A parametric study of titanium silicide formation by rapid thermal processing
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A parametric study of titanium silicide formation by rapid thermal processing A. V. Amorsolo, Jr. and P. D. Funkenbusch Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627
A. M. Kadin Department of Electrical Engineering, University of Rochester, Rochester, New York 14627 (Received 12 June 1995; accepted 25 August 1995)
A parametric study of titanium silicide formation by rapid thermal processing was conducted to determine the effects of annealing temperature (650 ±C, 750 ±C), annealing time (30 s, 60 s), wet etching (no HF dip, with HF dip), sputter etching (no sputter etch, with sputter etch), and annealing ambient (Ar, N2 ) on the completeness of conversion of 60 nm Ti on (111)-Si to C54–TiSi2 based on sheet resistance and the uniformity of the sheet resistance measurements across the entire wafer. Statistical analysis of the results showed that temperature, annealing ambient, and sputter etching had the greatest influence. Increasing the temperature and using argon gas instead of nitrogen promoted conversion of the film to C54–TiSi2 . On the other hand, sputter etching retarded it. The results also indicated significant interactions among these factors. The best uniformity in sheet resistance was obtained by annealing at 750 ±C without sputter etching. The different sheet resistance profiles showed gradients that were consistent with expected profile behaviors, arising from temperature variations across the wafer due to the effect of a flowing cold gas and the effects of the wafer edge and flats.
I. INTRODUCTION
Silicides are a new generation of low-resistivity materials for microelectronic applications. Many silicides have the potential of reducing the sheet resistance in heavily doped layers, as well as lowering the contact resistance in microelectronic devices.1 In view of this, many metal silicides have been utilized as ohmic contacts, Schottky barriers, gate electrodes, and local interconnects in microelectronic devices in recent years.1–5 They have also been used as a diffusion barrier to prevent aluminum spiking of shallow junctions, while providing low contact resistance.2 Among the various silicides that can be utilized for microelectronic applications, TiSi2 is considered vital because of its many useful properties. For instance, it can be readily formed by reacting a thin film of Ti with Si during an annealing treatment (not the case with other refractory metal silicides).6 TiSi2 is also known to have good thermal stability6,7 as well as good adhesion.8 During formation of this silicide in VLSI/ULSI circuits, it is easy to selectively etch any unreacted titanium metal without affecting the TiSi2 layer.8 Finally, in terms of resistivity, TiSi2 has the lowest in the refractory metal group (13–16 mV-cm for C54–TiSi2 ).6,9–12 This is comparable to the resistivity of a near noble metal silicide like NiSi (12–15 mV-cm). 412
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J. Mater. Res., Vol. 11, No. 2, Feb 1996
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