Raman spectroscopy of silicide formation at the Pt/crystalline Si interface

Abstract

Raman spectroscopy has been used to characterize the formation of Pt-silicide on the Si(100) and (111) surfaces. 5–200 Å Pt overlayers were deposited on atomically clean Si surfaces, reacted and studied by photoemission, Auger spectroscopy and transmission electron microscopy (TEM). The Raman spectra were obtained with a multichannel Raman system; this allowed direct measurements of very thin overlayers on crystalline surfaces. For interfaces reacted at T>300 °C, the Raman spectra showed new lines; the strongest at 82 and 140 cm−1. These are assigned to PtSi by correlation with the TEM phase identification. The relative intensities of the PtSi Raman lines depend on the Pt thickness and the Si substrate orientation. For T<200 °C, these features are broadened and weaker, suggesting a limited (incomplete) reaction. This is consistent with the electron spectroscopy and TEM measurements on these samples. Our measurements show Raman spectroscopy can be used for silicide interface studies to identify and characterize (without extra sample preparation) thin reacted layers, even at the buried interface between unreacted metal and crystalline Si.