Thin Substrate Microphone With Backside Recess
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Solution Overview
Problem
Conventional MEMS microphones are limited by the thickness of their substrate, which affects signal-to-noise ratio and manufacturing complexity, as thinner substrates are more sensitive to mechanical influences during production.
Innovation Solution
A method involving a substrate with a recess formed on the backside, allowing for the creation of thin microphone structures with cavities, processed to form separate microphone structures, enabling a thin substrate and improved signal-to-noise ratio while simplifying and cost-saving manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the substrate thickness is reduced to improve signal-to-noise ratio, then the back volume behind the microphone increases, but the substrate becomes more sensitive to external mechanical influences during production and assembly
Solution Approach 1:
The patent applies local quality by creating a recess structure in the substrate that provides mechanical support specifically at the microphone location. The recess has a bottom surface that extends into the substrate, creating a localized thickened region that reinforces the area around the microphone while maintaining thin overall substrate thickness. This resolves the contradiction by providing mechanical stability where needed without preventing the overall substrate from being thin enough to achieve good signal-to-noise ratio.
2Length of moving object
If the substrate thickness is reduced to achieve thinner microphone structures, then space is saved in devices, but the handling of the substrate becomes more difficult during production
Solution Approach 1:
The recess structure creates localized thickness variation in the substrate. The substrate remains thin overall (improving device integration) but has a thickened region at the recess bottom that provides mechanical strength during handling and processing. This local reinforcement allows the substrate to be thin for space savings while maintaining ease of manufacture through improved mechanical properties at critical locations.
3Ease of manufacture
If a thick substrate is used to improve handling during production, then mechanical stability is achieved, but the back volume behind the microphone becomes small leading to low signal-to-noise ratio
Solution Approach 1:
The patent solves the contradiction by transitioning from a uniform thickness problem to a three-dimensional recess structure. Instead of choosing between thick or thin uniform substrates, the invention creates a recess that extends vertically into the substrate, forming a localized thickened region. This dimensional approach allows the substrate to provide mechanical stability (like a thick substrate) while maintaining thin overall profile (like a thin substrate), thereby achieving both good handling and high signal-to-noise ratio.
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 results in microphones with enhanced signal-to-noise ratio and cost-effective production, suitable for space-constrained devices like mobile communication devices, by forming thin substrates and utilizing wet chemical etching for cavity creation.
Implementation Method 1
forming a plurality of cavities into a bottom of the recess with each cavity of the plurality of cavities being formed in one of the microphone areas
Data Source
AI summary
In various embodiments, a method for manufacturing microphone structures is provided. The method may include: Providing a substrate having a front side and a back side, the backside facing away from the front side, and having an inner area and an outer area laterally surrounding the inner area, with the inner area comprising a plurality of microphone areas each microphone are being provided for one microphone of the plurality of microphones; Forming a plurality of layers for the plurality of microphones in the microphone areas on the front side of the substrate; Forming a recess from the backside of the substrate with the recess laterally overlapping the entire inner area; Forming a plurality of cavities into a bottom of the recess with each cavity of the plurality of cavities being formed in one of the microphone areas; Processing the layers to form the plurality of microphone structures, wherein each microphone structure comprises at least one layer of the plurality of layers and one cavity; and Separating the plurality of microphone structures from each other.