608-Jernigan-apl-199 - APPLIED PHYSICS LETTERS VOLUME 74 NUMBER 10 8 MARCH 1999 Interfacial differences between SiO2 grown on 6H-SiC and on Si100 G

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Interfacial differences between SiO 2 grown on 6H-SiC and on Si 100 G. G. Jernigan a) and R. E. Stahlbush Naval Research Laboratory, Code 6810, Washington DC 20375 M. K. Das and J. A. Cooper, Jr. Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 L. A. Lipkin CREE Research, Inc., Durham, North Carolina 27713 ~ Received 30 October 1998; accepted for publication 12 January 1999 ! Oxides grown on p -type 6H-SiC and on Si ~ 100 ! were studied using x-ray photoelectron spectroscopy and sputter depth profiling to determine what differences exist between the two systems. The oxide on SiC is found to be stoichiometric SiO 2 , but the oxide is structurally different from the oxide grown on Si ~ 100 ! . We propose that strain introduced during processing accounts for the structural differences. We also found that Si atoms at the SiO 2 /SiC interface are chemically different from Si atoms in the bulk of SiC and a number of possible explanations for this are given. © 1999 American Institute of Physics. @ S0003-6951 ~ 99 ! 03510-X # The development of metal-oxide-semiconductor ~ MOS ! structures on silicon carbide substrates is already under way for applications where devices are needed in high tempera- ture or in high power circuits. However, the electrical prop- erties of the oxides grown on SiC do not have the low fixed charge densities ( Q f ) and interfacial trapped charge densities ( D it ) that are obtained for oxides grown on silicon substrates. 1,2 This is surprising since the oxidation of SiC is expected to result in SiO 2 and volatile carbon monoxide or carbon dioxide gas which should escape. In contrast to Si processing, oxides on SiC are grown in a wet ambient, 3,4 utilize a postoxidation anneal, 5,6 and are not improved by hydrogen annealing. 1 Thus, we would like to know what differences exist between the oxides grown on SiC and on Si and how these differences affect the oxide/semiconductor in- terface. In this letter we used x-ray photoelectron spectroscopy ~ XPS ! to study two oxides; one grown on a Si terminated p -type 6H-SiC and one grown on Si ~ 100 ! for comparison. XPS is uniquely capable to determine the compositional and chemical nature of the grown oxides by measuring the inten- sity and energy of the photoelectrons emitted from atoms in the surface. Sputter depth profiling is done to observe how the composition and chemical nature of the atoms change from the oxide to the oxide/substrate interface and into the substrate bulk. We determined the composition of the oxide grown on SiC to be stoichiometric SiO 2 , and we did not detect excess carbon in the oxide nor at the interface. We did observe that the resultant oxide has a different chemical en- vironment than the oxide grown on Si. We also discovered that Si atoms in SiC near the interface are different from Si atoms in the bulk of SiC. The Si terminated 6H-SiC sample was prepared for oxi-
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608-Jernigan-apl-199 - APPLIED PHYSICS LETTERS VOLUME 74 NUMBER 10 8 MARCH 1999 Interfacial differences between SiO2 grown on 6H-SiC and on Si100 G

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