MeRAM Write Error Rate Reduction via Reverse Pulse Stabilization
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Solution Overview
Problem
Magnetoelectric random access memory (MeRAM) technologies face challenges in reducing write error rates due to high switching current density and power consumption, especially as bit sizes shrink below 100 nm, and existing writing schemes are inefficient in stabilizing the magnetic state post-write operation.
Innovation Solution
The implementation of a reverse pulse scheme that applies a voltage of a given polarity across a magnetoelectric junction bit for a precessional period, followed by a voltage of opposite polarity to increase perpendicular magnetic anisotropy and stabilize the magnetization direction, reducing write error rates by enhancing the falling slope of the write voltage and securing the written state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage pulse is applied to switch magnetization direction in MeRAM, then the magnetization state changes, but write error rate increases due to insufficient stabilization of the magnetic state post-write
Solution Approach 1:
A reverse voltage pulse is applied immediately after the write pulse to preemptively stabilize the magnetization state before thermal fluctuations or other disturbances can cause errors. This preliminary stabilization action prevents write errors rather than correcting them later, reducing the need for multiple write attempts.
Solution Approach 2:
The writing scheme uses periodic voltage pulses (write pulse followed by reverse pulse) to control magnetization switching. This periodic action allows precise timing control of the magnetization reversal process, ensuring the state is stabilized at the optimal moment to minimize write errors.
2Reliability
If the write voltage pulse duration is extended to ensure complete magnetization switching, then switching reliability improves, but energy consumption increases
Solution Approach 1:
Instead of using a single long voltage pulse, the invention employs a periodic sequence of pulses: a primary write pulse for magnetization switching followed by a shorter reverse pulse for stabilization. This periodic approach achieves complete switching with shorter individual pulse durations, reducing overall energy consumption while maintaining reliability.
Solution Approach 2:
The invention changes the voltage parameter dynamically by applying a reverse voltage pulse after the write pulse. This parameter change (from forward voltage to reverse voltage) allows the system to achieve stable magnetization switching with optimized pulse durations, reducing the energy required compared to using a single extended pulse.
3Speed
If the write voltage pulse amplitude is increased to accelerate magnetization switching, then switching speed improves, but magnetic state stability post-write deteriorates
Solution Approach 1:
The reverse voltage pulse acts as a counterweight to the strong write pulse. After the high-amplitude write pulse switches the magnetization rapidly, the reverse pulse counteracts any excessive magnetization dynamics or oscillations, stabilizing the final magnetic state and preventing write errors caused by unstable switching.
Solution Approach 2:
The reverse voltage pulse is applied immediately after the write pulse to preemptively stabilize the magnetization state before thermal fluctuations or other disturbances can cause errors. This preliminary stabilization action prevents write errors rather than correcting them later, reducing the need for multiple write attempts.
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 reduces the number of write attempts required to achieve a given bit error rate, lowers write error rates, and improves the energy efficiency of MeRAM by stabilizing the magnetic state and minimizing undesired switching.
Implementation Method 1
application of the voltage of the given polarity across the magnetoelectric junction bit reduces the perpendicular magnetic anisotropy and magnetic coercivity of the ferromagnetic free layer through a voltage controlled magnetic anisotropy effect
Implementation Method 2
lowering the applied voltage of the given polarity before the end of the given period of time, wherein the given period of time is approximately half of a precessional period of the ferromagnetic free layer
Data Source
AI summary
Systems and methods for reducing write error rate in MeRAM applications in accordance with various embodiments of the invention are illustrated. One embodiment includes a method for a writing mechanism for a magnetoelectric random access memory cell, the method including applying a voltage of a given polarity for a given period of time across a magnetoelectric junction bit of the magnetoelectric random access memory cell, wherein application of the voltage of the given polarity across the magnetoelectric junction bit reduces the perpendicular magnetic anisotropy and magnetic coercivity of the ferromagnetic free layer through a voltage controlled magnetic anisotropy effect, and lowering the applied voltage of the given polarity before the end of the given period of time, wherein the given period of time is approximately half of a precessional period of the ferromagnetic free layer.