Abstract
Thermal passivation of Si1-x Gex using high pressure (10,000 psi) oxidation was studied. Alloys of Si1-xGex (with x=5.4, 11.6, and 17 at. %) approximately 200 nm thick were oxidized using two processes: (i) dry oxygen at 10,000 psi at a temperature of 550°C and (ii) conventional, 1 atm steam at 800°C. The wet oxidation conditions were chosen to produce an oxide thickness comparable (=100 nm for xGe=11.6 at. %) to that obtained during high pressure oxidation at 550°C. Auger sputter depth profiling (AES), X-ray photoelectron spectroscopy (XPS), and cross-sectional transmission electron microscopy (TEM) were used to characterize the as-grown oxides. XPS studies reveal that high pressure oxides formed from all three of the alloys of Si1-xGex have greatly enhanced incorporation of Ge compared to those grown to a similar thickness under wet atmospheric conditions. We report that a significant benefit of this increase in Ge incorporation is the minimization of Ge enrichment near the oxide/Si1-xGex interface. Cross-sectional TEM images reveal a 30 nm thick Ge-rich band at the wet oxide/alloy interface and a dramatically thinner band (<5 nm) present at the oxide/alloy interface produced by high pressure oxidation. For the atmospheric oxidation samples, interfacial misfit dislocations were observed at the alloy/substrate interface indicating that the film relaxed during oxidation. In contrast, the high pressure samples showed no interfacial defects after oxidation.
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Acknowledgement
The authors are grateful to D.W. Greve and M. Racanelli of Carnegie Mellon University for providing the Sil-xGex alloys for this work. This work was partially supported by the Rhode Island Center for Thin Films and Interface Research and one of us (C.C.) acknowledges a graduate fellowship from Brown University. Useful discussion were had with A.F. Schwartzman of Brown University, F. LeGoues of International Business Machines, and R. L. Moore of Perkin-Elmer Corp.
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Caragianis, C., Paine, D.C., Roberts, C.B. et al. High Pressure Oxidation of Strained Si1-xGe Alloys. MRS Online Proceedings Library 204, 357–362 (1990). https://doi.org/10.1557/PROC-204-357
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DOI: https://doi.org/10.1557/PROC-204-357