Finding read disturbs on non-volatile memories
First Claim
1. A method of operating a non-volatile memory system having one or more memory circuits and a controller circuit, the memory circuits each including one or more arrays of non-volatile memory cells formed along word lines and the controller circuit managing the storage of data on the memory circuit, the method comprising:
- for each of a first plurality of distinct divisions of the one or more memory arrays maintaining by the controller circuit a count of the number of times word lines of the corresponding division are accessed for a read operation;
in response to one of the counts for a corresponding division reaching a first threshold value, subdividing the corresponding division into a second plurality of distinct first subdivisions; and
subsequently maintaining by the controller circuit for each of the first subdivisions a count of the number of times word lines of the subdivision are accessed for read operations.
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Accused Products
Abstract
In non-volatile memory devices, the accessing of data on word line can degrade the data quality on a neighboring word line, in what is called a read disturb. Techniques are presented for determining word lines likely to suffer read disturbs by use of a hash tree for tracking the number of reads. Read counters are maintained for memory units at a relatively coarse granularity, such as a die or block. When the counter for one of these units reaches a certain level, it is subdivided into sub-units, each with their own read counter, in a process that be repeated to determine frequently read word lines with a fine level of granularity while only using a relatively modest amount of RAM on the controller to store the counters.
175 Citations
29 Claims
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1. A method of operating a non-volatile memory system having one or more memory circuits and a controller circuit, the memory circuits each including one or more arrays of non-volatile memory cells formed along word lines and the controller circuit managing the storage of data on the memory circuit, the method comprising:
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for each of a first plurality of distinct divisions of the one or more memory arrays maintaining by the controller circuit a count of the number of times word lines of the corresponding division are accessed for a read operation; in response to one of the counts for a corresponding division reaching a first threshold value, subdividing the corresponding division into a second plurality of distinct first subdivisions; and subsequently maintaining by the controller circuit for each of the first subdivisions a count of the number of times word lines of the subdivision are accessed for read operations. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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Specification