Deposition and Characterization of 3-Aminopropyltrimethoxysilane Monolayer Diffusion Barrier for Copper Metallization

Diffusion barrier capability of 3-aminopropyltrimethoxysilane (APTMS) against the diffusion of copper into the dielectric is studied. A self-assembled monolayer (SAM) of APTMS was deposited on SiO2/Si substrate. Cu/SiO2/Si and Cu/SAM/SiO2/Si test structures were compared for their thermal stability using X-ray diffraction (XRD) characterization, sheet resistance variation, and Capacitance-Volatage (C-V) characterization. The samples were annealed at different temperatures starting from 473 K (200 degrees C) up to 973 K (700 degrees C) in vacuum for 30 minutes each. XRD results indicated that combination of SiO2/SAM worked as diffusion barrier up to 873 K (600 degrees C), whereas SiO2 alone could work as a barrier only up to 673 K (400 degrees C). Sheet resistance of these samples was measured as a function of annealing temperature, which also supports XRD results. C-V curves of these structures under the influence of biased thermal stress (BTS) were analyzed. BTS was applied with different parameters, i.e., 1.25 MV cm(-1) at 323 K (50 degrees C), 1.25 MV cm(-1) at 373 K (100 degrees C), and 2.5 MV cm(-1) at 423 K (150 degrees C). A change in threshold voltage (Delta V-t) was observed for each BTS. Results showed that in the case of higher electric field, i.e., 2.5 MV cm(-1) at 423 K (150 degrees C), V-t of the Cu/SiO2/Si/Al structure was changed significantly even after 15 minutes of stress, while V-t of the Cu/APTMS/SiO2/Si/Al structure was almost unchanged for up to 60 minutes. (C) The Minerals, Metals & Materials Society and ASM International 2014