Evaluation of residual stress in MEMS structures by Digital Holography

Year: 2003

Authors: Coppola G., De Nicola S., Ferraro P., Finizio A., Grilli S., Iodice M., Magro C., Pierattini G.

Autors Affiliation: Istituto per la Microelettronica e i Microsistemi – CNR, Sez. di Napoli, Via P. Castellino 111, 80131 Napoli, Italy;
Istituto di Cibernetica – CNR “E. Caianiello”, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy;
Istituto Nazionale di Ottica Applicata, Sez. di Napoli, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy;
Si-based optoelectronics, Bio-& Nano-systems group, STMicroelectronics srl, Stradale Primosole 50, 95121 Catania, Italy

Abstract: We investigate digital holography method as metrological tool for inspection and characterization of MEMS structures. The efficiency of the digital holography is demonstrated measuring out of plane deformations due to the intrinsic residual stress. Microstructures under investigation are of two different types: the first are made of a single polysilicon layer, whereas the second are bimorph structures with a thin silicon nitride layer over the polysilicon one. These structures exhibit an out-of-plane deformation owing to residual stresses between the different layers. The characterization of these deformations is instrumental to study and understand the effect of residual stress on the deformation of the single micro structures. To this aim digital holography has been applied as metrological tool in order to obtain the profile of the microstructures. These data are employed in analytical and numerical model to evaluate residual stress inside the investigated structures. Moreover, digital holography has been employed to evaluate MEMS behaviour when subjected to thermal load. Profile of cantilevers, with dimensions from 1 to 50mum, has been measured.

Journal/Review: PROCEEDINGS OF SPIE

Volume: 4933      Pages from: 226  to: 231

KeyWords: digital holography; MEMS;
DOI: 10.1117/12.516637

Citations: 5
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