Ferroelectric-semiconductor heterostructures obtained by direct wafer bonding

A novel fabrication process of ferroelectric-semiconductor heterostructures based on direct wafer bonding has been demonstrated. Polycrystalline Bi4Ti3O12 ferroelectric thin films were deposited on 3 in. silicon wafers using chemical solution deposition. The films were polished and then directly bonded to silicon wafers in a micro-cleanroom. After thermal annealing in air at 500 °C for 12 h, the bonding energy increases up to 1.5 J/m2. High resolution transmission electron microscopy shows the difference between the bonded and reacted interfaces. Obtaining a metal-ferroelectric-silicon (MFS) structure containing the ferroelectric-Si bonded interface was achieved by polishing down and etching the handling wafer. The Bi4Ti3O12 film kept its ferroelectric properties as shown by C–V measurement.