Multilayer Interconnect Superlattice for Skin Effect Suppression

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Solution Overview

Problem

Conventional subtractive patterning processes for metal/ferromagnetic metal multilayer interconnects suffer from contamination issues due to remnants of unwanted metal layers, which can lead to unsatisfactory performance and reliability in interconnect applications, particularly affecting skin effect suppression in alternating electric currents.

Innovation Solution

A damascene process is employed, where a Ta barrier is deposited after an interlayer dielectric etch, followed by conformable deposition of ferromagnetic metal layers and carbon hardmask fill and recess operations, allowing for the formation of a superlattice structure with vertically stacked ferromagnetic and metal layers, preventing diffusion and contamination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of substance

If a lift-off technique is used for subtractive patterning, then the target metal layer can be removed, but remnants of unwanted metal layers remain and cause contamination

Engineering Contradiction:

Improvemetal layer removalVSAvoidcontamination

Core Design Contradiction:

Loss of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent inverts the conventional subtractive patterning approach by using additive patterning instead. Rather than depositing metal and then removing unwanted portions (lift-off), the method deposits sacrificial material first, forms patterns, and then uses those patterns to guide metal deposition only where needed. This inversion eliminates the contamination problem inherent in lift-off techniques.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces sacrificial material as an intermediary substance that facilitates the patterning process. This sacrificial material is deposited, patterned, and then used as a template for metal deposition. After the metal is deposited, the sacrificial material is removed, leaving clean metal patterns without contamination. The intermediary serves as a temporary structure that enables precise metal placement without direct contact between metal and unwanted areas.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If conventional subtractive patterning is used, then metal layers can be formed, but performance and reliability are compromised due to contamination

Engineering Contradiction:

Improvemetal layer formationVSAvoidinterconnect performance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent inverts the patterning sequence to improve reliability. Instead of forming metal layers and then removing excess material (which causes contamination and reliability issues), the method first deposits and patterns sacrificial material, then deposits metal only in desired locations. This additive approach ensures no contamination occurs, thereby improving interconnect performance and reliability while maintaining ease of manufacture.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The sacrificial material acts as a disposable temporary structure that enables reliable metal patterning. This material is deposited, patterned, used as a template for metal deposition, and then completely removed. Its temporary nature allows it to serve its patterning function without compromising the final device reliability, as it is discarded after serving its purpose.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If skin effects are present in interconnects, then current distribution is uneven, but ferromagnetic metals can suppress skin effects through negative permeability

Engineering Contradiction:

Improvecurrent distributionVSAvoidmultilayer structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs composite multilayer structures combining ferromagnetic metal layers with non-magnetic metal layers. The ferromagnetic layers provide negative permeability at RF frequencies to suppress skin effects and improve current distribution. The non-magnetic layers provide good electrical conductivity. This composite structure leverages the complementary properties of different materials to achieve both skin effect suppression and low resistance, addressing the reliability issue while managing the inherent complexity through functional integration.

Inventive Principle:

Principle #40Composite materials

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 suppresses skin effects by utilizing the negative permeability of ferromagnetic metals at RF frequencies, enhancing the performance and reliability of interconnects while avoiding contamination issues associated with conventional lift-off techniques.

Implementation Method 1

Skin effects are a condition of alternating electric current (AC) in a conductor that is characterized by a current distribution that is largest near the surface of the conductor

Methodology Applied

Scientific EffectSkin effect: Skin Effect

Implementation Method 2

Metal/ferromagnetic metal multilayer interconnects suppress skin effects because of the negative permeability of ferromagnetic metals at radio frequencies (RF)

Methodology Applied

Scientific EffectNegative permeability: Ferromagnetism

Implementation Method 3

a Ta barrier is deposited after an interlayer dielectric etch

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Implementation Method 4

conformable deposition of ferromagnetic metal layers

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentUS11605592B2Method to fabricate metal and ferromagnetic metal multilayer interconnect line for skin effect suppression

Publication Date: 2023.03.14 INTEL CORP

AI summary

A multilayer conductive line is disclosed. The multilayer conductive line includes a dielectric layer, a Ta barrier layer on the dielectric layer and a superlattice on the Ta barrier layer. The superlattice includes a plurality of interleaved ferromagnetic and non-ferromagnetic material.