A novel low-temperature chemical vapour deposition (CVD) process has been developed by using hydrogen-atom reactions with metal compounds to produce copper thin films for ULSI applications. High-purity copper films, with low resistivity, good step coverage and strong adhesion to various substrates were obtained by using hydrogen-atom assisted CVD with CuCl at 200 degrees C, and with beta-diketonate copper (II) complexes Cu(fod)(2) and Cu(hfa)(2) at 100-150 degrees C. Gas-phase Cu atoms (10(10)- 10(11) cm(-3)) and concentration as a function of time were measured in-situ by atomic absorption spectroscopy during deposition. The diatomic molecule CuF was measured by atomic emission spectroscopy using oxygen-atom reactions with beta-diketonate copper (II) complexes Cu(fod)(2) and Cu(hfa)(2). Thermodynamic calculations of enthalpy, Delta H-o showed that these reactions were exothermic and spontaneous at room temperature. The spectroscopy measurements of Cu atoms and CuF diatomic molecules in the reaction were studied as a means to develop insight into the gas-phase reaction. The reaction mechanisms were evaluated on the basis of atomic absorption spectroscopy measurements.