VINSPEC SP - Inline process control for thickness of the antireflection coating at PV-wafers

Description

It utilizes 3 optical probes, which are positioned above the conveyor belt in the production line and sample the reflected light at different positions on the wafer passing by. The probes are connected to a fast digital spectrometer system via fiber-optical cables. The spectrometer records 3 spectra per wafer and probe, resulting in 9 inspection areas distributed across the wafer surface. The areas are 3 mm wide and 12 mm long at a belt speed of 600 mm/s. The operating software offers automatic logging of all values into an SQL-database, allowing easy access for later data analysis. Reference measurements and calibration are performed automatically. VINSPEC SP offers MES logging of all process and measurement data in conformity to SECS/GEM standards and thus smoothly integrates into the manufacturing environment. VINSPEC SP is a joint development of tec5 from Oberursel/Germany, the specialist for industrial spectroscopic measuring systems and VITRONIC from Wiesbaden/Germany, the machine vision specialist whose camera based inline quality inspection systems are already integrated several hundred times into automated PV cell and module production lines.

Innovative Aspect

The fast spectroscopic technology allows for short sampling intervals and thus 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 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 of obtaining the 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 easy and intuitive grap

hical user interface, well known and proven with VINSPEC systems, an industrial Spectrometer unit, as well as state of the art communication to the line PLCs and MES, the new system is a highly efficient process optimization tool that pays off in very short time. All measurement results are stored and can be used for statistical analysis. The same Spectrometer system is also available without Inline Add-ons for use as measurement tool in labs.

Benefits

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 color values. From this data the layer thickness is determined with an accuracy of better 1 nm. The data from the 9 observed spots allow a good screening of the overall properties of the wafer. Owing to the fast 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 light source can be accessed without interfering with the running production line.