Time Resolved X-Ray Diffraction Study of the Transformation Kinetics of TiSi2-C49 in Amorphous Si/Ti Multilayers
- PDF / 280,892 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 0 Downloads / 139 Views
TIME RESOLVED X-RAY DIFFRACTION STUDY OF THE TRANSFORMATION KINETICS OF TiSi2-C49 IN AMORPHOUS Si/Ti MULTILAYERS J. Sariel 1 , Haydn Chen2 , J. F. 2 Jongste33 , S. Radelaar 3 1 - Nuclear Research Center Negev, P.O.Box 9001, Beer-Sheva, 84190, Israel. 2 - Dept. of Materials Science & Engineering, University of Illinois at Urbana Champaign, 1304 W. Green St., Urbana, IL, 61801. 3 - Delft University of Technology, DIMES, Delft, The Netherlands. ABSTRACT Amorphous Si/Ti multilayers transform at high temperatures (above 700"C) to TiSi -C54. This phase is important for microelectronics applications because of iis low resistivity, stability up to 900*C, and compatibility with silicon processing. However, an unfavorable metastable TiSi 2 -C49 phase is usually formed at lower temperatures. Thus, an understanding of the C49 phase formation kinetics is useful to the device processing strategy. The kinetics of the transformation of TiSi -C49 phase can be characterized as a process of nucleation and growth, using ?he well known Johnson Mehl Avrami (JMA) equation. In the present work the formation kinetics of the C49 phase has been studied by an in situ x-ray diffraction technique. Isothermal annealing in vacuum was done at four temperatures, in the range of 275"C to 310"C. A position sensitive detector (PSD) was used to simultaneously collect the diffracted beams of (131) and (150) peaks of the C49 phase. From the data, the Avrami exponent, n, was determined to be 2.0±0.1. The reaction rate constant k follows a familiar Arrhenius-type equation with a measured activation energy of 2.5eV. Comparison of our x-ray results with kinetic data obtained by other means will be discussed. INTRODUCTION Titanium dis~licide (TiSi 2 ) is used as a material for metallization and interconnection on silicon based integrated circuits[l]. The favorable phase is TiSi -C54, which is formed above 700°C[2]. This phase has low resistivity, stabiliiy up to 900&C and is compatible with silicon processing. Before this phase appears, a metastable TiSi -C49 phase is already formed at lower temperature during heating. This unfavored C49 phase has a higher resistivity (4-20 times higher than that of C54 phase), and is unstable at higher temperatures. Jongste et al.[3], have measured the film stresses resulted from the formation of the C49 phase, and inferred, indirectly, the rate constants and the activation-energy. In the present work the same type of samples were used to measure directly the growth kinetics of the C49 phase by means of an in situ x-ray diffraction technique. Similar analytical methods to the ones used by Jongste et al.[3] were employed. EXPERIMENTAL Samples o-'stacked Ti and Si layers sputtered on Si(100) wafer were prepared, with ;hickness of about 250 nm, and periodicity of 1 nm. The ratio of Ti to Si is tbout 1:2. X-ray diffraction examinations 4 were done in situ with isothermal annealing in vacuum (approximately 2.10 Pa) at four
temperatures, i.e. 275"C, 290*C, 300C and 310"C. The sample was mounted in a miniature hot stage[4], with a
Data Loading...
