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 ( 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 100C - 300C for short times. For annealing temperatures up to 150C, 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 200C 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.