Paper PS-TuM3
Spectroscopic Measurement of Molecular Densities and Temperatures in Processing Plasmas

Tuesday, November 8, 2016, 8:40 am, Room 104B

Processing plasmas are of a similar pressure and temperature to the environment used to study astrophysical species in the submillimeter/terahertz spectral region. Many of the molecular neutrals, radicals, and ions present in processing plasmas have been studied in the laboratory and their absorption spectra have been cataloged or are in the literature for the purpose of astrophysical study. Thus, the methods developed over several decades in the submillimeter spectral region for these laboratory studies are directly applicable for use in the semiconductor manufacturing industry. In this work, a continuous wave submillimeter absorption spectrometer was developed to study its viability as a remote sensor of gas and plasma species. A major advantage of intensity calibrated rotational absorption spectroscopy is that it can be used to determine absolute concentrations and temperatures of plasmas species from first principles without altering the plasma environment. An important part of this work was the design of the optical components which manage the coupling of the 500 – 750 GHz radiation through a commercial inductively coupled plasma (ICP) etch chamber using its existing viewport. A software routine was developed to simultaneously fit for background and absorption signal. The absorption signal determines the concentration, rotational temperature, and translational temperature of polar species. Examples of measurements made in ICPs will be demonstrated.