Supercritical fluid immersion deposition: a new process for selective deposition of metal films on silicon substrates

Supercritical CO2 is used as a new solvent for immersion deposition, a galvanic displacement process traditionally carried out in aqueous HF solutions containing metal ions, to selectively develop metal films on silicon substrates. Components of supercritical fluid immersion deposition (SFID) solutions for fabricating Cu and Pd films on silicon substrates are described along with the corresponding experimental setup and procedures. Through this method, only silicon surfaces exposed to SFID solutions can be coated. The highly pressurized and gas-like supercritical CO2, combined with the galvanic displacement property of immersion deposition, enables the SFID technique to deposit metal films selectively in small features. Annealing of thin palladium films deposited by SFID can lead to the formation of palladium silicide in small features on silicon substrates.