Electron Cyclotron Resonance Hydrogen Research Articles

Hydrogen Plasma under Conditions of Electron-Cyclotron Resonance in Microelectronics Technology

This paper presents the results of hydrogen electron-cyclotron resonance (ECR) plasma in micro-electronics technology. Its effect on the radiation resistance of the IC and on the quality of the ohmic contact during the formation of UBM metallization is demonstrated. The devices obtained with the use of plasma ECR and without it are analyzed.

Radiation hardness of bipolar transistor based integrated circuits improved by ECR hydrogen plasma treatment and Si-wafers gettering

We demonstrate significant improvement of the radiation immunity of the integrated circuits based on silicon bipolar transistors. Strong decrease of the current gain degradation and significant yield improvement after high-energy gamma irradiation are both shown. This was achieved by development of efficient hydrogenation process for the silicon bulk and the surface dielectric layer using electron cyclotron resonance (ECR) plasma, as well as implementation of effective Si-wafer gettering option. Keywords: integrated circuits, bipolar transistors, ECR-plasma, hydrogenation of semiconductor structures, trap state passivation, gettering of semiconductor wafers, γ-irradiation, radiation hardness, yield of workable transistors.

Qualification of uniform large area multidipolar ECR hydrogen plasma

The design and characterization of a multi-dipolar microwave electron cyclotron resonance (ECR) hydrogen plasma reactor are presented. In this configuration, 16 ECR sources are disposed uniformly along the azimuthal direction at a constant distance from the center of a cylindrical reactor. Several plasma diagnostics have been used to determine key parameters such as neutral species temperature; electron density and temperature; and H+, H2+, and H3+ ion energy distributions. The experimental characterization is supported by electromagnetic and magnetostatic field simulations as well as Particle In-Cell Monte Carlo Collisions simulations to analyze the observed ion energy distribution functions. Especially, we show that both electron density and temperature are spatially uniform, i.e., 1011 cm−3 and 3 eV, respectively. This plasma enables generating ion flux and energy in the ranges 1019–1022 ions m−2 s−1 and few keVs, respectively. The H2+ ion distribution function shows two populations which were attributed to surface effects. These features make this reactor particularly suitable for studying hydrogen plasma surface interaction under controlled conditions.

High power vacuum ultraviolet source based on gasdynamic ECR plasma

We report experimental results of vacuum ultraviolet (VUV) emission from the plasma of an electron cyclotron resonance (ECR) discharge in hydrogen, sustained by millimeter-wavelength radiation of a gyrotron. The considered discharge is characterized with the high plasma density (1013 cm−3 order of magnitude) and, at the same time, the high electron average energy (10–300 eV), which makes it possible to significantly increase the efficiency of VUV re-emission of the energy deposited into the plasma by the microwave radiation. Experiments were performed with the plasma confined in a simple mirror trap and heated by pulsed gyrotron radiation of 37.5 GHz/100 kW under the ECR condition. The measured volumetric VUV emission power of Lyman-alpha line (122 10 nm) overlapping with the Werner band, Lyman band (160 10 nm), and molecular continuum (180 20 nm) reached 45, 25, and 55 W/cm3, respectively. The total absolute radiation power in these three ranges integrated over the plasma volume is estimated to be 22 kW, i.e., 22% of the incident microwave power, which matches theoretical predictions. The development of effective technological VUV sources of a kilowatt power level is expected to be the next step following the optimization of the conditions of the ECR hydrogen discharge sustained by powerful gyrotron radiation.

Measurements of electron energy distribution on electron cyclotron resonance plasma operated with hydrogen gas

This article deals with the production of electron cyclotron resonance hydrogen plasma in a closed gas chamber called Menja device. For this purpose, 2.45 GHz frequency and various power i.e. 0 - 500 W are employed. The flow of hydrogen gas is controlled manually with the range 1.5 – 10 sccm maintaining pressure range 10-5 – 10-4 mbar. The Langmuir probe technique is used to drag the electrons and ions by biasing the probe positively and negatively to study the key parameters such as ion saturation current, floating potential, plasma potential, electron temperature and plasma density. Besides these, to obtain information on electron energies and their interaction with plasma, the electron energy distribution function (EEDF) has been studied with the help of 2nd derivative of current obtained from the differentiator. For this purpose, an analogue differentiation circuit was built and tested.

Atomic and Electronic Structure of SiOx Films Obtained with Hydrogen Electron Cyclotron Resonance Plasma

The silicon oxide thin films obtained by thermal SiO2 treatment in hydrogen electron cyclotron resonance plasma at various exposure times are investigated. Using X-ray photoelectron spectroscopy, we have established that such treatment leads to a significant oxygen depletion of thermal SiO2, the more so the longer the treatment time. The atomic structure of the SiOx < 2 films obtained in this way is described by the random bonding model. The presence of oxygen vacancies in the plasma-treated films is confirmed by comparing the experimental valence band photoelectron spectra and those calculated from first principles, which allows the parameter x to be estimated. We show that thermal silicon oxide films treated in hydrogen plasma can be successfully used as a storage medium for a nonvolatile resistive memory cell.

Optical Properties of the SiOx (x &lt; 2) Thin Films Obtained by Hydrogen Plasma Processing of Thermal Silicon Dioxide

The optical properties and composition of thermal silicon oxide thin films processed in a hydrogen electron cyclotron resonance plasma have been studied by ellipsometry, quantum-chemical modeling, and photoluminescence spectroscopy. It has been found that the plasma processing of the films leads to their oxygen depletion and the formation of nonstoichiometric oxide SiOx < 2. The parameter x of the obtained SiOx films has been determined by comparing the experimental spectral dependence of the refractive index with the dependence obtained theoretically using the ab initio calculation. It is shown that an increase in the time of processing of thermal dioxide SiO2 in a hydrogen plasma leads to an increase in the refractive index of the film, as well as in the degree of its oxygen depletion. The dependence of the parameter x of the investigated films on the hydrogen plasma processing time is plotted.

Phonon-assisted electron tunneling between traps in silicon oxide films treated in hydrogen plasma

The charge transport in thin thermal silicon oxide films treated in electron cyclotron resonance hydrogen plasma at different exposure times was investigated. X-ray photoelectron studies show that such treatment leads to the oxygen deficiency of the films. It was established that the treatment of the films in plasma leads to an increase of their conductivity by a factor of about 102. The film charge transport properties were studied at different temperatures and analyzed within four theoretical dielectric conductivity models. It was found that the charge transport mechanism is described by Fowler-Nordheim model in the initial silicon oxide and by the model of phonon-assisted electron tunneling between neutral traps after the treatment in hydrogen plasma. The thermal trap ionization energy value (Wt = 1.6 eV) measured from transport experiments is in agreement with that obtained from ab initio calculations for the oxygen vacancy (Si-Si bond) in SiO2.

Surface modification influenced properties of silicon nanowires grown by Ag assisted chemical etching with ECR hydrogen plasma treatment

Silicon nanowires (SiNWs) are fabricated by Ag assisted chemical etching and are treated with hydrogen plasma created by electron cyclotron resonance (ECR) plasma system at 600 watts microwave power for various time durations (0–30 min). The hydrogen plasma exposure on the surface of the SiNWs reduced the surface roughness and increased the crystalline nature. SEM analysis revealed that the diameter of the SiNWs decreased on plasma exposure. The electrical conduction measurements suggested that the hydrogen plasma exposure for 5 min on the SiNW surface enhanced the electrical conductivity when compared to as fabricated SiNW surface. The hydrophobic nature of fabricated SiNWs was transformed to hydrophilic at plasma exposure for lower time duration. On plasma exposure of NWs for 30 min the sample turned hydrophobic. Study of different properties of the SiNWs before and after plasma treatment revealed that there is pronounced effect of plasma on the nature of SiNWs.

Оптические свойства тонких пленок SiO-=SUB=-x-=/SUB=- (x&amp;lt;2), полученных обработкой термического диоксида кремния в водородной плазме

Using the methods of ellipsometry, quantum chemical modeling, and photoluminescent spectroscopy, the optical properties and composition of thin films of thermal silicon oxide processed in a hydrogen electron-cyclotron resonance plasma are studied. It has been established that treatment of films in plasma leads to their depletion in oxygen and the formation of non-stoichiometric oxide SiOx &lt;2. By comparing the experimental spectral dependence of the refractive index with the theoretically calculated from the first principles, the values ​​of the parameter x in the obtained SiOx films are determined. It was shown that an increase in the processing time of thermal SiO2 in hydrogen plasma leads to an increase in the refractive index of the film, as well as the degree of depletion of the film with oxygen. For the studied films, the dependence of the value of the parameter x on the treatment time in a hydrogen plasma is constructed.

Hydrogen electron cyclotron resonance ion sources plasma characterization based on simple optical emission spectroscopy

Hydrogen electron cyclotron resonance ion sources plasma measurements based on simple optical emission spectroscopy on a new compact low current ion source designed and built by the authors is presented. By observing the plasma luminescence both directly and through a low-cost transmission diffraction grating, basic characterization of the Hydrogen plasma obtainable in the ion source is carried out. Through simple processing of CCD captures of these images, optimal values for the ion source relevant operation parameters, including RF power and frequency, and Hydrogen mass flow are easily obtained. Despite the simplicity of the method and its limited accuracy as compared to the use of a full standard optical spectrometric set-up, it is shown that the presented approach can cope with basic plasma diagnostic tasks as far as the successful operation of the ion source is concerned.

Study of hydrogen ECR plasma in a simple mirror magnetic trap heated by 75 GHz pulsed gyrotron radiation.

Plasma of electron cyclotron resonance (ECR) discharge sustained by millimeter wave radiation is widely used for production of ion beams of different kind. The main trend in ECR ion sources development nowadays is an increase of frequency and power of microwave heating. The most advanced systems use gyrotrons in 24-60 GHz frequency range. In previous studies at IAP RAS it was demonstrated that ECR source SMIS 37 (Simple Mirror Ion Source) with 37.5 GHz heating operating in quasigasdynamic regime of plasma confinement is able to produce proton and deuteron beams with ion current density about 700 mA/cm2. As the next step of these investigations plasma properties of the discharge sustained by 75 GHz radiation have been studied. Plasma density and electron temperature were determined using spectroscopic and Langmuir probe techniques. It was demonstrated that plasma density could reach values close to 1014 cm-3 and that is of great interest for further development of high current ion sources for various applications.

Strongly Eccentric Rotational Plasma Lamina Observed in a 2.45-GHz Hydrogen Discharge

A novel strongly eccentric rotating plasma lamina structure subtending approximately an angle of 120° is reported in a 2.45-GHz driven electron cyclotron resonance hydrogen discharge in the proximity of the chamber wall. Shape and rotation frequencies depend critically on the embedded magnetic field distribution in the plasma chamber as well as on neutral gas pressure and microwave power. The discharge denominated test-bench for ion-sources plasma studies includes a transparent doubled shielded quartz window that keeps the microwave resonance condition. An ultrafast microchannel plate charge-coupled device frame camera is used to obtain four pictures of 1- $\mu \text{s}$ exposure time each during a single plasma pulse in the visible emission range. $ {E} \times {B}$ drift is pointed as that responsible for driving the rotational behavior of a thick plasma sheath, where the scale of the quasi-neutrality breaking is estimated ten times greater than that in a typical plasma sheath.

Passivation of SiO2/4H–SiC interface defects via electron cyclotron resonance hydrogen–nitrogen mixed plasma pretreatment for SiC surface combined with post-oxidation annealing

We proposed an electron cyclotron resonance microwave hydrogen–nitrogen mixed plasma (HNP) pretreatment for 4H–SiC surface combined with post-oxidation annealing (POA) to improve the SiO2/SiC interface properties. Results revealed that HNP surface pretreatment effectively reduced the density of interface traps (Dit), which was closely correlated with interface flattening because of surface flattening, surface state (contaminants, adsorbates, and dangling bonds) reduction, and suppressed generation of interface defects during oxidation. Combined with POA, Dit was further decreased because of passivation of the formed defects after oxidation. The correlation among passivation, SiC surface properties, SiO2/SiC interface properties, and defect levels was established.

Influence of microwave driver coupling design on plasma density at Testbench for Ion sources Plasma Studies, a 2.45 GHz Electron Cyclotron Resonance Plasma Reactor

A comparative study of two microwave driver systems (preliminary and optimized) for a 2.45 GHz hydrogen Electron Cyclotron Resonance plasma generator has been conducted. The influence on plasma behavior and parameters of stationary electric field distribution in vacuum, i.e., just before breakdown, along all the microwave excitation system is analyzed. 3D simulations of resonant stationary electric field distributions, 2D simulations of external magnetic field mapping, experimental measurements of incoming and reflected power, and electron temperature and density along the plasma chamber axis have been carried out. By using these tools, an optimized set of plasma chamber and microwave coupler has been designed paying special attention to the optimization of stationary electric field value in the center of the plasma chamber. This system shows a strong stability on plasma behavior allowing a wider range of operational parameters and even sustaining low density plasma formation without external magnetic field. In addition, the optimized system shows the capability to produce values of plasma density four times higher than the preliminary as a consequence of a deeper penetration of the magnetic resonance surface in relative high electric field zone by keeping plasma stability. The increment of the amount of resonance surface embedded in the plasma under high electric field is suggested as a key factor.

Ultra-fast intensified frame images from an electron cyclotron resonance hydrogen plasma at 2.45 GHz: Some space distributions of visible and monochromatic emissions

First results from an ultra-fast frame image acquisition diagnostic coupled to a 2.45 GHz microwave hydrogen discharge are presented. The plasma reactor has been modified to include a transparent doubled shielded quartz window allowing to viewing the full plasma volume. Pictures describing the breakdown process at 1 μs exposure time have been obtained for integrated visible light signal, Balmer-alpha, Balmer-beta lines, and Fulcher-band. Several different plasma emission distributions are reported. The distribution depends on the magnetic field configuration, incident microwave power, and neutral gas pressure.

Temperature and density evolution during decay in a 2.45 GHz hydrogen electron cyclotron resonance plasma: Off-resonant and resonant cases

Time resolved electron temperature and density measurements during the decay stage in a hydrogen electron cyclotron resonance (ECR) plasma are presented for a resonance and off-resonance magnetic field configurations. The measurements are conducted on a ECR plasma generator excited at 2.45 GHz denominated test-bench for ion-sources plasma studies at ESS Bilbao. The plasma parameters evolution is studied by Langmuir probe diagnostic with synchronized sample technique developed for repetitive pulsed plasmas with a temporal resolution of 200 ns in typical decay processes of about 40 μs. An afterglow transient is clearly observed in the reflected microwave power signal from the plasma. Simultaneously, the electron temperature evolution shows rebounding peaks that may be related to the interplay between density drop and microwave coupling with deep impact on the Electron Energy Distribution Function. The correlation of such structures with the plasma absorbed power and the coupling quality is also reported.

Evaluation of Absolute Flux of Vacuum Ultraviolet Photons in an Electron Cyclotron Resonance Hydrogen Plasma: Comparison with Ion Flux

We compared the absolute flux of positive ions with the flux of photons in a vacuum ultraviolet (VUV) wavelength range in an electron cyclotron resonance hydrogen plasma. The absolute flux of positive ions was measured using a Langmuir probe. The absolute flux of VUV photons was evaluated on the basis of the branching ratio between the Lyman and Balmer lines emitted from electronic states with the same principal quantum numbers. The absolute intensities of the Balmer lines were obtained by calibrating the sensitivity of the spectroscopic system using a tungsten standard lamp. It has been found that the flux of VUV photons is, at least, on the comparable order of magnitude with the positive ion flux, suggesting the importance of VUV photons in plasma-induced damage in fabrication processes of ultralarge-scale integrated circuits.

Evaluation of Absolute Flux of Vacuum Ultraviolet Photons in an Electron Cyclotron Resonance Hydrogen Plasma: Comparison with Ion Flux

Evaluation of Absolute Flux of Vacuum Ultraviolet Photons in an Electron Cyclotron Resonance Hydrogen Plasma: Comparison with Ion Flux

A comparison of nitrous oxide and hydrogen ECR plasma discharges for silicon solar cell passivation

The passivation of crystalline Si solar cells using nitrous oxide (N 2O) electron cyclotron resonance (ECR) plasma discharges has been studied and compared with ECR hydrogen passivation. The cells consisted of ECRCVD grown microcrystalline Si emitter layers on single crystal Si (sc-Si) and multicrystalline Si (mc-Si) substrates, without anti-reflective coatings or surface texturing. For cells on sc-Si substrates, hydrogen passivation is more effective at a substrate temperature of 300 °C and low microwave power (300 W). With increased power (500 W) H 2 is less effective than N 2O due to hydrogen plasma damage leading to a significant fall in the cell fill factor. In comparison with H 2, N 2O discharges lead to a significantly better (by > a factor of 2) improvement in the performance of cells on mc-Si substrates for treatment times of ≤15 min at a passivation temperature of 300 °C and 300 W microwave power. XPS measurements suggest that a surface oxide layer containing N and C atoms is formed by the N 2O plasma which, most likely, reduces the surface state density and, hence, carrier recombination.