US Patent 9105689 Bonded semiconductor structure with SiGeC layer as etch stop

A semiconductor structure is formed with a first wafer (e.g. a handle wafer) and a second wafer (e.g. a bulk silicon wafer) bonded together. The second wafer includes an active layer, which in some embodiments is formed before the two wafers are bonded together. A substrate is removed from the second wafer on an opposite side of the active layer from the first wafer using a SiGeC layer as an etch stop. In some embodiments, the SiGeC layer is then removed; but in some other embodiments, it remains as a strain-inducing layer.