Plasma process monitoring of BCl3 using high-resolution infrared laser absorption spectroscopy

Boron trichloride (BCl3) is used as a source gas in various industrial plasma applications. The online monitoring of its ground state concentration in the plasma process reactor is vital for improved insight into the plasma chemistry and to increase productivity, reliability and reproducibility of the process. Infrared absorption spectroscopy was applied for in situ measurements of absolute densities of BCl3 and HCl in planar microwave plasma sources as well as in an industrial pulsed dc discharge reactor. In this paper procedures for the determination of HITRAN format line strength data files for BCl3 are described together with results of concentration measurements. The results show the influence of the discharge parameters on the dissociation of BCl3 and its conversion to HCl. Observations using tuneable diode lasers are compared with measurements using quantum cascade lasers and the applicability of this diagnostic technique for industrial plasma process monitoring is shown.