Sensor-based on-the-fly laser processing

Solar cell production is entering the terawatt range. With laser- processing being an important part of silicon solar cell manufacturing, a laser tool is required to reach a throughput of over 10,000 wafers per hour (wph) with accuracies of 10-100 µm and small structure sizes (<30µm) over the full solar cell area. To meet these demanding requirements, we have developed a new laser machine concept relying on on-the-fly processing and integrated tracking. Velocity fluctuations on high-throughput conveyor belts are measured using custom optical tracking hardware, enabling real-time active oscillation compensation through synchronization with the laser scanner. With this approach the pattern oscillations through transport imperfections could be reduced from 82.2µm to 13.2µm (1σ). To meet the necessary beam velocity of 1km/s and numerical aperture, polygon scanners are demonstrated to be well suited in combination with this on-the-fly processing approach, reaching a processing time of just 200ms for a full wafer.