MEMS Sensor Suspension Structure for Stress Isolation
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Solution Overview
Problem
MEMS accelerometers are prone to measurement errors due to stress and deformations caused by temperature variations and environmental factors, leading to unwanted modifications in sensing capacitances and errors in acceleration detection.
Innovation Solution
The sensing structure is mechanically coupled to the substrate via a shared suspension structure, which ensures that both mobile and fixed electrodes deform uniformly, making the system insensitive to substrate deformations and reducing zero-g level drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sensing structure is directly coupled to the substrate, then the manufacturing process is simple, but the measurement precision deteriorates due to stress sensitivity
Solution Approach 1:
The sensing structure is segmented from the substrate through the introduction of a suspension structure with elastic suspension elements. This segmentation allows the sensing structure to be mechanically isolated from substrate deformations while maintaining electrical functionality, thereby reducing stress sensitivity without complicating the manufacturing process.
Solution Approach 2:
The suspension structure acts as an intermediary element between the substrate and the sensing structure. The elastic suspension elements transmit necessary mechanical support while filtering out harmful substrate deformations, serving as a mediator that protects the sensing capacitors from stress-induced measurement errors.
2Stability of the object's composition
If the sensing structure is rigidly coupled to the substrate, then the structural stability is high, but the drift in electrical characteristics increases due to temperature variations
Solution Approach 1:
The coupling between the substrate and sensing structure is made dynamic rather than rigid. The elastic suspension elements provide a flexible connection that allows the sensing structure to adapt to thermal expansions and contractions independently, maintaining electrical characteristic stability while preserving structural integrity.
Solution Approach 2:
The mechanical coupling parameters are changed from rigid to elastic. By introducing elastic suspension elements with appropriate stiffness characteristics, the system allows controlled deformation under thermal stress while maintaining operational stability, thereby reducing zero-g level drift.
3Object-affected harmful factors
If the sensing structure is isolated from the substrate, then the stress sensitivity is reduced, but the device complexity increases
Solution Approach 1:
The suspension structure employs thin elastic suspension elements that provide effective mechanical isolation from substrate stress while occupying minimal space. These flexible elements achieve stress decoupling without adding significant structural complexity or volume to the device.
Solution Approach 2:
The suspension structure serves multiple functions simultaneously: it provides mechanical support, enables electrical connections, allows thermal expansion compensation, and isolates the sensing structure from substrate stress. This multi-functionality reduces the need for additional components, thereby limiting the increase in device complexity.
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 significantly minimizes drifts in electrical characteristics, maintaining stability and accuracy in acceleration detection despite temperature variations and mechanical stress, without altering the sensing mechanism or manufacturing process.
Implementation Method 1
Elastic coupling elements (8), arranged within the window (4), between the inertial mass (3) and the rotor anchorage structure (6)
Data Source
AI summary
A MEMS sensor device provided with a sensing structure, having: a substrate with a top surface extending in a horizontal plane; an inertial mass, suspended over the substrate; elastic coupling elements, elastically connected to the inertial mass so as to enable inertial movement thereof with respect to the substrate as a function of a quantity to be detected along a sensing axis belonging to the horizontal plane; and sensing electrodes, capacitively coupled to the inertial mass so as to form at least one sensing capacitor, a value of capacitance of which is indicative of the quantity to be detected. The sensing structure moreover has a suspension structure, to which the sensing electrodes are rigidly coupled, and to which the inertial mass is elastically coupled through the elastic coupling elements; the suspension structure is connected to an anchorage structure, fixed with respect to the substrate, by means of elastic suspension elements.