Micromachined array-type Mirau interferometer for MEMS metrology

This work presents the micromachined array-type Mirau interferometer, designed for massively parallel (5×5 channels) inspection of wafer-scale MEMS in the regime of a low coherence interferometry. The device is composed of vertically assembled glass wafers with batch-fabricated micro-optical components, i.e. refractive lenses, diffractive elements for correction of lens aberrations, micromirrors and multilayer dielectric beam-splitter. The fabrication processes of micro-optical components are described. The resolution measurement with USAF 1951 test pattern shows the capability of interferometer to distinguish lines down to 2.4 m wide. The operation of interferometer demonstrator with the 700 × 700 m2 field of view is successfully demonstrated using commercially available MEMS IR sensor.