A Comparative Study of Single and Double Langmuir Probe Techniques for RF Plasma Characterization (original) (raw)
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Langmuir probe measurement in a radio frequency inductively coupled argon plasma
2004
A Langmuir probe diagnostic system is constructed to measure the plasma properties in a radio frequency (RF) inductively coupled Argon plasma. A passive compensation is incorporated into the Langmuir probe to provide the high impedance to the probe tip in the fundamental drive frequency of 13.56 MHz. This will enable the probe tip to follow the RF fluctuation in the plasma and allows the “dc” probe characteristic to be measured. The properties of the RF inductively coupled Argon plasma are measured in the pressure range of 0.01 mbar–0.4 mbar and the RF incident power from 20 W–280 W. The radial and axial distributions of the RF Argon plasma are also studied. Comparison of the results from the Langmuir probes with compensation and without compensation demonstrates the effect of the compensating component.
Development of Simple Designs of Multitip Probe Diagnostic Systems for RF Plasma Characterization
Multitip probes are very useful diagnostics for analyzing and controlling the physical phenomena occurring in low temperature discharge plasmas. However, DC biased probes often fail to perform well in processing plasmas. The objective of the work was to deduce simple designs of DC biased multitip probes for parametric study of radio frequency plasmas. For this purpose, symmetric double probe, asymmetric double probe, and symmetric triple probe diagnostic systems and their driving circuits were designed and tested in an inductively coupled plasma (ICP) generated by a 13.56 MHz radio frequency (RF) source. Using I-V characteristics of these probes, electron temperature, electron number density, and ion saturation current was measured as a function of input power and filling gas pressure. An increasing trend was noticed in electron temperature and electron number density for increasing input RF power whilst a decreasing trend was evident in these parameters when measured against filling gas pressure. In addition, the electron energy probability function (EEPF) was also studied by using an asymmetric double probe. These studies confirmed the non-Maxwellian nature of the EEPF and the presence of two groups of the energetic electrons at low filling gas pressures.
2019
Langmuir probe is a powerful diagnostic tool for low pressure gas discharge plasmas, the ability of measurement of local plasma parameters and the electron energy distribution function (EEDF) makes it unique among other diagnostics. The Langmuir probe is consisting of small wire put in contact with the plasma thus measuring the current from the plasma at various applied voltages. We have fabricated Langmuir probe for the characterisation of RF produced plasma at SVITS, with calculated value of capacitor and inductor for the first and second Harmonics of frequency 13.56 MHz. A system has been designed, fabricated and installed at SVITS, Indore for producing tungsten coatings using Plasma Enhanced Chemical Vapor Deposition (PE-CVD) methodology. Variation of electron density with radial distance inside the plasma along the diameter of electrode ofRF Glow Discharge Argon Plasma will be discussed in this paper
RF plasma parameter determination by a Langmuir multipoint double probe array
Journal of Physics: Conference Series, 2012
A multipoint double Langmuir (MDL) probe system, which is exempt from interference, has been designed and assembled to be applied to an RF plasma. The system provides the measurement of fundamental plasma parameters such as density, temperature, plasma potential, etc. on the basis of the Bohm Approximation Theory and the Orbital Movement Limit. Thus, one pair of the MDL system is selected so as to consider the right plasma parameters within the prevailing pressure-power intervals. Both the hardware and software of the system have been applied to the modification of material properties by means of the PIII process.
Plasma parameters measurements by means of Langmuir probe
Radiation Effects and Defects in Solids, 2008
The Langmuir probe (LP) diagnostics is a powerful method for the evaluation of the plasma resistivity curve (I-V curve) and the characterization of the following plasma parameters: electron temperature, electron density, ion density, and plasma potential. In presence of a stable plasma it is possible to extrapolate the electron energy distribution function of the plasma electron population. Because of the long acquisition time (in the order of hundreds of msec or more), this method is suitable for cw plasmas in thermal equilibrium for which the physical properties vary in a time scale longer than the acquisition time. At INFN-LNS the LP diagnostics has been used in order to characterize the TRasco Intense Proton Source plasma, and the low temperature -high density plasmas of a plasma reactor designed for complex molecules dissociation. In the first case, it has been possible to evaluate the plasma properties for different magnetic field profiles and for several operating conditions. In the second case, the LP has permitted to characterize the plasma properties of the plasma reactor at different microwave powers and gas pressures, with the aim to find the optimal experimental conditions in terms of rate of molecules dissociation and of plasma stability and reliability. These series of measurements are here reported, together with measurements of the plasma reactor parameters. Finally, some considerations about the possibility to extend the LP diagnostics to the non-equilibrium plasmas in pulsed mode, as the plasmas obtained by means of laser ablation of solid targets, are given; the design of a possible experimental set-up is outlined.
International Journal of Applied Physics and Mathematics
Low temperature radio frequency plasma is widely used in low temperature plasma processing medium for material processing in many fields including microelectronics, aerospace, and the biology. For proper utilization of the process, it is very much important to know the plasma parameters. In this paper a technique is reported to determine the plasma parameters from the electrical discharge characteristic of a capacitivly couple radio frequency argon plasma. The homogeneous discharge model is modified to make it applicable in low pressure by incorporating the plasma series resonance effect. The effect on the plasma resistance by the change in drift velocity of the electron with rf electric filed is also considered. The electron density and temperature is found to be well agreed with the Langmuir probe diagnostic result, which is in the range of 0.5x10 10 to 4.5x10 10 cm-3 and 1.4 to 1.6 ev for wide range of rf power. Index Terms-Capacitive couple radio frequency plasma, discharge characteristic, homogeneous discharge model, plasma parameters, power balance.
Langmuir double probe RF plasma compensation using simulation method
The problem of Langmuir probe data deformation due to RF pickup by the probe is treated through a computer simulation method. It is pointed out that proper RF compensations can be obtained by treatment of the Langmuir probe raw data through the use of computer software. It is demonstrated that correct, RF unaffected probe I-V characteristics can be accurately reproduced from the RF contaminated data. This eliminates the need for the use of any filters or other hardware procedures. User friendly matlab based software is presented. The software automatically retrieves the correct RF I-V characteristics for single Langmuir probe data which consequently allows for proper evaluation of plasma parameters such as the plasma electron temperature, electron number density and the electron energy distribution function (EEDF)
A dc-pulsed capacitively coupled planar Langmuir probe for plasma process diagnostics and monitoring
Plasma Sources Science and Technology, 2012
An improvement to the RF-biased planar Langmuir probe technique proposed by Braithwaite et al (1996 Plasma Sources Sci. Technol. 5 67) is demonstrated, and applied to the case of an industrial CCP reactor. Compared with the RF-biased probe, the new technique uses dc pulses instead of RF bursts, which provides similar results but with simpler electronics. The ion fluxes determined by both techniques are compared under the same O 2 /Ar plasma conditions using available literature data for the RF-biased case. The data show not only the same trends but very close absolute values of ion fluxes for all studied plasma conditions after correcting for the chamber-area difference. Furthermore, the new technique has the additional benefit of providing information on the 'electron transition region' of the I -V curve, as well as allowing the resistance and capacitance of films deposited on the probe to be determined. Finally, both experimental data and numerical simulations of the I -V characteristics and the film parameters are presented for different oxidizing plasmas.
Computerized Langmuir probe measurements in a capacitively coupled RF discharge
A system of automated computerized Langmuir probe measurements is used in order to determine the plasma parameters in a plasma reactor constructed for cleaning of metallic artifacts by RF discharge. A compensated probe insures the suppression of the RF interference. The probe data are collected using a commercial data acquisition unit connected to a portable computer. The raw data are processed using wavelet transforms techniques which assures the denoising of the probe signal without distortion of the probe I-V characteristic. The first and second derivatives of the I-V characteristic are determined. The measurement of the electron density spatial distribution in the inter-electrode distance indicates a flat density profile in the middle region of the discharge.
Electron Density with Radial Distance in RF Glow Discharge Plasma Using Langmuir Probe
Journal of Physics and Chemistry of Materials
Langmuir probe is a powerful diagnostic tool for low pressure gas discharge plasmas, the ability of measurement of local plasma parameters and the electron energy distribution function (EEDF) makes it unique among other diagnostics. The Langmuir probe is consists of sticking a wire into the plasma and measuring the current to it at various applied voltages. We have constructed Langmuir probe For the Characterisation of RF plasma, with Exact value of Capacitor & Inductor for the First and second Harmonics of 13.56 MHz. A system has been designed, fabricated and installed at SVITS, Indore for producing Plasma Enhanced Chemical Vapour Deposition (PE-CVD) technique. The system contains a vacuum chamber, a turbo-molecular pump, two electrodes, vacuum gauges, mass analyzer, mass flow controllers and a RF power supply for producing the plasma using hydrogen gas. The vacuum of the order of 3×10-6 is achieved and DC& RF glow discharge plasma has been created with Argon Gas. The Diagnostics ports are 35 CF & 63 CF. Variation of electron density with radial distance inside the plasma along the diameter of electrode of RF Glow Discharge Argon Plasma are be discussed in this paper.