Memory characteristics of self-assembled tungsten nanodots dispersed in silicon nitride

In this letter, tungsten nanodots (W-NDs) in silicon nitride formed by a self-assembled nanodot deposition method have been investigated as a floating gate of nonvolatile memory (NVM). Observations from transmission electron microscopy and x-ray diffraction pattern clearly confirm the formation of crystallized W-NDs with a diameter of ∼5 nm. The metal-oxide-semiconductor device with W-NDs in silicon nitride exhibits a larger memory window (∼4.1 V at ±12 V sweep), indicating charge trapping and distrapping between the W-ND and a silicon substrate. The program/erase behaviors and data retention characteristics were evaluated. After 10 years retention, a large memory window of ∼3.4 V with a low charge loss of ∼15% was extrapolated. These results demonstrate advantages of W-NDs in silicon nitride for the NVM application.