Susumu Meguro and Osamu Ohashi
National Research Institute for Metals, Tsukuba 305-0047 (National Institute for Materials Science)
Diffusion joining processes of FZ silicon single crystals were carried out in order to study influence of oxide at joining surface. Relationship between joining conditions and mechanical properties, fracture morphologies, surface composition, cross section microstructure, and electric resistance were investigated.
Joining surface of FZ silicon blocks were treated by hydrofluoric acid, RCA process, and thermal oxidation. Diffusion joining processes were held in air and vacuum atmosphere. Mechanical properties of joints were investigated by 4-point bending.
Joining at air atmosphere and oxide film at joining interface cause larger bending strength. Fracture morphologies observation of joints give suggestion that oxide film decreases interface fracture area. Auger electron spectroscopy of treated surfaces were carried out in order to study behavior of oxide. On RCA processed specimen, oxygen concentration decreases by heating over 1073 K. This result shows probability that thin oxide film disappears from joining interface. Scanning electron microscopy observation of fracture surfaces show that joints with thermal oxide film break at interface between silicon and oxide film. Transmission electron microscopy observation of cross sections shows that thermal oxide film is amorphous and interface between silicon and oxide is flat. Electric resistance of joints with thermal oxide film decreases at higher joining temperature.
(Received September 18, 2001)
diffusion joining, silicon, oxide, bending strength, interface
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