Magnetic Liners Shield MRAM Cells from Bit Line Interference

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Solution Overview

Problem

Conventional magnetic random access memory (MRAM) cells face issues with memory volatility due to patterning and integration techniques, requiring external field bias for spin-torque switching, which is influenced by stray magnetic fields from local wires, leading to operational offset and data errors.

Innovation Solution

The use of magnetic liners, composed of materials like Ni, Fe, and Co, to divert magnetic fields away from magnetic tunnel junctions (MTJs) in MRAM cells, eliminating the need for external field bias by shielding the cells from current-induced magnetic fields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional patterning and integration techniques are used for MRAM cells, then manufacturing is simpler, but stray magnetic fields from local wires cause operational offset and data errors

Engineering Contradiction:

Improvedata accuracyVSAvoidcell structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A non-magnetic spacer layer is introduced between the bit line and the magnetic tunnel junction (MTJ) to act as a magnetic field shield. This intermediary structure blocks stray magnetic fields generated by current flowing through the bit line from reaching the MTJ, thereby preventing operational offset and data errors while maintaining conventional patterning techniques

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bit line structure is segmented into multiple parts: a lower bit line portion, a non-magnetic spacer layer, and an upper bit line portion. This segmentation isolates the magnetic field generation zone from the sensitive MTJ region, allowing current flow while preventing magnetic field interference

Inventive Principle:

Principle #1Segmentation

2Ease of operation

If external field bias is applied for spin-torque switching, then switching operation is achieved, but power consumption increases and operational complexity increases

Engineering Contradiction:

Improveswitching operationVSAvoidpower consumption

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

The patent converts the harmful stray magnetic field from the bit line into a beneficial switching mechanism. By carefully controlling the bit line current, the stray magnetic field itself performs the switching function that would otherwise require external field bias, thereby reducing power consumption and operational complexity

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If bit line current is increased for reliable switching, then switching reliability improves, but magnetic field interference with MTJ increases

Engineering Contradiction:

Improveswitching reliabilityVSAvoidmagnetic field interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The non-magnetic spacer layer serves as a magnetic field shield that allows high bit line currents to flow for reliable switching while preventing the associated magnetic field interference from affecting the MTJ operation

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

This solution effectively suppresses stray magnetic fields, reducing operational offsets and data errors, allowing for reliable spin-torque switching without external field bias, thereby enhancing the stability and accuracy of MRAM cells.

Implementation Method 1

The magnetic liner may comprise Ni, Fe, and/or Co... techniques for diverting magnetic fields created by the electric currents flowing in local wires

Methodology Applied

Scientific EffectMagnetic field diversion: Magnetic Field

Implementation Method 2

These techniques allow for spin-torque switching via direct current without the need for an external field bias... effectively suppresses stray magnetic fields

Methodology Applied

Scientific EffectMagnetic shielding: Magnetic Field

Implementation Method 3

injected spin polarized electrons interact with the magnetic moment of a free layer in the MRAM cell and transfer their angular momentum (commonly known as spin momentum transfer, or SMT)

Methodology Applied

Scientific EffectSpin momentum transfer: Angular Momentum

Implementation Method 4

recent advances in high tunneling magnetoresistance (TMR) devices with magnesium oxide (MgO) barriers, including devices with low resistance-area (RA) product

Methodology Applied

Scientific EffectTunneling magnetoresistance: Magnetoresistance

Data Source

PatentEP2255361B1Magnetically de-coupling magnetic memory cells and bit/word lines for reducing bit selection errors

Publication Date: 2022.07.06 GLOBALFOUNDRIES US INC

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AI summary

Techniques for shielding magnetic memory cells from magnetic fields are presented. In accordance with aspects of the invention, a magnetic storage element is formed with at least one conductive segment electrically coupled to the magnetic storage element. At least a portion of the conductive segment is surrounded with a magnetic liner. The magnetic liner is operative to divert at least a portion of a magnetic field created by a current passing through the conductive segment away from the magnetic storage element.