PNNL

Abstract

A low temperature carbon dioxide based on immersion deposition technology (SFID) has been developed for producing palladium, copper, silver, and other metal films on silicon-based substrates in supercritical CO2. The reaction is initiated by oxidation of elemental silicon to SiF4 or H2SiF6 by HF with the release of electrons that cause the reduction of metal ions in an organometallic precursor to the metallic form on silicon surface in CO2. Only the substrate surfaces are coated with metals using this method. Based on surface analysis of the films and spectroscopic analysis of the reaction products, the mechanism of metal film deposition is discussed. The metal films (Pd, Cu, and Ag) formed on silicon surfaces by the SFID method exhibit good coverage, smooth and dense texture, high purity and a metallic behavior. Similarly, metal films can also be deposited onto geranium substrates using SFID. The gas-like properties and the high pressure of the supercritical fluids, combined with the low reaction temperature, make this SFID method potentially useful for depositing thin metal films in small features, which are difficult to accomplish by conventional CVD methods.