Impact of Electron and Hole Trap Profiles in BE-TOX on Retention Characteristics of 3D NAND Flash Memory

Trap profiles in the bandgap-engineered tunneling oxide (BE-TOX) layer of a 3D NAND flash memory were investigated using a transient current trap spectroscopy technique. A new pulse scheme was introduced to generate channel holes and subsequently analyze the hole traps in the BE-TOX layer. In the fresh cell, the hole traps were primarily located at a trap energy level (E_T) of 1.1 eV, whereas the electron traps exhibited two distinct peaks at E_T = 0.75 and 1.25 eV. With increasing program/erase (P/E) cycling operations, the peak E_T associated with hole traps shifted toward shallower levels. Conversely, the electron traps remained unchanged, although their intensities increased. The extracted trap generation exhibited the power-law characteristics.