Effect of liquid additives in supercritical fluid deposition of copper for enhancing deposition chemistry

Four liquid chemical reagents (ethanol, 2-propanol, hydrogen peroxide, and formic acid) were evaluated as reducing agents for supercritical fluid deposition of Cu (Cu-SCFD) using bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper as a precursor onto a Ru-coated Si substrate for ultra large scale integration metallization. Deposition was carried out using a batch-type reactor and heating the substrate from 40 °C to 250 °C at a rate of 4.5 °C/min. 2-propanol and hydrogen peroxide yielded Cu grains, but not a continuous Cu film. Only formic acid yielded a high-purity continuous film. Solvent effect of two chemical reagents (ethanol and 2-propanol) on Cu-SCFD with H2 as a reducing agent was also investigated by using in situ method, in which optical reflectivity of growing surface at wavelength of 770 nm was used. Ethanol addition enhanced the deposition reaction without degrading both the surface morphology and high purity of the deposited Cu film.