Application of CMOS Metal Barriers to Copper Plated Silicon Solar Cells

In this paper, alternative front-side metallization schemes for c-Si solar cells are investigated. These are based on the sputtering of different metal barriers followed by copper electroplating. Different emitters have been evaluated. The influence of the plating process and the impact of different barrier materials on contact resistance, plating properties and device reliability are also investigated. Using this approach, large area silicon solar cells with conversion efficiencies up to 19.4% are obtained on Cz material. First results on the application of these deposition techniques in a low-cost industrial compatible process flow show a conversion efficiency of 18.5%. The influence of the plating process and the impact of different barrier materials (Ti, Ti/TiN, Ta and TaN) on the device reliability are studied. The effectiveness of the silicon nitride antireflecting layer and the metal barrier layer to the diffusion of copper is looked upon and the impact on solar cell performance of different aging processes is assessed.