US 7,923,712 B2Granted

Phase change memory element with a peripheral connection to a thin film electrode

AssigneeInternational Business Machines Corporation

InventorsJohn Christopher Arnold, Lawrence Alfred Clevenger, Timothy Joseph Dalton, Michael Christopher Gaidis, Louis L. Hsu, Carl John Radens, Keith Kwong Hon Wong, Chih-Chao Yang

Life of this patent

Estimating the term…

patentgrep

Loading patent…

Abstract

A PCM cell structure comprises a first electrode, a phase change element, and a second electrode, wherein the phase change element is inserted in between the first electrode and the second electrode and only the peripheral edge of the first electrode contacts the phase change element thereby reducing the contact area between the phase change element and the first electrode and thereby increasing the current density through the phase change element and effectively inducing the phase change at lower levels of current and reduced programming power.

Claims20

Dependent claims

A phase change memory cell comprising:

a first dielectric layer having an upper region with a central upper surface which is flat and a recessed region of said first dielectric layer surrounding said upper region, with said recessed region having a recessed surface lower than said central upper surface;
said first dielectric layer including a via conductor extending therethrough having an upper surface coplanar with said central upper surface;
a trilayer stack including said upper region of said first dielectric layer, a lower electrode which is a planar, flat, thin film formed on said central upper surface, and an insulating cap of dielectric material formed on said lower electrode;
said upper region, said lower electrode and said insulating cap having aligned vertical sidewalls extending from a top surface of said insulating cap down to said recessed surface of said recessed region surrounding said trilayer stack;
said recessed region extending aside from said trilayer stack and said upper region, aside from said via conductor and aside from said central upper surface;
said lower electrode is in contact with a top surface of said via conductor, said lower electrode layer having a periphery;
a phase change element formed on said upper surface of said insulating cap on said aligned vertical sidewalls and on said lower recessed surface with said periphery of said lower electrode contacting said phase change element at an angle to an inner surface thereof surrounding said vertical sidewalls of said trilayer stack;
and
an upper electrode formed over and in electrical contact with said phase change element;
wherein said phase change element is electrically connected to at least a portion of said periphery of said lower electrode.

7 more elements

A phase change memory cell, comprising:

a first dielectric layer having an upper region with a central upper surface which is flat and a recessed region of said first dielectric layer surrounding said upper region, with said recessed region having a recessed surface lower than said central upper surface;
a trilayer stack including said upper region of said first dielectric layer, a first electrode comprising a planar, flat, thin film formed on said central upper surface, and an insulating cap of dielectric material on said first electrode with said trilayer stack being surrounded by vertical sidewalls;
a phase change element;
said first electrode having a periphery;
a second electrode;
said phase change element being located between said first electrode and said second electrode having an inner surface and a separate surface;
said phase change element surrounding said vertical sidewalls of said trilayer stack;
and
said first electrode having said periphery of said first electrode in electrical and mechanical contact with said inner surface of said phase change element at a normal angle to said inner surface and said separate surface of said phase change element in electrical and mechanical contact with said second electrode.

6 more elements

A phase change memory cell, comprising:

a trilayer stack including an upper region of a first dielectric layer having a central upper surface which is flat and extends horizontally, a first electrode which is a planar, flat, thin film that is electrically conductive and having a top surface, with said first electrode formed on top of said central upper surface, and an insulating cap comprising a dielectric layer formed on said top surface of said first electrode;
a via conductor extending through said first dielectric layer with said via conductor having an exposed top end coplanar with said central upper surface;
said first dielectric layer having a recessed surface lower than said central upper surface aside from said central upper surface;
said insulating cap, said thin film lower electrode, and said upper region of said first dielectric layer having aligned vertical sidewalls extending between said central upper surface and said recessed surface surrounding said trilayer stack;
said first electrode having a lower surface in contact with said exposed top end of said via conductor;
said insulating cap formed on said top surface of said first electrode above said central upper surface;
a second electrode which is electrically conductive;
a phase change element formed over said insulating cap between said first electrode and said second electrode with at least a portion of said periphery of said first electrode in electrical and mechanical contact with said first electrode at an angle normal to an inner plane of said phase change element and said phase change element surrounding said vertical sidewalls of said trilayer stack;
said second electrode being in electrical and mechanical contact with an outer plane of said phase change element;
said first electrode being separated from said second electrode;
and
said phase change element formed over said upper surface of said insulating cap, over said aligned vertical sidewalls of said first dielectric layer, over said vertical sidewalls of said insulating cap and over said periphery of said first electrode;
whereby said phase change element is electrically connected to said peripheral sidewalls of said first electrode.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 12/492,618Filed 26 Jun 2009 · division
Priority: 30 Mar 2006
Published: US 2010/0001253 A17 Jan 2010
Granted: 12 Apr 2011
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H10N 70/063
Shaping switching materials: by etching of pre-deposited switching material layers, e.g. lithography
H10N 70/231
Multistable switching devices, e.g. memristors: based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect
H10N 70/821
Constructional details of multistable switching devices: device geometry
H10N 70/826
Device geometry: adapted for essentially vertical current flow, e.g. sandwich or pillar type devices