US5341328A
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US
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Electrically erasable memory elements having reduced switching current requirements and increased write/erase cycle life
Assignee: Ovonyx Inc
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Filing: 1992-06-15
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Granted: 1994-08-23
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Expires: 2012-06-15
Abstract
Abstract Disclosed herein is a solid state, directly overwritable, non-volatile, high density, low cost, low energy, high speed, readily manufacturable, single cell memory element having reduced switching current requirements and increased write/erase cycle life. The structurally modified memory element includes an electrical contact formed of amorphous silicon, either alone or in combination with a layer of amorphous carbon layer. The memory element exhibits orders of magnitude higher switching speeds at remarkably reduced switching energy levels. The novel memory elements of the instant invention are further characterized, inter alia, by at least two stable and non-volatile detectable configurations of local atomic and/or electronic order, which configurations can be selectively and repeatably accessed by electrical input signals of designated energies. The reduced switching current requirements and an increased write/erase cycle life are achieved by structurally modifying the electrical contact with the aforementioned layer of amorphous silicon.
Inventors
- 👤 Stanford R. Ovshinsky
- 👤 Stephen J. Hudgens
- 👤 Wolodymyr Czubatyj
- 👤 David A. Strand
- 👤 Guy C. Wicker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 00:17
CPC Classifications
G; G11; G11C; G11C11/00; G11C11/56; G11C11/5678; G11C13/00; G11C13/0002; G11C13/0004; H; H10; H10B; H10B63/00; H10B63/20; H10B63/80; H10B69/00; H10N; H10N70/00; H10N70/011; H10N70/021; H10N70/026; H10N70/20; H10N70/231; H10N70/801; H10N70/821; H10N70/826; H10N70/841; H10N70/881; H10N70/882; H10N70/8828; G11C13/04; G11C2213/00; G11C2213/70; G11C2213/72
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
174 words
A directly overwritable, single-cell memory element comprising: a volume of memory material defining a single cell memory element, said memory material characterized by (1) at least two electrically detectable values of resistance (2) the ability to be set at one of said detectable values in response to a selected electrical input signal so as to provide said single cell with data storage capabilities; means for applying an input signal to set said memory material to a selected resistance value; said input means consisting of two spacedly disposed contacts, each contact including a thin-film layer of silicon material disposed in direct contact with said volume of memory material, said two contacts providing the terminals for reading information stored in and writing information into said memory material; and said single cell of memory material being setable, by said selected input signal to a desired resistance value regardless of the previous value to which said memory material was set, and said memory material capable of remaining set at said value after the set signal has been terminated.
Claim 2
Dependent Claim
174 words
A directly overwritable, single-cell memory element comprising: a volume of memory material defining a single cell memory element, said memory material characterized by (1) at least two electrically detectable values of resistance (2) the ability to be set at one of said detectable values in response to a selected electrical input signal so as to provide said single cell with data storage capabilities; means for applying an input signal to set said memory material to a selected resistance value; said input means consisting of two spacedly disposed contacts, each contact including a thin-film layer of silicon material disposed in direct contact with said volume of memory material, said two contacts providing the terminals for reading information stored in and writing information into said memory material; and said single cell of memory material being setable, by said selected input signal to a desired resistance value regardless of the previous value to which said memory material was set, and said memory material capable of remaining set at said value after the set signal has been terminated.
Claim 3
Dependent Claim
39 words
The memory element of claim 1 wherein each of said two spacedly disposed contacts further includes a thin-film layer of carbon material disposed on the side of said thin-film layer of silicon material remote said volume of memory material.
Claim 4
Dependent Claim
30 words
The memory element of claim 2 wherein each of said two spacedly disposed contacts additionally includes a thin-film layer of molybdenum material disposed on said thin-film layer of carbon material.
Claim 5
Dependent Claim
30 words
The memory element of claim 1 wherein each of said two spacedly disposed contacts additionally includes a thin-film layer of molybdenum material disposed on said thin-film layer of silicon material.
Claim 6
Dependent Claim
34 words
The memory element of claim 1 wherein said thin-film layer of silicon material is originally in an amorphous state and thereafter, during an initial forming/switching, a portion of said thin-film amorphous silicon material crystallizes.
Claim 7
Dependent Claim
40 words
The memory element of claim 2 wherein said thin-film layers of silicon and carbon material are originally in an amorphous state and thereafter, during an initial forming/switching, a portion of said thin-film layers of amorphous silicon and carbon material crystallizes.
Claim 8
Dependent Claim
16 words
The memory element of claim 2 wherein said volume of memory material includes a chalcogen element.
Claim 9
Dependent Claim
24 words
The memory element of claim 7 wherein said chalcogen element is selected from the group consisting of Te, Se and mixtures or alloys thereof.
Claim 10
Dependent Claim
17 words
The memory element of claim 7 wherein said volume of memory material additionally includes a transition metal.
Claim 11
Dependent Claim
28 words
The memory element of claim 9 wherein said at least one transition metal is selected from the group consisting of Cr, Fe, Ni and mixtures or alloys thereof.
Claim 12
Dependent Claim
15 words
The memory element of claim 10 wherein said at least one transition metal is Ni.
Claim 13
Dependent Claim
27 words
The memory element of claim 7 wherein one or more elements are compositionally graded throughout the volume of memory material so as to reduce set resistance drift.
Claim 14
Dependent Claim
37 words
The memory element of claim 7 wherein said memory material additionally includes one or more elements selected from the group consisting of Ge, Sb, Bi, Pb, Sn, As, S, Si, P, O and mixtures or alloys thereof.
Claim 15
Dependent Claim
58 words
The memory element of claim 9 wherein said memory material includes Te, Ge, Sb and a transition metal, in the ratio (Te a Ge b Sb 100- (a+b)) c TM 100-c where the subscripts are in atomic percentages which total 100% of the constituent elements wherein TM is one or more transition metals; and a>70, 5>b>50, and 90>c>99.5.
Claim 16
Dependent Claim
10 words
The memory element of claim 7 wherein 48>a>58 and 8>b>40.
Claim 17
Dependent Claim
27 words
The memory element of claim 14 wherein said one or more transition metals is selected from the group of Cr, Fe, Ni and mixtures of alloys thereof.
Claim 18
Dependent Claim
15 words
The memory element of claim 14 wherein said one or more transition metals is Ni.
Claim 19
Dependent Claim
27 words
The memory element of claim 14 wherein one or more elements are compositionally graded throughout the volume of memory material so as to reduce set resistance drift.
Claim 20
Dependent Claim
18 words
The memory element of claim 1 wherein said volume of memory material is operatively disposed in a pore.
Claim 21
Dependent Claim
18 words
The memory element of claim 19 wherein the diameter of said pore is less than about 1 micron.
Claim 22
Dependent Claim
34 words
The memory element of claim 1 wherein said selected electrical input signal which sets said memory material to a desired resistance value is at least one pulse of a selected voltage, current and duration.
Claim 23
Dependent Claim
55 words
The memory element of claim 21 wherein said memory material can be set to a low resistance value by a selected pulse duration of between about 100 and about 500 nanoseconds using a pulse voltage of between about 1 and about 2 volts and a pulse current of between about 0.5 and about 1 milliamperes.
Claim 24
Dependent Claim
55 words
The memory element of claim 21 wherein said memory material can be set to a high resistance value by a selected pulse duration of between about 30 and about 50 nanoseconds using a pulse voltage of between about 2 and about 3 volts and a pulse current of between about 0.75 and about 5 milliamperes.
Claim 25
Dependent Claim
40 words
The memory element of claim 21 wherein said selected input signal includes a plurality of energy pulses, and a feedback system is provided for initiating additional pulses to insure that said memory element is set at the desired resistance value.
Claim 26
Dependent Claim
26 words
The memory element of claim 24 wherein the total duration of said plurality of energy pulses in said feedback system is less than about 500 nanoseconds.
Claim 27
Dependent Claim
28 words
The memory element of claim 1 wherein said volume of memory material and said contacts are formed so as to define a matrix array of thin film material.
Claim 28
Dependent Claim
28 words
The memory element of claim 26 wherein each memory element in said array is addressably isolated from other memory element in the array by thin film isolation devices.
Claim 29
Dependent Claim
30 words
The memory element of claim 27 wherein the combination of thin film memory elements and isolation devices define a three dimensional, multilevel array of discreetly addressable high density memory cells.
Claim 30
Dependent Claim
23 words
The memory element of claim 1 wherein the thickness of the volume of memory material is from about 100 Å to 5000 Å.
Claim 31
Dependent Claim
19 words
The memory element of claim 29 wherein said thickness of said volume of memory material is about 1500 Å.
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1997-08-22 | 1998-02-21 | 1998-08-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-08-22 | 2002-02-21 | 2002-08-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-08-22 | 2006-02-21 | 2006-08-23 | $7700.00 | Window Closed / Lapsed |