High-performance metal-ferroelectric-insulator-semiconductor structures with a damage-free and hydrogen-free silicon-nitride buffer layer

We developed high-performance metal-ferroelectric-insulator-semiconductor (MFIS) structures with a damage-free and hydrogen-free Si3N4 buffer layer as an insulator. We fabricated Si3N4 films by nitriding Si substrates with N-2 and/or atomic N radicals generated by an rf radical cell. In contrast to conventional Si3N4 films, the radical-nitride Si3N4 films showed no hysteresis or flat-band shift in the capacitance-voltage (C-V) characteristics even after high-temperature treatments, such as crystallization annealing of ferroelectric thin films deposited on the buffer Si3N4. Using this radical nitride Si3N4 as a buffer layer, we fabricated MFIS diodes with a Pt/Bi3.25La0.75Ti3O12/Si3N4/Si structure. These diodes had good hysteresis in their C-V characteristics, resulting from remnant polarization of the ferroelectric films. However, no other parasitic effects originating in charge trapping and/or detrapping were observed. (C) 2001 American Institute of Physics.