Ring Vibrator Angular Velocity Sensor Electrode Placement
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Solution Overview
Problem
Existing angular velocity sensors face challenges in sealing reliability and mass production of uniform products due to complex circuit configurations and difficulties in controlling etching depth, leading to reduced detection accuracy and limited electrode usage for frequency adjustment.
Innovation Solution
The angular velocity sensor features a semiconductor substrate with electrodes for electrostatic actuation, capacitance detection, and vibrational frequency adjustment formed within the same plane, allowing for improved sealing and precise frequency matching without complicating the circuit, using a ring-shaped vibrator with strategically placed electrodes and amplifier circuits on the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrodes are provided on the glass substrate with wire bonding through contact holes, then electrical connections are established, but the sealing property of the vibrator deteriorates due to metal wirings passing through the sealed portion
Solution Approach 1:
The patent extracts the electrode formation from the glass substrate and relocates it to the semiconductor substrate. By forming electrodes directly on the semiconductor substrate using MEMS techniques, the need for wire bonding through contact holes in glass substrates is eliminated, thereby improving sealing property while maintaining electrical connections.
Solution Approach 2:
The patent replaces the mechanical wire bonding system with a direct electrical connection system. Instead of using metal wirings that physically pass through sealed portions, the invention uses electrodes formed directly on the semiconductor substrate, substituting the mechanical connection method with a more integrated approach that preserves sealing integrity.
2Manufacturing precision
If etching depth is controlled by changing etching time, then capacitance gap can be adjusted, but mass production of uniform products becomes difficult due to considerable effect of etching conditions on etching time
Solution Approach 1:
The patent changes the control parameter from etching time to etching width. By using a mask pattern to control etching width, the capacitance gap can be precisely controlled and made uniform across mass-produced products. This parameter change from time-based to width-based control eliminates the variability introduced by etching condition fluctuations.
3Measurement precision
If electrodes for vibrational frequency adjustment are formed outside the ring portion, then circuit configuration becomes simpler, but frequency adjustment precision is reduced due to limited electrode positioning flexibility
Solution Approach 1:
The patent utilizes the internal space inside the ring portion as an additional dimension for electrode placement. By forming electrodes both inside and outside the ring portion, the invention gains extra positioning flexibility and freedom in arranging frequency adjustment electrodes, thereby improving frequency adjustment precision without significantly increasing circuit 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 enhances sealing reliability, simplifies the circuit, and enables high-precision frequency adjustment, facilitating the mass production of sensors with uniform characteristics and improved temperature stability.
Implementation Method 1
electrodes for electrostatic actuation for the vibrator... When driving voltage has been applied between the electrodes of the weight 71 of the vibrator 74 and the electrodes 61a and 62a for electrostatic actuation, electrostatic forces act on the electrodes 61a and 62a for electrostatic actuation in the direction of a spacing between both electrodes, thereby the vibrator 74 vibrates
Implementation Method 2
a pair of electrodes 61b for capacitance detection... These vibrations vary the distances between the surface of the weight 71 of the vibrator 74 and the electrodes 61b and 62b for capacitance detection, and hence capacitances between them vary. Therefore, by detecting such variations in the capacitances, the applied angular velocity can be detected.
Implementation Method 3
electrodes for vibrational frequency adjustment of the vibrator are formed at the outside or inside of the ring portion which is opposite the side of the electrodes for electrostatic actuation and the electrodes for capacitance detection
Implementation Method 4
When an angular velocity has been applied about the x axis at that time, the vibrator 74 vibrates while rotating about the y axis by the action of a Coriolis force
Data Source
AI summary
A vibrator 10, which is formed in a silicon wafer 1 by means of MEMS technique, has eight beam portions (beams) 12 supported at a central portion 11 and extending in the radial direction while mutually keeping the same angle and has a ring portion 13 connected to the eight beam portions 12. Outside the ring portion 13, eight electrodes 21a to 21h for electrostatic actuation, capacitance detection, or the like are spaced uniformly with a gap 22 created between the ring portion 13 and the electrodes 21a to 21h. Inside the ring portion 13, sixteen electrodes 23 for frequency adjustment are spaced uniformly with a gap 24 created between the ring portion 13 and the electrodes 23.