Thermal Stability Study of Cu(MoN_(x)) Seed Layer on Barrierless Si

摘要

This study reports the good thermal stability of a sputtered Cu(MoN_(x)) seed layer on a barrierless Si substrate. A Cu film with a small amount of MoN_(x) was deposited by reactive co-sputtering of Cu and Mo in an Ar/N_(2) gas mixture. After annealing at 560 deg C for 1 h, no copper silicide formation was observed at the interface of Cu and Si. Leakage current and resistivity evaluations reveal the good thermal reliability of Cu with a dilute amount of MoN_(x) at temperatures up to 560 deg C, suggesting its potential application in advanced barrierless metallization. The thermal performance of Cu(MoN_(x)) as a seed layer was evaluated when pure Cu is deposited on top. X-ray diffraction, focused ion beam microscopy, and transmission electron microscopy results confirm the presence of an approx10-nm-thick reaction layer formed at the seed layer/Si interface after annealing at 630 deg C for 1 h. Although the exact composition and structure of this reaction layer could not be unambiguously identified due to trace amounts of Mo and N, this reaction layer protects Cu from a detrimental reaction with Si. The Cu(MoN_(x)) seed layer is thus considered to act as a diffusion buffer with stability up to 630 deg C for the barrierless Si scheme. An electrical resistivity of 2.5 (mu)(OMEGA) cm was obtained for the Cu/Cu(MoN_(x)) scheme after annealing at 630 deg C.