The effects of additives such as acids and surfactants on copper outplating onto silicon surfaces from dilute HF solution were studied. It was found that some additives could significantly reduce copper outplating. Results from potentiommetry, total-reflectance X- ray fluorescence, time- of- flight - secondary ion mass spectroscopy, dynamic light scattering, and electron microscopy suggested that the anionic surfactant had strong interaction with cupric ions in solution, and their complex was adsorbed onto silicon surfaces, causing nonredox-type copper contamination. Dynamic light- scattering results also revealed strong interaction between the anionic surfactant and nickel ions. The roles of surfactants in copper outplating are discussed in this paper. (C) 2004 The Electrochemical Society.