Spectroscopic ellipsometry investigation of silicide formation by rapid thermal process

Abstract

Titanium, cobalt, and nickel silicides have been considered as self-aligned silicides (salicides) for contact and interconnect metallization in ultralarge scale integrated circuits. A CoSi2 salicide process using TiN or Ti capping, which is superior to the conventional cobalt salicidation, has been found to be a good solution for producing a lower sheet resistance value and a tighter sheet resistance distribution. In this work cobalt silicidation with and without a TiN and Ti cap has been performed in temperature range of 300–800 °C. In order to extensively study the phase sequence of silicide formation, a spectroscopic ellipsometry (SE) technique has been used to characterize the thin silicide films. The measurement of the optical properties and thicknesses of thin cobalt, stacked TiN/Co, and cobalt silicide layers has been compared with four point probe measurements. Also, a technique employing a SE optical method has been successfully developed to measure the thickness of thin Co and CoSi films and the selective etch rates of TiN and CoSi, which showed 0.45 and 0.009 nm/s, respectively, for TiN capped Co silicidation. The results obtained by the SE nondestructive technique are also compared with the results of Rutherford backscattering spectrometry.