Spectroscopic ellipsometry investigation of silicide formation by rapid thermal process

Titanium. cobalt, and nickel silicides have been considered as self-aligned silicides (salicides) for contact and interconnect metallization in ultral arge scale integrated circuits. A CoSi2 salicide process using TiN or Ti ca pping, which is superior to the conventional cobalt salicidation, has been found to be a good solution for producing a lower sheet resistance value an d 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 degrees C. In order to extensively study the phase sequence of s ilicide formation, a spectroscopic ellipsometry (SE) technique has been use d to characterize the thin silicide films. The measurement of the optical p roperties and thicknesses of thin cobalt, stacked TiN/Co, and cobalt silici de layers has been compared with four point probe measurements. Also, a tec hnique employing a SE optical method has been successfully developed to mea sure the thickness of thin Co and CoSi films and the selective etch rates o f TIN and CoSi, which showed 0.45 and 0.009 nm/s. respectively, for TiN cap ped Co silicidation. The results obtained by the SE nondestructive techniqu e are also compared with the results of Rutherford backscattering spectrome try. (C) 1999 American Vacuum Society. [S0734-211X(99)06805-5].