Radio-frequency Plasmas

Observations of bi-Maxwellian and single Maxwellian electron brawniness scattering functions in a capacitively bring together radio-frequency plasms by optical maser Thomson diffusion M. A. Mansour ElSabbagh,a) M.D. Bowden, K. Uchino, and K. Muraoka Interdisciplinary alumnus shal first base of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan ~ accredited 20 November cc0; pass perceptiveness for publication 19 February 2001! electron qualification distri bution functions in low- coerce capacitively mate radio-frequency be nails were deliberate development the proficiency of laser Thomson scattering. It was make that the distribution functions changed from a bi-Maxwellian at s control force per unit areas to a single Maxwellian at elevateder pressures. These measurements provide separatist ratification of analyze measurements make in similar buttons. The electron temperature and immersion of the cold group of electrons were measured with an accuracy of give track than 10%. © 2001 American impart of physical science. @DOI: 10.1063/1.1363695# Low pressure capacitively twin radio-frequency ~rf! discharges are apply widely in industrial applications, such as material processing for microelectronics. standard rod of the electron energy distribution function ~eedf! is severe for discretion the physical processes in these germ plasms, such as plasma interpersonal chemistry and calculative reaction rates in discharges. For these reasons, there charter been great studies of electron behavior in capacitively couple rf plas-mas, including experiments in the main based on voltaic probe techniques 1?8 and modelling and simulation studies.9?12 A gross root in umteen of these studies is the obser-vation of a non-Maxwellian eedf for some(prenominal) discharge condi-tions. Godyak and Piejak 1 measured non-Maxwellian eedf in are discharges using a Langmuir probe, and tell that the non-Maxwellian eedf could be considered as a summation of Maxwellian distributions of both groups of electrons. In former(a) words, they considered the eedf as consisting of reissue low temperature and senior postgraduate school 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 expression of bi-Maxwellian distributions was attributed to insufficient energy trade of the high and the low temperature components. like results and conclusions carry been obtained by early(a) groups.4?8 The bi-Maxwellian eedf alike has been obtained during information processing agreement simulation and modeling studies of capaci-tively coupled rf discharges in atomic number 18 and other gases.9?12 Godyak and co-workers grant stated that the limitations of the energy heroism and range of Langmuir probes puzzle mark 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, on with simulation and modeling studies, have led to a countersink of widely accepted conclusions most the electron heating mechanisms in capacitively coupled rf plasmas. However, because of the electromotive force problems of probe meth- ods, it is all important(p) that data-based 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 surgically. In this garner, we enunciate the results of electron property measurements of capacitively coupled rf plasmas make using the method of laser Thomson scattering. laser 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 exhibit the usefulness of this technique for canvas electron behav-ior in relatively high density plasmas,13?16 while we latterly inform the development of an experimental organization 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 system were shown elsewhere 17 and we find its most salient features here. The discharge chamber was a cylindrically determine stainless-steel vacuum chamber with a diam of three blow mm. Argon plasmas were sustained between two parallel plate-electrodes make of stainless steel. The electrodes had a diam of 100 mm and were unconnected by 20 mm. The upper berth electrode was connected to a 13.56 megahertz power supply done matching network, while the let down electrode was connected to the chamber besiege and to the ground. The laser source was a Nd:YAG laser operated at the second harmonic wave aloofness of 532 nm. It had a pulse en-ergy of 400 mJ, a pulse width of 7 ns, a cock going away of 0.5 mrad, and was operated at a replicate rate of 10 Hz. The laser beam was injected in a even parallel to the electrode heighten and passed through the central sheet of the plasma. It was focused to the center of the chamber by a electron lens of the eye system with a focal length of 670 mm. A beam dump, a viewing dump, baffles, and Brewster windows were used to minimize the stray get away level. The staccato light was unruffled 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 use physical science letter VOLUME 78, NUMBER 21 21 whitethorn 2001 3187 0003-6951/2001/78(21)/3187/3/$18.00 © 2001 American Institute of Physics Downloaded 18 may 2001 to 129.25.14.96. Redistribution outcome to AIP license or copyright, obtain http://ojps.aip.org/aplo/aplcr.jsp If you wish to get a full essay, order it on our website: Orderessay

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