Electron Cyclotron Resonance Argon Plasma Research Articles

Modification of transparent conductive ZnO and Ga-doped ZnO films by irradiation with electron cyclotron resonance argon plasma

By irradiating undoped ZnO and Ga-doped ZnO (GZO) films with electron cyclotron resonance Ar plasma, their electrical and optical properties have been modified. Both the carrier concentration and the Hall mobility increased with continuous irradiation in conductive ZnO films with a defect-rich crystalline lattice. Improved crystallinity was verified by intensifying the ZnO(002) x-ray diffraction peak and increasing the optical transmission level in the visible wavelength. This observation suggests network rearrangement through Zn atoms at interstitials or grain boundaries being oxidized or accommodated into the crystalline network. For insulating ZnO films that contain a sufficient number of oxygen atoms, the changes were better scaled with sheet resistance rather than resistivity. The interference fringes redshifted without lowering the transmittance level. Here, Ar ion impact will create oxygen vacancy donors in the near-surface region or desorb interstitial oxygen atoms that act as donor killers. In contrast, GZO films with resistivities in the 10−4 Ω cm range revealed little changes because there were very few imperfections in the crystalline lattice. The reduced amount of resistivity corresponded to the creation of oxygen vacancies in more resistive GZO films in the 10−3 Ω cm range.

Spectroscopic study on the evolution of graphite ablation plume in ECR argon plasma during the deposition of diamond-like carbon films

A spectroscopic study of carbon plume produced by pulsed laser ablation of a graphite target in argon plasma generated by electron cyclotron resonance (ECR) microwave discharge has been carried out in an attempt to clarify the processes involved in ECR argon plasma assisted pulsed laser deposition of diamond-like carbon (DLC) films. Optical emission spectroscopy measurements show that the plume exhibits different behaviors in its space distribution and time evolution when produced and expanding in argon plasma compared with the plume in vacuum or low-pressure argon ambient. In vacuum or low-pressure argon ambient, lines from carbon atoms and ions dominate the plume emission. In argon plasma, the emission evolves from consisting of lines from carbon atoms and ions to being dominated by bands from dimer C 2, with the strong C 2 bands governing the plume emission at the later stages of the plume expansion. The differences in the plume emission reveal the different gaseous species composing the plumes expanding in different environments, suggesting the different gaseous precursors for film deposition by PLD with or without the assistance of argon plasma. It was also found that the emissions of C 2 Swan bands and C 2 Deslandres D'Azembuja bands exhibit different space distribution.

Diamond-like carbon thin films prepared by ECR argon plasma assisted pulsed laser deposition

Diamond-like carbon films were prepared by pulsed laser ablation of graphite target in argon plasma produced from electron cyclotron resonance (ECR) microwave discharge and analyzed by Raman spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The analysis shows that the films prepared with argon plasma assistance have different chemical structure compared with the films prepared in vacuum without plasma assistance. The structure of the films prepared with plasma assistance depends strongly on the bias voltages applied on the substrate. Surface morphology observation shows that the films prepared with argon plasma assistance have a smoother surface than the films prepared without plasma assistance. The re-sputtering of the growing film due to the bombardment of the plasma stream results in reduction of the deposition rate. The ablation plumes during film preparation with and without plasma assistance were examined through optical emission spectroscopy. In vacuum, emission lines from mono-atomic carbons and carbon ions dominate the plume emission. In argon plasma, the plume emission exhibits different behavior in its temporal and spatial evolution. It is initially dominated by strong lines from mono-atomic carbons and carbon ions and then evolves to consist mainly of emissions from C 2 molecules superposed on a featureless continuum. It is also found that the emission intensity of the C 2 molecules as well as the continuum varies with the bias voltages.

Measurement of metastable state densities and electron temperatures in an electron cyclotron resonance argon plasma

The number of metastable state densities obtained ranges from 1×1015to 4×1015 m-3 in the electron cyclotron resonance (ECR) argon plasma by measuring the optical absorption of the 8115 nm spectral line under the conditions of 02—08 Pa and 500—800 W. Taking into account the c ontribution of both the ground state and the 1s5 metastable state to the emiss ions, the electron temperature Te is measured by the ratio of emissio n lines. Results show that there are obvious differences compared with only considering t he metastable state densities.

Hybrid PIG?ECR discharge as low-pressure sputtering system

The paper reports on a cold-cathode Penning ionization gauge (PIG) discharge ignited and sustained by microwave electron cyclotron resonance argon plasma at pressures below 0.01 Pa. The discharge was created in a 20-cm-diam PIG anode with a length-to-diameter ratio of two. The experimental data show that the discharge exists in a high-current discharge mode with a considerable cathode fall and a weak anode fall. The measurements of the discharge current and plasma parameters as a function of the discharge parameters are reported. The mechanism of the discharge and its possible applications are discussed.

Hybrid PIG–ECR discharge as low-pressure sputtering system

The paper reports on a cold-cathode Penning ionization gauge (PIG) discharge ignited and sustained by microwave electron cyclotron resonance argon plasma at pressures below 0.01 Pa. The discharge was created in a 20-cm-diam PIG anode with a length-to-diameter ratio of two. The experimental data show that the discharge exists in a high-current discharge mode with a considerable cathode fall and a weak anode fall. The measurements of the discharge current and plasma parameters as a function of the discharge parameters are reported. The mechanism of the discharge and its possible applications are discussed.

Maximum x-ray energy from compact electron cyclotron resonance based source of x rays

The x-ray spectra from an electron cyclotron resonance argon plasma produced in a compact magnetic trap, containing a tungsten target, are reported. The maximum attainable x-ray energy was recorded for different magnetic field configurations and energies higher than 300 keV were found. The maximum x-ray energy is strongly peaked near the change of the resonance surface topology from a one sheet hyperboloid to a two sheet hyperboloid. This observation is explained theoretically. Different regimes of x-ray production are described. Two distinct pressure ranges where x rays are produced were found. The characteristic lines of metals, e.g., from the target (tungsten), protection (lead), are clearly resolved. The radiography of an integrated circuit is shown as an example of possible use of the x-ray source for nondestructive control.

Zinc ionization by interaction with argon plasma

A low-temperature zinc plasma was generated by secondary ionization using an electron cyclotron resonance argon plasma. The ionization efficiency of zinc samples of the metal, the bromide, and the iodide were examined at different sample crucible temperatures. It was found that the ionization rate of zinc metal is the highest among the tested samples. The observed reaction rate constants , defined as = nZn+/nZnnAr+ in the present work, are 1.8 × 10-18 m-3, 1.7 × 10-19 m-3 and 3.7 × 10-19 m-3 for zinc metal, zinc bromide, and zinc iodide, respectively. The large reaction constant of zinc metal may be due to the small dissociation energy into atom vapour, compared with the large dissociation energies of the zinc halides.

Monte Carlo simulations of argon ion transport in the downstream region of electron cyclotron resonance plasmas

A Monte Carlo method to simulate the plasma characteristics of an electron cyclotron resonance (ECR) microwave discharge system is presented. We use the method to predict the ion behavior in the downstream region of an ECR argon plasma. The pressure and space dependences of the plasma potential, the effects of gas pressure on the ion velocity and angle distribution and the evolution of distributions are examined and discussed in detail. Our results of the simulation show that the ion parallel velocity distribution appears to be bimodal and is strongly dependent on the gas pressure, whereas the ion perpendicular velocity distribution is mainly determined by the applied magnetic field, and the ion beam tends to be parallel to the magnetic field.

Undriven periodic plasma oscillation in electron cyclotron resonance Ar plasma

We report experimental observation of periodic oscillation in a steady state electron cyclotron resonance argon plasma that is not driven by extra periodic forces. We interpret the oscillation according to the predator-prey model, which is a nonlinear plasma-neutral coupling in the plasma production region. The oscillation is observed in a narrow plasma parameter window and is evidence for neutral density depletion in a high density plasma system.

Enhanced production of multicharged boron ions by approaching a boride target to an ECR zone

Multicharged boron ions have been produced by a sputtering boride target in a 2.45-GHz electron cyclotron resonance (ECR) source. The target material is immersed in an ECR argon plasma along the geometrical axis of the mirror field, and dc bias voltages are applied. Extracted boron ion currents increase as the target approaches the ECR zone formed at the bottom of mirror trap although the argon charge state deteriorates. The increase of boron ion current is coincident with that of the solid angle subtended by the target at the ECR zone. Measurement of the boron flux shows that the increase of boron atoms sputtered into the ECR zone causes this enhanced production. Ratio of total boron to argon ion current and that of B2+ to B+ current are about 10% and 10%–20%, respectively. The B3+ current can be detected at low microwave power (∼150 W). The isotopes of boron are clearly separated in natural abundance ratio.

Study of gate oxide damage in an electron cyclotron resonance argon plasma

Charging damage of thin gate oxides is often a concern in plasma processing. This study examines the breakdown voltage characteristics of thin gate oxides in low-energy argon plasmas. An electron cyclotron resonance (ECR) system with a rf-biased electrode was used. The effects of rf bias, plasma exposure time, and gate oxide thickness on the gate oxide breakdown voltage were measured. The results show that the ECR plasma process with low, self-induced dc bias does not induce any charging damage for gate oxides as thin as 120 Å. More device failures are produced with higher bias and longer plasma exposure, while thicker gate oxides show less damage.

Etching of SiO2 in an electron cyclotron resonance argon plasma

Etching of SiO2 with low-energy Ar ions has been studied in an electron cyclotron resonance (ECR) based etching system. Ion energies were controlled by a capacitively coupled 13.56 MHz bias of the substrate. Etch rates of over 100 Å/min have been achieved at ion energies below 100 V. The variation in etch rate has been studied as a function of ECR power, self-induced bias, and position of the wafer relative to the ECR source. This low-energy process can be utilized for cleaning of semiconductor surfaces prior to chemical vapor deposition or metallization processes.