Strain evolution in hydrogen-implanted silicon

The structural changes that accommodate wafer splitting after hydrogen implantation of silicon and the transfer of split layers to a handle substrate were investigated using triple axis x-ray diffraction, to monitor the strain in the implanted layer, and atomic force microscopy. Silicon substrates (004) were implanted with a hydrogen dose that ranged from 5 × 10 15 cm −2 to 8 × 10 16 cm −2 and energies of either 30 kV or 140 kV. The changes in the implanted layer properties were investigated after annealing at 150–300°C for short times. For annealing temperatures up to 150°C, the strain-induced implant profile did not change appreciably nor did the surface roughness increase, indicating that, for these implant conditions, the implant is stable. Annealing at 200°C or higher for 10 min or more led to increased surface roughness and a change to the implant profile, although blister formation did not occur. Higher surface roughness is not conducive to successful wafer bonding, so these measurements helped to determine the annealing sequence that is appropriate for bonding. In this case, hydrophobic bonded wafers were successfully fabricated with the transferred layer showing similar structural properties as a thin epitaxial film of the same thickness. The use of x-ray scattering for this technique can be easily transferred to other materials for which other techniques, such as infrared absorption, have not been developed.