Acoustic Sensor Frame Wall Sacrifice Layer Shock Resistance

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Solution Overview

Problem

MEMS-based acoustic sensors face challenges in achieving shock resistance without compromising sensitivity or noise performance, due to limitations in the semiconductor manufacturing process.

Innovation Solution

A design where a sacrifice layer remains on the inner side of the frame wall around the fixing plate, with a roughness smaller than the sound hole shape reflecting structure, reinforcing the frame wall and improving shock resistance without affecting sensitivity or noise performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the vibration electrode film and back plate are thinned to enable downsizing, then the acoustic sensor size is reduced, but shock resistance deteriorates

Engineering Contradiction:

Improveacoustic sensor sizeVSAvoidshock resistance

Core Design Contradiction:

Volume of moving objectVSStrength

Solution Approach 1:

The patent applies local quality by making the frame wall thicker only in specific regions where shock resistance is needed, rather than uniformly thickening the entire structure. The frame wall has a first thickness in regions requiring enhanced shock resistance and a second thickness (smaller than the first) in other regions, allowing localized reinforcement without compromising overall sensor size or sensitivity.

Inventive Principle:

Principle #3Local quality

2Strength

If the frame wall is thickened to improve shock resistance, then shock resistance is improved, but sensitivity decreases and thermal noise increases

Engineering Contradiction:

Improveshock resistanceVSAvoidsensitivity and noise performance

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The frame wall is designed with variable thickness, having a first thickness in regions where shock resistance is prioritized and a second thickness (smaller than the first) in regions where sensitivity and noise performance are critical. This localized differentiation allows the structure to achieve adequate shock resistance without the penalty of uniform thickening that would degrade acoustic performance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The frame wall is segmented into different thickness regions, with the thickness varying according to functional requirements. This segmentation allows independent optimization of shock resistance in certain areas while maintaining sensitivity and low noise in other areas, resolving the contradiction between these competing requirements.

Inventive Principle:

Principle #1Segmentation

3Manufacturing precision

If the sacrifice layer is completely removed using etching liquid, then manufacturing precision is improved, but shock resistance deteriorates due to stress concentration

Engineering Contradiction:

Improveetching precisionVSAvoidshock resistance

Core Design Contradiction:

Manufacturing precisionVSStrength

Solution Approach 1:

The sacrifice layer is intentionally left remaining in the frame wall region before final assembly, serving as a preliminary reinforcement structure. This remaining sacrifice layer acts as a buffer that prevents stress concentration and reduces the risk of cracking during subsequent handling and assembly processes, improving shock resistance without compromising manufacturing precision.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The remaining sacrifice layer in the frame wall provides beforehand cushioning against mechanical stress and shocks. By maintaining this layer in the frame wall region, the structure is pre-protected against potential damage during assembly and operation, reducing stress concentration points that would otherwise lead to cracking.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 approach enhances shock resistance by reducing stress concentration and maintaining sensitivity and noise performance, while allowing for downsizing of the acoustic sensor.

Implementation Method 1

an acoustic sensor that detects acoustic vibration by converting the acoustic vibration into change in electrostatic capacitance between a vibration electrode film and a fixed electrode film

Methodology Applied

Scientific EffectElectrostatic capacitance: Capacitance

Implementation Method 2

removing the sacrifice layer using etching liquid supplied from the plurality of sound holes

Methodology Applied

Scientific EffectEtching:

Data Source

PatentUS9674618B2Acoustic sensor and manufacturing method of the same

Publication Date: 2017.06.06 MMI SEMICON CO LTD

AI summary

An acoustic sensor is provided for improving shock resistance performance, along with a method for manufacturing the acoustic sensor. In the acoustic sensor, a fixing plate is provided by a semiconductor manufacturing process, a frame wall has a curved shape in at least a portion of the periphery of the fixing plate, the frame wall being coupled to the semiconductor substrate. A sacrifice layer removed from the inner side of the fixing plate in the manufacturing process remains at least on a portion of the inner side of the frame wall. Roughness of the remaining sacrifice layer is smaller than roughness of a sound shape reflecting structure in which a shape similar to the external shape of sound holes is repeated. Roughness of the sound shape reflecting structure is formed when removing the sacrifice layer using etching liquid supplied from the plurality of sound holes in the semiconductor manufacturing process.