Properties of Process Gases Determined Accurately With Acoustic Techniques

Published

November 1, 1998

Author(s)

John J. Hurly

Abstract

Our laboratory has developed a highly precise, automated apparatus for measuring sound speeds, viscosity, and thermal conductivity in hazardous and/or corrosive process gases throughout the temperature and pressure ranges of interest to the semiconductor processing community. The sound speeds are determined from resonances within a cylindrical cavity (or resonator) filled with the sample gas. The resonator is thermostated to within a few millikelvin between 200 K {less than or equal} T {less than or equal} 480K. The pressure range is 0.05 MPa {less than or equal} P {less than or equal} 1.5 MPa, or 80% of the samples' vapor pressure whichever is lower. The Analysis of sound speeds provides the perfect gas heat-capacities, C^O_p(T), and the non-idealities of these gases. The viscosity and thermal conductivity are determined in similar resonators with geometries optimized for measuring energy losses. These thermophysical properties are required by the semiconductor processing industry to model processes, and to calibrate mass flow controllers (MFCs). The actual calibration of the MFCs is performed with nonhazardous surrogate gases, which we are also characterizing. We have obtained extensive sound speed data for the surrogate gases SF₆, CF₄, C₂F₆ and the semiconductor gas BCl₃. These results and their analysis are presented.

Conference Dates

March 23-27, 1998

Conference Title

International Conference on Characterization and Metrology for ULSI Technology

Pub Type

Conferences

Keywords

equation of state, heat capacity, sound speed, virial coefficient

Citation

Hurly, J. (1998), Properties of Process Gases Determined Accurately With Acoustic Techniques, International Conference on Characterization and Metrology for ULSI Technology (Accessed December 13, 2024)