Voltage Controlled Magnetic Anisotropy MRAM Free Layer

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Solution Overview

Problem

Magnetic random access memory (MRAM) technologies face challenges in balancing switching energy for writing and data retention, requiring a mechanism to reduce switching energy during writing while maintaining high switching energy for data stability during reading.

Innovation Solution

A magnetic memory element with a dielectric wall and an electrically conductive layer that surrounds the magnetic free layer, allowing for voltage-controlled magnetic anisotropy adjustment by applying a gate voltage to reduce perpendicular magnetic anisotropy during writing and increase it during reading, thereby controlling switching energy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If voltage-controlled magnetic anisotropy is used to reduce switching energy during writing, then write efficiency is improved, but data retention and thermal stability during reading may be compromised

Engineering Contradiction:

Improveswitching energyVSAvoiddata retention

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies dynamics by making the magnetic anisotropy可调 (tunable) through voltage control. The perpendicular magnetic anisotropy (PMA) in the CoFeB free layer is dynamically adjusted by applying different voltages to the underlying ferromagnetic metal layer, allowing the system to switch between low-anisotropy state (for easy writing) and high-anisotropy state (for stable data retention during reading).

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the magnetic anisotropy parameter through voltage control. By applying voltage to the ferromagnetic metal layer, the perpendicular magnetic anisotropy energy density (Keff) of the CoFeB layer is modified, enabling low switching energy during writing when voltage is applied, and high thermal stability during reading when voltage is removed.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If perpendicular magnetic anisotropy is increased for data stability during reading, then data retention is improved, but switching energy during writing increases

Engineering Contradiction:

Improvedata stabilityVSAvoidswitching energy

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The system dynamically adjusts the perpendicular magnetic anisotropy by applying voltage during writing operations to reduce switching energy, then removes the voltage during reading operations to maintain high data stability. This temporal separation of anisotropy states resolves the contradiction between easy switching and stable retention.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent employs periodic voltage application during write operations to temporarily reduce magnetic anisotropy for low-energy switching, followed by periodic removal of voltage during read operations to restore high anisotropy for stable data retention. This periodic modulation of anisotropy enables both low write energy and high read stability.

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

This approach reduces switching energy during writing, improving write efficiency while maintaining high switching energy for data stability and thermal and magnetic stability during reading, thus enhancing data retention and reducing read disturb.

Implementation Method 1

Methodology Applied

Scientific EffectVoltage controlled magnetic anisotropy:

Implementation Method 2

The switching of the MTJ element between high and low resistance states results from electron spin transfer

Methodology Applied

Scientific EffectElectron spin transfer:

Implementation Method 3

Magnetic Random Access Memory (MRAM) is a non-volatile data memory technology that stores data using magnetoresistive cells such as Magnetoresistive Tunnel Junction (MTJ) cells

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Data Source

PatentUS20200105831A1Magnetic memory element with voltage controlled magnetic anistropy

Publication Date: 2020.04.02 INTEGRATED SILICON SOLUTION CAYMAN INC

AI summary

A magnetic memory element having voltage controlled magnetic anisotropy for active control of switching energy (delta). The magnetic memory element can be formed as a pillar structure having a magnetic free layer a magnetic reference layer and a non-magnetic barrier layer located between the magnetic free layer and the magnetic reference layer. A dielectric wall is formed around the side of the magnetic free layer and an electrically conductive program line is formed around the dielectric wall, such that the dielectric wall separates the program line from the magnetic free layer. The electrically conductive program line is electrically connected with circuitry to selectively apply a gate voltage to the electrically conductive program line and across the dielectric layer. The circuitry can include a voltage source switching circuitry such as a transistor. The gate voltage advantageously reduces perpendicular magnetic anisotropy in the magnetic free layer, thereby reducing switching energy.