Fully Symmetrical MEMS Electrode Structures for Offset Control
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Solution Overview
Problem
Existing MEMS sensors suffer from asymmetrical designs that lead to changes in sensor offset and quadrature errors due to stress-induced rotation of fixed finger anchors, affecting accuracy and performance.
Innovation Solution
Implementing fully symmetrical sensing structures in MEMS devices, where fixed fingers are anchored symmetrically and aligned with moveable fingers, reducing stress-induced offset and quadrature errors through symmetric layouts and anchor co-alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If asymmetrical sensing structures are used in MEMS sensors, then device complexity is reduced and ease of manufacture is improved, but sensor offset performance deteriorates and stress-induced quadrature errors increase
Solution Approach 1:
The patent applies asymmetry in reverse - it deliberately introduces symmetry into the sensing structure to counteract the harmful effects of stress-induced asymmetry. The fixed fingers are arranged symmetrically with respect to the movable fingers, and anchors are positioned symmetrically to ensure that stress effects are evenly distributed and cancel out, thereby maintaining measurement precision while remaining manufacturable
2Device complexity
If fixed fingers are anchored asymmetrically, then device complexity is reduced, but stress-induced rotation of anchors causes changes in sensor offset and quadrature errors
Solution Approach 1:
The patent uses symmetry (the opposite of asymmetry) to resolve this contradiction. By arranging fixed fingers and their anchors symmetrically with respect to movable fingers, the design ensures that stress-induced rotations affect symmetric elements equally, causing errors to cancel out rather than accumulate, thereby improving reliability without significantly increasing device complexity
3Measurement precision
If fully symmetrical sensing structures are implemented, then offset performance and accuracy are improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies segmentation by dividing the sensing structure into symmetric segments - fixed fingers are divided into multiple elements arranged symmetrically on either side of the movable fingers. This segmentation allows the complex symmetrical structure to be built from repeating units, reducing manufacturing complexity while maintaining the beneficial symmetry for offset performance
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 fully symmetrical designs significantly improve offset performance and reduce stress-induced errors, enhancing the accuracy and reliability of MEMS sensors under package and external stress conditions.
Implementation Method 1
the sensing structure, such as a capacitive sensing structure having moveable fingers attached to the proof mass and fixed fingers anchored to a substrate. The moveable fingers and the fixed fingers can be interdigitated to form comb finger sets that serve to sense capacitance changes arising from the proof mass moving relative to the substrate.
Data Source
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AI summary
Fully symmetric sensing structures for MEMS devices are disclosed herein. In certain embodiments, a MEMS sensor includes a proof mass that moves in a first direction. The proof mass includes moveable fingers that move with the proof mass. The MEMS sensor further includes fixed fingers that are fixed with respect to the moveable fingers, and the fixed fingers and moveable fingers serve to detect movement of the proof mass. For example, the moveable fingers and the fixed fingers can be interdigitated to form a comb finger set for sensing changes in capacitance arising from movement of the proof mass relative to a substrate. A layout of the fixed fingers is fully symmetric in at least the first direction.