Polysilicon Bridge Sealing for MEMS Vacuum Cavities
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Solution Overview
Problem
The existing methods for forming polysilicon sealed vacuum cavities in micro-electro-mechanical systems (MEMS) are complex and lack reliability, requiring additional materials and processes that complicate the sealing and packaging of MEMS devices.
Innovation Solution
A method involving the formation of a cap element on a substrate, creating a gap by removing material, and rearranging material to merge the cap element and substrate, forming a bridge element that seals the gap without the need for additional materials, using thermal annealing in a hydrogen atmosphere to promote silicon migration and closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysilicon sealed vacuum cavities are formed using conventional methods, then sealing is achieved, but the process becomes complex and reliability decreases
Solution Approach 1:
The patent merges the cap element and substrate by forming a bridge structure that integrates them into a single sealed unit. The bridge element connects the cap to the substrate, eliminating the need for separate sealing processes and reducing overall device complexity while improving sealing reliability.
Solution Approach 2:
The bridge element serves as an intermediary structure between the cap element and substrate. This intermediate component facilitates the connection and sealing process, providing a reliable seal while simplifying the overall manufacturing process by acting as a mediator that integrates the two main components.
2Reliability
If additional materials are used for sealing, then sealing can be achieved, but the process complexity and cost increase
Solution Approach 1:
The bridge element is formed from the same polysilicon material as the cap element and substrate, maintaining material homogeneity throughout the structure. This eliminates the need for additional sealing materials and reduces overall material quantity while ensuring consistent material properties throughout the sealed cavity.
Solution Approach 2:
The bridge element is formed in-situ from the existing polysilicon material through selective removal and reformation processes. The structure essentially creates its own sealing mechanism using its own material, eliminating the need for external sealing materials and reducing process complexity.
3Ease of manufacture
If conventional sealing methods are used, then sealing is achieved, but additional processes and materials are required
Solution Approach 1:
The bridge element is formed during the initial polysilicon deposition and patterning processes, before the final assembly steps. By preparing the bridge structure in advance as part of the cap element fabrication, the sealing process is simplified and integrated into the existing manufacturing flow without requiring additional complex steps.
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 approach simplifies the sealing process, enhances the reliability and robustness of MEMS devices by forming a stable connection between the cap and substrate, protecting functional components from mechanical, electrical, and chemical influences, and is compatible with front-end CMOS processing, reducing costs and complexity.
Implementation Method 1
thermal annealing in a hydrogen atmosphere to promote silicon migration and closure
Implementation Method 2
thermal annealing in a hydrogen atmosphere to promote silicon migration and closure
Data Source
AI summary
A method of manufacturing a structure (1100), the method comprising forming a cap element (401) on a substrate (101), removing material (103) of the substrate (101) below the cap element (401) to thereby form a gap (802) between the cap element (401) and the substrate (101), and rearranging material of the cap element (401) and/or of the substrate (101) to thereby merge the cap element (401) and the substrate (101) to bridge the gap (802).