Modeling, design, fabrication and measurement of a single layer polysilicon micromirror with initial curvature compensation

A micromirror array for optical phase modulation is designed, fabricated and tested in this paper. It consists of 5 x 5 single layer polysilicon-based, electrostatically driven actuators. The micromirror array is made by using only two masks and can be driven independently by 25 channel circuits. About 6 pi phase modulation can be obtained in He-Ne laser (lambda similar or equal to 633 Mi) with 67% fill-factor. The deflection characteristics of the actuators with residual stresses and initial curvature are modeled and confirmed by experiments. The initial curvatures of mirror and spring element are also predicted by an appropriate modeling and compensated by using the gold metallization. The modeling results agree well with the experimental results. The detailed modeling of the deflection characteristics and pull-in behavior and the compensation method of obtaining a flat surface give us more exact prediction and better performance of the optical micromirror. (C) 1999 Elsevier Science S.A. All rights reserved.