Nomarski imaging interferometry to measure the displacement field of MEMS

Fabien Amiot (1, 2) , Jean Paul Roger (2)

1 LMT - Laboratoire de Mécanique et Technologie
2 LSLP - Laboratoire de Spectroscopie en Lumière Polarisée

We propose to use a Nomarski imaging interferometer to measure the out-of-plane displacement field of MEMS. It is shown that the measured optical phase arises both from height and slope gradients. Using four integrating buckets a more efficient approach to unwrap the measured phase is presented, thus making the method well suited for highly curved objects. Slope and height effects are then decoupled by expanding the displacement field on a functions basis, and the inverse transformation is applied to get a displacement field from a measure of the optical phase map change with a mechanical loading. A measurement reproducibility of about 10 pm is achieved, and typical results are shown on a microcantilever under thermal actuation, thereby proving the ability of such a set-up to provide a reliable full-field kinematic measurement without surface modification.

Mots clés: Phase retrieval; Interferometry; Height measurements; Phase modulation; Interference microscopy; MEMS

Domaines: Micro et nanotechnologies/Microélectronique; Matériaux et structures en mécanique [physics.class-ph]; Matériaux et structures en mécanique [physics.class-ph]; Optique [physics.optics]; Instrumentations et Détecteurs [physics.ins-det]; Mécanique des solides [physics.class-ph]; Mécanique des solides [physics.class-ph]

Fabien Amiot, Jean Paul Roger. Nomarski imaging interferometry to measure the displacement field of MEMS. Applied optics, 2006, 45(30), pp.7800. ⟨hal-00108496⟩