Suspended Stator MEMS Z-Axis Sensor for Stress-Insensitive Detection
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Solution Overview
Problem
MEMS accelerometers are susceptible to measurement errors due to deformations in the detection structure caused by external stresses and environmental conditions, leading to undesired modifications in the output signal and inaccurate acceleration detection.
Innovation Solution
The detection structure is designed with stator electrodes arranged in a fully suspended manner relative to the substrate, using epitaxial silicon layers to form stator and inertial masses in a differential configuration, ensuring minimal deformation-induced changes in the relative distance between the electrodes and inertial mass, thereby maintaining accurate signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If stator electrodes are fixed directly to the substrate, then manufacturing is simplified, but measurement precision deteriorates due to substrate deformation under external stresses
Solution Approach 1:
The stator electrode structure is segmented into multiple components: a suspension structure with first and second suspension portions, and a stator electrode portion. This segmentation allows the electrode to be suspended above the substrate rather than directly fixed, isolating it from substrate deformation while maintaining manufacturability through modular construction
Solution Approach 2:
The suspension structure acts as an intermediary between the substrate and the stator electrode. It provides mechanical support while electrically coupling the stator electrode to the substrate through conductive material, while the suspended configuration prevents direct transmission of substrate deformation to the electrode
2Manufacturing precision
If substrate deformations occur under external stresses, then device stability is compromised, but manufacturing precision is maintained
Solution Approach 1:
The invention changes the physical state and spatial configuration of the stator electrode from a fixed planar position to a suspended three-dimensional configuration. This parameter change in spatial arrangement allows the electrode to maintain constant distance from the inertial mass despite substrate deformations, preserving measurement stability
3Reliability
If stator electrodes are arranged in suspended configuration, then insensitivity to substrate deformation is improved, but device complexity increases
Solution Approach 1:
The suspension structure and stator electrode are merged into an integrated suspended configuration where the first and second suspension portions connect to form a complete support structure. This merging reduces the number of separate components and simplifies the overall device while maintaining the insensitivity to substrate deformation
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 significantly reduces drift in the output signal by eliminating the effects of substrate deformations, ensuring stable and accurate acceleration detection regardless of external stresses or environmental conditions.
Implementation Method 1
The inertial mass is arranged suspended above a substrate, coupled to a corresponding rotor anchor (fixed to the same substrate) by means of elastic elements, which allow movement of the same inertial mass by the inertial effect.
Implementation Method 2
The detection structure of the MEMS accelerometer further comprises stator electrodes, which are fixed and integrally coupled to the substrate and are capacitively coupled to the rotor to form one or more detection capacitors (typically in differential configuration), whose capacitive variation is indicative of the quantity to be detected.
Implementation Method 3
The inertial mass is arranged suspended above a substrate, coupled to a corresponding rotor anchor (fixed to the same substrate) by means of elastic elements, which allow movement of the same inertial mass by the inertial effect.
Data Source
AI summary
A microelectromechanical sensor device has a detection structure, having: a substrate, with a top surface; an inertial mass, suspended above the top surface of the substrate and elastically coupled to a rotor anchor so as to perform an inertial movement relative to the substrate as a function of a quantity to be detected; and stator electrodes, integrally coupled to the substrate at respective stator anchors and capacitively coupled to the inertial mass so as to generate a differential capacitive variation in response to, and indicative of, the quantity to be detected. In particular, the inertial mass performs, as the inertial movement, a translation movement along a vertical axis orthogonal to the top surface of the substrate; and the stator electrodes are arranged in a suspended manner above the top surface of the substrate.