MEMS Microphone Protection Post Reduces Stress Concentration

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Solution Overview

Problem

Existing MEMS microphones face issues with diaphragm damage due to large deformation under air pressure, leading to potential cracks in the sensor.

Innovation Solution

The proposed MEMS structure includes a protection post structure extending from the backplate into the air gap, which reduces stress concentration around the pillar structure and prevents diaphragm damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the diaphragm is made thin and flexible to improve acoustic sensitivity, then the acoustic pressure response is improved, but the diaphragm suffers large deformation under air pressure causing sensor cracks

Engineering Contradiction:

Improveacoustic sensitivityVSAvoiddiaphragm integrity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The support structure is segmented into multiple components: a central pillar structure for mechanical support and electrical connection, and surrounding protection post structures that segment the stress distribution area. This segmentation allows the diaphragm to be thin and flexible while distributing the stress away from the sensor region.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The protection post structures act as intermediary elements between the diaphragm and the air pressure load. These posts intercept and redirect the stress caused by diaphragm deformation, preventing direct transmission of stress to the sensor and eliminating the need to thicken the diaphragm for strength.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If the diaphragm is made thick and rigid to prevent deformation damage, then the diaphragm strength is improved, but the acoustic sensitivity and measurement precision deteriorate

Engineering Contradiction:

Improvediaphragm strengthVSAvoidacoustic sensitivity

Core Design Contradiction:

StrengthVSMeasurement precision

Solution Approach 1:

The protection post structures serve as intermediary stress-bearing elements that allow the diaphragm to remain thin and flexible. The posts intercept the mechanical stress from air pressure deformation, enabling the diaphragm to maintain high acoustic sensitivity while the overall structure achieves sufficient strength through the support posts.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The mechanical strength function is substituted from the diaphragm material itself to the separate protection post structures. This allows the diaphragm to be optimized purely for acoustic sensitivity (thin and flexible) while the protection posts provide the necessary mechanical strength and stress management.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Stability of the object's composition

If the pillar structure is enlarged to improve structural stability, then the support stability is improved, but the stress concentration around the pillar increases causing diaphragm damage

Engineering Contradiction:

Improvestructural stabilityVSAvoidstress concentration

Core Design Contradiction:

Stability of the object's compositionVSStress or pressure

Solution Approach 1:

The support function is segmented between the central pillar structure (providing mechanical stability and electrical connection) and the surrounding protection post structures (providing stress distribution). This segmentation allows the pillar to remain compact while the protection posts handle the stress concentration issue by distributing forces across a larger area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The stress distribution is extended from the single-dimensional pillar structure to a two-dimensional arrangement by adding protection posts in the radial direction around the pillar. This dimensional expansion distributes the stress over a larger area, reducing stress concentration at the pillar-diaphragm interface while maintaining structural stability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 protection post structure effectively reduces stress concentration by more than 40%, thereby preventing diaphragm damage and enhancing the reliability of MEMS microphones.

Implementation Method 1

the protection post structure may reduce the stress concentration around the pillar structure caused by the deformation of the diaphragm

Methodology Applied

Scientific EffectStress concentration reduction:

Implementation Method 2

variations in acoustic pressure force the diaphragm to deform correspondingly, and the deformation of the diaphragm changes the air gap, which induces a capacitance variation

Methodology Applied

Scientific EffectCapacitance variation: Capacitance

Data Source

PatentUS12207052B2MEMS structure

Publication Date: 2025.01.21 FORTEMEDIA INC

AI summary

A MEMS structure is provided. The MEMS structure includes a substrate having an opening portion and a backplate disposed on one side of the substrate. The MEMS structure also includes a diaphragm disposed between the substrate and the backplate. The opening portion of the substrate is under the diaphragm, and an air gap is formed between the diaphragm and the backplate. The MEMS structure further includes a pillar structure connected with the backplate and the diaphragm and a protection post structure extending from the backplate into the air gap. From a top view of the backplate, the protection post structure surrounds the pillar structure.