SOT-MRAM Lateral Alignment and Single Etch Process

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Solution Overview

Problem

Conventional spin-orbit torque magnetoresistive random-access memory (SOT-MRAM) devices experience current flow loss due to shunting current and defects in the SOT layer, which reduces switching efficiency and thermal stability, and the fabrication process is challenging due to the use of the SOT layer as an etch stop.

Innovation Solution

The SOT layer is laterally aligned with the magnetic tunnel junction (MTJ) stack and formed over a spacer between interconnect structures, eliminating shunting current by ensuring all electric current passes through the SOT layer under the MTJ, and the MTJ and SOT layers are patterned in a single etch process for self-alignment and reduced defect formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the SOT layer is used as an etch stop in conventional fabrication, then the MTJ stack can be patterned, but the quality of the SOT layer deteriorates and defects are introduced

Engineering Contradiction:

Improvepattern alignmentVSAvoidSOT layer quality

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent introduces a separate etch stop layer distinct from the SOT layer, dividing the functions of etching termination and spin-orbit torque generation into separate components. This prevents the SOT layer from being damaged during etching while maintaining pattern alignment capability through the dedicated etch stop layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs an intermediary etch stop layer positioned between the MTJ stack and the SOT layer. This intermediary layer serves as the etch termination point during fabrication, protecting the SOT layer from etching damage while allowing precise pattern transfer to the MTJ stack.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the MTJ stack and SOT layer have mismatched sizes, then fabrication is simplified, but current flow loss increases due to shunting current

Engineering Contradiction:

Improvefabrication simplicityVSAvoidcurrent flow loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent implements a method where the SOT layer width is dynamically adjusted to match the MTJ stack width through a multi-step patterning process. This ensures optimal current flow alignment while maintaining fabrication flexibility, eliminating shunting current without sacrificing manufacturing ease.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the width parameter of the SOT layer to match the MTJ stack width precisely. By adjusting this geometric parameter through controlled patterning steps, the invention eliminates current mismatch and shunting current while maintaining ease of fabrication through standard photolithography processes.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If conventional SOT-MRAM structures are used, then device structure is simple, but Joule heating increases due to shunting current

Engineering Contradiction:

Improvestructure simplicityVSAvoidJoule heating

Core Design Contradiction:

Device complexityVSTemperature

Solution Approach 1:

The patent extracts the shunting current path from the system by precisely aligning the SOT layer width with the MTJ stack width. This removal of the harmful current path eliminates the source of Joule heating while maintaining the overall simplicity of the SOT-MRAM device structure.

Inventive Principle:

Principle #2Taking out (Extraction)

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 current flow loss, increases switching efficiency, and improves thermal stability by ensuring all current contributes to spin-orbit coupling, while minimizing defects and Joule heating, resulting in improved SOT-MRAM device performance.

Implementation Method 1

spin-orbit torque (SOT) MRAM causes the switching of the spinning direction of the electrons by applying a current to a heavy metal layer, or spin-orbit torque (SOT) layer, adjacent the MTJ stack

Methodology Applied

Scientific EffectSpin-orbit coupling:

Implementation Method 2

Magnetoresistive random-access memory (MRAM) is a type of memory device containing an array of MRAM cells that store data using resistance values of MRAM cells

Methodology Applied

Scientific EffectMagnetoresistance: Magnetoresistance

Implementation Method 3

The SOT layer is laterally aligned with the magnetic tunnel junction (MTJ) stack and formed over a spacer between interconnect structures

Methodology Applied

Scientific EffectPhysical separation:

Data Source

PatentUS12201030B2Spin-orbit torque MRAM structure and manufacture thereof

Publication Date: 2025.01.14 APPLIED MATERIALS INC

AI summary

Embodiments of the present disclosure generally include spin-orbit torque magnetoresistive random-access memory (SOT-MRAM) devices and methods of manufacture thereof. The SOT-MRAM devices described herein include an SOT layer laterally aligned with a magnetic tunnel junction (MTJ) stack and formed over a trench in an interconnect. Thus, the presence of the SOT layer outside the area of the MTJ stack is eliminated, and electric current passes from the interconnect to the SOT layer by SOT-interconnect overlap. The devices and methods described herein reduce the formation of shunting current and enable the MTJ to self-align with the SOT layer in a single etching process.