Sn/Pd Catalyzation and Electroless Cu Deposition on TaN Diffusion Barrier Layers

Abstract

The catalyzation of TaN/SiO2/SiTaN/SiO2/Si substrates was carried out by immersion in SnCl2/HClSnCl2/HCl and PdCl2/HClPdCl2/HCl solutions for electroless Cu deposition. The sizes and morphologies of the catalytic sites on the TaN layers were found to be a function of catalyzation conditions, including solution temperature, immersion time, and the surface oxides. The appropriate formula for catalyzation was obtained by considering both the quality and efficiency. The catalytic sites were composed of Sn and Pd, and the ratio of Sn/Pd was about 1.3. During electroless Cu deposition on the catalyzed TaN/SiO2/SiTaN/SiO2/Si substrates, Cu nuclei first formed at the catalytic sites in the early stage, gradually agglomerated into dense islands, and finally merged to continuous deposition films. The Cu films were uniformly and smoothly deposited with a surface roughness of 6.2 nm under a film thickness of 210 nm. The lowest electrical resistivity of the Cu films was 2.5 μΩ cm, and the residual resistivity contributed to the participation of Sn-Pd catalyst and internal defects. Good gap-filling capability of electroless Cu deposition on Sn/Pd catalyzed, patterned substrates exhibited its high potential to act as a seed layer for Cu electrodeposition and even to completely fill submicrometer gaps in ultralarge-scale integrated metallization. © 2002 The Electrochemical Society. All rights reserved.