MEMS Microphone Anti-Stick Backplate Structures
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Solution Overview
Problem
Conventional MEMS microphones face issues with the membrane sticking to the backplate due to reduced gap distances, leading to malfunction, as the sensitivity enhancement increases the likelihood of adhesion.
Innovation Solution
The implementation of anti-sticky structures on the backplate layer, which penetrate through the electrode layer and are designed to prevent the membrane from adhering to the backplate, ensuring proper vibration and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gap between the membrane and the backplate is reduced to improve sensitivity, then the capacitance increases and sensitivity improves, but the membrane may stick to the backplate causing malfunction
Solution Approach 1:
The backplate is segmented into multiple regions: a central region with venting holes and an peripheral region with anti-sticky structures. This segmentation allows the backplate to simultaneously provide acoustic venting functionality and prevent membrane sticking, resolving the contradiction between sensitivity (requiring small gap) and reliability (preventing adhesion).
Solution Approach 2:
Different regions of the backplate are assigned different local properties: the central region has venting holes for acoustic function, while the peripheral region has anti-sticky structures with specific materials or surface properties. This local differentiation allows the system to maintain small gap for sensitivity while preventing sticking at critical locations where adhesion is most likely to occur.
2Measurement precision
If the membrane is kept close to the backplate to enhance capacitance, then the sensing capability improves, but the likelihood of adhesion increases
Solution Approach 1:
Anti-sticky structures are pre-formed on the backplate before the membrane is assembled. These structures proactively prevent adhesion by creating physical or chemical barriers that repel the membrane, countering the harmful adhesion effect before it can occur during operation.
Solution Approach 2:
The anti-sticky structures act as an intermediary layer between the membrane and the backplate. This intermediary prevents direct contact and adhesion between the membrane and the backplate surface, while still allowing the capacitor to function at the reduced gap distance for enhanced sensitivity.
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 anti-sticky structures effectively reduce the likelihood of membrane sticking, maintaining the sensitivity and functionality of the MEMS microphone by allowing for controlled vibration and capacitance variation.
Implementation Method 1
The membrane and the backplate are applied with two operation voltage levels to form as a capacitance during operation. The membrane senses the pressure of acoustic signal and changes the capacitances, so that the acoustic signal is transformed into electric signal for use in the puerperal electronic circuit.
Data Source
AI summary
A structure of micro-electro-mechanical-system (MEMS) microphone includes a substrate, having a first opening. A dielectric layer is disposed on the substrate, wherein the dielectric layer has a second opening aligned to the first opening. A membrane is disposed within the second opening of the dielectric layer. A peripheral region of the membrane is embedded into the dielectric layer at sidewall of the second opening. A backplate layer is disposed on the dielectric layer. The backplate layer includes a protection layer, having a peripheral region disposed on the dielectric layer and a central region with venting holes over the second opening. The central region of the protection layer further has anti-sticky structures at a side of the protection layer toward the membrane. An electrode layer is disposed on the side of the protection layer, surrounding the anti-sticky structures.