MTJ Memory Readout With Asymmetric Magnetoresistance Amplification
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Solution Overview
Problem
Magnetoresistive memory devices face challenges due to small readout signals caused by low tunneling magnetoresistance (TMR) ratios, which decrease with increasing sensing bias voltage, leading to insufficient improvement in read signals even in devices with high zero-bias TMR, and self-referenced read modes are slower than desired.
Innovation Solution
Incorporating an asymmetric magnetoresistance layer between the magnetic tunnel junction layer stack and electrodes, which exhibits higher resistance in the antiparallel state and lower resistance in the parallel state, thereby amplifying the readout signal and increasing the signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensing bias voltage is increased to improve readout signal, then read signal strength improves, but TMR ratio decreases strongly
Solution Approach 1:
The patent divides the magnetoresistive memory device into two functional segments: a magnetic tunnel junction (MTJ) for data storage and an asymmetric magnetoresistance layer for signal amplification. This segmentation allows the MTJ to maintain its TMR ratio while the asymmetric layer compensates for signal weakness at high bias voltages, resolving the contradiction between readout signal strength and TMR ratio maintenance.
Solution Approach 2:
The asymmetric magnetoresistance layer acts as an intermediary between the MTJ and the readout circuitry. It receives the weak signal from the MTJ at high bias voltages and amplifies it through its asymmetric magnetoresistance effect, thereby improving readout signal strength without requiring the MTJ itself to have an elevated TMR ratio.
2Measurement precision
If self-referenced read mode is used to overcome small TMR at readout voltage, then TMR measurement accuracy improves, but read speed decreases
Solution Approach 1:
The asymmetric magnetoresistance layer provides self-service by automatically amplifying the readout signal through its inherent asymmetric magnetoresistance effect. This eliminates the need for complex self-referenced read modes that require additional reference cells and slower differential measurement procedures, thereby maintaining fast read speeds while achieving accurate TMR measurement.
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 asymmetric magnetoresistance layer enhances the readout signal and improves the signal-to-noise ratio, providing better data retention and high-fidelity read operations without disturbing the magnetic state, thus overcoming the limitations of small TMR ratios and slow read modes.
Implementation Method 1
an asymmetric magnetoresistance layer located between the magnetic tunnel junction layer stack and one of the first electrode and the second electrode
Implementation Method 2
a small readout signal due to a small tunneling magnetoresistance (TMR) ratio
Data Source
AI summary
A magnetoresistive memory cell includes a first electrode, a second electrode that is spaced from the first electrode, a magnetic tunnel junction layer stack located between the first electrode and the second electrode, the magnetic tunnel junction layer stack containing, from one side to another, a reference layer having a fixed reference magnetization direction, a tunnel barrier layer comprising a dielectric material, and a free layer, and an asymmetric magnetoresistance layer located between the magnetic tunnel junction layer stack and one of the first electrode and the second electrode.