Bonding Pad Electromigration Barrier Layer Design

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Solution Overview

Problem

Copper bonding pads in semiconductor devices are prone to recesses near metallic diffusion barrier layers, leading to accelerated copper electromigration-induced void formation, which can result in poor electrical connections and device failure.

Innovation Solution

Incorporating a metallic electromigration barrier layer between the copper fill material and the metallic liner in the bonding pads, which reduces copper diffusion and void formation by acting as a copper diffusion barrier.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If copper bonding pads are used in semiconductor devices, then good electrical conductivity is achieved, but copper electromigration-induced void formation occurs at interfaces leading to poor electrical connections

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidcopper electromigration and void formation

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a metallic electromigration barrier layer as an intermediary between the copper bonding pad and the metallic liner. This barrier layer acts as a mediator that prevents direct interaction between copper atoms and the metallic liner, blocking copper diffusion and electromigration while maintaining electrical conductivity. The barrier layer serves as a protective interface that eliminates the harmful copper migration effect without compromising the electrical connection function.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The bonding pad structure is designed as a composite material system consisting of multiple layers: copper fill material, metallic electromigration barrier layer, and metallic liner. This composite structure combines the high electrical conductivity of copper with the diffusion-blocking properties of the metallic barrier layer and liner, creating a multi-functional material system that simultaneously achieves good electrical connection and prevents copper electromigration.

Inventive Principle:

Principle #40Composite materials

2Object-generated harmful factors

If metallic diffusion barrier layers are used to prevent copper migration, then copper electromigration is reduced, but recesses form near the barrier layers leading to poor electrical connections

Engineering Contradiction:

Improvecopper electromigrationVSAvoidelectrical connection quality

Core Design Contradiction:

Object-generated harmful factorsVSReliability

Solution Approach 1:

The patent applies local quality by creating a metallic liner with non-uniform thickness around the copper bonding pad. The liner thickness is specifically increased at regions adjacent to the metallic electromigration barrier layer where copper diffusion is most likely to occur. This localized thickening provides enhanced diffusion protection at critical interfaces while maintaining overall electrical connection quality, preventing both electromigration and recess formation.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The metallic liner is designed with excess material that protrudes beyond the copper bonding pad boundaries, creating a protective cushion or overhang before copper diffusion can occur. This prior cushioning of metallic material prevents copper atoms from migrating outward and forming voids at the interface, addressing the problem before it can manifest as recesses or poor electrical connections.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Ease of manufacture

If the bonding pad structure is simplified, then manufacturing ease is improved, but copper diffusion and void formation cannot be effectively prevented

Engineering Contradiction:

Improvebonding pad fabrication simplicityVSAvoidcopper diffusion and void formation

Core Design Contradiction:

Ease of manufactureVSObject-generated harmful factors

Solution Approach 1:

The bonding pad structure is segmented into distinct functional layers: copper fill material layer, metallic electromigration barrier layer, and metallic liner. This segmentation allows each layer to be deposited and processed independently using standard semiconductor fabrication techniques, maintaining manufacturing ease while enabling effective copper diffusion prevention through the specialized barrier layer configuration.

Inventive Principle:

Principle #1Segmentation

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 metallic electromigration barrier layer effectively reduces or eliminates void formation at the interfaces between bonding pads, enhancing electrical connectivity and device reliability by preventing copper migration and maintaining stable connections.

Implementation Method 1

a metallic electromigration barrier layer contacting the first metallic fill material portion and adjoined to the first metallic liner

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion Barrier

Data Source

PatentUS11270963B2Bonding pads including interfacial electromigration barrier layers and methods of making the same

Publication Date: 2022.03.08 SANDISK TECHNOLOGIES LLC

AI summary

A semiconductor die includes a first pad-level dielectric layer embedding first bonding pads and located over a first substrate. Each of the first bonding pads is located within a respective pad cavity in the first pad-level dielectric layer. Each of the first bonding pads includes a first metallic liner containing a first metallic liner material and contacting a sidewall of the respective pad cavity, a first metallic fill material portion embedded in the first metallic liner, and a metallic electromigration barrier layer contacting the first metallic fill material portion and adjoined to the first metallic liner.