Re-distribution of hydrogen during low temperature annealing of H-implanted Si
C. Miclaus, M.S. Goorsky, Y.M. Kim, and Y.H.Xie
University Of California, Los Angeles
Department of Materials Science and Engineering
Los Angeles, CA 90095-1595
The structural changes that accommodate wafer splitting after hydrogen implantation of silicon wafers and the transfer of split layers to a handle substrate were investigated as a function of low annealing temperatures. Most previous work on the changes that occur to hydrogen implanted layers have focused on higher temperature ranges (³ 450 °C); the distribution of hydrogen during low temperatures (100 – 300 °C) can be important for direct wafer bonding and to any process in which low temperature bonding is required. (004) silicon substrates were implanted with hydrogen with a dose that ranged from 5x1015cm-2 to 8x1016cm-2 and energies of either 30kV or 140kV. The changes in the implanted layer properties were investigated using triple axis x-ray diffraction and atomic force microscopy after annealing at 100°C - 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 minutes or more led to increased surface roughness and a change to the implant profile, although blister formation did not occur. Blister formation was observed for annealing at 300 °C. Higher surface roughness and blistering is not conducive to successful wafer bonding, so these measurements helped to determine the annealing sequence that is appropriate for bonding a hydrophobic implanted wafer with a hydrophobic handle wafer. Hydrophobic bonded wafers were successfully fabricated with the transferred layer showing similar structural properties as a thin epitaxial film of the same thickness.