Multilayer Hardmask for MRAM MTJ Halogen Diffusion

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Solution Overview

Problem

Halogen diffusion into the metal hardmask of magnetic tunnel junction (MTJ) structures in MRAM devices degrades their magnetic properties, and existing solutions like thicker hardmasks do not mitigate this issue as future nodes require scaled MTJ structure heights.

Innovation Solution

A multilayered hardmask structure is introduced, comprising a halogen barrier hardmask layer and an upper hardmask layer, which prevents halogen ions from diffusing into the MTJ structure, using a combination of halogen-based etching and ion beam etching processes to pattern the layers while maintaining the MTJ structure integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a metal hardmask is used for patterning MTJ structure with halogen-based etching, then optimal MTJ structure profile is achieved, but halogen diffusion into the metal hardmask degrades the magnetic properties of the MTJ structure

Engineering Contradiction:

ImproveMTJ structure profileVSAvoidmagnetic properties of MTJ structure

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

A halogen barrier layer is introduced as an intermediary between the metal hardmask and the MTJ structure. This barrier layer (comprised of materials such as tantalum, tungsten, titanium, or their nitrides/oxides) specifically blocks halogen diffusion into the MTJ structure while allowing the metal hardmask to perform its patterning function with halogen-based etching processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The hardmask structure is transformed from a single metal layer to a composite structure consisting of multiple layers: the metal hardmask layer combined with a halogen barrier layer. This composite structure simultaneously provides the etching performance of metal and the diffusion protection of barrier materials.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a thicker metal hardmask is employed to prevent halogen diffusion, then some protection is provided, but future nodes require scaled MTJ structure heights which this solution does not accommodate

Engineering Contradiction:

Improveprotection against halogen diffusionVSAvoidscaling capability of MTJ structure height

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The hardmask function is segmented into two distinct layers: the metal hardmask layer for patterning and the separate halogen barrier layer for diffusion protection. This segmentation allows each layer to be optimized independently, enabling the barrier layer to provide protection while the overall structure accommodates scaled MTJ heights at future technology nodes.

Inventive Principle:

Principle #1Segmentation

3Reliability

If additional layers are added to the hardmask structure to prevent halogen diffusion, then halogen ion diffusion is blocked, but the device structure becomes more complex

Engineering Contradiction:

Improveprevention of halogen ion diffusionVSAvoidhardmask structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The halogen barrier layer is designed to serve multiple functions: it acts as a diffusion barrier, provides an etch stop layer, and can serve as a seed layer for subsequent metal deposition. This multi-functionality reduces the need for additional separate layers, thereby limiting the increase in structural complexity while achieving halogen diffusion protection.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The multilayered hardmask structure effectively prevents halogen ion diffusion, maintaining the magnetic properties of the MTJ structure and enabling scaling of the MTJ structure height without degrading its performance.

Implementation Method 1

The halogen barrier hardmask layer can prevent halogen ions that are used to pattern the upper hardmask layer from diffusing into the MTJ structure

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 2

Halogen-based metal hardmask etching is typically used to provide an optimal MTJ structure profile

Methodology Applied

Scientific EffectHalogen-based etching:

Implementation Method 3

The halogen barrier hardmask layer, the MTJ structure and the MTJ cap layer are then patterned utilizing ion beam etching

Methodology Applied

Scientific EffectIon beam etching: Ion Beam

Data Source

PatentUS10714683B2Multilayer hardmask for high performance MRAM devices

Publication Date: 2020.07.14 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Multilayered hardmask structures are provided which can prevent degradation of the performance of a magnetic tunnel junction (MTJ) structure. The multilayered hardmask structures include at least a halogen barrier hardmask layer and an upper hardmask layer. The halogen barrier hardmask layer can prevent halogen ions that are used to pattern the upper hardmask layer from diffusing into the MTJ structure.