Die Bonding Structure With Dummy Pads for Dangling Bonds
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Solution Overview
Problem
The challenge in packaging integrated circuits with multiple device dies is the formation of complex structures that require improved bond strength and reduced stress to optimize device performance and manufacturing cost, particularly in bonding structures with dangling bonds.
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 dummy metal pads, and employing fusion bonding techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple device dies are packaged in the same package with upper memory dies bonded to lower memory dies, then manufacturing cost is saved and device performance is optimized, but bond strength is reduced and stress is increased due to dangling bonds
Solution Approach 1:
The patent introduces dummy pads as intermediary elements between the dangling pads of upper dies and the underlying structure. These dummy pads act as mediators that provide mechanical support and stress distribution, enabling the bonding of multiple dies while compensating for the weakness caused by dangling bonds. The dummy pads are formed in the dielectric layer and bonded to the dangling pads, creating a more robust bonding interface.
Solution Approach 2:
The bonding structure combines multiple materials including dielectric layers, metal pads, and buffer layers with different mechanical properties. The stress-absorbing buffer layer, positioned between the dummy pads and the underlying structure, is specifically designed with material properties that allow it to absorb and distribute stress, thereby enhancing the overall bond strength of the multi-die package.
2Reliability
If multiple device dies are packaged in the same package with upper memory dies bonded to lower memory dies, then device performance is optimized, but stress is increased in the package structure
Solution Approach 1:
The patent implements stress-absorbing buffer layers in advance within the bonding structure, before the actual bonding process. These buffer layers are positioned strategically between the dummy pads and the underlying structure to preemptively absorb and distribute the stress that will arise during operation, preventing stress concentration and potential failure in the multi-die package.
Solution Approach 2:
The dummy pads serve as intermediary elements that distribute and transfer stress away from the fragile dangling bonds. By bonding the dummy pads to the dangling pads and providing mechanical support, they act as stress-distributing mediators that reduce the overall stress in the package structure while maintaining device performance.
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 structure, leading to enhanced device performance and manufacturing efficiency by stabilizing dangling bonds and optimizing the package's integrity.
Implementation Method 1
bonded to a buffer layer, reducing stress and improving bond strength
Implementation Method 2
employing fusion bonding techniques
Data Source
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.