Magnetic Memory Device Stray Field Cancellation
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Solution Overview
Problem
Magnetoresistive memory devices face challenges in canceling stray magnetic fields and maintaining data reliability due to process variations and external magnetic interference, which affect the magnetization reversal current and data retention.
Innovation Solution
A magnetic memory device design incorporating a magnetic field generating area with invariable magnetization, separated from the magnetoresistive elements, generates a canceling magnetic field that surrounds the memory cell array and functions as a closed magnetic path to shield both stray and external fields, ensuring consistent operation and improved data retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shift cancelling layer is added to cancel stray magnetic field, then magnetization reverse current shifting is reduced, but device complexity increases
Solution Approach 1:
The patent extracts the magnetic field cancellation function from the magnetoresistive element stack and places it in a separate reference layer positioned away from the storage layer. This separation allows the reference layer to generate a compensating magnetic field that cancels the stray field from the storage layer, reducing the shifting of magnetization reverse current without adding complexity to the core magnetoresistive element structure.
Solution Approach 2:
The patent introduces a reference layer with invariable magnetization as an intermediary component that generates a magnetic field to counteract the stray magnetic field from the storage layer. This reference layer acts as a mediator that produces a compensating field, thereby canceling the harmful stray field effect and stabilizing the magnetization reversal process without requiring direct modification of the storage layer or tunnel barrier.
2Area of stationary object
If reference layer and storage layer are positioned close together, then device area is reduced, but stray magnetic field interference increases
Solution Approach 1:
The patent extracts the reference layer from immediate proximity to the storage layer and positions it at a distance, allowing the reference layer to still provide magnetic field compensation while reducing direct magnetic coupling. This spatial separation minimizes the stray magnetic field interference between the reference layer and storage layer, solving the contradiction between compact area and magnetic field interference.
Solution Approach 2:
The patent converts the potentially harmful stray magnetic field from the storage layer into a useful effect by using the reference layer's invariable magnetization to generate a compensating field. The stray field that would normally cause shifting of magnetization reverse current is instead canceled by the reference layer's field, turning the magnetic interaction from harmful to beneficial.
3Reliability
If magnetization reverse current is increased to overcome stray field, then data writing reliability is improved, but energy consumption increases
Solution Approach 1:
The patent applies preliminary anti-action by using the reference layer to generate a magnetic field that counteracts the stray magnetic field from the storage layer before the magnetization reversal process begins. This pre-compensation reduces the shifting of magnetization reverse current, allowing the writing operation to proceed with lower current requirements and improved accuracy without excessive energy consumption.
Solution Approach 2:
The patent implements a magnetic field feedback mechanism where the reference layer's invariable magnetization provides a stable reference field that compensates for variations in the storage layer's stray field. This feedback-like compensation stabilizes the magnetization reversal process, ensuring consistent writing reliability while minimizing the energy required for current reversal by eliminating the need for excessive overdrive current.
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 effectively cancels stray magnetic fields and shields the memory device from external interference, enhancing the reliability of data retention and magnetization reversal, even with process variations, and preventing magnetic field leakage.
Implementation Method 1
a magnetic field generating area which generates a first magnetic field cancelling a second magnetic field applying from the reference layer to the storage layer
Implementation Method 2
a closed magnetic path area functioning as a closed magnetic path of the first magnetic field, and surrounding the memory cell array area and the magnetic field generating area
Implementation Method 3
A magnetoresistive element comprises a reference layer having invariable magnetization, a storage layer having variable magnetization, and a tunnel barrier layer interposed between the reference layer and the storage layer
Data Source
AI summary
According to one embodiment, a magnetic memory device includes a semiconductor substrate, a memory cell array area on the semiconductor substrate, the memory cell array area including magnetoresistive elements, each of the magnetoresistive elements having a reference layer with an invariable magnetization, a storage layer with a variable magnetization, and a tunnel barrier layer therebetween, a magnetic field generating area which generates a first magnetic field cancelling a second magnetic field applying from the reference layer to the storage layer, and which is separated from the magnetoresistive elements, and a closed magnetic path area functioning as a closed magnetic path of the first magnetic field, and surrounding the memory cell array area and the magnetic field generating area.