MEMS Pressure Sensor Differential Detection for Stimulus Rejection
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Solution Overview
Problem
MEMS pressure sensors face challenges in accurately measuring external pressure due to undesired mechanical stimuli, including external and internal factors, which cause spurious deformation of the membrane, leading to low detection accuracy.
Innovation Solution
The pressure sensor design incorporates two detection structures with membranes that are mechanically decoupled from external stimuli and subjected to equal but opposite pressure differences, allowing for differential detection and high rejection of internal and external mechanical stimuli.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the membrane is formed into a structure suspended with respect to the body of the pressure sensor to decouple from external mechanical stimuli, then external stimulus rejection is improved, but sensitivity to internal mechanical stimuli remains high
Solution Approach 1:
The sensor body is divided into a first body portion and a second body portion that are mechanically decoupled from each other. The membrane is suspended over the first body portion, creating independent mechanical domains that allow differential response to pressure while rejecting common-mode stimuli through the decoupled structure.
Solution Approach 2:
The first and second body portions are designed with different mechanical properties and stress states. The first body portion has higher stress and the second has lower stress, creating local quality differences that enable the membrane to respond differentially to pressure while rejecting external mechanical stimuli through the asymmetric structure.
2Object-affected harmful factors
If a further membrane is added that does not deform as a function of external pressure to serve as a reference for canceling internal mechanical stimuli, then internal stimulus rejection is improved, but sensitivity and area occupation decrease
Solution Approach 1:
The reference function is merged with the pressure sensing function by using the same membrane structure for both purposes. The membrane's deformation is measured differentially between the two body portions, eliminating the need for a separate reference membrane while maintaining internal stimulus rejection capability.
Solution Approach 2:
The membrane structure serves multiple functions simultaneously: it acts as the pressure-sensitive element, the reference element, and the mechanical decoupling element. This multi-functionality eliminates the need for additional dedicated reference components, maintaining sensitivity while providing internal stimulus rejection.
3Object-affected harmful factors
If a further membrane is added that does not deform as a function of external pressure to serve as a reference, then internal stimulus rejection is improved, but area occupation increases
Solution Approach 1:
The reference functionality is combined within the existing sensor footprint by creating a differential structure using the same membrane and body portions. This eliminates the need for additional area dedicated to a separate reference membrane, maintaining compact sensor area while providing internal stimulus rejection.
Solution Approach 2:
The reference function is implemented not through additional spatial area but through the vertical dimension and mechanical coupling configuration. The differential measurement is achieved through the three-dimensional arrangement of body portions and membrane suspension rather than expanding the sensor footprint.
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 design enhances the detection accuracy and sensitivity of the pressure sensor by effectively canceling out spurious mechanical stresses and allowing both membranes to contribute to the measurement of external pressure.
Implementation Method 1
a membrane (25, 32) facing the buried cavity (24, 30)... configured to deform as a function of an external pressure to be measured
Implementation Method 2
By detecting the deformation of the membrane, for example through piezoresistors, a measurement of the external pressure may be obtained
Data Source
Figure 1~2
Figure 3~6
Figure 7~8
AI summary
A pressure sensor (1) has a body (5) having a first chamber (12) and a second chamber (13) hermetically separated from the first chamber; a first detection structure (18) which is arranged in the first chamber (12), has a first deformable element (25) and a first buried cavity (24) within the first detection structure, wherein the first deformable element is configured to undergo a deformation as a function of a pressure difference between the first chamber and the first buried cavity. The sensor also has a second detection structure (19) which is arranged in the second chamber (13), has a second deformable element (32) and a second buried cavity (30) within the second detection structure, wherein the second deformable element is configured to undergo a deformation as a function of a pressure difference between the second chamber and the second buried cavity. The sensor also has a first channel (40) that extends into the body (5) and is configured to fluidically couple the first buried cavity (24) with the second chamber (13); and a second channel (41) that extends into the body (5) and is configured to fluidically couple the second buried cavity (30) to the first chamber (12).