MEMS Stress Decoupling via Front-Side Blind Trenches
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Solution Overview
Problem
Conventional stress decoupling structures in MEMS elements, such as deep trenches in the substrate, are prone to particle contamination, require precise depth definition, and are costly to manufacture, leading to ineffective stress decoupling and increased stress input into the MEMS structure.
Innovation Solution
A blind hole-like trench structure is implemented in the MEMS substrate, open towards the space between the layered structure and the substrate, extending only to a predefined depth with a closed rear side, providing reliable stress and vibration decoupling by positioning the trenches under the functional element or offset from it, and using a ratio of web width to trench depth for decoupling properties independent of substrate thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If deep trenches are applied in the rear side of the substrate for stress decoupling, then stress decoupling effect is improved, but particle contamination occurs and manufacturing complexity increases
Solution Approach 1:
The patent inverts the conventional approach by forming trenches from the front side of the substrate instead of the rear side. The trenches extend through the substrate thickness and are open only at the front side, allowing stress decoupling while preventing particle collection that would occur in rear-side trenches during subsequent processing steps.
Solution Approach 2:
The substrate is segmented by creating trenches that divide the continuous substrate structure. These trenches create isolated regions that can independently absorb stress deformations, improving the overall stress decoupling effect while the open-front design prevents particle accumulation.
2Reliability
If trench depth is precisely defined to achieve effective stress decoupling, then stress decoupling reliability is improved, but manufacturing complexity and cost increase
Solution Approach 1:
By inverting the trench formation approach and creating trenches from the front side with openings only at the front, the patent eliminates the need for precise depth control relative to substrate thickness. The trenches can extend fully through the substrate, simplifying the manufacturing process while maintaining effective stress decoupling.
3Object-affected harmful factors
If trenches are filled with elastic material to prevent particle introduction, then particle contamination is reduced, but stress decoupling effect is significantly limited
Solution Approach 1:
The patent avoids the need to fill trenches with elastic material by inverting the trench design - trenches are open only at the front side and extend through the substrate. This design inherently prevents particle collection during processing while maintaining the trenches' stress-absorbing functionality, eliminating the trade-off between particle protection and stress decoupling.
Data Source
AI summary
Measures are described which contribute simply and reliably to the mechanical decoupling of a MEMS functional element from the structure of a MEMS element. The MEMS element includes at least one deflectable functional element, which is implemented in a layered structure on a MEMS substrate, so that a space exists between the layered structure and the MEMS substrate, at least in the area of the functional element. According to the invention, a stress decoupling structure is formed in the MEMS substrate in the form of a blind hole-like trench structure, which is open to the space between the layered structure and the MEMS substrate and extends into the MEMS substrate to only a predefined depth, so that the rear side of the MEMS substrate is closed, at least in the area of the trench structure.