MEMS Tethering Structures for Debris-Free Die Separation
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Solution Overview
Problem
Conventional dicing techniques for micro-electromechanical system (MEMS) devices are costly, complex, and generate debris, particularly in large-diameter wafers with small feature sizes and thin MEMS wafers, posing reliability concerns.
Innovation Solution
The use of tethering structures that suspend MEMS devices over a carrier wafer, allowing individual dies to be 'plucked' instead of being cut, eliminating the need for dicing and reducing debris generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional dicing techniques are used to separate MEMS devices from the wafer, then individual dies can be obtained, but debris is generated and reliability concerns arise
Solution Approach 1:
The patent divides the wafer into individual die regions separated by grooves, allowing each die to be independently accessed and removed without affecting others. This segmentation enables debris-free separation by eliminating the need for cutting through the entire wafer structure.
Solution Approach 2:
The patent extracts individual dies from the wafer by lifting them out through openings in the carrier substrate, rather than cutting them free. This extraction method removes the harmful cutting action that generates debris, while the tethering structures guide the removal process.
2Ease of manufacture
If conventional dicing techniques are used, then die separation is achieved, but the process becomes costly and complex
Solution Approach 1:
The patent performs preliminary actions during wafer fabrication by forming grooves and tethering structures before die separation is needed. These pre-formed features guide the subsequent simple lifting operation, eliminating the need for complex dicing equipment and procedures.
Solution Approach 2:
The patent introduces tethering structures as intermediaries between the die and carrier substrate. These tethers serve as temporary connectors that facilitate easy die removal through lifting, replacing the complex cutting mechanism with a simple mechanical separation process.
3Object-generated harmful factors
If tethering structures are used to suspend MEMS devices, then debris generation is reduced, but additional structural elements are required
Solution Approach 1:
The patent designs tethering structures that serve multiple functions: they provide mechanical support for suspending the die, guide the die during the lifting operation, and define the separation path. This multi-functionality reduces the need for additional separate components, offsetting the added structural complexity.
Solution Approach 2:
The patent merges the tethering structure with the carrier substrate and die support features into an integrated system. The grooves, tethers, and lifting openings work together as a unified mechanism, reducing the need for separate debris-collection systems or additional structural elements.
Data Source
AI summary
The present disclosure relates to a method for fabricating a micro-electromechanical system (MEMS) device. In the method, a carrier wafer is received. A MEMS wafer, which includes a plurality of die, is bonded to the carrier wafer. A cavity is formed to separate an upper surface of the carrier wafer from a lower surface of a die of the MEMS wafer. A separation trench is formed to laterally surround the die, wherein formation of the cavity and the separation trench leaves a tethering structure suspending the die over the upper surface of the carrier wafer. The die and carrier wafer are translated with respect to one another to break the tethering structure and separate the die from the carrier wafer.