Hollow Electrode Enhanced RF Glow Plasma Generation and its Application to the Fast Deposition of Microcrystalline Silic
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A5.16.1
Hollow electrode enhanced RF glow plasma generation and its application to the fast deposition of microcrystalline silicon films Toshihiro Tabuchi, Masayuki Takashiri, Yasumasa Toyoshima, Hiroyuki Mizukami Research Division, Komatsu Ltd. 1200 Manda, Hiratsuka, Kanagawa 254-8567, Japan
ABSTRACT A hollow electrode enhanced RF glow plasma excitation technique has been newly developed. In this technique, the reactor is divided into a capacitively-coupled RF glow discharge space and a processing space by the counter electrode, which includes a hollow structure and is placed between a RF electrode and the substrate. After introducing hydrogen gas into the chamber and applying RF power to the electrode, high intensity plasma emission is observed near and inside the hollow structure attached to the counter electrode. By using hollow RF electrode excitation in addition to the hollow counter electrode technique, it is found that plasma emission is further enhanced. The application of these discharge types for semiconductor processing is studied in the case of plasma enhanced chemical vapor deposition (PECVD) of hydrogenated microcrystalline silicon thin films. High crystallinity, photo-sensitivity and a maximum deposition rate of 4.9nm/s can all be achieved at a plasma excitation frequency of 13.56MHz and a temperature of 300oC. Properties of these plasmas are investigated by observing the plasma emission pattern and optical emission spectrum analysis. It is found that, using additional hollow RF electrode discharge, faster processing of device grade hydrogenated microcrystalline silicon thin films can be achieved under lower RF power compared to hollow counter electrode technique alone.
INTRODUCTION A RF excited hollow cathode discharge is a promising plasma technique not only for fast film deposition but also for etching [1,2]. Previous studies [3-5], have reported that a hollow electrode discharge, which is induced in a hollow structure prepared at a counter electrode (so-called anode), can generate high intensity plasma. It has also been shown that microcrystalline silicon (µc-Si) thin films with good photosensitivity can be deposited at 4.9nm/s using this technique named Hollow Electrode Enhanced Plasma Transportation (HEEPT) [5]. In order to improve processing speed and reduce plasma damage to films and/or substrates, a new HEEPT technique has been developed. In this article, the new HEEPT technique and a corresponding silicon thin film deposition process are presented. A plasma source is based on a hollow counter electrode enhanced RF glow discharge accompanied by a hollow RF electrode discharge. Both high plasma intensity and rapid deposition of well crystallized silicon thin films are easily achieved at lower RF power simply adjusting the diameter of holes for gas distribution arranged at the RF electrode. Using SiH4 and H2 gases, it is found that µc-Si thin films with good photosensitivity can be deposited at 6.0nm/s.
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