Long Retention Performance of a MFIS Device Achieved by Introducing High-k Al₂O₃/Si₃N₄/Si Buffer Layer

<jats:title>ABSTRACT</jats:title><jats:p>We introduced high-k Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/Si<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub> 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 Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> film using ALD (Atomic Layer Deposition) technique. The interface state density between the ALD-Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/Radical-Si<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub> stacked insulator and a Si substrate is as low as 10<jats:sup>11</jats:sup> cm<jats:sup>−2</jats:sup>eV<jats:sup>−1</jats:sup>. The current density less than 10<jats:sup>−9</jats:sup> A/cm<jats:sup>2</jats:sup> is realized under the 1V bias application using films with the capacitance density of 12fF/mm<jats:sup>2</jats:sup>. The c-axis oriented Bi<jats:sub>3.45</jats:sub>La<jats:sub>0.75</jats:sub>Ti<jats:sub>3</jats:sub>O<jats:sub>12</jats:sub> (BLT) ferroelectric films were deposited to make MFIS structure. With this structure, we obtained the retention time as long as 1.5×10<jats:sup>6</jats:sup> sec (about 17 days). This excellent retention character is attributable to the high insulating property of the ALD-Al<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub>/Radical-Si<jats:sub>3</jats:sub>N<jats:sub>4</jats:sub> stacked insulator and also attributable to the perfect elimination of defects at the interfaces in the MFIS structure.</jats:p>