Driving Principle and Stability Analysis of Vertical Comb-Drive Actuator for Scanning Micromirrors

Area of Science:

• Microelectromechanical Systems (MEMS)
• Actuator Technology
• Nanotechnology

Background:

• Micromirrors are crucial components in various optical systems.
• Existing manufacturing processes face challenges in achieving precise control and stability.
• Vertical comb-driven actuators offer potential for improved performance.

Purpose of the Study:

• To develop a novel manufacturing process for electrostatic vertically comb-driven micromirrors.
• To analyze and model potential instability issues in micromirror operation.
• To determine the operational and failure voltage limits for enhanced device reliability.

Main Methods:

• Utilized a self-alignment process to create a height difference in comb structures.
• Developed four instability models considering quasi-static driving principles and micromirror structure.
• Fabricated a 1D micromirror (0.8 mm diameter, 30 μm thickness) with a 10 μm height difference.

Main Results:

• Achieved a static mechanical angle of 2.25° at 60 V DC.
• Observed stable operation below 60 V, aligning with theoretical predictions.
• Identified comb adhesion and lateral torsional failure at 129 V, validating failure voltage predictions.

Conclusions:

• The developed manufacturing process enables stable operation of vertical comb-driven micromirrors.
• The proposed instability models accurately predict device performance and failure points.
• This work provides a foundation for designing reliable and high-performance MEMS micromirrors.