Semiconductor Pressure Sensor With Multiple Diaphragms
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Solution Overview
Problem
Conventional semiconductor pressure sensors fail to ensure functional safety and high-accuracy measurement across different pressure ranges due to single diaphragm design, leading to potential malfunctions and increased failure rates in vehicle applications, especially when measuring hydrogen gas pressures.
Innovation Solution
A semiconductor pressure sensor design featuring multiple diaphragms with varying thicknesses and optimized pressure-sensitive characteristics, formed using single crystal silicon substrates and oxide films, allowing for high-accuracy pressure measurement across different ranges without increasing sensor size, and providing redundancy to prevent system malfunctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single diaphragm is used in the pressure sensor, then the device complexity is reduced, but the reliability decreases because the entire system malfunctions if the diaphragm breaks
Solution Approach 1:
The pressure sensor is divided into multiple independent pressure-sensitive elements (first and second pressure-sensitive elements) with separate diaphragms. Each element can independently detect pressure, and the sensor can continue to operate even if one element fails, thereby improving reliability while maintaining manageable device complexity through modular segmentation.
2Measurement precision
If multiple diaphragms with different thicknesses are added to measure different pressure ranges, then the measurement precision across different pressure ranges is improved, but the device complexity increases
Solution Approach 1:
Different regions of the sensor contain diaphragms with locally optimized thicknesses and material properties. The first pressure-sensitive element has a first diaphragm optimized for one pressure range, while the second pressure-sensitive element has a second diaphragm optimized for another pressure range. This local optimization enables high measurement precision across different pressure ranges without requiring a complex reconfigurable structure.
3Measurement precision
If a glass wafer is used for the reference pressure chamber seating, then the manufacturing ease is improved, but the measurement precision deteriorates because hydrogen gas molecules pass through the porous glass material
Solution Approach 1:
The reference pressure chamber is formed using a homogeneous solid seating structure without porous materials. The seating is configured to maintain a high vacuum state that prevents hydrogen gas molecules from passing through, ensuring measurement precision for hydrogen gas pressure while using manufacturing techniques consistent with semiconductor fabrication processes.
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
Enables high-accuracy pressure measurement across multiple ranges without size increase, enhances functional safety by allowing continued operation even if one diaphragm fails, and maintains a high vacuum state to prevent hydrogen diffusion, thus addressing the limitations of single diaphragm designs.
Implementation Method 1
a first oxide film interposed therebetween; an intermediate semiconductor substrate joined to the first semiconductor substrate with a first oxide film interposed therebetween
Implementation Method 2
Piezoresistors are provided at a peripheral portion of the diaphragm. The pressure is measured by the piezoresistors detecting stress generated by the diaphragm bending when pressure is applied.
Data Source
AI summary
A semiconductor pressure sensor includes: a first semiconductor substrate having a plurality of recesses formed thereon; an intermediate semiconductor substrate joined to the first semiconductor substrate with a first oxide film interposed therebetween; a second semiconductor substrate joined to the intermediate semiconductor substrate with a second oxide film interposed therebetween; a first reference pressure chamber formed as a space surrounded by a first recess of the first semiconductor substrate and the intermediate semiconductor substrate; a second reference pressure chamber formed as a space surrounded by a second recess formed on the first semiconductor substrate, the intermediate semiconductor substrate, and the second semiconductor substrate, the intermediate semiconductor substrate having a through hole communicating with the second recess of the first semiconductor substrate; and piezoresistors formed on a surface of the second semiconductor substrate that receives pressure, along outer peripheries of the first and second reference pressure chambers.