MTJ Bottom Electrode Recessed Region Shields Resputtered Particles

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Solution Overview

Problem

In magnetic tunnel junction (MTJ) devices, the deposition of resputtered conductive metal particles from the bottom electrode onto the sidewall of the MTJ pillar can cause electrical shorts, particularly when the critical dimension of the bottom electrode exceeds that of the MTJ pillar, due to the difficulty in maintaining circularity at small feature sizes.

Innovation Solution

A bottom electrode structure with a mesa portion surrounded by a recessed region, where the recessed region is laterally adjacent to a dielectric material, preventing the deposition of resputtered conductive metal particles by changing the angle of resputtering and shielding the area from impinging ions, and a dielectric material layer is used to fill the recessed region to further prevent deposition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the critical dimension of the bottom electrode exceeds that of the MTJ pillar, then the bottom electrode can be easier to manufacture, but resputtered conductive metal particles deposit on the sidewall of the MTJ pillar causing electrical shorts

Engineering Contradiction:

Improveease of manufacturing bottom electrodeVSAvoidelectrical short prevention

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The bottom electrode is segmented into a mesa portion and a recessed region, creating distinct functional zones. The mesa portion maintains electrical connectivity while the recessed region prevents particle deposition, resolving the contradiction between ease of manufacture and reliability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The recessed region acts as an intermediary structure between the bottom electrode and the MTJ pillar sidewall. It intercepts resputtered particles before they can reach the MTJ pillar, preventing electrical shorts while maintaining the larger bottom electrode dimension for ease of manufacture.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If ion beam etching is used to clean the sidewall of the MTJ pillar, then the sidewall cleanliness is improved, but resputtered conductive metal particles deposit on the tunnel barrier material causing electrical shorts

Engineering Contradiction:

Improvesidewall cleanlinessVSAvoidelectrical short prevention

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The recessed region converts the harmful effect of ion beam etching (resputtering particles) into a beneficial shielding mechanism. The same ion beam that cleans the sidewall now deposits particles into the recessed region instead of onto the MTJ pillar, maintaining cleanliness while preventing shorts.

Inventive Principle:

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

Solution Approach 2:

The recessed region is pre-formed to intercept resputtered particles before they can reach the tunnel barrier material. This preliminary protective structure prevents the harmful deposition from occurring in the first place, allowing ion beam etching to proceed effectively.

Inventive Principle:

Principle #9Preliminary anti-action

3Device complexity

If the bottom electrode has a planar topmost surface, then the manufacturing process is simpler, but the angle of resputtering causes particles to deposit on the MTJ pillar

Engineering Contradiction:

Improvebottom electrode structure complexityVSAvoidparticle deposition prevention

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The bottom electrode structure transitions from a two-dimensional planar surface to a three-dimensional structure with a recessed region. This dimensional change creates a new spatial dimension for particle interception, preventing deposition on the MTJ pillar while maintaining manufacturing simplicity.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 effectively prevents the deposition of resputtered conductive metal particles onto the MTJ pillar, reducing the likelihood of electrical shorts and improving device performance by maintaining the integrity of the tunnel barrier.

Implementation Method 1

the bottom electrode that is connected to the MTJ pillar can be a source of resputtered conductive metal particles that can deposit on a sidewall of the MTJ pillar

Methodology Applied

Scientific EffectResputtering: Sputtering

Data Source

PatentUS11404634B2Structured bottom electrode for MTJ containing devices

Publication Date: 2022.08.02 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

A bottom electrode structure for a magnetic tunnel junction (MTJ) containing device is provided. The bottom electrode structure includes a mesa portion that is laterally surrounded by a recessed region. The recessed region of the bottom electrode structure is laterally adjacent to a dielectric material, and a MTJ pillar is located on the mesa portion of the bottom electrode structure. Such a configuration shields the recessed region from impinging ions thus preventing deposition of resputtered conductive metal particles from the bottom electrode onto the MTJ pillar.