(Invited) All-Wet TSV Fabrication Using Electroless Plated Barrier and Cu Seed Layers with Pd Nanoparticle Catalyst

Fabrication of TSV is one of key technologies for 3D-ICs. Filling of Cu electrode materials in a small dimension of TSV is essential for realizing fine-pitch TSVs, which reduce the lisk of thermal stress concentration issues. Cost reduction is also required to be feasible TSVs for a variety of devices. All-wet fabrication of TSVs using electroless plating of barrier and seed is one of solutions to fullfill these requirements. For realizing conformal thin barrier metal layers of Co-alloy or Ni-alloy electroless barriers in a high aspect TSV, Pd nanoparticles as catalyst are very effective because their adsorption is uniform throughout top to bottom of TSV. Furthermore they shows improvements of adhesion between dielectric and metal [1,2]. Adhesion issue is a serious obstacle for electroless plated films in general, however, we found displacement plating of Cu on electroless plated barrier layer has an excellent adhesion property. Finally, we succeeded in formation of a high aspect ratio TSV with superfilled Cu on electroless barrier/seed layers. Reliability aspects relating interdiffusion of Cu against the barrier layers will be discussed further. [1] F.Inoue, T.Shimizu, T. Yokoyama, H. Miyake, T.Ito, H. Seki, Y.Shinozaki, T.Yamamoto,and S.Shingubara, Electrochimica Acta, 82, 372-377 (2012). [2] F. Inoue, T. Shimizu, H. Miyake, R. Arima, T. Ito, H. Seki, Y. Shinozaki, T. Yamamoto,S.shingubara, Microelectronic Engineering, 106, 164-167 (2013).