Graded Synthetic Free Layer STTMRAM Thermal Stability
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Solution Overview
Problem
Spin transfer torque magnetic random access memory (STTMRAM) elements face challenges with low thermal stability, affecting the reliable switching of magnetic orientation, which is crucial for data storage.
Innovation Solution
The implementation of a graded synthetic free layer in STTMRAM elements, comprising multiple magnetic layers with anti-parallel orientations, balances the net magnetic field, reducing the demagnetizing field and thereby requiring lower switching currents while maintaining thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional magnetic layer configuration is used in STTMRAM, then the device structure is simple, but thermal stability is low which adversely affects switching behavior
Solution Approach 1:
The free layer is divided into multiple magnetic sublayers (first magnetic layer, second magnetic layer, third magnetic layer) with different magnetization directions. This segmentation allows each sublayer to contribute differently to the overall magnetic field, enabling improved thermal stability through balanced net magnetic field while maintaining manageable structural complexity
Solution Approach 2:
Different regions of the free layer are assigned different magnetic properties: the first magnetic layer has in-plane magnetization, while the second and third magnetic layers have perpendicular magnetization. This local quality differentiation enables precise control over the net magnetic field distribution, achieving optimal thermal stability without requiring complete structural redesign
2Reliability
If higher thermal stability is achieved through conventional means, then data storage reliability improves, but switching current requirement increases
Solution Approach 1:
The second and third magnetic layers with perpendicular magnetization are configured to counterbalance the demagnetizing field generated by the first magnetic layer. This anti-weight effect reduces the net demagnetizing field, thereby lowering the switching current requirement while maintaining the thermal stability needed for reliable data storage
Solution Approach 2:
The invention changes the magnetization direction parameter from uniform in-plane to a combination of in-plane and perpendicular magnetization across different layers. This parameter change optimizes the balance between thermal stability and switching current, achieving both high reliability and low energy consumption
3Speed
If the net magnetic field is increased to improve switching behavior, then switching speed improves, but thermal stability decreases
Solution Approach 1:
Different magnetic layers are assigned different magnetization strengths and directions to create localized magnetic field distributions. The first layer provides in-plane magnetization for controlled switching, while the second and third layers provide perpendicular magnetization to balance the net field, achieving both fast switching and high thermal stability
Solution Approach 2:
The free layer is constructed as a composite of multiple magnetic materials with different magnetization characteristics. This composite structure enables the system to exhibit both fast switching behavior (from the in-plane magnetized layer) and high thermal stability (from the perpendicular magnetized layers that balance the net field)
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 enhances thermal stability and reduces the switching current, improving the reliability and density of memory elements without compromising memory integrity, making STTMRAM a more viable candidate for replacing SRAM.
Implementation Method 1
writing magnetic bits is achieved by using a spin polarized current through the magnetic tunnel junction (MTJ), instead of using a magnetic field
Implementation Method 2
comprising multiple magnetic layers with anti-parallel orientations, balances the net magnetic field, reducing the demagnetizing field
Implementation Method 3
magnetic tunnel junction (MTJ)
Data Source
AI summary
A spin transfer torque memory random access memory (STTMRAM) element is capable of switching states when electrical current is applied thereto for storing data and includes the following layers. An anti-ferromagnetic layer, a fixed layer formed on top of the anti-ferromagnetic layer, a barrier layer formed on top of the second magnetic layer of the fixed layer, and a free layer including a first magnetic layer formed on top of the barrier layer, a second magnetic layer formed on top of the first magnetic layer, a nonmagnetic insulating layer formed on top of the second magnetic layer and a third magnetic layer formed on top of the non-magnetic insulating layer. A capping layer is formed on top of the non-magnetic insulating layer.