MEMS Elastic Elements for Thermo-Mechanical Stress Compensation
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Solution Overview
Problem
Microelectromechanical structures, such as capacitive accelerometers, suffer from performance degradation due to thermo-mechanical stress accumulated in the substrate during manufacturing, packaging, and operation, leading to offset and sensitivity drift in acceleration sensing.
Innovation Solution
Incorporating and adjusting elastic elements between the proof mass and anchors in the microelectromechanical structure to reduce displacement caused by thermo-mechanical stress, with the geometry and configuration of these elastic elements being specifically designed to compensate for the stress-induced offset and sensitivity drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If elastic elements are incorporated to compensate thermo-mechanical stress, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent modifies the geometric parameters (length, width, thickness) and material properties of the elastic elements to optimize their stress compensation capability. By adjusting these parameters, the elastic elements can be designed to provide precise compensation for thermo-mechanical stress while maintaining a relatively simple structure, thus improving measurement precision without excessive complexity increase.
Solution Approach 2:
The patent employs composite material structures for the elastic elements, combining different materials with complementary properties to achieve both high stress compensation efficiency and structural simplicity. The composite structure allows the elastic elements to respond differently to thermal and mechanical stresses, enabling precise offset compensation while keeping the overall device complexity manageable.
2Reliability
If elastic elements are adjusted to reduce proof mass displacement, then reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates preliminary design stages where the elastic element geometry is pre-calculated and optimized to compensate for expected thermo-mechanical stresses. By performing stress analysis and geometric optimization before manufacturing, the design can accommodate manufacturing tolerances while still achieving reliable stress compensation, reducing the stringency of post-manufacturing precision requirements.
Solution Approach 2:
The patent applies different geometric characteristics to different regions of the elastic elements based on local stress distribution. By optimizing each region's properties (length, width, thickness) according to the specific stress patterns it experiences, the design achieves reliable overall compensation while allowing localized variations in manufacturing precision that are acceptable within tolerance ranges.
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
The solution effectively reduces the impact of thermo-mechanical stress on the microelectromechanical structure, improving the accuracy and reliability of acceleration sensing by maintaining consistent capacitor gap variations and minimizing sensitivity drift.
Implementation Method 1
The elastic elements are coupled between the proof mass and the anchor to support the proof mass. Geometry and configuration of these elastic elements are adjusted to reduce a displacement of the proof mass caused by thermo-mechanical stress.
Implementation Method 2
Thermo-mechanical stress may introduce an intrinsic offset or drift to the output even though no out-of-plane acceleration is applied. Such asymmetric gap variations are incorporated into the final output from the interface circuit, and lead to an offset in the sensed acceleration and a sensitivity drift for the accelerometer 100.
Data Source
AI summary
The invention relates to a microelectromechanical structure, and more particularly, to systems, devices and methods of compensating the effect of the thermo-mechanical stress by incorporating and adjusting elastic elements that are used to couple a moveable proof mass to anchors. The proof mass responds to acceleration by displacing and tilting with respect to a moveable mass rotational axis. The thermo-mechanical stress is accumulated in the structure during the courses of manufacturing, packaging and assembly or over the structure's lifetime. The stress causes a displacement on the proof mass. A plurality of elastic elements is coupled to support the proof mass. Geometry and configuration of these elastic elements are adjusted to reduce the displacement caused by the thermo-mechanical stress.