Asymmetric Electrode Offset for Capacitive Sensor Accuracy
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Solution Overview
Problem
Existing physical quantity sensors, such as those disclosed in JP-A-2018-515353, face challenges in accurately detecting physical quantities due to variations in the overlapping state between movable and fixed electrodes, leading to inconsistencies in capacitance measurements and reduced detection accuracy.
Innovation Solution
A physical quantity sensor configuration where the first fixed electrode and first movable electrode are positioned such that one end of the movable electrode is offset by 4 μm or more and half the thickness or less relative to the fixed electrode in the third direction, and the other end is positioned on the third direction side relative to the fixed electrode in the opposite direction, enhancing sensitivity and accuracy by minimizing the influence of fringe capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the movable electrode is positioned with its end aligned with the fixed electrode in the third direction, then the device structure is simple, but the detection accuracy deteriorates due to fringe capacitance influence
Solution Approach 1:
The patent applies asymmetry by intentionally positioning the movable electrode's end at an offset from the fixed electrode's end in the third direction. This asymmetric configuration creates a controlled fringe capacitance effect that improves detection accuracy by minimizing the influence of edge effects and stabilizing capacitance changes during measurement.
2Reliability
If the overlapping area between movable and fixed electrodes is maximized, then the capacitance signal strength increases, but the fringe capacitance fluctuations increase leading to reduced measurement stability
Solution Approach 1:
The patent applies local quality by creating a specific local configuration at the electrode ends where the movable electrode's end is positioned at an offset from the fixed electrode's end. This local asymmetric design specifically addresses the fringe capacitance issue at the electrode boundaries while maintaining the overall overlapping area for sufficient signal strength.
3Measurement precision
If additional elements are added to compensate for fringe capacitance effects, then the detection accuracy improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies self-service by designing the electrode structure itself to inherently compensate for fringe capacitance effects through the asymmetric offset configuration. This self-compensating design eliminates the need for additional compensation elements or external factors, maintaining manufacturing simplicity while achieving high detection accuracy.
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 detection accuracy and range of physical quantities by stabilizing capacitance changes, reducing the impact of fringe capacitance fluctuations and allowing for high-sensitivity acceleration detection in both the third and fourth directions without requiring additional elements or external factors.
Implementation Method 1
a first fixed electrode portion provided at a substrate; and a first movable electrode portion, in which the first fixed electrode portion includes a first fixed electrode, the first movable electrode portion includes a first movable electrode facing the first fixed electrode of the first fixed electrode portion in the second direction
Data Source
AI summary
In a physical quantity sensor, when a smaller thickness among thicknesses of first fixed electrodes in first fixed electrode portions in a third direction and thicknesses of first movable electrodes in a first movable electrode portion in the third direction is defined as TCA, in a side view in a second direction in a stationary state, one ends of the first movable electrodes on a third direction side are positioned on the third direction side by 4 μm or more and TCA/2 or less relative to one ends of the first fixed electrodes on the third direction side. When an opposite direction of the third direction is defined as a fourth direction, the other ends of the first movable electrodes on a fourth direction side are positioned on the third direction side relative to the other ends of the first fixed electrodes on the fourth direction side.