Systems and methods utilizing serial and parallel configurations of magnetic memory devices

Patent metadata

Field	Value
Publication number	US-10937478-B2
Application number	US-201916506878-A
Country	US
Kind code	B2
Filing date	Jul 9, 2019
Priority date	Dec 29, 2017
Publication date	Mar 2, 2021
Grant date	Mar 2, 2021

Abstract

An apparatus includes two or more magnetic tunnel junctions (MTJs), including a first MTJ having a first magnetic characteristic and a second MTJ having a second magnetic characteristic. The first magnetic characteristic is distinct from the second magnetic characteristic. The first magnetic characteristic is based on a first magnetic anisotropy and a first offset field on a first storage layer of the first MTJ. The second magnetic characteristic is based on a second magnetic anisotropy and a second offset field on a second storage layer of the second MTJ, The apparatus further includes a metallic separator coupling the first MTJ with the second MTJ, wherein the first MTJ and the second MTJ are arranged in series.

First claim

What is claimed is:

1. An apparatus comprising:
two or more perpendicular magnetic tunnel junctions (MTJs), including a first perpendicular MTJ having a first magnetic characteristic and a first size and a second perpendicular MTJ having a second magnetic characteristic and a second size that is distinct from the first size, wherein:
the first magnetic characteristic is distinct from the second magnetic characteristic;
the first magnetic characteristic is based on a first magnetic anisotropy and a first offset field on a first storage layer of the first MTJ that is based in part on the first size;
the second magnetic characteristic is based on a second magnetic anisotropy and a second offset field on a second storage layer of the second MTJ that is based in part on the second size; and

a metallic separator coupling the first MTJ with the second MTJ, wherein the first MTJ and the second MTJ are arranged in series, wherein:
the apparatus is responsive to a single or multi-level voltage pulse for writing one or more bits to the two or more MTJs, and writing the one or more bits changes a magnetic state of the first MTJ; and
the single or multi-level voltage pulse is received at a peripheral layer of the two or more perpendicular MTJs.

2. The apparatus of claim 1 , wherein each respective MTJ has a respective magnetic characteristic determined by one or more material compositions of the respective MTJ, wherein the material compositions include materials selected from the group consisting of MgO, CoFeB, Cobalt, Platinum, Ruthenium, Tungsten, and Tantalum.

3. The apparatus of claim 1 , wherein each respective MTJ has a distinct switching current value which is determined by the magnetic characteristic of the respective MTJ.

4. The apparatus of claim 1 , further comprising:
a third perpendicular MTJ having a third magnetic characteristic and a third electrical characteristic, wherein the third magnetic characteristic is distinct from the first magnetic characteristic and the second magnetic characteristic; and
a second metallic separator coupling the third perpendicular MTJ with the second MTJ, wherein the first MTJ, the second MTJ, and the third MTJ are arranged in series.

5. The apparatus of claim 1 , wherein a total resistance measured across the two or more MTJs may have a maximum of 2 n discrete values, where n is a number of MTJs of the two or more MTJs.

6. The apparatus of claim 5 , wherein the two or more MTJs can store a fewer number of bits than the maximum of 2 n discrete values.

7. The apparatus of claim 1 , wherein the first size comprises a first radius and the second size comprises a second radius that is distinct from the first radius.

8. The apparatus of claim 1 wherein the magnetic state of the first MTJ is a parallel magnetic state or an anti-parallel magnetic state.

9. An apparatus comprising:
two or more perpendicular magnetic tunnel junctions (MTJs), including a first perpendicular MTJ having a first magnetic characteristic and a first electrical characteristic and a second perpendicular MTJ having a second magnetic characteristic and a second electrical characteristic, wherein:
the first magnetic characteristic is distinct from the second magnetic characteristic;
the first electrical characteristic of the first MTJ is a first resistance determined based on a geometric property of the first MTJ that includes a first diameter of the first MTJ and a Resistance x Area product (RA product) of the first MTJ, the Area of the first MTJ including the first diameter; and
the second electrical characteristic of the second MTJ is a second resistance determined based on a geometric property of the second MTJ that includes a second diameter of the second MTJ and an RA product of the second MTJ the Area of the second MTJ including the second diameter; and

a metallic separator coupling the first MTJ with the second MTJ, wherein the first MTJ and the second MTJ are arranged in series, wherein:
the apparatus is responsive to a single or multi-level voltage pulse for writing one or more bits to the two or more MTJs, and writing the one or more bits changes a magnetic state of the first MTJ; and
the single or multi-level voltage pulse is received at a peripheral layer of the two or more perpendicular MTJs.

10. The apparatus of claim 9 , wherein the first electrical characteristic is distinct from the second electrical characteristic.

11. The apparatus of claim 9 , wherein the first electrical characteristic has the same value as the second electrical characteristic.

12. The apparatus of claim 9 , wherein the geometric property of each MTJ is further selected from the group consisting of area and thickness.

13. The apparatus of claim 9 , wherein the geometric property of each MTJ is based on an order of stacking a reference layer, a spacer layer, and a storage layer of each MTJ.

14. An apparatus comprising:
two or more magnetic tunnel junctions (MTJs), including a first MTJ having a first magnetic characteristic and a second MTJ having a second magnetic characteristic, wherein the first magnetic characteristic is distinct from the second magnetic characteristic; and
a metallic separator coupling the first MTJ with the second MTJ, wherein:
the first MTJ and the second MTJ are arranged in series; and
the first MTJ is arranged in an offset position from the second MTJ so as to minimize influence of stray fields between the first and second MTJs.

15. The apparatus of claim 14 , wherein two or more MTJs may have a maximum of 2 n bits stored, where n is a number of MTJs of the two or more MTJs.

16. The apparatus of claim 14 , wherein the apparatus is responsive to instructions for reading a resistance across the two or more MTJs to determine one or more bits that are stored in each MTJ of the two or more MTJs.

17. The apparatus of claim 14 , wherein the first MTJ is in a first magnetic state and the second MTJ is in the first magnetic state, which creates a first resistance measured across the first MTJ and the second MTJ.

18. The apparatus of claim 17 , wherein the first MTJ is in a second magnetic state and the second MTJ is in the first magnetic state, creating a second resistance, measured across the first MTJ and the second MTJ, distinct from the first resistance.

19. The apparatus of claim 18 , wherein the first MTJ is in the first magnetic state and the second MTJ is in the second magnetic state, creating a third resistance, measured across the first MTJ and the second MTJ, distinct from the first resistance and the second resistance.

20. The apparatus of claim 19 , wherein the first MTJ is in the second magnetic state and the second MTJ is in the second magnetic state, creating a fourth resistance, measured across the first MTJ and the second MTJ, distinct from the first resistance, the second resistance, and the third resistance.

21. The apparatus of claim 14 , wherein a total resistance measured across the first MTJ and the second MTJ is discrete based on a magnetic state of the first MTJ and the magnetic state of the second MTJ.

Assignees

• Spin Memory Inc

Inventors

• Bozdag Kadriye Deniz
• Gajek Marcin
• El Baraji Mourad
• Ryan Eric Michael

Classifications

• H10N50/85

  Materials of the active region · CPC title

• G11C11/00

  Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor (G11C14/00 - G11C21/00 take precedence) · CPC title

• G11C11/15 Primary

  using multiple magnetic layers (G11C11/155 takes precedence) · CPC title

• G11C11/161

  details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell · CPC title

• G11C11/1675

  Writing or programming circuits or methods · CPC title