Formation of highly oriented diamond film on carburized (100) Si substrate
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Highly oriented diamond film was grown on a (100) Si substrate by a bias-enhanced microwave-plasma chemical vapor deposition. The Si surface was carburized at a faster rate by bias treatment than by carburization alone, but the initial carburization stage was indispensable. During the bias treatment, the flat surface was changed to a textured structure on the nanometer scale. The formation of this structure was required for the synthesis of a highly oriented diamond film. Diamond microcrystals formed subsequently were irregular and of a few to a few tens nanometers in size. They then grew to oriented film in the following growth process.
I. INTRODUCTION The formation of large-area single-crystalline films is a goal of CVD diamond research because of their great potential in microelectronic device technology.1'2 Although mirror-polished silicon (Si) is one of the most practical substrates for diamond deposition, the population density of diamond particles formed on this substrate is normally as low as 104—105 cm" 2 . Thus, a variety of substrates and pretreatment methods have been tested. Recently, Yugo et al? found that a negative bias treatment was very effective for enhancing the nucleation of diamond. Employing this biasenhanced microwave-plasma chemical vapor deposition (bias-enhanced MPCVD) technique, several groups succeeded in controlling the orientation of diamond particles on mirror-finished SiC or Si substrates. Stoner et al.4'5 first obtained a textured diamond film on a /3-SiC film that was grown epitaxially by a thermal CVD method6'7 on a (100) Si substrate, prior to the bias-enhanced MPCVD. Kohl et al} also synthesized a textured diamond film in the same way. In their experiments, the surface of the SiC film was carefully modified by sophisticated pretreatments. On the other hand, Wolter and co-workers9 developed a three-step deposition process consisting of (i) in situ carburization of a mirror-finished Si surface, (ii) precise controlled nucleation under negative biasing, and (iii) growth without biasing. By this technique, a highly oriented boron-doped diamond film was grown on a (100) Si substrate.10 The hole mobility of the film at room temperature was 165 cm 2 /(V • s), which was approximately five times greater than that of polycrystalline films. This in situ process seems to be
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J. Mater. Res., Vol. 10, No. 1, Jan 1995
http://journals.cambridge.org
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very promising for the production of large-area singlecrystalline diamond films, although the relationship between orientation of diamond and process conditions, particularly in the bias-enhanced nucleation step, is not fully elucidated to date. Jiang et al.11'12 formed a highly oriented diamond film on a mirror-polished (100) Si wafer. The substrate was also treated in situ by applying a negative bias in a microwave plasma. These results reveal that controlled nucleation under negative biasing is a key technique for the highly oriented diamond, but details of b
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