Laser-fired contacts - transfer of a simple high efficiency process scheme to industrial production

Abstract

Laser-fired Contacts (LFC) have just recently been proposed as a simple way to realize local contacting for a passivated rear surface. Efficiencies above 20% have been reported for this technology. This work aims to assess the current status of the transfer of this process scheme to industrial production. The application of laser-fired contacts to 2 /spl Omega//spl euro/cm silicon wafers yielding an open circuit voltage of more than 660 mV clearly indicates the formation of a local aluminum back surface field. A newly developed pilot type laser system with automated wafer handling is presented. Due to the use of scanning mirrors for the movement of the laser beam the LFC process time is reduced to just a few seconds per wafer. Finally the most important criteria for an industrial transfer are discussed in comparison to the standard Aluminum back surface field (Al-BSF), being the benchmark for any other rear surface passivation scheme up to now.