Abstract
Self-assembled monolayers (SAMs) are investigated as potential Cu diffusion barriers for application in back-end-of-line (BEOL) interconnections. A screening of SAMs derived from molecules with different head group (SiCl 3, Si(OCH 3) 3, Si(OCH 3)Cl 2) bonding to the dielectric substrate, chain lengths ( n = 3–21) and terminal group (CH 3, Br, CN, NH 2, C 5H 4N and SH) bonding to the Cu overlayer are compared in terms of inhibition of interfacial Cu diffusion and promotion of Cu–SiO 2 adhesion. SAM barrier properties against Cu silicide formation are examined upon annealing from 200 to 400 °C by visual inspection, sheet resistance measurements (Rs) and X-ray Diffraction Spectroscopy (XRD). Cu/SAM/SiO 2 adhesion is evaluated by tape test and four-point probe measurements. Results indicate that NH 2-SAM derived from 3-aminopropyltrimethoxysilane is the most promising for Cu diffusion barrier application. Silicide formation is inhibited to at least 400 °C, essential stability for BEOL integration. However, the 2.9 Gc (J/m 2) adhesion of the layer compared with 3.1 Gc (J/m 2) on SiO 2 does need improvement.
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