Trapping of implanted hydrogen for ultrathin layer transfer

We have studied the impact of the incorporation of a buried and ultrathin layer (i.e a few nm), engineered to trap the implanted hydrogen in the donor substrate, on the silicon layer transfer by Smart Cut™. Two kinds of buried layers were studied: boron doped silicon and silicon-germanium alloy. We show that thin layers of boron doped silicon are particularly efficient to trap implanted hydrogen from the surrounding matrix. Using this structure, the transferred silicon layer presents typically a roughness of a few angstroms RMS, which represents an order of magnitude lower than the process without trapping layer. Moreover, this approach allows to transfer ultrathin silicon layer, i.e less than 100 nm thick, and is then promising for advanced generation of Silicon-On-Insulator wafers.