Magnetic tunnel junction element and magnetoresistive memory device
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Solution Overview
Problem
Current magnetoresistive memory devices face challenges in achieving high thermal stability and reliability at wide operating temperatures due to the deterioration of magnetic anisotropy at high temperatures, particularly in structures like the TcC structure, and have limited material selection for high perpendicular magnetic anisotropy and spin polarization.
Innovation Solution
A magnetic tunnel junction element is designed with a fixed layer, an insulating layer, and an antiferromagnetic oxide layer sequentially stacked, where the antiferromagnetic oxide layer is in direct contact with the free layer, providing perpendicular magnetic anisotropy and a bias magnetic field to enable low power, high-speed reversal, and high reliability across a wide temperature range of -40°C to 150°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a TcC structure with high magnetic anisotropy layer is used to achieve perpendicular magnetization holding, then thermal stability is improved at low temperatures, but thermal stability deteriorates at high temperatures due to rapid deterioration of magnetic anisotropy
Solution Approach 1:
The patent employs a composite structure consisting of a CoFeB free layer with perpendicular magnetic anisotropy and an FeCoB cap layer with in-plane magnetization. This composite material approach allows the perpendicular magnetization to be maintained through interfacial anisotropy while the FeCoB cap layer provides thermal stability at high temperatures by preventing unwanted magnetization switching, thus resolving the temperature-dependent thermal stability issue.
Solution Approach 2:
The patent modifies the magnetic anisotropy parameters by controlling the thickness and composition of the CoFeB free layer and FeCoB cap layer. By adjusting these parameters, the perpendicular magnetic anisotropy is optimized for low-temperature operation while the overall structure maintains thermal stability across a wide temperature range, addressing the contradiction between thermal stability and operating temperature range.
2Reliability
If multiple layers are stacked to achieve perpendicular magnetization and control magnetic coupling, then thermal stability and spin polarization are improved, but device complexity increases and optimization becomes difficult
Solution Approach 1:
The patent extracts and eliminates the TcC magnetic coupling control layer from the structure, replacing it with a simplified CoFeB/FeCoB bilayer structure. This extraction removes the source of high device complexity while preserving the essential functions of perpendicular magnetization holding and thermal stability through the interfacial anisotropy between the free layer and cap layer.
Solution Approach 2:
The patent uses a composite material system of CoFeB and FeCoB layers that inherently provides both perpendicular magnetization and thermal stability without requiring additional magnetic coupling control layers. This composite approach achieves the desired functionality with fewer layers, reducing device complexity while maintaining reliability.
3Ease of manufacture
If conventional magnetic tunnel junction structures are used, then manufacturing is straightforward, but power consumption is high and write current is excessive
Solution Approach 1:
The patent changes the magnetic anisotropy parameter from in-plane to perpendicular by controlling the thickness and composition of the CoFeB free layer. This parameter change enables spin-transfer torque switching with lower write current while maintaining ease of manufacture using standard sputtering techniques, thus resolving the contradiction between manufacturing simplicity and power consumption.
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 solution achieves low power consumption, high-speed magnetization reversal, and enhanced reliability by increasing perpendicular magnetic anisotropy and reducing write current, allowing the magnetic tunnel junction element to operate effectively at varying temperatures.
Implementation Method 1
providing perpendicular magnetic anisotropy
Implementation Method 2
antiferromagnetic oxide layer in direct contact with the free layer... providing perpendicular magnetic anisotropy
Implementation Method 3
antiferromagnetic oxide layer in direct contact with the free layer... providing... a bias magnetic field
Implementation Method 4
providing... a bias magnetic field to enable low power, high-speed reversal
Implementation Method 5
magnetoresistive effect... read-out through the magnetoresistive effect
Implementation Method 6
insulating layer between the free layer and the fixed layer... huge tunnel magnetoresistive ratio is expected
Implementation Method 7
high spin polarization... Heusler alloy film... in contact with an insulating layer such as MgO
Data Source
AI summary
Provided is a magnetic tunnel junction element and a magnetoresistive memory device. The magnetic tunnel junction element includes a fixed layer maintaining a magnetization direction, an insulating layer, a free layer having a variable magnetization direction, and an antiferromagnetic oxide layer. The fixed layer, the free layer, and the antiferromagnetic oxide layer may be sequentially stacked. The free layer and the antiferromagnetic oxide layer may be in direct contact with each other.