MRAM Top Electrode TiN (111) Structure Against MTJ Oxidation

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Solution Overview

Problem

The oxidation of top electrodes during patterning in MRAM device fabrication can inhibit electron spin and magnetic reversibility of the magnetic tunnel junction (MTJ), leading to operational issues due to oxygen contamination.

Innovation Solution

A deposition technique using a single layer or multi-layers of titanium nitride with a (111) crystal orientation for the top electrode is employed, which reduces oxygen contamination and has a high oxidation temperature, thereby protecting the underlying layers of the MTJ.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional top electrode materials are used during patterning, then the patterning process can be completed, but oxygen contamination infiltrates the MTJ and inhibits electron spin and magnetic reversibility

Engineering Contradiction:

Improvepatterning process completionVSAvoidelectron spin reversibility

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

A protective capping layer is deposited over the top electrode before the patterning process. This preliminary action prevents oxygen contamination during subsequent patterning steps while allowing the patterning to proceed normally. The capping layer is removed after patterning completes, having served its protective function throughout the critical manufacturing steps.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The capping layer acts as an intermediary barrier between the oxygen-containing environment and the MTJ structure. It mediates the interaction by physically blocking oxygen diffusion paths during patterning, thereby protecting the magnetic properties of the MTJ without interfering with the top electrode's electrical function.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If the top electrode is exposed during subsequent processing, then processing steps can be completed, but oxidation temperature is exceeded and oxygen diffusion occurs

Engineering Contradiction:

Improveprocessing completionVSAvoidoxygen diffusion

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The capping layer is deposited in advance before any subsequent processing steps. It remains in place throughout all processing operations, preventing oxygen diffusion even when processing temperatures approach or exceed the oxidation temperature of the top electrode materials. This allows complete processing without oxygen contamination.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The capping layer creates an oxygen-barrier environment around the top electrode and MTJ structure during subsequent processing. It effectively establishes a localized inert atmosphere that prevents oxidation and oxygen diffusion, allowing standard processing equipment and atmospheres to be used without causing harmful effects.

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

3Device complexity

If no protective measure is taken, then the fabrication process is simpler, but the yield and acceptance of MRAM cells decrease due to oxygen contamination

Engineering Contradiction:

Improvefabrication process complexityVSAvoidyield and acceptance

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The capping layer is deposited as a preliminary step early in the fabrication sequence, before critical patterning and processing steps. This single additional deposition step protects against oxygen contamination throughout the entire subsequent process, dramatically improving yield and acceptance without requiring complex process modifications or multiple protective measures.

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 approach effectively inhibits oxygen infiltration, maintaining the electron spin reversibility and improving the yield and acceptance of MRAM cells by reducing oxygen diffusion into the MTJ, thus enhancing the reliability and efficiency of the MRAM device.

Implementation Method 1

Methodology Applied

Scientific EffectOxidation resistance: Oxidation

Implementation Method 2

A deposition technique using a single layer or multi-layers of titanium nitride with a (111) crystal orientation for the top electrode is employed

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS11864467B2MRAM fabrication and device

Publication Date: 2024.01.02 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A top electrode of a magnetoresistive random access memory (MRAM) device over a magnetic tunnel junction (MTJ) is formed using a film of titanium nitride oriented in a (111) crystal structure rather than a top electrode which uses tantalum, tantalum nitride, and/or a multilayer including tantalum and tantalum nitride.