STTMRAM Element with Perpendicular Enhancement Layer for Low Switching Current
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Solution Overview
Problem
Current spin transfer torque magnetic random access memory (STTMRAM) technologies face challenges in reducing the switching current density while maintaining high thermal stability and tunneling magneto-resistive ratio (TMR) performance, particularly due to high damping constants associated with conventional perpendicular anisotropy materials like FePt, which also complicate the manufacturing process.
Innovation Solution
The development of a spin transfer torque magnetic random access memory (STTMRAM) element with a first perpendicular free layer and a second perpendicular reference layer, each incorporating a perpendicular enhancement layer, formed using a method that reduces damping and increases magnetic stiffness, allowing for lower switching current density and higher TMR performance, achievable through a simplified film manufacturing process at room substrate temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional perpendicular anisotropy materials like FePt are used, then thermal stability is improved, but damping constant increases leading to higher switching current density
Solution Approach 1:
The patent changes the material composition parameters by replacing conventional FePt perpendicular anisotropy materials with CoFeB-based materials having different magnetic properties (lower saturation magnetization and lower damping constant), thereby reducing switching current density while maintaining thermal stability through engineered magnetic anisotropy
Solution Approach 2:
The patent employs composite material structures including CoFeB alloy layers combined with specific thickness ratios (e.g., 3:1 or 4:1 thickness ratios between different layers) to achieve optimized magnetic properties that balance thermal stability with low switching current density requirements
2Stability of the object's composition
If conventional perpendicular anisotropy materials are used, then thermal stability is improved, but manufacturing process complexity increases
Solution Approach 1:
The patent changes manufacturing parameters by enabling deposition at room temperature instead of requiring elevated temperatures, and uses standard sputtering techniques rather than complex high-ordering transformation processes, thereby simplifying manufacturing while maintaining thermal stability through material composition engineering
3Length of moving object
If switching current density is reduced, then access transistor size can be reduced, but thermal stability may be compromised
Solution Approach 1:
The patent changes the magnetic material parameters (saturation magnetization, damping constant, and magnetic anisotropy) by using CoFeB-based materials with optimized thickness ratios, enabling reduced switching current density for smaller transistors while maintaining sufficient thermal stability for data retention
Solution Approach 2:
The patent uses composite CoFeB alloy structures with specific layer thickness ratios (3:1 or 4:1) to achieve the optimal balance between low switching current density and high thermal stability, allowing miniaturization of access transistors without compromising data retention reliability
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 results in a STTMRAM element with reduced switching current density and enhanced thermal stability, improving scalability and manufacturing ease while maintaining high TMR performance, addressing the limitations of conventional technologies.
Implementation Method 1
The PEL is made of any combination of materials including Ta, Ti, Hf, Nb, V, Y, Re, W, Cr, Mo, and Ru, and having a thickness of 1 to 10 Angstroms. In some embodiments, the CoFeB layer and the PEL are deposited in-situ without breaking vacuum.
Implementation Method 2
One of the challenges for implementing STT is a substantial reduction of the intrinsic current density to switch the magnetization of the free layer while maintaining high thermal stability
Implementation Method 3
MTJ exhibits a low (high) resistance state when the magnetization orientation of the two ferromagnetic layers in substantially parallel (anti-parallel) direction
Data Source
AI summary
A spin-transfer torque magnetic random access memory (STTMRAM) element employed to store a state based on the magnetic orientation of a free layer, the STTMRAM element is made of a first perpendicular free layer (PFL) including a first perpendicular enhancement layer (PEL). The first PFL is formed on top of a seed layer. The STTMRAM element further includes a barrier layer formed on top of the first PFL and a second perpendicular reference layer (PRL) that has a second PEL. The second PRL is formed on top of the barrier layer. The STTMRAM element further includes a capping layer that is formed on top of the second PRL.