Precise analysis of H, C, N, and O as dominant impurities in Cu films: complementary use of SIMS and GDMS

Secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (GDMS) were used to determine the impurity concentrations of hydrogen, carbon, nitrogen, and oxygen elements in Cu films, and the results of SIMS and GDMS were carefully interpreted. The Cu films were deposited on Si (100) substrates at substrate bias voltages ranging from 0 V to −150 V using a non-mass separated ion beam deposition method. From the results of SIMS using a Cs⁻ ion beam, as a whole, many high intensity peaks were observed in the Cu films deposited without substrate bias voltage. From the quantitative GDMS results, these peaks were determined to be signals detected as a cluster state such as C_xH_x, O_xH_x, C_xO_xH_x. Therefore, using a combination of these dominant impurities, all the unknown peaks observed in the SIMS results could be interpreted. Moreover, it was found that the dominant impurities having a great influence on the film purity were hydrogen, carbon, nitrogen, and oxygen.