MEMS Acoustic Transducer Nested Cavity Design
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Solution Overview
Problem
The challenge in developing MEMS acoustic transducers is to increase sensitivity while reducing production costs and addressing the complexity of the fabrication process, particularly in optimizing the volume of the back cavity and preventing sticking issues between the membrane and backplate.
Innovation Solution
The solution involves a MEMS acoustic transducer design with a substrate having a first opening area and a lower electrode layer, a MEMS chip with a second opening area and an upper electrode layer forming an induction capacitor, and a housing creating a cavity with the MEMS chip or substrate, allowing for adjustable vertical gaps and improved fabrication processes such as CMOS integration and conductive glue usage to enhance sensitivity and reduce thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the volume of the back cavity is increased to improve sensitivity, then the sensitivity is improved, but the total volume of the transducer increases
Solution Approach 1:
The patent places the MEMS chip inside the housing cavity, and further integrates the induction capacitor structure within the MEMS chip itself. The back cavity is formed by the housing enclosing the MEMS chip, creating a nested arrangement where smaller components are placed within larger structures. This nesting allows the back cavity volume to be optimized for sensitivity while the entire transducer maintains a compact footprint suitable for mobile devices.
2Length of moving object
If the membrane and backplate are made thinner to reduce thickness, then the thickness is reduced, but sticking issues occur between the membrane and backplate
Solution Approach 1:
The patent introduces an intermediary structure between the membrane (upper electrode layer) and backplate (lower electrode layer) in the form of the induction capacitor configuration. The upper electrode layer partially seals the second opening area and forms a capacitor with the lower electrode layer, creating an electromagnetic field-based interaction that provides flexibility and prevents direct mechanical contact. This intermediary capacitor structure eliminates the sticking issue while maintaining thin profile.
3Ease of manufacture
If the fabrication process is simplified to reduce production costs, then the production cost is reduced, but the sensitivity and performance may be compromised
Solution Approach 1:
The patent combines multiple functions into integrated structures: the induction capacitor is formed by integrating the upper electrode layer on the MEMS chip with the lower electrode layer on the substrate; the back cavity is formed by the housing enclosing the MEMS chip; the sound opening is created by aligning the first and second opening areas. These merged structures reduce the number of separate components and assembly steps, lowering production costs while maintaining the sensitivity performance through optimized electromagnetic field configuration.
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 design enhances sensitivity, reduces the total volume of the transducer, and simplifies the fabrication process, aligning with the trend of making devices lighter and thinner while maintaining high performance.
Implementation Method 1
both the ECM and the MEMS acoustic transducers detect sound by sensing the capacitance variation produced by acoustic pressure
Implementation Method 2
sensing the capacitance variation produced by acoustic pressure
Data Source
AI summary
A MEMS acoustic transducer is provided, which includes a substrate, a MEMS chip, and a housing. The substrate has a first opening area and a lower electrode layer disposed over a surface of the substrate, wherein the first opening area includes at least one hole allowing acoustic pressure to enter the MEMS acoustic transducer. The MEMS chip is disposed over the surface of the substrate, including a second opening area and an upper electrode layer partially sealing the second opening area, wherein the upper electrode layer and the lower electrode layer, which are parallel to each other and have a gap therebetween, form an induction capacitor. The housing is disposed over the MEMS chip or the surface of the substrate creating a cavity with the MEMS chip or the substrate. In addition, a method for fabricating the above MEMS acoustic transducer is also provided.