Fe-Co-B Free Layer Composition for Thermally Stable MTJ Recording
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Solution Overview
Problem
The existing MRAM elements face challenges with insufficient thermal stability and complex manufacturing processes due to the use of composite layers with multi-layered structures for the ferromagnetic free layer, which complicates film formation and etching, increases costs, and limits mass productivity.
Innovation Solution
A ferromagnetic free layer composed of Fe, Co, B, and an additive metal (Mo or Re) with specific atomic content ratios and thickness, allowing it to maintain magnetic properties during high-temperature thermal treatments, thus ensuring the normal recording function of the MTJ structure without a multi-layered structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a composite layer with multi-layered structure is used for the ferromagnetic free layer, then thermal stability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges multiple functional layers (ferromagnetic layer, non-magnetic layer, and capping layer) into a single integrated ferromagnetic free layer with controlled composition gradients. This combining approach maintains the thermal stability benefits of multi-layer structures while eliminating the complexity of fabricating and aligning multiple separate layers, directly resolving the contradiction between reliability and device complexity.
Solution Approach 2:
The patent employs composite material design by creating a ferromagnetic free layer with non-uniform composition containing Fe, Co, B, and additive metals (Mo, Re, or Ru) in specific concentration ranges. This composite material approach achieves the thermal stability of multi-layer structures through compositional engineering rather than structural layering, reducing manufacturing complexity while maintaining reliability.
2Reliability
If a composite layer with multi-layered structure is used for the ferromagnetic free layer, then thermal stability is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent combines multiple deposition processes into a single continuous deposition process for forming the ferromagnetic free layer. By integrating the ferromagnetic, non-magnetic, and capping layers into one monolithic structure deposited in sequence without intermediate handling, the patent maintains thermal stability while dramatically improving ease of manufacture and reducing process complexity.
Solution Approach 2:
The patent uses parameter control (composition ratios of Fe, Co, B, and additive metals within specific ranges) to achieve thermal stability without changing the fundamental single-layer structure. This parameter-based optimization allows standard deposition equipment and processes to be used, improving ease of manufacture compared to multi-layer structures that require precise thickness control and alignment.
3Reliability
If a composite layer with multi-layered structure is used for the ferromagnetic free layer, then thermal stability is improved, but productivity decreases
Solution Approach 1:
The patent merges multiple fabrication steps into a single deposition process, eliminating intermediate handling, alignment, and inspection steps required for multi-layer structures. This integration significantly improves mass productivity while maintaining thermal stability, as the single-layer structure can be deposited continuously across large substrate areas without the compounding complexity of multiple layer operations.
4Reliability
If a composite layer with multi-layered structure is used for the ferromagnetic free layer, then thermal stability is improved, but manufacturing cost increases
Solution Approach 1:
The patent combines multiple layers into a single ferromagnetic free layer structure, reducing the number of deposition chambers, processing steps, and quality control checkpoints required. This merging approach maintains thermal stability while lowering manufacturing costs by simplifying the overall fabrication workflow and reducing equipment utilization requirements.
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 proposed ferromagnetic free layer provides improved thermal stability and simplifies the manufacturing process, maintaining magnetic properties after high-temperature treatments, enhancing mass productivity and reducing process complexity and costs.
Implementation Method 1
the ferromagnetic free layer provides improved thermal stability and simplifies the manufacturing process, maintaining magnetic properties after high-temperature treatments
Implementation Method 2
The advent of MRAM elements comes from the advance of giant magnetoresistance (GMR) and spin-transfer torque (STT) effects
Implementation Method 3
The advent of MRAM elements comes from the advance of giant magnetoresistance (GMR) and spin-transfer torque (STT) effects
Implementation Method 4
STT is accomplished by the MTJ involving the tunneling magnetoresistance (TMR) effect
Data Source
AI summary
Provided is a ferromagnetic free layer, comprising Fe, Co, B and an additive metal, and based on a total atomic number of the ferromagnetic free layer, a content of Co is more than 0 at % and less than 30 at %, a content of B is more than 10 at % and less than or equal to 35 at %, and a content of the additive metal is more than or equal to 2 at % and less than 10 at %; the additive metal comprises Mo, Re or a combination thereof, and a thickness of the ferromagnetic free layer is more than or equal to 1.5 nm and less than 2.5 nm. The ferromagnetic free layer can be applied to a MTJ structure as a single layer, and has sufficient thermal stability for maintaining good magnetic properties after thermal treatment, which makes sure that the MTJ structure can exert normal recording function.