Faculty Profiles - NAKATSUKA, Osamu

Papers - NAKATSUKA, Osamu

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Ge基板上に作製したPr酸化膜の評価 Reviewed

坂下満男, 鬼頭伸幸, 加藤亮祐, 近藤博基, 中塚理, 酒井朗, 小川正毅, 財満鎭明

特別研究会研究報告“ゲートスタック研究会 -材料・プロセス・評価の物理-”（第13回研究会） page： 237-242 2008.2

Contact properties of epitaxial NiSi2/heavily doped Si structures formed from Ni/Ti/Si systems Reviewed

S. Akimoto, O. Nakatsuka, A. Suzuki, A. Sakai, M. Ogawa, S. Zaima

Advanced Metallization Conference (AMC) page： 101-105 2008

Interface and defect control for group IV channel engineering

A. Sakai, Y. Ohara, T. Ueda, E. Toyoda, K. Izunome, S. Takeuchi, Y. Shimura, O. Nakatsuka, M. Ogawa, S. Zaima, S. Kimura

ECS Transactions Vol. 16 ( 10 ) page： 687-698 2008

パルスレーザー蒸着法によるGe基板上へのPr酸化膜の作製とその構造及び電気的特性評価

鬼頭伸幸, 坂下満男, 酒井朗, 中塚理, 近藤博基, 小川正毅, 財満鎭明

特別研究会研究報告“ゲートスタック研究会 –材料・プロセス・評価の物理-”（第12回研究会） page： 251-256 2007.2

Strain relaxation of patterned Ge and SiGe layers on Si(001) substrates

S. Mochizuki, A. Sakai, O. Nakatsuka, H. Kondo, K. Yukawa, K. Izunome, T. Senda, E. Toyoda, M. Ogawa, and S. Zaima

Semicond. Sci. Tech. Vol. 22 ( 1 ) page： S132-S136 2007.1

Language：English Publishing type：Research paper (scientific journal)

We have investigated dislocation morphology and strain relaxation mechanisms of SiGe and Ge sub-micron wide striped mesa lines patterned on Si(0 0 1) substrates. The patterning of SiGe and Ge layers principally leads to asymmetric elastic strain relaxation. Post-patterning anneal induces 60° dislocation introduction to relax the strain but the narrower the line width the more dominant is the elastic strain relaxation. In the case of 250 nm wide SiGe lines, 60° dislocation introduction along the line is critically suppressed so that asymmetric strain distribution is realized. On the other hand, for the Ge line structure, pre-formed pure edge dislocations elongate along both orthogonal directions at the heterointerface independent of the line geometry even with the line width of 250 nm. Thus strain relaxation occurs symmetrically and rigidly. These results can be explained by deference of the introduction and propagation mechanisms of 60° and pure-edge dislocations.

Ge(001)表面の酸素エッチングおよび初期酸化過程の原子スケール評価

山崎理弘, 若園恭伸, 酒井朗, 中塚理, 竹内正太郎, 小川正毅, 財満鎭明

特別研究会研究報告“ゲートスタック研究会 –材料・プロセス・評価の物理-”（第12回研究会） page： 197-202 2007.1

Growth and structure evaluation of strain-relaxed Ge1-xSnx buffer layers grown on various types of substrates Reviewed

S. Takeuchi, A. Sakai, K. Yamamoto, O. Nakatsuka, M. Ogawa, and S. Zaima

Semicond. Sci. Tech. Vol. 22 ( 1 ) page： S231-S235 2007.1

Language：English Publishing type：Research paper (scientific journal)

We have performed growth and structure evaluation of strain-relaxed Ge1-xSnx buffer layers grown on Si(0 0 1), virtual Ge(0 0 1) and bulk Ge(0 0 1) substrates. In the case of Si(0 0 1), amorphous Ge1-xSnx phases are partially formed as well as many threading dislocations in Ge0.98Sn0.02 layers. Employing virtual Ge substrates to reduce the lattice mismatch at the interface leads to epitaxial Ge0.978Sn0.022 layers with a flat surface. Most of threading dislocations in the Ge0.978Sn0.022 layer comes from pre-existing ones in the virtual Ge substrate and propagates laterally, leaving misfit segments at the Ge0.978Sn0.022/virtual Ge interface, after post-deposition annealing (PDA). This simultaneously results in the reduction of threading dislocation density and the promotion of strain relaxation. In the case of bulk Ge(0 0 1), although low threading dislocation density can be achieved, less than 106 cm-2, the film exhibits surface undulation and a lesser degree of strain relaxation even after PDA.

Silicide and germanide technology for contacts and metal gates in MOSFET applications

S. Zaima, O. Nakatsuka, H. Kondo, M. Sakashita, A. Sakai, M. Ogawa

ECS Transactions Vol. 11 ( 6 ) page： 197-205 2007

Impact of Pt incorporation on thermal stability of NiGe layers on Ge(001) substrates

O. Nakatsuka, A. Suzuki, A. Sakai, M. Ogawa, S. Zaima

Extended Abstracts of the 7th International Workshop on Junction Technology, IWJT 2007 page： 87-88 2007

Electrical properties of epitaxial NiSi2/Si contacts with extremely flat interface formed in Ni/Ti/Si(0 0 1) system Reviewed

O. Nakatsuka, A. Suzuki, A. Sakai, M. Ogawa, and S. Zaima

Microelectron. Eng. Vol. 83 ( 11-12 ) page： 2272-2276 2006.11

Ni-Silicide/Si and SiGe(C) Contact Technology for ULSI Applications Invited

O. Nakastuka, S. Zaima, A. Sakai, and M. Ogawa

Proceedings of the 14th annual IEEE International Conference on Advanced Thermal Processing of Semiconductors page： 31-37 2006.10

Control of misfit dislocations in strain-relaxed SiGe buffer layers on SOI substrates Reviewed

N. Taoka, A. Sakai, S. Mochizuki, O. Nakatsuka, M. Ogawa and S. Zaima

Thin Solid Films Vol. 508 ( 1-2 ) page： 147-151 2006.6

Language：English Publishing type：Research paper (scientific journal)

A thin strain-relaxed SiGe buffer layer with pure-edge dislocations has been grown on a silicon-on-insulator (SOI) substrate by using low-temperature epitaxy of Ge and subsequent high-temperature annealing. The dislocation morphology and crystalline mosaicity of the strain-relaxed SiGe layers has been measured, and the influence of the thickness of the SiGe and SOI layers on these features has been investigated. Behavior of the dislocations introduced from the interface between the SiGe and the buried oxide layers during high-temperature annealing shows a high dependence on the thickness of the SOI layer. This SOI thickness dependence can be explained by considering the effects of the image force exerted on the dislocations. A higher temperature anneal and a thinner SOI layer are both found to reduce the crystalline mosaicity.

*Local strain in SiGe/Si heterostructures analyzed by X-ray microdiffraction Reviewed

S. Mochizuki, A. Sakai, N. Taoka, O. Nakatsuka, S. Takeda, S. Kimura, M. Ogawa, and S. Zaima

Thin Solid Films Vol. 508 ( 1-2 ) page： 128-131 2006.6

Language：English Publishing type：Research paper (scientific journal)

We have investigated, using X-ray microdiffraction, local strain and crystalline texture in SiGe layers fabricated under various growth conditions on Si(001) substrates. Two-dimensional reciprocal space maps and contour maps in a series of the X-ray rocking curves were taken from the SiGe layers with misfit dislocations having either a 60 degrees or pure-edge character. Quantitative analysis for fine structures observed in the diffraction peak revealed that crystal domains with sizes ranging from 50 nm to 200 nm at tilt angles from 0.00 degrees to 0.42 degrees with respect to the Si[001] direction are formed in the layer relaxed with 60 degrees dislocations. Furthermore, nonuniformity of crystalline texture having a size of 2 to 4 μm was also detected. On the other hand, no remarkable domain structures were detected from diffraction profiles when the sample is predominantly strain-relaxed by pure-edge dislocations. In this case, homogeneous strain distribution with reduced mosaicity is realized in the micrometer-sized regions.

Initial Growth Process of TiN Films in Ultrahigh-Vacuum Rapid Thermal Chemical Vapor Deposition Reviewed

Y. Okuda, S. Naito, O. Nakatsuka, H. Kondo, T. Okuhara, A. Sakai, S. Zaima, and Y. Yasuda

Jpn. J. Appl. Phys. Vol. 45 ( 1A ) page： 49-53 2006.1

Language：English Publishing type：Research paper (scientific journal)

We have investigated the crystalline and electrical properties of Ni silicide/Si and SiGeC contacts for ULSI applications. NiSi/Si contacts promises the contact resistivity as low as 10-8 ohm-cm2 for both n+- and p+-Si. Degradation of the sheet resistance of NiSi layers critically depends on the annealing time particularly at temperatures ranging from 650 deg.C to 750 deg.C. The enlargement of the Si-exposed region concomitant with the NiSi agglomeration is a dominant factor responsible for the increase in sheet resistance and the activation energy of this process is estimated to be 2.8±0.4 eV. Incorporation of Ge into Ni/Si systems is effective in raising the transformation temperature from NiSi to NiSi2. Incorporation of C into NiSi/Si system effectively suppresses the NiSi agglomeration. C introduction also causes the pile-up of B atoms at the NiSi/Si interface, which promises the reduction of the contact resistivity.

Dislocation morphology and crystalline mosaicity in strain-relaxed SiGe buffer layers on SOI

A. Sakai, N. Taoka, O. Nakatsuka, M. Ogawa, S. Zaima

IEEJ Transactions on Electronics, Information and Systems Vol. 126 ( 9 ) page： 1083-1087 2006

Ni silicide and germanide technology for contacts and metal gates in MOSFET applications

S. Zaima, O. Nakatsuka, H. Kondo, M. Sakashita, A. Sakai, M. Ogawa

ICSICT-2006: 2006 8th International Conference on Solid-State and Integrated Circuit Technology, Proceedings page： 322-325 2006

Scanning tunneling microscopy study on the reaction of oxygen with clean Ge(001) surfaces

A. Sakai, Y. Wakazono, O. Nakatsuka, S. Zaima, M. Ogawa

ECS Transactions Vol. 2 ( 7 ) page： 1197-1203 2006

Thermal stability and electrical properties of Ni-silicide on C-incorporated Si Reviewed

O. Nakatsuka, K. Okubo, A. Sakai, M. Ogawa, S. Zaima, J. Murota, and Y. Yasuda

Proc. of Advanced Metallization Conference 2004 (AMC2004) page： 293-298 2005.10

*Low Temperature Formation of Epitaxial NiSi2 Layers with Solid-Phase Reaction in Ni/Ti/Si(001) Systems Reviewed

O. Nakatsuka, K. Okubo, Y. Tsuchiya, A. Sakai, S. Zaima, and Y. Yasuda

Jpn. J. Appl. Phys. Vol. 44 ( 5A ) page： 2945-2947 2005

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)

The solid-phase epitaxial growth of NiSi2 in Ni/Ti/Si systems has been investigated. Continuous epitaxial NiSi2 layers consisting of pyramidal domains with {111} facets at the Ni-silicide/Si interface can be formed by annealing at a temperature (350 deg.C) lower than that for conventional Ni/Si systems. This NiSi2 layer is transformed to a uniform epitaxial NiSi2 layer with an atomically flat silicide/Si interface by additional annealing at 850deg.C, while the {111} facets at the NiSi2/Si interface remains in the Ni/Si system under the same annealing conditions. Moreover, the epitaxial NiSi2 layer formed at 350 deg.C exhibits a high thermal robustness even after annealing at higher than 750 deg.C, in contrast to the polycrystalline NiSi layer.

Initial growth behaviors of SiGeC in SiGe and C alternate deposition Reviewed

S. Takeuchi, O. Nakatsuka, Y. Wakazono, A. Sakai, S. Zaima, and Y. Yasuda

Materials Science in Semiconductor Processing Vol. 8 ( 1-3 ) page： 5-9 2005

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