Capacitive Sensor Electrode Segmentation for Cost and Sensitivity
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Solution Overview
Problem
Existing physical quantity sensors face challenges in increasing sensitivity and manufacturing efficiency while reducing costs, due to the need for expensive SOI substrates and complex electrode insulation processes.
Innovation Solution
A functional device with a movable section and fixed electrode fingers formed on an insulating substrate, allowing for separate capacitance measurements without the need for expensive SOI substrates and simplifying the manufacturing process by etching in the thickness direction only.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If SOI substrate is used to form fixed electrode and movable electrode, then sensitivity is improved, but manufacturing cost increases and manufacturing efficiency decreases
Solution Approach 1:
The patent divides the substrate into a first substrate (supporting the fixed electrode) and a second substrate (supporting the movable electrode), allowing independent optimization of each substrate's material and thickness without requiring expensive SOI substrates. This segmentation enables cost reduction while maintaining the necessary electrode thickness for sensitivity.
2Measurement precision
If electrode thickness is increased to improve sensitivity, then sensitivity is improved, but manufacturing complexity increases due to multiple etching steps
Solution Approach 1:
The patent changes the manufacturing approach by forming the fixed electrode and movable electrode in separate substrates that are subsequently bonded together. This allows the electrode thickness to be controlled by substrate thickness selection rather than complex multi-directional etching processes, simplifying the manufacturing process while enabling increased electrode thickness for improved sensitivity.
3Reliability
If individual insulation of electrode fingers is implemented, then electrical insulation is achieved, but manufacturing efficiency decreases
Solution Approach 1:
The patent introduces an insulating film as an intermediary layer between the first substrate (fixed electrode) and the second substrate (movable electrode). This single insulating layer provides comprehensive electrical insulation for all electrode fingers simultaneously, eliminating the need for individual insulation of each electrode finger and significantly improving manufacturing efficiency while maintaining reliable electrical insulation.
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 enhances sensitivity and manufacturing efficiency, reduces costs, and improves reliability by eliminating the need for expensive substrates and complex insulation methods.
Implementation Method 1
detects physical quantities such as acceleration and angular velocity on the basis of the capacitance between the fixed electrode and the movable electrode
Data Source
AI summary
A functional device according to an embodiment of the invention includes: an insulating substrate; a movable section; movable electrode fingers provided in the movable section; and fixed electrode fingers provided on the insulating substrate and arranged to be opposed to the movable electrode fingers. The fixed electrode fingers include: first fixed electrode fingers arranged on one side of the movable electrode fingers; and second fixed electrode fingers arranged on the other side of the movable electrode fingers. The first fixed electrode fingers and the second fixed electrode fingers are arranged to be spaced apart from each other.