The distribution of water between gas and liquid phases was investigated for high purity HBr cylinders, and standard enthalpy of vaporization and Henry's law constant for trace amount of water in HBr were extracted. In the 3-32 {degree sign} C temperature range, the water vapor concentration in the gas phase of a cylinder is a function of cylinder temperature and the enthalpies of vaporization of water and HBr. The standard enthalpy of vaporization for trace amount of H2O in HBr was found to be 58.5 kJ/mol. The temperature dependent Henry's law constant can be expressed as: ln K(T) = -7031.44/T + 22.38. Using the thermodynamic parameters found, water vapor concentration measured for gas-phase HBr from cylinders at various temperatures can be normalized to corresponding levels at a chosen standard temperature, e.g. 21{degree sign}C. This is very important in establishing meaningful water vapor specifications, and trustworthy quality control protocols for high purity HBr gas.
Anhydrous HBr used in etch processing for the semiconductor industry requires strict impurity control. However, the gas cylinder material of construction plays a critical role in controlling and maintaining purity levels of the delivered HBr process gas and must be carefully selected. In this work Ni-lined AISI 4130 Cr-Mo steel cylinders are compared against the gas industry standard AISI 4130 Cr-Mo steel cylinders with regard to (a) surface roughness/area and oxide layer thickness after exposure to HBr and (b) the concentration of moisture in delivered HBr gas. Over the period of a year, the surface roughness increase of the polished Cr-Mo steel package doubles that of the Ni-lined package and the penetration of the oxide layer into the metal for the Cr-Mo steel is over 10 times that for the Ni surface. Finally the more inert surface of the Ni lining is shown to lower the moisture concentration in the HBr gas by ~4 times. These findings demonstrate that Ni-lined AISI 4130 Cr-Mo steel provides a superior package for Ultra High Purity HBr storage and delivery.
Anhydrous HBr used in reactive ion etch chemistries for the semiconductor industry requires strict control of impurities over time. Proper selection of cylinder materials strongly influences the purity of the HBr over the shelf life of the stored gas. In this work Ni-lined AISI 4130 Cr-Mo steel cylinders are compared to the gas industry standard AISI 4130 Cr-Mo steel cylinders and 316L SS cylinders regarding the generation of atmospheric impurities over the shelf life of the cylinders. In addition an accelerated aging process of water doping was executed to determine variances between materials. Over the period of 18 months, significant amounts of atmospheric impurities such as CH4, CO2, and H2 were generated in the water doped cylinders. However, the Ni lined cylinders inhibited the atmospheric impurity generation by as much as 20 times, compared to the Cr-Mo steel or 316L SS cylinders in the accelerated study. A similar affect was observed in the standard non-accelerated study. These results demonstrate that Ni lined Cr-Mo steel provides a superior package for anhydrous HBr, due to superior contamination control.
The formation of trace moisture by exposure of dry heated surfaces of 316 L stainless-steel, Restek Silcosteel®, and nickel 1/8 in. outer diameter line segments to purified Ar and H2 was studied using atmospheric pressure ionization mass spectrometry at flow rates of 2 slpm. Prior to H2 exposure, adsorbed moisture was removed by heating incrementally to 500 °C in an argon matrix, where the Restek Silcosteel® material released a maximum of 50 ppb moisture at 300 °C and moisture spikes from the Ni and stainless-steel surfaces reached several 100 ppb. Upon exposure to H2, persistent low ppb moisture emissions due to the reduction of surface oxide species were observed at temperatures as low as 100 °C. Spikes at 300–500 °C ranged from ∼100 ppb for the stainless-steel lines to 400 ppb for the Restek Silcosteel® material. The observed moisture emissions have to be considered as a potential contamination source for high-purity processes utilizing H2 purge at elevated temperatures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.