Thin film solar cell scribing using water jet-guided laser technology

Abstract

The water jet-guided laser technology has found a broad range of applications in the micromachining field. Its principle is to focus a laser beam into a hair-thin, low-pressure water jet, onto the sample. This hybrid system prevents heat damage to the material by cooling the cutting edges in between the laser pulses; simultaneously the water jet removes the laser generated molten material. Contamination is avoided thanks to a thin water film covering the wafer surface during the cutting process. The perfectly cylindrical water jet yields highly parallel kerf walls.In this paper experimental results from thin film solar cell grooving steps P1 and P3 are presented. P1 grooving steps on Mo and TCO yielded 40 µm wide clean cuts without burrs or cracks. Former P3 step scribing tests were performed using long-pulse lasers with pulse durations ranging from 100 ns to 1 ms. We introduce recent thin film solar cell grooving results obtained using a short pulse (10 ns) Q-switched frequency doubled laser with 15 W maximum output power. Shorter pulses allow for more precise depth control and enable successful layer removal in a single pass. The lower TCO layer remains untouched and the isolation is excellent.The water jet-guided laser technology has found a broad range of applications in the micromachining field. Its principle is to focus a laser beam into a hair-thin, low-pressure water jet, onto the sample. This hybrid system prevents heat damage to the material by cooling the cutting edges in between the laser pulses; simultaneously the water jet removes the laser generated molten material. Contamination is avoided thanks to a thin water film covering the wafer surface during the cutting process. The perfectly cylindrical water jet yields highly parallel kerf walls.In this paper experimental results from thin film solar cell grooving steps P1 and P3 are presented. P1 grooving steps on Mo and TCO yielded 40 µm wide clean cuts without burrs or cracks. Former P3 step scribing tests were performed using long-pulse lasers with pulse durations ranging from 100 ns to 1 ms. We introduce recent thin film solar cell grooving results obtained using a short pulse (10 ns) Q-switched frequency doubled laser with 15 W ma...