Advanced MFIS structure with Al2O3/Si3N4 stacked buffer layer

We developed high-performance metal-ferro-electric-insulator-semiconductor (MFIS) structures with a thin Al2O3 layer deposited on Si3N4 buffer layer. The Al2O3 were deposited by atomic layer deposition technique and the Si3N 4 were made by the direct nitridation of Si substrate using atomic nitrogen radicals. Since the buffer Si3N4 was made perfectly damage-free and hydrogen-free, we can perform high temperature oxidation to eliminate defects in Al2O3 and ferroelectric films down to the negligible level. On the stacked buffer layer, we deposited highly c-axis oriented Bi-3.25 La-0.75 Ti3O12 film and fabricated MFIS structure. With the help of the high insulating property of a buffer layer and a highly c-axis oriented ferroelectric film, we succeeded to realize the large memory windows together with the long retention characters in the Pt/Bi-3.25 La-0.75 Ti3O12 /Al2O3 /Si3N4 /Si MFIS structure.