Paper NM+PS+AS-WeA3
Vertically Aligned Si Nanostructure Arrays formed using SF₆/O₂ Plasma

Wednesday, October 22, 2008, 2:20 pm, Room 309

Arrays of high aspect ratio (>10:1) vertically aligned Si nanostructure were formed in an inductively coupled plasma (ICP) reactor using SF6/O2 plasma without any masks at noncryogenic temperature. Mean diameter of the nanostructure arrays is about 100 nm and the mean height is up to 4.77 um. These nanostructure arrays can be fabricated for large area (>100 cm2). The formation of the nanostructure arrays are studied as a function of time, bias RF-power and O2/SF6 ratio. The processing condition of the SF6/O2 plasma is known to markedly affect the preparation of the nanostructure arrays. O2/SF6 ratio determines the formation of the nanostructure arrays. The nanostructure arrays only could be fabricated when the O2 content is not too low or too high, the range is 0.5< O2/SF6<2.5. Two types of the nanostructure arrays formed because of the different bias RF-power, one is nanohole arrays and another is the nanopillar arrays. The formation of the nanostructure is hole when the bias power is 10 W, but the diameter is only 420 nm after etching 150 s. If the bias power increased to 30 W, the nanopillar arrays appear, the mean height is up to 4.77 um after etching 150s. The etching time is also important for the nanostructure arrays. After etching about 40s, the nanostructure arrays appear abruptly and become longer and longer. But very long time etching has destroyed the nanostructure arrays. The mechanism of the plasma etching for fabricating the nanostructure arrays has been investigated using OES, XPS and SEM analyses. From the analyses, the properties of the plasma and the formed passivation layer are mainly reasons for the fabrication of the nanostructure arrays. The best condition to fabricate a high aspect ratio vertically aligned Si nanostructure arrays is suggested.