Ta and Ta–N diffusion barriers sputtered with various N2/Ar ratios for Cu metallization

Abstract

Ta and Ta–N films sputtered with pure Ar, 10%, 20%, 30%, 40%, 50%, and 60% N2/Ar gas ratios were found to be a mixture of β-Ta and bcc-Ta, bcc-Ta, bcc-TaNx, expanded bcc-TaNx, hcp-Ta2N, fcc-TaN, and fcc-TaN (nearly amorphous) phases, respectively. The resistivity was found to be lowest in samples sputtered with 10% N2/Ar and increase with nitrogen content in samples deposited with 10% to 60% N2/Ar. For Cu layers deposited on these films, the growth orientations were found to depend strongly on the microstructures of underlying Ta and Ta–N films. The Cu (111)/(200) ratio was decreased with the nitrogen content of Ta–N films.