MEMS Anchors With Shell Stiffening For Beam Deflection
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Solution Overview
Problem
There is a need for anchoring structures in mechanical light modulators that can prevent or minimize undesired deflections of compliant beams and shutters, which are prone to deflection due to mechanical shock, attraction to the substrate, and stresses in the films, while being fabricated using MEMS techniques for fast, bright, and low-powered displays.
Innovation Solution
The development of a MEMS device with a substrate-based anchoring structure featuring a shell structure with a non-horizontal elevating portion, a horizontal shelf portion, and non-horizontal shell stiffening portions, where the normal vectors of the stiffening portions are substantially different, providing enhanced stiffness and resistance to deflections, and the beam is manufactured from materials that can be different from or the same as the shelf portion, with the beam being coupled to the shelf and extending from the anchor structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional anchor structures are used, then the device can be fabricated using standard MEMS techniques, but undesired deflections of beams and shutters occur due to mechanical shock, attraction, and film stresses
Solution Approach 1:
The anchor structure transitions from a conventional planar configuration to a three-dimensional shell structure with elevating portions that extend vertically from the substrate. This dimensional change creates a more rigid support that resists deflection forces while maintaining compatibility with MEMS fabrication processes.
Solution Approach 2:
The shell structure incorporates curved surfaces and non-horizontal elevating portions rather than straight vertical walls. This curvature distributes stress more effectively and increases the structural rigidity of the anchor, reducing beam and shutter deflection while being formable through standard MEMS techniques.
2Reliability
If the anchor structure is made stiffer to prevent deflection, then beam and shutter stability improves, but the complexity of the anchor structure increases
Solution Approach 1:
The anchor structure is divided into distinct functional portions: a base portion attached to the substrate, elevating portions that extend upward, and a shell portion that provides lateral support. This segmentation allows each portion to be optimized for its specific function while maintaining overall structural efficiency and manufacturability.
Solution Approach 2:
The anchor utilizes a shell structure that provides high stiffness-to-weight ratio and stress distribution. The thin-walled shell geometry resists deflection forces effectively while using minimal material, reducing the overall complexity compared to solid rigid structures.
3Illumination intensity
If the beam height is increased to improve light modulation performance, then the beam can modulate light more effectively, but the beam becomes more prone to deflection
Solution Approach 1:
The shell structure's curved geometry provides distributed structural support that counteracts the increased deflection tendency of taller beams. The curvature creates a more rigid support framework that maintains beam stability even when beam height is increased for improved light modulation performance.
Data Source
AI summary
The invention relates to an improved apparatus and method for the design and manufacture of MEMS anchoring structures for light modulators in order to address the stresses of beams mounted on them.