Microstructural evolution of diamond/Si(100) interfaces with pretreatments in chemical vapor deposition
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L. Chang Division of Engineering and Applied Science, National Science Council, Taipei, Taiwan 10636, Republic of China
T. S. Lin Materials Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan 31015, Republic of Chinu
F.R. Chen Materials Science Center, National Tsiizg Huu University, Hsinclzu, Taiwan 300, Republic of China (Received 1 1 February 1995; accepted 1 August 1995)
Diamond was deposited on Si( 100) substrates by the microwave plasma-assisted chemical vapor deposition method in three steps: carburization, biasing, and growth. High-resolution transmission electron microscopy in cross-sectional view has been used to observe the evolution of microstructures around the interfacial region between diamond and Si in each processing step. The chemistry near the interface was characterized with elemental mapping using an energy-filtered imaging technique with electron energy loss spectroscopy. An amorphous carbon layer, p -Sic and diamond particles, and graphite plates have been observed in the carburization stage. ,8-Sic can form in epitaxial orientation with Si in the following stage of biasing. Graphite and amorphous carbon were not observed after the bias was applied. Diamond grains were aligned in a strongly textured condition in the growth stage. It has been found that diamond, Sic, and Si all have (1 11) planes in parallel. The relation of the evolution of microstructure with the processing conditions is also discussed.
1. INTRODUCTION
Diamond applications have been extensively studied since chemical vapor deposition (CVD) has been successful in synthesizing diamond films. In the earlier studies, it has been found that diamond nucleation on silicon with a smooth surface is scarce, resulting in the formation of particles rather than a continuous film. Consequently, a variety of pretreatment methods were developed to increase the nucleation density of diamond to form a film.' A mechanical pretreatment is one of the most often used methods. The mechanical action, for example, grinding with diamond powders, produces a rough surface which may provide the sites for nucleation. Such surface characteristics are difficult to control with uniformity in large area. Thus, the mechanical pretreatment is regarded as unsuitable for processes which require high quality control, particularly on electronic applications. A bias-enhanced nucleation method recently developed by Yugo et aL2 and Stoner and Glass3 eliminates the need for mechanical pretreatment. Furthermore, the nucleation density can be raised to 10" cm12, higher than those obtained from mechanical pretreatments. J. Mater. Res., Vol. 10, No. 12, Dec 1995
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In recent works using the bias-enhanced nucleation method to grow diamond films on (100) silicon substrates, the results showed that highly oriented films can be ~ b t a i n e d . ~Wolter - ~ et a1.' and Stoner et aL9 have furthermore added a carburization step before applying the bias one, resulting in a diamond film with a
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