Physical Quantity Sensor Wall Protrusion Design
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Solution Overview
Problem
Conventional semiconductor physical quantity sensors face issues with moisture infiltration and reduced sensitivity due to the material properties of their walls, which affect the accuracy of capacitance measurements.
Innovation Solution
The sensor design incorporates a wall with protrusions made of silicon nitride and silicon nitride containing Si—H bonds, which enhances moisture resistance and sensitivity by preventing moisture infiltration and increasing the distance between the diaphragm and electrode, while also improving pressure resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional wall structure is used in the sensor, then the device complexity is low, but moisture infiltration occurs and measurement precision deteriorates
Solution Approach 1:
The wall is divided into multiple functional layers: a first wall portion and a second wall portion with different material compositions and properties. This segmentation allows each layer to perform specific functions - the first layer provides structural support while the second layer with protrusions provides moisture resistance and maintains capacitance measurement accuracy, thereby resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The wall employs composite material structure with at least two different materials having distinct physical properties. The first wall portion and second wall portion use different materials optimized for their respective functions, creating a composite structure that simultaneously achieves moisture resistance, mechanical strength, and accurate capacitance measurements without excessive complexity.
2Strength
If the distance between diaphragm and electrode is increased to improve pressure resistance, then strength improves, but sensitivity deteriorates
Solution Approach 1:
The second wall portion includes protrusions that locally extend toward the electrode, creating localized regions with different gap distances. These protrusions are strategically positioned to provide moisture barriers and mechanical support in critical areas while maintaining smaller gaps in measurement-sensitive regions, thus achieving both pressure resistance and sensitivity through spatially varying local properties.
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 improves the moisture resistance and sensitivity of the sensor, reducing the likelihood of cracks and maintaining high accuracy in capacitance measurements.
Implementation Method 1
The physical quantity sensor has high moisture resistance
Implementation Method 2
The diaphragm warps in accordance with physical quantity applied from the outside
Implementation Method 3
the accuracy of capacitance measurements
Data Source
AI summary
A physical quantity sensor includes a first substrate, an electrode provided on the first substrate, a diaphragm made of semiconductor material, a second substrate fixed to the first substrate, a dielectric film provided on the diaphragm, and a wall provided between the dielectric film and the electrode. The second substrate supports the diaphragm such that the diaphragm has an opposing surface facing the electrode across a space. The dielectric film is provided on the opposing surface of the diaphragm. The dielectric film has a surface facing the electrode across the space. The wall includes a first protrusion and a second protrusion. The first protrusion protrudes toward the electrode from the surface of the dielectric film. The second protrusion protrudes toward the electrode from the first protrusion, and contacts the electrode. The second protrusion is made of material which is different from material of the dielectric film.