VINSPEC SP – Inline process control for thickness of the antireflection coating at PV-wafers
Winner of the CELL AWARD 2009 in the category: Best technology for silicon feedstock and wafer processes
VINSPEC SP is a joint development between tec5 in Oberursel/Germany, specialists for industrial spectroscopic measuring systems and VITRONIC in Wiesbaden/Germany, the machine vision specialists whose camera based inline quality inspection systems are already integrated into several hundred automated PV cell and module production lines.
Innovative Aspects
In contrast to traditionally used imaging systems VINSPEC SP employs a high end diode array spectrometer, which offers a direct method to measure physical properties of one or more coating layers, instead of indirect calculations from colour values. From this data the layer thickness is determined with an accuracy of better 1 nm. The data from the 9 observed spots allows effective screening of the overall properties of the wafer. Owing to high speed spectroscopic technology, this data is collected on-the-fly (~250 ms, depending on belt speed), without interruption of the feeding process. The probe is connected to the instrument via optical fibers, allowing for small and robust probes. In addition the concept of remote probes allows for easy maintenance since measurement electronics including the light source can be accessed without interfering with the running production line.
Benefits
High speed spectroscopic technology allows for short sampling intervals and therefore the possibility of inline process analysis of photovoltaic wafers. Statistics over the 9 measured spots
give precise information about layer thickness, uniformity, major defect areas and overall quality of the coatings on the wafer. Resultant shorter cycle times, a more detailed layer characterization and more information to react to changes in product quality. The possibility to obtain full spectroscopic data in the UV/VIS/NIR-range allows for characterization of multiple layers, making this method ideal for immediate process feedback control.
Together with the benefits of an easy and intuitive graphical user interface which is well known and proven with VINSPEC systems, an industrial spectrometer unit, as well as state of the art communications to line PLCs and MES is a new highly efficient process optimization tool that pays off in a very short time. All measurement results are stored and can be accessed for statistical analysis.
The same spectrometer system is also available without inline add-ons for use as measurement tool in labs.