MEMS Sensor Offset Anchor Load Rejection
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Solution Overview
Problem
MEMS inertial sensors, such as accelerometers and gyroscopes, face accuracy and sensitivity issues due to manufacturing tolerances and external stresses, which cause shifts in the location of proof masses relative to sense electrodes, affecting capacitance measurements and overall performance.
Innovation Solution
A microelectromechanical (MEMS) device with a suspended spring-mass system where anchoring masses are bonded to both the cap and substrate layers with offset bonds, allowing rotational displacement of anchoring masses to counteract external forces, maintaining the spring-mass system's alignment and minimizing angle deviation within the MEMS layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional vertically-stacked anchor bonds are used to connect cap and substrate layers, then manufacturing simplicity is maintained, but external stresses cause anchor displacement and proof mass misalignment leading to measurement errors
Solution Approach 1:
The patent applies asymmetry by offsetting the bond locations between the cap layer and substrate layer anchors. Instead of vertically stacking bonds directly above each other, the cap layer bonds are positioned at different lateral locations than the substrate layer bonds. This asymmetric configuration creates a rotational degree of freedom that allows the anchor to counteract external stresses through rotation, maintaining proof mass alignment and measurement accuracy.
2Measurement precision
If offset anchor bonds are implemented to counteract external forces, then alignment accuracy is improved, but manufacturing complexity increases due to precise bond location requirements
Solution Approach 1:
The patent incorporates the offset bond configuration directly into the anchor structure design during manufacturing. The offset distances are predetermined based on expected stress conditions, and the bonds are formed at these pre-calculated locations. This preliminary design approach eliminates the need for complex real-time adjustments or post-manufacturing calibration, making the manufacturing process more straightforward despite the offset requirement.
3Strength
If rigid anchor connections are used to maintain structural stability, then mechanical strength is improved, but stress-induced displacement increases causing proof mass location shifts
Solution Approach 1:
The patent transforms the static, rigid anchor connection into a dynamic structure that can rotate in response to external stresses. The offset bond configuration creates a lever arm that converts lateral stress forces into rotational motion, allowing the anchor to dynamically adjust its orientation. This dynamic response maintains the proof mass position stability while still providing structural strength through the offset bond geometry.
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 configuration ensures that the MEMS inertial sensor remains substantially aligned, with less than a 5% angle deviation, thereby maintaining accuracy and sensitivity by balancing external forces and maintaining the correct capacitance measurements.
Implementation Method 1
the anchoring masses are bonded to the cap layer and the substrate layer at offset locations such that when a force is applied to the cap layer, the anchoring masses rotate about the standoffs
Implementation Method 2
This configuration ensures that the MEMS inertial sensor remains substantially aligned, with less than a 5% angle deviation, thereby maintaining accuracy and sensitivity by balancing external forces
Implementation Method 3
maintaining the spring-mass system's alignment and minimizing angle deviation within the MEMS layer
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A MEMS sensor includes a MEMS layer, a cap layer, and a substrate layer. The MEMS layer includes a suspended spring-mass system that moves in response to a sensed inertial force. The suspended spring-mass system is suspended from one or more anchors. The anchors are coupled to each of the cap layer and the substrate layer by anchoring components. The anchoring components are offset such that a force applied to the cap layer or the substrate layer causes a rotation of the anchor and such that the suspended spring-mass system substantially remains within the original MEMS layer.