Adjustable MRAM Polarizer Layer for Switching Stability

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Solution Overview

Problem

Spin transfer torque magnetic random access memory (MRAM) devices face challenges in achieving high thermal stability and efficient switching while minimizing current requirements and chip area, as well as reducing the probability of unintended switching during read operations.

Innovation Solution

The MRAM device incorporates a magnetic tunnel junction (MTJ) with a polarizer layer that can adopt a programming or stabilizing magnetization direction, allowing for reduced switching currents and enhanced thermal stability by utilizing a polarizer layer with a magnetization vector that can switch between these directions, thereby destabilizing the free layer and facilitating efficient switching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a polarizer layer with fixed magnetization direction is used, then the free layer can be destabilized for efficient switching, but thermal stability deteriorates and unintended switching probability increases

Engineering Contradiction:

Improveswitching efficiencyVSAvoidthermal stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies the dynamics principle by making the polarizer layer's magnetization direction adjustable rather than fixed. The polarizer layer can switch between an in-plane magnetization direction (for efficient switching during write operations) and a perpendicular magnetization direction (for thermal stability during read operations and idle states). This dynamic reconfiguration resolves the contradiction between switching efficiency and thermal stability.

Inventive Principle:

Principle #15Dynamics

2Reliability

If high magnetic anisotropy is used to withstand thermal fluctuations, then thermal stability is improved, but switching current requirements increase

Engineering Contradiction:

Improvethermal stabilityVSAvoidswitching current

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies the preliminary action principle by pre-stabilizing the free layer through perpendicular dipolar coupling with the polarizer layer in its initial perpendicular magnetization state. This preliminary stabilization allows the use of higher magnetic anisotropy without proportionally increasing switching current, because the stabilization is already in place before switching begins. During write operations, the polarizer switches to in-plane direction to provide destabilizing field that assists switching.

Inventive Principle:

Principle #10Preliminary action

3Loss of time

If the free layer is destabilized for efficient switching, then switching time is reduced, but the probability of unintended switching during read operations increases

Engineering Contradiction:

Improveswitching timeVSAvoidread disturb rate

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent applies the periodic action principle by periodically reconfiguring the polarizer layer's magnetization direction based on operational mode. During write operations, the polarizer adopts an in-plane magnetization direction to destabilize the free layer and enable efficient switching. During read operations and idle states, the polarizer switches to a perpendicular magnetization direction to stabilize the free layer and prevent unintended switching. This periodic reconfiguration resolves the contradiction between switching speed and read reliability.

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 configuration enables lower switching currents, faster switching times, reduced read disturb rates, and improved thermal stability, enhancing the commercial applicability of MRAM devices by stabilizing the free layer during read operations and periods of inactivity.

Implementation Method 1

Spin transfer torque or spin transfer switching, uses spin-aligned ('polarized') electrons to change the magnetization orientation of the free layer in the magnetic tunnel junction

Methodology Applied

Scientific EffectSpin transfer torque:

Implementation Method 2

Due to the spin-polarized electron tunneling effect, the electrical resistance of the cell depends on the relative orientation of the magnetizations of the two layers

Methodology Applied

Scientific EffectSpin-polarized electron tunneling:

Implementation Method 3

the magnetic anisotropy of the free layer and reference layer needs to be large enough to withstand thermal fluctuations

Methodology Applied

Scientific EffectMagnetic anisotropy: Anisotropy

Implementation Method 4

the magnetization vector of polarizer layer is dipole-coupled to the magnetization vector of free layer

Methodology Applied

Scientific EffectDipolar coupling:

Data Source

PatentUS10580827B1Adjustable stabilizer/polarizer method for MRAM with enhanced stability and efficient switching

Publication Date: 2020.03.03 INTEGRATED SILICON SOLUTION CAYMAN INC

AI summary

A magnetoresistive random-access memory (MRAM) is disclosed. The MRAM bit cell consists of a magnetic tunnel junction stack having a significantly improved performance of the magnetic storage layer. The MRAM device utilizes a polarizer layer with a magnetic vector that can switch between a stabilizing magnetic direction and a programming magnetic direction.