Capacitive Sensor Side Wall Reinforcement
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Solution Overview
Problem
Conventional capacitive vibration sensors face strength issues at the side wall portion of the fixed electrode plate due to thin film thickness and poor film quality during manufacturing, leading to reduced impact resistance and breakage resistance.
Innovation Solution
A capacitive sensor design incorporating a reinforcement film made of metal, such as Au, Cr, or Pt, on the side wall portion of the fixed electrode plate to enhance strength and prevent etching, while ensuring electrical insulation from the movable and fixed electrode plates, thereby simplifying manufacturing and reducing parasitic capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the back plate is formed by depositing SiN on the mesa type sacrifice layer, then the fixed electrode plate is formed, but the film thickness becomes thinner and film quality becomes worse at the side wall portion, reducing strength
Solution Approach 1:
The patent applies local quality by forming a reinforcement film specifically at the side wall portion of the fixed electrode plate where strength is compromised. This localized reinforcement addresses the specific weakness at the side wall without modifying the entire structure, maintaining thin film characteristics in other areas while strengthening the vulnerable side wall region through targeted material deposition.
Solution Approach 2:
The patent employs composite materials by combining the SiN back plate with an additional reinforcement film material deposited on the side wall portion. This creates a composite structure where the reinforcement film material provides enhanced mechanical strength to the side wall, compensating for the inherent thinness and quality issues caused by the deposition process on the mesa structure.
2Productivity
If the hollow part is formed by etching the Si substrate, then the vibration sensor structure is created, but the back plate thickness is reduced particularly at the side wall portion
Solution Approach 1:
The patent applies preliminary action by forming the reinforcement film on the side wall portion before the etching process that creates the hollow part. This pre-reinforcement ensures that when the etching process removes material and reduces back plate thickness, the side wall portion maintains adequate structural integrity due to the previously deposited reinforcement film.
Solution Approach 2:
The reinforcement film is applied locally at the side wall portion where thickness reduction is most critical during etching. This localized approach maintains overall productivity by not requiring universal thickening of the back plate, while specifically addressing the vulnerability at the side wall region exposed by the hollow part formation.
3Ease of manufacture
If the sacrifice layer is removed by etching, then the vibration electrode plate is exposed, but the back plate is simultaneously etched and side wall thickness is reduced
Solution Approach 1:
The reinforcement film is deposited on the side wall portion before the sacrifice layer removal etching process. This preliminary reinforcement protects the back plate from excessive etching damage during sacrifice layer removal, maintaining side wall thickness and strength while still allowing the etching process to proceed for exposing the vibration electrode plate.
Solution Approach 2:
The reinforcement film acts as a protective cushion deposited beforehand to compensate for the inevitable etching damage that occurs during sacrifice layer removal. This pre-cushioning ensures that even though the etching process removes some material, the critical side wall portion maintains adequate thickness and strength for device operation.
4Ease of manufacture
If the side wall portion has thin film thickness and poor film quality, then manufacturing is simplified, but impact resistance and breakage resistance are reduced
Solution Approach 1:
The patent applies local quality by selectively reinforcing only the side wall portion with a reinforcement film, rather than uniformly thickening the entire back plate. This localized approach maintains the overall simplicity of manufacturing while specifically addressing the reliability issue at the vulnerable side wall region, improving impact and breakage resistance where needed.
Solution Approach 2:
The patent uses composite materials by combining the original SiN back plate with an additional reinforcement film material at the side wall portion. This composite structure provides enhanced mechanical properties and reliability for impact and breakage resistance, while maintaining the thin film characteristics and manufacturing simplicity of the original structure in non-critical areas.
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 reinforcement film effectively increases the impact resistance and breakage resistance of the capacitive sensor by maintaining the thickness and quality of the side wall portion, while maintaining sensitivity and preventing crack formation.
Implementation Method 1
a reinforcement film 44 is formed on at least one part of the side wall portion 43
Implementation Method 2
a capacitive sensor 31, wherein a movable electrode plate 34 is arranged on an upper surface of a substrate 32, and a fixed electrode plate 35 is arranged on the upper surface of the substrate 32 so as to cover the movable electrode plate 34, a physical amount or change thereof being detected by a capacitance or a change thereof between the movable electrode plate 34 and the fixed electrode plate 35
Data Source
AI summary
A hollow part is formed in a silicon substrate through the front and the back. A vibration electrode plate is arranged on an upper surface of the silicon substrate to cover the opening on the upper surface. A fixed electrode plate covers the upper side of the vibration electrode plate while maintaining a microscopic gap with the vibration electrode plate, where the peripheral part is fixed to the upper surface of the silicon substrate. The fixed electrode plate has the portion facing the upper surface of the silicon substrate through a space supported by a side wall portion arranged on an inner edge of the portion fixed to the upper surface of the silicon substrate without interposing a space. The outer surface of the side wall portion of the fixed electrode plate is covered by a reinforcement film made of metal such as Au, Cr, and Pt.