A robust k ∼ 2.3 SiCOH low-k film formed by porogen removal with UV-cure

Aurora (R) ELK films were fabricated by PE-CVD of a SiCOH matrix precursor and an organic porogen material. The porogen material is removed during a subsequent thermally assisted Uv-cure step with a short wavelength UV-lamp (lambda < 200 nm). This results in film thickness shrinkage of 13.2% and a robust low-k film with k-value similar to 2.3, elastic modulus similar to 5.0 GPa and intrinsic film stress similar to 59 MPa. The microscopic film properties during UV-cure were evaluated by FT-IR. A decrease in the CH, peak area is related to the porogen removal from the film resulting in a reduced dielectric constant. The decrease of the Si-CH3 peak and increase in the SiO network area are associated to the network restructuring and increase in elastic modulus. The nature of the Si-H peaks which appear during UV-cure has to be investigated carefully to determine their impact on film reliability. The dielectric diffusion barrier can work as an UV absorption layer which reduces UV-curing of underlying layers and possible UV reflections on interfaces. The SiCN/A-SiCO diffusion barrier film properties during UV-cure show a decrease in k-value, increase in intrinsic film stress and a slight increase in leakage. More research is needed to evaluate the impact of porogen removal by UV-cure on BEOL integration. (C) 2007 Elsevier B.V. All rights reserved.