A single-crystal silicon thin film formed by secondary recrystallization

Thin encapsulated silicon films were zone heated in the solid state just under the melting point with a quartz-iodine lamp over a range of speeds between 0.005 and 0.05 cm/sec. The recrystallized thin films were examined with electron channeling, transmission electron microscopy, scanning and optical microscopy. The recrystallized 1/2-μm- thick film was essentially a single crystal with large equiaxed subgrains oriented with the (100) nearly normal to the plane of the film and the 〈010〉 direction along the growth direction at growth velocities below 0.01 cm/sec. Misorientations between adjacent large 100-μm subgrains were of the order of 1°. The driving force of grain growth in the silicon thin film was determined to be the surface energy anisotropy of the silicon oxide interface from observations of grain boundary grooves that were pinned by a few micron-size included grains. Both the mechanism of recrystallization and the potential for producing silicon-on-insulator material by solid-state recrystallization are discussed.