Risk Assessment of Bulk Versus Small Chemical Quantity Transfer During The Manufacture of Semiconductors: A Review Article of Silane Delivery Methods

Risk Assessment of Bulk Versus Small Chemical Quantity Transfer During The Manufacture of Semiconductors: A Review Article of Silane Delivery Methods
Matthew VanWatermulen; University of Minnesota Duluth

Since the introduction of silane into semiconductor manufacture, there have been serious accidents that have caused injury, property damage, and loss-of-life. Silane is a pyrophoric gas used by xerography, glass, photovoltaic, and semiconductor manufacturers. It is utilized in semiconductor manufacture during chemical vapor deposition (CVD) of 150, 200, and 300 millimeter wafers. High pressure systems are widely used in the semiconductor industry to deliver silane to fabrication areas, and are typically delivered in 5 kg cylinders with delivery pressures of 790 psig. Bulk tube trailers have been utilized in xerography, glass manufacture, photovoltaics and have become increasingly prevalent in the semiconductor industry. They typically contain anywhere between one and six metric tons of silane, in eight combined tubes, and are delivered at through a gas cabinet with a pressure of 700 psig. VAC(TM) delivery is a relatively new form of silane delivery that incorporates set-pressure-regulators (SPR) which can be set to sub- and super-atmospheric atmospheric pressures. The standards for silane and its associated delivery methods are controlled by various governmental and local enforcement agencies, in addition to recommendation guidelines set forth by several semiconductor and chemical related organizations. This article provides a comprehensive risk analysis that incorporates previous risk assessments and technical data. The risk of silane delivery as a whole is a function of the delivery pressure and quantity of silane used in process operations. Some of the potential risks of high-pressure delivery include failures during change-out, maintenance, and component failures. Risks associated with bulk tube trailers are concerned with mainly process interruptions, and catastrophic events. These include failures of trailers due to structural damage, and pressure relief devices. VAC(TM) risks include component and human failures, such as those associated with SPR s, damage to the structural integrity of the cylinders, and installation errors. A cost benefit analysis was done to investigate the associated cost impacts between highpressure, bulk tube trailers, and VAC(TM). The analysis revealed that bulk tube trailers were the most cost effective when compare to high-pressure and VAC(TM) using certain protocol. Finally, recommendations of the delivery methods were provided by the author based on research and knowledge obtained through interviews, literature, and technical data.