Hybrid laser-etching-process for wafer texturing

An approach of a texturing process combining surface modification by ultra-short pulsed laser radiation and etching techniques is developed. The hybrid process is divided into two steps: Firstly, the surface of a silicon wafer is modified by laser radiation. For this purpose, the influence of several laser parameters, e.g. wavelength, pulse duration and energy density, have been analyzed. Secondly, the surface texture is fabricated by an etching process. The modification threshold of the laser treatment is determined for different silicon materials. Different surface modifications occur for different materials after applying the laser treatment. No significant influence of the pulse duration or focus radius is found. Furthermore, the influence of laser processing and plasma etching on reflectivity spectra is compared and interactions between laser and etching parameters are investigated. The developed hybrid process results in smooth and fine surface microstructures. First results show a reduction of the reflectivity in the range of 30% compared to the reflectivity of unstructured wafers.