METROLOGY OF SUB-0.5 MU-M SILICON EPITAXIAL-FILMS

Non-destructive thickness measurement of sub-0.5 mu m silicon epitaxia l films has been performed using spectroscopic ellipsometry (SE) in th e near infrared to visible range (0.75-3 eV). The undoped epitaxial fi lms were grown on heavily doped substrates by chemical vapor depositio n at 700-900 degrees C. The effect of heavy doping on the optical prop erties of crystalline silicon in the spectral range 0.75-3 eV is preci sely described by the Drude free carrier model. It is shown that SE ca n simultaneously determine the substrate dopant concentration, the thi cknesses of the epitaxial film and native oxide, and if present, the t hickness of the transition layer between the epitaxial film and the su bstrate. The epitaxial film thicknesses measured by SE were in excelle nt agreement with results of secondary ion mass spectrometry (SIMS). T he substrate dopant concentrations measured by SE also agree well with SIMS results for n-type substrates, but are consistently higher than SIMS values for p-type substrates. It was also demonstrated that SE ca n be used for process monitoring in low temperature silicon epitaxy. T his study identifies a non-destructive thickness measurement technique for sub-0.5 mu m silicon epitaxial films which are expected to be wid ely used in future semiconductor devices. (C) 1998 American Vacuum Soc iety. [S0734-2101(98)03904-9].