X-Ray Absorption Studies of Titanium Silicide Formation at the Interface of Ti Deposited on Si
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X-RAY ABSORPTION STUDIES OF TITANIUM SILICIDE FORMATION AT THE INTERFACE OF Ti DEPOSITED ON Si. D.B. Aldrich*, R.W. Fiordalice*+. H. Jeont, Q. Islam*, R.J. Nemanich*t, and D.E. Sayers* * Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 t
Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 25695 + Current Address; Motorolla APRDL, Austin, TX 78721
ABSTRACT Near edge X-ray absorption spectra (XANES) have been obtained from the Ti K-edge for several series of titanium silicide samples produced by different techniques. Samples were fabricated by depositing Ti on silicon wafers and subsequently annealing them up to temperatures from 100°C to 900°C in UHV, vacuum furnace, or in a Rapid Thermal Annealing system. Measurements were done in the fluorescence and total electron yield modes. The XANES measurements were correlated with Raman scattering measurements. The XANES data of several reference compounds were obtained, and the data showed a high sensitivity to changes in the film structure. Ti metallic bonding and Ti-Si bonds can be distinguished and their evolution as a function of annealing is related to previous results. For the samples with increased impurities, Ti regions were stable at higher temperatures. The XANES spectra of samples annealed under N2 indicate the formation of a surface nitride.
INTRODUCTION
The focus of this paper is on the application of X-ray absorption near edge spectroscopy (XANES) to study the stages of titanium silicide formation during the reaction of a Ti film with a Si substrate. Previous studies have indicated that at low temperature (-200'C), interdiffusion occurs at the Ti-Si interface, and a disordered intermixed phase forms at the interface. At -450°C, the metastable C49 phase of TiSi2 nucleates, while at temperatures greater than 650°C, the film transforms to the stable C54 phase of TiSi 2 [1-5]. In this study the XANES and Raman spectral signatures of different silicides and oxides are identified, and used to examine the structures which form during the titanium silicon reaction. The XANES measurements are sensitive to local atomic configurations while the Raman spectra displays the vibrational modes associated with different crystal structures. Raman spectroscopy has proved to be a very useful probe of the different crystalline structures which form from annealing of Ti/Si structures [6]. Spectra associated with both C49 and C54 TiSi2 have been identified [1,41. The two techniques are used to follow the Ti-Si reaction from initial Ti deposition through C54 TiSi 2 formation. UHV cleaning, deposition, and annealing were employed to form the silicides which were used to characterize the interaction process. Samples were also prepared by Rapid Thermal Annealing (RTA) and furnace annealing techniques to examine the effects of particular annealing processes on silicide formation. The results are described in terms of Ti-Si composition, crystal structures, and formation temperatures.
Mat. Res. Soc. Symp. Proc. V
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