Electromagnetically actuated surface micromachined free standing torsion beam micromirror made by electroplated nickel

In this paper we report extremely simple 2-mask exposure fabrication process using photoresist as sacrificial layer to fabricate electromagnetically actuated torsion beam micromirror. The important feature of this reported include that the torsion beam and micromirror body are made of low stress electroplated nickel, and the torsion beam micromirror is testing on a free standing structural frame also made of electroplated copper. This device structure has resulted in a simplified fabrication process. The electroplated, low stress nickel piece having a dimension 1200 x 1400 x 4 mum(3) constitutes the mirror body and is used as reflective surface as well for magnetic interaction with magnetic field. Electromagnetic actuation in mirror is realized by control of current through a set of 500 turns copper coils on 7 cm long iron pole to which free standing mirror fixture was integrated. This structure is capable to have bi-directional actuation and a maximum deflection >24degrees has been obtained in static mode for the investigated electromagnet's coil current. The electromagnetically induced deflection of our torsion mirror were modeled and shown to agree with experimental measurements.