Selection of data for redundancy calculation by likely error rate
AssigneeSanDisk Technologies LLC
InventorsDeepak Raghu, Gautam A. Dusija, Chris Avila, Yingda Dong, Man Mui, Xiying Costa, Pao-Ling Koh
Life of this patent
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Abstract
Layers in a multi-layer memory array are categorized according to likely error rates as predicted from their memory hole diameters. Data to be stored along a word line in a high risk layer is subject to a redundancy operation (e.g. XOR) with data to be stored along a word line in a low risk layer so that the risk of both being bad is low.
Claims17
A method of operating a three-dimensional NAND memory comprising:
- categorizing word lines in a block of the three-dimensional NAND memory into a plurality of categories according to predicted error rates for the word lines;
- selecting data assigned to a first word line from a first category for an exclusive OR (XOR) operation, the first category having a high predicted error rate;
- selecting data assigned to a second word line from a second category for the XOR operation, the second category having a low predicted error rate;
- and
- performing the XOR operation on the data assigned to the first and second word lines to generate XOR data.
A method of operating a three-dimensional memory array that includes multiple NAND strings, each NAND string having a plurality of memory cells in a plurality of levels connected in series, comprising:
- categorizing the plurality of levels of word lines in a block into at least a first category and a second category according to memory hole diameter, the first category containing word lines having the smallest memory hole diameter in the block, the second category containing word lines having the largest memory hole diameter in the block;
- selecting first data assigned to a first word line from the first category for an exclusive OR (XOR) operation;
- selecting second data assigned to a second word line from the second category for the XOR operation;
- and
- performing the XOR operation on the first data and the second data to generate XOR data.
A three-dimensional NAND memory comprising:
- an array of memory cells arranged in a plurality of levels including high risk levels close to a substrate and low risk levels farther from the substrate;
- a plurality of memory hole structures extending vertically through the plurality of levels to connect memory cells of the plurality of levels in NAND strings;
- and
- an exclusive OR (XOR) circuit configured to perform an XOR operation on a portion of data assigned to a high risk level with a portion of data assigned to a low risk level.
Dependencies are inferred from the claim text.