MRAM Free-Layer Stack With High-Exchange Spacer for Fast Retention
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Solution Overview
Problem
Current memory technologies face challenges in achieving a balance between high-speed operation, non-volatility, and low power consumption, with existing memory solutions like DRAM requiring frequent refreshing and having limited data retention times.
Innovation Solution
The development of magnetoresistive random-access memory (MRAM) devices with spin Hall electrodes and magnetic tunnel junctions (MTJs) that utilize spin transfer torque or spin-orbit torque mechanisms, allowing for efficient data storage and retrieval with long retention times and low power consumption, by patterning the spin Hall electrode to create varying thickness regions for enhanced current flow and resistance differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If DRAM is used for high-speed operation, then speed is improved, but data retention time deteriorates due to frequent refreshing requirements
Solution Approach 1:
The patent changes the fundamental operating parameter from volatile electrical charge storage (DRAM) to non-volatile magnetic state storage (MRAM). By utilizing magnetic tunnel junctions with different resistance states corresponding to magnetic orientations, the system achieves both high-speed operation through electrical read/write access and long data retention times without refreshing, as the magnetic states are inherently non-volatile.
2Use of energy by stationary object
If MRAM with spin Hall electrode is used, then power consumption is reduced and data retention is improved, but device complexity increases due to additional magnetic layers and spin Hall electrode structure
Solution Approach 1:
The patent merges the write current path through the spin Hall electrode with the magnetic tunnel junction structure. The spin Hall electrode serves dual purposes: it generates spin-orbit torque for magnetic switching and provides the read current path. This integration reduces the need for separate write and read structures, thereby managing complexity while achieving low power consumption through efficient spin transfer torque mechanisms.
Solution Approach 2:
The patent replaces traditional magnetic field-based write mechanisms (which require external coils and high currents) with spin-orbit torque generated by spin Hall effect in the electrode. This substitution eliminates the need for external magnetic field generation structures, reducing device complexity while achieving efficient magnetic switching with lower power consumption.
3Productivity
If spin Hall electrode with varying thickness is patterned, then current flow efficiency is improved and resistance differences are enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent implements local quality variation in the spin Hall electrode by creating regions of different thicknesses. The central region has greater thickness to provide higher spin Hall angle and stronger spin-orbit torque for reliable magnetic switching, while peripheral regions have reduced thickness to lower resistance for efficient current flow. This spatially varying thickness profile optimizes both switching efficiency and current flow characteristics.
Solution Approach 2:
The patent addresses manufacturing precision challenges by transitioning from controlling thickness in one dimension to utilizing the vertical dimension for functional differentiation. The varying thickness is achieved through selective etching or deposition processes that create a depth profile, transforming a single-parameter control problem into a multi-dimensional structural solution that enhances both current efficiency and switching performance.
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
MRAM devices offer fast read and write speeds, long data retention times, and reduced power consumption, making them suitable for next-generation memory technologies that combine the benefits of SRAM and DRAM while overcoming their limitations.
Implementation Method 1
MRAM devices with spin Hall electrodes and magnetic tunnel junctions (MTJs) that utilize spin transfer torque or spin-orbit torque mechanisms
Implementation Method 2
utilize spin transfer torque or spin-orbit torque mechanisms
Implementation Method 3
utilize spin transfer torque or spin-orbit torque mechanisms
Implementation Method 4
patterning the spin Hall electrode to create varying thickness regions for enhanced current flow and resistance differences
Data Source
AI summary
A memory device includes a substrate, a reference layer, a tunneling layer, a film stack, and a capping layer. The reference layer is disposed on the substrate. The tunneling layer is disposed on the reference layer. The film stack is formed over the tunneling layer and on the substrate, wherein the film stack includes a first free layer, a spacer with high exchange stiffness constant and a second free layer. The first free layer is in contact with the tunneling layer and the film stack. The spacer with high exchange stiffness constant is sandwiched between the first free layer and the second free layer. The capping layer is disposed on and electrically connected to the film stack.