Formation of a Low Ohmic Contact Nickel Silicide Layer on Textured Silicon Wafers Using Electroless Nickel Plating

This paper presents a low cost process for fabrication of high efficiency silicon-based solar cells from front side ARC patterning through contact line metallization. This process utilizes a screen printable etch resist to define the contact pattern and a wet etching solution to remove the exposed ARC layer. The metallization stack for the contact line pattern consists of a nickel silicide ohmic contact and a nickel and copper metal stack plated using a light induced plating (LIP) process. The nickel silicide contact is formed by annealing a thin nickel seed layer that is deposited on the silicon surface using two different alternative seed layer (ASL) processes, chemically activated and light assisted electroless plating. Through optimization of the ASL processes, a thin, uniform NiSi layer is achieved that is less than 200 nm. This thin NiSi layer should be compatible with shallow emitter silicon solar cells. An LIP process for nickel and copper over the NiSi contact areas is demonstrated.