Fiber Optics-Based Fourier Transform Infrared Spectroscopy for in-Situ Concentration Monitoring in OMCVD

Abstract

AbstractFiber-based Fourier transform infrared spectroscopy for remote in-situ monitoring of organometallic delivery in organometallic chemical vapor deposition (OMCVD) is presented. The measurement is based on infrared absorbance of the organometallic reagent in a short single pass gas cell placed in the gas delivery line of an OMCVD system. The performance of the set-up is demonstrated for monitoring concentration transients during the delivery of two common OMCVD precursors, trimethylgallium (TMG) and trimethylindium (TMI). The time to reach saturation is shown to be faster for a TMG bubbler than for a TMI bubbler. This difference in delivery behavior is interpreted through a mathematical model of the gas handling lines and the monitoring gas cell. The utility of the system in monitoring temporal variations in TMI delivery is also demonstrated. Finally, the ability of the system to detect the chemical species unintentionally present in the feed lines is illustrated with the observation of methane gas from TMG and TMI bubblers that have been dormant for a period time. The methane gas is shown to quickly disappear with repeated used of the bubblers.