Cu penetration into low-k dielectric during deposition and bias-temperature stress

Abstract

Cu penetration into low-k dielectrics can cause serious reliability issues in on-chip interconnect systems. Using secondary ion mass spectrometry with both front-side and back-side depth profiling strategies, Cu was found to diffuse into SiCOH low-k dielectric in a Cu/SiCOH/Si capacitor during Cu deposition. After bias-temperature stressing the capacitor at 270 °C and 2.5 MV/cm, Cu penetrates further into SiCOH, but its distribution profile is the same as that after the same temperature annealing without electrical bias, suggesting no Cu ion drift. The implication of these findings on the Cu/low-k dielectric time-dependent dielectric breakdown modeling is discussed.