Product Code: ICA11_M305

Micromachining PV Materials with Time Domain Tailored Laser Pulses
Authors:
Mathew Rekow, ESI-PyroPhotonics Laser, Inc.; Fremont CA USA
Richard Murison, ESI-PyroPhotonics Laser, Inc.; Montreal QC Canada
C Dinkel, NRC Canada, Industrial Materials Institute-CAMM; -
Tullio Panarello, ESI-PyroPhotonics Laser, Inc.; Montreal QC Canada
S Nikumb, NRC Canada, Industrial Materials Institute-CAMM; -
Walajabad Sampath, Colorado State University; Ft Collins CO USA
Presented at ICALEO 2011

For the CdTe P1 scribe, breaching of the SiO2 sodium barrier layer by the scribe laser, potentially exposes the CdTe film to Na from the soda lime glass substrate. To mitigate this problem, the industry typically applies the P1 scribe after CdTe deposition followed by a photo-resist application step to back fill the resulting groove. The photo-resist application step accounts for a large fraction of the equipment and floor space overhead in a CdTe production line. We demonstrate a novel P1 process that is enabled by carefully tailoring the temporal pulse shape, allowing selective etching in air of the SnO2:F layer with the laser, leaving the SiO2 sodium barrier layer intact. This new process enables a P1, P2, P3 scribing sequence that eliminates the photo-resist application step and allows the P1 scribe to be performed before CdTe deposition. Next, we tailor the laser temporal pulse shape for the P2 and the P3 scribing steps and compare the results to those achieved with typical Q-switched pulse shapes. The optimized shaped pulse processes are then applied in the construction of monolithically interconnected CdTe mini-modules demonstrating a new industrial scribing process sequence that markedly reduces the capital cost of a CdTe production line.