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

The TiSix 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 Angstrom and the Si/Ti ratio approximate to 2.2, while the thickness of each Ti-Si bilayer approximate to 120 Angstrom. After deposition of each Ti or Si layer and during annealing of Ti-Si multilayers up to 680 degrees 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 Angstrom width at each Ti-Si interface occurred. By using SE we found that during annealing below 150 degrees 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 degrees C. A phase transition occurs at 580 degrees C from the amorphous Ti5Si3 compound to the C49 TiSi2 structure and above this temperature XTEM depicts that only structural modification within the interdiffused layers of Ti-Si is observed.