Novel electrostatic MOEMS phase shifter array using CMOS-MEMS process

We present a 3 x 3 micro-optoelectromechanical systems (MOEMS) phase shifter array that achieves a lambda/4 vertical displacement with peak-to-valley deformation within lambda/10 (514-nm light source). The mirror reflective surface is made of an aluminum layer with a high optical reflectivity exceeding 90%. Each individual micromirror pixel is controlled and driven by comb drive actuators. The phase shifter array is fabricated using the Taiwan Semiconductor Manufacturing Company 0.35-mu m 2P4M complementary metal-oxide semiconductor process. In-house post-processing is utilized to reserve a 40-mu m-thick bulk-silicon under the 200 mu m x 200 mu m mirror. This eliminates mirror deformation from residual stress after the device is released. The micromirror demonstrates a vertical displacement of lambda/4 at 38 V. The device resonant frequency is 3.71 kHz, and the fill factor is 0.65. This MOEMS phase shifter array can be used as a spatial light modulator in holographic data storage systems. (C) 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3280264]