MEMS Capacitive Pressure Sensor 3D Electrode Overlap
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Solution Overview
Problem
MEMS capacitive pressure sensors face limitations in sensitivity due to a small capacitance change in response to small pressure variations, primarily because of the limited overlap area between electrode layers, which restricts their ability to accurately detect low-pressure changes.
Innovation Solution
The design incorporates a 3-D electrode structure with conductive sidewalls and a second electrode layer suspended over these sidewalls, along with a chamber, to increase the overlap area and capacitance, enhancing sensitivity by forming a MEMS capacitive pressure sensor with a substrate having specific dielectric and electrode layers and a method for their fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional planar electrode structure is used, then the device complexity is low and manufacturing is easy, but the overlap area between electrode layers is limited, resulting in low sensitivity
Solution Approach 1:
The patent transitions from a conventional planar 2D electrode structure to a 3D electrode structure with vertical sidewalls and suspended portions. This dimensional change increases the overlap area between electrode layers by utilizing the vertical dimension, thereby increasing capacitance and sensitivity without proportionally increasing device complexity
Solution Approach 2:
The patent implements a nested electrode configuration where the second electrode layer is suspended over and nested between the conductive sidewalls of the first electrode layer. This nesting arrangement maximizes the overlap area within a compact footprint, enhancing capacitance while maintaining reasonable device complexity
2Measurement precision
If the overlap area between electrode layers is increased to improve sensitivity, then the capacitance change under pressure increases, but the device structure becomes more complex
Solution Approach 1:
The patent utilizes the vertical dimension to increase overlap area by creating conductive sidewalls and suspended electrode portions that extend vertically, allowing greater capacitance change without proportionally increasing horizontal footprint or overall structural complexity
Solution Approach 2:
The second electrode layer is designed as a thin suspended film that can deform under pressure. This flexible thin film structure allows for increased overlap area with minimal material and structural complexity, while maintaining the ability to respond to pressure changes
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 configuration significantly improves the sensitivity of the pressure sensor by increasing the capacitance change under pressure, allowing for more precise detection of small pressure variations, thereby addressing the limitations of existing sensors.
Implementation Method 1
The first electrode layer 101, the second electrode layer 102 and the chamber 103 form a capacitive structure. When the second electrode layer 102 is pressed by an external pressure, the second electrode layer 102 is deformed; and the distance between the first electrode layer 101 and the second electrode layer 102 is changed. Thus, the capacitance of the capacitive structure changes.
Data Source
AI summary
A MEMS capacitive pressure sensor is provided. The pressure sensor includes a substrate having a first region and a second region, and a first dielectric layer formed on the substrate. The pressure sensor also includes a first electrode layer formed on the first dielectric layer, and a second dielectric layer having first openings formed on the first electrode layer. Further, the pressure sensor includes conductive sidewalls connecting with the first electrode layer formed on sidewalls of the first openings, and a second electrode layer with a portion formed on the second dielectric layer in the second region and the rest suspended over the conductive sidewalls in the first region. Further, the pressure sensor also includes a chamber between the conductive sidewalls and the second electrode layer; and a third dielectric layer formed on the second electrode layer exposing a portion of the second electrode layer in the first region.