The use of ion channeling and elastic recoil detection in determining the mechanism of cleavage in the ion-cut process

Hydrogen ion implantation in Si has been shown to be an effective means of inducing cleavage in Si and facilitating the transfer of thin slices to other substrates, a process known as ion-cut. In our experiments silicon wafers were implanted with 40 keV protons to a variety of ion doses ranging from 5×1016 to 1×1017 cm−2 and subsequently annealed at 600 °C.
Under all of these conditions ion-cutting in the form of “popping off” discrete blisters was obtained.
The cleavage mechanisms in these samples were studied through the combined use of Rutherford backscattering spectroscopy in channeling mode, elastic recoil detection analysis, and scanning electron microscopy.
Our analyses had shown that the cleavage location in Si is largely controlled by the lattice damage that is generated by the H-implantation process.
At lower H doses, the cut location is well correlated with the damage peak and can be explained by damage-induced in-plane stress and the corresponding out-of-plane strain.
However, at higher implantation doses the ion-cut location shifts to a portion of the crystal which contains lower damage and sufficient concentration of H.
This effect can be explained by the changing fracture mechanics at high H concentrations in heavily damaged Si.