Metal nanocrystal memory with sol-gel derived HfO<inf>2</inf> high-к tunneling oxide

Abstract

A metal-oxide-semiconductor (MOS) capacitor structure containing gold (Au) nanoparticles (NPs) within sol-gel derived HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> high-κ oxide is fabricated. Firstly, the Au NPs with particle size of about 3.3 nm were synthesized by chemical reduction method. Then the 10 nm-thick HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> tunneling oxide, the Au NPs and the 15 nm-thick HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> control oxide were prepared by spin coating method to construct a Si/HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Au NPs/HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> memory structure. The sol-gel derived ultra-thin HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> high-κ oxide layer showed good electrical properties and were critical to desirable memory property of the MOS structure. The high-frequency capacitance-voltage(C-V) measurements demonstrated the well defined counterclockwise hysteresis memory loops which was originated from the Au nanocrystals. By utilizing high-k HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as tunneling oxide, the MOS structure showed memory effect even at a low voltage of ± 2 V. The flat-band voltage shift was about 0.8 V by a swapping voltage between ±5 V. Although the memory window was not so large, the MOS showed better retention characteristics by replacing SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> as tunneling oxide. Therefore, we have successfully fabricated nanocrystal memory device with HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> high-κ tunneling oxide which are attractive for low operation voltage non-volatile memory applications.