Magnetic Memory Device Using Spin Orbit Torque
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Solution Overview
Problem
Current magnetic memory devices face challenges in reducing the size of memory cells while maintaining efficient data storage and retrieval operations, particularly in utilizing the spin orbit torque for writing data without external magnetic fields.
Innovation Solution
The magnetic memory device incorporates a three-terminal-type memory cell with a magnetoresistance effect element and two-terminal-type switching elements, utilizing a wiring structure that applies spin orbit torque for writing data, eliminating the need for external magnetic fields and allowing for smaller cell sizes by integrating the switching elements directly with the magnetoresistance effect element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional two-terminal memory cell structure is used, then the device is simple to manufacture, but the cell size cannot be reduced further and write efficiency is limited
Solution Approach 1:
The patent divides the memory cell into three distinct terminals: a first terminal connected to the word line, a second terminal connected to the bit line, and a third terminal connected to the read line. This segmentation allows independent control of write and read operations, enabling smaller cell sizes while maintaining functionality. The three-terminal structure separates the write current path from the read current path, improving both size efficiency and operational control.
Solution Approach 2:
The patent introduces a third terminal dimension to the conventional two-terminal structure, adding vertical stacking of functional layers. The magnetoresistance effect element is positioned between the second and third terminals, while the first terminal provides additional control access. This dimensional expansion enables more compact planar footprint while maintaining three-dimensional functional separation.
2Adaptability or versatility
If external magnetic fields are used for writing data, then the magnetoresistance effect element can be reliably written, but the device requires additional external equipment and cannot be integrated
Solution Approach 1:
The patent replaces the external magnetic field system with an electrical current-based spin-orbit torque system. By passing current through the magnetoresistance effect element, spin-orbit torque is generated to switch the magnetization state of the ferromagnetic layer. This substitution eliminates the need for external magnetic field generation equipment, enabling full integration while maintaining reliable data writing through electrical control.
Solution Approach 2:
The magnetoresistance effect element generates the necessary torque for magnetization switching through its own internal spin-orbit coupling mechanism when current flows through it. The heavy metal layer or topological insulator within the element structure converts charge current directly into spin current, which then exerts torque on the ferromagnetic layer. This self-service mechanism eliminates external intervention and enables scalable integration.
3Reliability
If high current is applied during read operations, then data can be read reliably, but the magnetoresistance effect element suffers from high voltage stress and reduced endurance
Solution Approach 1:
The patent segments the current path into separate write and read paths. During read operations, current flows only between the second and third terminals through the magnetoresistance effect element, while the first terminal remains inactive. This segmentation allows optimized read current levels that are sufficient for reliable detection without reaching the high current thresholds that would cause damage, thereby extending element endurance.
Solution Approach 2:
The patent introduces a switching element as an intermediary between the read line and the magnetoresistance effect element. This switching element controls and limits the read current, ensuring it remains within safe operating boundaries while still providing sufficient signal for reliable data detection. The intermediary protects the magnetoresistance effect element from voltage stress during read operations.
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 configuration enables efficient data storage and retrieval operations with reduced cell size, improved write current flow, and enhanced endurance of the magnetoresistance effect element, preventing unintentional high voltage application during read operations.
Implementation Method 1
a first magnetoresistance effect element connected between the third conductor layer and the fourth conductor layer
Implementation Method 2
a nonmagnetic layer including a first portion connected to the word line, a second portion connected to the write bit line, and a third portion connected to the read bit line, the nonmagnetic layer having a high spin orbit coupling constant
Data Source
AI summary
According to one embodiment, a magnetic memory device includes first to third conductor layers, and a three-terminal-type memory cell connected to the first to third conductor layers. The first memory cell includes a fourth conductor layer, a magnetoresistance effect element, a two-terminal-type first switching element, and a two-terminal-type second switching element. The fourth conductor layer includes a first portion connected to the first conductor layer, a second portion connected to the second conductor layer, and a third portion which is connected to the third conductor layer. The magnetoresistance effect element is connected between the third conductor layer and the fourth conductor layer. The first switching element is connected between the second conductor layer and the fourth conductor layer. The second switching element is connected between the first conductor layer and the third conductor layer.