Concave Sidewall Pedestal for MTJ Resputtering Control

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Solution Overview

Problem

The tapered conductive pedestals in magnetic tunnel junction (MTJ) devices are susceptible to resputtering, leading to electrical shorts due to the deposition of conductive metal particles on the sidewall of the MTJ pillar, particularly on the tunnel barrier material.

Innovation Solution

A conductive pedestal structure with a concave sidewall is formed between the bottom electrode and the MTJ pillar, which reduces the likelihood of resputtered metal particles depositing on the sidewall, achieved by etching the conductive pedestal to create an undercut shape after forming a passivation material spacer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of stationary object

If a tapered conductive pedestal is formed, then the physical distance between bottom electrode and MTJ pillar is created, but the tapered structure is susceptible to resputtering and deposition of conductive metal particles on MTJ pillar sidewall

Engineering Contradiction:

Improvephysical distance between bottom electrode and MTJ pillarVSAvoidresputtering and deposition of conductive metal particles

Core Design Contradiction:

Length of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The conductive pedestal is designed with a concave sidewall curvature instead of a tapered shape. This concave geometry creates an undercut profile that prevents resputtered metal particles from reaching and depositing on the MTJ pillar sidewall, while still maintaining the necessary physical spacing between the bottom electrode and MTJ pillar.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The pedestal structure employs asymmetric geometry with a concave sidewall profile rather than a symmetric tapered shape. This asymmetry is strategically designed to block the trajectory of resputtered particles, allowing the pedestal to fulfill its spacing function while eliminating the harmful deposition effect.

Inventive Principle:

Principle #4Asymmetry

2Manufacturing precision

If ion beam etching is performed at a different angle for cleaning, then cleaning effectiveness is improved, but the tapered pedestal is more susceptible to resputtering

Engineering Contradiction:

Improvecleaning effectiveness of MTJ pillar sidewallVSAvoidresputtered conductive metal particles from pedestal

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The concave sidewall geometry of the pedestal converts the harmful resputtering effect into a beneficial shielding mechanism. The undercut profile created by the concave shape causes resputtered particles to be redirected away from the MTJ pillar, transforming the potential contamination source into a protective feature that actually prevents deposition.

Inventive Principle:

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

3Reliability

If resputtered conductive metal particles deposit on the tunnel barrier material, then electrical shorts occur, but the concave pedestal structure prevents this deposition

Engineering Contradiction:

Improveprevention of electrical shorts in MTJ deviceVSAvoidconductive pedestal structure with concave sidewall

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The concave sidewall profile is formed in advance during the pedestal fabrication process, before the ion beam etching cleaning step. This preliminary geometric configuration ensures that when resputtering occurs during cleaning, the particles are already directed away from the MTJ pillar by the pre-established undercut profile, preventing deposition before it can cause electrical shorts.

Inventive Principle:

Principle #10Preliminary 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 significantly reduces electrical shorts caused by resputtered conductive metal particles, enhancing the reliability and performance of the MTJ device by preventing deposition on the tunnel barrier material.

Implementation Method 1

a passivation material spacer is formed on a sidewall of each of the top electrode and the MTJ pillar

Methodology Applied

Scientific EffectPhysical Vapour Deposition: Physical Vapour Deposition

Implementation Method 2

The conductive pedestal having the tapered sidewall is then etched to provide a conductive pedestal structure having a concave sidewall

Methodology Applied

Scientific EffectSputtering: Sputtering

Data Source

PatentUS11502243B2Structured pedestal for MTJ containing devices

Publication Date: 2022.11.15 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A magnetic tunnel junction (MTJ) containing device is provided that includes an undercut conductive pedestal structure having a concave sidewall positioned between a bottom electrode and a MTJ pillar. The geometric nature of such a conductive pedestal structure makes the pedestal structure unlikely to be resputtered and deposited on a sidewall of the MTJ pillar, especially the sidewall of the tunnel barrier of the MTJ pillar. Thus, electrical shorts caused by depositing resputtered conductive metal particles on the sidewall of the tunnel barrier of the MTJ pillar are substantially reduced.