MeRAM Reverse Pulse Write Error Rate Reduction

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Solution Overview

Problem

Magnetoelectric random access memory (MeRAM) technologies face challenges in reducing write error rates due to high power consumption and the need for large switching currents, especially as bit sizes shrink below 100 nm, and existing writing schemes are inefficient in stabilizing the magnetic state post-write operation.

Innovation Solution

A reverse pulse (RVP) scheme is implemented in MeRAM, which involves applying a voltage of a given polarity across a magnetoelectric junction bit to reduce perpendicular magnetic anisotropy and coercivity, followed by a voltage of opposite polarity to increase anisotropy and stabilize the magnetization direction, using a voltage-controlled magnetic anisotropy effect to secure the written state and reduce write error rates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a voltage pulse is applied to switch magnetization direction in MeRAM, then the magnetization state changes, but the write error rate increases due to insufficient stabilization of the magnetic state

Engineering Contradiction:

Improvewrite error rateVSAvoidwriting scheme complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies a periodic voltage pulse scheme consisting of a first voltage pulse to switch magnetization direction and a second voltage pulse of opposite polarity to stabilize the magnetic state. This periodic action sequence ensures reliable writing by first changing the magnetization direction and then stabilizing it, thereby reducing write error rates while maintaining a relatively simple device structure

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies a preliminary voltage pulse before the main switching pulse to prepare the magnetic state. The first voltage pulse reduces perpendicular magnetic anisotropy and coercivity, making the free layer more susceptible to subsequent magnetization switching. This preliminary action facilitates more reliable and efficient writing operations

Inventive Principle:

Principle #10Preliminary action

2Area of stationary object

If the bit size is reduced below 100 nm to increase storage density, then the storage capacity improves, but the power consumption and switching current requirements increase

Engineering Contradiction:

Improvebit sizeVSAvoidpower consumption

Core Design Contradiction:

Area of stationary objectVSUse of energy by moving object

Solution Approach 1:

The patent utilizes voltage-controlled magnetic anisotropy to dynamically change the magnetic properties of the free layer. By applying voltage pulses that modify perpendicular magnetic anisotropy and coercivity parameters, the system enables low-power magnetization switching in scaled-down bits below 100 nm, overcoming the increased power consumption typically associated with smaller feature sizes

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If existing writing schemes are used to switch magnetization, then the writing process is simple, but the magnetic state is not properly stabilized after writing

Engineering Contradiction:

Improvewriting process simplicityVSAvoidmagnetic state stability

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent employs a two-pulse periodic writing scheme where a first voltage pulse switches the magnetization direction and a second voltage pulse of opposite polarity stabilizes the magnetic state. This extended periodic action sequence maintains operational simplicity while ensuring proper stabilization of the written magnetic state, reducing write errors without complicating the writing process

Inventive Principle:

Principle #19Periodic action

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 RVP scheme effectively reduces write error rates by stabilizing the magnetic state and minimizing the number of write attempts required to achieve a desired bit error rate, improving the energy efficiency and reliability of MeRAM operations.

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

Methodology Applied

Scientific EffectVoltage-controlled magnetic anisotropy effect:

Data Source

PatentUS10460786B2Systems and methods for reducing write error rate in magnetoelectric random access memory through pulse sharpening and reverse pulse schemes

Publication Date: 2019.10.29 INSTON

AI summary

Reverse pulse schemes for reducing write error rate in magnetoelectric random access memory applications can be implemented in many different ways in accordance with various embodiments of the invention. 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 period of time across a magnetoelectric junction bit of the magnetoelectric random access memory cell and applying a voltage of a polarity opposite the given polarity across the magnetoelectric junction bit at the end of the application of the voltage of the given polarity, 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.