Ag/Sn Nanoparticles Reduced by Tin(II) Pyrophosphate, Tin(II) Oxalate, and Tin(II) Sulfate for Catalyzing Electroless Copper Deposition

Abstract

Different-sized Ag/Sn nanoparticles were prepared using various tin salts, including tin(II) pyrophosphate, tin(II) oxalate, and tin(II) sulfate, and applied as activators for electroless copper deposition. The transmission electron microscopy and X-ray photon electron spectroscopy data showed Ag nanoparticles of 8.2 and 10.2 nm were prepared and coated by SnOx when tin(II) sulfate and tin(II) oxalate were used, respectively. When tin(II) pyrophosphate was employed, 5.8 nm Ag nanoparticles with a thicker shell composed of SnOx and Sn2P2O7 were obtained. Furthermore, a comparison of the activities and actual deposition rates of these three Ag/Sn nanoparticles was carried out by monitoring the deposition in situ with a quartz crystal microbalance (QCM) and measuring the surface morphology of the deposited layer with a field-emission scanning electron microscope (FE-SEM). The activities and deposition rates observed by QCM had the order Ag/SnP2O7 > Ag/SnSO4 > Ag/SnC2O4, which demonstrated that the size of the Ag nanoparticles controls the activity of electroless copper deposition (ECD), even in the presence of a thick Sn shell. However, the FE-SEM images showed that a thick shell influenced the uniformity of deposited Cu film. Therefore, among these three Ag/Sn nanoparticles, the nanoparticles reduced by tin(II) sulfate showed the best performance as an activator for ECD.