Slotted MEMS Sense Electrodes for Crack Resistance
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Solution Overview
Problem
MEMS sensors, such as accelerometers and gyroscopes, face challenges in maintaining accurate capacitance measurements due to environmental stressors like temperature changes, which can cause cracking and deformation of sense electrodes, leading to inaccurate readings of motion parameters.
Innovation Solution
The implementation of slotted sense electrodes with specific patterns, such as T-slot, Y-slot, spiral, and recessed-slot designs, which guide cracking and reduce the impact of environmental stress on the sensor's capacitive sensing, maintaining electrical conductivity and capacitive resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sense electrodes are made continuous to maintain electrical conductivity, then electrical conductivity is improved, but cracking and deformation under environmental stress worsen measurement accuracy
Solution Approach 1:
The sense electrode is divided into multiple discrete segments rather than being continuous. These segmented electrodes maintain electrical conductivity through appropriate spacing and sizing while reducing stress concentration that causes cracking. The segmentation allows the electrode structure to better accommodate thermal expansion and mechanical stress without compromising measurement accuracy.
Solution Approach 2:
Different regions of the sense electrode are designed with different properties - some areas have larger electrode segments for better conductivity while other areas have smaller segments or gaps to reduce stress concentration. This local variation in electrode quality optimizes both electrical conductivity and resistance to environmental stress-induced cracking.
2Measurement precision
If sense electrodes are made larger to improve capacitive sensing, then capacitive resolution is improved, but susceptibility to environmental stress and cracking worsens
Solution Approach 1:
Large sense electrodes are divided into multiple smaller segmented electrodes. This segmentation reduces the overall stress concentration on any single electrode region while maintaining the total capacitive sensing area. The distributed segmentation allows the sensor to achieve high capacitive resolution without the vulnerability of large continuous electrodes to environmental stress and cracking.
3Volume of moving object
If sense electrodes are made thinner to reduce device size, then device compactness is improved, but mechanical strength and resistance to cracking worsen
Solution Approach 1:
Thin sense electrodes are designed with a segmented pattern rather than being continuous. This segmentation creates a more mechanically robust structure that can better withstand bending and stress despite the reduced thickness. The gaps between segments reduce stress concentration points, thereby improving crack resistance while maintaining device compactness.
4Reliability
If slots are added to sense electrodes to guide cracking, then resilience to environmental conditions is improved, but electrical conductivity and capacitive sensing are worsened
Solution Approach 1:
The sense electrode is segmented into multiple discrete regions with controlled spacing. This segmentation naturally guides stress distribution and cracking patterns without requiring additional slot features. The segmented design maintains adequate electrical conductivity through the distributed electrode structure while improving environmental resilience by preventing uncontrolled cracking propagation.
Solution Approach 2:
Different regions of the sense electrode have different segment sizes and spacing to optimize local stress distribution. This local variation in electrode quality provides crack guidance and stress management in critical areas while maintaining adequate capacitive sensing capability in measurement regions, thereby improving environmental resilience without significantly compromising sensing accuracy.
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
These designs enhance the resilience of MEMS sensors to environmental conditions, ensuring accurate and stable capacitance measurements over time, even under extreme temperature variations, by limiting the impact of cracking and maintaining capacitive sensing integrity.
Implementation Method 1
a first capacitive sensing element is formed between the movable component and the first sense electrode, wherein the first capacitive sensing element is configured to be responsive to the motion of the movable component along the first axis
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A MEMS sensor includes a proof mass that is suspended over a substrate. A sense electrode is located on a top surface of the substrate parallel to the proof mass, and forms a capacitor with the proof mass. The sense electrodes have a plurality of slots that provide improved performance for the MEMS sensor. A measured value sensed by the MEMS sensor is determined based on the movement of the proof mass relative to the slotted sense electrode.