MEMS Device Fabrication with Segmented Opening Depths
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Solution Overview
Problem
Current MEMS device fabrication methods face challenges in exposing the photosensitive layer uniformly due to the etch loading effect during dry etching, leading to poor sensing ability and performance, especially when forming trenches with concave bottom surfaces.
Innovation Solution
The method involves forming a first substrate with varying depth openings in different regions, where the depth of first openings is larger than third openings, and using a patterned mask layer for dry etching to create a trench with a concave bottom surface, ensuring exposure of the photosensitive layer on all openings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a trench is formed by dry etching to expose the photosensitive layer, then the sensing ability should be improved, but the etch loading effect causes non-uniform exposure and poor performance
Solution Approach 1:
The patent segments the opening structure into two types: first openings in the peripheral region with larger depth and second openings in the central region with smaller depth. This segmentation allows different regions to be optimized independently, with the deeper peripheral openings compensating for the concave trench bottom surface while central openings provide uniform exposure. The segmented approach resolves the etch loading effect by distributing the exposure requirement across different opening types rather than relying on a single uniform opening structure.
2Ease of manufacture
If the depth of all openings is made equal, then the manufacturing process is simplified, but the photosensitive layer cannot be fully exposed due to the concave trench bottom surface
Solution Approach 1:
The patent applies local quality by assigning different depths to openings in different spatial locations. Peripheral openings have larger depth while central openings have smaller depth, matching the local requirements of each region. The deeper peripheral openings ensure complete exposure of the concave trench bottom surface in those regions, while central openings provide sufficient exposure for their location. This localized depth variation optimizes both manufacturing feasibility and exposure completeness without requiring uniform depth across all openings.
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 enhances the MEMS device's light sensing ability and electronic performance by ensuring complete exposure of the photosensitive layer, overcoming the etch loading effect and improving product yield.
Implementation Method 1
forming a trench in the first substrate by a dry etching process using the patterned mask layer as an etch mask
Implementation Method 2
forming a photosensitive layer on bottom and sidewall surfaces of the first openings and also on bottom and sidewall surfaces of the third openings
Data Source
AI summary
A method for fabricating an MEMS device includes providing a first substrate with a central region and a peripheral region, and forming a plurality of first openings in the peripheral region and a plurality of third openings in the central region by etching the first substrate from a front side. The depth of the first openings is larger than the depth of the third openings. The method further includes forming a photosensitive layer on the surfaces of the first openings and the third openings, bonding a second substrate to the front side of the first substrate, and forming a trench by etching the first substrate from a back side using a patterned mask layer as an etch mask. The trench has a concave bottom surface and exposes a portion of the photosensitive layer formed on the bottom surfaces of the first openings and the third openings.