Product Code: ICA10_M1102

Process Optimization for Improving Drilling Efficiency in EWT Solar Cell Manufacturing
Authors:
Henrikki Pantsar, Fraunhofer USA, Inc., Center for Laser Technology; Plymouth MI USA
Mathew Rekow, Pyrophotonics Lasers, Inc.; Dollard-Des-Ormeaux QC Canada
Richard Murison, Pyrophotonics Lasers, Inc.; Dollard-Des-Ormeaux QC Canada
Hans Herfurth, Fraunhofer USA, Inc., Center for Laser Technology; Plymouth MI USA
Stefan Heinemann, Fraunhofer USA, Inc., Center for Laser Technology; Plymouth MI USA
Thomas Eisenbeis, Fraunhofer USA, Inc., Center for Laser Technology; Plymoth MI USA
Presented at ICALEO 2010

Pulse parameter optimization is a key element in reaching higher drilling rates in the production of Emitter Wrap Through (EWT) solar cells. Manufacturing of these cells relies on fast laser drilling of silicon wafers. In order to create a cost case for EWT manufacturing, not only the drilling rate, but also the investment costs and cost of ownership have to be taken into account. In this aspect using fewer lower power lasers with a capability to maximize energy efficiency in drilling is an important factor.

Master Oscillator Power Amplifier fiber laser concept allows for independent adjustment of pulse width, energy and temporal shape. This capability can be exploited for improving the drilling process efficiency. Combined with a FPGA controller, one can drill holes at unprecedented speeds. It was shown that a single hole can be drilled through a 210 µm silicon wafer using less than 3 mJ of energy; consequently 6,250 holes per second could be drilled using 18.2 W laser power. The results were compared to q-switched lasers by mimicking the shape of a high peak power q-switched pulse.