Electrical Characterization of Metal–Oxide–Semiconductor Memory Devices with High-Density Self-Assembled Tungsten Nanodots

Tungsten nanodots (W-NDs) with an ultrahigh density of 1 × 10 13 /cm 2 and a small size of around of 1.5–2 nm were successfully formed by self-assembled nanodot deposition (SAND). A metal–oxide–semiconductor (MOS) memory device was also fabricated with a W-ND layer placed between tunneling SiO 2 and block SiO 2 . Using this device, the effects of annealing on the capacitance characteristics were investigated in detail. After 900 °C post deposition annealing (PDA), an extremely large memory window of about 9.2 V was obtained, indicating that the device is a strong contender for future nonvolatile memory (NVM) applications. The program/erase speed and retention characteristics were also evaluated. The oxidation of tungsten by oxygen from the cosputtered silicon oxide was confirmed by X-ray photoelectron spectroscopy (XPS) measurement. It is considered to degrade the retention characteristics of MOS memory devices.