Spin Hall Effect Base Layer for ST-MRAM Switching
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Solution Overview
Problem
Conventional magnetic random access memory (MRAM) devices, particularly spin-torque MRAM (ST-MRAM), face challenges in achieving efficient and reliable data storage due to limitations in switching currents and energy efficiency, as well as reliability issues related to current-induced switching mechanisms.
Innovation Solution
The implementation of a spin Hall effect (SHE) base layer with a non-magnetic conductor material having a spin Hall angle greater than 0.05 and a thickness no greater than 5 times the spin diffusion length, allowing for lateral switching currents to align magnetic orientations within the ST-MRAM structure, while a perpendicular sensing current and voltage are applied through a magnetoresistive element stack, enhancing switching efficiency and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional spin-torque MRAM uses current-induced switching through the magnetoresistive element, then magnetic switching can be achieved, but high current requirements and energy consumption result
Solution Approach 1:
The patent introduces a spin Hall effect base layer as an intermediary component between the current path and the magnetic free layer. This base layer converts charge current into spin current through the spin Hall effect, which then acts on the free layer to induce switching. This mediator approach allows the current to flow laterally through the base layer rather than vertically through the magnetoresistive element, reducing the direct current burden while maintaining effective magnetic switching.
Solution Approach 2:
The patent replaces the conventional spin-transfer torque mechanism (which requires current to flow through the magnetic tunnel junction) with a spin Hall effect mechanism. This substitution changes the physical mechanism from direct momentum transfer through the junction to indirect spin current generation via the spin Hall effect in the base layer, thereby reducing the switching current requirement and improving energy efficiency.
2Device complexity
If reading and writing currents share the same path in conventional ST-MRAM, then device structure is simplified, but reliability decreases due to interference between read and write operations
Solution Approach 1:
The patent segments the current paths into two distinct routes: a lateral current path through the spin Hall effect base layer for writing operations, and a vertical current path through the magnetoresistive element for reading operations. This segmentation physically separates the read and write current flows, eliminating interference between operations and improving reliability, while adding only minimal structural complexity through the base layer configuration.
3Area of stationary object
If thin film dimensions are reduced to increase device density, then storage capacity increases, but switching reliability and signal detection become more difficult
Solution Approach 1:
The patent uses the spin Hall effect base layer to generate a spin current that copies the information from the charge current and transfers it to the magnetic free layer. This copying mechanism allows the magnetic switching to occur with enhanced efficiency even in reduced dimensions, as the spin current amplification effect compensates for the smaller scale, maintaining reliability while enabling higher density.
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 enables more efficient magnetic switching with lower current and energy requirements, improves device reliability by separating reading and writing current paths, and provides thermal stability for the magnetic free layer, addressing the limitations of conventional ST-MRAM technologies.
Implementation Method 1
use a base layer having an enhanced spin Hall effect (i.e., a spin Hall effect base layer (SHE base layer)) which is located and formed contacting a free layer within the ST-MRAM structure
Implementation Method 2
A central component of an MRAM device cell is a thin film magnetoresistive element, which is a combination of thin film materials whose electrical resistance depends upon the relative magnetic orientation of two or more, but generally only two, thin film ferromagnetic material layers
Data Source
AI summary
An ST-MRAM structure, a method for fabricating the ST-MRAM structure and a method for operating an ST-MRAM device that results from the ST-MRAM structure each utilize a spin Hall effect base layer that contacts a magnetic free layer and effects a magnetic moment switching within the magnetic free layer as a result of a lateral switching current within the spin Hall effect base layer. This resulting ST-MRAM device uses an independent sense current and sense voltage through a magnetoresistive stack that includes a pinned layer, a non-magnetic spacer layer and the magnetic free layer which contacts the spin Hall effect base layer. Desirable non-magnetic conductor materials for the spin Hall effect base layer include certain types of tantalum materials and tungsten materials that have a spin diffusion length no greater than about five times the thickness of the spin Hall effect base layer and a spin Hall angle at least about 0.05.