Perpendicular Magnetic Tunnel Junction with Crystalline Free Layer
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Solution Overview
Problem
Conventional packaging processing for Magnetic Random Access Memory (MRAM) chips requires high temperatures, which degrades the stability of magnetic tunnel junctions (MTJs) and affects information storage reliability.
Innovation Solution
A method is developed to form a perpendicular magnetic tunnel junction (pMTJ) stack with an as-deposited crystalline magnetic free layer, reducing temperature sensitivity and enhancing stability, by engineering the interface between the tunneling barrier layer and the free layer using molecules with a small radius to enhance perpendicular magnetic anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional packaging processing is used to form MRAM chips, then the packaging can be completed, but the high temperature degrades the stability of MTJs and affects information storage reliability
Solution Approach 1:
The patent changes the material composition and crystalline structure parameters of the free layer to create a magnetic layer that maintains stable magnetization at high temperatures. By adjusting the alloy composition and inducing a crystalline structure with perpendicular magnetic anisotropy, the free layer's thermal stability is improved to withstand packaging processing temperatures up to 260°C
Solution Approach 2:
The patent employs a composite structure consisting of multiple thin layers including the free layer, barrier layer, and cap layer. Each layer is composed of specific materials (e.g., CoFeB, MgO, Ta) with engineered interfaces that collectively provide thermal stability and perpendicular magnetic anisotropy, allowing the MTJ to withstand high-temperature packaging processing
2Ease of manufacture
If the free layer is made amorphous, then the manufacturing process is simpler, but the energy barrier is low and temperature sensitivity is high
Solution Approach 1:
The patent changes the structural parameter of the free layer from amorphous to crystalline state while maintaining compatibility with standard sputtering deposition processes. This crystalline transformation, achieved through controlled deposition conditions and material composition, increases the perpendicular magnetic anisotropy and energy barrier without requiring additional complex manufacturing steps
Solution Approach 2:
The patent applies local quality by creating a crystalline structure specifically in the free layer region while maintaining the overall layer structure. The crystalline phase is induced locally at the free layer through material composition control and deposition parameter optimization, providing enhanced thermal stability at the critical interface region without affecting other parts of the device
3Reliability
If the free layer is made crystalline, then the energy barrier is high and temperature sensitivity is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent optimizes material composition parameters (e.g., Co:Fe:B ratios, layer thicknesses) and deposition parameters (e.g., sputtering power, gas flow rates, substrate temperature) to achieve crystalline structure formation during standard deposition processes. By carefully controlling these parameters, the crystalline phase is obtained without requiring additional annealing or complex post-processing steps
Solution Approach 2:
The patent enables the free layer to self-organize into a crystalline structure with perpendicular magnetic anisotropy through controlled deposition conditions. The material composition and deposition parameters are designed such that the crystalline structure forms in-situ during the sputtering process itself, eliminating the need for separate crystallization treatments and reducing overall manufacturing complexity
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 approach results in a pMTJ stack that maintains stability at high temperatures, such as 260°C, during reflow processing, improving information storage reliability and reducing power consumption without increasing chip size.
Implementation Method 1
engineering the interface between the tunneling barrier layer and the free layer using molecules with a small radius to enhance perpendicular magnetic anisotropy
Data Source
AI summary
A magnetic tunneling junction (MTJ) with a free layer that is less temperature sensitive and is reflow compatible at 260° C. The magnetic free layer may include various configurations, such as a single as-deposited crystalline magnetic layer or a composite free layer with more than one magnetic layers or a combination of composite and single magnetic layers. The layers of the composite magnetic free layer may include as-deposited crystalline magnetic free layers or a combination of as-deposited crystalline and as-deposited amorphous magnetic layers, with or without a spacer layer. An interface layer may be provided at an interface between the free layer and adjacent layer to apply tensile stress on the free layer in the direction perpendicular to the in-plane direction to enhance perpendicular magnetic anisotropy (PMA) of the free layer.