The laser is an extremely suitable non-contact tool for fast and automated in-line processes for example used to improve the efficiency of solar cells. With ultra-short pulsed laser radiation it is possible to decrease the reflectivity by modifying the surface topology of silicon. For the proposed modification, the optimum process window for altering the silicon surface topology on a micrometer scale is found at small laser fluencies at finite repetition rates. A promising up scaling method is process parallelization using in parallel a multiple set of interaction zones with the optimized process characteristics for single process interaction. Based on the single process, required laser process parameters and optical parameters for parallel processing are derived theoretically in order to enable a wafer processing in standard cycle times. Exemplarily 5-inch mc-silicon solar wafers are machined using a linear 7-times diffractive optical element (DOE), and in a second step solar cells are built up to determine the efficiency gain by the laser surface modification. A preliminary absolute efficiency gain of Δη > 0.2 \% is achieved.