Pre-Bent MEMS Thin Membrane for Wider-Range Pressure Sensing
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Solution Overview
Problem
Existing microelectromechanical system (MEMS) pressure sensors suffer from suboptimal sensitivity and range in pressure sensing applications.
Innovation Solution
A MEMS pressure sensor design featuring a thin membrane with a stress structure on its surface, inducing a biased deformation that enhances sensitivity and range by allowing greater membrane displacement in response to applied pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a suspended membrane is used as a pressure sensor, then the sensor can detect pressure, but the sensitivity and range are less than optimal
Solution Approach 1:
The patent applies preliminary action by introducing a stress structure that pre-bends the membrane before pressure application. This pre-deformation positions the membrane in a state that maximizes its response to incoming pressure, thereby improving sensitivity without compromising the operational range. The stress structure is integrated during manufacturing to establish this advantageous initial state.
Solution Approach 2:
The patent employs parameter changes by modifying the mechanical state of the membrane through the stress structure. By changing the initial curvature and stress distribution of the membrane, the sensor achieves enhanced sensitivity and extended pressure range. This parameter modification allows the membrane to operate in a more responsive regime across a broader pressure spectrum.
2Measurement precision
If the membrane is made thinner to increase displacement, then sensitivity improves, but the membrane strength decreases
Solution Approach 1:
The stress structure acts as a counterbalancing element that compensates for the reduced mechanical strength of thinner membranes. By introducing controlled residual stresses through the stress structure, the membrane gains the necessary structural support to maintain integrity while remaining thin enough to provide high displacement and sensitivity responses to pressure changes.
Solution Approach 2:
The patent utilizes the inherent flexibility of thin membrane films to achieve high sensitivity while managing strength concerns through the integrated stress structure. The thin film design allows for greater displacement under pressure, and the stress structure ensures that this thinning does not compromise the membrane's ability to withstand operational pressures without failure.
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 sensor achieves significantly improved sensitivity and range by maximizing membrane displacement, enabling more precise pressure detection.
Implementation Method 1
A MEMS pressure sensor design featuring a thin membrane with a stress structure on its surface, inducing a biased deformation that enhances sensitivity and range
Implementation Method 2
The sensor includes a bridge circuit having four piezoresistors, wherein each piezoresistor is formed by a doped region at the topside surface of the thin membrane
Data Source
Figure 1~4
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Figure 9A~11A
AI summary
A blind opening is formed in a bottom surface of a semiconductor substrate to define a thin membrane suspended from a substrate frame. The thin membrane has a topside surface and a bottomside surface. A stress structure is mounted to one of the topside surface or bottomside surface of the thin membrane. The stress structure induces a bending of the thin membrane which defines a normal state for the thin membrane. Piezoresistors are supported by the thin membrane. In response to an applied pressure, the thin membrane is bent away from the normal state and a change in resistance of the piezoresistors is indicative of the applied pressure.