Die Stack Alignment via TSV Recesses and Protrusions
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Solution Overview
Problem
The alignment of through-wafer vias in stacked semiconductor devices becomes increasingly challenging as the pitch and diameter decrease, affecting the electrical connectivity and yield of integrated circuits, particularly due to the limitations of existing alignment methods during the die stacking process.
Innovation Solution
The use of alignment recesses and protrusions on the dies, which are patterned and etched during the deep via patterning process, ensures precise alignment of through-wafer vias by engaging each other during the stacking process, thereby improving the accuracy and stability of the die stack without requiring additional processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through-wafer vias are used to interconnect stacked dies, then electrical connectivity and circuit density are improved, but alignment precision deteriorates due to the small diameter and high density of TSVs
Solution Approach 1:
The patent divides the alignment system into two distinct components: alignment protrusions on one die and alignment recesses on the mating die. This segmentation allows each component to be optimized independently while working together to achieve precise TSV alignment during die stacking, resolving the contradiction between maintaining electrical connectivity through TSVs and achieving the required alignment precision.
Solution Approach 2:
The alignment protrusions and recesses act as intermediary features that facilitate precise alignment between dies during stacking. These intermediary structures enable accurate positioning of small-diameter TSVs without requiring direct alignment of the TSVs themselves, thereby improving manufacturing precision while maintaining the electrical connectivity benefits of through-wafer vias.
2Device complexity
If die stacking is performed without alignment features, then device complexity is reduced, but manufacturing precision of through-wafer via alignment deteriorates
Solution Approach 1:
The patent merges the alignment function with the existing die stacking process by integrating alignment protrusions and recesses into the die structures themselves. This combination eliminates the need for separate alignment mechanisms or additional processing steps, maintaining device complexity at an acceptable level while significantly improving via alignment accuracy during stacking.
Solution Approach 2:
The alignment protrusions and recesses are formed during the deep via patterning process, which occurs before die stacking. This preliminary action ensures that alignment features are already in place when stacking occurs, enabling precise TSV alignment without adding complexity to the stacking process itself and maintaining high manufacturing precision.
3Manufacturing precision
If alignment recesses and protrusions are formed during deep via patterning, then manufacturing precision of alignment features is improved, but device complexity increases due to additional processing steps
Solution Approach 1:
The patent combines the formation of alignment features with the existing deep via patterning process. By merging these two operations into a single processing step, the method achieves high manufacturing precision for alignment features without adding separate processing steps, thereby avoiding increased device complexity while maintaining precise alignment feature formation.
Data Source
Figure 1
Figure 2A~2B
Figure 2C~2D
AI summary
A method is provided for forming a die stack. The method includes forming a plurality of through-wafer vias and a first plurality of alignment features in a first die. A second plurality of alignment features is formed in a second die, and the first die is stacked on the second die such that the first plurality of alignment features engage the second plurality of alignment features. A method of manufacturing a die stack is also provided that includes forming a plurality of through-wafer vias on a first die, forming a plurality of recesses on a first die, and forming a plurality of protrusions on a second die. A die stack and a system are also provided.