Highly selective etch stop by stress compensation for thin-film BESOI

A limiting issue in the application of the BESOI (bond and etchback silicon-on-insulator) technique to whole wafers is the final film thickness nonuniformity, which typically totals approximately 40 nm using the etchback techniques presented to date. Such variation makes BESOI impractical for thin-film SOI (e.g. ⩽300 nm) and applications to fully depleted MOS. The etchback process is a major contributor to the final film thickness nonuniformity. The authors demonstrate a highly selective etch stop of 2×10²⁰ cm^-3 boron concentration, stress compensated by introducing GE (a high atomic number species). The Si_1-x-y Ge_xB_γ etch stop is selective through the reduction of the passivation potential in KOH to a point where negligible etching occurs. The stress compensation gives the wafer surface an exact Si lattice constant. Epitaxial layers are grown over this etch stop without misfit dislocations