MODIFICATION OF SILICON-CARBON FILM PROPERTIES UNDER HIGH-ENERGY ION-BEAM IRRADIATION

Changes induced to the properties of amorphous hydrogenated silicon-ca rbon layers by 2 MeV He-4(+) ion irradiation during Rutherford Backsca ttering Spectrometry (RBS) and Elastic Recoil Detection Analysis (ERDA ) measurements are reported. Thin films have been deposited at low tem peratures ranging from 60 degrees C to 300 degrees C by photo-CVD usin g a Xe-2(+) excimer lamp from different gas mixtures (acetylene, ethyl ene, silane and disilane), Additional techniques, such as ellipsometry and infrared spectroscopy have been employed to complete the film cha racterization. Hydrogen is removed from the material during the sample irradiation, and an exponential decrease of the ERDA counts with incr easing the number of ions impinging the surface is observed. Ellipsome tric measurements reveal that this effect depends on the film properti es, since for films produced from ethylene and disilane, a linear rela tionship between the relative amount of the removed hydrogen and the i ndex of refraction was found. It is known that silicon carbide present s an aging process when exposed to atmospheric conditions, consisting basically of film oxidation and the consequent diminution of the refra ctive index values, The effects of the ion beam irradiation on the phy sico-chemical structure of the films and their aging process are also reported. (C) 1998 Elsevier Science B.V.