Stress in Copper thin Films With Barrier Layers

Abstract

AbstractWafer curvature and grazing incidence x-ray scattering (GIXS) techniques were used to investigate the biaxial stresses induced in blanket Cu films during a thermal cycle to 460°C and back to room temperature. Cu was deposited by DC sputtering at ambient temperature. Several different barrier layer materials — SiO2, W, Ta, TiN, and Si3N4 — were used to compare any effect barrier choice might have on Cu microstructure evolution and mechanical behavior. Ta and Si3N4 encouraged a strong (111) Cu texture. A W barrier led to an untextured microstructure which underwent large, uneven grain growth during thermal cycling. Several samples were capped with a Ta layer which affected the stress behavior during cooling by inhibiting dislocation motion. An inverse relationship between strength and thickness was also documented.