Improvement of characteristics with a sub-5 nm ge-doped silicon nitride layer in charge trap flash memory cells

The silicon nitride layer can be used to produce the charge trapping/detrapping characteristic in a non-volatile charge trap flash (CTF) memory device. However, it has been suggested that sub-5 nm silicon nitride layer has too little trapping/detrapping properties to embody the non-volatile memory characteristics. As the demand for smaller CTF memory cell size increases rapidly, thickness reduction of the silicon nitride layer is an inevitable technical issue. In this paper, we introduce a Ge-doping method as a new solution, and discuss how it overcomes the silicon nitride layer scaling limit by comparing the characteristics of as-grown and Ge-doped silicon nitride CTF memory cells. The sub-5 nm Ge-doped silicon nitride CTF memory cells show larger memory window, faster program speed and better data retention characteristics compared with as-grown silicon nitride CTF memory cells. These results indicate that sub-5 nm silicon nitride CTF memory cells can have sufficient trapping/detrapping properties to exhibit non-volatile memory characteristics when we use Ge-doped silicon nitride as a charge storage layer.