Extended Seal Ring Structure for Wafer Stacking Interface Chipping
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Solution Overview
Problem
In wafer-to-wafer bonding, chipping at the die interface can occur during singulation, leading to humidity penetration and increased ohmic resistance, resulting in die rejection and failure, due to the lack of effective mechanical stress support and sealing at the bonding interface.
Innovation Solution
An extended seal ring structure is formed by metal-to-metal bonding, solder bump process, or through-silicon-via process, which spans the bonding interface between wafers, providing mechanical stress support and resisting humidity penetration by extending the seal ring up through the bonding interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional seal ring structures are used in wafer bonding, then the bonding process is simple, but mechanical stress support is insufficient leading to chipping and humidity penetration
Solution Approach 1:
The seal ring structure is extended vertically through the bonding interface by forming it in multiple layers (first seal ring layer in first substrate, second seal ring layer in second substrate connected via through-silicon vias). This three-dimensional configuration provides mechanical stress support across the bonding interface without significantly increasing lateral footprint, thereby preventing chipping and humidity penetration while maintaining process feasibility.
Solution Approach 2:
The extended seal ring structure embeds through-silicon vias within the seal ring layers, creating a nested configuration where conductive vias are surrounded by seal ring material. This nested design provides both mechanical reinforcement and electrical connectivity functions within a compact structure, enhancing bonding interface reliability without proportionally increasing overall complexity.
2Strength
If extended seal ring structure is formed through through-silicon-via process, then mechanical stress support is improved, but manufacturing process complexity increases
Solution Approach 1:
The seal ring structures and through-silicon vias are formed within substrates before the bonding process. This preliminary formation allows standard semiconductor fabrication processes to be used, and the structures are subsequently aligned and connected through wafer bonding. This approach leverages existing manufacturing capabilities rather than requiring new complex processes for the extended seal ring structure.
Solution Approach 2:
The wafer bonding process itself serves as an intermediary that connects the separately formed seal ring structures from first and second substrates. By using the bonding interface as the connection medium, the patent avoids the need for complex post-bonding alignment and connection processes, simplifying the overall manufacturing approach while achieving the extended seal ring configuration.
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 extended seal ring structure enhances mechanical stability, reduces chipping propagation, and prevents humidity penetration, thereby improving the reliability and robustness of the wafer-level bonds, while allowing for cost-effective and tolerant bonding processes.
Implementation Method 1
the first seal ring extension and the second seal ring extension are bonded together to form a continuous seal ring through the bonding interface between the first wafer and the second wafer
Data Source
AI summary
Embodiments include a wafer-on-wafer bonding where each wafer includes a seal ring structure around die areas defined in the wafer. Embodiments provide a further seal ring spanning the interface between the wafers. Embodiments may extend the existing seal rings of the wafers, provide an extended seal ring structure separate from the existing seal rings of the wafers, or combinations thereof.