Oblong MEMS Pressure Sensor Diaphragm Design
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Solution Overview
Problem
Microelectromechanical pressure sensors face challenges in accurately detecting pressure-induced deflection due to thermal expansion and packaging-induced bending stresses, which distort measurements and reduce sensitivity.
Innovation Solution
The design of an oblong sensor structure with a diaphragm that is at least three times longer than its width, minimizing bending errors and enhancing robustness and sensitivity by aligning with the wafer's bending form, while maintaining a robust structure and efficient area usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional square or circular diaphragm is used, then the sensor structure is compact and easy to manufacture, but the measurement precision deteriorates due to bending errors and thermal expansion effects
Solution Approach 1:
The patent applies asymmetry by changing the diaphragm shape from conventional square or circular forms to an oblong configuration where the length is at least three times the width. This asymmetric dimensioning creates a fundamental difference in how the diaphragm responds to bending forces compared to conventional shapes, enabling the wafer and diaphragm to bend in a coordinated manner that reduces measurement errors while maintaining manufacturing feasibility
2Measurement precision
If the diaphragm dimensions are increased to improve detection area, then sensitivity improves, but the structure becomes more susceptible to bending stresses and thermal expansion effects
Solution Approach 1:
The patent applies parameter changes by specifically adjusting the dimensional parameters of the diaphragm, setting the length to be at least three times the width. This parameter optimization creates a geometric configuration where the increased detection area is achieved while simultaneously reducing susceptibility to bending stresses and thermal expansion effects through the specific aspect ratio
3Reliability
If the sensor structure is made more robust to resist bending stresses, then reliability improves, but the detection sensitivity decreases due to reduced diaphragm deflection
Solution Approach 1:
The patent applies segmentation by dividing the structural considerations into two coordinated components: the wafer structure and the diaphragm structure. By optimizing their dimensional relationship with the oblong diaphragm configuration, the system achieves both robustness and sensitivity through proper structural segmentation rather than requiring a single overly rigid structure
4Measurement precision
If conventional diaphragm shapes are used, then manufacturing is simpler, but the area usage efficiency is suboptimal for pressure detection
Solution Approach 1:
The patent applies asymmetry with the oblong diaphragm shape that achieves superior area usage efficiency for pressure detection. While this asymmetric configuration is more complex than a simple circle or square, it remains compatible with standard semiconductor manufacturing processes, achieving a balance between optimized performance and manufacturing feasibility
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 significantly reduces measurement errors caused by bending, improves sensitivity by utilizing the deflected area effectively, and maintains mechanical robustness, enhancing the accuracy and reliability of pressure sensor readings.
Implementation Method 1
The diaphragm deforms due to difference between the reference pressure and an ambient pressure surrounding the sensor
Implementation Method 2
The diaphragm displacement may be translated to an electrical signal with capacitive or piezoresistive sensing
Implementation Method 3
Already change of dimensions of the elements caused by thermal expansion in varying operating temperatures can cause significant variations to the measured values
Implementation Method 4
The package may have different thermal expansion coefficient than the sensor structure, which may cause large, temperature dependent bending stresses that distort the measurements
Data Source
Figure 1
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Figure 3~4
AI summary
A microelectromechanical pressure sensor structure wherein the length of the diaphragm is at least three times the width of the diaphragm. The oblong diaphragm experiences a minimized difference between lateral bending of the wafer and of the diaphragm along the width of the diaphragm. In a perpendicular direction, the diaphragm is at least three times longer due to which it accurately aligns with the bending form of the wafer. Due to this, the total error caused by bending of the structure is significantly reduced and a more robust structure is achieved. At the same time, the longer diaphragm provides mode deflected area for detection and thus significantly improves sensitivity of the device.