US 11,894,079 B2
Memory controller, memory system with improved threshold voltage distribution characteristics, and operation method
Hyeji Lee, Hwaseong-si (KR); Raeyoung Lee, Suwon-si (KR); Jinkyu Kang, Seoul (KR); Sejun Park, Yongin-si (KR); and Jaeduk Lee, Seongnam-si (KR)
Assigned to Samsung Electronics Co., Ltd.
Filed by SAMSUNG ELECTRONICS CO., LTD., Suwon-si (KR)
Filed on Jul. 23, 2021, as Appl. No. 17/384,219.
Claims priority of application No. 10-2020-0142526 (KR), filed on Oct. 29, 2020.
Prior Publication US 2022/0139474 A1, May 5, 2022
Int. Cl. G11C 16/34 (2006.01); G11C 16/26 (2006.01); G11C 16/10 (2006.01)
CPC G11C 16/3463 (2013.01) [G11C 16/102 (2013.01); G11C 16/26 (2013.01); G11C 16/3404 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A method of operating a memory system including memory cells, the method comprising:
preprogramming and erasing the memory cells to set a first threshold voltage distribution for the memory cells;
detecting fast cells among the memory cells set in the first threshold voltage distribution, wherein normal cells among the memory cells each have a threshold voltage equal to or greater than a first threshold voltage, and the fast cells each have a threshold voltage less than or equal to a second threshold voltage which is less than the first threshold voltage; and
programming the memory cells set in the first threshold voltage distribution to a second threshold voltage distribution greater than the first threshold voltage distribution, said programming comprising,
normal programming the normal cells to the second threshold voltage distribution by applying a sequence of incremental step pulse program (ISPP) voltage pulses to the normal cells, and
over-programming the fast cells to the second threshold voltage distribution by applying the sequence of ISPP voltage pulses to the fast cells,
wherein a voltage of an ISPP voltage pulse applied during over-programming is greater than a voltage of a corresponding ISPP voltage pulse applied during normal programming, and
wherein a level of a verification voltage applied during the over-programming is greater than a level of a corresponding verification voltage applied during the normal programming.