STABILITY OF INTERFACES IN MO CU MULTILAYERED METALLIZATION/

Mo/Cu multilayered metallizations with less than or equal to 10 Cu con ducting layers of various thicknesses separated by Mo diffusion barrie rs 20 nm thick were deposited, by magnetron sputtering onto oxidized S i wafers. The samples were annealed for 1 h in the vacuum of 10(-3) Pa at temperatures between 400 degrees C and 800 degrees C and in a N-2 atmosphere at temperatures up to 700 degrees C. Rutherford backscatter ing spectroscopy, X-ray diffraction in both standard and grazing incid ence configurations, scanning electron microscopy, electron diffractio n spectroscopy and resistometry were employed to analyse the samples. Two mechanisms are assumed to be responsible for intermixing in immisc ible Mo/Cu multilayers: grain boundary diffusion and the formation of Mo and Cu nitrides in nitrogen environment. In the nitrogen ambient th e multilayer intermixed completely even at 500 degrees C, In vacuum th e 20 nm thick Mo layer was found to be an effective barrier against Mo /Cu intermixing up to 600 degrees C/1 h annealing. Only a small increa se (less than or equal to 20%) of the multilayer resistance was record ed in the samples annealed in vacuum. Cu-enriched hillocks appeared on the surfaces of samples annealed at greater than or equal to 500 degr ees C.