Suspended Membrane Pressure Sensor With Rounded Anchor Corners
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Solution Overview
Problem
Capacitive pressure sensors face challenges due to high tensile stress in tungsten membranes, leading to potential cracks and fractures, which can result in non-linearity and reliability issues across varying temperatures and pressures.
Innovation Solution
The introduction of rounded corners in the outer anchor trenches of capacitive pressure sensors, with a radius of at least 40 µm, helps mitigate stress concentrations, reducing the risk of membrane fracture and improving manufacturing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a suspended membrane structure is used in capacitive pressure sensors, then sensitivity and measurement capability are improved, but stress concentration at sharp corners leads to membrane rupture and reduced reliability
Solution Approach 1:
The patent applies curvature by replacing sharp corners with rounded corners at the anchor edge of the suspended membrane. This geometric modification eliminates stress concentration points while preserving the membrane's suspended structure and sensing capability, directly resolving the contradiction between measurement sensitivity and rupture resistance
2Ease of manufacture
If standard fabrication processes are used for suspended membranes, then manufacturing simplicity is maintained, but corner rounding is difficult to achieve with sufficient radius
Solution Approach 1:
The patent changes the fabrication parameters by using deep ultraviolet (DUV) lithography with a specific wavelength to achieve the desired corner radius. This parameter change enables precise corner rounding while maintaining compatibility with standard semiconductor fabrication processes, resolving the contradiction between manufacturing simplicity and corner radius precision
3Area of moving object
If membrane area is increased to improve measurement range, then pressure sensing capability is enhanced, but stress concentration at corners increases rupture risk
Solution Approach 1:
By rounding the corners of larger membranes, the patent enables increased membrane area for enhanced pressure sensing capability while simultaneously reducing stress concentration at the corners. This geometric modification allows the membrane to maintain both large area and high rupture resistance, resolving the contradiction between measurement range and reliability
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 effectively reduces stress concentrations, preventing membrane failure and anchor delamination, while allowing for more accurate and reliable pressure readings over a range of conditions.
Implementation Method 1
Capacitive pressure sensors and other devices having a suspended membrane
Data Source
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Figure 1A
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AI summary
A semiconductor device includes an integrated circuit, and a capacitive pressure sensor disposed over and electrically connected to the integrated circuit. The capacitive pressure sensor includes a first electrode, a cavity over the first electrode, and a second electrode including a suspended membrane over the cavity. The second electrode further includes electrically conductive anchor trenches laterally surrounding the cavity. The anchor trenches include an inner anchor trench and an outer anchor trench, wherein the outer anchor trench has rounded corners.