STTMRAM Free Layer Edge Magnetization for Low Voltage Switching

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Solution Overview

Problem

Magnetic random access memory (MRAM) with magnetic tunnel junctions (MTJs) faces challenges in reducing the threshold voltage and current required to switch the free layer's magnetic state due to inconsistent coercivity across the free layer, limiting the ease of switching and increasing the effective coercivity ratio.

Innovation Solution

A spin torque transfer magnetic random access memory (STTMRAM) element is designed with a reference layer, a junction layer, a free layer, and a fixed layer, where the perpendicular magnetic components of the fixed and reference layers cancel each other, and the free layer has an in-plane magnetization field at its edges, reducing the effective coercivity and allowing easier switching with lower voltage and current requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If perpendicular anisotropic field (Hk) of the free layer is lowered to ease switching, then switching becomes easier, but effective coercivity (Hc) at edges increases undesirably

Engineering Contradiction:

Improveease of switchingVSAvoideffective coercivity ratio

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent applies different magnetic field characteristics to different regions of the free layer. The center region maintains perpendicular magnetization with lower Hc for easy switching, while the edge regions are engineered to have in-plane magnetization that compensates for the edge effect, preventing excessive Hc increase at edges.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the magnetization orientation parameter from purely perpendicular to a hybrid configuration. By introducing in-plane magnetization components at the edges through specific layer结构设计 (including the capping layer and magnetic field application), the effective Hc distribution is optimized across different regions of the free layer.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If spin torque transfer is used to switch magnetization, then non-volatile memory is achieved, but threshold voltage and current requirements are too high for practical applications

Engineering Contradiction:

Improvenon-volatile memory capabilityVSAvoidthreshold voltage and current

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent introduces a compensating magnetic field from the capping layer that counteracts the harmful edge effect in the free layer. This compensation reduces the effective Hc that opposes switching, thereby lowering the spin torque threshold current required to switch the magnetization state while maintaining non-volatile memory functionality.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Solution Approach 2:

The capping layer acts as an intermediary that mediates between the free layer's perpendicular magnetization and the external environment. It generates a compensating magnetic field that reduces the effective coercivity at edges, facilitating easier switching with lower current while preserving the non-volatile memory特性.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution achieves a significant reduction in switching voltage by approximately 70% compared to prior art structures, enabling easier and more efficient switching of the free layer's magnetic state while maintaining symmetrical switching performance.

Implementation Method 1

the perpendicular magnetic components of the fixed layer and the reference layer substantially cancel each other

Methodology Applied

Scientific EffectMagnetic field cancellation: Magnetic Field

Implementation Method 2

spin torque from electrons transmitted from the pinned layer to the free layer orientate the free layer magnetization in a direction that is parallel to that of the reference or pinned layer. When electrons flow from the free layer to the pinned layer, spin torque from electrons that are reflected from the pinned layer back into the free layer orientate the free layer magnetization to be anti-parallel relative to the magnetization of the pinned layer

Methodology Applied

Scientific EffectSpin torque transfer:

Data Source

PatentUS8565010B2Magnetic random access memory with field compensating layer and multi-level cell

Publication Date: 2013.10.22 AVALANCHE TECHNOLOGY INC

AI summary

A spin toque transfer magnetic random access memory (STTMRAM) element comprises a reference layer formed on a substrate, with a fixed perpendicular magnetic component. A junction layer is formed on top of the reference layer and a free layer is formed on top of the junction layer with a perpendicular magnetic orientation, at substantially its center of the free layer and switchable. A spacer layer is formed on top of the free layer and a fixed layer is formed on top of the spacer layer, the fixed layer has a fixed perpendicular magnetic component opposite to that of the reference layer. The magnetic orientation of the free layer switches relative to that of the fixed layer. The perpendicular magnetic components of the fixed layer and the reference layer substantially cancel each other and the free layer has an in-plane edge magnetization field.