Multi-layer Composite Backplate for MEMS Microphone
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Solution Overview
Problem
MEMS microphone systems face a challenge in achieving a balance between backplate strength and acoustic noise performance, as thick backplates provide robustness but reduce noise performance, while thin or highly perforated backplates lack strength and particle filtration efficiency.
Innovation Solution
A composite backplate construction using thin material layers with patterned web sections and strategically placed vent holes, incorporating interconnect layers of different metals or insulators, and varying layer widths to enhance strength and filtration while maintaining acoustic sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the backplate is made thick to provide robustness, then strength is improved, but acoustic noise performance deteriorates
Solution Approach 1:
The backplate is segmented into multiple thin layers (first backplate layer, second backplate layer, third backplate layer) rather than using a single thick plate. This segmentation allows each layer to contribute to overall strength while maintaining acoustic transparency, resolving the contradiction between strength and noise performance.
Solution Approach 2:
The invention uses a composite structure combining multiple materials (silicon nitride, silicon oxide, aluminum) in different layers. This composite approach provides enhanced mechanical strength equivalent to thicker plates while maintaining acoustic transparency, thus improving strength without deteriorating noise performance.
2Object-affected harmful factors
If the backplate is made thin or highly perforated to improve acoustic noise performance, then acoustic noise performance is improved, but strength deteriorates
Solution Approach 1:
The backplate is divided into multiple thin layers with controlled thickness (e.g., 50-200 nm per layer) rather than using a single thin plate. This segmentation distributes the mechanical load across layers, providing sufficient strength while maintaining acoustic transparency and enabling high particle filtration efficiency.
Solution Approach 2:
The composite structure using multiple materials (silicon nitride, silicon oxide, aluminum) provides enhanced mechanical properties that compensate for the thin overall thickness. This allows the backplate to be thin and highly perforated for acoustic performance while the composite nature provides the necessary strength.
3Object-affected harmful factors
If the backplate is made thin to improve particle filtration efficiency, then particle filtration efficiency is improved, but strength deteriorates
Solution Approach 1:
The backplate is segmented into multiple ultra-thin layers (total thickness 100-500 nm) with vent holes distributed across layers. This segmentation creates a tortuous path for particles while maintaining structural integrity through the multi-layer architecture, improving filtration efficiency without sacrificing strength.
Solution Approach 2:
The composite structure combining silicon nitride, silicon oxide, and aluminum provides enhanced mechanical strength that enables the use of ultra-thin layers for improved particle filtration. The different materials contribute varying mechanical properties that collectively provide sufficient strength despite the reduced overall thickness.
4Strength
If multiple layers are added to the backplate to improve strength, then strength is improved, but device complexity increases
Solution Approach 1:
Multiple functional layers (structural layers, vent hole layers, interconnect layers) are merged into a single integrated backplate structure formed through sequential deposition and patterning. This merging approach provides enhanced strength through multiple layers while avoiding the complexity of assembling separate components, as the entire structure is fabricated as one integrated unit.
Data Source
Figure 1
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Figure 3a~3b
AI summary
A MEMS device. The device includes a membrane, and a reinforced backplate having a plurality of openings. The reinforced backplate include a first layer, and a second layer coupled to the first layer.