AlTiN Underlayer for MRAM Damping Reduction
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Solution Overview
Problem
In spin transfer torque MRAM using a perpendicular magnetization film, the write current is increased by the damping constant, which is undesirable, and there is a need to decrease the damping constant, increase spin polarizability, and reduce the area to achieve lower write currents.
Innovation Solution
A magnetoresistive element is designed with a recording layer and a reference layer having perpendicular magnetic anisotropy, an intermediate layer, and an underlayer made of nitrogen compounds like AlTiN, which decreases the damping constant while maintaining thermal stability, thereby reducing the write current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If Ru underlayer is used to increase thermal stability, then thermal stability is improved, but damping constant increases and write current increases
Solution Approach 1:
The patent changes the material composition of the underlayer from Ru to AlTiN, which fundamentally alters the physical parameters including damping constant and spin polarizability. This material substitution enables achieving high thermal stability through perpendicular magnetic anisotropy while simultaneously reducing damping constant to decrease write current
Solution Approach 2:
The patent employs AlTiN composite material for the underlayer, combining aluminum and titanium with nitrogen to create a material with optimized properties. This composite structure provides both high thermal stability and low damping constant, resolving the contradiction between stability and energy consumption
2Measurement precision
If CoPt stacked film is used to achieve high MR ratio, then magnetoresistive ratio is improved, but crystal magnetic anisotropy increases and write current increases
Solution Approach 1:
The patent changes the magnetic anisotropy parameter from in-plane to perpendicular orientation by using AlTiN underlayer with CoFeB recording layer. This parameter change enables achieving high MR ratio through perpendicular magnetization while reducing the write current due to lower damping constant
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
The use of AlTiN as an underlayer effectively decreases the damping constant and write current, while ensuring high thermal stability and maintaining an effective magnetoresistive ratio, thus improving the performance of the MRAM device.
Implementation Method 1
A spin transfer torque MRAM (Magnetic Random Access Memory) using a perpendicular magnetization film
Implementation Method 2
The use of AlTiN as an underlayer effectively decreases the damping constant and write current
Implementation Method 3
a magnetoresistive element includes a recording layer and a reference layer, each having perpendicular magnetic anisotropy
Data Source
AI summary
According to one embodiment, a magnetoresistive element includes a recording layer having magnetic anisotropy perpendicular to a film surface and having a variable magnetization direction, a reference layer having magnetic anisotropy perpendicular to a film surface and having an invariable magnetization direction, an intermediate layer provided between the recording layer and the reference layer, and a underlayer containing AlTiN and provided on an opposite side of a surface of the recording layer on which the intermediate layer is provided.