Chemical Properties
Silicon monoxide (SiO) is another oxide of silicon, used rarely in silicon processing but quite often in thin film, hybrid Ie manufacture. It is useful there because no silicon is available for in situ growth of the dioxide, and it is deposited easily by physical vapor deposition, a process quite similar to the vacuum deposition of aluminum described. Usually the condensed oxide is nonstoichiometric, being a mixture of SiO, Si02, and Si; often, it is designated SiOx .The value of x, which ranges between 1 and 2, is influenced by the deposition conditions.
The SiO source material is prepared by heating Si02 with Si, carbon, and hydrogen, or a hydrocarbon, to reduce the dioxide to the monoxide. Reduction takes place at roughly 1000°C, and SiO is formed in the vapor phase. This temperature is much too low to produce a significant vapor pressure of Si02, so the two oxides may be separated. The monoxide vapor is condensed out and subsequently powdered. This material, which is suitable for evaporation, is available commercially and need not be prepared by the IC manufacturer.
