Multiple aspect-ratio structural integration in single crystal silicon (MASIS) for fabrication of transmissive MOEMS modulators

A novel fabrication process, named MASIS (multiple aspect ratio structural integration in single-crystal-silicon), is introduced for the implementation of single-crystal-silicon microstructures characterized by distinct aspect ratios to be fabricated in the same device layer. The MASIS process was especially designed for fabrication of transmissive MOEMS (Micro-Opto-Electro-Mechanical-Systems) modulators incorporating large field areas, and driven by long-stroke comb-drive actuators combined with folded suspensions. The comb-drive actuators were designed to achieve large amplitude of vibration and high natural frequencies, which allow large aperture areas at high operational frequency. The MASIS process consists of selective thinning of the device thickness in the shutter area, reducing payload mass, while preserving higher thickness of the suspension springs and comb-drive transducer fingers, thereby increasing the natural frequency of the device and reducing actuation voltages. A modulator was successfully fabricated, demonstrating maximum displacement of 50 μm at 1 kHz in resonance using an actuation voltage of 15 Vpp in air. The MOEMS modulator was adapted as integral part of a solid-state photodetection system to overcome the low-frequency noise.