DEPOSITION PROCESS OF W ONTO A-SI-H OBSERVED IN-SITU WITH POLARIZATION MODULATION IR AND QUADRUPOLE MASS SPECTROSCOPIES

The reaction processes of WF6 with photochemically deposited a-Si:H fi lms were studied in situ by polarization modulation IR spectroscopy an d quadrupole mass spectrometry. The IR bands due to the hydrogenated s ilicon species (-SiH3 and -SiH2) incorporated in the film decreased in intensity during the exposure to WF6. Irrespective of the exposure te mperature, the intensity reduction rates of the -SiH3 species were muc h larger than those of the -SiH2 species. Gas-phase analysis revealed that the evolution of hydrogen into the gas phase took place prior to that of silicon fluorides. Inductively coupled plasma analysis showed that the weight of W deposited on the substrate increased steeply just after the beginning of the exposure, then tended to be saturated beyo nd the exposure time at which the IR bands due to the -SiH3 species al most disappeared. These results indicate that WF6 reacts preferentiall y with the -SiH3 species present in the hydrogen-rich surface layer an d further deposition reaction is strongly suppressed by the W layer fo rmed on the surface.