The unique role of ion beam analysis in modeling the thermal evolution of hydrogen in Si implanted at doses required for ion cutting

Abstract

Hydrogen-ion implantation is capable of precise cutting of materials to remove a thin layer for transfer to alternate substrate. Combined with wafer bonding, this technique is capable of joining dissimilar materials to yield heterostructures such as silicon-on-insulator. This has spawned a renewed interest in the behavior of implanted hydrogen in Si. Rutherford backscattering/channeling analysis is shown to reveal an “inverse annealing” effect, where the displacement field increases (∼10×) monotonically with temperature. While this effect has been noted previously by others, it has not been adequately explained. “Inverse annealing” is shown by ion channeling to be anisotropic along different symmetry axes in the lattice. A model is offered that explains this anomaly as arising from microcracks within platelets (hydrogen-related, planar defects) that introduce an anisotropy in the lattice registry. This model will be applied to the study of boron incorporation in Si, which greatly enhances the efficacy of hydrogen-ion cutting. This is easily explained in terms of the model as a change in the orientation rather than the density of the platelets. Lattice location studies using a B(p,α)Be nuclear reaction analysis performed along random and channeling directions is shown to be key in revealing the role of boron in orienting the platelet defects.