MEMS Acceleration Sensor Electrode Pairing for Bias Reduction
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Solution Overview
Problem
Miniaturized acceleration sensors, such as MEMS, face challenges in achieving accurate measurements due to production-related fluctuations in gap distances between electrode pairs, leading to varying etch depths and widths, which result in measurement bias caused by uneven etching liquid distribution during manufacturing.
Innovation Solution
The design involves two groups of excitation and detection electrode pairs with equal numbers, where the average distance between electrodes in one group is set to match the average distance in the other group, ensuring equal forces are exerted on the excitation mass in opposite directions, thereby reducing or eliminating measurement bias. This is achieved by arranging electrode pairs in a crosswise configuration to average out differences in gap widths caused by uneven etching liquid distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If miniaturized acceleration sensors are used to reduce size, then the sensor dimensions are reduced, but manufacturing precision deteriorates due to production-related fluctuations in gap distances
Solution Approach 1:
The sensor is divided into multiple electrode pairs, with each pair contributing to the overall measurement. By segmenting the sensing function across multiple pairs, the patent compensates for individual variations in gap distances through statistical averaging, thereby maintaining manufacturing precision while enabling miniaturization.
Solution Approach 2:
The patent changes the parameter of electrode pair configuration from a single pair to multiple pairs with specific geometric arrangements. This parameter change allows the system to tolerate variations in individual gap distances while maintaining overall measurement accuracy, resolving the contradiction between miniaturization and manufacturing precision.
2Productivity
If standard etching processes are used for manufacturing, then production efficiency is maintained, but measurement precision deteriorates due to uneven etching liquid distribution causing bias
Solution Approach 1:
The patent employs asymmetric arrangements of electrode pairs where pairs are positioned at different locations and orientations on the diaphragm. This asymmetric distribution ensures that uneven etching liquid distribution affects different pairs differently, and the combined effect averages out the bias, maintaining measurement precision while using standard etching processes.
Solution Approach 2:
The patent extends the electrode pair arrangement from a single plane or line to multiple dimensions across the diaphragm surface. By distributing pairs in two-dimensional space with varying orientations, the system captures and averages out etching variations from multiple spatial perspectives, eliminating bias while maintaining production efficiency.
3Measurement precision
If multiple electrode pairs are used to improve measurement reliability, then measurement precision is improved, but device complexity increases
Solution Approach 1:
Multiple electrode pairs serve the universal function of acceleration sensing simultaneously. Each pair contributes to the same measurement objective, and their combined output provides both improved precision and redundancy. This multi-functionality approach improves measurement precision without proportionally increasing device complexity.
Solution Approach 2:
The patent merges the output signals from multiple electrode pairs through electrical connection and signal processing. By combining the measurements from multiple pairs, the system achieves improved measurement precision while managing device complexity through integrated signal handling rather than independent processing of each pair.
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 approach simplifies the production of acceleration sensors with reduced bias, reduces manufacturing costs, and ensures more accurate acceleration measurements by maintaining consistent forces across electrode pairs, minimizing distortion in measurement results.
Implementation Method 1
the excitation electrodes and the detection electrodes associated with them form pairings, which exert equal forces on the excitation mass in opposite directions
Implementation Method 2
The change in the electric field between the electrodes allows the movement of the mass over time to be recorded
Data Source
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AI summary
The invention relates to an acceleration sensor (400) comprising an excitation mass (420) having excitation electrodes (430), which excitation mass is movably mounted over a substrate (410) along a movement axis (x) and comprising detection electrodes (440) which are permanently connected to the substrate (410) and allocated to the excitation electrodes (430). A first group of pairings (450) of excitation electrode (430) and allocated detection electrodes (440) is suitable for deflecting the excitation mass (420) along the movement axis (x) in a first direction (460). A second group of pairings (450) of excitation electrodes (430) and allocated detection electrodes (440) is suitable for deflecting the excitation mass (420) along the movement axis (x) in a second direction (465), which is opposite the first direction (460). The number of pairings (450) in the first group is equal to the number of pairings (450) in the second group. The averaged distance between excitation electrodes (430) and detection electrodes (440) of the pairings (450) of the first group corresponds to the averaged distance between excitation electrodes (430) and detection electrodes (440) of the pairings (450) of the second group.