US 2003/0067013 A1Published application

Phase change nonvolatile storage device and drive circuit

AssigneeKabushiki Kaisha Toshiba

InventorsKatsutaro Ichihara, Hiroaki Yoda

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Abstract

In a phase-change nonvolatile storage device using a phase-change material as storage cells, which is improved to overcome a basic problem involved in conventional devices of this type and reliably, easily operable as a storage device, the pre-record state of a storage cell is read before recording information in the storage cell, and a write pulse optimum for transition is selected and applied. If the storage cell need not change in phase, the write pulse need not be applied. Alternatively, the pulse is adjusted in waveform of the trailing edge, depending on whether the storage cell should be changed to the amorphous state or the crystal state, to control the crystallization hold time.

Claims18

Dependent claims

A drive circuit which drives a phase-change nonvolatile storage device which has a storage cell including a phase-change material variable in phase between a crystal state and an amorphous state, and changes at least a part of said phase-change material of said storage cell in phase between said crystal state and said amorphous state to record information as a first record state corresponding to said crystal state or a second record state corresponding to said amorphous state,

said drive circuit comprising:
a signal generator which generates a first record signal which changes said storage cell from said first record state to said second record state, and a second record signal which changes said storage cell from said second record state to said first record state;
and
a reading circuit which reads the record state of said storage cell before recording information in said storage cell,
said drive circuit applying said first record signal to said storage cell when said storage cell is in said first record state and should be changed to said second record state, and
said drive circuit applying said second record signal to said storage cell when said storage cell is in said second record state and should be changed to said first record state.

3 more elements

A phase-change nonvolatile storage device comprising:

a storage cell including a phase-change material variable in phase between a crystal state and an amorphous state, and changes at least a part of said phase-change material of said storage cell in phase between said crystal state and said amorphous state to record information as a first record state corresponding to said crystal state or a second record state corresponding to said amorphous state;
and
a drive circuit which drives said storage cell,
said drive circuit having:
a signal generator which generates a first record signal which changes said storage cell from said first record state to said second record state, and a second record signal which changes said storage cell from said second record state to said first record state;
and
a reading circuit which reads the record state of said storage cell before recording information in said storage cell,
said drive circuit applying said first record signal to said storage cell when said storage cell is in said first record state and should be changed to said second record state, and
said drive circuit applying said second record signal to said storage cell when said storage cell is in said second record state and should be changed to said first record state.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 10/233,629Filed 4 Sep 2002
Priority: JP 2001-29610227 Sep 2001
Published: 10 Apr 2003
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G11C 13/0069
Auxiliary circuits: writing or programming circuits or methods
G11C 11/56
Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor: using storage elements…
G11C 11/5678
Using storage elements with more than two stable states represented by steps, e.g. of voltage, current, phase, frequency: using…
G11C 13/0004
Using resistive RAM [RRAM] elements: comprising amorphous/crystalline phase transition cells

Family

US 6,750,469 B2Related patent
US 2003/0067013 A1This patent

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