Automatic Pico Laser Trimming System for Silicon MEMS Resonant Devices Based on Image Recognition

This paper proposed an automatic laser trimming system for silicon MEMS devices based on picosecond laser source and image recognition technique. Through the design of laser focusing optical path and coaxial imaging optical path, the observation of laser machining process is realized. A set of picosecond laser trimming parameters are determined by experiments, which enables a 7um width trench on the silicon resonator. Compared with the femtosecond laser trimming systems, the cost of the pico-laser system is reduced by more than 60%. The shape matching algorithm based on OpenCV and the chord-to-point distance accumulation (CPDA) algorithm for MEMS resonators image measurement solve the problem that the inefficiency of manual trimming for complex resonators. The experimental results of dual-mass tuning fork resonator show that the trimming time of a single device using the automatic trimming method is reduced from more than 1 hour manual trimming to less than 1 minute and the accuracy consistency is also improved by 82.6%. Finally, the structural stiffness imbalance of tuning fork resonator caused by the manufacturing error is eliminated.