Microstructure analysis of the interface situation and adhesion of thermally formed nickel silicide for plated nickel-copper contacts on silicon solar cells

The point of failure upon performing solder and peel testing on sintered contacts has been identified to be at the silicide-nickel interface. Microstructural analysis shows that void formation can be observed at this interface. The mechanisms of silicide and void formation from plated layers on solar cells are studied taking into account different electrolytes and pretreatments. The cavities can be removed by selective nickel etching and replating nickel onto the formed silicide after silicide pretreatment. Excellent adhesion of up to 2.5 N/mm has been measured, which represents the force of silicon wafer breakage rather than true metal adhesive force.