Laser System Development Division Photovoltaics Fraunhofer Institute for Solar Energy Systems
Tuesday, February 16, 2021, 11:00
As a production technology with very low running cost, laser processing has continuously gained importance for the manufacturing of silicon solar cells. Improvements of new cell concepts using laser material processing have already been demonstrated in the laboratory. To make advances from the lab accessible to the scales of industrial manufacturing, the economic efficiency and thus the execution time of the laser processes is also a decisive factor. The aim of this work is to develop and demonstrate a new concept of a high-throughput system for inline laser material processing.
In a demonstrator setup, wafers are to be able to be processed with high precision during transport on a simple conveyor belt. The position of the wafer needs to be tracked in real time and the laser focus must be carried along with the moving wafer. The aim is to replace expensive system components such as high-precision positioning systems with electronic control technology. Regarding the rapid development of semiconductor technology in recent decades, which is also reflected in sensor technology, the development from classic mechanical engineering solutions to cheaper, faster and intelligently controlled system concepts is a promising topic.
To follow the wafer's motion a measurement device, composed of an array of optical tracking sensors, was developed. The sensor array can measure the wafer position in real time with low latency to generate a control signal for the laser scanner. In addition to the inaccurate transport, the non-planar height profile of the wafer is a significant factor influencing the positioning accuracy. The setup allows the recording of numerous parameters such as wafer trajectory, target and actual movements of the laser scanner mirrors and wafer height profile, and thus forms, together with the position data of a coordinate measuring setup the basis for modelling and offline optimization of the system towards a high positioning accuracy.