Complementary Magnetic Memory Cell with Unidirectional Write Current
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional MRAM technologies face challenges such as write asymmetry, high read error rates, and area overhead due to the limitations of spin transfer torque (STT) and spin orbit torque (SOT) technologies, particularly in reducing current requirements and minimizing device breakdown.
Innovation Solution
A complementary magnetic memory cell utilizing a pair of magnetic tunnel junctions with complementary resistance states, where one junction is set to a high resistance state and the other to a low resistance state, using spin orbit torque and spin transfer torque to optimize write operations and reduce read errors, with a unidirectional current requirement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If spin transfer torque (STT) technology is used to write data in MRAM, then the current requirement can be reduced as device size decreases, but the write current directly passes through the ultra-thin barrier layer causing breakdown and failure, and the power consumption and delay for writing from low resistance state to high resistance state are larger
Solution Approach 1:
The patent segments the write current path from the read current path by introducing a separate write electrode that applies current to the heavy metal film underneath the magnetic tunnel junction. This segmentation allows the write current to flow through a different path that does not pass through the ultra-thin barrier layer, thereby reducing breakdown risk while maintaining low power consumption for writing operations.
Solution Approach 2:
The patent introduces a heavy metal film as an intermediary layer between the write electrode and the magnetic tunnel junction. This intermediary enables spin orbit torque to be generated without requiring current to pass through the vulnerable barrier layer, thus protecting the device from breakdown while still achieving effective magnetization switching.
2Reliability
If spin orbit torque (SOT) technology is used to write data in MRAM, then the read and write paths are separated reducing barrier breakdown risk, but the memory cell requires three terminals and typically two access transistors causing additional area overhead
Solution Approach 1:
The patent merges the read and write functions into a two-terminal magnetic tunnel junction structure. By using complementary resistance states and a unidirectional write current applied through the heavy metal film, the patent achieves separate read and write paths without requiring additional access transistors or three-terminal configurations, thereby reducing area overhead while maintaining reliability.
Solution Approach 2:
The magnetic tunnel junction in the patent serves multiple functions: it acts as both the storage element and the sensing element, while the heavy metal film serves as both the spin source for writing and part of the read path. This multi-functionality eliminates the need for separate access transistors and reduces overall device complexity.
3Productivity
If conventional MRAM uses magnetic fields to achieve data writing, then data can be written, but the current required for magnetic field writing cannot be reduced as device size decreases
Solution Approach 1:
The patent replaces the magnetic field-based writing mechanism (which relies on current loops generating external magnetic fields) with a spin transfer torque mechanism that directly transfers angular momentum from spin-polarized current to the magnetization. This substitution allows the write current to be reduced proportionally with device size, improving energy efficiency while maintaining data writing capability.
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 approach reduces read error rates, minimizes power consumption, and eliminates area overhead by using a unidirectional current for writing, while maintaining high read sensing margins and efficient data storage.
Implementation Method 1
spin transfer torque (STT) technology has been proposed and applied to write operations of MRAM
Implementation Method 2
Recently proposed spin orbit torque (SOT) technology also implements data writing of MRAM through current
Implementation Method 3
a magnetic random access memory (MRAM) based on a magnetic tunnel junction
Data Source
AI summary
A complementary magnetic memory cell includes: a heavy metal film or an antiferromagnetic film, a first magnetic tunnel junction, a second magnetic tunnel junction, a first electrode, a second electrode, a third electrode, a fourth electrode, and a fifth electrode; wherein the first magnetic tunnel junction and the second magnetic tunnel junction are fabricated above the heavy metal film or the antiferromagnetic film; the first electrode, the second electrode and the third electrode are fabricated under the heavy metal film or the antiferromagnetic film; the fourth electrode is fabricated above the first magnetic tunnel junction, and the fifth electrode is fabricated above the second magnetic tunnel junction; to store one bit of data, the first magnetic tunnel junction and the second magnetic tunnel junction are arranged in a pair of complementary resistance states, wherein one magnetic tunnel junction is set to a high resistance state and the other remains unchanged.