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US 6,275,411 B1Granted
Spin dependent tunneling memory
AssigneeNonvolatile Electronics, Incorporated
InventorsJames M. Daughton, Brenda A. Everitt, Arthur V. Pohm
Life of this patent
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Abstract
A digital data memory having a bit structure in a memory cell based on a dielectric intermediate separating material with two major surfaces having thereon an anisotropic ferromagnetic thin-film of differing thicknesses. These bit structures are fabricated within structural extent limits to operate satisfactorily, and are fabricated as series connected members of storage line structures. A corresponding conductive word line structure adjacent corresponding ones of these memory cells is used for selecting or operating them, or both, in data storage and retrieval operations.
Claims66
A ferromagnetic thin-film based digital memory, said memory comprising:
- a plurality of bit structures electrically interconnected with information retrieval circuitry, said bit structures comprising:
- an electrically insulative intermediate layer of a selected thickness, said intermediate layer having two major surfaces on opposite sides thereof;
- and
- a memory film of an anisotropic ferromagnetic material on each of said intermediate layer major surfaces of thicknesses differing from one another outwardly from those surfaces by at least 5% to thereby primarily provide switching thresholds for magnetizations of said film adjacent each of said intermediate layer major surfaces that differ in value for a switching of these magnetizations from both being directed initially at least in part in substantially a common direction to being directed at least in part in substantially opposite directions versus a switching from being directed initially at least in part in substantially opposite directions to both being directed at least in part in substantially a common direction, said intermediate layer major surfaces adjacent said memory film having a surface area which with said intermediate layer thickness, together provide a time constant for electrical energizations of said bit structures that is less than 35 μs:
- and
- a plurality of word line structures each having a pair of word line end terminal regions adapted to conduct electrical current in at least one direction therethrough, each of said pairs of word line end terminal regions having an electrical conductor electrically connected therebetween which is located across an electrical insulating layer from said memory film on one of said major surfaces of said intermediate layer of a corresponding one of said bit structures.
3 more elements
A ferromagnetic thin-film based digital memory, said memory comprising:
- a plurality of bit structures electrically interconnected with information retrieval circuitry, said bit structures comprising:
- an electrically insulative intermediate layer of a selected thickness said intermediate layer having two major surfaces on opposite sides thereof;
- and
- a memory film of an anisotropic ferromagnetic material on each of said intermediate layer major surfaces of thicknesses differing from one another outwardly from those surfaces sufficiently greatly, for a selected current being conducted through said bit structure, to prevent magnetizations of said memory film adjacent those surfaces, oriented initially at least in part in a direction substantially opposite that of a word line field generated in a word line field direction by a subsequently supplied current due to a relatively rapid current change initiated through said word line, from both pointing in said word line field direction as a result of such current change initiation even though said word line field magnitude, after expiration of transients therein following such generation thereof, is less than that switching threshold characterizing said thicker memory film if switched by a word line field resulting from a relatively slowly changing word line current, said intermediate layer, major surfaces adjacent said memory film having a surface area which with said intermediate layer thickness, together provide a time constant for electrical energizations of said bit structures that is less than 35 μs;
- and
- a plurality of word line structures each having a pair of word line end terminal regions adapted to conduct electrical current in at least one direction therethrough, each of said pairs of word line end terminal regions having an electrical conductor electrically connected therebetween which is located across an electrical insulating layer from said memory film on one of said major surfaces of said intermediate layer of a corresponding one of said bit structures.
3 more elements
A ferromagnetic thin-film based digital memory, said memory comprising:
- a plurality of bit structures electrically interconnected with information retrieval circuitry, said bit structures comprising:
- an electrically insulative intermediate layer of a selected thickness, said intermediate layer having two major surfaces on opposite sides thereof;
- and
- a memory film of an anisotropic ferromagnetic material on each of said intermediate layer major surfaces of thicknesses differing from one another outwardly from those surfaces by at least 5%, said memory film in a said bit structure being characterized by an anisotropy field, and said width being sufficiently small that demagnetization fields arising in said memory film in response to its saturation magnetization being oriented along that said width exceed in magnitude said anisotropy field, said intermediate layer major surfaces adjacent said memory film having a surface area which with said intermediate layer thickness, together provide a time constant for electrical energizations of said bit structures that is less than 35 μs;
- and
- a plurality of word line structures each having a pair of word line end terminal regions adapted to conduct electrical current in at least one direction therethrough, each of said pairs of word line end terminal regions having an electrical conductor electrically connected therebetween which is located across an electrical insulating layer from said memory film on one of said major surfaces of said intermediate layer of a corresponding one of said bit structures.
3 more elements
A ferromagnetic thin-film based digital memory, said memory comprising:
- a first storage line structure having a first storage line pair of end terminal regions suited to conduct electrical current in at least one direction therethrough, said storage line end terminal regions having electrically connected in parallel therebetween a plurality of bit structures, each said bit structure comprising:
- an electrically insulative intermediate layer, said intermediate layer having two major surfaces on opposite sides thereof;
- and
- a memory film of an anisotropic ferromagnetic material on each of said intermediate layer major surfaces having switching thresholds for magnetizations of said film adjacent each of said intermediate layer major surfaces that differ in value for a switching of these magnetizations from both being directed initially at least in part in substantially a common direction to being directed at least in part in substantially opposite directions versus a switching from being directed initially at least in part in substantially opposite directions to both being directed at least in part in substantially a common direction, and
- a plurality of word line structures each having a pair of word line end terminal regions adapted to conduct electrical current in at least one direction therethrough, each of said pairs of word line end terminal regions having an electrical conductor electrically connected therebetween which is located across an electrical insulating layer from said memory film on one of said major surfaces of said intermediate layer of a corresponding one of said bit structures.
2 more elements
A ferromagnetic thin-film based digital memory, said memory comprising:
- a plurality of bit structures interconnected with information retrieval circuitry so as to have a transistor electrically coupled thereto that selectively substantially prevents current in at least one direction along a current path through at least some set of said plurality of bit structures in which such current would otherwise occur during an information retrieval from a said bit structure if said plurality of bit structures were interconnected with said information retrieval circuitry to permit information retrievals therefrom without said transistor being coupled thereto, each said bit structure comprising:
- an electrically insulative intermediate layer of a selected thickness said intermediate layer having two major surfaces on opposite sides thereof;
- and
- a memory film of an anisotropic ferromagnetic material on each of said intermediate layer major surfaces having switching thresholds for magnetizations of said film adjacent each of said intermediate layer major surfaces that differ in value for a switching of these magnetizations from both being directed initially at least in part in substantially a common direction to being directed at least in part in substantially opposite directions versus a switching from being directed initially at least in part in substantially opposite directions to both being directed at least in part in substantially a common direction, said intermediate layer major surfaces adjacent said memory film having a surface area which, with said intermediate layer thickness, together provide a time constant for electrical energizations of said bit structures that is less than 35 μs, and a plurality of word line structures each having a pair of word line end terminal regions adapted to conduct electrical current in at least one direction therethrough, each of said pairs of word line end terminal regions having an electrical conductor electrically connected therebetween which is located across an electrical insulating layer from said memory film on one of said major surfaces of said intermediate layer of a corresponding one of said bit structures.
1 more element
A ferromagnetic thin-film based digital memory, said memory comprising:
- a plurality of bit structures each connected between corresponding interconnection conductors that are interconnected with information storage and retrieval circuitry so as to have an electrical isolation device electrically coupled thereto that substantially prevents current in at least one direction along a current path through at least some set of said plurality of bit structures in which such current would otherwise occur during an information retrieval from a said bit structure if said plurality of bit structures were interconnected with said information storage and retrieval circuitry to permit information retrievals therefrom without said electrical isolation device being coupled thereto, each said bit structure comprising:
- an electrically insulative intermediate layer of a selected thickness, said intermediate layer having two major surfaces on opposite sides thereof;
- and a memory film of an anisotropic ferromagnetic material on each of said intermediate layer major surfaces having switching thresholds for magnetizations of said film adjacent each of said intermediate layer major surfaces that differ in value for a switching of these magnetizations from both being directed initially at least in part in substantially a common direction to being directed at least in part in substantially opposite directions versus a switching from being directed initially at least in part in substantially opposite directions to both being directed at least in part in substantially a common direction, said intermediate layer major surfaces adjacent said memory film having a surface area which with said intermediate layer thickness, together provide a time constant for electrical energizations of said bit structures that is less than 35 μs;
- and
- a plurality of word line structures each having a pair of word line end terminal regions adapted to conduct electrical current in at least one direction therethrough, each of said pairs of word line end terminal regions having an electrical conductor electrically connected therebetween which is located across an electrical insulating layer from said memory film on one of said major surfaces of said intermediate layer of a corresponding one of said bit structures.
2 more elements
A ferromagnetic thin-film based digital memory, said memory comprising:
- a plurality of bit structures electrically interconnected with information retrieval circuitry, said bit structures comprising:
- an electrically insulative intermediate layer of a selected thickness, said intermediate layer having two major surfaces on opposite sides thereof;
- and
- a memory film of an anisotropic ferromagnetic material on each of said intermediate layer major surfaces having magnetizations which can be switched from both being directed initially at least in part in substantially a common direction to being directed at least in part in substantially opposite directions and can be switched from being directed initially at least in part in substantially opposite directions to both being directed at least in part in substantially a common direction to provide output signals to said information retrieval circuitry, said intermediate layer major surfaces adjacent said memory film having a surface area sufficiently large to provide at least that signal-to-noise ratio needed by said information retrieval circuitry to permit determinations thereby of directions of magnetizations of said memory film on each of said intermediate layer surfaces;
- and
- a plurality of word line structures each having a pair of word line end terminal regions adapted to conduct electrical current in at least one direction therethrough, each of said pairs of word line end terminal regions having an electrical conductor electrically connected therebetween which is located across an electrical insulating layer from said memory film on one of said major surfaces of said intermediate layer of a corresponding one of said bit structures.
3 more elements
A magnetoresistive thin-film layered structure, said structure comprising:
- a substrate having a major surface portion;
- and
- a magnetic field responsive structure supported on said substrate having an electrically insulative intermediate layer with two major surfaces on opposite sides thereof and memory films of ferromagnetic material on each of said intermediate layer major surfaces with at least one of said memory films being a composite thin-film having therein a magnetoresistive first ferromagnetic thin-film and a magnetoresistive second ferromagnetic thin-film with a magnetic moment differing from said first ferromagnetic thin-film.
Dependencies are inferred from the claim text.