Self-Referenced MRAM Element with Perpendicular Sense Magnetization
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Solution Overview
Problem
Magnetic random access memory (MRAM) cells face challenges in scaling down due to increased dipolar coupling between storage and sense layers, which requires high magnetic fields for read operations, leading to power consumption issues and reduced reliability.
Innovation Solution
The MRAM element incorporates a magnetic tunnel junction with a storage layer and a sense layer, along with a tunnel barrier layer, and an aligning device that provides magnetic anisotropy perpendicular to the storage magnetization, allowing for a low reading magnetic field to adjust the sense magnetization and vary junction resistance linearly, reducing power consumption and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the magnetic tunnel junction diameter is reduced to scale down the MRAM cell, then the device size is reduced, but the dipolar coupling between storage and sense layers increases
Solution Approach 1:
The patent extracts the harmful dipolar coupling effect by introducing a non-magnetic spacer layer that physically separates the storage and sense layers, preventing their magnetic interactions while maintaining the scaled-down device structure
Solution Approach 2:
The non-magnetic spacer layer acts as an intermediary between the storage and sense layers, blocking the magnetic field interaction while allowing the device to function at smaller dimensions without excessive dipolar coupling
2Reliability
If a high magnetic field is applied to overcome the dipolar coupling during read operation, then the read operation can be performed, but the power consumption increases
Solution Approach 1:
The patent converts the harmful dipolar coupling into a beneficial effect by designing the sense layer with perpendicular magnetic anisotropy, where the dipolar field from the storage layer assists in switching the sense layer magnetization during read operations, eliminating the need for high external magnetic fields and reducing power consumption
3Measurement precision
If the sense layer magnetization is coupled with the storage layer magnetization through dipolar coupling, then the hysteresis loop is shifted, but the reading magnetic field must be increased to overcome this coupling
Solution Approach 1:
The patent introduces asymmetry in the magnetic configuration by giving the sense layer perpendicular magnetic anisotropy while the storage layer maintains in-plane magnetization, creating orthogonal magnetization directions that eliminate dipolar coupling effects and simplify the hysteresis loop measurement
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables reliable read operations with low power consumption, even in the presence of strong dipolar offsets, by adjusting the sense magnetization with a small read magnetic field, thereby reducing power dissipation and simplifying design and manufacturing control.
Implementation Method 1
the magnetic tunnel junction having a magnetoresistance corresponding to the difference between a high junction resistance value where the sense magnetization is antiparallel to the storage magnetization, and a low junction resistance value where the sense magnetization is parallel to the storage magnetization
Implementation Method 2
said aligning device can comprise a second antiferromagnetic layer exchange coupling the sense layer such as to pin the sense magnetization along the second direction
Implementation Method 3
a dipolar coupling between the storage and sense layers occurs due to local magnetic stray field, coupling the magnetization of the sense layer with the one of the storage layer
Data Source
Figure 1
Figure 2(a)~3
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AI summary
The present disclosure concerns a self-referenced random access memory (MRAM) element (1), comprising a magnetic tunnel junction (2) having a magnetoresistance (MR), comprising: a storage layer (23) having a storage magnetization (231) that is pinned along a first direction (60) when the magnetic tunnel junction (2) is at a low temperature threshold; a sense layer (21) having a sense magnetization (211); and a tunnel barrier layer (22) included between the storage layer (23) and the sense layer (21); and an aligning device (20, 5, 52) arranged for providing the sense magnetization (211) with a magnetic anisotropy along a second direction (61) that is substantially perpendicular to the first direction (60) such that the sense magnetization (211) is adjusted about the second direction (61); the aligning device (20, 5, 52) being further arranged such that, when a first read magnetic field (44) is provided, a resistance variation range (VR) of the magnetic tunnel junction (2) is at least about 20% of the magnetoresistance (MR). The self-referenced MRAM cell can be read with an increased reliability and has reducing power consumption.