Fraunhofer ISE develops a faster laser system for wafer processing

By using a new type of laser, the processing speed of wafers can be 10 to 20 times faster than before. This is the result of a research project at the Fraunhofer Institute for Solar Systems in Germany.

Researchers have developed a prototype that can use ultraviolet waves to carve the most intricate structures on silicon wafers. The new system concept enables solar cell manufacturers to perform laser processing at the highest speed without compromising on the size of the structure or processing field.

In order to produce photovoltaic cells from wafers, wafers must be metallized. In this step, the fine channels are grooved at the top of the cell. Silver paste enters the channel and is then used as a conductor track. The speed at which the channel enters the silicon wafer is crucial for battery production to further reduce production costs.

The laser provided by Fraunhofer ISE can draw 1800 lines per second. This is 10 to 20 times faster than so-called galvanometer scanners, which are typically used for this purpose. The laser has a high repetition rate of 10 megahertz and a maximum pulse energy of 5.6 microjoules.

This laser can also process M12 format wafers with a side length of 210 millimeters. The laser engraving channel is only 15 microns wide. This is 30% finer than the currently commercially used ultraviolet laser. Compared to the very common infrared laser, the channel of the new laser is three times larger. A finer channel can reduce the use of silver paste, thereby helping to further reduce production costs.

"The unique feature of the demonstrator design is that large workpieces can be processed very quickly and the structural dimensions are small," said Jale Schneider, project manager at Fraunhofer ISE. The idea that you can only have two of these three characteristics at the same time - large image field, rapid processing, and fine structure - is deeply rooted in the laser material processing industry. With this system, we have achieved these three aspirations simultaneously.

German laser expert Edgewave GmbH has developed a prototype. Moewe Optical Solutions built a polygon scanner for this project. At Fraunhofer ISE, the team combined a polygonal scanner, laser, and axis for beam guidance into a system. The group now hopes to research new processes to increase production.

Source: Laser Net