MEMS Acoustic Sensing Chip: Pillar-Free Structure for Higher Sensitivity

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Solution Overview

Problem

Double-diaphragm MEMS microphones suffer from low mechanical sensitivity and high stress concentration at support pillar junctions, leading to potential diaphragm fracture and reduced signal-to-noise ratio due to the large 'equivalent thickness' of support pillars.

Innovation Solution

A MEMS acoustic sensing chip design that omits support pillars between diaphragms, incorporating vent holes independent of the inner cavity and release holes in the diaphragms, maintaining sensitivity and SNR without increasing diaphragm area, and featuring nanoscale release holes for sacrificial layer removal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If support pillars are used to mechanically connect the two diaphragms, then the structural stability is improved, but the mechanical sensitivity deteriorates due to large equivalent thickness

Engineering Contradiction:

Improvestructural stabilityVSAvoidmechanical sensitivity

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent removes the support pillars from the double-diaphragm structure. By extracting this component, the mechanical connection between diaphragms is eliminated, reducing the equivalent thickness and improving mechanical sensitivity while maintaining structural stability through alternative design approaches.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent divides the support function into separate elements: the support board with through-holes and the independent suspension mechanisms for each diaphragm. This segmentation allows each component to perform its function independently, improving overall mechanical sensitivity while maintaining structural stability.

Inventive Principle:

Principle #1Segmentation

2Strength

If support pillars are used to connect the two diaphragms, then the structural support is improved, but the stress concentration at junctions increases leading to diaphragm fracture

Engineering Contradiction:

Improvestructural supportVSAvoiddiaphragm fracture resistance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent removes the support pillars that create stress concentration points at the diaphragm junctions. By extracting this component, the stress concentration is eliminated, preventing diaphragm fracture while maintaining structural support through the support board and suspension design.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If the area of diaphragms is increased to compensate for reduced sensitivity, then the signal-to-noise ratio is improved, but the device size increases

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoiddiaphragm area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

By removing the support pillars, the patent eliminates the source of reduced mechanical sensitivity. This allows the diaphragms to maintain smaller areas while achieving the required signal-to-noise ratio, as the sensitivity loss from pillar interference is eliminated.

Inventive Principle:

Principle #2Taking out (Extraction)

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 design enhances mechanical sensitivity, reduces diaphragm fracture risk, and improves reliability while maintaining acoustic performance, facilitating miniaturization and offering superior dust and water resistance.

Implementation Method 1

the vent hole being in communication with the back cavity

Methodology Applied

Scientific EffectPressure equalization: Pressure Gradient

Implementation Method 2

at least one of the first diaphragm and the second diaphragm is provided with a release hole, the release hole being in communication with the inner cavity

Methodology Applied

Scientific EffectChemical etching: Ablation

Implementation Method 3

air in the inner cavity flows, and after sequentially passing through the second gap, the through holes, and the first gap, exerts pressure on the first diaphragm, causing the first diaphragm and the second diaphragm to vibrate synchronously

Methodology Applied

Scientific EffectAcoustic pressure transmission: Sound

Implementation Method 4

the first diaphragm and the backplate are formed with a first gap therebetween and form a first capacitor structure, and the second diaphragm and the backplate are formed with a second gap therebetween and form a second capacitor structure

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentEP4626035A1MEMS acoustic sensing chip, microphone and electronic device

Publication Date: 2025.10.01 WEIFANG GOERTEK MICROELECTRONICS CO LTD

Figure 1~2

AI summary

A MEMS acoustic sensing chip, a microphone, and an electronic device are disclosed in embodiments of the present disclosure. The MEMS acoustic sensing chip includes a substrate, a first diaphragm, a second diaphragm, a backplate, and a support structure, the substrate being provided with a back cavity; the first diaphragm, the second diaphragm, and the backplate are provided on one side of the substrate through the support structure, the first diaphragm and the second diaphragm are provided with an inner cavity therebetween, and the backplate is suspended in the inner cavity; the support structure is provided with a vent hole, the vent hole being in communication with the back cavity and being independent of the inner cavity; and at least one of the first diaphragm and the second diaphragm is provided with a release hole, which is in communication with the inner cavity.