INTERACTION OF FREE-RADICALS WITH SOLID SURFACES AS STUDIED BY FLUORESCENCE-IMAGING METHOD WITH CROSSED BEAMS

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In order to understand the kinetics of neutral radical reactions in plasma-and photo-excited material processing, we performed in-situ diagnostics of their reactions on the solid surfaces. As the first step, we built suitable radical sources driven by RF- and MW-discharges. We established also highly-sensitive methods to measure the densities and fluxes of effused radicals from these sources by using laser induced fluorescence spectroscopy (LIF), intra-cavity laser absorption spectroscopy (ICLAS) and so on. Among the successfully detected radicals are Si-containing radicals such as Si, SiH and SiH_2 and atomic radicals such as H, O and N.Firstly, the reactions of SiH_n(n=0-2) have been studied in the deposition of hydrogenated amorphous silicon (a-Si:H). From a comparison of characterized incident flux of these radicals and the measured optical and electrical proper-ties of the deposited films the reaction mechanisms involved in the deposition have been discussed. The obtained result is also consistent with a computer simulation of our proposed surface reaction model. Secondly, the mechanism of low temperature oxidation of silicon wafer surface has been studied using an oxygen radical source, in which the enhancement of oxidation has been correlated with the flux of oxygen atoms and electronically excited oxygen molecules.