Effects of Body Doping in a NAND Flash String without Source/Drain

초록

Cell structure using fringing field from control gate (CG) is very promising for a scaled NAND flash memory beyond sub-40nm node. We investigated a new NAND string structure not with n-type source/drain (S/D) regions but with p-type regions in the space between gates. Even though the NAND string has a p-type region instead of n-type S/D in the space between adjacent two cells, induced layer (virtual source/drain) can be easily formed in the space by the fringing field from the CGs. When comparing a conventional NAND string with n-type S/D, the proposed structure shows better drain induced barrier leakage (DIBL) and subthreshold swing (SS) characteristics, and also shows better immunity against the process variation than conventional structure with n-type S/D. The electrical characteristics of the proposed structure were investigated as parameters of the width and doping concentration at the p/n-type region. As a NAND cell string, the current drivability of the proposed structure was also studied. (C) 2011 The Japan Society of Applied Physics