MEMS Device Cavity Sealing via Sacrificial-Layer Extraction
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Solution Overview
Problem
Existing MEMS device manufacturing methods require long production periods and are prone to structural defects due to the use of silicon-based materials and processes like CMP, which can lead to cracks and delamination from thermal expansion coefficient mismatches.
Innovation Solution
A method involving deposition of a thin film on a sacrificial layer, defining through holes, removing material to create a cavity, and sealing with a separate sealing layer, optionally using a structural layer with a hollow portion to facilitate machining and reduce thermal expansion coefficient mismatches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thin film layer is deposited on the top of the cavity and air outlet holes are defined by etching process, then sealing can be realized, but the production period is relatively long
Solution Approach 1:
The patent extracts and removes the sacrificial layer material through the air outlet holes after deposition, allowing the thin film to be formed first and then the cavity to be created by removing the sacrificial material. This reverses the traditional sequence where the cavity is formed first, then sealed. By taking out the sacrificial layer through the holes rather than forming holes through the sealed film, the process is simplified and time is reduced while maintaining sealing integrity.
2Manufacturing precision
If silicon-based materials and CMP process are used, then manufacturing precision can be achieved, but structural defects such as cracks and delamination occur due to thermal expansion coefficient mismatches
Solution Approach 1:
The patent changes the material parameter selection by using materials with matched thermal expansion coefficients. Specifically, it employs silicon oxide structural layer and silicon-based thin film materials that have compatible thermal expansion properties, eliminating the thermal mismatch that causes cracks and delamination in traditional CMOS processes. This parameter change maintains manufacturing precision while improving structural reliability.
Solution Approach 2:
The patent uses a composite structure consisting of a silicon oxide structural layer combined with silicon-based thin film materials (such as silicon nitride or polysilicon). This composite material approach ensures thermal expansion compatibility between layers, preventing delamination and cracks while achieving the required manufacturing precision for MEMS devices.
3Reliability
If wafer bonding and film packaging are used for sealing, then sealing can be realized, but manufacturing cost and maintenance are greatly increased
Solution Approach 1:
The patent implements self-service sealing where the thin film layer itself serves as the sealing structure. By forming the thin film over the cavity and sealing the air outlet holes with the same or compatible material layers, the structure seals itself without requiring separate wafer bonding or film packaging processes. This eliminates the need for additional sealing steps, reducing manufacturing cost and complexity while maintaining reliable sealing capability.
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 shortens production time, enhances sealing reliability, reduces defects, and improves the operating reliability and service life of the MEMS device by avoiding CMP and minimizing material defects.
Implementation Method 1
depositing a thin film on at least a part of a surface of a sacrificial layer
Implementation Method 2
the at least one through hole is defined in the thin film by laser drilling or surface ablation
Implementation Method 3
depositing a sealing layer on a surface of the thin film facing away from the sacrificial layer to seal the at least one through hole
Data Source
AI summary
A method for manufacturing a MEMS device and the MEMS device are provided. The method includes: depositing a film on at least a part of a surface of a sacrificial layer, defining at least one through hole in the thin film by machining, removing at least a part of a material covered by the thin film in the sacrificial layer, discharging the part of the material removed from the sacrificial layer from the at least one through hole to define a cavity in the sacrificial layer, and depositing a sealing layer on a surface of the thin film facing away from the sacrificial layer to seal the at least one through hole. Compared with the manufacturing method in the related art, the manufacturing method of the disclosure only requires to deposit one layer of thin film, shorten the production period, and has reliable on-site sealing capability.