Capacitance Sensor Concave Vent Hole Design
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Solution Overview
Problem
Conventional capacitance type sensors face a trade-off between reducing acoustic resistance and maintaining drop impact resistance, with existing solutions either increasing manufacturing complexity or compromising sensitivity.
Innovation Solution
A capacitance type sensor design featuring a semiconductor substrate with a vertically opened penetration hole and a concave portion on the substrate surface, which reduces vent hole resistance without shortening the vent hole length, while maintaining drop impact resistance through anisotropic wet etching techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the penetration hole of silicon substrate is widened to shorten the vent hole length, then the acoustic resistance is reduced, but the drop impact resistance deteriorates
Solution Approach 1:
The patent applies local quality by creating a concave portion only in the specific region where the periphery portion of the diaphragm overlaps with the silicon substrate top surface. This localized structural modification increases the cross-sectional area of the vent hole at the concave portion, reducing acoustic resistance without requiring overall widening of the penetration hole, thereby maintaining drop impact resistance.
2Measurement precision
If the vent hole length is shortened to reduce acoustic resistance, then the S/N ratio improves, but the drop impact resistance is compromised
Solution Approach 1:
The patent introduces a dimensional change by creating a concave portion that modifies the cross-sectional area of the vent hole along the vertical dimension. This allows the vent hole to have varying cross-sectional areas along its length, effectively reducing acoustic resistance without shortening the overall vent hole length, thus maintaining both S/N ratio and drop impact resistance.
3Object-affected harmful factors
If the penetration hole is widened to reduce vent hole resistance, then the acoustic performance improves, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating a concave portion only in the specific region where the periphery portion of the diaphragm overlaps with the silicon substrate top surface. This localized structural modification increases the cross-sectional area of the vent hole at the concave portion, reducing acoustic resistance without requiring overall widening of the penetration hole, thereby maintaining drop impact resistance.
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 solution effectively reduces acoustic resistance and improves signal-to-noise ratio while maintaining or enhancing drop impact resistance, simplifying the manufacturing process and stabilizing sensor sensitivity.
Implementation Method 1
at least part of the concave portion is formed by an inclined surface provided in the top surface of the semiconductor substrate
Implementation Method 2
The vibration of diaphragm 13 changes the capacitance between diaphragm 13 and fixed electrode film 16, and the acoustic vibration is converted into an electrical signal
Data Source
AI summary
A capacitance type sensor has a semiconductor substrate having a vertically opened penetration hole, a movable electrode film arranged above the penetration hole such that a periphery portion opposes to a top surface of the semiconductor substrate with a gap provided, and a fixed electrode film arranged above the movable electrode film with a gap with respect to the movable electrode film. A concave portion having at least a part thereof formed by an inclined surface is provided in the top surface of the semiconductor substrate in a region of the top surface of the semiconductor substrate which overlaps the periphery portion of the movable electrode film.