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Measuring threshold voltage distribution in memory using an aggregate characteristic

A threshold voltage distribution, memory circuit technology, applied in static memory, read-only memory, information storage, etc., can solve the problems of lack of flexibility and efficiency

Inactive Publication Date: 2009-01-14
SANDISK IL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, conventional methods for calculating threshold voltage distributions, e.g., using external analog devices or the like, are not suitable for "on-line" implementation in, e.g., real-time flash memory hypervisors or manufacturing test (where the timing element is critical). lack of flexibility and efficiency

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  • Measuring threshold voltage distribution in memory using an aggregate characteristic
  • Measuring threshold voltage distribution in memory using an aggregate characteristic
  • Measuring threshold voltage distribution in memory using an aggregate characteristic

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Embodiment Construction

[0050] The present invention provides a method and apparatus for reducing read errors in a non-volatile storage system.

[0051] One example of a memory system suitable for implementing the present invention uses a NAND flash memory structure, which involves arranging multiple transistors in series between two select gates. The series connection of transistors and the select gates is called a NAND string. figure 1 is a top view showing a "and not" string. figure 2 is the equivalent circuit of the "AND" string. figure 1 and figure 2 The NAND string depicted in includes four transistors, 100 , 102 , 104 and 106 , in series and sandwiched between a first select gate 120 and a second select gate 122 . Select gate 120 enables the connection of the NAND string to bit line 126 . Select gate 122 enables the connection of the NAND string to source line 128 . Select gate 120 is controlled by applying an appropriate voltage to control gate 120CG. Select gate 122 is controlled b...

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PUM

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Abstract

A threshold voltage distribution of a set of storage elements in a memory device is measured by sweeping a control gate voltage while measuring a characteristic of the set of storage elements as a whole. The characteristic indicates how many of the storage elements meet a given condition, such as being in a conductive state. For example, the characteristic may be a combined current, voltage or capacitance of the set which is measured at a common source of the set. The control gate voltage can be generated internally within a memory die. Similarly, the threshold voltage distribution can be determined internally within the memory die. Optionally, storage elements which become conductive can be locked out, such as by changing a bit line voltage, so they no longer contribute to the characteristic. New read reference voltages are determined based on the threshold voltage distribution to reduce errors in future read operations.

Description

[0001] inventor : [0002] Mark Shlick and Menahem Lasser [0003] Cross References to Related Applications [0004] This application claims the benefit of US Provisional Patent Application No. 60 / 917,679, filed May 14, 2007, which is hereby incorporated by reference. [0005] This application is related to co-pending and commonly assigned U.S. Patent Application No. ______, entitled "Operating Sequence And Commands For Measuring Threshold Voltage Distribution In Memory" (Docket No. SAND-1282US0 / MSD-0023), which is filed with this application and is incorporated herein by reference. technical field [0006] The present invention relates to a memory device. Background technique [0007] The use of semiconductor memory in various electronic devices has become more and more popular. For example, non-volatile semiconductor memory is used in cellular telephones, digital cameras, personal digital assistants, mobile computing devices, non-mobile computing devices, and other de...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G11C16/34
Inventor 马克·施利克梅纳赫姆·拉瑟
Owner SANDISK IL LTD