Development of Three-Dimensional Microstages Using Inclined Deep-Reactive Ion Etching

Three-dimensional (3-D) microstages driven by electrostatic comb actuators that provide continuous motion along three axes (x,y , and z ) were designed and fabricated. Each 3-D microstage consisted of sets of traveling tables, suspension systems, and comb actuators. To convert lateral displacement of the comb actuators to vertical motion, one suspension system incorporated leaf springs inclined to a substrate. To efficiently construct the inclined leaf springs, we devised a fabrication technique that uses deep reactive ion etching. Three-dimensional microstages were then fabricated in a 20-mum-thick device layer on a silicon-on-insulator wafer. The maximum vertical (z) displacement of this 3-D microstage was 2.6 mum, and the maximum lateral displacement (x and y) was more than 6 mum in each direction, achieved by using support suspensions to suppress the interference between the comb actuators. A 3-D microstage was then installed in a commercial atomic force microscope, and a 3-D image of a grating was successfully measured without hysteresis using this 3-D microstage as the scanning device.