Multilayer coating method for x-ray reflectivity enhancement of polysilicon micro-mirrors at 1.54-Å wavelength

A poly-silicon piston micro-mirror array, which has been enhanced with a multilayer coating to exhibit special reflective properties at Cu K α emission line of 1.54 A is presented. The micro-mirror array is fabricated using the MEMSCAP PolyMUMPs process and packaged in a ceramic package. The packaged array is coated using atomic layer deposition with an Al 2 O 3 /W multilayer. The first Al 2 O 3 layer is thicker than for a normal bilayer pair and prevents the mirror coating from creating an electrical short. This device was tested before and after coating. The snap-down voltage was reduced by half, but qualitatively the mechanical motion remained similar. The fabrication process presented for the Cu K α wavelength at 1.54 A can be easily adapted to other optical MEMS and for other wavelengths.