Copper Pillar Bump Boosting Pads for Die-to-Die Coplanarity
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Solution Overview
Problem
In semiconductor fabrication, copper pillar bumps often exhibit height variations due to manufacturing tolerances and differences in bump density, leading to uneven coplanarity, which affects reliable connections in advanced packaging applications.
Innovation Solution
The introduction of boosting pads under shorter copper pillar bumps to raise their height within a tolerance threshold of taller bumps, ensuring consistent coplanarity through the selective boosting of conductive pillar bumps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If copper pillar bumps are manufactured using standard deposition processes, then manufacturing simplicity is maintained, but bump coplanarity deteriorates due to height variations from manufacturing tolerances and bump density differences
Solution Approach 1:
The patent applies local quality by introducing boosting pads only in specific regions where bump height is insufficient, rather than uniformly modifying all bumps. The boosting pads are selectively placed in high-density bump regions to raise those specific bumps to the target height, while low-density regions maintain their original bump structure. This localized modification approach improves overall coplanarity without unnecessarily complicating the entire manufacturing process.
Solution Approach 2:
The manufacturing process is segmented into multiple stages: initial copper deposition, density analysis, selective boosting pad deposition in high-density regions, and final copper deposition to complete the bumps. This segmentation allows different regions of the die to receive different treatments based on their bump density characteristics, enabling precise control of bump heights while maintaining process manageability.
2Reliability
If bump density is increased for high-performance computing applications, then connection capacity is improved, but coplanarity control becomes more difficult due to greater height variations
Solution Approach 1:
The patent implements preliminary action by performing density analysis and selective boosting pad deposition before the final copper bump formation. By identifying high-density regions early in the process and adding boosting pads at that stage, the method ensures that subsequent copper deposition will result in uniform bump heights across all regions, thereby maintaining coplanarity even as overall bump density increases for higher connection capacity.
Data Source
AI summary
Disclosed are techniques for selectively boosting conductive pillar bumps. In an aspect, an apparatus includes a plurality of metal pads, a first set of boosting pads attached to a first set of the plurality of metal pads, a first set of conductive pillar bumps attached to the first set of boosting pads, a second set of conductive pillar bumps attached to a second set of the plurality of metal pads, wherein heights of the first set of conductive pillar bumps are shorter than heights of the second set of conductive pillar bumps, and wherein heights of the first set of boosting pads plus the heights of the first set of conductive pillar bumps are within a tolerance threshold of the heights of the second set of conductive pillar bumps, and solder attached to the first set of conductive pillar bumps and the second set of conductive pillar bumps.