Transducer Back-Plate with Stress-Differential Extensions

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Solution Overview

Problem

Manufacturing microphones faces challenges in preventing stiction between the movable membrane and the back-plate, which can lead to adhesion and damage, and requires minimizing contact area while maintaining membrane stability and sensitivity.

Innovation Solution

The method involves forming a back-plate with a first material layer and a second material layer of different stress properties, creating openings with extensions that bend due to stress differences, reducing contact area and preventing adhesion by allowing air displacement without damaging the membrane.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the contact area between membrane and back-plate is reduced to prevent stiction, then adhesion and damage are prevented, but membrane stability may be compromised

Engineering Contradiction:

Improveprevention of stiction and adhesionVSAvoidmembrane stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The back-plate is segmented into multiple material layers (first material layer and second material layer) with different stress properties. This segmentation allows the structure to provide both stability and controlled deflection, preventing stiction while maintaining membrane stability through the layered construction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the stress parameters of the back-plate by using materials with different stress properties in each layer. The first material layer has different stress than the second material layer, enabling controlled bending and deflection of extensions to prevent adhesion while maintaining overall structural stability.

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If extensions are made rigid to maintain structural integrity, then manufacturing is simplified, but stiction cannot be prevented

Engineering Contradiction:

Improvestructural integrityVSAvoidprevention of stiction

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The extensions are constructed as composite structures with a first material layer and a second material layer having different stress properties. This composite construction enables the extensions to bend and deflect controlled amounts, preventing stiction while maintaining sufficient structural integrity for manufacturing and operation.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

By changing the stress parameters through selective material layering, the extensions achieve controlled flexibility. The different stress in the first and second material layers creates predictable bending behavior that prevents adhesion while maintaining structural integrity.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If the back-plate is made from uniform material for simplicity, then manufacturing is easier, but controlled deflection to prevent adhesion cannot be achieved

Engineering Contradiction:

Improvematerial uniformityVSAvoidcontrolled deflection

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The back-plate is constructed from composite materials with the first material layer and second material layer having different stress properties. This composite structure enables controlled deflection and bending of extensions to prevent adhesion, while the layered approach remains manufacturable through standard deposition techniques.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different regions of the back-plate have different material properties - the first material layer and second material layer are selectively applied to create local variations in stress. This local quality differentiation enables controlled deflection where needed while maintaining ease of manufacture through targeted material deposition.

Inventive Principle:

Principle #3Local quality

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

This approach effectively reduces stiction, maintains membrane sensitivity, and prevents damage by allowing controlled deflection and air circulation, enhancing the operational reliability of microphones.

Implementation Method 1

forming a back-plate comprising a first material layer and a second material layer, the first material layer comprising a different stress than the second material layer. The method further comprises causing the extension to bend because of the different stress in the first material layer and the second material layer.

Methodology Applied

Scientific EffectStress differential:

Data Source

PatentEP3288286B1Method for making a transducer

Publication Date: 2020.05.27 INFINEON TECHNOLOGIES AG

Figure 1~2b
Figure 2c~2d
Figure 3a~3b

AI summary

A method for manufacturing a transducer comprises forming a membrane in a substrate, forming a back-plate comprising a first material layer and a second material layer, the first material layer comprising a different stress than the second material layer, and forming an opening in the back-plate, the opening comprising an extension extending into the opening. Forming the opening comprises etching the opening in the first material layer using a first etch process, and etching the opening in the second material layer using a second etch process..