Two-Dimensional Structure of Reactive Silane Plasmas in the Presence of Crossed Magnetic and Electric Fields
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TWO-DIMENSIONAL STRUCTURE OF REACTIVE SILANE PLASMAS IN THE PRESENCE OF CROSSED MAGNETIC AND ELECTRIC FIELDS
HIROSHI FUJIYAMA, H.KAWASAKI, Y.MATSUDA AND N.OHNO Faculty of Engineering, Nagasaki University 1-14, Nagasaki 852, Japan
ABSTRACT In order to control reactive silane(SiH 4 ) glow discharge plasmas for an a-Si:I{ thin film synthesis, we have investigated the dependence of plasma parameters on the crossed magnetic field B perpendicular to the discharge electric field E. As the result of modification of plasma structure by a crossed magnetic field, subsequent modified profiles of optical emission from SiH radicals were observed. On the other hand, H,, emission in the cathode sheath region, which may be caused by high energy secondary electrons(-y-electron), were not so much influenced by a magnetic field. By modulating the crossed magnetic field in AC discharge plasmas, the time-averaged uniform (2.5% inhomogeneity) profile of SiH radical could be realized near the substrate sustained outside the discharge region.
Introduction In recent years, there has been a growing interest in the plasma-enhanced CVD reactor with a magnetic field[1]s[3]. In order to prepare large-area uniform thin films, we have developed the scanning plasma method(SPM) using a modulated magnetic field[3] [4]. In such the magnetized plasma processing, the magnetic field increases the collisions between electrons and reactive gas molecules as a result of electron Larmor gyration. When the crossed magnetic field is applied perpenticular to the electric field, transport effect due to the E x B drift are added to the collision increment effect. When the magnetic field is modulated by a low frequency signal, plasmas begin to scan outside the discharge region and large-area uniform plasma layer can be obtained near the substrate, which is sustained outside the discharge region. Using this method, we could prepare large-area(lm x 2m) homogeneous a-Si:H thin films[3]. In this paper, we report the detailed two-dimensional structures of SiH'(413.5nm), ArI (750.4nm) and H.a(656.3nm) emission intensity profiles in a SiH 4(10%)/Ar magnetized plasma. In addition, on the basis of these structures, the spatial averaging effect of emissive species, plasma density and film thickness by the SPM is discussed.
Experimental
Apparatus
Cross-sectional view of the experimenal setup is shown in Fig. 1. The experiments were performed in a long cylindrical vacuum chamber of 32cm in diameter and 230 cm in length. The axial magnetic field was uniform over 230 cm. The plasmas were produced by a multi-electrodes parallel-plate AC (60Hz) glow discharge. As the AC power supply was isolated from the grounded potential, the electrode system was symmetrized electrically. The modulated magnetic field was applied perpendicular to the discharge electric field and paralell to the electrode surface. The SiH 4 (10%)/Ar gas was used and the typical gas pressure was 0.05 Torr. The apparatus of emission spectroscopy is shown in Fig. 2. The discharge space was observed through a pl
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