MRAM Free Layer Patterning via Chemical Oxidation

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Solution Overview

Problem

Current methods for manufacturing magnetoresistive random access memory (MRAM) devices face challenges in forming precise free layer patterns and tunnel barrier layers, leading to inefficiencies and potential electrical shorts during the physical etching process.

Innovation Solution

A method involving the sequential formation of a lower electrode, preliminary free layer, and sacrificial layer, followed by partial oxidation of the second free layer to create a second free layer pattern, and the subsequent formation of a tunnel barrier layer and fixed layer structure, minimizing the physical etching process and preventing magnetic material attachment to the sidewalls.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If physical etching process is used to form free layer patterns and tunnel barrier layers, then manufacturing capability is achieved, but manufacturing precision deteriorates due to potential electrical shorts and magnetic material attachment to sidewalls

Engineering Contradiction:

Improvemanufacturing capabilityVSAvoidpattern precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent replaces the physical etching process (mechanical removal of material) with a chemical oxidation process. Specifically, a sacrificial layer is oxidized in situ to form the tunnel barrier layer and free layer patterns, eliminating the need for physical etching that causes sidewall attachment and electrical shorts. This substitution of mechanical process with chemical process resolves the contradiction by maintaining manufacturability while dramatically improving pattern precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a sacrificial layer as an intermediary material that facilitates the formation of the tunnel barrier layer and free layer patterns through oxidation. This intermediary layer enables precise pattern formation by serving as a template that is selectively oxidized, avoiding the harmful effects of direct physical etching on the magnetic layers while maintaining manufacturing capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If physical etching process is used, then layer patterning is achieved, but reliability deteriorates due to electrical shorts

Engineering Contradiction:

Improvepatterning capabilityVSAvoiddevice reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent replaces physical etching with chemical oxidation to form patterns. The sacrificial layer is oxidized in situ to create the tunnel barrier layer and free layer patterns without mechanical contact, eliminating the source of electrical shorts that occur when physical etching tools attach to sidewalls and create conductive pathways. This maintains patterning capability while significantly improving device reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If physical etching process is used to form precise patterns, then manufacturing speed is maintained, but manufacturing precision deteriorates due to magnetic material attachment to sidewalls

Engineering Contradiction:

Improvemanufacturing speedVSAvoidpattern precision

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent replaces physical etching with chemical oxidation, where the sacrificial layer is oxidized in situ to form precise patterns. This chemical process occurs uniformly throughout the sacrificial layer volume simultaneously, maintaining high manufacturing speed while eliminating the sidewall attachment problem inherent in sequential physical etching processes, thereby achieving both high productivity and high precision.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 enables the efficient formation of MRAM devices with reduced physical etching, minimizing electrical shorts and improving the reliability of the magnetic tunnel junction structure.

Implementation Method 1

performing an ion implantation process using the mask as an ion implantation mask to partially implant oxygen ions into the sacrificial layer, the first free layer, and the lower electrode layer

Methodology Applied

Scientific EffectIon implantation: Ion Implantation

Implementation Method 2

diffusing the oxygen ions implanted into the first free layer into the second free layer

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 3

the fixed layer pattern structure, tunnel barrier layer pattern, and free layer pattern may be formed by a physical etching process such as an ion sputtering process

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS10134980B2Magnetoresistive random access memory device

Publication Date: 2018.11.20 SAMSUNG ELECTRONICS CO LTD

AI summary

In a method of manufacturing an MRAM device, a lower electrode and a preliminary first free layer pattern sequentially stacked are formed on a substrate. An upper portion of the preliminary first free layer pattern is removed to form a first free layer pattern. A second free layer and a tunnel barrier layer are sequentially formed on the first free layer pattern. The second free layer is partially oxidized to form a second free layer pattern. A fixed layer structure is formed on the tunnel barrier layer.