Electrical Characteristics Improvement of NAND Flash Memory on Experiment to Replace 49BF2+ with 11B+ in Implantation of Ions

Tuesday, 30 May 2017
Grand Ballroom (Hilton New Orleans Riverside)
H. M. Choi (Sungkyunkwan University, Samsung Electronics Co. Ltd) and Y. Roh (Sungkyunkwan University)
As device size of NAND Flash is shrinking, the program and erase operations need the smaller number of electrons. So the importance of decreasing electron loss is getting increase. Because electron loss causes degradation of the device reliability. As has been discussed before, ion-implantation damage is important factor of NAND Flash fabrication process and device characteristics. Ion implantation damage makes interface trap so it causes electron loss in the device. The heavy ion mass (amu) ion-implantation process makes inevitably not only severe surface lattice damage and more defects in silicon (Si) surface but more thermal budget to recrystallizing. After RTA (Rapid Thermal Annealing) process, the unrestored defects exist at the silicon (Si) surface by heavy ion mass (amu) ion-implantation process damage. In this paper, we focus on endurance improvement characteristics between 49BF2+ ion implantation and 11B+ ion-implantation in 1X floating-gate (FG) NAND Flash cell. The interface trap density (Dit) decreases during initial and stress status by replacing 49BF2+ with 11B+. and erase Vth shift improves after 50k program/erase cycles. From experimental results, we found that the improvement by replacing 49BF2+ with 11B+ reduces interface trap at Si/SiO2 and improves endurance by reducing erase Vth shift in the program/erase cycles.