There has been important progress at the IFSW (USTUTT) in the development of the laser ablation process of silicon (Si). This latter being one of the main application areas of the HIPERDIAS project. With the successful installation of a 500 W laser system delivering sub-300fs pulses, upscaling activities of the Si ablation process have begun. The goal being to identify processing strategies to achieve a high ablation rate (>1mm³/s) while maintaining a smooth surface (Sa<1 micron). An example of a high-quality Si ablation process is illustrated in the picture below.
One of the main challenges that the IFSW (USTUTT) has addressed within the upscaling of the Si-ablation using high-power laser was the heat accumulation effect. This leads to high surface roughness and a darkening effect on the sample. Therefore the upscaling activities have begun at the IFSW with basic investigations on the residual heat which is a key parameter regarding heat accumulation. In fact, the residual heat gives an indication of the amount of the incident pulse energy that remains inside the material as heat after the ablation process. A publication about this whole study is under preparation by HIPERDIAS partners.
On this basis, strategies to avoid a drawback of heat accumulation on the processing result have been identified and Si ablation process at high average power has been successfully implemented. Using a laser beam with 430 W of average power, Si was ablated with an ablation rate of 0.63 mm³/s. The surface quality of the produced samples was good with a roughness measured to be Sa < 2 µm A SEM image of the surface is shown below. With the planned integration of a laser system with 1 kW of average laser power by end of 2018, the HIPERDIAS partners are confident to reach the project goal of an ablation rate of >1 mm³/s.