Covalently formation of insulation and barrier layers in high aspect ratio TSVs

Polymers have been widely explored as the alternative material for silicon oxide in through-silicon vias (TSVs). However, an acceptable adhesion between polymers and metallic diffusion barriers is often challenging, espe-cially when it comes to ultrathin films with extremely low roughness. This paper proposes a cost-effective and highly reliable wet deposition path to successively fabricate polyacrylic acid (PAA) insulation films and nickel diffusion barriers on the silicon substrate. PAA films were firstly pretreated to form diazo functional groups through aryldiazonium chemistry. With an electrochemical reduction, catalytic palladiu m nanoparticles and palladium chelates were introduced to the pretreated substrate by robust Pd-C covalent bonds and electrostatic interaction, respectively. After being immersed into the plating solution, a continuous and uniform nickel layer on the PAA substrate with high adhesion strength can be obtained . Therefore, a stable interface between polymer insulation layers and nickel diffusion barrier can be provided by the proposed covalent fabrication approach. This wet polymer metallization approach on the flat silicon substrate was further extended in TSVs (3 mu m x 30 mu m) for practical deployment.

Automated summary

The study introduces a cost-effective wet deposition path for fabricating PAA insulation films and nickel diffusion barriers on silicon substrate, providing a stable interface between polymer insulation layers and nickel diffusion barrier.