Kerfless Si Wafering Using Al Metal Paste, Epoxy and Ni Electroplating as Stress-Induced Layer

Abstract

Kerfless wafering is a beneficial technique that enhances the cost effectiveness of crystalline silicon (c-Si) solar cells, preventing silicon (Si) waste during diamond sawing. This study compared the advantages of three stress layers for kerfless wafering: aluminum (Al) paste, epoxy-, and electroplated nickel (Ni). These materials demonstrated the ability to exfoliate Si foil, with the electroplated Ni layer having the best result. To control crack propagation, a notch was created by laser scribing on the top and the side of the Si wafer with the Al paste and epoxy layers. The Al paste layer with silicon nitride (SiNx) exfoliated the 1 cm × 1 cm Si foil, and the epoxy layer exfoliated the 5 cm x 5 cm Si foil. However, the Si foils were fragmented after etching of the Al paste and epoxy layers. The thickness of the Si foil increased as the Al paste layer increased. The Al paste layer was etched completely but the epoxy was not removed completely. The Ni layer was electroplated on a titanium/nickel (Ti/Ni) seed layer. A 10 cm × 10 cm Si foil with a thickness of approximately 40 µm was exfoliated using an Ni electroplating method. This Si foil’s effective lifetime increased to 8.17us after Al2O3 passivation and annealing.