MEMS Package Multi-Depth Trench Fabrication via Hard Mask
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Solution Overview
Problem
The integration of MEMS devices with different cavity depths on the same substrate poses challenges in fabrication due to the difficulty in forming and patterning photoresist masking layers on non-planar substrate surfaces, leading to insufficient coating and voids in deep trenches, especially when additional depth structures like movement stoppers or subscribe trenches are required.
Innovation Solution
A method involving a cap substrate with defined regions and trenches, where a hard mask is formed and patterned to expose and recess specific portions of the substrate, allowing for the formation of stoppers within trenches without using a photoresist masking layer, thereby reducing the aspect ratio of patterning openings and improving fabrication quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photoresist masking layers are used to form trenches of different depths, then the desired cavity depths can be achieved, but the fabrication process becomes complex and defective due to insufficient coating and voids in deep trenches
Solution Approach 1:
The patent divides the single complex patterning process into multiple simpler steps: forming initial trenches, depositing hard mask material, performing partial etching, and forming stoppers. This segmentation eliminates the need for complex photoresist masking in deep trenches while achieving precise different depths through controlled etching steps
Solution Approach 2:
The patent performs preliminary actions by forming the hard mask layer and patterning it before the final etching step. This preliminary patterning establishes the trench boundaries and stopper locations, allowing subsequent etching to proceed without requiring photoresist to remain in deep trenches, thus avoiding coating and void issues
2Adaptability or versatility
If additional depth structures like stoppers are formed in deep trenches, then device functionality is improved, but the aspect ratio of patterning openings increases making fabrication more difficult
Solution Approach 1:
The patent introduces a hard mask material as an intermediary that remains after photoresist removal. This hard mask serves as both the patterning definition and the stopper material, eliminating the need for high aspect ratio photoresist patterns while still enabling precise trench formation and stopper creation through controlled etching
Solution Approach 2:
The patent changes the physical and chemical parameters of the mask material by using deposited hard mask material instead of photoresist. This material has different etching resistance properties and can be patterned at lower aspect ratios, enabling the formation of stoppers and deep trenches with improved fabrication characteristics
Data Source
AI summary
The present disclosure relates to a MEMS package having different trench depths, and a method of fabricating the MEMS package. In some embodiments, a cap substrate is bonded to a device substrate. The cap substrate comprises a cap substrate bonded to a device substrate. The cap substrate comprises a MEMS trench, a scribe trench, and an edge trench respectively recessed from at a front-side surface of the cap substrate. A stopper is disposed within the MEMS trench and raised from a bottom surface of the MEMS trench.