Suspended Membrane Fabrication via Peripheral Trench Etch Stop
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Solution Overview
Problem
Existing methods for producing suspended membranes in MEMS/NEMS struggle with precision in dimension and shape control, often resulting in circular shapes and mechanical property degradation due to anchoring studs and central etching plug defects.
Innovation Solution
A method involving trench formation around a sacrificial layer, filling with an etch stop material, and selective etching to create suspended membranes of any shape with improved mechanical properties, allowing for precise control over dimensions and reduced mechanical property degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If etching is performed through a central opening to create suspended membranes, then suspended structures can be formed, but the plug material introduces defects that alter mechanical properties and the shape is constrained to circular
Solution Approach 1:
The patent removes the central plug from the manufacturing process entirely. Instead of etching through a central opening and leaving a plug, the method uses peripheral trenches to define the membrane boundary, allowing complete removal of sacrificial material without requiring any plug material to seal openings. This eliminates the defect source while maintaining the suspended membrane structure.
Solution Approach 2:
The patent segments the continuous sacrificial layer into regions defined by peripheral trenches. The sacrificial material is removed through multiple openings distributed around the periphery rather than a single central opening, allowing the membrane to be released without requiring a central plug. This segmentation approach enables precise dimensional control while avoiding manufacturing defects.
2Strength
If anchoring studs are distributed under the membrane, then structural support is provided, but the membrane mechanical properties are degraded
Solution Approach 1:
The patent completely removes anchoring studs from the membrane structure. The suspended membrane is supported solely by its peripheral boundary anchored to the substrate, eliminating the distributed anchoring studs that would otherwise compromise the membrane's mechanical properties and uniformity.
3Productivity
If etching rate depends on pH, temperature and composition, then etching can be controlled, but precise dimensional characterization becomes difficult
Solution Approach 1:
The patent performs preliminary patterning of trenches through the membrane layer before etching the sacrificial material. The trench depth and position are precisely defined in advance, establishing the final membrane dimensions before the etching process begins. This preliminary structuring decouples the dimensional definition from the etching rate variations, allowing precise dimensional control regardless of etching conditions.
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
Enables the production of suspended membranes with precise dimensions and shapes, reducing mechanical property degradation and allowing for flexible membrane designs, such as non-circular shapes, while maintaining high mechanical integrity.
Implementation Method 1
etching said portion of the first sacrificial layer with said etching agent through at least one opening made in the second layer
Data Source
AI summary
A method for producing a device with at least one suspended membrane, including the following steps: Producing a trench through a first sacrificial layer and a second layer deposited on the first sacrificial layer, the trench completely surrounding at least a portion of the first sacrificial layer and at least a portion of the second layer, filling all or a portion of the trench with at least one material capable of resisting at least one etching agent, and etching the portion of the first sacrificial layer with the etching agent through at least one opening made in the second layer, the portion of the second layer forming at least one portion of the suspended membrane.