MEMS Diaphragm Release via Pre-wetting to Suppress Etching Bubbles
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Solution Overview
Problem
The wet etching process for releasing the diaphragm in MEMS devices often results in bubbles forming on the silicon substrate due to hydrophobic etchants, which can hinder the etching process and reduce the sensitivity of the device by not effectively releasing the diaphragm from the dielectric layer.
Innovation Solution
A pre-wetting process using a hydrophilic solution, such as methyl alcohol or isopropyl alcohol, is applied to the MEMS device before the wet etching process to reduce bubble formation, allowing for efficient etching of the dielectric material and proper release of the diaphragm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching process is used to release the diaphragm, then the diaphragm can be released from the dielectric layer, but bubbles form on the silicon substrate surface due to hydrophobicity of the etchant
Solution Approach 1:
The patent applies a pre-wetting treatment to the silicon substrate before the wet etching process. This preliminary action modifies the surface properties of the substrate to be hydrophilic, preventing bubble formation during the subsequent etching process. The pre-wetting step is performed in advance to prepare the surface for optimal etching conditions.
Solution Approach 2:
The patent introduces a pre-wetting solution as an intermediary substance between the substrate and the etchant. This intermediary layer modifies the interaction between the hydrophobic etchant and the silicon substrate, enabling the etchant to spread uniformly without forming bubbles. The pre-wetting solution acts as a mediator that bridges the incompatibility between the etchant and substrate surface.
2Reliability
If bubbles cover the dielectric layer surface, then the wet etching process quality deteriorates, but the etching process is still necessary to release the diaphragm
Solution Approach 1:
The pre-wetting treatment is performed before etching to prevent bubble formation that would compromise etching quality and subsequently affect device sensitivity. By addressing the surface hydrophobicity in advance, the patent ensures both high etching precision and reliable device performance.
Solution Approach 2:
The patent applies pre-wetting to counteract the hydrophobic effect of the etchant before it can cause bubble formation. This preliminary anti-action neutralizes the harmful interaction between the etchant and substrate surface, preventing the deterioration of etching quality that would otherwise occur.
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 pre-wetting process effectively suppresses bubble occurrence, enhancing the quality of the wet etching process and ensuring better release of the diaphragm, thereby improving the sensitivity and performance of the MEMS device.
Implementation Method 1
pre-wetting the MEMS device in a pre-wetting solution to at least pre-wet a sidewall surface of a cavity of the MEMS device
Implementation Method 2
the etchant relative to the silicon substrate having the cavity is hydrophobic or repellent, so a bubble may occur on the surface of the substrate
Data Source
AI summary
A method for releasing a diaphragm of a micro-electro-mechanical systems (MEMS) device at a stage of semi-finished product. The method includes pre-wetting the MEMS device in a pre-wetting solution to at least pre-wet a sidewall surface of a cavity of the MEMS device. Then, a wetting process after the step of pre-wetting the MEMS device is performed to etch a dielectric material of a dielectric layer for holding the diaphragm, wherein a sensing portion of the diaphragm is released from the dielectric layer.