NOVELTY - Forming back contact solar cell involves depositing first metal layer of electrically conductive metal on backside surface of a semiconductor solar cell substrate; attaching an electrically insulating backplane layer on the semiconductor solar cell substrate comprising first metal layer, drilling via holes in backplane layer to first metal layer; and detecting the via hole endpoint during the laser via drilling process to extend the via hole through the electrically insulating backplane layer to the first metal layer and prevent breaching or punching through the first level metal.    USE - For forming a back contact solar cell (claimed).    ADVANTAGE - The method provides low cost metallization option for high efficiency solar cells including high-efficiency back-junction, back-contact crystalline silicon solar cells.    DETAILED DESCRIPTION - Forming a back contact solar cell involves depositing a first metal layer of electrically conductive metal on a backside surface of a semiconductor solar cell substrate, where the first metal layer comprising base electrodes and emitter electrodes connected to base regions and emitter regions on the semiconductor solar cell substrate; attaching an electrically insulating backplane layer on the semiconductor solar cell substrate comprising the first metal layer, drilling via holes in the backplane layer to the first metal layer, the via holes laser drilled through the backplane layer and the first metal layer at specified positions to expose conductive metal on the first metal layer to form base contacts and emitter contacts to the first metal layer; detecting the via hole endpoint during the laser via drilling process to extend the via hole through the electrically insulating backplane layer to the first metal layer and prevent breaching or punching through the first level metal; and forming a second metal layer of electrically conductive metal on the backplane layer, the second metal layer contacted to the first metal layer through the via holes and providing conductive leads for electrical connections to the back-contact solar cell.