Resonant Pressure Sensor Silicon Direct Bonding Gap Control
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Solution Overview
Problem
Existing resonant pressure sensors face challenges in controlling diaphragm thickness and gap formation, leading to variations in sensitivity, limited shape flexibility, and difficulties in suppressing resonance, which affects input/output characteristics and restricts pressure range measurement.
Innovation Solution
A resonant pressure sensor design that uses silicon substrates with direct bonding at room temperature, allowing for precise control of diaphragm thickness and gap formation without the need for oxide films or dissimilar materials, enabling flexible diaphragm shapes and improved temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional etching methods are used to form diaphragm gaps, then gap formation is achieved, but manufacturing precision and control over gap size deteriorate
Solution Approach 1:
The patent replaces chemical etching processes with mechanical grinding/polishing processes to form diaphragm gaps. This substitution enables precise control over gap dimensions through controlled material removal by grinding, achieving manufacturing precision that chemical etching cannot provide while simplifying the overall manufacturing process.
Solution Approach 2:
The patent changes the manufacturing parameter from chemical etching depth to mechanical grinding depth. By controlling the grinding parameters (such as grinding pressure, speed, and duration), precise control over gap size is achieved. This parameter change allows for better control and reproducibility of gap dimensions.
2Strength
If oxide films or dissimilar materials are used in bonding, then bonding strength is achieved, but temperature characteristics and manufacturing simplicity deteriorate
Solution Approach 1:
The patent uses direct bonding of identical silicon substrates without requiring oxide films or dissimilar materials. This homogeneous bonding approach eliminates the thermal expansion mismatch issues that arise when bonding dissimilar materials, thereby improving temperature characteristics while maintaining bonding strength through direct silicon-to-silicon bonding.
3Shape
If conventional diaphragm formation methods are used, then diaphragm structure is created, but shape flexibility and design freedom deteriorate
Solution Approach 1:
The patent segments the diaphragm formation process into independent steps where the diaphragm structure is created separately from the substrate bonding. This segmentation allows for greater design freedom in diaphragm shapes while maintaining manufacturing precision through controlled grinding processes that can accommodate various geometric configurations.
4Reliability
If resonance suppression structures are added, then input/output characteristics are improved, but device complexity increases
Solution Approach 1:
The patent merges the resonance suppression function with the existing diaphragm gap structure. By optimizing the gap dimensions and positioning, the resonance suppression effect is achieved without adding separate complex structures. This integration approach improves input/output characteristics while minimizing the increase in device complexity.
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 achieves precise control over diaphragm thickness and gap formation, suppressing resonance and enhancing input/output characteristics, while allowing for flexible diaphragm shapes and cost-effective mass production without the limitations of traditional etching methods.
Implementation Method 1
the silicon diaphragm does not resonate with the resonant-type strain gauge due to density and viscosity of the fluid between the diaphragm and the vibration suppressor
Implementation Method 2
when external pressure is applied to the diaphragm, the natural frequency of the resonant-type strain gauge changes according to the external pressure. A vibration of the resonant-type strain gauge is detected by a vibration detecting unit
Implementation Method 3
silicon substrates with direct bonding at room temperature, allowing for precise control of diaphragm thickness
Data Source
Figure 1~2
Figure 3(a)~3(g)
Figure 4
AI summary
A resonant pressure sensor including one or more resonant-type strain gauges arranged on a diaphragm may include a sensor substrate made of silicon and including one surface on which one or more resonant-type strain gauge elements are arranged and the other surface which is polished to have a thickness corresponding to the diaphragm, a base substrate made of silicon and including one surface directly bonded with the other surface of the sensor substrate, a concave portion formed in a portion of the base substrate bonding with the sensor substrate, substantially forming the diaphragm in the sensor substrate, and including a predetermined gap that does not restrict a movable range of the diaphragm due to foreign substances and suppresses vibration of the diaphragm excited by vibration of the resonant-type strain gauge elements, one or more conducting holes, and a fluid.