Optical Properties of Metal Films and Their Silicides

Abstract

ABSTRACTSilicides are used widely in microelectronic fabrication, yet there are very little data available regarding their optical constants at most wavelengths, and specifically at those of interest to G-line and I-line lithography. We have studied extensively the optical properties of Ti, Co, as metal films and as silicide films formed at various temperatures, and of CVD (chemical vapour deposition) W. Using spectroscopic ellipsometry at two angles of incidence, we have calculated the complex index of refraction N = (n, k) of these films every 10nm at 68 wavelengths between 230 and 900nm. These data are necessary to model accurately the reflectivity of wafers to study the effects of various thermal and surface treatments on silicide growth and to set exposure times for lithography. They also allow the use of reflectivity vs X as a non-contact method to map film thicknesses across wafers within the patterned devices themselves.