MRAM Memory Element With Ta Cap Layer for Low Write Current
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Solution Overview
Problem
Magnetic random access memory (MRAM) devices face challenges in miniaturization due to the difficulty in flowing sufficient current for magnetization inversion, leading to instability in retaining information, especially with the use of spin injection, where thermal stability is compromised and write current is high, making it hard to achieve reliable data retention and low power consumption.
Innovation Solution
A memory element with a layered structure including a memory layer, a magnetization-fixed layer, and an insulating layer, where spin-polarized electrons are injected in the lamination direction, and a cap layer with a Ta film is used to reduce the effective diamagnetic field, allowing for magnetization inversion with a smaller write current and improved thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If spin injection is used for magnetization inversion in miniaturized memory elements, then the device can be miniaturized, but thermal stability deteriorates and write current increases
Solution Approach 1:
The patent changes the magnetization inversion mechanism from spin injection to direct current flow through address interconnects. This parameter change in the inversion mechanism allows miniaturized memory elements to maintain sufficient thermal stability while reducing write current requirements, resolving the contradiction between miniaturization and thermal stability
Solution Approach 2:
The patent substitutes the spin injection mechanism with a direct current magnetic field generation approach. By replacing the spin-dependent mechanism with a direct electromagnetic field approach through address interconnects, the system achieves reliable magnetization inversion in miniaturized devices without compromising thermal stability
2Ease of operation
If spin injection is used for magnetization inversion, then magnetization can be inverted, but write current becomes high
Solution Approach 1:
The patent replaces the spin injection mechanism with direct current flow through address interconnects to generate magnetic fields for magnetization inversion. This substitution eliminates the need for high current densities required for spin injection, thereby reducing write current while maintaining inversion capability
Solution Approach 2:
The address interconnects serve dual functions: they provide the current path for selecting memory cells and simultaneously generate the magnetic field for magnetization inversion. This multi-functionality reduces the need for separate high-current write paths, lowering overall write current requirements
3Productivity
If address interconnect is miniaturized, then device density increases, but current flow capability decreases
Solution Approach 1:
The address interconnects are designed to serve both as selection lines and as magnetic field generation lines. By making the address interconnects carry both selection and inversion functions, the patent eliminates the need for separate thick write lines, maintaining high device density while ensuring sufficient current flow capability for magnetization inversion
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 configuration enables efficient magnetization inversion with reduced write current, enhanced thermal stability, and lower power consumption, allowing for reliable data retention and high-density memory devices.
Implementation Method 1
a magnitude of an effective diamagnetic field which the memory layer receives is smaller than a saturated magnetization amount of the memory layer
Implementation Method 2
Magnetization inversion by the spin injection means that a spin polarized electron after passing through a magnetic material is injected into the other magnetic material, and thereby magnetization inversion is caused in the other magnetic material
Implementation Method 3
an insulating layer that is provided between the memory layer and the magnetization-fixed layer and is formed of a non-magnetic material
Data Source
AI summary
There is disclosed a memory element which includes a layered structure. The layered structure includes a memory layer that has a magnetization perpendicular to a film face; a magnetization-fixed layer having magnetization perpendicular to the film face; an insulating layer provided between the memory layer and the magnetization-fixed layer; and a cap layer provided at a face side, which is opposite to the insulating layer-side face, of the memory layer, in which an electron that is spin-polarized is injected in a lamination direction of the layered structure, and thereby the magnetization direction of the memory layer varies and a recording of information is performed, a magnitude of an effective diamagnetic field which the memory layer receives is smaller than a saturated magnetization amount of the memory layer, and at least a face, which comes into contact with the memory layer, of the cap layer is formed of a Ta film.