Behavior of electroless Cu deposition in CuSO4-HF solution

The behavior of electroless Cu deposition on a Cu substrate in CUSO4-HF solution is studied using a Si wafer as anode. The results show that the weight of Cu substrate increases with bath temperature and plating time before reaching a constant value. Both the Cu corrosion by HF and reduction of [Cu2+] on the cathode contribute to the measured weight variation of Cu substrate, which can be described in an equation. The weight gain of Cu substrate decreases with the distance between two electrodes in an exponential way approximately. Cu film is also observed to deposit on the Si wafer during plating. The relationships of the plating time and the weight gain of the Cu substrate reveal that Cu film coated on the Si wafer may prevent the electron diffusion to the cathode. The kinetic research suggests that the activation energy of Cu reduction depends on different experimental conditions and varies from 0.383 to 0.486 eV With the present method, a Cu film is deposited on TiN barrier in the acid-based solution. (c) 2005 The Electrochemical Society. All rights reserved.