Systems and methods utilizing parallel configurations of magnetic memory devices

• US 10,347,308 B1
• Filed: 12/29/2017
• Issued: 07/09/2019
• Est. Priority Date: 12/29/2017
• Status: Active Grant

• Current Assignee: Integrated Silicon Solution Incorporated (Uphill Investment Co.)
• Original Assignee: Spin Memory, Inc.
• Inventors: Bozdag, Kadriye Deniz, Gajek, Marcin, El Baraji, Mourad, Ryan, Eric Michael
• Primary Examiner(s): Ojha, Ajay
• Application Number:
  US15/859,259
• Publication Number:
  US 20190206939A1
• Time in Patent Office: 557 Days
• CPC Class Codes: G11C 11/00 Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor G11C14/00 - G11C21/00 take precedence
• CPC Class Codes: G11C 11/15 using multiple magnetic layers G11C11/155 takes precedence
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: G11C 11/1673 Reading or sensing circuits or methods
• CPC Class Codes: G11C 11/1675 Writing or programming circuits or methods
• CPC Class Codes: H10B 61/22 of the field-effect transistor [FET] type
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/80 Constructional details
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

A magnetic storage device is provided. The magnetic storage device comprises a magnetic memory cell, which includes two or more magnetic tunnel junctions (MTJs), including a first MTJ having a first magnetic characteristic and a first electrical characteristic and a second MTJ has a second magnetic characteristic and a second electrical characteristic, wherein the first magnetic characteristic is distinct from the second magnetic characteristic. The magnetic memory cell further comprises a bottom electrode and a top electrode, wherein the two or more MTJs are arranged between the top and bottom electrode in parallel with respect to each other. The magnetic storage device further comprises readout circuitry coupled to the bottom electrode or the top electrode of the magnetic memory cell and write circuitry coupled to the bottom electrode or the top electrode of the magnetic memory cell.

Claims

1. A magnetic storage device, comprising:

a magnetic memory cell, comprising;

two or more magnetic tunnel junctions (MTJs) electrically coupled in parallel, including a first MTJ having a first magnetic characteristic and a first electrical characteristic and a second MTJ has a second magnetic characteristic and a second electrical characteristic, wherein the first magnetic characteristic is distinct from the second magnetic characteristic; and

a bottom electrode and a top electrode, wherein;

the two or more MTJs are arranged in parallel with one another between the top and bottom electrode;

each respective MTJ of the two or more MTJs has a distinct switching current threshold for changing a magnetic state of the MTJ from a first magnetic state to a second magnetic state using a current applied to the respective MTJ; and

a switching current threshold of the first MTJ is distinct from the switching current threshold of the second MTJ and is based at least in part on a difference in composition of the first MTJ and the second MTJ arranged between the top electrode and the bottom electrode;

readout circuitry coupled to the bottom electrode or the top electrode of the magnetic memory cell; and

write circuitry coupled to the bottom electrode or the top electrode of the magnetic memory cell.

2. The magnetic storage device of claim 1, wherein:

each MTJ of the first MTJ and the second MTJ includes a storage layer;

the first magnetic characteristic of the first MTJ is based on a magnetic anisotropy and an offset field on the storage layer of the first MTJ; and

the second magnetic characteristic of the second MTJ is based on a magnetic anisotropy and an offset field on the storage layer of the second MTJ.

3. The magnetic storage device of claim 1, wherein:

the first electrical characteristic of the first MTJ is based on a geometric property of the first MTJ and a Resistance-Area product (RA product) of the first MTJ;

the second electrical characteristic of the second MTJ is based on a geometric property of the second MTJ and an RA product of the second MTJ.

4. The magnetic storage device of claim 3, wherein the geometric property of the first MTJ is distinct from the geometric property of the second MTJ.

5. The magnetic storage device of claim 3, wherein the geometric property of each MTJ is selected from the group consisting of area, diameter, width, and thickness.

6. The magnetic storage device of claim 1, wherein the magnetic state of the MTJ is a parallel magnetic state or an anti-parallel magnetic state.

7. The magnetic storage device of claim 1, wherein each MTJ has a resistance that changes in accordance with a change in the magnetic state of the MTJ.

8. The magnetic storage device of claim 7, wherein the switching current threshold of a respective MTJ is based on the magnetic state and the resistance of the MTJ.

9. The magnetic storage device of claim 1, wherein a switching current threshold of the first MTJ is distinct from the switching current threshold of the second MTJ based at least in part on stray fields from a reference layer of the first MTJ.

10. The magnetic storage device of claim 1, wherein the first MTJ and the second MTJ are each in the first magnetic state, corresponding to a first resistance measured across the magnetic memory cell.

11. The magnetic storage device of claim 10, wherein the first MTJ is in the second magnetic state and the second MTJ is in the first magnetic state, corresponding to a second resistance measured across the magnetic memory cell, the second resistance distinct from the first resistance.

12. The magnetic storage device of claim 11, wherein the first MTJ is in the first magnetic state and the second MTJ is in the second magnetic state, corresponding to a third resistance measured across the magnetic memory cell, the third resistance distinct from the first resistance and the second resistance.

13. The magnetic storage device of claim 12, wherein the first MTJ and the second MTJ are each in the second magnetic state, corresponding to a fourth resistance measured across the magnetic memory cell, the fourth resistance distinct from the first resistance, the second resistance, and the third resistance.

14. The magnetic storage device of claim 1, wherein the magnetic memory cell further comprises a third MTJ having a third magnetic characteristic that is distinct from the first magnetic characteristic and the second magnetic characteristic and having a third electrical characteristic, wherein the third MTJ is arranged in parallel with the first MTJ and the second MTJ.

15. The magnetic storage device of claim 1, wherein:

the magnetic memory cell is responsive to a first voltage pulse for writing to the first MTJ; and

the magnetic memory cell is responsive to a second voltage pulse for writing to the second MTJ, the second voltage pulse distinct from the first voltage pulse.

16. The magnetic storage device of claim 1, wherein the magnetic memory cell is responsive to a single voltage pulse for writing to both the first MTJ and the second MTJ.

17. The magnetic storage device of claim 1, wherein the magnetic memory cell is responsive to a third voltage pulse for reading a bit from the magnetic memory cell.