Abstract
We investigated the temporal evolution of nickel-silicide phase-formation and the simultaneous redistribution of platinum during silicidation of a 10 nm thick Ni 0.95Pt 0.05 film on a Si(100) substrate. Grazing incidence x-ray diffraction (GIXRD) and atom-probe tomography (APT) measurements were performed on as-deposited films and after rapid thermal annealing (RTA) at 320 or 420 °C for different times. Observation of the Ni 2Si phase in as-deposited films, both with and without platinum alloying, is attributed to surface preparation. RTA at 320 °C for 5 s results in the formation of the low-resistivity NiSi intermetallic phase and nickel-rich phases, Ni 2Si and Ni 3Si 2, as demonstrated by GIXRD measurements. At 420 °C for 5 s, the NiSi phase grows outward from the silicide/Si(100) interface by consuming the nickel-rich silicide phases. On increasing the annealing time at 420 °C to 30 min, this reaction is driven towards completion. The nickel-silicide/silicon interface is reconstructed in three-dimensions employing APT and its chemical root-mean-square roughness, based on a silicon isoconcentration surface, decreases to 0.6 nm with the formation of the NiSi phase during silicidation. Pt redistribution is affected by the simultaneous reaction between Ni and Si during silicidation, and it influences the resulting microstructure and thermal stability of the NiSi phase. Short-circuit diffusion of Pt via grain boundaries in NiSi is observed, which affects the resultant grain size, morphology, and possibly the preferred orientation of the NiSi grains. Pt segregates at the NiSi/Si(100) heterophase interface and may be responsible for the morphological stabilization of NiSi against agglomeration to temperatures greater than 650 °C. The Gibbsian interfacial excess of Pt at the NiSi/Si(100) interface after RTA at 420 °C for 5 s is 1.2 ± 0.01 atoms nm -2 and then increases to 2.1 ± 0.02 atoms nm -2 after 30 min at 420 °C, corresponding to a decrease in the interfacial free energy of 7.1 mJ m -2.
| Original language | English (US) |
|---|---|
| Article number | 064307 |
| Journal | Journal of Applied Physics |
| Volume | 112 |
| Issue number | 6 |
| DOIs | |
| State | Published - Sep 15 2012 |
Funding
This research was supported by Semiconductor Research Corporation, Task No. 1441.001. P.A. kindly acknowledges additional support from an IBM Ph.D. Fellowship during the academic year 2009-2010, a fellowship from Northwestern University during his terminal year, and partial support from the US-Israel Binational Science Foundation, Grant No. 2008140, during 2009-2010 and 2010-2011. D.N.S. kindly acknowledges support from an IBM Faculty Award for 2010-2011. The atom-probe tomographic measurements were performed at the Northwestern University Center for Atom-Probe Tomography (NUCAPT), which is managed by Dr. Dieter Isheim. The LEAP tomograph was purchased and upgraded with funding from NSF-MRI (DMR-0420532) and ONR-DURIP (N00014-0400798, N00014-0610539, N00014-0910781) grants. We also thank the Initiative for Sustainability and Energy at Northwestern for support of NUCAPT with grants for equipment upgrades. The FEI dual-beam FIB microscope was used in the EPIC facility of the NUANCE Center at Northwestern University. X-ray measurements were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by E. I. DuPont de Nemours & Co., The Dow Chemical Company and Northwestern University. Use of the APS, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract No. DE-AC02-06CH11357. We thank Dr. Denis T. Keane for assistance with the x-ray measurements, Dr. Ivan D. Blum for detailed discussions of diffusion/reaction silicidation models and for reading the manuscript, and an anonymous reviewer for comments on our manuscript.
ASJC Scopus subject areas
- General Physics and Astronomy