最近の研究業績 (Recent Publications)

 2022年度 (2022/04/01-)

 2021年度 (2021/04/01-2022/03/31)

 2020年度 (2020/04/01-2021/03/31)

 2019年度 (2019/04/01-2020/03/31)

 2018年度 (2018/04/01-2019/3/31)

 2017年度 (2017/04/01-2018/3/31)

以前の研究業績

主な学術論文

(1) Characteristics of Electrolessly Deposited CoReNiMnP Films with Perpendicular Magnetic Anisotropy, H. Matsuda, O. Takano, and P. J. Grundy, Journal of Magnetism and Magnetic Materials, Vol. 128, 386 (1993).

(2) Effect of Dissolved Oxygen on the Magnetic Properties of Electrolessly Deposited Co-P Films, H. Matsuda, and O. Takano, Journal of Magnetism and Magnetic Materials, Vol. 131, 440 (1994).

(3) Characteristics of Electrolessly Deposited Cobalt Tin Phosphorus Films, H. Matsuda and O. Takano, Journal of Magnetism and Magnetic Materials, Vol. 134, 185 (1994).

(4) Magnetization Mechanism of Electrolessly Deposited NiXP/CoReNiMnP Double Layer Films, H. Matsuda, D. Kim, and O. Takano, Transactions of the Institute of Metal Finishing UK, Vol. 72, 150 (1994).

(5) Magnetic Recording Properties of Electrolessly Deposited NiXP/CoReNiMnP Double Layer Media, H. Matsuda, I. Takasu, D. Kim, O. Takano, and P. J. Grundy, Journal of Magnetism and Magnetic Materials, Vol. 155, 250 (1996).

(6) Improvement of the Sintering Processes in a Sendust Alloy Powder Used as a Magnetic Recording Head Material, I. Takasu, A. Yanagitani, and H. Matsuda, Journal of Magnetism and Magnetic Materials, Vol. 163, 397 (1996).

(7) Hole Diffusion Length and Temperature Dependence of Photovoltages for n-Si Electrodes Modified with LB Layers of Ultrafine Platinum Particles, J. G. Jia, M. Fujitani, S. Yae, and Y. Nakato, Electrochim. Acta, Vol. 42, 431 (1996).

(8) Improvement in Photovoltage and Stability of Porous n-Si Electrodes Coated with Platinum by Regulation of the Thickness of Nanoporous Layers, K. Kawakami, T. Fujii, S. Yae, and Y. Nakato, J. Phys. Chem. B, Vol. 101, 4508 (1997).

(9) 無電解めっき法による半導体複合めっき膜の作製とその光電気化学特性, 岩岸哲也, 八重真治, 松田　均, 表面技術, Vol. 49, 1235 (1998).

(10) Development of Electrolessly Deposited Nano Fe-P Films, H. Matsuda, S. Yae, T. Iwagishi, and H. Matsuo, Trans IMF, Vol. 76, 241 (1998).

(11) 無電解めっきの活性化前処理におけるＳｎおよびＰｄの吸着量とＣｏ−Ｐめっき皮膜の表面形態, 山岸憲史, 曽我倫明, 西羅正芳, 八重真治, 松田　均, 表面技術, Vol. 50, 378 (1999).

(12) ヒドラジンを還元剤とする無電解Niめっき膜の光沢性の向上, 八重真治, 伊藤　潔, 山憲史, 松田　均, 表面技術, Vol. 51, 99 (2000).

(13) 無電解めっきの活性化前処理により絶縁性基板上に形成された触媒核の直接観察, 山岸憲史, 八重真治, 西羅正芳, 松田　均, 表面技術, Vol. 51, 215 (2000).

(14) ヒドラジンを還元剤とする無電解Niめっき膜の光沢性と結晶配向性, 八重真治, 中野久継, 伊藤　潔, 山岸憲史, 松田 均, 表面技術，Vol. 51, 1035 (2000).

(15) Electrochemical Deposition of Fine Pt Particles on n-Si Electrodes for Efficient Photoelectrochemical Solar Cells, Shinji YAE, Masaki KITAGAKI, Taizou HAGIHARA, Yuichi MIYOSHI, Hitoshi MATSUDA, Bruce A. PARKINSON, and Yoshihiro NAKATO, Electrochim. Acta, Vol. 47, 345 (2001).

(16) 無電解めっきの活性化前処理により基板に形成される吸着物の量および形態−センシタイジング液のエージングの影響−, 八重真治, 内野智朗, 関根雄介, 岡本尚樹, 山岸憲史, 松田　均, 表面技術, Vol. 52, 713 (2001).

(17) Formation of porous silicon by metal particle enhanced chemical etching in HF solution and its application for efficient solar cells, S. Yae, Y. Kawamoto, H. Tanaka, N. Fukumuro, and H. Matsuda, Electrochem. Comm., Vol. 5, 632 (2003).

(18) Electrolessly Deposited Co-W-Zn-P Films Having High Coercivity and High Corrosion Resistance, S. Yae, T. Kanki, N. Fukumuro, Y. Yamada, and H. Matsuda, Trans. IMF, Vol. 81, 45 (2003).

(19) 無電解めっきの二液法活性化前処理により非導電性基板上に形成される吸着物, 山岸憲史, 八重真治,岡本尚樹, 福室直樹, 松田　均, 表面技術, Vol. 54, 150 (2003).

(20) TiO₂光触媒を利用したマグネシウム合金上への無電解めっきの光パターニング, 福室直樹，加藤陽平，八重真治，松田　均, 表面技術, 54(12), 1056-1057 (2003).

(21) ヒドラジンを還元剤とする無電解純ニッケルめっきの浴組成の単純化, 八重真治，濱田隆弘，横山敦之，伊藤　潔，福室直樹，松田　均, 表面技術，55(1)，89-90 (2004).

(22) 無電解めっきの活性化前処理に用いられるセンシタイジング液の経時変化, 岡本尚樹, 八重真治, 山岸憲史, 三俣宣明, 渡辺 徹, 福室直樹, 松田　均, 表面技術, 55(4), 281-285 (2004).

(23) 無電解Ni-P/TiO₂複合めっき膜の構造と光電流密度, 福室直樹, 臼井勇樹, 八重真治, 松田 均, 表面技術, 55(5), 355-359 (2004).

(24) 二液法活性化により非導電性基板上に形成される吸着物と無電解Ni-Pめっき初期析出物の微視的形態, 山岸憲史, 岡本尚樹, 鵜川博之, 福室直樹, 八重真治, 松田　均, 表面技術, 55(6), 417-422 (2004).

(25) Reaction Process of Two-Step Catalysation Pre-treatment for Electroless Plating on Non-conductiong Substrates, K. Yamagishi, N. Okamoto, N. Mitsumata, N. Fukumuro, S. Yae, and H. Matsuda, Trans. Inst. Met. Fin., 82(3/4), 114-117 (2004).

(26) Autocatalytic Deposition of Pure Nickel Films Having Bright Surfaces and High Electrical Conductivity, K. Ito, S. Yae, T. Hamada, H. Nakano, N. Fukumuro, and H. Matsuda, Electrochemistry, 73(2), 123-127 (2005).

(27) Electroless Deposition of Pure Nickel Films from a Simple Solution Consisting of Nickel Acetate and Hydrazine, S. Yae, K. Ito, T. Hamada, N. Fukumuro, and H. Matsuda, Plat. Surf. Finish., 92(4), 58-62 (2005)

(28) ヒドラジンを還元剤とする無電解純ニッケルめっき膜の微細構造と電気伝導性, 伊藤　潔，福室直樹，八重真治, 松田　均, エレクトロニクス実装学会誌, 8(3), 233-236 (2005).

(29) Porous silicon formation by HF chemical etching for antireflection of solar cells, Shinji Yae, Hiroyuki Tanaka, Tsutomu Kobayashi, Naoki Fukumuro, and Hitoshi Matsuda, Phys. Stat. Sol. (c), 2(9), 3476-3480 (2005).

(30) Microstructural feature of crystalline-amorphous transition layer in structurally graded Co-P films produced by an electroless plating process, N. Fukumuro, J. Nishiyama, S. Yae, and H. Matsuda, Trans. Inst. Met. Finish., 83(6), 281-285 (2005).

(31) Photocatalytic Initiation and Patterning of Autocatalytic Deposition of Metal Films on Magnesium Alloy Substrates, S. Yae, Y. Kato, N. Fukumuro, K. Tanaka, and H. Matsuda, Photocatalytic and Advanced Oxidation Processes for Treatment of Air, Water, Soil and Surfaces (Proceedings of TiO2-9 and AOTs-10) Edited by D. F. Ollis, H. Al-Ekabi, Redox Technologies, Inc., 155-160 (2005).

(32) ヒドラジンを還元剤とする無電解純ニッケルめっき膜の微細構造と電気伝導性, 伊藤 潔, 福室直樹, 八重真治, 松田 均, エレクトロニクス実装学会誌, 8(3), 233-236 (2005).

(33) Sn-Ag-Cu鉛フリーはんだとの接合性に優れた無電解純Niめっき, 伊藤 潔, 福室直樹, 八重真治, 松田 均, エレクトロニクス実装学会誌, 9(1), 52-56 (2006).

(34) Antireflective Porous Layer Formation on Multicrystalline Silicon by Metal Particle Enhanced HF Etching, Shinji Yae, Tsutomu Kobayashi, Tatsunori Kawagishi, Naoki Fukumuro, and Hitoshi Matsuda, Solar Energy, 80(6), 701-706 (2006).

(35) Structural Change in Porous Si by Photoillumination During Metal Particle Enhanced Etching, S. Yae, T. Kobayashi, T. Kawagishi, N. Fukumuro, and H. Matsuda, Proc. the Intern. Symp. Pits & Pores III: Formation, Properties, and Significance for Advanced Materials, 206 ECS Meeting, Oct. 3-8, Honolulu HI USA, Edited by P. Schmuki, D. J. Lockwood, Y. H. Ogata, M. Seo, and H. S. Isaacs, ECS Proceedings Vol., 2004-19, 141-146 (2006).

(36) Confirmation of hydroxide in electroless cobalt alloy films by GDOES, N. Fukumuro, J. Nishiyama, K. Shigeta, H. Takagami, S. Yae, and H. Matsuda, Transactions of the Institute of Metal Finishing, 85(2), 111-112 (2007).

(37) Solar to chemical conversion using metal nanoparticle modified microcrystalline silicon thin film photoelectrode, Shinji Yae, Tsutomu Kobayashi, Makoto Abe, Noriaki Nasu, Naoki Fukumuro, Shunsuke Ogawa, Norimitsu Yoshida, Shuichi Nonomura, Yoshihiro Nakato, and Hitoshi Matsuda, Solar Energy Materials & Solar Cells, 91(4), 224-229 (2007).

(38) Co-P multilayer film electrodeposited under DC electrolysis, N. Fukumuro, J. Nishiyama, K. Shigeta, Y. Morimoto, H. Takagami, S. Yae, H. Matsuda, Electrochemistry Communications, 9(5), 1185-1188 (2007).

(39) In Situ Measurement of Internal Stress in Electrolessly Deposited Copper Film by Television Holographic Interferometry, Naoki Fukumuro, Motohiro Yamazaki, Kiyoshi Ito, Hajime Ishihara, Satoshi Kakunai, Shinji Yae, and Hitoshi Matsuda, Electrochemical and Solid‑State Letters, 10(6), E14-E15 (2007).

(40) Structure of Porous Si Formed by Metal-Particle (Pt, Pd) Enhanced HF Etching, Shinji Yae, Makoto Abe, Tatsunori Kawagishi, Kentarou Suzuki, Naoki Fukumuro, and Hitoshi Matsuda, Trans. Mater. Res. Soc. Jpn., 32(2), 445-448 (2007).

(41) Nucleation behavior in electroless displacement deposition of metals on silicon from hydrofluoric acid solutions, Shinji Yae, Noriaki Nasu, Kohei Matsumoto, Taizo Hagihara, Naoki Fukumuro, and Hitoshi Matsuda, Electrochimica Acta, 53(1), 35-41 (2007).

(42) Hydrogen production using metal nanoparticle modified silicon thin film photoelectrode, S. Yae, A. Onaka, M. Abe, N. Fukumuro, S. Ogawa, N. Yoshida, S. Nonomura, Y. Nakato, H. Matsuda, Solar Hydrogen and Nanotechnology II, Aug. 27-30, 2007, San Diego, CA USA, Edited by Jinghua Guo, Proc. of SPIE, 6650, #6650-12 (2007).

(43) Palladium Enhanced Etching of n-type Silicon in Hydrofluoric Acid Solution, Shinji Yae, Makoto Abe, Naoki Fukumuro, Hitoshi Matsuda, Electrochemistry, 72(2), 144-146 (2008).

(44) High Catalytic Activity of Palladium for Metal-Enhanced Hydrofluoric Acid Etching of Silicon, S. Yae, M. Tashiro, T. Hirano, M. Abe, N. Fukumuro, and H. Matsuda, ECS Transactions, 16(3), 285-289 (2008).

(45) Metal nanorod production in silicon matrix by electroless process, Shinji Yae, Tatsuya Hirano, Takashi Matsuda, Naoki Fukumuro, Hitoshi Matsuda, Appl. Surf. Sci., 255(8), 4670-4672 (2009).

(46) 平滑アルミナ基板と無電解純Niめっき膜の密着性と内部応力との関係, 伊藤　潔, 福室直樹，八重真治, 松田　均, エレクトロニクス実装学会誌, 12(2), 130-136 (2009).

 

(47) n型シリコン上への貴金属微粒子電析に及ぼす置換反応の影響, 河井めぐみ, 八重真治, 福室直樹, 松田　均, 表面技術, 60(5), 355-356 (2009).

 

(48) High Catalytic Activity of Palladium for Metal-Enhanced HF Etching of Silicon, Shinji Yae, Masayuki Tashiro, Makoto Abe, Naoki Fukumuro, and Hitoshi Matsuda, J. Electrochem. Soc., 157(2), D90-D93 (2010).

              Metal-enhanced HF etching of Si is an electroless method used to produce porous Si. Such etching generally uses not only metal-modified Si but also an oxidizing agent, such as hydrogen peroxide or metal ions. Pd exhibits high activity in enhancing the HF etching of Si without an oxidizing agent even under dissolved-oxygen-free and dark conditions. Electrolessly deposited Pd particles on n-type Si enhance the HF etching of Si but produce no porous layer. Patterned Pd films localize the etching under the boundary of the Pd deposited areas, and thus Pd can produce a microetch pattern on Si with a simple immersion in the HF solution. This etching reaction is explained by electron injection into the conduction band of Si due to the Pd-enhanced anodic oxidization of Si with water and the cathodic hydrogen evolution on Pd with the injected electrons.

 

(49) Adhesive Metal Film Formation on Silicon by Electroless Deposition Using Catalytic Anchors, Shinji Yae, Tatsuya Hirano, Keisuke Sakabe, Naoki Fukumuro, and Hitoshi Matsuda, ECS Trans., 25(27), 215-220 (2010).

              Autocatalytic electroless deposition, which is a conventional method to metalize nonmetallic substrates, requires catalyzation of substrates before deposition. For silicon (Si) substrates, obtaining adhesive metal films with conventional catalyzation pretreatments is difficult. In this study, we develop a new method to produce adhesive metal films on Si substrates by an electroless process that consists of three steps: 1) electroless displacement deposition of metal nanoparticles; 2) Si nanopore formation by metal-particleenhanced hydrofluoric acid etching; and 3) metal filling in nanopores and metal-film formation on the whole Si surface by autocatalytic electroless deposition. The metal nanorods in Si act as catalytic nanoanchors to promote autocatalytic electroless metal deposition and improve the adhesion of metal films on Si substrates.

 

(50) Electrochemical Deposition of Pt Particles from Hexachloroplatinate(IV) Ion and Tetrachloroplatinate(II) Ion Solutions, M. Kawai, N. Fukumuro, S. Yae, and H. Matsuda, ECS Trans., 25(33), 117-123 (2010).

              The behavior of Pt electrodeposition on n-Si is different between H₂PtCl₆ (Pt(IV)) and K₂PtCl₄ (Pt(II)) aqueous solutions. Immersion of bare n-Si wafers in a Pt(II) solution under an opencircuit condition deposits Pt particles on n-Si, but immersion in the Pt(IV) solution deposits no particles. In the Pt(IV) solution, silicon oxide is produced with holes injected into the Si valence band by the reduction reaction of Pt(IV) to Pt(II). The quantity of electrodeposited Pt on the glassy carbon at +0.10 V vs. SCE in the Pt(IV) solution was smaller than that of the Pt(II) case. Cyclic voltammetry shows that the electeroeposition behavior of Pt in the early stage is influenced by the substrates.

 

(51) In Situ Stress Measurement of Electrodeposited Ni Films by Television Holographic Interferometry, N. Fukumuro, T. Do, S. Kakunai, S. Yae, and H. Matsuda, ECS Trans., 25(34), 27-34 (2010)

           In situ stress measurements of electrodeposited Ni films from a sulfate bath during deposition were carried out by television holographic interferometry. The effect of the addition of saccharin sodium on the internal stress in the Ni films was studied. Structure change with film growth was investigated by cross-sectional TEM observation. Quantitative analysis of impurities and hydrogen in films was performed. The stress behaviors of Ni films changed drastically from a tensile direction to a compressive direction with an increase of the concentration of saccharin sodium.

 

(52) Effect of Absorbed Hydrogen on Microstructure of Electrodeposited Cobalt, A. Nakayama, N. Fukumuro, S. Yae, and H. Matsuda, ECS Trans., 25(34), 79-85 (2010)

           The objective of this study is to elucidate the relationship between the total amount of hydrogen absorbed in electrodeposited cobalt films and their microstructure. The electrodeposited cobalt films were produced by such different depositing conditions as a solution pH, bath temperature, and current density. Structure analysis with XRD and TEM and hydrogen analysis with TDS reveal that the cobalt films with higher absorbed hydrogen content have a structure with coarse grain that consisted of hcp(100) preferred orientation. On the other hand, the cobalt films with lower absorbed hydrogen content have a stacking fault structure of hcp(110)/fcc(220). The total amount of absorbed hydrogen has a liner relationship with the stacking fault ratio and the grain size.

 

(53) Microstructural Investigation of Modulated Structure in Electrolessly Deposited Co-P Films, Naoki Fukumuro, Jin Nishiyama, Shinji Yae, and Hitoshi Matsuda, Trans. Mater. Res. Soc. Jpn., 35(1), 55-58 (2010).

              The depositing conditions were investigated for obtaining a modulated structure that appeared between an amorphous structure and a columnar structure in electroless Co-P alloy films. The microstructure of electroless Co-P films was found to be sensitively dependent on the variation of the deposition rate controlled by both the solution pH and the stirring strength. Uniform modulated structure Co-P film was formed in the limited deposition rate range. Cross-sectional transmission electron microscopy clarified that the modulated structure Co-P film consists of a periodic array of granules less than 100 nm separated by amorphous channels enriched with phosphorous. The modulated structure Co-P film was comprised of hard and soft magnetic components.

 

(54) Influence of Displacement Reaction on Electrodeposition of Noble Metal Particles on Silicon, Shinji Yae, Megumi Kawai, Takashi Matsuda, Naoki Fukumuro, and Hitoshi Matsuda, Trans. Mater. Res. Soc. Jpn., 35(1), 73-76 (2010).

              In this paper, we investigate electrodeposition of Pt, Pd and Au particles on n-Si using a double potential step method that applies single pulse potential of -1 to -8 V vs. SCE and then maintains constant potential at -0.3 V. An aqueous solution of H₂PtCl₆, PdCl₂ or HAuCl₄ at pH 1.7 is used for the electrodeposition of each metal. The particle density of Pt is increased with a negative shift of the pulse potential and then remains nearly constant. The Pd particle density changes with the pulse potential in a similar manner to the Pt particle case. The particle density of Au is much higher than that of Pt, and it is independent of the pulse potential. Immersion of bare n-Si wafers in the H₂PtCl₆ solution under the open-circuit condition deposits no particles but produces silicon oxide. Immersion in a H₂PtCl₄ (Pt(II)) solution, under the same condition as the H₂PtCl₆ (Pt(IV)) case, deposits Pt particles on n-Si. Immersion in a HAuCl₄ solution deposits almost the same particle density of Au as electrodeposition. These displacement reactions, which involve cathodic reduction of metal ions and anodic oxidation of Si, influences the electrodeposition behavior.

 

(55) Pd Assisted HF Etching of Si: Electrochemical Measurement, M. Tashiro, S. Yae, Y. Morii, N. Fukumuro, and H. Matsuda, ECS Trans., Vol. 33, No.16, 173-180 (2011).

              Metal-assisted HF etching of Si has attracted considerable attention as a new electroless method that can produce porous Si by immersing metal-modified Si in a HF solution without bias. Such etching generally uses not only metal-modified Si but also an oxidizing agent. Palladium exhibits high activity in assisted etching under dissolved-oxygen-free and dark conditions. In this study, we investigate the Pd assisted HF etching of n-Si by electrochemical measurements. The potential of Pd metal on Si is more negative than the potential of hydrogen evolution at open circuit conditions. Anodic current generation of Pd-modified Si electrodes at positive bias and the localization of etching under Pd films at low thickness indicate that Pd catalyzes the anodic dissolution of Si and the cathodic hydrogen evolution.

 

(56) New Surface-Activation-Process for Electroless Deposition of Adhesive Metal (Ni, Cu) Films on Si Substrates, S. Yae, K. Sakabe, N. Fukumuro, S. Sakamoto*, and H. Matsuda, *Nippon Oikos Co., Ltd., ECS Trans., Vol. 33, No.18, 33-37 (2011).

              We report a new surface-activation process for direct electroless deposition of adhesive metal films on silicon (Si) substrates. This process, which electrolessly forms metal nanorods in Si, consistsof three steps: Step 1) displacement deposition of metal nanoparticles; Step 2) metal-particle-assisted hydrofluoric acid etching for catalytic nanopore formation; and Step 3) autocatalytic electroless deposition of metal film on the Si surface. In this study, our new surface-activation process is successfully applied not only to nickel and cobalt but also to adhesive copper film deposition on Si substrates.

 

(57) Thermal Desorption Spectroscopic Study of Hydrogen in Electrodeposited Ni-P Films, T. Takemoto, N. Fukumuro, S. Yae, and H. Matsuda, ECS Trans., Vol. 33, No.21, 11-15 (2011).

              The objective of this study is to reveal the atomistic state of hydrogen in electrodeposited Ni-P films by thermal desorption spectroscopy. Two peaks corresponding to the desorption of hydrogen occupying regular interstitial sites and the break-up of vacancy-hydrogen (Vac-H) clusters were observed in electrodeposited pure Ni film. With an increase in phosphorus content, the crystallinity of electrodeposited Ni-P films decreased and the hydrogen desorption from the interstitial sites and Vac-H clusters disappeared. The amount of diffusible hydrogen increased abruptly with the increase in the amorphous phase in Ni-P film.

 

(58) Influence of Si Surface Condition on Electroless Displacement Deposition of Pt Particles, K. Takami, S. Yae, K. Yamagishi, N. Fukumuro, and H. Matsuda, ECS Trans., Vol. 33, No.21, 17-24 (2011).

              The displacement reaction, which is the immersion of Si wafers into a metal-salt solution containing HF, has been applied to prepare catalytic fine metal particles for metal-assisted HF etching, photoelectrochemical solar cells, and autocatalytic plating. The particle density of Pt particles deposited by displacement reaction on n-Si was different based on the solution used for Si chemical oxidation prior to the deposition. Particle density correlates not with the electrical state density at the SiOx/Si interface but with the contact angle of pure water and the microroughness of the oxidized n-Si surface. A model of the deposition process of Pt particles on an oxidized n-Si surface is proposed.

 

(59) Catalytic nanopores for electroless deposition of adhesive metal films on silicon: Applications to various silicon substrates including multi- and micro-crystalline, Shinji Yae, Keisuke Sakabe, Tatsuya Hirano, Naoki Fukumuro, and Hitoshi Matsuda, Phys. Stat. Sol. (c), 8(6), 1769-1773  (2011).

           Metal-particle-assisted hydrofluoric acid etching of silicon (Si) is a unique method of preparing Si nanopores with metal nanoparticles at the bottom of each nanopore. Autocatalytic electroless deposition, which is the conventional method to metalize nonmetallic substrates, requires catalyzation of the substrates before deposition. For Si substrates, obtaining adhesive metal films with conventional catalyzation pretreatments is difficult. We recently developed a new method to produce adhesive metal films on Si substrates using catalytic nanopores that consists of three steps: 1) displacement deposition of metal nanoparticles; 2) Si nanopore formation by metal-particle-assisted hydrofluoric acid etching; and 3) autocatalytic electroless deposition of metal films. In this study, the new method is applied not only to previously reported p-Si (100) 1 Ω cm substrates but also to various Si substrates, such as low and high resistibility, p- and n-types, (100), (111), and (110) planes, and single-, multi- and micro-crystalline substrates. Adhesive and bright metal films were formed on all Si substrates.

 

(60) Rh電析膜中の水素誘起超多量空孔の影響, 福室直樹，成田真嗣，八重真治，松田　均, 表面技術, 62(6), 317-318 (2011)

              Rh電析膜中の水素の存在状態とその効果について検討した。水素はRh膜中に過飽和に固溶して、多量の空孔、双晶、積層欠陥およびナノボイド等の欠陥構造を形成して存在する。水素誘起超多量空孔からの水素の脱離に伴う拡散促進効果によって、低温でRh膜の再結晶現象が認められた。

 

(61)  Surface-Activation Process for Electroless Deposition of Adhesive Metal (Ni-B, Cu) Films on Si Substrates Using Catalytic Nanoanchors, Shinji Yae, Keisuke Sakabe, Naoki Fukumuro, Susumu Sakamoto, and Hitoshi Matsuda, J. Electrochem. Soc., 158(9), D573-577 (2011).

              Autocatalytic electroless deposition, which is a conventional method to metalize nonmetallic substrates, requires catalyzation of substrates before deposition. For silicon (Si) substrates, obtaining adhesive metal films with conventional catalyzation pretreatment is difficult. In this study, we develop a new surface-activation process for the direct electroless deposition of adhesive metal films on Si substrates that consists of three steps: (1) metal nanoparticle formation by electroless displacement deposition; (2) Si nanopore formation by metal-particle-assisted hydrofluoric acid etching; and (3) metal filling in nanopores and metal-film formation on the whole Si surface by autocatalytic electroless deposition. The metal nanorods in the Si act as catalytic nanoanchors to promote autocatalytic electroless metal deposition and improve the adhesion of the metal films on the Si substrates. This process was successfully applied not only to nickel-boron alloy but also to copper film deposition on Si substrates.

 

(62) Influence of hydrogen on room temperature recrystallisation of electrodeposited Cu films: thermal desorption spectroscopy, N. Fukumuro, T. Adachi, S. Yae, H. Matsuda and Y. Fukai, Trans. Inst. Met. Finish., 89(4), 198-201 (2011).

              The mechanism of recrystallisation observed at room temperature in electrodeposited Cu films has been examined in light of the enhancement of metal atom diffusion by hydrogen induced superabundant vacancies. Thermal desorption spectroscopy revealed that Cu films electrodeposited from acid sulphate bath containing some specific additives showed a pronounced peak, which was ascribed to the break-up of vacancy–hydrogen clusters. The amount of desorbed hydrogen was comparable to that of vacancy type clusters estimated in previous positron annihilation experiments. The grain size of Cu films increased as hydrogen desorption proceeded. Such grain growths were not observed in the films deposited from the baths without additives. These results indicate that the room temperature recrystallisation of electrodeposited Cu films is caused by hydrogen induced superabundant vacancies.

 

(63) 無電解ニッケルめっき液のゼロエミッションリサイクル, 高上豪倫, 大藪 剛, 川上 浩, 福室直樹, 八重真治, 松田 均, 表面技術, 62(12), 712-716 (2011).

              A new recycling electroless nickel plating system has been developed using nickel hypophosphite as the source of metallic ions and as a reducing agent. In the system, phosphite ions, which are deleterious for the plating process, are fixed as the precipitate of calcium phosphite. Then they are removed from the solution. During repetitive plating operations, we maintained the plating solution composition and pH as almost constant values. The quantitative change of the reaction products provides theoretical confirmation that the system can be characterized as a ‘zero-emission-type recycling model’.

 

(64) アルゴンプラズマエッチングがシリコンへの金属微粒子無電解置換析出に及ぼす影響

藤原良太, 萩原泰三, 松田貴士, 江籠卓馬, 福室直樹, 八重真治, 松田 均

表面技術, Vol.63, pp.581-584 (2012)

Fine metal particles can be formed on Si by electroless displacement deposition, in which Si wafers are simply immersed into a metal-salt solution containing HF. Depending on the kind of metal and the surface condition of Si substrates, the particle density of deposited metal varies widely. Especially, Pt particle density greatly changes according to the Si surface condition. In this study, we investigate the influence of Ar-plasma etching of Si on the Pt particle density. Single crystalline n-Si (100) wafers were etched by Ar plasma using a radio frequency glow discharge spectrometer. An amorphous Si layer was formed on etched Si surfaces. Pt particles, with the particle density of four hundred times higher than that for non-etched Si wafers, were deposited by immersing Ar-plasma-etched Si wafers in a H₂PtCl₆ solution containing HF. The Pt particle density was decreased by removing the amorphous layer and as well as chemical etching of single-crystalline Si wafer. It was proved that the influence of the Ar-plasma-etching extended at least 0.5 μm to the interior of single-crystalline Si beneath the amorphous layer.

 

(65) ジニトロスルファト白金（�U）酸浴から電析したPt膜中の水素

久永尚哉, 福室直樹，八重真治，松田　均

表面技術, Vol.63, pp.596-597 (2012)

著者らは金属の電気めっきの際に生じる水素共析について系統的に調べているが、本研究においては、ジニトロスルファト白金酸めっき液での電気めっきにおけるPt中の水素について調べた。めっき基材としてTiを用い、ジニトロスルファト白金酸(H₂Pt(NO₂)2SO₄)水溶液でPtを約1μm電着させた。このPt膜中の水素の熱分離挙動および熱処理後のミクロ組織観察を透過型電子顕微鏡を用いて実施した。これらの実験から、ジニトロスルファト白金酸を用いたPtめっきではめっき層中に大量の水素が導入されており、熱処理によって水素の離脱が生じ、金属原子の拡散の活発化により結晶粒成長が進行することが明らかとなった。

 

(66) Catalytic activity of noble metals for metal-assisted chemical etching of silicon

S. Yae, Y. Morii, N. Fukumuro, H. Matsuda

Nanoscale Res. Lett., Vol.7, 352(pp.1-5) (2012)

Metal-assisted chemical etching of silicon is an electroless method that can produce porous silicon by immersing metal-modified silicon in a hydrofluoric acid solution without electrical bias. We have been studying the metal-assisted hydrofluoric acid etching of silicon using dissolved oxygen as an oxidizing agent. Three major factors control the etching reaction and the porous silicon structure: photoillumination during etching, oxidizing agents, and metal particles. In this study, the influence of noble metal particles, silver, gold, platinum, and rhodium, on this etching is investigated under dark conditions: the absence of photogenerated charges in the silicon. The silicon dissolution is localized under the particles, and nanopores are formed whose diameters resemble the size of the metal nanoparticles. The etching rate of the silicon and the catalytic activity of the metals for the cathodic reduction of oxygen in the hydrofluoric acid solution increase in the order of silver, gold, platinum, and rhodium.

 

(67) シリコン基板上に形成した金属ナノロッドの太さと無電解めっき膜の密着性

榎本将人, 八重真治, 阪本進, 福室直樹, 松田均

表面技術, Vol.63, pp.781-783 (2012)

著者らはこれまで、Si基板上への金属膜の形成において金属ナノロッドを利用することで密着性の向上を図ることに成功している。本報告においては、形成する金属ナノロッドの太さと形成する無電解めっき膜の密着性の関係を調べた。Si単結晶基板に対し、0.15 M HF‐1 mM AgNO₃水溶液浸漬によるAgナノ粒子の形成、7.3 M HF水溶液への浸漬によるナノ孔の形成、および無電解メッキによるNi‐B膜の形成を行なった。テープを用いた密着性試験およびミクロ組織観察を実施した。これらの実験から、0.15 M HF‐1 mM AgNO₃水溶液浸漬時間の増加とともにナノ粒子の粒径は大きくなり、これは密着性を向上させることにつながったことを明らかにした。

 

(68) Metal-Assisted Chemical Etching of Silicon Using Oxygen as an Oxidizing Agent: Influence of HF Concentration on Etching Rate and Pore Morphology Metal-Assisted Silicon Dissolution

S. Yae, Y. Morii, M. Enomoto, N. Fukumuro, H. Matsuda

ECS Trans., Vol.50, No.37, pp.31-36 (2013)

Metal-assisted chemical etching of silicon is an electroless method that can produce porous silicon by immersing metal-modified silicon in a HF solution without electrical bias. We have been studying this etching using dissolved oxygen as an oxidizing agent and recently reported that the catalytic activity of noble metal particles including silver, gold, platinum, and rhodium, influences the cathodic reduction of oxygen and controls the etching rate. In this paper, we investigate the influence of the HF concentration on the etching rate and the pore morphology. In the case of high HF concentration, the etching rate is independent of the HF concentration and depends on the oxygen concentration and the catalytic activity of the metal particles. In the low HF concentration case, the etching rate depends on the HF concentration and is independent of the oxygen concentration and the catalytic activity. The pore morphology is also changed by the HF concentration.

 

(69) Hydrogen in Platinum Films Electrodeposited from Dinitrosulfatoplatinate Solution

N. Hisanaga, N. Fukumuro, S. Yae, H. Matsuda

ECS Trans., Vol.50, No.48, pp.77-82 (2013)

The influence of hydrogen on the microstructure of Pt films electrodeposited from a dinitrosulfatoplatinate(II) solution was investigated with thermal desorption spectroscopy, X-ray diffraction, transmission electron microscopy, and scanning electron microscopy. Two pronounced desorption peaks were observed in the thermal desorption spectrum of hydrogen from the Pt films. The total amount of desorbed hydrogen in the range from 300 to 1100 K in the atomic ratio (H/Pt) was 0.1. The deposited Pt film consisted of fine grains (〜10 nm) and many nano-voids. The lattice parameter of the Pt grains was lower than that of bulk Pt. Drastic grain growth and reduction in the lattice contraction occurred from heat treatment at a temperature corresponding to the first hydrogen desorption peak of 500 K.

 

(70) AFM Analysis for Initial Stage of Electroless Displacement Deposition of Silver on Silicon Surface

T. Ego, T. Hagihara, Y. Morii, N. Fukumuro, S. Yae, H. Matsuda

ECS Trans., Vol.50, No.52, pp.143-153 (2013)

We deposit fine metal particles on silicon (Si) by a displacement reaction, which is the immersion of Si wafers into a metal-salt solution containing hydrofluoric acid, that consists of a local cathodic reduction of metal ions and a local anodic dissolution of Si. In this study, the displacement deposition of silver (Ag) nanoparticles on the Si(111) surface with an atomic step-terrace structure is investigated by atomic force microscopy. Ag particles are uniformly deposited on the Si surface without influence of the step-terrace structure. The particle density of the deposited Ag decreases and then increases with immersion times between 1 and 15 s. The step-terrace structure disappears and nanoholes are formed by an immersion time of 15 s. We propose a model of Ag particle density and Si surface changes with time.

 

(71) Electroless Metallization of Silicon Using Metal Nanoparticles as Catalysts and Binding-Points Electrodeposition and Semiconductor Metallization

S. Yae, M. Enomoto, H. Atsushiba, A. Hasegawa, C. Okayama, N. Fukumuro, S. Sakamoto, H. Matsuda

ECS Trans., Vol.53, No.6, pp.99-103 (2013)

Gold nanoparticles on silicon work not only as catalysts to initiate autocatalytic electroless metal deposition but also as bindingpoints between the deposited metal film and the silicon surface. Conventional catalysts of autocatalytic electroless metal deposition, such as palladium and silver, require heat treatments or anchor formation to obtain practical adhesion of deposited metal films on silicon. Gold nanoparticles can directly produce adhesive metal films on flat silicon surfaces without any treatments. Crosssectional transmission electron microscopic observation reveals that gold nanoparticles form an alloy with silicon at the room temperature. This alloy is expected to improve the adhesion of metal film on silicon.

 

(72) Noble Metal Recovering by Electroless Displacement Deposition on Silicon Powder

K. Fukuda, S. Yae, N. Fukumuro, S. Sakamoto, H. Matsuda

ECS Trans., Vol.53, No.19, pp.69-76 (2013)

We developed a low-cost, efficient method to recover all noble metals including gold, silver, palladium, rhodium, platinum, osmium, ruthenium, and iridium from aqueous solutions by simply adding hydrofluoric acid (HF) and silicon (Si) powder. The recovery rate depends on the specific surface area of Si, the HF concentration, and the solution temperature. Our method selectively recovers noble metals and copper from a mixture solution of noble and base metal ions, such as nickel, cobalt, and iron, and obtains pure noble metal powder by dissolving Si. The Si powder and the HF solution are expected to be supplied from semiconductor industries, such as the sawdust Si of wafering or dicing and the waste HF solution of wafer cleaning or etching. This new method recovers noble metals from waste (urban mines) using other waste; it also has green electroless deposition.

 

(73) 前処理によりシリコン表面に形成された金属ナノロッドの長さと無電解めっき膜の密着性

榎本将人、八重真治、阪本進、福室直樹、松田均

表面技術、Vol.64、pp.682-684 (2013)

We have developed a surface-activation process for the direct electroless deposition of adhesive metal films on Si substrates. This process forms metal nanorods in Si by using electroless displacement metal nanoparticle deposition, metal-nanoparticle-assisted HF etching of Si, and autocatalytic electroless Ni deposition. The adhesion of metal films increases with metal nanorod length.

 

(74)Hydrogen-Induced Enhancement of Atomic Diffusion in Electrodeposited Pd films

N. Fukumuro, M. Yokota, S. Yae, H. Matsuda, Y. Fukai^*

^*Institute of Industrial Science, The University of Tokyo

J. Alloys Compd., Vol.580 S1, pp.55-57 (2013)

The hydrogen-induced enhancement of atomic diffusion in electrodeposited Pd films on Cu substrate has been investigated with thermal desorption spectroscopy, X-ray diffraction, and transmission electron microscopy. The hydrogen content in Pd films (x = H/Pd) was 2.2〜7.7×10^-2 and decreased with time at room temperature. For Pd films with lower hydrogen contents (x ≦ 4.0×10^-2), lattice contraction and grain growth proceeded as hydrogen desorption proceeded. For Pd films with higher hydrogen contents (x ≧ 5.8×10^-2), fine grains became large columnar grains, and a large-grained Cu-Pd interlayer was formed by interdiffusion between the Cu substrate and the Pd film.

 

(75) Contact Resistance Measurements for Electrodes on Silicon Prepared by Autocatalytic Electroless Metallization Using Metal Nanoparticles

Y. Orita, H. Atsushiba, M. Enomoto, T. Kimura^**, N. Fukumuro, H. Takagami^*, K. Kato^*, S. Sakamoto, M. Hirata, and S. Yae

^*Murata Co., Ltd.

^**Japan Fine Tech Co., Ltd.

ECS Trans., Vol.61, No.10, pp.25-29 (2014)

Recently, we reported on autocatalytic electroless metallization of silicon using gold nanoparticles. This technology is expected to be a useful, low-cost, and reliable method to form electrodes on silicon for several devices, such as solar cells and power devices. For the fabrication of electrodes, it is important that the resistance, consisting of the sheet resistance of the metal patterns and the contact resistance between the metal and silicon, is low. In this study, we measure the contact resistance of metal electrodes on silicon prepared by autocatalytic electroless metallization using gold nanoparticles. The transfer length method is suitable to evaluate the contact resistance between electrolessly plated nickelphosphorus alloy thin films and silicon. The values obtained for the contact resistivity decrease as the film thickness increases from 0.5 to 2.3 μm. This decrease is caused by the decrease of the sheet resistance of the metal films. Reliable values for the contact resistivity were determined to be 0.9 and 1.2 mΩ cm² for p⁺- and n⁺-doped wafers, respectively. The contact resistivity depends on the gold nanoparticle coverage.

 

(76) Adhesion and Interfacial Structure of Metal Film Electrolessly Deposited on Si Using Au Nanoparticles as Catalysts

H. Atsushiba, Y. Orita, S. Sakamoto, N. Fukumuro, and S. Yae

ECS Trans., Vol.61, No.10, pp.9-13 (2014)

We developed a new surface-activation process for autocatalytic electroless metallization of silicon using gold nanoparticles. The gold nanoparticles provide much higher adhesion of electrolessly deposited nickel-boron alloy films on silicon substrates than do silver and palladium nanoparticles. TEM observation and XPS analysis indicate that the electrolessly deposited nickel-phosphorus alloy film directly contacts the gold nanoparticles, silicon-gold metallic alloy is formed at the interface between the silicon substrate and the gold nanoparticles even at room temperature, and an amorphous layer exists between the metals and silicon substrate.

 

(77) Electroless Displacement Deposition of Noble Metal on Silicon Powder for Recovering from Urban Mines

K. Fukuda, N. Fukumuro, S. Sakamoto, and S. Yae

ECS Trans., Vol.61, No.10, pp.1-7 (2014)

We developed a simple recovery method of all noble metals from aqueous solutions by adding silicon (Si) powder and fluoride. This method is expected to be low-cost, because the Si powder and the fluoride solution can be supplied from semiconductor industries, such as the sawdust Si of wafering or dicing and the waste hydrofluoric acid solution of wafer cleaning or etching. In this study, we investigated the recovery of noble metals using a lowtoxic agent instead of a toxic hydrofluoric acid, or sawdust Si powder. This method can recover noble metals using ammonium fluoride or sodium fluoride. The recovery rate with sawdust Si is as high as that using pure Si powder. We found that the recovery of noble metals by this method from aqueous solutions including aqua regia is also possible.

 

(78) 単結晶シリコン上へ無電解置換析出する白金微粒子の数密度

萩原泰三，松田貴士，福室直樹，八重真治

表面技術、Vol.65、pp.495-498 (2014)

Immersing of Si into a solution containing metal-salt and HF deposits fine metal particles onto the Si surface by the electroless displacement deposition. The particle density of deposited metal onto the surface varies widely by kinds of metal-salt and pretreatments of Si. Especially, the particle density of Pt depends a great deal on the pretreatments of Si. In this study, we have investigated the process of Pt electroless displacement deposition. Single crystalline n-Si (100) wafers were pretreated by following three different methods: immersion in a mixture of HF, HNO₃, CH₃COOH and H₂O (3:5:3:22 in volume) (CP4A), ordinary RCA method, and oxidization of Si surface by immersion in HNO₃ after RCA (RCA + HNO₃). The electroless displacement deposition of Pt particles onto Si surface proceeds by immersing Si wafers into a H₂PtCl₆ solution containing HF for 5-900 seconds. On the Si surface pretreated by the CP4A method, Pt particles deposited in the progressive mode. For the RCA method, Pt particles deposited in two-stage progressive mode which is separated at 180 seconds. For the pretreatment of RCA + HNO₃, Pt particles deposited in two-stage progressive mode separated at 120 seconds. These two-stage progressive modes are explained to be caused by local anodic reaction which dissolved and roughed Si surface in electroless displacement deposition solution. However, regardless of the pretreatment method, Pt particles were deposited in the order of 10⁹ cm^-2 in particle density by the deposition for 900 seconds.

 

(79) Hydrogen-Induced Superabundant Vacancies in Electrodeposited Fe-C Alloy Films

N. Fukumuro, S. Kojima, M. Fujino, Y. Mizuta, T. Maruo, S. Yae, Y. Fukai^*

^*Institute of Industrial Science, The University of Tokyo

J. Alloys Compd., Vol.645 S1, pp.404-407 (2015)

Fe-C alloy films containing supersaturated C and H were prepared by electrodeposition, and investigated for the hydrogen behavior in annealing processes utilizing X-ray diffraction and thermal desorption spectroscopy. The H content x_H (x_H = H/Fe) in the films increased from about 0.031 in pure Fe to about 0.36 in Fe-C alloy (x_C = C/Fe = 0.073) in proportion to the C content. The lattice contraction of about 0.2% was observed in pure Fe films, whereas the lattice expansion increasing with C content was observed in Fe-C alloy films. Both the lattice contraction of the Fe films and the lattice expansion of the Fe-C alloy films were decreased as H was desorbed during heat treatments. The atomistic structure of vacancy-hydrogen and vacancy-carbon-hydrogen clusters in Fe-C alloy films is discussed, based on these experimental results.

 

(80) 電析Cu膜における水素誘起粒成長

吉田裕輝, 山崎貴昭, 安達貴良, 福室直樹, 八重真治, 深井　有^*

^*東京大学生産技術研究所

日本金属学会誌、Vol.73、pp.78-81 (2015)

We proposed that the grain growth observed in electrodeposited Cu films at room temperature is caused by hydrogen-induced superabundant vacancy-hydrogen clusters. In this study, the relation between grain growth and hydrogen behavior in the electrodeposited Cu films was investigated using different types of plating baths. The Cu films were electrodeposited from an acid sulfate bath, an acid sulfate bath containing chloride ion, polyethylene glycol, and bis(3-sulfopropyl)disulfide (additive-containing bath), a pyrophosphate bath, and a chloride bath containing citric acid. Thermal desorption spectroscopy revealed that extremely high concentration of hydrogen is contained in the Cu films deposited from the additive-containing bath and the chloride bath. The room-temperature grain growth was observed in these Cu films with passage of time after deposition, concurrently with hydrogen desorption. Such grain growths were not observed in the Cu films with low hydrogen content deposited from the acid sulfate bath and the pyrophosphate bath. The changes in crystal orientation and internal stress during the grain growth of the Cu films differed between the additive-containing bath and the chloride bath. These results suggest that the room-temperature-grain growth was induced by the co-deposited hydrogen in films.

 

(81) Electrochemical Quartz Crystal Microbalance Study of The Electrodeposition of Platinum

T. Hagihara, K. Yaori, K. Iwakura, N. Fukumuro, and S. Yae

Electrochim. Acta, Vol.176 , pp.65-69 (2015)

The electrodeposition of Pt from aqueous solutions of K₂PtCl₄ (Pt(II)), H₂PtCl₆ (Pt(IV)), and a mixture of Pt(II) and Pt(IV) was studied using the electrochemical quartz crystal microbalance (EQCM) method. Pt deposition and cathode current flow began at the same potential in the Pt(II) solution. On the other hand, in the Pt(IV) solution, the cathode current increased at a more positive potential followed by Pt deposition at a more negative potential than in the Pt(II) solution. This difference in the potentials is due to the reduction reaction of Pt(IV) to Pt(II). Thus, Pt deposition in the Pt(IV) solution occurred in two potential ranges. In the first range, which was more positive than the second one, Pt was deposited via the reduction of Pt(II) to Pt(0). In the second range, direct deposition from Pt(IV) to Pt(0) proceeded, but was followed by hydrogen adsorption, which inhibited further Pt deposition.

 

(82) Catalytic Activity of Ru for Metal-Assisted Etching of Si

D. Sadakane, K. Yamakawa, N. Fukumuro, and S. Yae

ECS Trans., Vol.69, No.2, pp.179-184 (2015)

Metal-assisted etching of Si is an electroless method that can produce porous Si by immersing metal-modified Si in a HF solution without electric bias. We reported that the etching rate of noble metal-modified Si in a simple HF solution including oxygen under dark conditions depended on the catalytic activity of metal for oxygen reduction. Only palladium exhibits high activity for the etching under dissolved oxygen-free and dark conditions. In this study, the catalytic activity of Ru for the etching of Si has been investigated. Ru nanoparticles are electrodeposited on Si substrates. Electroless displacement deposition using RuCl₃ solution including HF can form Ru nanoparticles not on mirror-polished n-Si substrate but on roughed one. The etching rate of Ru-particledeposited Si is similar to that of Rh case which is changed with dissolved oxygen concentration. On the roughed Si substrates, the Ru nanoparticles assist the etching even under oxygen-free and dark conditions.

 

(83) Optical Property of Porous Silicon Produced By Metal-Assisted Etching

K. Yamakawa, S. Sakamoto, N. Fukumuro, and S. Yae

ECS Trans., Vol.69, No.2, pp.185-191 (2015)

Antireflection of Si surface is an important technology to increase the photocurrent density of solar cells. Recently, porous Si has been researched for replacing Si nitride which is common material of antireflective coating (ARC). In this study, we have investigated the optical properties of porous Si thin films, thinner than doped layers for p-n junction formation of Si solar cells, produced by metal-assisted etching. The structure of porous Si is changed with the size of catalytic Ag nanoparticles, composition of etching solution, and etching time. The reflection of porous film formed Si wafers is much lower than that of mirror polished wafers. Reflectance spectra and ellipsometric analysis indicate that the thin porous Si films act as optical films and they are expected to function as suitable ARC for crystalline Si solar cells.

 

(84) Effect of Epitaxial Growth of Gold Nanoparticles on Si Substrates on Adhesion of Electrolessly Deposited Metal Films

N. Yamada, H. Atsushiba, S. Sakamoto, N. Fukumuro, and S. Yae

ECS Trans., Vol.69, No.39, pp.59-63 (2015)

Electrolessly deposited metal films on silicon substrates using gold nanoparticles as catalysts yield much higher adhesion than that by using palladium or silver nanoparticles. In this study, the structure of the gold nanoparticles is analyzed by X-ray diffraction and transmission electron microscopy. Single crystalline gold nanoparticles are epitaxially deposited on silicon substrates and silicon-gold alloy is formed at the interface. Those epitaxially grown gold nanoparticles cause the high adhesion of electrolessly deposited nickel films on silicon substrates.

 

ベストペーパー賞受賞

(85) シリコンウェーハ上への直接無電解めっき

八重真治, 山田直輝, 阪本　進, 福室直樹

MES2015（第25回マイクロエレクトロニクスシンポジウム）論文集, pp.63-66 (2015)

Gold nanoparticles are produced on silicon substrates by electroless displacement deposition simply immersing in a gold salt solution including hydrofluoric acid. Such gold nanoparticles work not only as catalysts to initiate autocatalytic electroless metal deposition but also as bindingpoints between the deposited metal film and the silicon surface. Gold nanoparticles can directly produce adhesive metal films on silicon surfaces without any treatments. For the fabrication of electrodes on such silicon devices as solar cells and power devices, it is important that the contact resistance between the metal and silicon is low. The contact resistivity between electrolessly deposited nickel-phosphorus alloy thin films and p⁺- and n⁺-doped silicon substrates are 0.9 and 1.2 mΩ cm², respectively.

 

(86) アルゴンプラズマエッチングを施した単結晶シリコン上に無電解置換析出する白金微粒子の数密度

萩原泰三, 藤原良太, 松田貴士, 山川加能, 福室直樹, 八重真治

表面技術、Vol.67、pp.34-39 (2016)

By immersion of silicon into a solution containing metal-salt and hydrofluoric acid, fine metal particles are deposited onto the silicon surface by electroless displacement reaction. The particle density of deposited metal varies widely depending on the kind of metal and the surface condition of silicon substrates. The platinum particle density changes to an especially large degree according to silicon surface conditions. This study revealed the relation of deposition time to platinum particle density deposited by electroless displacement deposition on argonplasma-etched Si surfaces. Single-crystalline n-Si（100）wafers were chemically pretreated and were then etched with argon plasma using a radiofrequency glow discharge spectrometer. The electroless displacement deposition of platinum particles onto the silicon surface proceeds by immersion of silicon wafers into a hexachloroplatinic（IV）acid solution containing hydrofluoric acid. Platinum particles were deposited in the progressive mode until 450 s, and reached 10¹¹ cm^-2. The particle density was decreased by immersion longer than 450 s, and was maintained at 10¹⁰ cm^-2 after 900 s. Dimples appeared on the silicon surface by immersion for 600 s and longer. Dimples were formed by local anodic dissolution of silicon under the platinum particles. The initial increase and posterior decrease in the particle density are explained, respectively, as the influence of argon-plasma etching and the dissolution of the influenced region of a silicon wafer.

 

(87) 電析Cu 膜の室温粒成長に及ぼす水素の影響

福室直樹, 吉田裕輝, 山崎貴昭, 深井　有^*, 八重真治

^*東京大学生産技術研究所

日本金属学会誌、Vol.80、pp.736-739 (2016)

The influence of co-deposited hydrogen on the room-temperature grain growth of electrodeposited Cu films was investigated. The films were prepared from ethylenediamine (EDA)-complex and ethylenediaminetetraacetic acid (EDTA)-complex baths and examined with respect to hydrogen concentration, the initial microstructure, residual stress and impurities. Thermal desorption spectroscopy revealed that extremely high concentrations of hydrogen was contained in the Cu films deposited from both the EDA- and EDTA-complex baths. The room-temperature grain growth of these Cu films proceeded after deposition and concurrently with the gradual desorption of hydrogen. During the grain growth, the (111)-oriented texture remained almost unchanged but the tensile stress decreased. Compared with the Cu films electrodeposited from other types of baths, temporal changes in crystal orientation and residual stress varied in the different baths, however grain growth proceeded with a decrease in hydrogen as previous. These results indicate that the primary cause of room-temperature grain growth of electrodeposited Cu films is hydrogen-induced superabundant vacancies.

 

(88) ナノホールアレイを用いた反射防止によるシリコン太陽電池の高効率化

山川加能，榎本将人, 阪本　進, 八重真治

表 面技術、Vol.67、pp.689-670 (2016)

Antireflection of a silicon surface is an important means of increasing the photocurrent density and thereby improving solar cell conversion efficiency. We have produced thin nanohole arrays on silicon solar cells using metal-assisted-etching with electrolessly deposited silver nanoparticles. The nanohole array acts as an optical film, decreasing silicon surface reflectance, increasing photocurrent, and causing no damage to the pn-junction.

 

(89) SiCへの直接無電解めっき

山田直輝，福田健二, 阪本　進，福室直樹, 八重真治

MES2016（第26回マイクロエレクトロニクスシンポジウム論文集、pp.83-86 (2016)

We have developed a novel method of direct electroless plating on single crystalline 4H-silicon carbide (SiC) wafers by using gold nanoparticles as catalysts. Gold nanoparticles on SiC are produced by immersing in a tetrachloroauric(III) acid solution containing hydrofluoric acid or potassium hydroxide under UV-light illumination using a Hg-Xe short arc lamp. The gold-nanoparticle-deposited SiC wafers can initiate autocatalytic electroless plating of nickel-phosphorous (Ni-P) alloy. Uniform Ni-P films are produced on the SiC wafers. The adhesion of the Ni-P films formed by the present method is as high as no peeling occurs by a tape test without any further treatment such as heat treatment. The gold nanoparticles on SiC work not only as catalysts to initiate autocatalytic electroless deposition but also as binding-points between the deposited metal film and the SiC surface.

 

(90) Influence of Hydrogen Adsorption on Electrodeposition of Platinum from Chloro Complex Solution

A. Yokoyama, S. Karatsu, M. Sumikawa, N. Fukumuro, and S. Yae

ECS Trans., 75(52) pp.55-60 (2017)

The influence of hydrogen adsorption on the electrodeposition of platinum was investigated using an electrochemical quartz crystal microbalance (EQCM) method and thermal desorption spectroscopy (TDS). Three types of hydrogen adsorption were observed in a tetrachloroplatinate(II) solution by the EQCM method: UPD-H1, UPD-H2, and OPD-H in order from positive to negative potential. Platinum films were electrodeposited potentiostatically at 0 for UPD-H1, -0.1 and -0.2 for UPD-H2, and -0.3 V vs. Ag/AgCl for OPD-H. The amount of hydrogen desorbed by TDS, that is, the hydrogen incorporated into the films by electrodeposition, depended on the deposition potential. At the potential for UPD-H1, no hydrogen was incorporated into the bulk of the platinum films. At the UPD-H2 potential, hydrogen was uniformly incorporated in the platinum films at the content of ca. 0.02 in an atomic ratio of H/Pt. At the OPD-H potential, a fairly large amount of hydrogen, 0.1 of content, was incorporated uniformly in the platinum films.

 

(91) Displacement deposition of gold nanoparticles and electroless deposition of nickel films on silicon-carbide (4H-SiC) wafers

K. Fukuda, N. Yamada, D. Sadakane, S. Sakamoto, N. Fukumuro and S. Yae

Trans. Inst. Met. Finish.95(4) pp.203-206 (2017)

Metallisation of silicon carbide (SiC) wafers is a key technology for producing efficient power devices. Conventional autocatalytic electroless deposition cannot produce adherent metal films directly on SiC substrates. The authors applied their recently developed surface-activation process for electroless metal-film deposition on silicon wafers to SiC wafers. Gold nanoparticles were produced on 4H-SiC substrates by displacement deposition after immersing the substrates in a tetrachloroauric(III) acid solution that includes hydrofluoric acid or potassium hydroxide. The size and the particle density of the deposited gold are changed with deposition parameters such as the surface condition of the substrates, the solution composition, and the UV-light illumination. The gold nanoparticles work not only as catalysts to initiate autocatalytic electroless deposition but also as binding-points between the metal film and the SiC surface. Adherent and uniform nickel-phosphorus alloy films are produced on such SiC substrates by autocatalytic electroless deposition without any further treatments.