Investigation of the bonding states of the SiO₂ aerogel film/metal interface

Due to a rapid decrease in the physical dimensions of today's microelectronic devices, the RC-time-delay of the interconnection is now a serious problem. As a possible plan, lower resistive metal or lower dielectric constant material has to be introduced. For a low dielectric constant material, SiO₂ aerogel may be a promising candidate for an interlayer dielectric (ILD) due to its relatively small dielectric constant. However, the formation of a SiO₂ aerogel film on metal substrate may induce a modification of the metal surface because the aerogel film is made by the sol-gel process. Thus, this investigation focused on the interface formation of SiO₂ aerogel film and substrate metal is important for the application of low-k material. It was revealed that aluminum silicate bond during aging of spun-on film was induced at the interface with Al and oxidized Al bond was increased after supercritical drying. Copper silicate bond was formed at the interface of the aged film and maintained after fabrication of SiO₂ aerogel film. Cu(OH)₂ bond, which did not exist at the Cu surface, was generated during film fabrication process. Measurement of leakage current of SiO₂ aerogel film deposited on various substrates indicated the degradation of material property in Al/SiO₂ aerogel/Cu structure.