Semiconductor Strain Sensor with Multi-Bridge Detection
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Solution Overview
Problem
Current semiconductor strain sensors face challenges in achieving high accuracy and long-term reliability, particularly in pressure sensor applications, due to limitations in detecting strain differences and absolute values in multiple directions, which affects their performance under varying conditions such as temperature changes and mechanical stress.
Innovation Solution
The proposed mechanical quantity measurement device incorporates a strain detection region with multiple Wheatstone bridges on a semiconductor substrate, including P-type and polysilicon resistors arranged to detect differences and absolute values of strain in orthogonal directions, and a pressure sensor bonded to a metallic diaphragm, enhancing accuracy and reliability by independent strain measurement and correction calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional metal foil strain gauge is used, then the structure is simple and price is low, but measurement error increases with temperature changes and power consumption is high
Solution Approach 1:
The patent transitions from metal foil resistors to semiconductor impurity diffusion resistors, fundamentally changing the material parameter. This enables higher sensitivity (several tens of times greater resistance change rate) while forming all bridge circuit resistors on a single semiconductor substrate, which provides thermal stability and eliminates temperature-induced measurement errors
Solution Approach 2:
The patent uses a composite structure combining semiconductor substrate with impurity diffusion resistors formed through photolithography and diffusion processes. This composite approach integrates multiple functions (sensing, temperature compensation, signal processing) into a single device, achieving both high measurement accuracy and temperature stability
2Measurement precision
If semiconductor strain sensor with impurity diffusion resistor is used, then sensitivity to strain is high and measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges all four bridge circuit resistors onto a single semiconductor substrate using impurity diffusion technology. This integration combines multiple sensing elements into one unified structure, reducing the number of separate components and simplifying the overall device architecture while maintaining high sensitivity and accuracy
Solution Approach 2:
The semiconductor substrate serves multiple functions simultaneously: it provides the mechanical structure for strain sensing, hosts the impurity diffusion resistors for electrical measurement, and acts as a temperature-compensating platform. This multi-functionality reduces the need for separate compensation devices and simplifies the overall system
3Device complexity
If single Wheatstone bridge is used for strain detection, then device structure is simple, but ability to detect strain differences and absolute values in multiple directions is limited
Solution Approach 1:
The patent segments the strain detection function into multiple independent Wheatstone bridges (first bridge for strain difference, second bridge for absolute strain values). Each bridge is configured with resistors oriented in specific directions to detect different strain components, enabling comprehensive multi-axial measurement through functional segmentation
Solution Approach 2:
The patent extends detection from a single strain component to multiple dimensions by arranging resistors in different orientations (x-direction, y-direction, and diagonal directions) and using multiple bridges. This dimensional expansion allows simultaneous measurement of strain differences and absolute values across multiple axes
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 accuracy and long-term reliability of mechanical quantity and pressure sensors by effectively measuring strain differences and absolute values, reducing measurement errors and enhancing durability under automotive-grade conditions.
Implementation Method 1
a resistance change rate of the impurity diffusion resistor in relation to strain is as large as several tens of times that of the metal resistor of the conventional metal foil strain gauge
Implementation Method 2
at least two or more sets of bridge circuits are formed on a semiconductor monocrystalline substrate
Data Source
Figure 1
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Figure 3A
AI summary
Provided are a dynamic quantity measuring device having higher accuracy and longer-term reliability than in the prior art, and a pressure sensor using the same. A dynamic quantity measuring device is provided with a first Wheatstone bridge (A) configured by an impurity diffused resistor on a principal surface of one semiconductor substrate (1), and detects a difference between strain quantities respectively generated in an x-axis direction and a y-axis direction that are orthogonal to each other on the principal surface of the semiconductor substrate (1) by the first Wheatstone bridge (A), the dynamic quantity measuring device being provided with, on the principal surface of the semiconductor substrate (1), a second Wheatstone bridge (B) for detecting the strain quantity in the x-axis direction, and a third Wheatstone bridge (C) for detecting the strain quantity in the y-axis direction.