Magnetic Memory Device ALD Interface Layer

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Solution Overview

Problem

Magnetic tunnel junction (MTJ) devices face degradation of magnetic anisotropy and metal interface damage during encapsulation due to high energy processes like PECVD, which affects the magnetic properties of CoFeB alloy layers.

Innovation Solution

A method involving atomic layer deposition (ALD) to form a thin interface layer using self-activated surface chemistry with low thermal or plasma energy, followed by a silicon nitride encapsulation layer, to prevent damage and maintain magnetic properties during processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If PECVD process is used to deposit silicon nitride encapsulation layer, then adequate film quality and conformality are achieved, but magnetic anisotropy of MTJ device is degraded due to high energy ions and reactive radicals

Engineering Contradiction:

Improvefilm conformalityVSAvoidmagnetic anisotropy

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

A thin interface layer (1-3 nm) of silicon nitride or silicon oxynitride is deposited between the MTJ device stack and the encapsulation layer. This intermediary layer acts as a buffer that protects the magnetic layers from direct exposure to high energy ions and reactive radicals during PECVD processing, while still allowing the encapsulation layer to provide conformal coverage and protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The interface layer is deposited in advance before the main encapsulation layer. This preliminary action creates a protective barrier on the magnetic layers before they are exposed to the harsh conditions of PECVD processing, preventing damage to magnetic anisotropy while enabling subsequent conformal encapsulation.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If PECVD process is used for encapsulation, then protection against oxidation is provided, but metal interfaces are damaged due to reactive radical reactions and high reactivity at elevated temperatures

Engineering Contradiction:

Improveoxidation protectionVSAvoidinterface damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The interface layer serves as a protective intermediary between the metal layers and the PECVD plasma environment. It absorbs the harmful effects of reactive radicals and high energy species, preventing them from directly attacking and damaging the metal interfaces while still allowing the PECVD process to proceed for oxidation protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The interface layer is deposited beforehand to cushion and absorb the impact of high energy ions and reactive radicals during encapsulation. This prior cushioning prevents direct damage to the metal interfaces while maintaining the protective oxidation barrier function.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Reliability

If thin interface layer is deposited using ALD, then magnetic properties are preserved, but additional process step is added to the fabrication sequence

Engineering Contradiction:

Improvemagnetic property preservationVSAvoidprocess steps

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The interface layer deposition is merged with the existing encapsulation process flow. The thin ALD-deposited interface layer (1-3 nm) is deposited as a preliminary step before the main PECVD encapsulation layer, combining the benefits of both ALD (precision, low damage) and PECVD (conformality, protection) in a single integrated process sequence.

Inventive Principle:

Principle #5Merging (Combining)

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 approach effectively protects magnetic layers from degradation, preserving magnetic properties and preventing nitridation, while ensuring conformal coverage and stability of the device stack without altering the standard process flow.

Implementation Method 1

depositing an interface layer conformally over the device stack using an atomic layer deposition process

Methodology Applied

Scientific EffectAtomic layer deposition: Chemical Vapour Deposition

Implementation Method 2

depositing an interface layer conformally over the device stack using an atomic layer deposition process, the interface layer comprising a first insulator material

Methodology Applied

Scientific EffectSelf-activated surface chemistry: Chemical Bonding

Implementation Method 3

A plasma enhanced chemical vapor deposition process (or, simply, plasma enhanced chemical vapor deposition), sometimes referred to as PECVD is the most commonly used technique for forming an encapsulating SiN film

Methodology Applied

Scientific EffectPlasma enhanced chemical vapor deposition: Plasma Enhanced Chemical Vapour Deposition

Data Source

PatentUS10312432B2Magnetic memory device and techniques for forming

Publication Date: 2019.06.04 VARIAN SEMICON EQUIP ASSC INC

AI summary

A method may include: providing a device stack, the device stack comprising sidewall portions and extending above a substrate base, the device stack further including a plurality of metal layers; depositing an interface layer conformally over the device stack using an atomic layer deposition process, the interface layer comprising a first insulator material; depositing an encapsulation layer on the interface layer, the encapsulation layer comprising a second insulator material; and depositing an interlevel dielectric disposed on the encapsulation layer, the interlevel dielectric comprising a third insulator material.