Synchrotron radiation photoemission study of GeN/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

https://doi.org/10.1143/JJAP.50.10PE03

Interface engineering of Ge MOS devices with ZrO 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-/Ge gate stacks with reduced leakage current and superior interface quality, which was fabricated by direct deposition of ZrO on Ge substrate and thermal oxidation. Synchrotron radiation photoelectron spectroscopy revealed that thermal oxidation at 823 K caused not only an intermixing between ZrO and Ge but also the formation of GeO at the interlayer. We obtained an equivalent oxide thickness (EOT) of 1.9 nm, and an interface state density of 10 cmeV for Au/ZrO/Ge capacitors. Furthermore, we found that the A10 capping on the Zr0 1ayer is effective for decreasing EOT. The interface state density as low as 5.310 cmeV was obtained for the AlO/ZrO/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/Si stack.

In-situ characterization of chemical bonding states and thermal decomposition of GeN 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 component was selectively removed by thermal anealing up to 773 K in the UHV condition. After that XPS spectra of pure GeN film could be observed. We concluded chemical shift of the nitrided Ge was 2.2 eV.

SR-XPS analysis of SiO/SiC interfaces formed by thermal oxidation of 4H-SiC(000) 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/SiC interfaces made on (000) and (000) surfaces have been analyzed by using a synchrotron radiation XPS method. Si2p 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) surface, Si component was small, higher oxidation number components were larger, and total amount od sub-oxides was larger comparing to that of the (000) surface. A binding energy for oxide formed on the (000) surface was shifted to 0.22 eV higher side comparing to that of the (000) surface. It indicates that band off-set of conduction band is small in the SiO/SiC interface.

Impact of GeN 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 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 formation. In this work, we proposed the use of GeN 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/GeN/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 GeN interlayer was slightly oxidized after thermal oxidation at 823 K, but N 1s spectra remained almost unchanged. This indicates that the GeN interlayer is effective in suppressing interfacial oxidation, thus obtaining an EOT of 1.8 nm.

Interface engineering of ZrO/Ge gate stacks by post-deposition annealing and AlO 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 layers on Ge substrates and subsequent post-deposition annealing. Synchrotron-radiation X-ray photoelectron spectroscopy revealed that thermally oxidizing a ZrO/Ge structure at 823 K caused not only ZrO and Ge to intermix but also a pure GeO 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 cmeV for Au/ZrO/Ge capacitors. We also developed AlO/ZrO stacked gate dielectrics to control interface reaction during the post treatment. The AlO capping on the ZrO 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.

-particle breakup at incident energy of several hundreds of MeV/u

Yamaguchi, Yuji*; Araki, Yusuke*; Fujii, Motoharu*; Watanabe, Gaku*; Sanami, Toshiya*; Matsufuji, Naruhiro*; Koba, Yusuke*; Iwamoto, Yosuke; Uozumi, Yusuke*

no journal, , 

For heavy-ion cancer therapy with carbon, there is a problem about radiation exposure due to secondary particles produced by heavy ion incident reaction. We have a plan to extend our improved intra nuclear cascade (INC) model for proton incidences to INC model for alpha and carbon incidences. However, there is no experimental data about multi-particle (proton, deuteron, triton, He and alpha) production double differential cross sections (DDXs) for alpha incident reactions to validate the extended INC model. In this work, we measured multi-particle production DDXs for 100 and 230 MeV/nucleon alpha incident reactions on samples (C, Al, Co, Nb) at the HIMAC building in National Institute of Radiological Sciences (NIRS), QST. As a result, we found that results calculated by the extended INC model agreed with experimental data at 30 degrees and those underestimated the experimental data with increasing angles.