Easy plating - study on contact interface properties of parasitic plating-free Ni/Cu solar cells

The Easy Plating process sequence is an elegant way to produce Al-BSF or PERC solar cells with laser-structured Ni/Cu-plated contacts. By eliminating the HF-treatment before metal deposition one can avoid parasitic plating at defects of the anti-reflection coating by utilizing native oxide growth to passivate these defects. Recent work demonstrated a significant improvement in terms of metal recombination, optical shading and aesthetical appearance compared to the standard plating approach. However, the Easy Plating sequence is sensitive to laser-induced and native oxide formation at the Si/Ni interface in the laser defined local contact openings. This work investigates the influence of interface oxides between the Si/Ni layer and the beneficial impact of the thermal anneal for the contact resistance. Therefore, the contact resistance is studied by transmission line measurement (TLM) and SEM is applied for visualization of silicides. Our findings are important for advanced process optimization and an advanced understanding of the processes at the interface.