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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:47.47(Physics, Applied)

Journal Articles

Interface engineering of Ge MOS devices with Zr0$$_{2}$$ 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.

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

SR-XPS analysis of SiO$$_{2}$$/SiC interfaces formed by thermal oxidation of plasma nitrided SiC surfaces

Kagei, Yusuke*; Kosono, Kohei*; Kutsuki, Katsuhiro*; Yoshigoe, Akitaka; Teraoka, Yuden; Hosoi, Takuji*; Shimura, Takayoshi*; Watanabe, Heiji*

no journal, , 

Impact of high-density plasma nitridation of 4H-SiC(0001) surface on thermally grown SiO$$_{2}$$/SiC interface structure was investigated using synchrotron radiation X-ray photoemission spectroscopy. Surface nitridation was confirmed from Si2p and N1s spectra. Both Si sub-oxide and Si sub-nitride states at SiO$$_{2}$$/SiC interface was evaluated through deconvolution of Si2p spectra. We found that the amount of Si sub-oxide states increased with the oxidation time. However, the formation of Si sub-oxides was effectively suppressed by the surface nitridation treatment prior to oxidation. Since an interface state density of Al/SiO$$_{2}$$/SiC MOS capacitor was approximately halved by the surface nitridation treatment, a generation of interface defects was considered to be caused by the Si sub-oxides formation.

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

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

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, , 

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