E.L. Tsakadze

Low-frequency, high-density, inductively coupled plasma sources: Operation and applications

Operation regimes, plasma parameters, and applications of the low-frequency (∼500 kHz) inductively coupled plasma (ICP) sources with a planar external coil are investigated. It is shown that highly uniform, high-density (ne∼9×1012 cm−3) plasmas can be produced in low-pressure argon discharges with moderate rf powers. The low-frequency ICP sources operate in either electrostatic (E) or electromagnetic (H) regimes in a wide pressure range without any Faraday shield or an external multipolar magnetic confinement, and exhibit high power transfer efficiency, and low circuit loss. In the H mode, the ICP features high level of uniformity over large processing areas and volumes, low electron temperatures, and plasma potentials. The low-density, highly uniform over the cross-section, plasmas with high electron temperatures and plasma and sheath potentials are characteristic to the electrostatic regime. Both operation regimes offer great potential for various plasma processing applications. As examples, the efficie...

SYNTHESIS AND CHARACTERIZATION OF TERNARY AL-C-N COMPOUND

An attempt for modification of carbon nitride material by introduction of Al to form a ternary Al-C-N compound in a thin film deposited using inductively coupled plasma (ICP) assisted DC magnetron sputtering is reported. Optical emission spectroscopy (OES) is used for in-situ observation and identification of reactive species. The films were characterized using x-ray photoelectron spectroscopy (XPS) and x-ray diffraction spectroscopy (XRD). The results indicate that C-N bond is formed in the plasma. The XPS narrow scam spectra confirm the existence of C-Al, sp2C-N and sp3C-N bonds. Elemental proportion of carbon increases with the CH4/N2 flow rate ratio, and has a tendency to saturate. The film is dominated by c-AlN (111), mixed with Al4C3 and AlCN ternary compound.

CONTROL AND DIAGNOSTICS OF INDUCTIVELY COUPLED PLASMAS FOR CHEMICAL VAPOUR DEPOSITION ON NANOCOMPOSITE CARBON NITRIDE-BASED FILMS

Control and diagnostics of low-frequency (~ 500 kHz) inductively coupled plasmas for chemical vapor deposition (CVD) of nano-composite carbon nitride-based films is reported. Relation between the discharge control parameters, plasma electron energy distribution/probability functions (EEDF/EEPF), and elemental composition in the deposited C-N based thin films is investigated. Langmuir probe technique is employed to monitor the plasma density and potential, effective electron temperature, and EEDFs/EEPFs in Ar + N2 + CH4 discharges. It is revealed that varying RF power and gas composition/pressure one can engineer the EEDFs/EEPFs to enhance the desired plasma-chemical gas-phase reactions thus controlling the film chemical structure. Auxiliary diagnostic tools for study of the RF power deposition, plasma composition, stability, and optical emission are discussed as well.

Generation of uniform plasmas by crossed internal oscillating current sheets: Key concepts and experimental verification

The results of comprehensive experimental studies of the operation, stability, and plasma parameters of the low-frequency (0.46 MHz) inductively coupled plasmas sustained by the internal oscillating rf current are reported. The rf plasma is generated by using a custom-designed configuration of the internal rf coil that comprises two perpendicular sets of eight currents in each direction. Various diagnostic tools, such as magnetic probes, optical emission spectroscopy, and an rf-compensated Langmuir probe were used to investigate the electromagnetic, optical, and global properties of the argon plasma in wide ranges of the applied rf power and gas feedstock pressure. It is found that the uniformity of the electromagnetic field inside the plasma reactor is improved as compared to the conventional sources of inductively coupled plasmas with the external flat coil configuration. A reasonable agreement between the experimental data and computed electromagnetic field topography inside the chamber is reported. The Langmuir probe measurements reveal that the spatial profiles of the electron density, the effective electron temperature, plasma potential, and electron energy distribution/probability functions feature a high degree of the radial and axial uniformity and a weak azimuthal dependence, which is consistent with the earlier theoretical predictions. As the input rf power increases, the azimuthal dependence of the global plasma parameters vanishes. The obtained results demonstrate that by introducing the internal oscillated rf currents one can noticeably improve the uniformity of electromagnetic field topography, rf power deposition, and the plasma density in the reactor.

Diagnostics and Simulation of Low‐Frequency Inductively Coupled Plasmas

The results on the diagnostics and numerical modeling of low‐frequency (∼460 KHz) inductively coupled plasmas generated in a cylindrical metal chamber by an external flat spiral coil are presented. Experimental data on the electron number densities and temperatures, and optical emission intensities of the abundant plasma species in low/intermediate pressure argon discharges are included. The spatial profiles of the plasma density, electron temperature, and excited argon species are computed, for different RF powers and working gas pressures, using the 2D fluid approach. The model allows one to achieve a reasonable agreement between the computed and experimental data. The effect of the neutral gas temperature on the plasma parameters is also investigated. It is shown that neutral gas heating at higher (> 1 kW ) RF powers is among the key factors that control the electron number density and temperature. The dependence of the average RF power loss, per electron‐ion pair created, on the working gas pressure s...

CARBON BONDING STATES AND MECHANICAL PROPERTIES OF HYDROGENATED DLC FILMS DEPOSITED IN ELECTROSTATIC AND ELECTROMAGNETIC RF PLASMA MODES

Efficient hydrogenated diamond-like carbon (DLC) film deposition in a plasma reactor that features both the capacitive and inductively coupled operation regimes is reported. The hydrogenated DLC films have been prepared on silicon chemical vapor deposition (CVD) system. At low RF powers, the system operates as an asymmetric capacitively coupled plasma source, and the film deposition process is undertaken in the electrostatic (E) discharge regime. The films deposited in the electrostatic mode feature graphite-like structure. Above the mode transition threshold, the high-density inductively coupled plasma is produced in the electromagnetic (H) discharge regime. Raman spectrometry suggests the possibility to control relative proportions of sp2 and sp3 hybridized carbon. Variation of the DC substrate bias results in dramatic modification of the film structure from the polymeric (unbiased substrates) to the diamond-like (optimized bias). It has been shown that the deposition rate and hardness of the CH4+Ar gas mixture discharge, the DLC film exhibits mecha nical hardness of 18 GPa, Youngs modulus of 170 GPa, and compressive stress of 1.3 GPa.