Memory device

• US 8,344,348 B2
• Filed: 10/02/2008
• Issued: 01/01/2013
• Est. Priority Date: 10/02/2008
• Status: Active Grant

• Current Assignee: Carlow Innovations, LLC
• Original Assignee: Ovonyx Incorporated (Micron Technology, Inc.)
• Inventors: Wicker, Guy, Czubatyj, Wolodymyr
• Primary Examiner(s): Nadav, Ori
• Application Number:
  US12/244,421
• Publication Number:
  US 20100084625A1
• Time in Patent Office: 1,552 Days
• Field of Search: 257 2- 5
• US Class Current: 257/4
• CPC Class Codes: H10B 63/24 of the Ovonic threshold switching type
• CPC Class Codes: H10N 70/20 Multistable switching devices, e.g. memristors
• CPC Class Codes: H10N 70/231 based on solid-state phase change, e.g. between amorphous and crystalline phases, Ovshinsky effect
• CPC Class Codes: H10N 70/826 adapted for essentially vertical current flow, e.g. sandwich or pillar type devices
• CPC Class Codes: H10N 70/8413 adapted for resistive heating
• CPC Class Codes: H10N 70/8825 Selenides, e.g. GeSe
• CPC Class Codes: H10N 70/8828 Tellurides, e.g. GeSbTe

Abstract

An electrical device includes a first electrode and a second electrode. A first active material is between the first electrode and second electrode. A second active material is between the first electrode and second electrode. A nonlinear electrode material is disposed between the first electrode and the second electrode. The nonlinear electrode material is electrically in series with the first electrode, the first active material, the second active material, and the second electrode. The first electrode and the first active material undergo no chemical or electrochemical reaction when current passes between the first electrode and the second electrode.

Claims

1. An electrical device comprising:

a first electrode;

a second electrode;

a first active material layer disposed between said first electrode and said second electrode, wherein said first active material layer includes

a programmable resistance material,

a phase-change material, or

a chalcogenide material;

a second active material layer disposed between said first electrode and said second electrode, wherein a lower surface of the second active material layer is disposed adjacent an upper surface of the first active material layer, wherein said second active material layer differs in composition from said first active material and includes

a switchable material, said switchable material having

a resistive state, and

a conductive state, wherein said switchable material switches from said resistive state to said conductive state upon application of a critical voltage between said first electrode and said second electrode; and

a nonlinear resistive material disposed between said first electrode and said second electrode and in direct contact with the first active material layer, said nonlinear resistive material being electrically in series with said first electrode, said first active material layer, said second active material layer, and said second electrode.

2. The electrical device of claim 1, wherein said first active material layer comprises one or more elements selected from the group consisting of Se and Te and one or more elements selected from the group consisting of Ge, Sb, In, and Bi.

3. The electrical device of claim 1, wherein said switchable material comprises

a chalcogen element and one or more elements selected from the group consisting of Ge, As, Si, and In.

4. The electrical device of claim 1, wherein said switchable material is

a threshold switching material, said threshold switching material having a threshold voltage, said threshold voltage corresponding to said critical voltage.

5. The electrical device of claim 1, wherein said switchable material switches from said conductive state to said resistive state upon removal of said critical voltage.

6. The electrical device of claim 1, wherein said nonlinear resistive material comprises

carbon and nitrogen.

7. The electrical device of claim 6, wherein said nonlinear resistive material includes a sputtered carbon-containing material.

8. The electrical device of claim 7, wherein the sputtered carbon-containing material is formed in the presence of a gas phase ambient that includes nitrogen gas, wherein a partial pressure of said nitrogen gas in said gas phase ambient is at least 20%.

9. The electrical device of claim 7, wherein the sputtered carbon-containing material is formed in the presence of a gas phase ambient that includes nitrogen gas, wherein a partial pressure of said nitrogen gas in said gas phase ambient is at least 40%.

10. The electrical device of claim 1, wherein said nonlinear resistive material has a first state and a second state, said second state being more conductive than said first state, wherein, application of a turn-on voltage provides

means for transforming said nonlinear resistive material from said first state to said second state.

11. The electrical device of claim 10, wherein transformation from said first state to said second state occurs without a discontinuity in voltage or current.

12. The electrical device of claim 10, wherein transformation from said first state to said second state occurs at an approximately constant voltage.

13. The electrical device of claim 10, wherein transformation from said first state to said second state is accompanied by an increase in current.

14. The electrical device of claim 10, wherein a thickness of said nonlinear resistive material is such that said turn-on voltage and said critical voltage differ by less than 1 volt.

15. The electrical device of claim 10, wherein a thickness of said nonlinear resistive material is such that said turn-on voltage and said critical voltage differ by less than 0.5 volt.

16. The electrical device of claim 10, wherein a thickness of said nonlinear resistive material is such that said turn-on voltage and said critical voltage differ by less than 0.1 volt.

17. The electrical device of claim 10, wherein said first state of said nonlinear resistive material is more conductive than said resistive state of said switchable material.

18. The electrical device of claim 17, wherein said first state of said nonlinear resistive material is less conductive than said conductive state of said switchable material.

19. The electrical device of claim 1, wherein said first active material layer does not experience a discontinuity in current or voltage upon said switching of said switchable material.

20. The electrical device of claim 1, wherein said nonlinear resistive material is interconnected between said first electrode and said first active material layer and said second active material layer is interconnected between said first active material layer and said second electrode.

21. The electrical device of claim 1, wherein said first active material layer is interconnected between said nonlinear resistive material and said second active material layer.

22. The electrical device of claim 1, further comprising

a bottom interconnect, said first electrode being interconnected between said bottom interconnect and said first active material layer.

23. The electrical device of claim 1, further comprising:

a first insulator disposed on said nonlinear resistive material, said first insulator having a pore therethrough, said first active material layer occupying said pore and contacting said nonlinear resistive material.

24. The electrical device of claim 23, wherein said nonlinear resistive material contacts said first electrode.

25. The electrical device of claim 23, wherein said second active material layer contacts said first active material layer.

26. The electrical device of claim 1, wherein at least one of the first active material layer and the second active material layer is transformable between

an amorphous state,

a crystalline state, and

a partially crystalline state, wherein the first active material layer is transformable between the amorphous state, the crystalline state and the partially crystalline state whereas the second active material layer includes a predominantly amorphous material that exhibits little tendency to be transformable from the amorphous state to either of the crystalline state or the partially crystalline state.

27. An electrical device comprising:

a first electrode;

a second electrode;

a first active material layer disposed between said first electrode and said second electrode;

a second active material layer disposed between said first electrode and said second electrode, wherein a lower surface of the second active material layer is disposed adjacent an upper surface of the first active material layer wherein said second active material layer differs in composition from said first active material; and

a nonlinear resistive material consisting essentially of carbon and nitrogen that is disposed between said first electrode and said second electrode and in direct contact with the first active material layer, said nonlinear resistive material being electrically in series with said first electrode, said first active material layer, said second active material layer, and said second electrode.

28. The electrical device of claim 27, wherein at least one of the first active material layer and the second active material layer is transformable between

an amorphous state,

a crystalline state, and

a partially crystalline state, wherein the first active material layer is transformable between the amorphous state, the crystalline state and the partially crystalline state whereas the second active material layer includes a predominantly amorphous material that exhibits little tendency to be transformable from the amorphous state to either of the crystalline state or the partially crystalline state.

29. An electrical device comprising:

a first electrode;

a second electrode;

a first layer of material that includes an active material disposed between said first electrode and said second electrode;

a second layer of material including an amorphous active material disposed between said first electrode and said second electrode, wherein a lower surface of the second layer of material is disposed adjacent an upper surface of the first layer of material wherein said second active material layer differs in composition from said first active material; and

a nonlinear resistive material disposed between said first electrode and said second electrode and in direct contact with the first active material layer, said nonlinear resistive material being electrically in series with said first electrode, said first layer of material, said second layer of material, and said second electrode.

30. The electrical device of claim 29, wherein the first layer of material is transformable between an amorphous state, a crystalline state and a partially crystalline state whereas the second layer of material exhibits little tendency to be transformable from the amorphous state to either of the crystalline state or the partially crystalline state.