X-ray photoelectron spectroscopic characterization of the adhesion behavior of chemical vapor deposited copper films

Adhesion behavior of chemical vapor deposited (CVD) copper (Cu) films on va rious barrier substrates was studied using a pull-off test. The mean adhesi on strength of Cu films on air-exposed physical vapor deposition (PVD) Ta, air-exposed CVD TiN, in situ PVD TiN, and in situ CVD TiN were determined t o be 3.42, 4.74, 4.64, and 10.24 MPa, respectively. The adhesion of Cu film s on the in situ PVD TiN exhibited almost the same strength as the adhesion on the air-exposed CVD TiN. Root-mean-squared (rms) roughness values for a ir-exposed CVD TiN and in situ PVD TiN are 8.06 and 1.18 tun, respectively. The rougher surface morphology of the air-exposed CVD TiN films was consid ered to improve adhesion due to mechanical anchoring. The adhesion strength of the Cu film on the in situ CVD TiN was two times higher than that on th e air-exposed CVD TiN. In order to examine the adhesion difference, x-ray p hotoelectron spectroscopy (XPS) measurement was performed on the exposed in terface after pulling off the Cu film. The XPS results showed that on the i n situ barrier Cu(OH)(2) was formed at the surface, but on the air-exposed barrier Cu(OH)(2) was not formed. Consideration of the Ti 2p spectra and th e Cu 2p spectra indicated that the native oxide composition of the barrier surface affects the adhesion characteristics in the same way as the oxidati on resistance of the Cu atoms. Since the amount of residual F was only 3 to 4 at. % at the interface, the effect of F on the adhesion was not as impor tant as that of the native oxide. (C) 2001 American Vacuum Society.