Capacitive Acceleration Sensor with Staggered Bending Elastic Beams
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for preparing capacitive acceleration sensors with sandwich structures are complex, costly, and suffer from nonuniformity and residual stress issues, limiting sensitivity and accuracy.
Innovation Solution
A method involving anisotropic etching and photolithography to form staggered bending elastic beams on a SOI substrate, with anti-overloading bumps and damping grooves, allowing for a simpler bonding process and precise control over beam thickness and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bulk silicon micro-mechanical machining is used to prepare sandwich capacitive acceleration sensors, then detection accuracy can be improved, but the fabrication process becomes complex and costly
Solution Approach 1:
The sensor structure is divided into separate components (seismic mass, elastic beams, electrode plates) that are fabricated independently on different silicon wafers and then bonded together. This segmentation allows each component to be optimized separately while simplifying the overall fabrication process compared to monolithic bulk silicon machining.
Solution Approach 2:
A middle structural layer containing the seismic mass and elastic beams is introduced as an intermediary component between the first and second electrode structural layers. This middle layer acts as a mediator that can be independently fabricated and bonded, simplifying the overall structure and reducing fabrication complexity while maintaining detection accuracy.
2Reliability
If conventional methods are used to prepare anti-overloading bumps on electrode plates, then sensor protection is achieved, but the bonding process becomes complicated
Solution Approach 1:
Anti-overloading bumps are fabricated in advance on the middle structural layer during the initial etching and formation stages, before the bonding process. This preliminary action ensures protection features are already in place and properly positioned, eliminating the need for complex post-bonding adjustments or additional bonding steps.
Solution Approach 2:
The middle structural layer with pre-formed anti-overloading bumps serves itself by providing protection features that are automatically positioned and integrated during the bonding process, without requiring separate complex bonding operations for the bumps themselves.
3Strength
If L-shaped beams are used in the sensor structure, then structural strength is improved, but the sensor chip area is excessively occupied
Solution Approach 1:
The elastic beams are designed with a bent configuration that utilizes the third dimension (vertical height) rather than only occupying horizontal chip area. The beams extend vertically from the seismic mass to connect with electrode plates, providing structural strength while minimizing the footprint on the sensor chip surface.
Solution Approach 2:
Thin elastic beam structures are used that provide sufficient mechanical strength and flexibility while occupying minimal space. The beams are designed as thin film structures that can bend and deform elastically, providing the necessary structural support without excessive area occupation on the chip.
4Manufacturing precision
If boron-doped self-stop method is used to prepare symmetrical beam-mass structure, then etching control is improved, but residual stress affects sensor performance
Solution Approach 1:
The boron-doped self-stop method is replaced by extracting the etching control function to a dedicated etch-stop layer (such as a silicon oxide layer) that is specifically designed for this purpose. This separation removes the harmful residual stress associated with boron doping while maintaining precise etching control through the etch-stop layer's well-defined etching characteristics.
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 approach simplifies the sensor fabrication process, reduces sensor size, enhances sensitivity, and stabilizes performance by ensuring accurate beam thickness and distribution, enabling flexible sensitivity adjustment.
Implementation Method 1
performing etching at two surfaces of a SOI substrate having a double device layer based on an anisotropic etching method, causing the two surfaces to be concave, respectively
Implementation Method 2
A capacitive acceleration sensor is provided with a fixed electrode and a movable electrode on a seismic mass, when the mass is displaced by acceleration, the distance between the movable electrode and the fixed electrodes is changed, thereby causing the capacitance value between them to be changed
Implementation Method 3
capacitive acceleration sensor with a bending elastic beam
Data Source
AI summary
The present invention provides a capacitive acceleration sensor with a bending elastic beam and a preparation method. The sensor at least includes a first electrode structural layer, a middle structural layer and a second electrode structural layer; wherein the first electrode structural layer and the second electrode structural layer are provided with an electrode lead via-hole, respectively; the middle structural layer includes: a frame formed on a SOI silicon substrate with a double device layers, a seismic mass whose double sides are symmetrical and a bending elastic beam with one end connected to the frame and the other end connected to the seismic mass, wherein anti-overloading bumps and damping grooves are symmetrically provided on two sides of the seismic mass, and the bending elastic beams at different planes are staggered distributed and are not overlapped with each other in space. Since the bending times, the total length and the total width of the bending elastic beam can be prepared as needed, capacitive acceleration sensors with different sensitivities can be manufactured according to the present invention, and the manufacturing has high flexibility.