Capacitance Offset Compensation in Seesaw Physical Quantity Sensors
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Solution Overview
Problem
Existing physical quantity sensors, such as seesaw type sensors, face detection accuracy issues due to electrostatic capacitance offsets caused by differences in fringe capacitance between movable and fixed electrode portions, leading to reduced accuracy in detecting acceleration or angular velocity.
Innovation Solution
A physical quantity sensor design that includes a substrate with a movable object divided into first and second movable portions, where the first and second electrodes are positioned to offset the difference between the first and second fringe capacitances, improving detection accuracy by adjusting the area and length of overlapping regions and preventing sticking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the movable object is divided into first and second movable portions with different areas, then the detection capability is improved, but the fringe capacitance difference increases causing electrostatic capacitance offset
Solution Approach 1:
The patent applies local quality by making the first electrode and second electrode have different areas corresponding to the different areas of the first and second movable portions. Specifically, the first electrode has a larger area than the second electrode, which compensates for the different fringe capacitances generated by the asymmetric movable portions, thereby reducing the electrostatic capacitance offset while maintaining detection accuracy.
2Measurement precision
If the first electrode area is made larger than the second electrode area, then the fringe capacitance difference is offset, but the device structure becomes more complex
Solution Approach 1:
The patent applies asymmetry by intentionally designing the first electrode and second electrode with different areas, where the first electrode has a larger area than the second electrode. This asymmetric design compensates for the asymmetric configuration of the movable portions and their resulting fringe capacitance differences, reducing the electrostatic capacitance offset while maintaining a relatively simple overall structure.
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
The sensor effectively reduces electrostatic capacitance offsets, enhancing detection accuracy by ensuring that the areas of the first and second regions are appropriately sized and positioned to minimize fringe capacitance differences, thereby improving the sensor's ability to accurately measure physical quantities like acceleration.
Implementation Method 1
it is possible to detect a physical quantity such as acceleration or an angular velocity based on an electrostatic capacitance between the movable electrode portion and the fixed electrode portion
Implementation Method 2
a fringe capacitance generated between the movable electrode and the fixed electrode portion in one side and a fringe capacitance generated between the movable electrode and the fixed electrode portion in the other side are different from each other
Data Source
AI summary
A physical quantity sensor includes a base substrate, a movable portion that is oscillatably provided around an axis while facing the base substrate and that is divided into a first movable portion and a second movable portion, a first fixed electrode that is disposed on the base substrate facing the first movable portion, and a second fixed electrode that is disposed on the base substrate facing the second movable portion. The first fixed electrode and the second fixed electrode are configured so as to offset at least a part of a difference between a first fringe capacitance, which is between the first movable portion and the first fixed electrode, and a second fringe capacitance, which is between the second movable portion and the second fixed electrode.