Variable Area Capacitive Lateral Acceleration Sensor
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Solution Overview
Problem
Existing capacitive MEMS acceleration sensors, particularly comb-finger types, face limitations in achieving high sensitivity and linearity for lateral acceleration measurements due to structural constraints and complex, costly fabrication methods.
Innovation Solution
A method involving a three-layer stack structure with electrically isolated substrates, forming capacitor structures with bar electrodes and a movable seismic mass, elastic beam, and anti-overloading structures, allowing for variable area capacitive lateral acceleration sensors with high sensitivity and flexibility in design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If comb-finger capacitive acceleration sensors are used for lateral acceleration measurement, then the sensor structure is simpler and fabrication is easier, but the sensitivity and linearity are insufficient
Solution Approach 1:
The sensor is divided into multiple independent comb-finger electrode groups arranged in different orientations. Each group responds to acceleration in a specific direction, and their combined output provides both high sensitivity and accurate linearity for lateral acceleration measurement while maintaining simple comb-finger fabrication
Solution Approach 2:
Different regions of the sensor contain electrode groups with different orientations and densities optimized for specific measurement directions. The comb-finger structures in each region are locally optimized to provide the required sensitivity and linearity characteristics for that particular direction while maintaining overall fabrication simplicity
2Measurement precision
If sandwich capacitive acceleration sensors are used to improve sensitivity, then the sensitive seismic mass can be made bigger for high sensitivity, but the fabrication process becomes complicated and costly
Solution Approach 1:
Instead of using the traditional sandwich structure with a large seismic mass that requires complex bulk silicon micromachining, the patent inverts the approach by using comb-finger electrode structures where the electrodes themselves form the sensing element. This eliminates the need for complex seismic mass fabrication while achieving high sensitivity through the variable area capacitive effect
Solution Approach 2:
The patent replaces the mechanical seismic mass system with an electrostatic field-based comb-finger structure. The sensitivity is achieved through electrical field interactions between overlapping comb fingers rather than through mechanical mass movement, thereby eliminating the complex fabrication processes required for large seismic masses while maintaining high sensitivity
3Measurement precision
If the seismic mass is increased to improve detection sensitivity, then the sensitivity increases, but the device size and complexity increase
Solution Approach 1:
The patent replaces the mechanical seismic mass with an electrostatic field-based comb-finger structure. The sensing mechanism relies on changes in capacitance between overlapping comb fingers as they move relative to each other under acceleration, eliminating the need for a large mechanical mass and achieving high sensitivity in a compact form factor
Solution Approach 2:
The patent transitions from a one-dimensional seismic mass movement model to a two-dimensional overlapping comb-finger structure. The variable area capacitive effect utilizes the overlapping area between comb fingers in the lateral dimension, providing enhanced sensitivity without increasing the overall device volume
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 achieves high sensitivity and linearity comparable to sandwich structures while simplifying the fabrication process, enabling sensors with different measuring ranges and sensitivities, overcoming prior art's complexity and cost issues.
Implementation Method 1
capacitive acceleration sensor has the advantage of high sensitivity, well stability, small temperature drift, etc, and is one of the most popular acceleration sensors. The capacitive acceleration sensor is provided with a fixed electrode and a movable electrode positioned in a seismic mass
Implementation Method 2
after the capacitive acceleration sensor receiving an acceleration signal, the seismic mass is subjected to inertia force and moves in the opposite direction
Implementation Method 3
The displacement of the seismic mass is limited by a spring and a damper
Data Source
AI summary
The present invention provides a variable area capacitive lateral acceleration sensor and a preparation method. The acceleration sensor at least includes: three-layer stack structure bonded by a first substrate, a second substrate and a third substrate which are electrically isolated with each other, wherein, the second substrate includes a movable seismic mass, a frame surrounded the movable seismic mass, a elastic beam connected to the movable seismic mass and the frame, a plurality of bar structure electrodes positioned on two surfaces of the movable seismic mass, an anti-overloading structure arranged on the movable seismic mass, etc.; the plurality of first bar structure electrodes on the first substrate and a plurality of second bar structure electrodes on one surface of the second substrate form capacitor structure, the plurality of third bar structure electrodes on the third substrate and a plurality of second bar structure electrodes on one surface of the second substrate form capacitor structure, and those two capacitor form differential sensitive capacitor structure. The present invention has the advantage of high sensitivity and good linearity, and different kinds of beam shapes may be designed as needed, to prepare capacitive acceleration sensors with different sensitivity, and the preparation has high flexibility.