MEMS Microphone Stacked Substrate Integration
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Solution Overview
Problem
Conventional methods for manufacturing MEMS microphones face challenges in integrating CMOS circuits and microphone structures on a single substrate, leading to complex processes, increased size, and high manufacturing costs due to differences in manufacturing processes and material limitations.
Innovation Solution
A method involving the bonding of substrates with conductive layers and sensitive electrodes to form a stacked structure, where a conductive plug is used to establish an electrical connection between the conductive layer and the sensitive electrode, avoiding additional conductive layers and allowing for flexible material selection and process temperatures, thus simplifying integration and reducing size and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the microphone structure and CMOS circuit are manufactured on a single substrate, then integration is improved, but the manufacturing process becomes complex and the device size increases
Solution Approach 1:
The patent divides the manufacturing process into two independent substrates: a first substrate for the microphone structure and a second substrate for the CMOS circuit. This segmentation allows each substrate to be manufactured using optimized processes for its specific requirements, avoiding the complexity of single-substrate integration while achieving functional integration through subsequent bonding.
Solution Approach 2:
The patent transitions from planar single-substrate integration to three-dimensional stacked substrate integration. By bonding the first substrate (microphone) and second substrate (CMOS circuit) in a stacked configuration, the patent achieves integration in the vertical dimension, reducing lateral footprint while maintaining process independence.
2Adaptability or versatility
If the microphone structure is manufactured before the CMOS circuit, then material selection flexibility is improved, but the substrate process affects CMOS circuit yield
Solution Approach 1:
By separating the microphone structure manufacturing (on first substrate) from the CMOS circuit manufacturing (on second substrate), the patent eliminates process interference. The first substrate can undergo aggressive processing for microphone structure formation without affecting CMOS yield, while the second substrate maintains dedicated CMOS fabrication conditions.
3Reliability
If the CMOS circuit is manufactured before the microphone structure, then CMOS circuit yield is improved, but material and process temperature selection for the microphone structure is limited
Solution Approach 1:
The patent separates the manufacturing sequences: the second substrate is dedicated to CMOS circuit fabrication with optimized yield, while the first substrate is dedicated to microphone structure formation with unrestricted material and process selection. This segmentation allows high-temperature or aggressive processes on the first substrate without compromising CMOS circuits.
4Ease of manufacture
If separate manufacturing processes are used for the microphone chip and CMOS circuit chip, then manufacturing flexibility is improved, but the device size increases
Solution Approach 1:
The patent merges the separately manufactured first substrate (microphone chip) and second substrate (CMOS circuit chip) into a single stacked assembly through bonding. This combining achieves functional integration and size reduction while preserving the manufacturing flexibility benefits of separate process optimization.
Solution Approach 2:
The patent stacks the two separately manufactured substrates in the vertical dimension, transitioning from lateral arrangement to vertical integration. This dimensional change reduces the lateral footprint and overall device size while maintaining the independence of manufacturing processes for each substrate.
Data Source
AI summary
A Micro-Electro-Mechanical System (MEMS) microphone and a method for forming the same are provided. The method includes: providing a first substrate including a first surface and a second surface opposite to each other; providing a second substrate including a third surface and a fourth surface opposite to each other; bonding the first surface of the first substrate and the third surface of the second substrate to each other; removing a second base of the second substrate to form a fifth surface opposite to the third surface of the second substrate; forming a cavity between the first substrate and the sensitive region of the second substrate; and forming a first conductive plug from the side of the fifth surface of the second substrate, with the first conductive plug passing through to at least one of the conductive layers.