Porphyrin self-assembled monolayer as a copper diffusion barrier for advanced CMOS technologies

Abstract

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.