Magnetic Biasing Structure for MRAM Write Selectivity
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Solution Overview
Problem
Conventional magnetic memory elements in MRAM suffer from poor write selectivity and high write current requirements due to variations in internal magnetic fields caused by manufacturing defects and size/shape variations, leading to unintentional cell writing and increased power consumption.
Innovation Solution
A magnetic biasing structure is introduced with a first pinned layer, a second pinned layer oriented perpendicular to the first, a nonferromagnetic spacer layer, and a free layer with anisotropy parallel to the second direction, providing a hard or easy axis bias field to improve switching characteristics and reduce write current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional magnetic elements are used in MRAM, then data storage function is achieved, but write selectivity is poor and write current is high
Solution Approach 1:
The magnetic element is segmented into multiple functional layers including pinned layers, free layer, and barrier layer, each with specific magnetic properties. The pinned layers have fixed magnetization directions while the free layer has variable magnetization, allowing selective switching. This segmentation enables better control over write operations and reduces the required write current by confining the switching action to specific regions.
Solution Approach 2:
Different layers are assigned different magnetic qualities: the pinned layers have high coercivity and fixed magnetization, the free layer has lower coercivity and variable magnetization, and the barrier layer provides spin-dependent scattering. This local differentiation of magnetic properties allows the write operation to affect only the intended cell by exploiting the specific magnetic characteristics of each layer, improving write selectivity while reducing write current.
2Reliability
If conventional magnetic elements are used in MRAM, then data storage is achieved, but manufacturing variations cause large distribution in required write field
Solution Approach 1:
The invention changes the magnetic parameters of different layers to achieve robust switching characteristics. By setting the pinned layers with high coercivity and the free layer with lower coercivity, and by controlling the thickness and composition of the barrier layer, the system achieves a write field distribution that is less sensitive to manufacturing variations in size and shape. This parameter optimization ensures uniform switching behavior across devices with varying dimensions.
3Reliability
If high write current is applied to conventional magnetic elements, then switching is achieved, but unintentional cell writing occurs
Solution Approach 1:
The barrier layer acts as an intermediary that mediates the interaction between the pinned layers and the free layer. It provides spin-dependent scattering that transfers angular momentum selectively, enabling the write operation to switch the free layer magnetization without affecting adjacent cells. This intermediary mechanism allows reliable switching at lower current densities, preventing unintentional cell writing while maintaining switching reliability.
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
The magnetic biasing structure enhances switching uniformity and reduces the required write current, minimizing unintentional cell writing and power consumption while maintaining reliable data storage in MRAM.
Implementation Method 1
The spacer layer is configured such that the free layer is substantially free of exchange coupling with the second pinned layer
Implementation Method 2
Depending upon the orientations of the magnetization 19/19′ of the conventional free layer 18/18′ and the conventional pinned layer 14/14′, respectively, the resistance of the conventional magnetic element 10/10′, respectively, changes
Implementation Method 3
the conventional barrier layer 16′ is an insulator that is thin enough for electrons to tunnel through in a conventional spin tunneling junction 10′
Implementation Method 4
the magnetization 19/19′ of the free layer 18/18′ can be switched to have an equilibrium position parallel or antiparallel to the magnetization of the pinned layer 14/14′
Data Source
AI summary
A method and system for providing a magnetic element are disclosed. The method and system include providing a magnetic biasing structure having a first pinned layer, a second pinned layer, a spacer layer, and a free layer. The first pinned layer has a first magnetization pinned in the first direction. The second pinned layer has a second magnetization in a second direction that is substantially perpendicular or along the first direction. The spacer layer is nonferromagnetic, resides between the second pinned layer and the free layer, and is configured such that the free layer is substantially free of exchange coupling with the second pinned layer. The free layer has a shape anisotropy with a longitudinal direction substantially in the second direction. The magnetic biasing structure provides a bias field for the free layer along the hard or easy axis. In one aspect, the second pinned layer resides between the first pinned layer and the free layer.