The selective area deposition of diamond films
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The selective area deposition of diamond films P. G. Roberts,a) D. K. Milne, and P. John Department of Chemistry, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, United Kingdom
M. G. Jubber and J. I. B. Wilson Department of Physics, Heriot-Watt University, Riccarton, Edinburgh EH14 4AS, United Kingdom (Received 3 March 1995; accepted 20 August 1996)
Diamond films were selectively nucleated and grown on single crystal (100) silicon by microwave plasma assisted chemical vapor deposition with submicron spatial resolution. A thermal silicon dioxide layer on the wafers was patterned by standard photolithography. Nucleation was performed by applying a dc bias of 2250 to 2350 V in a hydrogen-methane plasma. Lifting off the oxide layer by HF etching prior to growth delineated the nucleation pattern which was replicated by the diamond film after growth. The growth of polycrystalline diamond was performed in a hydrogen-carbon monoxide-methane mixture selected to facilitate (100) texturing. Individual faceted crystallites were grown on a square matrix of sites, with a pitch of 3 mm, by controlling the nucleation densities within the windows exposing the prenucleated silicon. However, the orientation of the crystallites was randomly aligned with respect to the (100) silicon lattice within the micron scale windows employed in this study.
I. INTRODUCTION
Because of the combination of a number of favorable properties such as a large band gap, high carrier mobility and breakdown voltage, low dielectric constant, and resistance to high temperatures and radiation, diamond has attracted attention as an attractive material for microelectronic devices. Device quality diamond is a prerequisite to the fabrication of advanced devices. Diamond films can be routinely synthesized by a variety of chemical vapor deposition (CVD) methods, although microwave plasma deposition is the currently preferred route to high purity films. The potential microelectronic applications have been limited by the polycrystalline nature of the resulting films which leads to inferior electrical properties compared to single crystal diamond.1 This problem has been greatly reduced by the recent demonstration of heteroepitaxial growth of polycrystalline diamond2–5 on (100) silicon and concomitant improvement in electrical properties.6 A fundamental step in this process is the application of a dc bias7 to the substrate in order to induce diamond nucleation rather than the more commonly used method of scratching the wafer with diamond dust. Employing the bias conditions used in the heteroepitaxial process, the resulting diamond nuclei are aligned with respect to the underlying (100) substrate. Early attempts8 at fabricating arrays of aligned crystals using octahedral seed crystals inserted into pyramidal etch pits in silicon have realized layers with properties close to single crystal diamond. a)
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J. Mater. Res., Vol. 11, No. 12, Dec 1996
The processe
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