PES is proud to welcome Carl Zeiss MicroImaging GmbH back to its pages. We catch up with Product Manager Chris Hellwig who discusses how the company are supporting high quality in manufacturing – from the lab to the production line.
When measuring surface properties like spectral reflectance and transmission at fast moving and dynamic mass production lines, the requirements concerning the optical heads differ dramatically from lab-scale or pilot production lines.
While the Optical Sensor Systems department of Carl Zeiss MicroImaging (OSS) has been developing and improving applications for its fab proven inline metrology systems, optical measuring heads have increasingly become the focus of attention during the last couple of years.
Knowledge of the spectral reflectance and transmittance as well as derived results like colour metrics or layer thickness is a vital requirement to stabilise production quality, cost and output. Evaluating a sample in an at-line quality lab requires fundamental knowledge of the measuring instrument and the processes used to produce the sample. In in-line metrology additional challenges have to be addressed. The process integration including the PLC, MES and database connections has to be done. Most thin film PV fabs produce their products in continuous flow. Thus the sample not only moves in the conveyor transport direction. Due to the characteristics of existing conveyor systems the sample vibrates, resulting in distance variations between the substrate surface and the optical measuring head. Traditional measuring geometries are sensitive to these distance variations, resulting in some uncertainties.
Additionally there is a strong need in the market to measure haze. The haze reflection is needed as a direct functional measured value representing the roughness or surface texture of the sample. Haze is needed to calculate the layer thickness in multilayer systems too.
