Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 20
  • 1

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Impact of post-nitridation annealing in CO$$_{2}$$ ambient on threshold voltage stability in 4H-SiC metal-oxide-semiconductor field-effect transistors

Hosoi, Takuji*; Osako, Momoe*; Moges, K.*; Ito, Koji*; Kimoto, Tsunenobu*; Sometani, Mitsuru*; Okamoto, Mitsuo*; Yoshigoe, Akitaka; Shimura, Takayoshi*; Watanabe, Heiji*

Applied Physics Express, 15(6), p.061003_1 - 061003_5, 2022/06

 Times Cited Count:1 Percentile:37.1(Physics, Applied)

The combination of NO annealing and subsequent post-nitridation annealing (PNA) in CO$$_{2}$$ ambient for SiO$$_{2}$$/SiC structures has been demonstrated to be effective in obtaining both high channel mobility and superior threshold voltage stability in SiC-based metal-oxide-semiconductor field-effect transistors (MOSFETs). N atoms on the SiO$$_{2}$$ side of the SiO$$_{2}$$/SiC interface incorporated by NO annealing, which are plausible cause of charge trapping sites, could be selectively removed by CO$$_{2}$$-PNA at 1300$$^{circ}$$C without oxidizing the SiC. CO$$_{2}$$-PNA was also effective in compensating oxygen vacancies in SiO$$_{2}$$, resulting high immunity against both positive and negative bias-temperature stresses.

Journal Articles

Comprehensive physical and electrical characterizations of NO nitrided SiO$$_{2}$$/4H-SiC(11$$overline{2}$$0) interfaces

Nakanuma, Takato*; Iwakata, Yu*; Watanabe, Arisa*; Hosoi, Takuji*; Kobayashi, Takuma*; Sometani, Mitsuru*; Okamoto, Mitsuo*; Yoshigoe, Akitaka; Shimura, Takayoshi*; Watanabe, Heiji*

Japanese Journal of Applied Physics, 61(SC), p.SC1065_1 - SC1065_8, 2022/05

 Times Cited Count:6 Percentile:79.58(Physics, Applied)

Nitridation of SiO$$_{2}$$/4H-SiC(11$$overline{2}$$0) interfaces with post-oxidation annealing in an NO ambient (NO-POA) and its impact on the electrical properties were investigated. Sub-nm-resolution nitrogen depth profiling at the interfaces was conducted by using a scanning X-ray photoelectron spectroscopy microprobe. The results showed that nitrogen atoms were incorporated just at the interface and that interface nitridation proceeded much faster than at SiO$$_{2}$$/SiC(0001) interfaces, resulting in a 2.3 times higher nitrogen concentration. Electrical characterizations of metal-oxide-semiconductor capacitors were conducted through capacitance-voltage ($$C-V$$) measurements in the dark and under illumination with ultraviolet light to evaluate the electrical defects near the conduction and valence band edges and those causing hysteresis and shifting of the $$C-V$$ curves. While all of these defects were passivated with the progress of the interface nitridation, excessive nitridation resulted in degradation of the MOS capacitors. The optimal conditions for NO-POA are discussed on the basis of these experimental findings.

Journal Articles

Impact of nitridation on the reliability of 4H-SiC(11$$bar{2}$$0) MOS devices

Nakanuma, Takato*; Kobayashi, Takuma*; Hosoi, Takuji*; Sometani, Mitsuru*; Okamoto, Mitsuo*; Yoshigoe, Akitaka; Shimura, Takayoshi*; Watanabe, Heiji*

Applied Physics Express, 15(4), p.041002_1 - 041002_4, 2022/04

 Times Cited Count:2 Percentile:51.2(Physics, Applied)

The leakage current and flat-band voltage (VFB) instability of NO-nitrided SiC (11$$bar{2}$$0) (a-face) MOS devices were systematically investigated. Although NO nitridation is effective in improving the interface properties, we found that it reduces the onset field of Fowler-Nordheim (F-N) current by about 1 MVcm$$^{-1}$$, leading to pronounced leakage current. Synchrotron X-ray photoelectron spectroscopy revealed that the nitridation reduces the conduction band offset at the SiO$$_{2}$$/SiC interface, corroborating the above finding. Furthermore, systematical positive and negative bias stress tests clearly indicated the VFB instability of nitrided a-face MOS devices against electron and hole injection.

Journal Articles

Synchrotron radiation photoemission study of Ge$$_{3}$$N$$_{4}$$/Ge structures formed by plasma nitridation

Hosoi, Takuji*; Kutsuki, Katsuhiro*; Okamoto, Gaku*; Yoshigoe, Akitaka; Teraoka, Yuden; Shimura, Takayoshi*; Watanabe, Heiji*

Japanese Journal of Applied Physics, 50(10), p.10PE03_1 - 10PE03_5, 2011/10

 Times Cited Count:11 Percentile:44.1(Physics, Applied)

Journal Articles

Interface engineering of Ge MOS devices with ZrO$$_{2}$$ gate dielectrics

Hosoi, Takuji*; Okamoto, Gaku*; Kutsuki, Katsuhiro*; Kagei, Yusuke*; Harries, J.; Yoshigoe, Akitaka; Teraoka, Yuden; Shimura, Takayoshi*; Watanabe, Heiji*

Oyo Butsuri Gakkai Hakumaku, Hyomen Butsuri Bunkakai, Shirikon Tekunoroji Bunkakai Kyosai Tokubetsu Kenkyukai Kenkyu Hokoku, p.145 - 148, 2010/01

We developed high quality high-$$k$$/Ge gate stacks with reduced leakage current and superior interface quality, which was fabricated by direct deposition of ZrO$$_{2}$$ on Ge substrate and thermal oxidation. Synchrotron radiation photoelectron spectroscopy revealed that thermal oxidation at 823 K caused not only an intermixing between ZrO$$_{2}$$ and Ge but also the formation of GeO$$_{2}$$ at the interlayer. We obtained an equivalent oxide thickness (EOT) of 1.9 nm, and an interface state density of 10$$^{11}$$ cm$$^{-2}$$eV$$^{-1}$$ for Au/ZrO$$_{2}$$/Ge capacitors. Furthermore, we found that the A1$$_{2}$$0$$_{3}$$ capping on the Zr0$$_{2}$$ 1ayer is effective for decreasing EOT. The interface state density as low as 5.3$$times$$10$$^{10}$$ cm$$^{-2}$$eV$$^{-1}$$ was obtained for the Al$$_{2}$$O$$_{3}$$/ZrO$$_{2}$$/Ge stack with 30 min oxidation. The EOT could be reduced to l.6 nm by 10 min oxidation. The leakage current was two orders of magnitude lower than the conventional poly-Si/SiO$$_{2}$$/Si stack.

JAEA Reports

Microbial activity in the subsurface environment of the Tono area and its relation to geochemical conditions -Study of the abundance and diversity of groundwater microorganisms-

Naganuma, Takeshi*; Iwatsuki, Teruki; Murakami, Yuki; Hama, Katsuhiro; Okamoto, Takuji*; Tanimoto, Daisuke*; Fujita, Yuka*; Watanabe, Fumiko*; Adachi, Nahomi*; Sato, Makoto*

JNC TY7400 2003-001, 116 Pages, 2003/05

JNC-TY7400-2003-001.pdf:4.97MB

The abundance and diversity of groundwater microorganisms was studied in the Tono area, central Japan. Total cell counts were estimated by epifluorescence microscopy. Cell viability, based on cell membrane integrity, respiration-based metabolism, and esterase activity was estimated to be from 0.001% to approximately 100% of the total counts. The distribution of microbial abundance wad related to a variety of environmental factors, including fracture numbers, hydrological, and geochemical conditions in the groundwater. In the groundwater, profiles of redox sensitive solutes such as sulphate and sulphide ions, abundance and viability of microbes, and sulphur isotope rations of sulphate ions suggest that microbial sulphate redution involving organic matter and subsequent pyrite precipiration are dominant redox reactions at the depths of the uranium ore body. Concentrations of both the sulphate and chloride increase with increasing depth. The dissoloved sulphate is surmised to have originated from dissolution of sulphate and sulphide minerals in a geologic marine formation precipitated in marine environments, in the upper part of the sedimentary rocks. Such a redox process in the water-mineral-microbe system is inferred to have continued from the time when the marine formation underwent uplift above sea-level, because sulphate-reducing bacteria can use sulphate ions dissolved in fresh water that infiltrates from the marine formation and organic matter located in the deeper sedimentary rocks. Calculations by using the sulphate-S contents of the rocks and the sulphate dissolution rate suggest that microbial sulphate redution alone could maintain sufficiently reducing conditions of preserve the uranium ore for several hundred thousand years, in the case where a hydrogeological system continues to exist without much change. On the other hand, iron-oxidizing/reducing bacteria seem to play an important role in iron redox cycling in the granite groundwater.

Journal Articles

Production of a radioactive endovascular stents by implantation of $$^{133}$$Xe ions

Watanabe, Satoshi; Osa, Akihiko; Sekine, Toshiaki; Ishioka, Noriko; Koizumi, Mitsuo; Kojima, Takuji; Hasegawa, A.*; Yoshii, M.*; Okamoto, E.*; Aoyagi, K.*; et al.

Applied Radiation and Isotopes, 51(2), p.197 - 202, 1999/08

 Times Cited Count:7 Percentile:49.75(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

Development of alanine dose-reader

Haruyama, Yasuyuki; Kojima, Takuji; Tachibana, Hiroyuki; Agematsu, Takashi; Okamoto, Jiro; *

Radioisotopes, 42(8), p.445 - 451, 1993/08

no abstracts in English

Journal Articles

Development of portable ESR spectrometer as a reader for alanine dosimeters

Kojima, Takuji; Haruyama, Yasuyuki; Tachibana, Hiroyuki; Tanaka, Ryuichi; Okamoto, Jiro; *; *

Applied Radiation and Isotopes, 44(1-2), p.361 - 365, 1993/00

 Times Cited Count:5 Percentile:50.63(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

Recent progress in JAERI alanine/ESR dosimeter system

Kojima, Takuji; Tachibana, Hiroyuki; Haruyama, Yasuyuki; Tanaka, Ryuichi; Okamoto, Jiro

Radiation Physics and Chemistry, 42(4-6), p.813 - 816, 1993/00

 Times Cited Count:8 Percentile:63.72(Chemistry, Physical)

no abstracts in English

Journal Articles

Alanine/ESR dosimetry system for routine use in radiation processing

Kojima, Takuji; Haruyama, Yasuyuki; Tachibana, Hiroyuki; Tanaka, Ryuichi; Okamoto, Jiro; *; *; *; Kashiwazaki, Shigeru*

Radiation Physics and Chemistry, 42(4-6), p.757 - 760, 1993/00

 Times Cited Count:7 Percentile:60.47(Chemistry, Physical)

no abstracts in English

Oral presentation

In-situ characterization of chemical bonding states and thermal decomposition of Ge$$_{3}$$N$$_{4}$$ film by SR-XPS

Hosoi, Takuji*; Kutsuki, Katsuhiro*; Okamoto, Gaku*; Harada, Makoto*; Yoshigoe, Akitaka; Teraoka, Yuden; Shimura, Takayoshi*; Watanabe, Heiji*

no journal, , 

After wet cleaning of p-Ge(001) by HF solution, the surface was anealed in an ultra-high vacuum and was nitrided using a large area nitrogen plasma apparatus in the conditions of surface temperature: 623 K, RF power: 50 W, nitrogen pressure:10.5 Torr, and reaction period: 30 min. The chemical bonding states and thermal decomposition processes of the nitide film was in-situ analyzed by synchrotron radiation photoemission spectroscopy. XPS spectra of clean Ge surface showed binding energies of Ge3d5/2 and 3/2 levels were 29.2 eV and 29.8 eV, respectively. The Ge surface nitrided by the high density plasma was oxidized by exposure to the air so that both components of nitride and oxide were observed by the SR-XPS before thermal anealing. GeO$$_{2}$$ component was selectively removed by thermal anealing up to 773 K in the UHV condition. After that XPS spectra of pure Ge$$_{3}$$N$$_{4}$$ film could be observed. We concluded chemical shift of the nitrided Ge was 2.2 eV.

Oral presentation

Fabrication and characterization of high quality Al$$_{2}$$O$$_{3}$$/ZrO$$_{2}$$/GeO$$_{2}$$ layered gate dielectrics

Okamoto, Gaku*; Kutsuki, Katsuhiro*; Kagei, Yusuke*; Harries, J.; Yoshigoe, Akitaka; Teraoka, Yuden; Hosoi, Takuji*; Shimura, Takayoshi*; Watanabe, Heiji*

no journal, , 

Structure analyses and electrical characteristic tests have been conducted for a high-k/Ge stuck of Al$$_{2}$$O$$_{3}$$/ZrO$$_{2}$$/GeO$$_{2}$$/Ge structure. A ZrGeO layer and intermediate oxidation number states for Ge have been confirmed in photoemission spectra in addition to a chemically-shifted Ge$$^{4+}$$ component suggesting the growth of GeO$$_{2}$$ interface layer. An Au electrode was capped on this dielectic substrate to make an Au/Al$$_{2}$$O$$_{3}$$/ZrO$$_{2}$$/GeO$$_{2}$$/Ge capacitor. C-V measurements were conducted for the capacitor. Hysteresis was so small of 21 mV and frequency dispersion was also small. Interface state density near a mid gap, estimated by a low temperature conductance method, was 5.3$$times$$10$$^{10}$$ cm$$^{-2}$$eV$$^{-1}$$. As a conclusion, we succeeded to make a high-k/Ge stuck which has excellent interface characteristics.

Oral presentation

SR-XPS analysis of SiO$$_{2}$$/SiC interfaces formed by thermal oxidation of 4H-SiC(000$$bar{1}$$) surfaces

Kirino, Takashi*; Kagei, Yusuke*; Okamoto, Gaku*; Harries, J.; Yoshigoe, Akitaka; Teraoka, Yuden; Mitani, Shuhei*; Nakano, Yuki*; Nakamura, Takashi*; Hosoi, Takuji*; et al.

no journal, , 

In order to study the origin of degradation for interface chracteristics and reliability of SiC(0001)C surfaces, chemical bonding states at SiO$$_{2}$$/SiC interfaces made on (000$$bar{1}$$)$$_{Si}$$ and (000$$bar{1}$$)$$_{C}$$ surfaces have been analyzed by using a synchrotron radiation XPS method. Si2p$$_{3/2}$$ components were extracted from Si2p photoemission peaks. Sub-oxidea components were observed in addition to the SiC substrate and the oxide layer. In the interface of the oxide layer formed on the (000$$bar{1}$$)$$_{C}$$ surface, Si$$^{1+}$$ component was small, higher oxidation number components were larger, and total amount od sub-oxides was larger comparing to that of the (000$$bar{1}$$)$$_{Si}$$ surface. A binding energy for oxide formed on the (000$$bar{1}$$)$$_{C}$$ surface was shifted to 0.22 eV higher side comparing to that of the (000$$bar{1}$$)$$_{Si}$$ surface. It indicates that band off-set of conduction band is small in the SiO$$_{2}$$/SiC interface.

Oral presentation

SR-XPS study on energy band structure of thermally grown SiO$$_{2}$$/4H-SiC interface

Kirino, Takashi*; Kagei, Yusuke*; Okamoto, Gaku*; Harries, J.; Yoshigoe, Akitaka; Teraoka, Yuden; Mitani, Shuhei*; Nakano, Yuki*; Nakamura, Takashi*; Hosoi, Takuji*; et al.

no journal, , 

Device ability of SiC-MOSFET's expected from physical data has not been achieved because channel resistance increases by mobility degradation due to Si0$$_{2}$$/SiC interface defects. Although high channel mobility is obtained in the MOSFET's made on a 4H-SiC(000-1)c face compared to them on a 4H-SiC(0001)Si face, reliability of an oxide film is preferential in the MOSFET's on a 4H-SiC(000-1)c face. Conduction band off-set of SiO$$_{2}$$/SiC interface and energy distribution of the interface level density are known to be different between MOSFET's on a 4H-SiC(000-1)c face and a 4H-SiC(0001)Si face. Physical origins for them are not known yet. In order to make clear the reasons for degradation of interface characteristics and reliability in the MOSFET's made on an SiC(000-1)c face, we evaluated chemical bonding states and energy band structures of SiO$$_{2}$$/SiC interfaces formed on an SiC(0001)Si face and an SiC(000-1)c face using synchrotron radiation photoemission spectroscopy.

Oral presentation

Impact of Ge$$_{3}$$N$$_{4}$$ interface layer on EOT scaling in high-k/Ge gate stacks

Kutsuki, Katsuhiro*; Okamoto, Gaku*; Hideshima, Iori*; Uenishi, Yusuke*; Kirino, Takashi*; Harries, J.; Yoshigoe, Akitaka; Teraoka, Yuden; Hosoi, Takuji*; Shimura, Takayoshi*; et al.

no journal, , 

Direct deposition of ZrO$$_{2}$$ films on Ge substrates and subsequent thermal oxidation results in an equivalent oxide thickness (EOT) of above 2 nm while obtaining good interface quality due to interfacial GeO$$_{2}$$ formation. In this work, we proposed the use of Ge$$_{3}$$N$$_{4}$$ interlayer formed by high-density plasma nitridation for further EOT scaling because of its high resistance to oxidation and superior thermal stability. The structural modification of ZrO$$_{2}$$/Ge$$_{3}$$N$$_{4}$$/Ge after oxidation was characterized by synchrotron-radiation X-ray photoelectron spectroscopy at BL23SU in SPring-8. Ge 3d core-level spectra revealed that the Ge$$_{3}$$N$$_{4}$$ interlayer was slightly oxidized after thermal oxidation at 823 K, but N 1s spectra remained almost unchanged. This indicates that the Ge$$_{3}$$N$$_{4}$$ interlayer is effective in suppressing interfacial oxidation, thus obtaining an EOT of 1.8 nm.

Oral presentation

Determination of SiO$$_{2}$$/4H-SiC conduction band offset by SR-XPS

Kirino, Takashi*; Kagei, Yusuke*; Okamoto, Gaku*; Harries, J.; Yoshigoe, Akitaka; Teraoka, Yuden; Mitani, Shuhei*; Nakano, Yuki*; Nakamura, Takashi*; Hosoi, Takuji*; et al.

no journal, , 

It has been reported that hydrogen incorporation into thermally grown SiO$$_{2}$$/4H-SiC structures not only improves the interface quality, but also degrades the gate oxide reliability depending on SiC surface orientation. In this study, energy band diagrams of thermally grown SiO$$_{2}$$/4H-SiC(0001) and SiO$$_{2}$$/4H-SiC(000-1) structures with and without high-temperature hydrogen annealing were evaluated by synchrotron radiation X-ray photoelectron spectroscopy. The SiO$$_{2}$$ band gap and valence band offset at SiO$$_{2}$$/SiC interface were extracted from O 1s energy loss spectra and valence band spectra, respectively. The obtained energy band diagrams revealed that conduction band offsets at SiO$$_{2}$$/SiC interfaces were decreased after the hydrogen annealing especially for 4H-SiC(000-1) substrates. This is one possible reason for the reliability degradation of 4H-SiC metal-oxide-semiconductor devices by hydrogen incorporation.

Oral presentation

Interface engineering of ZrO$$_{2}$$/Ge gate stacks by post-deposition annealing and Al$$_{2}$$O$$_{3}$$ capping layers

Watanabe, Heiji*; Okamoto, Gaku*; Kutsuki, Katsuhiro*; Harries, J.; Yoshigoe, Akitaka; Teraoka, Yuden; Hosoi, Takuji*; Shimura, Takayoshi*

no journal, , 

We fabricated high-quality high-k/Ge gate stacks by direct deposition of ZrO$$_{2}$$ layers on Ge substrates and subsequent post-deposition annealing. Synchrotron-radiation X-ray photoelectron spectroscopy revealed that thermally oxidizing a ZrO$$_{2}$$/Ge structure at 823 K caused not only ZrO$$_{2}$$ and Ge to intermix but also a pure GeO$$_{2}$$ interlayer to form. By optimizing subsequent oxidation conditions, we obtained a minimum EOT of 1.9 nm, negligible C-V hysteresis, and an interface state density (Dit) of a few 10$$^{11}$$ cm$$^{-2}$$eV$$^{-1}$$ for Au/ZrO$$_{2}$$/Ge capacitors. We also developed Al$$_{2}$$O$$_{3}$$/ZrO$$_{2}$$ stacked gate dielectrics to control interface reaction during the post treatment. The Al$$_{2}$$O$$_{3}$$ capping on the ZrO$$_{2}$$ layer was found to be beneficial for further EOT scaling because it suppressed excess interface reaction. Scaled EOT value down to 1.6 nm and leakage current reduction were achieved.

Oral presentation

In situ synchrotron radiation photoemission study of Ge$$_{3}$$N$$_{4}$$/Ge structures formed by plasma nitridation

Hosoi, Takuji*; Kutsuki, Katsuhiro*; Okamoto, Gaku*; Yoshigoe, Akitaka; Teraoka, Yuden; Shimura, Takayoshi*; Watanabe, Heiji*

no journal, , 

Oral presentation

Reliability issues in Nitrided SiC MOS devices

Kobayashi, Takuma*; Nakanuma, Takato*; Suzuki, Asato*; Sometani, Mitsuru*; Okamoto, Mitsuo*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; Watanabe, Heiji*

no journal, , 

We investigated the reliability of nitrided SiC MOS devices in terms of oxide leakage and flatband voltage stability. Although nitrided MOS devices on non-basal planes are known to have superior on-state performances, we found that the nitridation not only leads to pronounced oxide leakage but also hampers the flatband voltage stability in response to electron and hole injection. In the presentation, we will show how the nitridation modifies the MOS interfaces based on the results of synchrotron radiation X-ray photoelectron spectroscopy and discuss the possible cause of reliability degradation.

20 (Records 1-20 displayed on this page)
  • 1