Metal nanocrystal memory with sol-gel derived HfO2 high-к tunneling oxide

A metal-oxide-semiconductor (MOS) capacitor structure containing gold (Au) nanoparticles (NPs) within sol-gel derived HfO₂ 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 HfO₂ tunneling oxide, the Au NPs and the 15 nm-thick HfO₂ control oxide were prepared by spin coating method to construct a Si/HfO₂/Au NPs/HfO₂ memory structure. The sol-gel derived ultra-thin HfO₂ 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 HfO₂ 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 SiO₂ with HfO₂ as tunneling oxide. Therefore, we have successfully fabricated nanocrystal memory device with HfO₂ high-κ tunneling oxide which are attractive for low operation voltage non-volatile memory applications.