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Cell-state determination in phase-change memory

A phase change memory, state technology, applied in static memory, digital memory information, information storage, etc., can solve the problem of redundancy not conducive to memory capacity, reducing code validity, validity scaling and other issues

Inactive Publication Date: 2013-05-01
IBM CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Although drift coding can be a potentially powerful technique, its effectiveness generally scales with the redundancy of the code used
Higher redundancy is detrimental to the memory capacity available to store actual user data
Usually only minimal redundancy is tolerated, and this can reduce the code's effectiveness in dealing with drift

Method used

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  • Cell-state determination in phase-change memory
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  • Cell-state determination in phase-change memory

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Embodiment Construction

[0037] figure 1 is a simplified schematic diagram of a phase change memory device embodying the present invention. The device 1 includes a phase change memory 2 for storing data in one or more integrated arrays of multi-level PCM cells. Although shown as a single block in the figures, in general memory 2 may comprise any desired configuration of PCM memory cells ranging, for example, from a single chip or die to packages each containing multiple memory chips. Multiple storage groups. Reading and writing of data to the memory 2 is performed by the reading / writing means 3 . The device 3 comprises a data write and read measurement circuit 4 for writing data to the PCM cells and for making cell measurements allowing the cell state to be determined and thus the stored data to be read back. Circuitry 4 can address individual PCM cells for both writing and reading purposes by applying appropriate voltages to the array of word lines and bit lines in memory population 2 . This proc...

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Abstract

Methods and apparatus are provided for determining the state of a phase-change memory cell. A plurality of measurements are made on the cell, the measurements being dependent on the sub-threshold current-versus-voltage characteristic of the cell. The measurements are processed to obtain a metric which is dependent on the slope of the sub- threshold current-versus-voltage characteristic. The state of the cell is then determined in dependence on this metric which, unlike absolute cell resistance,is substantially unaffected by drift.

Description

technical field [0001] The present invention relates generally to phase change memory, and more particularly to methods and apparatus for determining the state of phase change memory cells. Background technique [0002] Phase change memory (PCM) is a new non-volatile solid-state memory technology that utilizes the reversible switching of certain chalcogenide materials between at least two states with different conductivities. PCM is fast, has very good retention and durability properties and has demonstrated upgrades to future lithography nodes. For these reasons it is considered to have the potential to replace or complement flash memory in today's mainstream memory and storage applications. [0003] In commercially available PCM devices, the basic memory unit ("cell") can be set into one of two states, crystalline and amorphous, by the application of heat. In the amorphous state, which represents a binary zero, the resistance of the cell is high. A chalcogenide material...

Claims

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Application Information

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IPC IPC(8): G11C13/00
CPCG11C13/004G11C11/5678G11C13/0004G11C7/1006H10N70/231
Inventor E·S·埃里弗塞里乌A·潘塔齐N·帕潘德雷乌C·伯津迪斯A·塞巴斯蒂安
Owner IBM CORP