Copper Bonding Pads With Electrochemical Barrier Layers for Low-Cavity Bonding
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Solution Overview
Problem
The process reliability and yield of copper-to-copper bonding between mating pairs of copper pads become challenging as the dimensions of the copper pads decrease in advanced semiconductor technology generations, necessitating a solution to improve bonding by reducing cavities between these pads.
Innovation Solution
A bonded assembly is formed using semiconductor dies with copper bonding pads that incorporate conductive barrier layers with specific electrochemical potentials, where one layer has a higher potential than copper and the other has a lower potential, facilitating copper-to-copper bonding by inducing bonding between copper material portions laterally surrounded by these barrier layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If copper pad dimensions are reduced to enable advanced semiconductor technology generations, then device integration density is improved, but copper-to-copper bonding reliability deteriorates due to increased cavity formation
Solution Approach 1:
The patent applies different conductive barrier materials with specific electrochemical potentials to different locations in the bonding structure. One copper pad uses a barrier material with higher electrochemical potential while the mating pad uses a barrier material with lower electrochemical potential, creating localized chemical properties that promote reliable bonding despite reduced pad dimensions
Solution Approach 2:
The patent changes the electrochemical potential parameter of the conductive barrier layers by selecting materials with different potentials relative to copper. This parameter change creates a chemical driving force that facilitates copper-to-copper bonding and reduces cavity formation, enabling reliable bonding at smaller pad dimensions
2Manufacturing precision
If copper pad dimensions are reduced, then manufacturing precision requirements increase, but bonding yield deteriorates due to cavity formation between pads
Solution Approach 1:
The patent converts the potential harm of reduced pad dimensions (which leads to bonding difficulties and low yield) into a benefit by introducing conductive barrier layers with different electrochemical potentials. This chemical approach compensates for the dimensional reduction, enabling high bonding yield despite smaller pad sizes and stricter precision requirements
3Productivity
If conductive barrier layers with different electrochemical potentials are used, then copper bonding yield is improved, but device complexity increases
Solution Approach 1:
The patent segments the conductive barrier layer into two distinct components: one with higher electrochemical potential and one with lower electrochemical potential relative to copper. This segmentation allows each barrier layer to perform its specific function in promoting bonding, achieving high bonding yield while maintaining a relatively simple overall structure that integrates seamlessly with existing semiconductor manufacturing processes
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 enhances the copper bonding yield and reliability by ensuring effective bonding between copper pads, addressing the challenges posed by reduced pad dimensions in advanced semiconductor technologies.
Implementation Method 1
the first bonding pad comprises a first copper material portion and a first conductive barrier layer comprising a first conductive barrier material having a higher electrochemical potential than copper located between the first semiconductor devices and the first copper material portion
Implementation Method 2
the second bonding pad comprises a second copper material portion and a second conductive barrier layer comprising a second conductive barrier material having a lower electrochemical potential than copper located between the second semiconductor devices and the second copper material portion
Data Source
AI summary
Bonding strength and yield can be enhanced by providing a mating pair of a convex bonding surface and a concave bonding surface. The convex bonding surface can be provided by employing a conductive barrier layer having a higher electrochemical potential than copper. The concave bonding surface can be provided by employing a conductive barrier layer having a lower electrochemical potential than copper. Alternatively additionally, a copper material portion in a bonding pad may include at least 10% volume fraction of (200) copper grains to provide high volume expansion toward a mating copper material portion. The mating copper material portion may be formed with at least 95% volume fraction of (111) copper grains to provide high surface diffusivity, or may be formed with at least 10% volume fraction of (200) copper grains to provide high volume expansion.