In situ Fourier-transform infrared measurements have been carried out to study the effects of Pi atoms on removing impurities in Cu thin films during plasma enhanced metal organic chemical vapor deposition (PEMOCVD) using bis(hexafluoroacetylacetonato) copper (II), Cu(hfac)(2) as a source material. The results show that H atoms are very effective in removing impurities in the film, as well as on its surface. Based on such knowledge regarding the effects of I-I atoms, a PEMOCVD reactor equipped with an H atom source is developed to control both densities of H atoms and Cu-contained radicals independently. High purity (approximate to 100%) Cu films of a low resistivity of 2 mu Omega cm can be deposited for a H-2 gas volume fraction of 50%-67% by using the H atom source, while the high purity films were obtained only for a very high H-2 gas volume fraction above about 90% in the case of no H atom source as reported previously. This feature opens up a possibility of deposition of high quality Cu films at a high rate using the reactor equipped with the I-I atom source, since a gas volume fraction of Cu metal organic material can be increased by more than five times.