Gas flow activated in an electron-beam plasma

Abstract

Probe measurements of electron temperature and density, electron energy distribution functions, and plasma potential in a free gas jet activated in an electron-beam plasma and in a planar reactor are presented. The measurements are performed by single, double, and triple electrostatic probes in jets of helium-argon and helium-argon-monosilane gas mixtures. The latter mixture is used to deposit films of microcrystalline and epitaxial silicon. Microcrystalline silicon films of higher quality are obtained in a dense (n e ≈ 10 17 m −3 ) and cold (T e ≈ 1.0-0.5 eV) plasma with a low potential (U sp ≈ 10 V), whereas the growth of monocrystalline silicon films requires a hotter plasma (T e ≈ 3-5 eV) with a potential U sp ≈ 15 V.Key words: probe diagnostics, electron-beam plasma, chemical vapor deposition of thin silicon films.Introduction. Deposition of thin films often involves chemical vapor methods with activation of gaseous reagents in a discharge plasma or electron-beam plasma [1,2]. In particular, a silane plasma is used for silicon-film deposition [3][4][5]. The study of such a plasma is an urgent problem, and one of the most widely used diagnostic methods is the Langmuir probe [6][7][8]. Probe characteristics can yield information on the electron temperature, electron density, plasma potential, and, in the general case, the electron energy distribution function. If a single or a double probe is used, however, it is impossible to determine instantaneous values of plasma parameters (measuring and processing of the current-voltage characteristic is a rather long procedure). Such information can be obtained by a triple probe [8].It was demonstrated [9] by means of probe diagnostics that the temperature and density of secondary electrons in a nitrogen electron-beam plasma are 0.5-2.5 eV and 10 16 -10 17 m −3 , respectively. The temperature was found to decrease and the density was found to increase with increasing pressure in the electron-beam plasma. The measurements performed in an argon electron-beam plasma [10] showed that the electron temperature is approximately 1 eV, the electron density is 5 · 10 16 to 5 · 10 17 m −3 , and the plasma potential is approximately 4 V. Such a plasma produces a soft and nondestructive effect on the surface and can be used for material processing and depositing high-quality thin films [2]. Deposition of epitaxial layers requires a harder plasma, but a principally important quantity in this case is the plasma potential [11].In a reactive plasma, the probe surface is contaminated by growing films; hence, correct measurements in such a plasma are ensured by using heated probes [7]. It was found in [12] with the use of heated probes that the electron temperature and density decrease with increasing flow rate of monosilane or pressure in the discharge chamber.The present paper describes investigations performed in free jets of helium-argon and helium-argonmonosilane mixtures activated in an electron-beam plasma and in a gas flow inside a planar reactor. The goal of the present work was ...

Effect of diluent gas on silicon film deposition from a free jet of monosilane-diluent mixture activated by electron-beam plasma

“…We should note that under the same conditions, the temperature of plasma electrons weakly depends on the current and energy of the electron beam, the argon flow rate, and varies from 1.2 to 1.6 eV. The plasma potential was negative and varied from 2 to 10 V. Similar results were also obtained in [9]. Comparison of the dependences of the silicon film growth rate (Figs.…”

Investigation of the Formation and Energy Density of High-Current Pulsed Electron Beams

“…The captured images are stored in a computer via the controller. In this study, a high-speed framing CCD camera C7977-01 provided by Hamamatsu Co. Japan was used, which has a resolution of 1,000,000 pixels and a fast frame rate up to 3.333×10 6 frame per second (fps). As shown in Fig.…”

“…Recently, Sigeneger and Winkler [5] theoretically investigated the helium plasma in a hollow cathode discharge by a new hybrid approach, and they found significant difference in shapes of the density profiles for the excited atoms considered in their study. In addition, Konstantinov and Khmel [6] used a probe technique to measure the electron temperature and density. Up to now, limited research has been done to determine instantaneous values of the HCPEB.…”