Si Whisker Growth by Hydrogen Radical using Hot Filament CVD Reactor
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1018-EE05-30
Si Whisker Growth by Hydrogen Radical using Hot Filament CVD Reactor Hiroshi Nagayoshi1, Suzuka Nishimura2, Kazutaka Terashima2, Nobuo Matsumoto2, and Alexander G. Ulyashin3 1
Tokyo National College of Technology, 1220-2,Kunugida-machi, Hachioji, Tokyo, Japan
2
Shonan Institute of Technology, 1-1-25, Tsujido, Fujisawa, Kanagawa, Japan
3
Institute for Energy Technology, P.O.Box 40, Kjeller, NO-2027, Norway
ABSTRACT This paper describes the growth mechanism of silicon whisker on a silicon substrate using hot filament CVD reactor. Only hydrogen is used as source gas. The particle layer could be obtained at high filament current condition under hydrogen ambient. XPS analysis result suggests that the particle is composed of tungsten silicide. The deposition condition of the particle layer is much depended on the substrate size, surface condition and the distance between the substrate and the filament. The experimental results suggest that the silicon hydride, which generated at the silicon surface by hydrogen radical etching, react with the tungsten filament material around the filament, depositing on the silicon substrate. The silicon surface is etched by hydrogen radical and its resultant surface morphology is much depended on the particle deposition pattern. Many silicon whiskers, which diameter is varied from 10 to 50 nm, are observed on the textured silicon surface when the residence time of the source gas in the reactor is long. Each whisker has a silicide particle on their tip. The silicon hydride generated by the hydrogen radical etching is much absorbed to the silicide particle when the source gas residence time is long, enabling the silicon whisker growth from the particle. The results suggest that nm size whisker structure is much stable compare to the bulk silicon against etching reaction.
INTRODUCTION There has been growing interest in developing methods to form 3-dimensional nanostructure on semiconductor for nanoscale device applications[1]. The direct growth of heteroepitaxial nanostructure has attract match attention since large lattice mismatches can be rapidly accompanied in whisker growth and novel quantum structures can be devised on a silicon platform. Silicon whiskers are of increasing interest due to their properties as well as their potential for new devices. Some silicon whisker growth methods such as chemical vapor deposition (CVD), molecular beam epitaxy (MBE), and pulsed laser vaporization (PLV) have been reported[2-6]. In case of the CVD method, small droplets of metals, such as gold, are forming low-temperature eutectic liquids with silicon, acting a seed for the whisker growth. This growth mechanism is well known as vapor-liquid-solid (VLS) growth mechanism[7-8]. The silicon is preferentially incorporated via the liquid silicon-metal droplet, the droplet being supersaturation with silicon. Crystalline silicon, in thermodynamic equilibrium with the liquid
particle, precipitates out from the droplet. We investigated the Si whisker growth by Hot Filament CVD using hydro
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