MEMS Mirror Stabilization via Charge Removal Electrode
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Solution Overview
Problem
Electrostatically driven MEMS devices, such as micromirror devices, experience drift in mirror tilt angle due to charge accumulation in the insulating film near the fixed electrodes, leading to signal light loss and inaccurate path switching in optical switches.
Innovation Solution
Incorporating a driving stabilization electrode made of metal or semiconductor in contact with the insulating film and forming metal films on the movable member to match the driving electrodes, reducing charge accumulation and stabilizing the tilt angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating film is used near the fixed electrodes in electrostatically driven MEMS devices, then electrical insulation is provided, but charge accumulation occurs in the insulating film leading to drift in mirror tilt angle
Solution Approach 1:
A charge removal electrode is introduced as an intermediary component between the fixed electrode and the insulating film. This electrode serves as a mediator to extract accumulated charges from the insulating film, preventing charge accumulation while maintaining the electrical insulation function of the insulating film structure.
Solution Approach 2:
The electrical parameters of the insulating film interface are changed by introducing a conductive element (charge removal electrode) that modifies the charge distribution characteristics. This changes the electrical field distribution and charge accumulation behavior in the insulating film, transforming it from a charge-trapping structure to a charge-managed structure.
2Reliability
If charge accumulation occurs in the insulating film, then electrical insulation is maintained, but drift in mirror tilt angle occurs leading to signal light loss
Solution Approach 1:
The charge removal electrode acts as an intermediary that actively manages charge accumulation in the insulating film. By providing a controlled path for charge extraction, it prevents the drift in mirror tilt angle while preserving the electrical insulation function, thereby maintaining both signal transmission stability and tilt angle precision.
Solution Approach 2:
The charge removal electrode creates a feedback mechanism where accumulated charges in the insulating film are continuously monitored and removed. This feedback loop prevents charge buildup that would otherwise cause drift in mirror tilt angle, ensuring consistent optical performance and signal transmission stability.
3Reliability
If a charge removal electrode is added to the MEMS device, then charge accumulation is reduced and tilt angle stability is improved, but device complexity increases
Solution Approach 1:
The charge removal electrode is designed to perform multiple functions: it removes accumulated charges from the insulating film, maintains electrical insulation when not actively removing charges, and can potentially serve as an additional actuation electrode. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity.
Solution Approach 2:
The charge removal electrode is integrated into the existing electrode structure of the MEMS device. By merging the charge removal function with the existing electrical architecture, the patent avoids adding completely separate subsystems, thus improving tilt angle stability while minimizing the increase in overall device 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
The solution effectively suppresses drift in the mirror tilt angle, ensuring stable signal transmission and accurate path switching by reducing charge accumulation and maintaining consistent electrostatic attraction.
Implementation Method 1
a driving electrode arranged on an insulating film on a surface of the second substrate facing the first substrate so as to face the movable member across a gap and drive the movable member
Data Source
AI summary
A MEMS device includes a mirror substrate (200), an electrode substrate (301) arranged so as to face the mirror substrate (200), a mirror (230) serving as a movable member rotatably supported in an opening portion of the mirror substrate (200) via support members, a driving electrode (101) arranged on an insulating film (104) on a surface of the electrode substrate (301) facing the mirror substrate (200) so as to face the mirror (230) across a gap and drive the mirror (230), and a lower electrode (103) made of a metal or a semiconductor and formed under the insulating film (104) exposed to the gap so as to be in contact with the insulating film (104).