Radio-frequency Plasmas

Observations of bi-Maxwellian and single Maxwellian negatron brawniness distri merelyion functions in a capacitively twin radio-frequency plasmas by optical maser Thomson scattering M. A. Mansour ElSabbagh,a) M.D. Bowden, K. Uchino, and K. Muraoka Interdisciplinary alumnus teach of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan ~Received 20 November cc0; pass savvy for publication 19 February 2001! Electron energy distribution functions in conf apply- coerce capacitively mate radio-frequency atomic number 18 nails were measured using the technique of laser Thomson scattering. It was make that the distribution functions changed from a bi-Maxwellian at make out insistings to a single Maxwellian at elevateder pressures. These measurements provide separatist check mark of analyse measurements make in similar disgraces. The electron temperature and denseness of the cold group of electrons were measured with an accuracy of give mien than 1 0%. © 2001 American Institute of Physics. @DOI: 10.1063/1.1363695# Low pressure capacitively conjugated radio-frequency ~rf! discharges are used widely in industrial applications, such as material processing for microelectronics. measurement rod of the electron energy distribution function ~eedf! is obese for discretion the physical processes in these plasmas, such as plasma interpersonal chemistry and calculating reaction rates in discharges. For these reasons, there charter been extensive studies of electron behavior in capacitively coupled rf plas-mas, including experiments mostly based on electric probe techniques 1?8 and modelling and simulation studies.9?12 A gross result in umteen of these studies is the obser-vation of a non-Maxwellian eedf for some discharge condi-tions. Godyak and Piejak 1 measured non-Maxwellian eedf in argon discharges using a Langmuir probe, and noted that the non-Maxwellian eedf could be considered as a summation of Maxwellian distribution s of both groups of electrons. In other wor! ds, they considered the eedf as consisting of rive low temperature and eminent temperature components. The high temperature component of the eedf was attributed to stochas-tic electron high temperature in the rf sheaths of the plasma enhanced by the Ramsauer effect. The show of bi-Maxwellian distributions was attributed to insufficient energy exchange of the high and the low temperature components. same results and conclusions carry been obtained by other groups.4?8 The bi-Maxwellian eedf alike has been obtained during computer simulation and modeling studies of capaci-tively coupled rf discharges in argon and other gases.9?12 Godyak and co-workers flip stated that the limitations of the energy effect and range of Langmuir probes puzzle determination of low-energy electrons and detection of rela-tively high-energy electron tails unwieldy for some discharge conditions. The consistency of probe results obtained by many groups, along with simulation and modeling studies, ha ve led to a set of widely accepted conclusions some the electron heating mechanisms in capacitively coupled rf plasmas. However, because of the potential difference problems of probe meth- ods, it is important that experimental results be confirmed by an independent technique. It is also important that the tem-perature and density of the low-temperature component of bi-Maxwellian eedf be determined accurately. In this letter, we report the results of electron property measurements of capacitively coupled rf plasmas make using the method of laser Thomson scattering. optical maser Thomson scattering is a relatively complicated method experimentally, but has the significant advantages including a method that is non-perturbing and that experimental results can be inter-preted straightforwardly.

Previous studies have demonstrated the usefulness of this technique for canvas electron behav-ior in relatively high density plasmas,13?16 while we latterly reported the development of an experimental remains capable of reservation accurate measurements in very low electron den-sity conditions, found in low pressure capacitively coupled rf plasmas.17 The gravel of this letter is to show the measured eedf in these plasmas and to compare the results with those obtained by other groups. Details of the experimental ashes were shown elsewhere 17 and we describe its most salient features here. The discharge bedchamber was a cylindrically shaped stainless-steel vacuum chamber with a diam of three hundred mm. Argon plasmas were sustained between two parallel plate-electrodes made of stainless steel. The electrodes had a diameter of 100 mm and were disconne cted by 20 mm. The speed electrode was connected to a 13.56 megacycle power supply through and through matching network, while the raze electrode was connected to the chamber hem in and to the ground. The laser source was a Nd:YAG laser operated at the second harmonic wavelength of 532 nm. It had a pulse en-ergy of 400 mJ, a pulse width of 7 ns, a beam deviation of 0.5 mrad, and was operated at a repeat rate of 10 Hz. The laser beam was injected in a even parallel to the electrode move up and passed through the central plane of the plasma. It was focused to the center of the chamber by a lens system with a central length of 670 mm. A beam dump, a viewing dump, baffles, and Brewster windows were used to minimize the stray light level. The staccato light was gathered by a lens with diameter of 130 mm and a focal length of 200 mm, at a! Electronic mail: mansour@asem.kyushu-u.ac.jp APPLIED physical science letter VOLUME 78, NUMBER 21 21 whitethorn 2001 3187 0003-6951/2001/78( 21)/3187/3/$18.00 © 2001 American Institute of Phy! sics Downloaded 18 may 2001 to 129.25.14.96. Redistribution contentedness to AIP license or copyright, see http://ojps.aip.org/aplo/aplcr.jsp If you wish to get a full essay, order it on our website: BestEssayCheap.com

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