Microelectromechanical Inertial Sensor with Segmented Damping
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Solution Overview
Problem
The challenge in fabricating multi-sensor modules using Wafer Level Packaging (WLP) lies in establishing different operating pressures and gas compositions for various sensor systems, as existing techniques cannot arbitrarily adjust pressure values and gas compositions, leading to inadequate damping for high-quality sensors like resonant rotation rate sensors and insufficient operation for low-quality sensors like acceleration sensors.
Innovation Solution
Incorporating a damping structure within the inertial sensor, specifically designed to reduce the quality factor at low cavity pressures, and using getter materials to adjust gas pressures and compositions in separate cavities, allowing for the operation of sensors with varying quality factors in a single multi-sensor module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Wafer Level Packaging is used to integrate multiple sensor units, then production efficiency and cost are improved, but the ability to establish different operating pressures and gas compositions for different sensor types deteriorates
Solution Approach 1:
The patent divides the sealed cavity into multiple independent sub-cavities, each capable of having different gas compositions and pressures. This segmentation allows different sensor units to operate under their optimal conditions while maintaining the benefits of WLP integration.
Solution Approach 2:
Different regions of the cavity are provided with different gas compositions and pressures tailored to specific sensor requirements. For example, acceleration sensors receive higher pressure gas for damping, while resonant sensors receive lower pressure gas to minimize damping, with each region optimized for its local sensor's needs.
2Measurement precision
If high quality factor is maintained for resonant sensors, then measurement precision is improved, but damping becomes insufficient for acceleration sensors operating at low pressure
Solution Approach 1:
The cavity is segmented into separate regions where resonant sensors operate in low-pressure zones maintaining high quality factors, while acceleration sensors operate in higher-pressure zones providing sufficient damping. This spatial segmentation resolves the contradiction between precision and damping requirements.
Solution Approach 2:
Different local regions of the cavity are optimized with different gas pressures: low pressure regions for resonant sensors to maintain high Q-factors and measurement precision, and high pressure regions for acceleration sensors to ensure adequate damping and operational reliability.
3Reliability
If gas pressure is increased for acceleration sensor damping, then damping performance is improved, but quality factor of resonant sensors deteriorates due to excessive damping
Solution Approach 1:
The patent segments the sealed cavity into multiple independent sub-cavities or regions, allowing acceleration sensors to be exposed to higher gas pressures for improved damping while resonant sensors remain in lower pressure environments to maintain their quality factors.
Solution Approach 2:
Different local regions within the sealed cavity are provided with different gas pressures optimized for their specific sensor types: higher pressure in regions containing acceleration sensors for adequate damping, and lower pressure in regions containing resonant sensors to preserve their quality factors and measurement precision.
4Ease of manufacture
If uniform gas composition is provided in all cavities during WLP, then manufacturing simplicity is maintained, but the ability to provide different operating conditions for different sensor types deteriorates
Solution Approach 1:
The manufacturing process is segmented into stages: first forming a sealed cavity with uniform gas composition through WLP for ease of manufacture, then subsequently dividing the cavity into multiple regions with different gas compositions and pressures to provide different operating conditions for different sensor types.
Solution Approach 2:
The WLP process is performed first with uniform gas composition to simplify manufacturing, and then subsequent actions are taken to create different gas environments in different regions. This preliminary action maintains manufacturing simplicity while enabling later differentiation of operating conditions.
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
Enables the operation of high-quality sensors like resonant rotation rate sensors and low-quality sensors like acceleration sensors in a single device, with sufficient damping at low pressures without compromising sensitivity, by adjusting gas pressures and compositions using getter materials and a damping structure.
Implementation Method 1
damping structure which is designed to reduce the quality factor of the inertial sensor at low cavity pressures
Implementation Method 2
adjusting the gas pressure and/or the gas composition in the cavity or in selected cavities by using getter materials
Data Source
AI summary
The present invention relates to an inertial sensor, preferably an acceleration sensor or multi-axis acceleration sensor as a microelectromechanical construction element, said sensor comprising a housing with at least one first gas-filled cavity in which a first detection unit is disposed moveably relative to the housing for detection of an acceleration to be detected, wherein the inertial sensor comprises a damping structure.