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US 9,792,174 B2Granted
Bad column handling in flash memory
AssigneeSanDisk Technologies LLC
InventorsDamian Pablo Yurzola, Eran Sharon, Idan Alrod, Michael Altshuler, Madhuri Kotagiri, Rajeev Nagabhirava
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Abstract
In a flash memory, redundant columns are used alternatively as replacement columns for replacing bad columns or to provide additional redundancy for ECC encoding. Locations of bad columns are indicated to a soft-input ECC decoder so that data bits from bad columns are treated as having a lower reliability than data bits from other columns.
Claims8
A multi-plane flash memory array comprising:
- a first plane of flash memory cells comprising first non-redundant columns and first redundant columns, the first non-redundant columns having first bad columns, wherein a number of the first bad columns is less than or equal to a number of the first redundant columns, and wherein each of the first redundant columns stores replacement data for one of the first bad columns;
- and
- a second plane of flash memory cells comprising second non-redundant columns and second redundant columns, the second non-redundant columns having second bad columns, wherein a number of the second bad columns is greater than a number of the second redundant columns, and wherein at least a portion of the second redundant columns stores Error Correction Code (ECC) encoded data and a remaining portion of the second redundant columns stores replacement data for a portion of the second bad columns.
Dependencies are inferred from the claim text.