Concentric Bump Alignment for 3D Die Stacking
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Solution Overview
Problem
In the formation of stacked dies for 3-D integrated circuits, the alignment and bonding processes are complex, particularly when multiple dies are stacked, leading to potential shifting and misalignment issues that can compromise the reliability of electrical connections.
Innovation Solution
The use of alignment bumps, which are non-solder metallic bumps forming rings around openings, are integrated with electrical connectors to prevent shifting and ensure accurate alignment during the stacking and bonding of dies, allowing for simultaneous formation with active bumps without additional cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple dies are stacked to form a die stack, then the footprint of packages is reduced and metal line routing is simplified, but the alignment and bonding processes become complex leading to potential shifting and misalignment issues
Solution Approach 1:
Alignment bumps are formed on the dies before the stacking process. These bumps serve as pre-established mechanical guides that ensure precise alignment when dies are stacked, preventing shifting and misalignment issues during the bonding process while enabling multi-die stacking to reduce package footprint
Solution Approach 2:
Alignment bumps act as intermediary mechanical features between the dies being stacked. These bumps engage with corresponding structures on adjacent dies to maintain precise relative positioning, serving as a mediator that ensures alignment precision is maintained throughout the multi-die stacking process
2Manufacturing precision
If alignment bumps are integrated with electrical connectors, then shifting is prevented and accurate alignment is ensured, but the device structure becomes more complex
Solution Approach 1:
Alignment bumps are merged with electrical connectors by forming both features simultaneously on the same die surfaces using the same bump formation process. This integration combines the alignment function and electrical connection function into unified structures, preventing shifting while maintaining relatively simple device architecture
Solution Approach 2:
The bumped structures serve multiple functions simultaneously: they provide mechanical alignment guidance during stacking and also serve as electrical connectors for signal and power transmission. This multi-functionality eliminates the need for separate alignment features, preventing shifting while avoiding additional structural complexity
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 alignment bumps effectively prevent undesirable shifting of overlying dies relative to underlying dies, ensuring reliable electrical connections and simplifying the bonding process by maintaining alignment without requiring extra steps or resources.
Implementation Method 1
solder regions/balls are reflowed to join the first die to the package substrate
Implementation Method 2
solder regions/balls are reflowed to join the second die to the first die
Implementation Method 3
The second underfill is then cured
Data Source
AI summary
An integrated circuit structure includes an alignment bump and an active electrical connector. The alignment bump includes a first non-solder metallic bump. The first non-solder metallic bump forms a ring encircling an opening therein. The active electrical connector includes a second non-solder metallic bump. A surface of the first non-solder metallic bump and a surface of the second non-solder metallic bump are substantially coplanar with each other.