MEMS Comb Electrode Release Mask for Clean Finger Tip Separation
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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 potential 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 device functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standard release etch process is used, then the etching is uniform across the structure, but the fingers become stuck to the substrate due to etch variations, leading to breakage during release
Solution Approach 1:
The mask structure implements local quality by providing different opening sizes at different locations: larger openings near finger bases and smaller openings near finger tips. This non-uniform mask design creates localized etching variations that ensure complete release at critical areas while maintaining overall process control, resolving the contradiction between etch uniformity and release reliability.
Solution Approach 2:
The mask is applied beforehand to strategically control where etching occurs most aggressively. By pre-positioning larger openings at finger bases and smaller openings at tips, the process prepares the structure for complete release before the actual release attempt, preventing stuck fingers and subsequent breakage during the release process.
2Ease of manufacture
If etching is performed uniformly across all areas, then the process is simple to control, but finger tips may remain attached to the substrate, reducing device sensitivity or functionality
Solution Approach 1:
The mask introduces local quality variations with different opening sizes at different finger locations. This ensures that etching is more aggressive where needed (at finger bases) while maintaining simpler overall process control, achieving complete finger release without compromising manufacturing ease.
3Strength
If the finger tips remain attached to the substrate, then the structure maintains structural integrity, but device sensitivity is reduced or the device becomes non-operational
Solution Approach 1:
The mask creates local quality differences in etching intensity, with larger openings at finger bases providing more aggressive etching to ensure complete release. This targeted approach maintains structural integrity during processing while ensuring tips are cleanly released for proper device functionality, resolving the contradiction between strength and reliability.
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.