1997 Fiscal Year Final Research Report Summary
Determination of Energy Distribution of Defect State Density for Ultrathin SiO_2/Si Interfaces by Using Photoelectron Yield Spectroscopy
| Project/Area Number |
08455147
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
MIYAZAKI Seiichi Hiroshima University, Department of Electrical Engineering, Associate Professor, 工学部, 助教授 (70190759)
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| Co-Investigator(Kenkyū-buntansha) |
HIROSE Masataka Hiroshima University, Department of Electrical Engineering, Professor, 工学部, 教授 (10034406)
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| Project Period (FY) |
1996 – 1997
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| Keywords | Ultrathin SiO_2 / c-Si Interface / Photoelectron Yield Spectroscopy / Sur11face Fermi Level / Surface States Density / Valence Band State Density / Photoelectron Escape Depth / Interface State Density / Hydrogen Terminated Si Surface |
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| Research Abstract |
A system for total photoelectron yield spectroscopy (PYS) with a high sensitivity has been developed to determine the energy distribution of gap state densities for H-terminated c-Si surfaces and thermally-grown SiO_2/c-Si interfaces. The PYS system was installed in an UHV chamber for X-ray/ultraviolet excited photoelectron spectroscopy together with a Kelvin probe, which enables us to determine Fermi energy on a sample surface with an accuracy of a few meV.
1. In the PYS system, a dynamic range of eight orders of magnitude was obtained for c-Si and SiO_2/c-Si samples.
2. The threshold energies for direct and indirect photoexitations are determined by liner and cubic root plots of PYS spectra for the samples. This leads us to determine the energy position of the valence band edge on the surface independent of the amount of surface band bending.
3. On the basis of the density of states near the valence band edge obtained from the XPS valence band spectrum for c-Si, the gap state density as low as 10^<10>cm^<-2>eV^<-1> can be detected and determined from the first derivative PYS spectrum.
4. The escape depth for 5.6 eV-excited photoelectrons in SiO_2 was estimated to be 3.1nm from the yield reduction rate for the SiO_2/c-Si system.
5. There exist interface states around midgap with densities as high as -10^<12>cm^<-2>eV^<-1> in an as-grown 2.7nm-thick SiO_2/n^+Si interface. 400ﾟC annealing in an H_2 + N_2 gas mixture reduces the interface state density by one order of magnitude for the sample without any gate metal.
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