Semiconductor Strain Sensor Layout for Higher SNR Pressure Sensing
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Solution Overview
Problem
Conventional semiconductor strain sensors face challenges in achieving high accuracy and long-time reliability for precise pressure measurement in automotive engines, particularly in high-pressure environments, due to limitations in signal-to-noise ratio and temperature stability.
Innovation Solution
The semiconductor strain sensor employs a strain detection region with equally distributed Wheatstone bridges on a semiconductor substrate, where the output signals from multiple bridges are added to enhance signal characteristics and square-average noise components, improving the signal-to-noise ratio and achieving accurate strain detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional metal foil strain gauge is used, then simple structure and low cost are achieved, but measurement accuracy deteriorates when temperature changes
Solution Approach 1:
The patent changes the material parameter from metal foil to semiconductor impurity diffusion resistors, which have different temperature characteristics. The semiconductor resistors are formed by diffusion processes that create specific temperature compensation properties, resolving the contradiction between simple structure and temperature-stable measurement accuracy.
Solution Approach 2:
The patent uses a composite structure combining semiconductor substrate with impurity diffusion resistors, integrating multiple functional properties into a single device. This composite approach enables both structural simplicity and temperature-compensated measurement accuracy simultaneously.
2Ease of manufacture
If conventional metal foil strain gauge is used, then low cost is achieved, but power consumption increases
Solution Approach 1:
The patent changes the operational parameters by using semiconductor resistors with higher gauge factors, which provide greater signal output for the same strain input. This allows the use of lower excitation currents, thereby reducing power consumption while maintaining cost-effectiveness through standard semiconductor manufacturing processes.
3Ease of manufacture
If conventional metal foil strain gauge is used, then low cost is achieved, but installation area increases
Solution Approach 1:
The patent segments the strain detection function into multiple small impurity diffusion resistors arranged in a compact pattern on the semiconductor substrate. This segmentation allows the same measurement function to be achieved in a much smaller area compared to conventional metal foil gauges, reducing installation space requirements.
Solution Approach 2:
The patent transitions from planar metal foil structures to vertically-integrated semiconductor structures where resistors are formed through diffusion processes into the substrate. This dimensional change enables compact three-dimensional arrangements that reduce the footprint while maintaining measurement functionality.
4Measurement precision
If semiconductor strain sensor with multiple Wheatstone bridges is used, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple Wheatstone bridge circuits into a single integrated semiconductor device, with all resistors fabricated using the same diffusion process on the same substrate. This merging approach improves signal-to-noise ratio through signal averaging while minimizing device complexity by using unified manufacturing processes and compact integration.
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 results in a mechanical quantity measuring apparatus with higher detection performance and a pressure sensor with enhanced accuracy and long-time reliability, capable of handling high-pressure and temperature variations effectively.
Implementation Method 1
a strain detection region constituted by impurity diffusion resistors formed on a surface of a semiconductor substrate
Implementation Method 2
The strain detection region includes a plurality of Wheatstone bridges
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Provided are a mechanical quantity measurement device having a higher signal-to-noise ratio and resolution than the prior art and a pressure sensor using the same. A mechanical quantity measurement device that is provided with a plurality of Wheatstone bridges on the main surface of a single semiconductor substrate 1 that are composed from impurity-diffused resistors and detect the difference between the strain amount occurring in the x-axis direction and the strain amount occurring in the y-axis direction, which intersect at right angles on the main surface of the semiconductor substrate 1, said mechanical quantity measurement device being characterized in that the impurity-diffused resistors composing the plurality of Wheatstone bridges are disposed evenly in an area to be measured.