MEMS Audio TSV Structure for Foundry-Compatible Speaker Integration
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Solution Overview
Problem
Conventional speakers and microphones are incompatible with semiconductor manufacturing processes, limiting their integration in consumer devices and posing challenges due to magnetic interference and size constraints.
Innovation Solution
A foundry-compatible process is developed for fabricating MEMS speakers and microphones, utilizing silicon-based components and CMOS technology, allowing integration on a common substrate with vent regions and movable diaphragms, and employing etching and bonding techniques to create integrated audio devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional speaker technology with permanent magnets and moving coils is used, then audio signal conversion is achieved, but compatibility with semiconductor manufacturing processes is lost and device size is increased
Solution Approach 1:
The patent replaces the conventional electromagnetic actuation system (permanent magnets, moving coils) with a purely mechanical MEMS structure actuated by electrostatic forces. The speaker diaphragm is suspended over a cavity with vent holes, and actuation is achieved through electrostatic attraction between the diaphragm and a backplate, eliminating all magnetic components and enabling compatibility with standard CMOS semiconductor manufacturing processes
Solution Approach 2:
The patent extracts and removes the magnetic components (permanent magnets, ferromagnetic materials) from the speaker structure, retaining only the essential acoustic conversion function. This extraction allows the speaker to be fabricated using non-magnetic semiconductor materials and processes, resolving the contradiction between manufacturing compatibility and functional performance
2Object-affected harmful factors
If conventional speaker technology with permanent magnets is used, then audio signal conversion is achieved, but interference with magnetic sensors and other components occurs
Solution Approach 1:
The patent substitutes the electromagnetic actuation mechanism with an electrostatic-mechanical system. The speaker diaphragm is actuated by electrostatic forces between charged plates, completely eliminating permanent magnets and ferromagnetic materials. This substitution removes the source of magnetic interference, allowing the speaker to coexist with magnetic sensors and other magnetic-sensitive components in smartphones and wearables
3Volume of moving object
If speaker size is reduced to fit mobile devices, then device integration is improved, but conventional speaker technology constraints limit placement options
Solution Approach 1:
The patent transitions from planar speaker designs to a three-dimensional vertical cavity structure. The speaker diaphragm is suspended over a deep cavity etched into the substrate, with vent holes providing acoustic access. This vertical configuration allows the speaker to be integrated into the thickness dimension of mobile devices, maximizing placement flexibility while maintaining acoustic performance in extremely compact form factors
Solution Approach 2:
The patent nests the speaker cavity within the substrate thickness, embedding the acoustic chamber inside the device structure rather than adding external volume. The cavity is etched through the substrate, and the diaphragm is suspended within this nested space, allowing the speaker to occupy minimal external footprint while providing sufficient acoustic volume for effective operation
4Device complexity
If micro-speaker and microphone are integrated on common substrate, then device miniaturization is achieved, but manufacturing process compatibility must be maintained
Solution Approach 1:
The patent designs a universal MEMS fabrication process that can fabricate both micro-speakers and microphones using the same sequence of steps on a common substrate. The process uses standard CMOS-compatible materials and techniques (suspension bridge structures, deep reactive ion etching, electrostatic actuation) that can produce either acoustic output device depending on the specific device configuration, enabling monolithic integration without requiring separate manufacturing lines
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
Enables the miniaturization of audio components without performance loss, facilitating their integration in devices like earbuds, smartwatches, and smartphones, and supporting wide-scale commercialization using conventional semiconductor and MEMS processes.
Implementation Method 1
a movable diaphragm device comprising a thickness of silicon material having a thickness 0.1 nm to ten microns, and configured spatially in an elongated manner within the cavity region
Implementation Method 2
The device has a CMOS (i.e., Complementary metal-oxide-semiconductor) device coupled to the cap device
Data Source
AI summary
A MEMS audio device includes a first wafer having a top with a first cavity and a bottom with a vent hole coupled to the first cavity, wherein the bottom having first contacts, a second wafer disposed upon the first wafer having a flexible material layer disposed above the first cavity, a third wafer disposed upon the second wafer having physical contacts coupled to the second wafer, wherein the third wafer includes a second cavity disposed above the flexible material layer, a wiring wafer disposed below the first wafer having a second vent hole coupled to the first cavity, wherein the wiring wafer having second contacts coupled to the first contacts, and wherein the flexible material layer forms a diaphragm for the MEMS audio device.