MEMS Microphone Etching Residue Removal
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Solution Overview
Problem
Conventional methods for manufacturing MEMS microphones struggle to completely remove sacrificial layers, leading to residues between the membrane and backplate, which reduce reliability and increase power consumption.
Innovation Solution
An etching method involving a first plasma process with a mixed gas of oxygen and nitrogen-based gases to remove the sacrificial Polyimide structure, followed by a second plasma process with a mixed gas of nitrogen-based and fluorine-based gases to remove the adhesion Organosilane layer, ensuring effective residue removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional etching methods are used to remove the sacrificial layer, then the manufacturing process is simple, but residues remain between the membrane and backplate reducing reliability
Solution Approach 1:
The etching process is divided into multiple sequential steps with different gas compositions. The first etching step uses a nitrogen-based gas to remove the sacrificial layer, and the second etching step uses a fluorine-based gas to remove the adhesion layer. This segmentation allows each step to target specific materials effectively, ensuring complete removal of residues while maintaining process control.
Solution Approach 2:
The patent changes the chemical composition parameters of the etching gas between steps. By switching from a nitrogen-based gas to a fluorine-based gas, the etching chemistry is optimized for different materials (sacrificial layer vs. adhesion layer). This parameter change enables selective and complete removal of each layer without leaving residues.
2Productivity
If conventional single-step etching is used, then the manufacturing process is fast, but adhesion layer residues remain reducing yield
Solution Approach 1:
The etching process is divided into multiple sequential steps with different gas compositions. The first etching step uses a nitrogen-based gas to remove the sacrificial layer, and the second etching step uses a fluorine-based gas to remove the adhesion layer. This segmentation allows each step to target specific materials effectively, ensuring complete removal of residues while maintaining process control.
Solution Approach 2:
The patent introduces an intermediary approach by using different gas chemistries as mediators for different etching tasks. The nitrogen-based gas acts as an intermediary for removing organic sacrificial layers, while the fluorine-based gas serves as an intermediary for removing inorganic adhesion layers. This intermediary strategy ensures complete removal of each layer type without cross-contamination or residue.
3Ease of manufacture
If residues of sacrificial layer remain, then the manufacturing process is simple, but power consumption increases and reliability decreases
Solution Approach 1:
The patent changes the chemical composition parameters of the etching gas between steps. By switching from a nitrogen-based gas to a fluorine-based gas, the etching chemistry is optimized for different materials (sacrificial layer vs. adhesion layer). This parameter change enables selective and complete removal of each layer without leaving residues.
Solution Approach 2:
The use of fluorine-based gas in the second etching step acts as a strong chemical agent that effectively removes the adhesion layer residues. The fluorine chemistry provides accelerated removal capability ensuring complete cleanup of the interface between the membrane and backplate, preventing any residue that could cause future power consumption issues.
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 method enhances the yield of MEMS devices by thoroughly removing sacrificial and adhesion layers, preventing residues and reducing power consumption, thereby improving the reliability of capacitive MEMS microphones.
Implementation Method 1
performing a first plasma etching process by using a first mixed gas to remove the sacrificial structure, wherein the first mixed gas includes oxygen and a first nitrogen-based gas
Implementation Method 2
performing a second plasma etching process by using a second mixed gas to remove the adhesion layer, wherein the second mixed gas includes a second nitrogen-based gas and a fluorine-based gas
Data Source
AI summary
An etching method for manufacturing MEMS devices is provided. The method includes steps of: providing a substrate including a first surface and a second surface opposite to the first surface, wherein a base structure, a sacrificial structure and at least one adhesion layer are arranged on the first surface of the substrate, the adhesion layer is disposed between the base structure and the sacrificial structure, the base structure is disposed between the adhesion layer and the substrate; performing a surface grinding process on the second surface of the substrate; performing a first plasma etching process by using a first mixed gas to remove the sacrificial structure, wherein the first mixed gas includes oxygen and a first nitrogen-based gas; and performing a second plasma etching process by using a second mixed gas to remove the adhesion layer, wherein the second mixed gas includes a second nitrogen-based base gas and a fluorine-based gas.