US6570783B1
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Asymmetric MRAM cell and bit design for improving bit yield
Assignee: Micron Technology Inc
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Filing: 2002-03-12
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Granted: 2003-05-27
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Expires: 2022-03-12
Abstract
Abstract An asymmetric cell and bit design for an MRAM device. The design is asymmetrical with respect to the easy-axis of the cell and has a centroid displaced from bit center along the hard-axis of the cell. This asymmetry is large enough so that manufacturing process variations do not substantially change the switching fields of the bits. In addition, the asymmetry causes the ends of the bits to align in opposite directions in small half-select fields and parallel to each other at large half-select fields, which increases the difference in the switching fields between selected and unselected bits. The combined effect of these two characteristics results in increased bit yield (relative to similarly sized symmetric bits) due to a smaller overlap between selected and unselected bit switching distributions.
Inventors
- 👤 James G. Deak
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 09:55
CPC Classifications
G; G11; G11C; G11C11/00; G11C11/02; G11C11/16; G11C11/14; G11C11/15; G11C11/155; G11C11/161
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
75 words
A magnetic memory cell comprising: a first magnetic layer having a pinned magnetization direction; a second magnetic layer having a switchable magnetization direction; and a non-magnetic layer between said first and second magnetic layers, wherein said cell comprises a hard-axis and an easy-axis, an intersection of the hard-axis and easy-axis defining a center of said cell, and at least said second magnetic layer has a centroid that is displaced along the hard-axis from the center.
Claim 2
Dependent Claim
75 words
A magnetic memory cell comprising: a first magnetic layer having a pinned magnetization direction; a second magnetic layer having a switchable magnetization direction; and a non-magnetic layer between said first and second magnetic layers, wherein said cell comprises a hard-axis and an easy-axis, an intersection of the hard-axis and easy-axis defining a center of said cell, and at least said second magnetic layer has a centroid that is displaced along the hard-axis from the center.
Claim 3
Dependent Claim
28 words
The magnetic memory cell of claim 1 wherein said second magnetic layer is patterned into a lopsided shape with its centroid displaced along the hard-axis from the center.
Claim 4
Dependent Claim
25 words
The magnetic memory cell of claim 1 wherein each of said layers has an associated centroid that is displaced from the center along the hard-axis.
Claim 5
Dependent Claim
34 words
The magnetic memory cell of claim 1 wherein each of said layers has an associated centroid and is patterned into a lopsided shape with its respective centroid displaced along the hard-axis from the center.
Claim 6
Dependent Claim
71 words
The magnetic memory cell of claim 1 wherein said second magnetic layer comprises first and second end regions and a main region, said main region being parallel to said easy-axis and stores the magnetization that is switchable between the first and second directions, and said first and second ends store magnetic fields that align in opposite directions with respect to each other when low half-select fields are applied to the cell.
Claim 7
Dependent Claim
72 words
The magnetic memory cell of claim 1 wherein said second magnetic layer comprises first and second end regions and a main region, said main region being parallel to said easy-axis and stores the magnetization that is switchable between the first and second directions, and said first and second ends store magnetic fields that align in a same direction with respect to each other when high half-select fields are applied to the cell.
Claim 8
Dependent Claim
94 words
A magnetic memory device comprising: a plurality of magnetic memory cells organized into an array of rows and columns, each magnetic memory cell comprising: a first magnetic layer having a pinned magnetization direction; a second magnetic layer having a switchable magnetization direction; and a non-magnetic layer between said first and second magnetic layers; wherein said cell comprises a hard-axis and an easy-axis, an intersection of the hard-axis and easy-axis defining a center of said cell, and at least said second magnetic layer has a centroid that is displaced along the hard-axis from the center.
Claim 9
Dependent Claim
94 words
A magnetic memory device comprising: a plurality of magnetic memory cells organized into an array of rows and columns, each magnetic memory cell comprising: a first magnetic layer having a pinned magnetization direction; a second magnetic layer having a switchable magnetization direction; and a non-magnetic layer between said first and second magnetic layers; wherein said cell comprises a hard-axis and an easy-axis, an intersection of the hard-axis and easy-axis defining a center of said cell, and at least said second magnetic layer has a centroid that is displaced along the hard-axis from the center.
Claim 10
Dependent Claim
36 words
The magnetic memory device of claim 7 wherein said second magnetic layer is patterned into a lopsided shape that is asymmetrical with respect to the easy-axis and its centroid displaced along the hard-axis from the center.
Claim 11
Dependent Claim
23 words
The magnetic memory device of claim 7 wherein each layer has an associated centroid that is displaced from the center along the hard-axis.
Claim 12
Dependent Claim
40 words
The magnetic memory device of claim 7 wherein each layer has an associated centroid, is patterned into a lopsided shape that is asymmetrical with respect to the easy-axis, and has its respective centroid displaced along the hard-axis from the center.
Claim 13
Dependent Claim
71 words
The magnetic memory device of claim 7 wherein said second magnetic layer comprises first and second end, regions and a main region, said main region being parallel to said easy-axis and stores the magnetization that is switchable between the first and second directions, and said first and second ends store magnetic fields that align in opposite directions with respect to each other when low half-select fields are applied to the cell.
Claim 14
Dependent Claim
72 words
The magnetic memory device of claim 7 wherein said second magnetic layer comprises first and second end regions and a main region, said main region being parallel to said easy-axis and stores the magnetization that is switchable between the first and second directions, and said first and second ends store magnetic fields that align in a same direction with respect to each other when high half-select fields are applied to the cell.
Claim 15
Dependent Claim
19 words
The magnetic memory device of claim 7 , wherein said device is a magnetoresistive random access memory (MRAM) device.
Claim 16
Dependent Claim
110 words
A processor system comprising: a processor; and a magnetic memory device coupled to said processor, said magnetic memory device comprising a plurality of magnetic memory cells organized into an array of rows and columns, each magnetic memory cell comprising: a first magnetic layer having a pinned magnetization direction; a second magnetic layer having a switchable magnetization direction; and a non-magnetic layer between said first and said second magnetic layers; wherein said cell comprises a hard-axis and an easy-axis, an intersection of the hard-axis and easy-axis defining a center of said cell, and at least said second magnetic layer has a centroid that is displaced along the hard-axis from the center.
Claim 17
Dependent Claim
110 words
A processor system comprising: a processor; and a magnetic memory device coupled to said processor, said magnetic memory device comprising a plurality of magnetic memory cells organized into an array of rows and columns, each magnetic memory cell comprising: a first magnetic layer having a pinned magnetization direction; a second magnetic layer having a switchable magnetization direction; and a non-magnetic layer between said first and said second magnetic layers; wherein said cell comprises a hard-axis and an easy-axis, an intersection of the hard-axis and easy-axis defining a center of said cell, and at least said second magnetic layer has a centroid that is displaced along the hard-axis from the center.
Claim 18
Dependent Claim
32 words
The system of claim 14 wherein said second magnetic layer has a lopsided shape that is asymmetrical with respect to the easy-axis and its centroid displaced along the hard-axis from the center.
Claim 19
Dependent Claim
20 words
The system of claim 14 wherein each layer has a centroid that is displaced along the hard-axis from the center.
Claim 20
Dependent Claim
29 words
The system of claim 14 wherein each layer has a centroid and is patterned into a lopsided shape having its respective centroid displaced from the center along the hard-axis.
Claim 21
Dependent Claim
69 words
The system of claim 14 wherein said second magnetic layer comprises first and second end regions and a main region, said main region being parallel to said easy-axis and stores the magnetization that is switchable between the first and second directions, and said first and second ends store magnetic fields that align in opposite directions with respect to each other when low half-select fields are applied to the cell.
Claim 22
Dependent Claim
70 words
The system of claim 14 wherein said second magnetic layer comprises first and second end regions and a main region, said main region being parallel to said easy-axis and stores the magnetization that is switchable between the first and second directions, and said first and second ends store magnetic fields that align in a same direction with respect to each other when high half-select fields are applied to the cell.
Claim 23
Dependent Claim
17 words
The system of claim 14 wherein said magnetic memory-device is a magnetoresistive random access memory (MRAM) device.
Claim 24
Dependent Claim
19 words
The system of claim 14 wherein said magnetic memory device is embedded on a same chip as said processor.
Claim 25
Independent Claim
107 words
A method of storing information in a magnetic memory cell, said method comprises the steps of: providing a memory cell having a hard-axis and an easy-axis of magnetization, an intersection of the hard-axis and easy-axis defining a center of said cell, the memory cell comprising a magnetic field that is aligned with the easy-axis in a first direction, the memory cell having a centroid that is displaced along the hard-axis from the center; applying a half-select magnetic field to the cell; and applying a switching magnetic field to the cell, said switching magnetic field causing the magnetic to switch from the first direction to the second direction.
Claim 26
Independent Claim
107 words
A method of storing information in a magnetic memory cell, said method comprises the steps of: providing a memory cell having a hard-axis and an easy-axis of magnetization, an intersection of the hard-axis and easy-axis defining a center of said cell, the memory cell comprising a magnetic field that is aligned with the easy-axis in a first direction, the memory cell having a centroid that is displaced along the hard-axis from the center; applying a half-select magnetic field to the cell; and applying a switching magnetic field to the cell, said switching magnetic field causing the magnetic to switch from the first direction to the second direction.
Claim 27
Dependent Claim
25 words
The method of claim 22 , wherein a domain wall is formed on the cell before the magnetic field is switched to the second direction.
Claim 28
Dependent Claim
82 words
The method of claim 22 , wherein the memory comprises a magnetic layer having first and second end regions and a main region, and wherein the value of said half-select field is below a threshold value so as to cause a first magnetic field to be stored in the first end region and a second magnetic field to be stored in the second end region, wherein the first and second magnetic fields are aligned in opposite directions with respect to each other.
Claim 29
Dependent Claim
83 words
The method of claim 22 , wherein the memory comprises a magnetic layer having first and second end regions and a main region, said method further comprises the step of applying a high half-select field to the cell to cause a first magnetic field to be stored in the first end region and a second magnetic field to be stored in the second end region, wherein the first and second magnetic fields are aligned in a same direction with respect to each other.
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