Knowledge Bank

Infrared tunable diode laser absorption diagnostics of gas phase radical concentrations can yield important information on chemical mechanisms in semiconductor processing systems. Absorption concentration measurements require knowledge of line and band strengths. We have been using fast flow reactor techniques to study the CF2 radical, of interest in plasma etching systems, and the $CH3$ radical, important in metalorganic and diamond chemical vapor deposition systems. $CF2$ concentrations are determined by ultraviolet absorption of 248.4 nm radiation from a KrF excimer laser. $CH3$ radicals are generated by reaction of $CH4$ with F atoms. They are quantified using the known CH3 recombination rate constant by observing their concentration decay with residence time for varying initial concentrations. We will present infrared absorption strength measurements for these radicals and compare these results with recently reported $measurements.1,2$