Dummy Pad Bonding Structure for Stress-Resistant Die Stacking

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Solution Overview

Problem

The challenge in packaging integrated circuits is the formation of complex structures with multiple device dies, particularly in bonding structures where dangling bonds can lead to reduced bond strength and increased stress, affecting the reliability and performance of the package.

Innovation Solution

The solution involves forming dummy pads in the dielectric layer of lower-tier dies, which are bonded to dangling pads in upper-tier dies, enhancing bond strength and reducing stress through the use of stress-absorbing buffer layers and dielectric materials, and employing fusion bonding techniques to improve the structural integrity of the package.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If multiple device dies are bonded together to form complex package structures, then device functionality and integration are improved, but bond strength and structural stability deteriorate due to dangling bonds

Engineering Contradiction:

Improvedevice functionalityVSAvoidbond strength

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The patent converts the harmful dangling bonds into beneficial stress-absorbing elements by intentionally creating controlled dangling bonds in buffer layers and dummy pads. These engineered dangling bonds absorb thermal stress and mechanical strain, preventing bond failure while maintaining structural integrity in multi-die packages.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces intermediary layers including buffer layers and dummy pads between bonded dies. These intermediary structures contain controlled dangling bonds that act as stress-absorbing mediators, protecting the actual bond interfaces from stress concentration and improving overall package reliability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If multiple device dies are bonded together to form complex package structures, then device functionality is improved, but stress and warpage increase affecting reliability

Engineering Contradiction:

Improvedevice functionalityVSAvoidpackage stress

Core Design Contradiction:

Adaptability or versatilityVSStress or pressure

Solution Approach 1:

The patent converts the harmful stress accumulation into a beneficial stress-management mechanism by creating controlled dangling bonds in buffer layers. These engineered defects absorb and distribute thermal stress and mechanical strain, preventing stress concentration at bond interfaces and reducing warpage in multi-die packages.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the physical and chemical parameters of intermediate layers by introducing controlled dangling bonds with specific density and distribution. This parameter modification allows the buffer layers to exhibit stress-absorbing properties, transforming them from potential failure points into protective elements that manage package stress.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If dangling bonds are present in bonded structures, then manufacturing complexity is reduced, but bond strength and reliability deteriorate

Engineering Contradiction:

Improvebonding process simplicityVSAvoidpackage reliability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent converts the typically harmful dangling bonds into beneficial stress-absorbing features. By intentionally creating controlled dangling bonds in buffer layers and dummy pads during manufacturing, the process maintains simplicity while the resulting structure gains enhanced stress management capabilities and improved reliability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the quality and distribution parameters of dangling bonds from random defects to controlled features. By adjusting the density, location, and characteristics of dangling bonds in intermediate layers, the manufacturing process produces structures with optimized stress-absorbing properties and improved package reliability.

Inventive Principle:

Principle #35Parameter changes

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 improves bond strength and reduces stress in the package, leading to enhanced reliability and performance by stabilizing the bond structure and minimizing warpage, thereby optimizing manufacturing efficiency and device functionality.

Implementation Method 1

enhancing bond strength and reducing stress through the use of stress-absorbing buffer layers and dielectric materials

Methodology Applied

Scientific EffectStress absorption: Elasticity

Implementation Method 2

employing fusion bonding techniques to improve the structural integrity of the package

Methodology Applied

Scientific EffectFusion bonding: Welding

Data Source

PatentUS20250364460A1Bonding structure of dies with dangling bonds

Publication Date: 2025.11.27 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A method includes polishing a semiconductor substrate of a first die to reveal first through-vias that extend into the semiconductor substrate, forming a dielectric layer on the semiconductor substrate, and forming a plurality of bond pads in the dielectric layer. The plurality of bond pads include active bond pads and dummy bond pads. The active bond pads are electrically coupled to the first through-vias. The first die is bonded to a second die, and both of the active bond pads and the dummy bond pads are bonded to corresponding bond pads in the second die.