MEMS Accelerometer Anchor Tracking via Compensation Capacitors
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Solution Overview
Problem
Conventional MEMS accelerometers are susceptible to stress-induced displacement of anchors, which can lead to inaccurate sensing of in-plane accelerations due to packaging stress and thermal variations, causing non-zero signals that are not indicative of actual acceleration.
Innovation Solution
The implementation of a micro-electro-mechanical system (MEMS) accelerometer with a plurality of compensation structures connected to respective anchors, which form compensation capacitors to detect and compensate for anchor displacement, thereby isolating the displacement from the sensed motion of the proof mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional MEMS accelerometers are used without compensation structures, then the device complexity is low, but the measurement precision deteriorates due to stress-induced anchor displacement
Solution Approach 1:
The sensor is segmented into distinct functional components: proof mass for acceleration sensing, anchors for structural support, and compensation structures for stress detection. Each component independently performs its specific function, allowing the anchor displacement to be measured and compensated separately from the acceleration signal, thereby improving measurement precision without excessive complexity
Solution Approach 2:
Compensation structures serve as intermediary elements that detect anchor displacement caused by stress. These structures transfer the anchor position information to the readout circuitry, enabling the system to distinguish between actual acceleration signals and artifacts caused by anchor displacement, thus improving measurement accuracy
2Measurement precision
If compensation structures are added to detect anchor displacement, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The compensation structures are merged with the existing anchor structure, sharing common elements such as the substrate connection and readout circuitry. This integration allows the compensation function to be added without requiring completely separate systems, thereby improving measurement precision while limiting the increase in device complexity
Solution Approach 2:
The compensation structures serve multiple functions: they detect anchor displacement, provide a reference for stress compensation, and maintain structural integrity. This multi-functionality reduces the need for additional dedicated components, improving measurement precision while controlling device complexity
3Stability of the object's composition
If anchors are rigidly connected to substrate, then the stability improves, but the measurement precision deteriorates due to stress-induced displacement
Solution Approach 1:
The compensation structures provide feedback information about anchor displacement to the signal processing system. This feedback enables real-time compensation of stress-induced errors, allowing the anchors to remain rigidly connected for stability while maintaining measurement precision through active correction of displacement artifacts
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 enhances the accuracy of MEMS inertial sensors by separately detecting and compensating for anchor displacement, reducing the impact of stress-related errors and improving the overall performance of the sensor.
Implementation Method 1
a first compensation electrode rigidly connected to the first anchor and a second fixed electrode connected to the substrate, and detecting a second displacement of the second anchor using a second lateral compensation capacitor
Implementation Method 2
one or more sense electrodes connected to the proof mass and forming one or more sense capacitors with at least one of the plurality of fixed electrodes, wherein the one or more sense capacitors are configured to sense lateral acceleration of the proof mass
Data Source
AI summary
A microelectromechanical systems (MEMS) accelerometer is described. The MEMS accelerometer may comprise a proof mass configured to sense accelerations in a direction parallel the plane of the proof mass, and a plurality of compensation structures. The proof mass may be connected to one or more anchors through springs. The compensation structures may be coupled to the substrate of the MEMS accelerometer through a rigid connection to respective anchors. A compensation structure may comprise at least one compensation electrode forming one or more lateral compensation capacitors. The compensation capacitor(s) may be configured to sense displacement of the anchor to which the compensation structures is connected.