Direct Electroplating on Indium-Tin-Oxide-Coated Textured and Polished Silicon Substrates via Transition Metal Alloyed Interlayers

Abstract

Fe electroplating was used on polished or pyramidally textured indium-tin-oxide (ITO)-coated silicon substrates as an initial layer for subsequent Ni and Cu plating. Up to 15 μm thick Cu layers were deposited on the Ni/Fe intermediate layer. The adhesion strength of this metal layer stack was qualitatively shown using the scotch tape method and quantified by measuring the pull-off stress of the metal stack on ITO. 1.44 and 1.28 MPa was applied to pull off the metal stack from polished and pyramidally textured substrates, respectively. Electrical contact properties were measured by circular transmission line model structures. Very low contact resistivity for electroplated metal on ITO of 6.5E−7 and 9.0E−7 Ωcm2 with transfer lengths of 487 and 720nm are determined for polished and pyramidally textured substrates, respectively.

Study of Microstructure and Mechanical Properties of Electrodeposited Cu on Silicon Heterojunction Solar Cells

“…The combined effect of the reduction in grain boundary energy and the elastic energy of dislocations could have led to the observed self-annealing in the investigated Cu film. The average grain size was about 900 nm for the electroplated Cu films 672 h after deposition [20].…”

“…In recent research conducted by Politze et al, the authors investigated using Fe electroplating as an initial layer for subsequent Ni and Cu plating on polished or pyramidally textured indium-tin-oxide-coated silicon substrates [20]. The Fe layer acted as an intermediate between the ITO-coated substrate and the Cu layer.…”

“…Cu layers of up to 15 µm were deposited on the Ni/Fe intermediate layer. The pull-off stresses, which indicate adhesion strength, of the Cu/Ni/Fe/ITO/Si stack were measured to be 1.44 MPa for the polished substrates and 1.28 MPa for the pyramidally textured substrates [20]. Interestingly, Politze et al also examined the direct electroplating of Cu onto the Fe layer without the Ni layer.…”

“…In this case, the metal stack (Cu/Fe/ITO/Si) exhibited poor adhesion and lifted from the substrate. However, when a thin, conformal Ni layer was deposited between the Fe and Cu layers, the Fe/Ni/Cu layer stack maintained good adhesion, even with a Cu layer thickness of 15 µm [20]. This suggests that the Ni layer promotes adhesion between the Cu and Fe layers.…”