MEMS Pressure Sensor Compression Stress Design
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Solution Overview
Problem
Current silicon-based pressure sensors for extreme conditions, such as those in oil and gas exploration, face limitations due to silicon's brittleness under tension and high stress, leading to performance and reliability issues, with maximum allowable pressure restricted by tension stress levels and concentrated stress areas making alignment difficult.
Innovation Solution
A microelectromechanical system (MEMS) chip with a sensitive membrane subjected to compression stress, designed to optimize stress distribution, featuring a rectangular shape with lateral walls that transmit compression stress, and a stress detection circuit to measure pressure, enhancing sensitivity and stability while avoiding tension-induced breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If silicon-based pressure sensors are used under extreme pressure conditions, then pressure measurement capability is improved, but reliability deteriorates due to silicon brittleness under tension stress
Solution Approach 1:
The patent inverts the conventional stress approach by designing the membrane to operate under compression stress instead of tension stress. The lateral walls are specifically designed to apply compressive forces to the membrane during pressure measurement, exploiting silicon's high compression strength while avoiding its brittleness under tension.
Solution Approach 2:
The patent changes the stress state parameter from tension to compression. By modifying the structural design of lateral walls and their connection to the membrane, the operating stress regime is fundamentally changed, allowing silicon to operate in its high-strength compression mode rather than its brittle tension mode.
2Stress or pressure
If maximum pressure resistance is improved by increasing tension stress tolerance, then pressure range is extended, but manufacturing precision requirements worsen due to concentrated stress areas
Solution Approach 1:
The patent inverts the stress type from tension to compression, which fundamentally changes the stress distribution pattern. Compression stress is more uniformly distributed across the membrane and lateral walls, eliminating the concentrated stress areas at junctions that plague tension-based designs and reduce alignment sensitivity.
Solution Approach 2:
The patent applies different structural qualities to different parts of the device. The lateral walls are designed with specific geometries and connection features that locally optimize stress distribution, creating zones of compressed contact between walls and membrane that distribute loads more evenly rather than concentrating them at sharp junctions.
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 enables accurate and reliable pressure measurement under extreme conditions, achieving higher output signals without breakage or fatigue, with improved sensitivity and stability compared to prior art, allowing operation from a few hundred bars to over 2000 bars.
Implementation Method 1
Stress-sensitive resistors 5, including two resistors 5a positioned longitudinally and two resistors 5b positioned transversally, also called piezoresistors or gauges, are located on the membrane 2
Data Source
Figure 1A~3
Figure 4~5
Figure 6~7
AI summary
This invention concerns a fluid pressure measurement sensor (11) comprising a microelectromechanical system (MEMS) chip (23). The MEMS chip (23) comprises two lateral walls (56), a sensitive membrane (49) connected to said lateral walls (56) and sealed cavity (9). The exterior surfaces of the lateral walls (56) and the sensitive membrane (49) are exposed to the fluid pressure. The lateral walls (56) are designed to subject the sensitive membrane (49) to a compression stress transmitted by the opposite lateral walls (56) where said lateral walls (56) are connected to the sensitive membrane (49) such that the sensitive membrane (49) works in compression only. The MEMS chip (23) also comprises a stress detection circuit (31) to measure the compression state of the sensitive membrane (49) which is proportional to the fluid pressure.