Highly oriented, textured diamond films on silicon via bias-enhanced nucleation and textured growth
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P. Southworth and P. J. Ellis Kobe Steel Europe Ltd., Research Laboratory, 10 Nugent Road, Surrey Research Park, Guildford, Surrey, GU2 5AF, United Kingdom (Received 16 November 1992; accepted 8 February 1993)
Highly oriented diamond films were grown on single-crystal silicon substrates. Textured films were first nucleated by a two-step process that involved the conversion of the silicon surface to an epitaxial SiC layer, followed by bias-enhanced nucleation. The nucleation stage, which produced a partially oriented diamond film, was immediately followed by a (100) textured growth process, thus resulting in a film surface where approximately 100% of the grains are epitaxially oriented relative to the silicon substrate. The diamond films were characterized by both SEM and Raman spectroscopy. Structural defects in the film are discussed in the context of their potential effect on the electrical characteristics of the resulting film.
I. INTRODUCTION Previous work has shown that diamond may be nucleated on pristine (unscratched) silicon wafers via an in situ pretreatment that involves negatively biasing the substrate while immersed in a methane/hydrogen plasma. 13 This process, termed bias-enhanced nucleation (BEN), has been also used to heteroepitaxially nucleate diamond on single-crystal y8—SiC.46 It was found that greater than 50% of the diamond grains that nucleated were in epitaxial alignment with the SiC substrate. This result was promising, yet the expense of high-quality single-crystal SiC made the further development of this epitaxial process difficult. In subsequent work by Wolter et al.,1 epitaxial nucleation of diamond on (100) silicon wafers was demonstrated via a two-step nucleation process that involved an in situ carburization followed by BEN. It was speculated in this work that the diamond nucleated on an epitaxial yS—SiC conversion layer that formed during the carburization step. By utilizing Si substrates instead of the more expensive SiC single crystals, the development of this epitaxial process then became feasible. In the work presented by Wolter et al.,1 it was shown that approximately 30% of the grains were oriented relative to the (100) silicon substrate. To become useful as a substrate on which to fabricate diamond electronic devices, close to 100% of the grains need to be epitaxially oriented. It is therefore necessary either to achieve 100% epitaxial nucleation, or to start with a partially oriented film and grow under conditions that promote (100) texturing. The latter approach was demonstrated 1334 http://journals.cambridge.org
J. Mater. Res., Vol. 8, No. 6, Jun 1993 Downloaded: 04 Nov 2014
by both Clausing et al.8 and Wild et al.9'10 as a means to obtain highly textured diamond films from randomly oriented seed crystals. These approaches utilize the van der Drift theory of crystal growth evolution in which the resulting texture is a function of the growth competition between different crystal orientations.11 In the present article the authors report on the successful nucleation and gr
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