Spin-Injection MRAM With Magnetic Shielding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Miniaturization of Magnetic Random Access Memory (MRAM) devices faces challenges in achieving a balance between reducing write current and maintaining magnetization stability due to increased coercive field, making it difficult to fabricate large-capacity memory devices using the magnetic field write method.
Innovation Solution
The semiconductor memory device employs a spin-injection write method with a stacked structure of MTJ elements, including a perpendicular magnetic film, a tunnel junction layer, and an insulating film with dispersed metallic or magnetic powders acting as a magnetic shield to reduce magnetic interference and maintain insulating properties, allowing for efficient magnetization inversion and stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the magnetic field write method is used with miniaturized MTJ elements, then the memory density is improved, but the write current cannot be sufficiently decreased due to increased coercive field
Solution Approach 1:
The patent replaces the magnetic field write method with a spin injection write method. Instead of using external magnetic fields generated by write lines to invert magnetization, the invention directly injects spin-polarized electrons through the tunnel junction into the storage layer, utilizing spin-transfer torque to invert magnetization. This substitution eliminates the need for high current densities in write lines and directly addresses the coercive field issue in miniaturized elements.
Solution Approach 2:
The patent introduces a spin-polarization layer as an intermediary component. This layer, positioned adjacent to the storage layer and separated by a nonmagnetic layer, serves as a mediator that generates spin-polarized electrons when current passes through it. These spin-polarized electrons then act as the actual mechanism for inverting storage layer magnetization, decoupling the write current path from the storage layer and enabling efficient magnetization inversion in miniaturized elements.
2Use of energy by moving object
If the write line is brought closer to the storage layer to decrease write current, then the write current is reduced, but the magnetic field interference and crosstalk increase
Solution Approach 1:
The patent eliminates the magnetic field generation mechanism by write lines and replaces it with direct spin electron injection. Since the spin injection method does not rely on external magnetic fields, the harmful magnetic field interference and crosstalk are inherently avoided, regardless of the spatial arrangement between write structures and storage elements.
Solution Approach 2:
The patent extracts and removes the magnetic field generation function from the write line structure. By using a separate spin-polarization layer to generate spin-polarized electrons, the invention separates the magnetization inversion mechanism from any potential magnetic field sources, thereby eliminating magnetic field interference as a harmful factor.
3Volume of moving object
If the MTJ element is miniaturized to increase memory density, then the memory capacity is improved, but the coercive field increases making write operation difficult
Solution Approach 1:
The patent replaces the magnetic field-based write mechanism with direct spin electron injection. This substitution enables effective magnetization inversion in miniaturized elements because spin-transfer torque is highly efficient at small scales, directly acting on the magnetic moments of the storage layer atoms without being hindered by increased coercive field effects that plague magnetic field methods.
Solution Approach 2:
The spin-polarization layer acts as a mediator that provides a controlled source of spin-polarized electrons specifically tailored for the storage layer. This intermediary structure enables precise control over the spin injection process, ensuring reliable magnetization inversion even in miniaturized elements with high coercive fields, thereby maintaining magnetization stability while enabling small-scale operation.
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 decreases the write current required for data inversion while preventing magnetic crosstalk and maintaining the high Tunneling Magneto-Resistance effect, enabling stable and efficient operation of MRAM devices.
Implementation Method 1
When a current is passed through the MTJ element including storage layer/tunnel junction layer/reference layer, a resistance value of the MTJ element is changed according to the magnetization direction of the storage layer relative to the magnetization direction of the reference layer. Specifically, the resistance value takes a minimum value when the magnetization directions of the storage layer and the reference layer are parallel to each other, and the resistance value takes a maximum value when the magnetization directions are antiparallel. The phenomenon is called a Tunneling Magneto-Resistance effect
Implementation Method 2
recently a spin injection write method in which the magnetization is inverted by utilizing a spin-polarization current is being investigated. In the spin injection write method, the spin-polarization current is passed through the MTJ element to invert the magnetization direction of the storage layer
Implementation Method 3
a current is passed through a wiring disposed near the storage layer of the MTJ element, and the magnetization direction of the storage layer is inverted by utilizing a magnetic field generated around the storage layer (magnetic field write method)
Data Source
AI summary
According to one embodiment, a semiconductor memory device includes plural magneto-resistance elements being two-dimensionally arrayed on a semiconductor substrate. In the semiconductor memory device, each of the magneto-resistance elements includes: a first magnetic layer formed on the semiconductor substrate; a non-magnetic layer formed on the first magnetic layer; and a second magnetic layer formed on the non-magnetic layer, and an insulating film buried between the magneto-resistance elements adjacent to each other, a powder made of a metallic material or a magnetic material being dispersed in the insulating film.