Porphyrin Self-Assembled Monolayer as a Copper Diffusion Barrier for Advanced CMOS Technologies

This paper investigates properties of zinc porphyrin self-assembled monolayer (SAM) as a Cu diffusion barrier for advanced back-end complementary metal-oxide-semiconductor technologies. The SAM layers are integrated with various inter-layer dielectrics (ILDs) such as HSQ and black diamond (BD). Monolayer formation on ILDs was studied using X-ray photoelectron spectroscopy, atomic force microscopy, contact angle, FTIR, and UV-Vis techniques. Degradation study of the Cu/ILD and Cu/SAM/ILD systems was performed using stress-induced CV and IV at elevated temperatures. Time-of-flight secondary ion mass spectrometry was employed to establish effectiveness of these films as Cu diffusion barriers. The results indicate that SAM films, in addition to improving the ILD´s moisture resistance, may help in thinning down the existing barrier layer thickness on the low-k porous ILDs. Effect of SAM layers on the mechanical properties of BD film was studied using nanoindentation.