Formation of silicides by ion beam synthesis
EMSL Project ID
6505
Abstract
The compatibility with Si-processing technology has meant the transition metal silicides have been the topic of considerable research interest in recent years. CoSi2 has in particular been the focus of much attention because it has a low resistivity (~15  cm), it is in thermodynamically in equilibrium with Si over a wide temperature range, and its cubic structure has a lattice mismatch to Si of ~1.2 %. This enables epitaxial buried layers of CoSi2 to be formed by high fluence ion irradiation. This special feature is extremely useful for introducing buried metal layers interconnects nanometer devices by direct writing using Focused Ion Beam (FIB)1 and aperture masked microbeams . The formation of CoSi2 has been studied extensively by Ion Beam Synthesis (IBS) where Co ions are implanted into Si , . In particular the formation of silicides surface layers , the approach to sputtering equilibrium , the development of surface topography and the formation of low resistivity layers has been studied. The studies so far have focused on the implantation of Si with Co. In this IBS situation the CoSi2 phase is approached from the Si-rich side of the binary phase diagram. In this proposal we seek to investigate the cobalt silicide phase formation by IBS from both the Co-rich side and Si-rich side of the phase diagram. This will be done by studying the phase formation resulting from high-fluence implantation of Si ions into bulk Co and Co in to bulk Si. The situation is expected to be quite different. This is because of the existence of other phases such as CoSi between Co to CoSi2 whereas no other equilibrium phases exist from Si to CoSi2.
Experimental work
Cobalt or silicon samples have been implanted with high fluences of low-energy Si or metal beams using the Metal Vacuum Vapour Arc (MEVVA) implanter at the Institute for Low Energy Nuclear Physics ant Beijing National University. Samples have already been prepared with different beam currents with fluences (5x1017 and 1x1018 ions cm-2) of Si ions and further samples will be available after January.
To gain an understanding of the characterisation program should cover the following aspects.
- Concentration depth profile measurement using Rutherford Backscattering Spectrometry (RBS) and possibly with Elastic Recoil Detection Analysis (ERDA).
- Determination of the different phases and formation sequence by X-ray Diffraction (XRD)
- Scanning Electron Microscopy to study the surface morphology
- Transmission Electron Microscopy (TEM) to investigate epitaxy and the internal structure of the implanted surface.
Project Details
Project type
Capability Research
Start Date
2004-02-03
End Date
2006-02-06
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Joensson CT, IA Maximov, HJ Whitlow, V Shutthanandan, DE McCready, BW Arey, Y Zhang, and S Thevuthasan. 2005. "Synthesis and Characterization of Cobalt Silicide Films on Silicon." PNNL-SA-44675, Pacific Northwest National Laboratory, Richland, WA.