Modern optical measurement station for micro-materials and micro-elements studies M. Kujawin ´ska * Institute of Micromechanics and Photonics, Warsaw University of Technology, 8 Chodkiewicza Street, 02-525 Warsaw, Poland Abstract The paper gives the overview of various (point and full-field) concepts of optical measurements of micro-elements including micro- electromechanical system (MEMS), micro-optical-electromechanical system (MOEMS) and electronic packages. In particular, it describes waveguide micro-interferometer which enables an alternative usage of conventional interferometry (CI) and grating interferometry (GI) (reflective surfaces), ESPI (scattering surfaces) and digital holographic interferometry (DHI) (mixed surfaces) for shape, in-plane and out-of- plane displacement measurements. To prove the applicability of this micro-interferometer, the wide selection of measurement examples is given. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Optical full-field methods; Micro-interferometry; Waveguide interferometer; Micro-materials; Micro-elements; Optical testing 1. Introduction Competitive trends to miniaturize micro-electromechani- cal system (MEMS) and micro-optical-electromechanical system (MOEMS) and electronic components and packages introduce unprecedented requirements concerning their designs. To satisfy these challenges, new materials and technologies are being employed. Complex structures of modern micro-mechanical assemblies and electronic packages must withstand wide range of applied or generated mechanical, thermal and electrical loads. To ensure their optimum design, functionality and reliability hybrid experi- mental/numerical methods of analysis are being implemen- ted [1,2]. These include:  forming theoretical models of structure behavior and implementing them into finite element method (FEM) and computer aided design (CAD) analysis,  incorporating the experimental displacement/strain per- formance of elements with knowledge about accurate geometry of the object being modeled, including local, small scale irregularities,  taking into consideration the experimentally determined material constants in micro-scale, which due to unique processing procedures high stress levels and small fea- ture sizes may differ from the bulk material properties, performing long-term monitoring and quality control of ready-to-use devices. Considering experimental methodologies for micro-scale component analysis, it can be easily recognized that the conventional procedures involving strain gauges, photo elas- ticity, mechanical probing, etc. are generally not applicable to these measurement. An alternative to the conventional methods is provided by full-field optical methods including the most popular: conventional interferometry (CI), electro- nic speckle pattern interferometry (ESPI) and shearography, grating (moire ´) interferometry and recently proposed digital holography supported by thermovision and optical, confo- cal, scanning electron microscopy (SEM) or atomic force microscopy (AFM). Recent advances in semiconductor coherent light sources, CCD detectors, waveguide and fiber optics technology enable to realize compact, remote control, automatic measuring systems which provide data about static or dynamic behavior of micro-elements with nan- ometer sensitivity and micro-meter spatial resolution. Below the review of different measurement concepts based on point-wise and full-field optical methods is pre- sented. In order to fulfil most of the requirements connected with advanced micro-element and micro-material testing, the general concept of the optical measurement station based on a waveguide micro-interferometer is proposed and described in details. The applicability of the system with configurations adopted for various full-field optical methods is shown at the examples representing great variety of micro- elements and electronic components. Sensors and Actuators A 99 (2002) 144–153 * Tel.: þ48-22-660-8489; fax: þ48-22-660-8601. E-mail address: m.Kujawinska@mchtr.pw.edu.pl (M. Kujawin ´ska). 0924-4247/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0924-4247(01)00911-6