Nano-twinned Copper Coating for Direct Bonding Interconnects
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Solution Overview
Problem
The increasing device density and decreasing device dimensions in semiconductor technology lead to brittle solder joints due to intermetallic compound formation, affecting the quality of interconnects in semiconductor packages, which existing packaging techniques fail to adequately address.
Innovation Solution
A direct-bonding semiconductor structure utilizing nano-twinned metal contact areas with a bond enhancement layer, where nano-twinned copper coating layers on substrates form a direct bonding interface, potentially eliminating the need for solder and enhancing interconnect reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder is used for interconnection in semiconductor packages, then electrical connection is achieved, but the solder joints become brittle due to intermetallic compound formation
Solution Approach 1:
The patent removes solder entirely from the interconnection process, extracting the harmful element that causes brittleness. Instead of using solder joints, the invention employs direct Cu-to-Cu bonding between microbumps, eliminating the source of intermetallic compound formation and associated reliability issues.
Solution Approach 2:
The patent introduces a nano-twinned metal coating layer as an intermediary between the Cu microbumps and the bonding interface. This nanotwinned copper layer serves as a mediator that enables direct bonding while preventing intermetallic compound formation, thus maintaining connection quality without the brittleness problems of solder joints.
2Productivity
If microbump size is reduced to increase device density, then more devices can be packed, but the amount of solder decreases resulting in increased brittleness
Solution Approach 1:
The patent extracts solder from the interconnection system entirely, replacing it with direct Cu-to-Cu bonding. This elimination allows microbumps to be scaled down to finer pitches without the constraint of maintaining sufficient solder volume, enabling higher device density without compromising joint reliability.
Solution Approach 2:
The patent changes the material parameters at the bonding interface by using nanotwinned copper coating with specific crystallographic orientation ((111) orientation). This parameter change in material structure enables reliable bonding at reduced microbump sizes where traditional solder would become too brittle.
3Reliability
If direct Cu-to-Cu bonding is used for fine-pitch microbumps, then solder brittleness is avoided, but bonding interface quality must be precisely controlled
Solution Approach 1:
The patent applies preliminary action by pre-coating the Cu microbumps with a nanotwinned copper layer before bonding. This preliminary coating step ensures that when the microbumps are bonded directly together, the interface already has the optimal crystallographic structure ((111) orientation) and nanotwinned morphology needed for high-quality bonding, reducing the precision requirements during the actual bonding process.
Solution Approach 2:
The patent changes the material parameters of the bonding interface by creating a nanotwinned copper coating with controlled grain size and (111) crystallographic orientation. This parameter transformation from conventional copper to nanotwinned copper with specific orientation simplifies the bonding process and improves interface quality, making it more robust against manufacturing variations.
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 solution provides a robust and reliable interconnect by creating a large nano-twin metal contact area, enhancing the bonding strength and reducing brittleness, thus improving the quality of semiconductor package interconnects.
Implementation Method 1
The first contact structure is connected with the second contact structure, thereby constituting a bonding interface directly between the first nano-twinned metal coating layer and the second nano-twinned metal coating layer
Data Source
AI summary
A semiconductor structure includes a first substrate including a first contact structure located on a first pad, and a second substrate including a second contact structure on a second pad. The first contact structure includes a first metal base layer covered by a first nano-twinned metal coating layer. The second contact structure includes a second nano-twinned metal coating layer on the second pad. The first contact structure is connected to the second contact structure, thereby forming a bonding interface between the first nano-twinned metal coating layer and the second nano-twinned metal coating layer.