Seal Ring Bonding Structures With Stoppers For MEMS
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Solution Overview
Problem
In the fabrication of MEMS sensors, the eutectic bond material used for sealing can excessively flow out of the seal ring region, causing electrical shorts with sensitive structures, and existing designs that attempt to manage this often compromise alignment accuracy between wafers due to inadequate gap width control.
Innovation Solution
The introduction of stoppers or tabs within the channel of the seal ring structure, which narrow the gap and direct the eutectic encapsulation bonding material to a wider channel portion, preventing overflow and enhancing alignment accuracy by maintaining a smaller gap dimension than typical tool performance allows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seal ring channel gap width is increased to prevent eutectic bond material overflow, then the risk of electrical shorts is reduced, but the alignment accuracy between wafers deteriorates
Solution Approach 1:
The channel gap is segmented into two distinct regions: a first region with a larger gap width to accommodate eutectic bond material overflow, and a second region with a smaller gap width to maintain alignment accuracy. This segmentation allows each region to serve its specific function without compromising the other.
Solution Approach 2:
Different gap widths are applied to different portions of the channel based on local requirements. The first portion has a larger gap where overflow is expected, while the second portion has a smaller gap where precision alignment is critical. This local differentiation resolves the contradiction by matching gap width to functional needs.
2Manufacturing precision
If the seal ring channel gap width is decreased to improve alignment accuracy, then the alignment precision between wafers is improved, but the eutectic bond material flows excessively causing electrical shorts
Solution Approach 1:
The channel is divided into functional segments with different gap characteristics. The first region provides overflow accommodation with larger gap, while the second region provides precision alignment with smaller gap, preventing electrical shorts while maintaining alignment accuracy.
Solution Approach 2:
The gap width is optimized locally for each channel region: larger gap in the overflow-prone first portion and smaller gap in the alignment-critical second portion, thereby simultaneously preventing shorts and ensuring precision.
3Ease of manufacture
If uniform gap width is used throughout the channel, then the manufacturing process is simplified, but the eutectic bond material either overflows causing shorts or alignment accuracy is compromised
Solution Approach 1:
Rather than using a uniform gap, the channel is segmented into regions with different gap widths optimized for their specific functions. This segmentation, while adding some manufacturing complexity, is achieved through standard lithographic patterning and resolves the reliability issues that would otherwise require even more complex manufacturing solutions.
Solution Approach 2:
The channel gap is designed with local quality variations to match the different functional requirements of different regions, achieving reliable operation without excessive manufacturing 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
This solution effectively prevents electrical shorts by controlling the flow of eutectic bonding material and improves alignment accuracy between wafers, meeting product accuracy requirements despite the limitations of typical tool performance.
Implementation Method 1
bonded to the first wafer with eutectic bonding materials
Data Source
AI summary
The present disclosure relates to semiconductor structures and, more particularly, to seal ring structures with channels and methods of manufacture. The structure includes: a first wafer having a channel formed within a passivation layer; a second wafer having a protuberance which is insertable into the channel and which is bonded to the first wafer with eutectic bonding materials; and a plurality of stoppers or tabs extending within the channel and which provides a gap that has a dimension smaller than a gap formed in other portions of the channel.