A study on Cu diffusion to sol-gel derived low-k films

Organically modified low dielectric constant films were synthesized via sol-gel technique. The interaction between copper interconnect and sol-gel films with different porosity was investigated using Cu/low-k film/n⁺ Si metal insulator metal capacitors. Tape test showed that the copper adhered better to the films after annealing. The electrical properties of Cu/low-k film/n⁺ Si capacitors were characterized and compared to those of Au/Ti/low-k film/n⁺ Si capacitors. The dielectric constant and leakage current of the as-deposited and annealed Cu capacitors were found to be similar to those of the Au/Ti capacitors. The conduction mechanism analysis suggested that the carriers of both Cu capacitors and Au/ Ti capacitors had the same Schottky emission. These results indicated that there was no significant Cu diffusion through the organosilicate films even for the film with porosity as high as 73% under the experimental conditions. The interface stability indicates that both adhesion promoting layer and diffusion barrier with higher dielectric constant perhaps can be avoided for these sol-gel derived low-fc films.