MRAM Thermal Stability Enhancement Layer Design
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Solution Overview
Problem
The thermal stability of the free layer in perpendicular spin-transfer torque magnetic memory (STT-MRAM) devices decreases as the device size shrinks, limiting data retention capability, and increasing the free layer thickness compromises perpendicular anisotropy and tunneling magnetoresistance.
Innovation Solution
A thermal stability enhancement layer with perpendicular anisotropy is introduced, magnetically coupled to the free layer through a non-magnetic separation layer, maintaining out-of-plane magnetization and enhancing thermal stability without increasing the free layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the free layer thickness is increased to improve thermal stability, then thermal stability is improved, but perpendicular anisotropy and tunneling magnetoresistance are compromised
Solution Approach 1:
The patent divides the magnetic structure into separate functional layers: a reference layer, a free layer, and a thermal stability enhancement layer. This segmentation allows each layer to be optimized independently - the free layer maintains thin dimensions for high TMR and perpendicular anisotropy, while the thermal stability enhancement layer provides the necessary thermal stability through its magnetic coupling to the free layer.
Solution Approach 2:
The patent introduces a non-magnetic separation layer as an intermediary between the free layer and the thermal stability enhancement layer. This intermediary layer enables magnetic coupling while maintaining physical separation, allowing the thermal stability enhancement layer to improve thermal stability without directly compromising the perpendicular anisotropy and TMR properties of the free layer.
2Productivity
If device size is reduced to improve integration density, then productivity is improved, but thermal stability deteriorates
Solution Approach 1:
The patent addresses the thermal stability issue in miniaturized devices by adding a vertical dimension to the magnetic structure. The thermal stability enhancement layer is positioned above the free layer in the vertical dimension, connected through the non-magnetic separation layer. This vertical arrangement allows thermal stability enhancement without increasing the lateral footprint of the device, thereby maintaining high integration density while improving thermal stability.
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 improves thermal stability and maintains low critical switching currents, ensuring reliable operation and data retention in smaller device sizes by maintaining perpendicular magnetization and high tunneling magnetoresistance values.
Implementation Method 1
A thermal stability enhancement layer with perpendicular anisotropy is introduced, magnetically coupled to the free layer through a non-magnetic separation layer
Implementation Method 2
Due to the spin-polarized tunneling magnetoresistance (TMR) effect, the electrical resistance of the cell change due to the orientation of the magnetic fields of the two layers
Implementation Method 3
If a spin-polarized current is passed to the magnetic region of a free layer in the magnetic tunnel junction device, the electrons will transfer a portion of their spin-angular momentum to the magnetization layer to produce a torque on the magnetization of the free layer
Data Source
AI summary
A magnetoresistive random-access memory (MRAM) device is disclosed. The device described herein has a thermal stability enhancement layer over the free layer of a magnetic tunnel junction. The thermal stability enhancement layer improves the thermal stability of the free layer, increases the magnetic moment of the free layer, while also not causing the magnetic direction of the free layer to become in plan. The thermal stability enhancement layer can be comprised of a layer of CoFeB ferromagnetic material.