Published online by Cambridge University Press: 01 February 2011
We introduced high-k Al2O3/Si3N4 buffer layer in MFIS (Metal-Ferroelectric-Insulator-Semiconductor) devices to reduce the leakage current though the buffer (I) layer. We prepared the buffer layer by nitridizing Si substrate by atomic nitrogen radicals and then deposited Al2O3 film using ALD (Atomic Layer Deposition) technique. The interface state density between the ALD-Al2O3/Radical-Si3N4 stacked insulator and a Si substrate is as low as 1011 cm−2eV−1. The current density less than 10−9 A/cm2 is realized under the 1V bias application using films with the capacitance density of 12fF/mm2. The c-axis oriented Bi3.45La0.75Ti3O12 (BLT) ferroelectric films were deposited to make MFIS structure. With this structure, we obtained the retention time as long as 1.5×106 sec (about 17 days). This excellent retention character is attributable to the high insulating property of the ALD-Al2O3/Radical-Si3N4 stacked insulator and also attributable to the perfect elimination of defects at the interfaces in the MFIS structure.