Direct wafer bonding: A new fabrication method for ferroelectric-silicon heterostructures

Ferroelectric-semiconductor heterostructures were fabricated using direct w afer bonding. Polycrystalline Bi4Ti3O12 ferroelectric thin films were depos ited on 3" silicon wafers by chemical solution deposition. The films were p olished and then directly bonded to silicon wafers in a micro-cleanroom. Af ter thermal annealing in air at 500 degrees C for 12 hours, the bonding ene rgy increases up to 1.5 J/m(2). High resolution transmission electron micro scopy shows a significant difference between the bonded and reacted interfa ces. A Metal-Ferroelectric-Silicon (MFS) structure containing the ferroelec tric-Si bonded interface was achieved by polishing down and etching the han dling wafer. Capacitance-voltage (C-V) and current-voltage (I-V) characteri stics were measured for the Bi4Ti3O12 /Si heterostructures with a bonded in terface.