X-RAY MOIRE PATTERN IN DISLOCATION-FREE SILICON-ON-INSULATOR WAFERS PREPARED BY OXYGEN ION-IMPLANTATION

A moiré pattern formed by the two superimposed lattices of a host silicon substrate and the top "superficial" silicon layer formed in a separation by implanted oxygen (SIMOX) process has been observed with Lang transmission x-ray topography. The moiré patterns clearly show a characteristic fingerprint related to a nonuniformity in the ion implantation apparatus. It is shown that moiré patterns obtained with x-ray topography are a uniquely powerful tool for the characterization of highly ordered SIMOX wafers which have essentially no extended dislocations. Moiré patterns not only image the dilatational strain or lattice rotation between the two superimposed lattices, but also indicate the level of crystallographic perfection of the entire width and depth of the substrate/ superficial layer system.