Hairpin-resonator probe design and measurement considerations (original) (raw)
Related papers
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
Estimation of Plasma Parameters using Radio-Frequency Resonance Technique
Journal of the Physical Society of Japan, 2001
Numerous workers have studied rf resonance probe under the condition ν m ω ep , i.e. under collisionless condition, where ν m is angular collision frequency and ω ep is angular plasma frequency. In the present paper, the interaction of rf signal with a back diffusion type plasma has been studied without neglecting collision frequency. The problem has been discussed theoretically under this condition, and the derivation yields two expressions for which impedance is minimum. To verify the result experimentally, a rectangular plasma chamber is designed and fabricated, where electron density can be changed without changing the discharging potential and vacuum conditions. From the experiment two resonance peaks are obtained in the If 2 curve (I: current and f : applied frequency) corresponding to the two minimum impedance conditions, from which plasma parameters like electron density, collision frequency and electron temperature have been estimated.
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.
Rf probe technology for the next generation of technological plasmas
Journal of Physics D: Applied Physics, 2001
We describe radio frequency (rf) analysis of technological plasmas at the 13.56 MHz fundamental drive frequency and integer narrow-band harmonics up to n = 9. In particular, we demonstrate the use of harmonic amplitude information as a process end-point diagnostic. Using very high frequency (vhf) techniques, we construct non-invasive ex situ remote-coupled probes: a diplexer, an equal-ratio-arm bridge, and a dual directional coupler used as a single directional device. These probes bolt into the plasma-tool 50 transmission-line between the rf generator and matching network, and hence do not require modification of the plasma tool. The 50 probe environment produces repeatable measurements of the chamber capacitance and narrow-band harmonic amplitude with an end-point detection sensitivity corresponding to a 2 dB change in the harmonic amplitude with the removal of 1 cm 2 of photoresist. The methodology and design of an instrument for the measurement of the plasma-tool frequency response, and the plasma harmonic amplitude and phase response are examined. The instrument allows the monitoring of the plasma phase delay, plasma-tool short-and long-term ageing, and process end-point prediction.
Electron neutral collision frequency measurement with the hairpin resonator probe
2017
Electron neutral collision frequency is measured using both grounded and floating hairpin resonator probes in a 27 MHz parallel plate capacitively coupled plasma (CCP). Operating conditions are 0.1-2 Torr (13.3-267 Pa) in Ar, He, and Ar-He gas mixtures. The method treats the hairpin probe as a two wire transmission line immersed in a dielectric medium. A minimization method is applied during the pressure and sheath correction process by sweeping over assumed collision frequencies in order to obtain the measured collision frequency. Results are compared to hybrid plasma equipment module (HPEM) simulations and show good agreement.
A Comparative Study of Single and Double Langmuir Probe Techniques for RF Plasma Characterization
Contributions to Plasma Physics, 1999
In this study, the plasma density and electron temperature of Radio Frequency (RF) plasmas were determined by three types of Langrnuir probes, namely a conventional double probe, a single probe with RF, choke and a single probe with RF choke and compensating electrode. The same plasmas were characterized by the three probes, each performing three measurements per plasma condition, in order to determine the precision of the measurement results. After performing a comparative analysis, which looked at the precision and the accuracy of these results, .the conclusion is that the double probe, which has already the advantage of the simplest construction, yields the most reliable results for both capacitively and inductively coupled RF plasmas. The single probe with RF choke and compensating electrode has a similar precision as the single probe without compensating electrode, but its accuracy is better.
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.
Numerical enhancement of the microwave cavity method for plasma density measurement
2017
Microwave resonator method is well established and sensitive technique of plasma density measurements, especially in low pressure plasmas. The traditional Slater solution of the electromagnetic field perturbation (suitable for small perturbations only) is replaced with more accurate, yet comprehensible numerical model, also addressing further phenomena such as the resonator eigenmodes and the stability of the dominant mode.
Observations of resonant modes formation in microwave generated magnetized plasmas
The European Physical Journal D, 2011
Ion sources have a significant number of applications in accelerator facilities and in industrial applications. In particular, the electron cyclotron resonance ion sources (ECRIS) are nowadays the most effective devices that can feed particle accelerators in a continuous and reliable way, providing high current beams of low and medium charge state ions and lower, but still remarkable, beam current for highly charged ions. In recent years several experiments have shown that the current, the charge states and even the beam shape change by slightly varying the microwave frequency (the so-called frequency tuning effect -FTE). The theoretical explanation of these results is based on the difference in the electromagnetic field pattern over the resonance surface, i.e. that region where the electrons resonantly interact with the incoming wave. In order to be consistent with the experiments, this model requires that standing waves are formed also in presence of a dense plasma. The proof was sought by means of a series of measurements performed with a network analyzer and with a plasma reactor operating at 2.45 GHz, according to the principles of the microwave discharge ion sources (MDIS). The measurements have been carried out with the aim to achieve the electromagnetic characterization of the plasma chamber in terms of possible excited resonant modes with and without plasma, and they reported that resonant modes are excited inside the cavity even in presence of a dense plasma. It was observed that the plasma dynamics strongly depends on the structure of the standing waves that are generated. The measurement of the eigen-frequencies' shifts were carried out for several values of pressure and RF power, thus linking the shift with the plasma density measured by a Langmuir probe. The changes in plasma shape, density and electron temperature have been also monitored for different operating conditions. A strong variation of plasma properties has been observed as a consequence of the introduction of the Langmuir probe inside the resonant cavity, thus demonstrating that the standing wave can be strongly perturbed even by means of relatively small metallic electrodes. The measurements reported hereinafter are relevant also for ECRIS, because they confirm the validity of the theoretical model that describes the frequency tuning.