Identification and operation of sub-prime blocks in nonvolatile memory
First Claim
Patent Images
1. A method of operating blocks of a memory array comprising:
- categorizing the blocks into a plurality of categories including prime blocks, sub-prime blocks, and bad blocks;
wherein the categorizing includes identifying a bad block from test results obtained from the bad block, and subsequently identifying sub-prime blocks based on their proximity to the bad block;
subsequently selecting individual blocks in different planes for parallel operation in metablocks such that each block in a metablock is selected from the same category;
configuring metablocks formed from prime blocks as prime metablocks that are operated in a first manner; and
configuring metablocks formed from sub-prime blocks as sub-prime metablocks that are operated in a second manner that is different from the first manner.
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Abstract
In a block-erasable nonvolatile memory array, blocks are categorized as bad blocks, prime blocks, and sub-prime blocks. Sub-prime blocks are identified from their proximity to bad blocks or from testing. Sub-prime blocks are configured for limited operation (e.g. only storing non-critical data, or data copied elsewhere, or using some additional or enhanced redundancy scheme).
37 Citations
18 Claims
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1. A method of operating blocks of a memory array comprising:
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categorizing the blocks into a plurality of categories including prime blocks, sub-prime blocks, and bad blocks; wherein the categorizing includes identifying a bad block from test results obtained from the bad block, and subsequently identifying sub-prime blocks based on their proximity to the bad block; subsequently selecting individual blocks in different planes for parallel operation in metablocks such that each block in a metablock is selected from the same category; configuring metablocks formed from prime blocks as prime metablocks that are operated in a first manner; and configuring metablocks formed from sub-prime blocks as sub-prime metablocks that are operated in a second manner that is different from the first manner. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of operating erase blocks of a memory array comprising:
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individually testing a plurality of erase blocks to determine a number of memory cells with threshold voltages that are between target threshold voltage ranges associated with logic states for each of the plurality of erase blocks; categorizing the plurality of erase blocks into a plurality of categories based on the number, the plurality of categories including prime erase blocks, and sub-prime erase blocks including categorizing erase blocks that are in close proximity to bad blocks as sub-prime blocks; operating prime erase blocks in a first manner; operating sub-prime erase blocks in a second manner that is different from the first manner; and wherein operation in the second manner is restricted to storing only data that is recoverable from other blocks in the memory array. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method of operating erase blocks of a memory array comprising:
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individually testing a plurality of erase blocks to obtain block-specific test information; storing the block-specific test information; subsequently, categorizing the plurality of erase blocks into a plurality of categories based on the block-specific test information, the plurality of categories including prime erase blocks, and sub-prime erase blocks; identifying bad blocks and categorizing erase blocks that are in close proximity to bad blocks as sub-prime blocks; configuring prime erase blocks for general use in storing user data; and configuring sub-prime erase blocks for limited use. - View Dependent Claims (15, 16, 17, 18)
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Specification