A SIMPLE COPPER BASED PLATING PROCESS RESULTING IN EFFICIENCIES ABOVE 20.5 USING PILOT PROCESSING EQUIPMENT

摘要

Despite cost and technological advantages, the commercialization of nickel/copper (Ni/Cu) platedcontacts has so far been limited. Reasons for this include increased process complexity, availability of suitable lowcostproduction tools, and doubts over long-term reliability. We previously reported on a simple Cu basedmetallization sequence consisting of i) defining the front contact pattern by ps-UV laser ablation ii) self-alignedplating of the contacts using Ni/Cu/Ag and finally iii) sintering in N2 for nickel silicidation. We also reported that 10cells strings modules featuring these Ni/Cu/Ag contacts met extended (1.5x) IEC61215 criteria for thermal cyclingand damp heat reliability. In this work, this process sequence is transferred to 156×156 mmm~2 substrates using pilotlineprocessing equipment available at imec that include inline plating and sintering tools. The process sequence isfurther simplified to yield an industrial 0.5μm deep emitter without compromising efficiency results nor ribbon pullforce values (average >3N/mm). This 0.5μm emitter also proves to be more robust to changes in sheet resistanceinduced during processing than the previously used high-efficiency 1μm deep homogeneous emitter. Applying the0.5μm deep emitter and optimizing both front grid design and plating thickness we demonstrate efficiencies above20% on 109 cells (average of 20.5%), with the best cell achieving 20.7% (externally confirmed by FhG-ISE CalLab).