MEMS Pressure Sensor Etch Stop Assembly
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Solution Overview
Problem
Existing methods of manufacturing MEMS pressure sensors often result in unwanted etching of the pressure sensing film at the bottom of the pressure trench, affecting the electrical test results and reliability of the sensor due to compressive stress from the etch stop layer.
Innovation Solution
A method involving the formation of an etch stop assembly on the pressure sensing film, followed by a cover layer and mask layer, where the cover layer is etched to form the pressure trench, and the etch stop assembly is removed, preventing unwanted etching and stress on the film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional patterning process is used to form the pressure trench, then the manufacturing process is simple, but unwanted etching of the pressure sensing film occurs at the bottom of the pressure trench
Solution Approach 1:
An etch stop layer is introduced as an intermediary layer between the pressure sensing film and the cover layer. This layer acts as a mediator that stops the etching process before it reaches the pressure sensing film, preventing unwanted etching while allowing the patterning process to proceed. The etch stop layer is selectively removed later to complete the pressure trench formation.
Solution Approach 2:
The pressure trench formation process is segmented into multiple steps: first forming the pressure trench through the cover layer, then selectively removing the etch stop layer to complete the trench. This segmentation allows precise control over where etching occurs, preventing damage to the pressure sensing film while maintaining manufacturing feasibility.
2Manufacturing precision
If an etch stop layer is formed to prevent unwanted etching, then etching precision is improved, but compressive stress is applied to the pressure sensing film causing deformation
Solution Approach 1:
The etch stop layer is formed preliminarily during the manufacturing process to protect the pressure sensing film during etching. After the pressure trench is formed, the etch stop layer is selectively removed to eliminate the compressive stress. This preliminary protection followed by removal resolves both the precision and stability issues.
Solution Approach 2:
The etch stop layer serves as a temporary protective element that is discarded after completing its function. By removing the etch stop layer after pressure trench formation, the compressive stress on the pressure sensing film is eliminated, recovering the film's structural stability while maintaining the precision benefits during manufacturing.
3Reliability
If the etch stop layer is kept in place to prevent etching, then reliability is improved, but sensor drift occurs due to stress on the film
Solution Approach 1:
The etch stop layer provides preliminary protection during manufacturing to ensure reliability. After manufacturing is complete, the layer is removed to eliminate stress-induced measurement errors. This temporal separation of functions resolves both reliability and measurement precision requirements.
Solution Approach 2:
The etch stop layer is discarded after serving its protective function during manufacturing. This removal recovers the pressure sensing film's ability to provide accurate measurements by eliminating the compressive stress that would otherwise cause sensor drift, while the temporary presence of the layer ensured manufacturing reliability.
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 reduces unwanted etching and stress on the pressure sensing film, enhancing the reliability and sensitivity of the MEMS pressure sensor by preventing deformation and sensor drift.
Implementation Method 1
forming an etch stop assembly on the pressure sensing film at a location corresponding to a pressure trench
Implementation Method 2
forming a mask layer on the cover layer, wherein an opening of the mask layer is formed above the etch stop assembly and exposes a portion of the cover layer
Implementation Method 3
etching the cover layer using the mask layer so as to form the pressure trench in the cover layer
Implementation Method 4
a bottom electrode and a pressure sensing film are disposed on the substrate
Data Source
AI summary
A method of manufacturing a pressure sensor is provided. The method includes: providing a substrate, wherein a bottom electrode and a pressure sensing film are disposed on the substrate; forming an etch stop assembly on the pressure sensing film at a location corresponding to a pressure trench; forming a cover layer on the substrate covering the etch stop assembly and the pressure sensing film; forming a mask layer on the cover layer, wherein an opening of the mask layer is formed above the etch stop assembly and exposes a portion of the cover layer at the location corresponding to the pressure trench; etching the cover layer using the mask layer so as to form the pressure trench in the cover layer; removing the etch stop assembly at a bottom of the pressure trench; and removing the mask layer.