LOW-ENERGY ELECTRON-BEAM-ENHANCED FORMATION OF ULTRATHIN INSULATING SILICON OXYNITRIDE LAYERS ON SI(100) AT MODERATE TEMPERATURES - IN-SITUDETERMINATION OF THE BAND-GAP ENERGY USING ELECTRON-ENERGY-LOSS SPECTROSCOPY

Exposure of a Si(100)-2 X 1 surface to low pure NO gas pressures (less than or equal to 8 X 10(-6) mbar) at moderate temperatures (room temp erature (RT) - 600 degrees C) leads to the formation of an amorphous p assivating oxynitride layer (thickness similar to 0.5 nm). However, we show that low energy (100 eV) electron bombardment of the surface, du ring exposure to NO, induces the formation of amorphous ultrathin (les s than or equal to 2 nm) silicon oxynitride films having different ele mental compositions. At RT, oxygen-rich films were grown, while nitrog en-rich layers were formed at 600 degrees C. This result confirms rece nt published data where synchrotron radiation (thermal activation) at RT (above 1000 degrees C) was found to be an efficient promoter of the oxidation (nitridation) of silicon using low pure NO gas pressures. T he thickness and the composition parameter 0/(0 + N) of the resulting insulating layers have been deduced from Anger electron spectroscopy ( AES) measurements. The band gaps of various ultrathin films already fo rmed have been determined in situ using reflection electron energy los s spectroscopy (EELS). For this purpose, the true N(E) distributions o f inelastically-backscattered electrons have been deduced, using a num erical procedure, from EELS spectra recorded by means of a standard si ngle-pass cylindrical mirror analyzer operated in the pulse counting m ode.