Dynamic read valley search in non-volatile memory

A non-volatile storage, latch technology, applied in static memory, read-only memory, digital memory information, etc., can solve problems such as change, threshold voltage drift, etc.

Active Publication Date: 2016-11-23
SANDISK TECH LLC
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  • Abstract
  • Description
  • Claims
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Problems solved by technology

However, the ideal read level may need to change over time due to threshold voltage drift

Method used

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  • Dynamic read valley search in non-volatile memory
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  • Dynamic read valley search in non-volatile memory

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[0031] Techniques for determining dynamic read levels for non-volatile storage elements are disclosed herein. Due to data retention issues, the threshold voltage (V T ) may be offset. Therefore, the read level (CGRV) should be changed / updated to reflect the V T offset. One technique for finding new read levels is to do a valley search. Valley searching refers to a valley between two adjacent threshold voltage distributions. Valley searching may include taking multiple reads to find a valley between two adjacent threshold voltage distributions. The new read level can be based on the location of the trough. In one possible technique, valley searching includes determining a count for non-volatile storage elements having threshold voltages within a threshold voltage window defined by two read levels. This process can be repeated for several threshold voltage windows such that several counts are determined. The process of determining the count may be referred to herein as "s...

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Abstract

Determining dynamic read levels for memory cells is disclosed. A group of memory cells may be read at a pair of reference levels. Results of reading the group at the pair of reference levels are compared while the group is read at a different reference level. By comparing the results of reading the group at the pair of reference levels while reading the group at a different reference level, time is saved. Note that the reading and comparing can be repeated for other pairs of reference levels. The storage device may determine an adjusted read level based on the comparisons of the results for the different pairs of reference levels. The memory cells may be read at a set of reference levels. A voltage on a word line is not back down to ground between the reads in one aspect, which saves considerable time.

Description

[0001] priority claim [0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 160,751, filed May 13, 2015, entitled "EARLY READTERMINATION / SKIP READ FOR DYNAMIC READ VALLEYSEARCH IN NON-VOLATILE MEMORY," the entire contents of which are incorporated by reference In this article. technical field [0003] The present disclosure relates to the field of semiconductor memory, in particular to dynamic read valley search in non-volatile memory. Background technique [0004] Semiconductor memory is widely used in various electronic devices such as cellular telephones, digital cameras, personal digital assistants, medical electronics, mobile computing devices, and non-mobile computing devices. Semiconductor memory may include nonvolatile memory or volatile memory. Non-volatile memory allows information to be stored and retained even when the non-volatile memory is not connected to a power source (eg, a battery). Examples of nonvolatile memory includ...

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Application Information

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IPC IPC(8): G11C16/26
CPCG11C16/26G11C7/14G11C11/5642G11C16/0483G11C16/28G11C16/3418G11C16/3459G11C11/5628G11C16/349
Inventor 肯尼斯·路易萧江华戈皮纳特·巴拉克里希南卡皮尔·韦曼格里什马·沙赫
Owner SANDISK TECH LLC
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