Polytec: White-light interferometer inspects finest structures


Advances in microsystems technology and microelectronics are increasing the demand for measurements of structural details, for example to characterise channel depths and edge profiles on a lab-on-a-chip, to determine step heights, co-planarity and other packaging parameters, or to characterise MEMS based on their 3D structural profiles and derived surface parameters, such as roughness, flatness and deformation. With the TopMap Micro.View+, Polytec (Waldbronn, Germany) has a high-resolution microscope-based white-light interferometer in its range for such applications.

The colour information (RGB) of the measured object, which is provided in addition to the height measurement, simplifies defect assignment. Equipped with motorised x, y and z axes, a travel range of 200 x 200 x 100 mm³ and a likewise motorised objective turret, test sequences can be carried out automatically according to specific "recipes", the sample height can be measured up to 370 mm and the measuring head can also be integrated separately directly in the production line.

At the Institute for Microelectronics Stuttgart (IMS CHIPS), the high-resolution inspection system has meanwhile proven itself in practical use for inspecting the surface of flexible hybrid electronics. In the wafer-based production process, chips are embedded on a polyimide film, overlaid and wired with lithographic structuring. For quality control, the fine structures of the four-layer structure have to be checked. At the same time, the results help to evaluate and optimise the manufacturing process. The 3D measurement data from the white-light interferometers can be processed with any suitable evaluation software. This is particularly easy with the TMS software specially developed for these topography measuring systems, which offers numerous options for evaluating the measurement results quickly and in compliance with ISO. In addition, the software can be individually modified thanks to good documentation, open structure and modular design. This means that internal knowledge remains within the company and it is possible to react flexibly to changing requirements.

Caption: The microscope-based white-light interferometer detects the finest structural details over the entire measuring range. (image source: Polytec/ IMS CHIPS)

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