Influence of the substrate temperature on silicon–carbon thin films deposited from SiH 4 and C 2H 4 by excimer lamp–CVD

Abstract

Amorphous hydrogenated silicon–carbon layers have been prepared on silicon and aluminium substrates by photo-chemical vapour deposition from silane and ethylene by using a Xe 2 * excimer lamp. Films produced at different substrate temperatures have been systematically characterised by ellipsometry, Fourier Transform Infrared Spectroscopy (FTIR), profilometry, Raman Spectroscopy and Energy Dispersive X-ray Spectroscopy (EDS). Ellipsometric studies reveal that the refractive index rises linearly from 1.5 to 2.3 and the deposition rate changes significantly when the substrate temperature is increased. Moreover, EDS analysis indicates an enhancement of the silicon to carbon ratio. Homonuclear silicon and carbon bonds are observed in the Raman spectra, and infrared spectroscopy shows hydrogen incorporated in the films bonded to both silicon and carbon atoms. An atypical increase of the amount of Si–H and a shift of its stretching frequency is found for increasing temperatures. Spontaneous effusion of hydrogen bonded to silicon and a consequent incorporation of oxygen in these vacancies, which provokes a diminution of the refractive index and a shift of the Si–H stretching frequency to higher values, is observed during film aging.