Three-Axis Acceleration Sensor Chip Integration
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Solution Overview
Problem
Existing acceleration sensors have limitations in detecting accelerations in three perpendicular directions with sufficient sensitivity, particularly in achieving high detection accuracy and miniaturization.
Innovation Solution
The acceleration sensor integrates X, Y, and Z detection portions on a single chip, utilizing movable electrodes and beam structures to detect changes in electrostatic capacitance, allowing for enhanced sensitivity and miniaturization by arranging fixed electrodes to oppose movable electrodes in specific configurations and using pillar-like electrodes for electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a comb teeth-like sensor is used to detect accelerations in three perpendicular directions, then three-axis detection capability is achieved, but detection sensitivity is insufficient
Solution Approach 1:
The sensor is divided into three independent detection portions (X, Y, Z axes), each with its own movable electrode and beam structure. This segmentation allows each axis to be optimized independently for maximum sensitivity while maintaining three-axis detection capability. The X detection portion detects acceleration in the X direction, the Y detection portion detects acceleration in the Y direction, and the Z detection portion detects acceleration in the Z direction, with each portion having dedicated electrostatic capacitance measurement circuits.
Solution Approach 2:
The patent transitions from a planar comb teeth-like structure to a three-dimensional configuration with movable electrodes that can swing in multiple directions. The beam portions are arranged to enable movement in X, Y, and Z directions, creating a spatially distributed sensor structure that enhances detection sensitivity by utilizing three-dimensional space rather than a two-dimensional plane.
2Area of stationary object
If multiple detection portions are integrated on one chip, then chip size is reduced, but parasitic capacitance noise increases
Solution Approach 1:
The patent extracts and separates the electrostatic capacitance measurement circuits for each detection portion, with each circuit dedicated to measuring the capacitance of its corresponding movable electrode. This separation minimizes interference between measurement circuits and reduces parasitic capacitance effects. The first electrostatic capacitance measurement circuit is dedicated to the X detection portion, the second to the Y detection portion, and the third to the Z detection portion, allowing independent optimization of each measurement path.
Solution Approach 2:
The patent introduces fixed electrodes as intermediary elements between the movable electrodes and the measurement circuits. These fixed electrodes are positioned to minimize parasitic capacitance coupling while maintaining sufficient electrostatic field interaction for detection. The fixed electrodes serve as mediators that facilitate capacitance measurement while reducing direct parasitic coupling between adjacent detection portions on the integrated chip.
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 enhances detection sensitivity for accelerations in three directions, reduces parasitic capacitance noise, and facilitates miniaturization by sharing peripheral regions, thereby improving accuracy and reducing chip size.
Implementation Method 1
displacement of a mass body is detected from a change of an electrostatic capacitance between an electrode provided on the mass body and a fixed electrode
Data Source
AI summary
An acceleration sensor includes: an X detection portion (10) that detects acceleration in an X direction by swinging a first movable electrode (11) about a pair of beam portions (12a, 12b); a Y detection portion (20) that detects acceleration in a Y direction perpendicular to the X direction by swinging a second movable electrode (21) about a pair of beam portions (22a, 22b); and a Z detection portion (30) that detects acceleration in a Z direction by moving a third movable electrode (31), which is held by two pairs of beam portions (32a, 32b, 32c, 32d) in parallel in the vertical direction, characterized in that the X detection portion (10), the Y detection portion (20) and the Z detection portion (30) are arranged in one chip.