Characterization of MEMS structures by microscopic digital holography
Anno: 2003
Autori: Coppola G., De Nicola S., Ferraro P., Finizio A., Grilli S., Iodice M., Magro C., Pierattini G.
Affiliazione autori: Istituto di Cibernetica “E. Caianiello” del CNR, Via Campi Flegrei 34, 80078 Pozzuoli (NA), Italy;
Istituto per la Microelettronica e i Microsistemi (IMM) del CNR, Sez. di Napoli, Via Diocleziano 328, 80124 Napoli, 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 propose the use of digital holography (DH) as a metrological tool for inspection and characterization of MEMS structures. We show that DH can be efficiently employed to assess the fabrication process of micro structures as well as to test their behaviour in operative conditions. DH allows reconstructing both the amplitude and phase of microscopic
objects and, compared to traditional microscopy, it provides quantitative phase determination. We demonstrate that DH allows determination of full field deformation maps that can be compared with analytical and/or numerical models of the deformed microstructure. Application of DH on structures with several different geometries and shapes, like cantilever beams, bridges and membranes is reported and result will be discussed. Dimensions of the inspected microstructures ranging from 1 to 50?m. Examples of application are presented were DH allows determination with high accuracy out of plane deformations due to the residual stress introduced by the fabrication process. An optical setup for recording digital holograms based on a Mach-Zehnder interferometer was adopted and a laser source which wavelength is ?=532nm was employed. The light reflected by the object under investigation was made to interfere with a plane wave front. Holograms were recorded by a CCD array with 1024 x 1280 square pixels with 6.7 ?m size. A mirror mounted on a piezo-actuator was inserted along the reference arm of the interferometric in order to introduce controlled phase steps and to employ phase shifting technique. This technique allows suppressing both the zeroth-order and the conjugate wave-front in the numerical holographic reconstruction process. A method for compensating numerically curvature of the wave front and introduced by the microscopic objective lens is proposed and discussed.
Giornale/Rivista: PROCEEDINGS OF SPIE
Volume: 4945 Da Pagina: 71 A: 78
Parole chiavi: MEMS; digital holography; DOI: 10.1117/12.471989Citazioni: 16dati da “WEB OF SCIENCE” (of Thomson Reuters) aggiornati al: 2024-05-12Riferimenti tratti da Isi Web of Knowledge: (solo abbonati) Link per visualizzare la scheda su IsiWeb: Clicca quiLink per visualizzare la citazioni su IsiWeb: Clicca qui