Thermodynamic Properties of Trace Water Vapor in High Purity Hydrogen Bromide used for Semiconductor Processing

Abstract

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.

Impurity Amplification in Ultra High Purity Hydrogen Bromide by Water Catalyzed Reactions from Different Cylinder Materials

“…The moisture analysis demonstrated that a large gradient between the liquid and vapor phase HBr is present in the cylinder. Similar results have been observed and modeled in previous studies (5). The liquid phase is known to contain >200ppm/w water as the vapor phase is used and the moisture is left behind during the single stage distillation.…”

“…All experimental conditions for sampling low moisture level HBr were previously validated in previous studies. (5) Gas phase moisture data was collected with a model MTO-1000 CRDS instrument (Tiger Optics, Warrington PA) using the absorption peak at 1392.54 cm -1 which arises from the rotational transition (2,0,2 ← 3,0,3) in the ν 1 + ν 3 (1,0,1 ← 0,0,0) vibrational band of water molecule. The calibration of the instrument was confirmed using a NIST certified H 2 O standard which was verified using a CR-3 chilled mirror hygrometer (Buck Research Instrument, Boulder CO) in nitrogen flow.…”

Cylinder Materials of Construction for Ultra-High Purity HBr in Advanced Semiconductor Etch Processes

“…The gas was sampled at a rate of 0.7 standard liters per minute. The experimental conditions and procedures were established by a previous study determining the thermodynamic properties of trace moisture in HBr (5) ECS Transactions, 13 (8) 71-77 (2008)…”