ADSORPTION OF MOLECULAR FLUORINE ON THE SI(100) SURFACE - AN ELLIPSOMETRIC STUDY

The kinetics of the formation of an adsorption layer on a Si(100) surf ace under the action of fluorine molecular flow has been studied in th e temperature range 214-873 K with an automatic ellipsometer operating at a wavelength of 0.6328 mu m, which was coupled with an ultra-high vacuum chamber with the evacuation system (10(-7) Pa) and F-2 vapour s upply. Three types of adsorption states were found to be consecutively occupied during F-2 adsorption on the Si(100) surface. The adsorption states of the first type are non-activation ones. The activation ener gy of the states of the second type is 7.5 +/- 1.5 kcal/mol, and that of the third type - 12 +/- 2 kcal/mol. Only the states of the first ty pe are occupied at T < 250 K, the states of both the first and the sec ond type are occupied at 250 < T < 450 K, and all three types at T > 4 50 K. Maximum saturation of the adsorption layer with F atoms was obse rved at T approximate to 550-600 K. The adsorption layer was not remov ed after the F-2 flow had been shut-off and the chamber had been evacu ated at T < 650 K. At T > 650 K, the desorption of the adsorption laye r was observed, and the adsorption layer was not formed during the etc hing of the Si surface in the F-2 flow at T approximate to 873 K. Sili con surface is polished by etching with F-2 gas.