).

The paper presents the results of the experimental study of O, N, and H atom interaction with ultra-thin MoS2 films demonstrating changes in properties of the surface layer of samples under investigation

Ion-assisted surface processes are the basis of modern plasma processing. Ion energy distribution (IED) control is critical for precise material modification, especially in atomic-level technologies such as atomic layer etching. Since this control should be done in real time, it requires real-time feedback using fast process sensors. In the general case of an industrial plasma reactor, when direct IED measurement is not possible, the IED can be estimated using the concept of a virtual IED sensor. In this paper, a similar virtual IED sensor is considered using an asymmetric dual-frequency (df) rf CCP discharge as an example. It is based on a fast calculation method of the IED at an rf-biased electrode. This approach uses the experimentally measured sheath voltage waveform and plasma density (or ion flux) as input data, and also includes Monte-Carlo simulation of ion motion in the sheath to take into account the effect of ion-neutral collisions. To validate this approach, experiments were carried out using various plasma diagnostics in several gases: argon and xenon as examples of plasma with atomic ions and nitrogen as an example of plasma with molecular ions. It is shown that in all cases it is possible to obtain an adequate IED estimation, close to the experimental one, in a reasonably short time ( tens of seconds when using a modern PC). The results obtained demonstrate the possibility of using a virtual IED sensor in real plasma processing.

Vacuum ultraviolet (VUV) flux of argon plasma radiation in a DC magnetron discharge with a plane circular titanium cathode is measured. It is found that the intensity of VUV radiation, mainly indicated by the resonance lines of argon atoms at 104.8 and 106.7 nm and ions at 92 and 93.2 nm, is proportional to the discharge current and decreases with pressure. Following the results of the measurements, a numerical model of resonance radiation transport is developed to determine the VUV flux to the substrate placed near the sputtering cathode where direct measurements are impossible due to the fast contamination of the detector by sputtered atoms. In the case of a substrate located 10 cm opposite the cathode surface, the upper limit of estimated VUV flux is of the order of 10(15) photons cm(-2) s(-1) at a coating deposition rate of 1.5 nm s(-1) for 2 and 12 mTorr gas pressures. Based on the measurements, the damage to a porous low-k dielectric by VUV radiation during the deposition of barrier layers in the DC magnetron discharge is first estimated.