Low-current and high-speed phase-change memory devices and methods of driving the same

• US 6,967,865 B2
• Filed: 03/23/2004
• Issued: 11/22/2005
• Est. Priority Date: 04/04/2003
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Se-ho
• Primary Examiner(s): PHUNG, ANH K
• Application Number:
  US10/807,077
• Publication Number:
  US 20040202017A1
• Time in Patent Office: 609 Days
• Field of Search: 365/163, 365/148, 365/113
• US Class Current: 365/163
• CPC Class Codes: G11C 11/5678 using amorphous/crystalline phase transition storage elements
• CPC Class Codes: G11C 13/0004 comprising amorphous/crystalline phase transition cells
• CPC Class Codes: G11C 13/004 Reading or sensing circuits or methods
• CPC Class Codes: G11C 13/0069 Writing or programming circuits or methods
• CPC Class Codes: G11C 2013/0054 Read is performed on a reference element, e.g. cell, and the reference sensed value is used to compare the sensed value of the selected cell
• CPC Class Codes: G11C 2013/0078 Write using current through the cell
• CPC Class Codes: G11C 2213/79 Array wherein the access device being a transistor
• CPC Class Codes: H10B 63/30 comprising selection components having three or more electrodes, e.g. transistors
• 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
• CPC Class Codes: H10N 70/884 based on at least one element of group IIIA, IVA or VA, e.g. elemental or compound semiconductors compounds of sulfur, selenium or tellurium, e.g. chalcogenides H10N70/882; oxides or nitrides H10N70/883

Abstract

Phase-change memories in which phase is changed by varying the resistance by a small amount are provided. In the phase-change memory, a set state is defined as a state where amorphous nuclei are formed in a phase-change layer of a memory cell and the phase-change layer has an initial resistance that is higher than in a crystalline matrix, and a reset state is defined as a state where the number and/or the density of the amorphous nuclei are greater than those in the set state and a resistance is higher than in the set state. A current for writing the reset and set states is reduced to several hundred microamperes, and a period required for writing the reset and set states is reduced to several tens of nanoseconds to several hundred nanoseconds.

Claims

1. A phase-change memory comprising:

a first electrode contact;

a phase-change layer on the first electrode contact; and

a second electrode contact on the phase-change layer, wherein a set state is a state in which amorphous nuclei are formed in the phase-change layer that has a set resistance of from about 4 kΩ

to 6 kΩ

, and a reset state is a state in which the number and density of the amorphous nuclei are greater than in the set state and has a reset resistance of about 6 kΩ

to 20 kΩ

.

2. The phase-change memory of claim 1, wherein a current for writing the reset state and/or the set state on the phase-change layer is from about 10 μ

A to about 200 μ

A, and a period required for writing the reset state and/or the set state from the phase-change layer is from about 10 nanoseconds to about 100 nanoseconds.

3. The phase-change memory of claim 1, wherein a current for writing the set state in the phase-change layer is from about 30 μ

A to about 50 μ

A, and a current for writing the reset state in the phase-change layer is from about 60 μ

A to about 200 μ

A.

4. The phase-change memory of claim 1, wherein a diameter of the first electrode contact to which the current is applied to write the reset and set states in the phase-change layer is from about 40 nanometers to about 70 nanometers.

5. The phase-change memory of claim 1, wherein a rising time and a falling time for writing the reset state and/or the set state in the phase-change layer is from about 1 nanosecond to about 4 nanoseconds.

6. The phase-change memory of claim 1, wherein a current for reading the reset state and/or the set state is from about 3 μ

A to about 6 μ

A, and a time required for reading the reset state and/or the set state is from about 5 nanoseconds to about 10 nanoseconds.

7. The phase-change memory of claim 2, wherein a current for reading the reset state and/or the set state is from about 3 μ

A to about 6 μ

A, and a time required for reading the reset state and/or the set state is from 5 nanoseconds to about 10 nanoseconds.

8. A phase change memory, comprising:

first and second electrode contacts;

a phase-change layer between the first and second electrode contacts, the phase change layer providing a first state established by a first number of amorphous nuclei in a crystalline matrix in a region adjacent an interface between the phase-change layer and the first electrode.

9. The phase change memory of claim 8, wherein the phase change layer further provides a second state established by a second number of amorphous nuclei in a crystalline matrix in the region adjacent the interface between the phase-change layer and the first electrode, the second number being greater than the first number.

10. The phase change memory of claim 9, wherein the first number of amorphous nuclei and the second number of amorphous nuclei provide a ratio of resistances of the phase-change layer of from about 1.5 to about 3.

11. The phase change memory of claim 9, wherein the first state of the phase-change layer provides a resistance of the phase-change layer of from about 4 to about 6 kΩ

and the second state the phase-change layer provides a resistance of the phase-change layer of from about 6to about 20 kΩ

.

12. The phase change memory of claim 9, wherein a current for writing the first state or the second state on the phase-change layer is from about 10 μ

A to about 200 μ

A, and a period required for writing the first state or the second state from the phase-change layer is from about 10 nanoseconds to about 100 nanoseconds.

13. The phase change memory of claim 9, wherein a current required for writing the first state in the phase-change layer is from about 30 μ

A to about 50 μ

A, and a current required for writing the second state in the phase-change layer is from about 60 μ

A to about 200 μ

A.

14. The phase change memory of claim 9, wherein a diameter of the first electrode contact to which a current is applied to write the first and second states in the phase-change layer is from about 40 nanometers to about 70 nanometers.

15. The phase change memory of claim 9, wherein a current for reading the first state and/or the second state is from about 3 μ

A to about 6 μ

A, and a time required for reading the first state and/or the second state is from about 5 nanoseconds to about 10 nanoseconds.

16. A method of operating a phase change memory, comprising:

establishing logic states in a phase change memory by controlling amorphous nucleation in a crystalline matrix of a phase-changeable material.

17. The method of claim 16, wherein a first logic state is established by a first number of amorphous nuclei in the crystalline matrix and a second logic state is established by a second number of amorphous nuclei in the crystalline matrix, the second number being greater than the first number.

18. The method of claim 17, wherein the first number of amorphous nuclei and the second number of amorphous nuclei provide a ratio of resistances of the phase-changeable material of from about 1.5 to about 3.

19. The method of claim 17, wherein the first logic state provides a resistance of the phase-change layer of from about 4 kΩ

to about 6 kΩ and

the second logic state provides a resistance of the phase-change layer of from about 6 kΩ

to about 20 kΩ

.

20. The method of claim 17, wherein controlling amorphous nucleation comprises controlling a current for writing the first logic state or the second logic state to be from about 10 μ

A to about 200 μ

A, and a period required for writing the first logic state or the second logic state to be from about 10 nanoseconds to about 100 nanoseconds.

21. The method of claim 17, wherein controlling amorphous nucleation comprises:

controlling a current for writing the first logic state to be from about 30 μ

A to about 50 μ

A; and

controlling a current or writing the second logic state to be from about 60 μ

A to about 200 μ

A.

22. The method of claim 17, wherein a diameter of the first electrode contact to which a current is applied to write the first and second logic states is from about 40 nanometers to about 70 nanometers.

23. The method of claim 17, further comprising controlling a current for reading the first logic state and/or the second logic state to be from about 3 μ

A to about 6 μ

A, and a time for reading the first state and/or the second state to be from about 5 nanoseconds to about 10 nanoseconds.