US 12,339,770 B2
Storage of threshold voltage shifts
Radu Ioan Stoica, Zurich (CH); Nikolaos Papandreou, Thalwil (CH); Roman Alexander Pletka, Uster (CH); and Charalampos Pozidis, Thalwil (CH)
Assigned to International Business Machines Corporation, Armonk, NY (US)
Filed by INTERNATIONAL BUSINESS MACHINES CORPORATION, Armonk, NY (US)
Filed on Oct. 10, 2023, as Appl. No. 18/483,578.
Prior Publication US 2025/0117320 A1, Apr. 10, 2025
Int. Cl. G06F 12/02 (2006.01)
CPC G06F 12/0246 (2013.01) 19 Claims
OG exemplary drawing
 
1. A method of operating a digital memory device comprising memory cells, each of the memory cells being adapted for storing information on N voltage levels separated by N−1 threshold voltages, the method comprising:
obtaining a plurality of threshold voltage shift (TVS) patterns, each TVS pattern comprising N−1 TVS reference values representing respective expected shifts of the threshold voltages of a specified set of the memory cells having a specific physical condition;
performing an assignment routine comprising, for the specified set:
storing a reference to a matching TVS pattern for the specified set, the matching TVS pattern being selected from the plurality of TVS patterns; and
storing TVS residual values of the memory cells of the specified set, the residual values being determined as differences between actual TVS values of the memory cells and corresponding TVS reference values of the matching TVS pattern;
in response to receiving an instruction for reading information stored by a specified memory cell of the specified set, performing a readout routine comprising:
reading the matching TVS pattern of the specified set and some or all of the TVS residual values of the specified memory cell;
determining restored TVS values of the specified memory cell by combining the TVS reference values of the matching TVS pattern with corresponding read TVS residual values; and
reading the information from the specified memory cell using some or all of the restored TVS values.