Crystal Wafer: November 2018

Nov 26, 2018

X-ray Radiographs Taken with Silicon Single Crystal Wafers by Divergent X-ray Method

By our own Divergent X-ray Method, X-ray radiographs consisted of broad Laue-spots with X-ray spectral lines were simply and easily taken with the wafers of silicon single crystals of various kinds. On each of the Laue-spots, many X-ray spectral lines of various shapes and ground figures consisted of somewhat broadened lines, straightened or curved, were revealed. It is considered that these X-ray spectral lines and the ground figures of the Laue-spots are mostly produced by the dislocations and other imperfections in the crystal wafer, and that from the appearances of these X-ray spectral lines and ground figures the bodily distribution of the dislocations and other imperfections can be presumed.

Source:IOPscience

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Nov 12, 2018

Deformation of Single Crystal Wafers of Silicon Caused by Lapping

Two types of deformation of single crystal wafers of silicon introduced by lapping one face of a wafer are observed. There exists a critical thickness, Tc, above which the deformation is symmetric with respect to the center of wafers (spherical deformation), and below which the deformation is symmetric with respect to a certain diameter (cylindrical deformation). The plots of the deflection for the spherical deformation at any cross section and for the cylindrical deformation at cross section perpendicular to axis of symmetry coincide with parabolic lines. In the case of {100} wafers, there are two stable modes for the cylindrical deformation and the axes of symmetry coincide with <100> on {100}. Whereas {111} wafers have a single stable mode: some axes of symmetry coincide with <211> and/or <110> but the rest does not coincide with any direction having low indices. It is likely that both types of deformation originate from the plastically deformed layer on the lapped face and that large portion of a wafer is deformed elastically except for the layer.