The bonding energy of Ta and C was measured by in situ x-ray photoelectron spectroscopy during sequential tantalum (Ta) deposition on low-k SiLK(TM). A tantalum carbide layer was found to be formed at the interface between Ta and SiLK(TM) and the thickness was estimated to be less than 1.2 nm. Since the energy peak of pi-pi* shakeup caused by an aromatic ring in SiLK(TM) disappeared after Ta deposition, tantalum carbide was thought to be formed by a minute reaction between Ta and de-bonded aromatic ring in SiLK(TM). (C) 2003 American Vacuum Society.