Exfoliation Detection in Strain Sensors via Segmented Wheatstone Bridge
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Solution Overview
Problem
Conventional strain sensor chips face challenges in detecting exfoliation due to small changes in sense output from Wheatstone bridges, especially when exfoliation occurs simultaneously in multiple corners, and are prone to noise from electromagnetic waves, making accurate exfoliation detection difficult.
Innovation Solution
The implementation of plural impurity diffused resistors forming groups that connect to form a Wheatstone bridge on the outer peripheral part of the semiconductor substrate, with a small sectional area to minimize noise and ensure detection of exfoliation by arranging Wheatstone bridges in a configuration that allows for early detection of exfoliation and accurate measurement of resistance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If impurity diffused resistors are arranged in the four corners to detect exfoliation, then exfoliation detection capability is improved, but noise from electromagnetic waves increases due to large sectional area of the Wheatstone bridge
Solution Approach 1:
The Wheatstone bridge is divided into four separate impurity diffused resistors positioned at the corners of the semiconductor substrate. This segmentation allows each resistor to have a small individual sectional area, reducing electromagnetic noise, while collectively forming the complete bridge circuit for exfoliation detection.
2Loss of time
If impurity diffused resistors are placed in the four corners for early exfoliation detection, then detection timing is improved, but measurement precision deteriorates when exfoliation occurs simultaneously in multiple corners due to offsetting resistance changes
Solution Approach 1:
Each corner of the semiconductor substrate is equipped with an impurity diffused resistor with specific local properties. The resistors are positioned to detect exfoliation at the corners where it most commonly initiates, and their individual resistance changes are processed through the Wheatstone bridge to provide accurate measurement even when multiple corners experience exfoliation simultaneously.
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 enables secure detection of exfoliation by amplifying the change in electric potential, reducing noise interference, and allowing for timely detection of exfoliation events, even when occurring in multiple corners simultaneously.
Implementation Method 1
an impurity diffused resistor is formed on a surface of this strain sensor chip (mechanical quantity measuring device) and the strain sensor chip (mechanical quantity measuring device) is attached to a measured object, with an adhesive. When a mechanical quantity acts on the measured object and the measured object is strained, the impurity diffused resistor is strained via the adhesive and the resistance thereof changes.
Implementation Method 2
it is proposed that impurity diffused resistors as exfoliation monitoring sensors are provided in the four corners of the strain sensor chip (mechanical quantity measuring device), in addition to the impurity diffused resistor for measuring the mechanical quantity acting on the measured object, and that these impurity diffused resistors in the four corners are connected to form a Wheatstone bridge
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A mechanical quantity measuring device (100) includes: a semiconductor substrate (1) attached to a measured object so as to indirectly measure the mechanical quantity acting on the measured object; a measuring portion (7) capable of measuring a mechanical quantity acting on a semiconductor substrate (1) at a central part (1c) of the semiconductor substrate (1); and plural impurity diffused resistors (3a, 3b, 4a, 4b) forming a group (5) gathering closely to each other in at least one place, on an outer peripheral part (1e) outside the central part (1c) of the semiconductor substrate (1). The plural impurity diffused resistors (3 a, 3b, 4a, 4b) forming one of the groups (5) are connected to each other to form a Wheatstone bridge (2a, 2b). Thus, the mechanical quantity measuring device (100) can securely detect its own exfoliation.