MTJ Free-Layer Segmentation for Fast Switching and Data Retention
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Solution Overview
Problem
Existing magnetic tunneling junction devices face a trade-off between operating speed and data retention, with reducing saturation magnetization leading to decreased tunneling magnetoresistance and retention.
Innovation Solution
Incorporating a free layer structure with a non-magnetic metal-doped second free layer and a boron-controlled first free layer, along with oxide layers to manage saturation magnetization and tunneling magnetoresistance, allowing for high-speed operation without significant retention loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If saturation magnetization is reduced to achieve faster operating speed, then operating speed is improved, but tunneling magnetoresistance and data retention deteriorate
Solution Approach 1:
The free layer is divided into two distinct sub-layers: a first free layer with high saturation magnetization for maintaining TMR and retention, and a second free layer with low saturation magnetization for enabling fast switching. This segmentation allows each sub-layer to fulfill different functional requirements simultaneously, resolving the contradiction between speed and reliability.
Solution Approach 2:
Different regions of the free layer are assigned different magnetic properties through the two-sublayer structure. The first free layer near the pinned layer has high Ms for strong TMR, while the second free layer has low Ms for fast switching. This local differentiation of properties enables both high retention and high speed operation within the same device.
2Speed
If non-magnetic element is doped to reduce saturation magnetization, then operating speed is improved, but tunneling magnetoresistance deteriorates
Solution Approach 1:
Non-magnetic element doping is applied locally only to the second free layer, leaving the first free layer with high boron content and high saturation magnetization intact. This localized doping strategy enables fast switching in the second layer while preserving strong TMR in the first layer, avoiding the trade-off that would occur with uniform doping.
Solution Approach 2:
The free layer is segmented into two parts with different compositions: the first free layer maintains high boron content for high Ms and TMR, while the second free layer has reduced boron content or alternative doping for low Ms and fast switching. This compositional segmentation resolves the contradiction between TMR and switching speed.
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 fast operating speeds of less than 10 nsec while maintaining data retention, improving switching efficiency and minimizing degradation of tunneling magnetoresistance and data retention.
Implementation Method 1
Spin Transfer Torque-Magnetic RAM (STT-MRAM) that is currently mass-produced
Implementation Method 2
The resistance of the magnetic tunneling junction device varies with the magnetization direction of a free layer
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Provided are a magnetic tunneling junction device having a fast operating speed without reducing or with increasing data retention and/or a memory device including the magnetic tunneling junction device. The magnetic tunneling junction device includes a free layer having a first surface and a second surface opposite the first surface; a pinned layer facing the first surface of the free layer; a first oxide layer between the pinned layer and the free layer; and a second oxide layer on the second surface of the free layer. The free layer includes a first free layer adjacent to the first oxide layer and a second free layer adjacent to the second oxide layer. The first free layer includes a magnetic material not doped with a non-magnetic metal, and the second free layer includes a magnetic material doped with the non-magnetic metal.