In-situ spectroscopic ellipsometry for monitoring the TiSi multilayers during growth and annealing

Abstract

The TiSi x formation and properties depend strongly on the deposition and annealing process. We employ spectroscopic ellipsometry (SE) to monitor both processes as well as transmission electron microscopy (XTEM) to verify the above results. The Ti and Si layers were deposited by magnetron sputtering on (100)Si. The multilayer thickness is about 930 Å and the Si Ti ratio ≈ 2.2 , while the thickness of each TiSi bilayer ≈ 120 A ̊ . After deposition of each Ti or Si layer and during annealing of TiSi multilayers up to 680 °C we obtain the SE spectra in the energy region 1.5–5.5 eV. Their analysis and XTEM observations show that during deposition an intermixing of 20 Å width at each TiSi interface occurred. By using SE we found that during annealing below 150 °C there is no drastic intermixing or reaction between Ti and Si. A fast interdiffusion of Ti and a-Si and their reaction is observed between 200 and 580 °C. A phase transition occurs at 580 °C from the amorphous Ti 5Si 3 compound to the C49 TiSi 2 structure and above this temperature XTEM depicts that only structural modification within the interdiffused layers of TiSi is observed.