Silane (gaseous silicon tetrahydride) is a commercially valuable compound with advanced applications in the manufacture of electronic components. It thermally decomposes to yield a layer of ultrapure silicon and hydrogen gas, a reaction that is used industrially in chemical vapor deposition (CVD) applications. CVD offers an alternative to the classical method of fabricating silicon wafer components via slow crystalline growth. Silane CVD is also extensively used to produce silicon dioxide, nitride, and metal silicide thin films.
The primary drawback to the use of silane is the explosive properties of the gas. It readily ignites in air, and when leaked is also prone to cause flashbacks into the reaction process. For reasons of safety and political acceptability, it is desirable for industrial users of silane to minimize the amount of gas in storage and n transit. However, current methods of industrial silane synthesis (typically involving the reduction of silicon tetrachloride by lithium hydride at high temperatures) require centralized production, shipment over long distances, and on-site storage. Such a centralized production and distribution system greatly complicates the safety and regulatory problems associated with silane use.
University of California researchers have discovered compounds and catalysts suitable for synthesizing silane at ambient temperatures, and have also developed improved methods for inactivating excess silane. The UC synthetic reactions are characterized by their adaptability to large-scale production, high yields (97% silane yield for one of them), and use of innocuous air-stable reactants. The inactivation methods involve passing the excess silane through a solid scrubbing system, simplifying the decomposition reaction as compared to the current employment of alkaline media, and giving visual indication of the amount of scrubbing capacity remaining.
Together, the UC silane synthesis and inactivation methods should allow for decentralized, on-site production of silane on an as needed basis. The UC silane technologies can eliminate the need for transport and storage of large quantities of silane, making silane much more attractive in industrial applications.