MEMS Comb Electrode Release Etch for Stiction-Free Finger Tips
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Solution Overview
Problem
During the manufacturing of MEMS structures, fingers of comb structures can become stuck to the substrate due to variations in the etch process, leading to increased breakage during the finger release process, which can result in reduced sensitivity or non-operational devices.
Innovation Solution
A mask is used during the release etch process with larger openings near the bases of the fingers to promote more etching at the tips, ensuring that the tips are cleanly released from the substrate, reducing the likelihood of breakage and improving functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a uniform mask is used during the release etch process, then the etching is consistent across all finger regions, but the fingers may not be cleanly released from the substrate and can become stuck, leading to breakage during the release process
Solution Approach 1:
The mask is designed with non-uniform opening sizes where first openings near the finger bases are larger than second openings near the finger tips. This local variation in mask opening size creates different etching rates at different finger regions, ensuring that etching is more pronounced at the bases to promote clean release while maintaining sufficient support at the tips during the release process.
2Reliability
If the etch process is made more aggressive to ensure finger release, then fingers are more likely to be released from the substrate, but the fingers become more prone to breakage during the release process
Solution Approach 1:
By making the mask openings larger near the finger bases, the etching is intensified at the base regions where release is most needed, while the smaller openings near the tips provide mechanical support during the release process. This localized etching approach ensures complete release without causing excessive stress and breakage.
Solution Approach 2:
The mask is designed in advance with the understanding that larger openings are needed at the bases for release while smaller openings are needed at the tips for support. This preliminary design of the mask structure prevents breakage before the release process begins by establishing the proper support distribution.
3Reliability
If the mask openings are made larger to promote etching at the finger tips, then finger release is improved, but the bases may not be properly etched, causing fingers to remain stuck at the base regions
Solution Approach 1:
The mask is designed with larger openings specifically at the finger base regions and smaller openings at the finger tip regions. This ensures that etching is maximized at the bases where release is most critical, while the tips receive sufficient but not excessive etching, preventing both stuck bases and over-etched tips.
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 method enhances the cleanliness of finger release, minimizing breakage and improving manufacturing yield and device sensitivity by ensuring that the bases, rather than the tips, of the fingers remain attached to the substrate.
Implementation Method 1
A mask is used during the release etch process with larger openings near the bases of the fingers to promote more etching at the tips
Data Source
AI summary
An integrated circuit (IC) device includes: a first substrate; a dielectric layer disposed over the first substrate; and a second substrate disposed over the dielectric layer. The second substrate includes anchor regions comprising silicon extending upwards from the dielectric layer, and a series of interdigitated fingers extend from inner sidewalls of the anchor regions. The interdigitated fingers extend generally in parallel with one another in a first direction and have respective finger lengths that extend generally in the first direction. A plurality of peaks comprising silicon is disposed on the dielectric layer directly below the respective interdigitated fingers. The series of interdigitated fingers are cantilevered over the plurality of peaks. A first peak is disposed below a base of a finger and has a first height, and a second peak is disposed below a tip of the finger has a second height less than the first height.