Fusion of micro-metrology techniques for the flexible inspection of MEMS/MOEMS assembly R. Schmitt*, A. Pavim† Laboratory for Machine Tools and Production Engineering WZL of the RWTH Aachen University, Steinbachstrasse 19, 52074 Aachen, Germany ABSTRACT Micro-technology plays an important role in everyday life, without being much perceived. Cell phones, for instance, are daily equipped with small electronic components, which must have their quality level assured. New micro-metrology techniques were developed in the last years for such purposes. They are usually only suited for measuring specific and individual object properties (e.g. geometry, roughness, contours). A multi-sensorial approach is needed to improve the inspection range and flexibility of a micro-production cell, so that the distinct features of different industrial parts may be inspected intelligently and independently of their surface properties. This work provides a basic review on some of the most important “non-contact” micro-metrology techniques (optical and non-optical), performing a comparison of these methods among their distinct capabilities and possible industrial applications/integration scenarios. Based on the already existent sensor fusion principles, the MEOND concept will be introduced to build up flexible inspection systems for small series production by combining sensors and data, focusing possible application scenarios of the micro-world. The fusion of micro-metrology techniques has not yet been far explored and is extremely important to assure flexibility, autonomy, accuracy and robustness for the assembly of MEMS/MOEMS systems. Keywords: Micro-metrology, optical metrology, non-destructive testing, sensor fusion, MEOND, MEMS/MOEMS

1. INTRODUCTION Micro-technology is considered a key technology in many industrial sectors, with a continuously growing market. It has evolved a lot in the recent years in different application fields and plays an important role in everyday life, without being much perceived. Computers, cell phones and automobiles are daily equipped with small electronic, mechanic and optical components, which must have their quality level assured. There is a strong global trend for the miniaturisation of production, due to the benefits coming from the micro-factory concept, such as [1]: economy of space and energy, reduction of investments and fabrication costs, smaller production cycles, utilisation of smaller, light and flexible manufacturing and montage. Novel monitoring solutions are essential to provide robustness and autonomy to such micro-factories. New micro-metrology techniques were developed in the last years for such purposes. Although they present good measurement results, it is usually not possible to attend all the inspection needs of the micro-technology industry with only a single inspection technique [1][2]. Distinct measurement principles or configurations need to be used for the inspection of objects with different shapes and/or materials. This means that the measurement system is somewhat dependent on the object features. This dependence is undesirable for monitoring flexible production lines, as small series production of printed circuit boards (PCB) or micro-lasers, for example. A multi-sensorial approach is needed to improve the inspection range and flexibility of a micro-production cell, so that the distinct features of different industrial parts may be inspected intelligently and independently of their surface properties. This work starts providing a basic review of some of the most important “non-contact” micro-metrology techniques (optical and non-optical), performing a comparison of these methods among their distinct capabilities and possible industrial applications/integration scenarios. In the sequence, based on the already existent sensor fusion principles, the Measurement on Demand (MEOND) concept will be presented as a possible solution to build up flexible inspection systems for small series production. Possible application scenarios for this concept will be discussed among the flexible inspection of micro-electrical circuits’ assembly and the self-optimised assembly of a micro-laser. *

Prof. Dr.-Ing. Robert Schmitt; [email protected]; Tel. +49 241 80-20283, Fax: +49 241 80-22193

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Scholarship holder of the Brazilian CNPq