Chikara Hayashi

Deposition of Ultra Fine Particles Using a Gas Jet

Use of a gas jet for the transfer and deposition of metal or ceramic UFP has been studied. Individual particles having a diameter of less than 0.1 µm, are produced by the so-called gas evaporation method. Deposition of the UFP can be made by preparing a colliding gas flow with UFP on a solid surface. Uniformly distributed deposition of different metals or ceramics, regardless of specific gravity, can also be made. A similar technique is also usable with frozen gas UFP (CO2 for example). A CO2 UFP blizzard can remove photoresist without contamination or damage to a substrate (thin film chromium coated on glass). The transfer and deposit technique could be a basic method for handling UFP for industrial application.

Behavior of Ultrafine Metallic Particles on Silicon Wafer Surface

The diameter of particles which adversely affects the yield has been shrinking as ULSI devices are more and more miniaturized. Ultrafine particles with diameters of 0.1 μm or less have become important recently. Ultrafine particles of this type are expected to be difficult to remove. This study has established a method to evaluate ultrafine particle removal efficiency. Ultrafine metallic particles with diameters of several to several hundreds of nanometers were deposited on the Si surface using a gas deposition method. The removal efficiency of the ultrafine particles using various cleaning solutions was investigated. APM (NH 4 OH-H 2 O 2 -H 2 O) cleaning can remove 150 nm Au particles, but cannot remove ultrafine Au particles with a diameter less than several tens of nanometers. In addition, the Si surface becomes rougher when a DHF-H 2 O 2 cleaning is performed to remove Au ultrafine particles. This is believed to be because noble metals such as Au, Ag, and Cu, which feature a higher electronegativity than Si, attract electrons from Si facilitating Si oxidation

Characterization of sliced multilayer zone plates for hard x rays (invited)

Circular zone plates for hard x rays, fabricated by dc planar magnetron sputtering, have been characterized using monochromatized synchroton x rays. The zone plates consisted of either 5 or 20 pairs of altenating WSi2 and C layers. The minimum focal spot size attained was less than 3 μm× 10 μm in the vertical and horizontal directions, respectively. The efficiency of the zone plate with 20 layer pairs was determined to be about 4.5%. An x‐ray transmission image of a No. 2000 mesh Cu grid and an x‐ray fluorescence image of a patterned Co thin film were measured, and it was demonstrated that a high‐resolution image could be obtained with the present zone plate. The possibility of implementing the phase zone plate in hard x‐ray range is considered.

Fabrication and Characterization of Multilayer Zone Plate for Hard X-Rays

A zone plate for 8 keV X-rays with alternative WSi2 and C layers was fabricated using a DC planer magnetron sputtering. The zone plate had 20 pairs of a high aspect ratio for hard X-rays. Its thickness was about 50 µm. An X-ray interference pattern through the zone plate was observed using monochromated synchrotron X-rays, and a focusing property of the zone plate was confirmed. The focal length was about 67 mm and the spot size (FWHM) was smaller than 8 µm.

The use of nanoparticles as coatings

Abstract Ultrafine particles having diameters in the range larger than 1 nm and less than 1 μm can be called nanoparticles. Chemically pure nanoparticles are usually produced by evaporation and condensation in a controlled environment. Scientific engineers may consider nanoparticles as materials suitable for the fabrication of micrometer-sized elements of macroproducts, while scientists consider the atomic and electronic structure and properties of nanoparticles. We previously proposed a deposition and/or erosionn process called the gas deposition process, where nanoparticles entrained in a tiny carrier gas jet collide and are deposited onto a target substrate ( Jpn. J. Appl. Phys., 23 (1984) L910–L912). The electrical circuit pattern (approximately 40 μm width), the capacitor (BaTiO 3 ), oxide superconducting contacts (yttrium, bismuth) etc. are exapmles of components of the process. Analysis of the thermal behavior of nanoparticles during the process will be discussed. We believe that this process or any other pollution-free and localized process should be developed as a bridging technology between the macro and atomic worlds.

Spin-on Cu films for ultralarge scale integrated metallization

We have developed the spin-on Cu metal (SOM) process to fill trenches and vias down to 0.3 μm. SOM is a liquid material that contains an organic solvent and dispersed ultrafine particles as a source of Cu. This solution was applied to a Si wafer using a spin coater to form a film. Coated wafers were baked at 623–673 K for 10 min in a reducing atmosphere. The end result is a Cu film. Contrary to the conventional deposition techniques, the SOM process is simple but advantageous to its gap filling, planarization, and cost consideration.

Metal tapes using ultra fine powder prepared by gas evaporation method

In the last decade, investigations of ultrafine powders prepared by the gas evaporation method have been carried out in Japan. Metals were evaporated in inert gases such as Xe or He or Ar. Ultra fine particles of 50 to 2000 A in diameter were precipitated like soot. The basic magnetic charcterstics have already been reported in previous papers. The coercive force of ferromagnetic fine powders can be controlled by changing the constituents of the alloy up to 2500 Oe. Resistance heating, plasma jet, induction heating or LASER have been examined as evaporation heat sources. Viedo and Audio tapes were tested in Fuji Photo Film Co.,Ltd.. One of the typical tapes gave 12.8 dB higher output level at 5 MHz and 10.0 dB better C/N at 4.5 MHz compared with commercially available highest quality tape. Reduction of the saturation magnetization of the tape is 0% after being kept in the condition that 60°c, 90% R.H. for one week. Still frame is more than 30 minutes.

Preparation and Properties of Ultra Fine Metal Powders

Ultra fine metal powders of less than 0.1 µm in diameter can be produced in Ar, He or He+H2 gaseous atmosphere by using the gas evaporation method with several heating methods. Three heating methods, that is, plasma jet, open arc and high frequency induction, have been tested to heat the surface of molten metal and alloy by the authors for producing ultra fine powders. Operating conditions of the ultra fine metal powder apparatus, the relation between the mean particle size of ultra fine Ni powder and the operating condition of the plasma jet, the similar data for ultra-fine Cu powder produced by an induction heating method and magnetic properties of ferromagnetic material powders are described.

Ultra Fine Particle Films by Gas Deposition Method

Ultra fine particles(UFP) of organic and inorganic materials can be formed by the gas evaporation method(gas condensation method). In the gas deposition method, particles formed by the gas evaporation method in an evaporation chamber are carried to another chamber (a deposition chamber) through a pipe. Particles are accelerated in the pipe with a gas flow and come out of a nozzle located in the deposition chamber which is being evacuated down to less than 10 torr and deposited on a substrate to form UFP films. The final speed of the particles depends on the pressure difference between the evaporation chamber and the deposition chamber. The particles speed exceeds 500m/s and adhesion strengths of the films reach 50OKgf/cm 2 as well as vacuum deposition films in the condition that the pressure of the evaporation chamber is at 4 atms. Patterns of spots and lines with 50μm size and also wider films can be formed on a substrate without a masking system. The process is effective for repairing electric connecting lines or producing electrodes and condensers on an industrial scale.

From Imported Scientific Vacuum Technology to the Evolution of Vacuum Industry in Japan (a Historical Review)

303 平成20年 9 月 9 日 日本真空協会50周年記念講演会にて講演 # 株アルバック社友 〒2538543 茅ヶ崎市萩園2500 1 ガッサンディは真空の中に神を持ち込まないと説いたので,彼 を西欧近代科学思想家の祖とする人たちも多い.他方では,真 空技術家の祖と言ってよいゲーリッケは‘真空は神の居場所 ()’としていた.思うに‘真空(完全真空)’はそれぞれの 人の幻想である.物理的理屈にこだわるなら‘完全真空’の中 で座標の原点は個人にしかないわけである. † 挿話(英国 New Scientist 誌ほかによる).宥和のころの話を 一つ. Sir. ウォルトン・レーリーはジェームス一世王のために有罪人 とされた.アトミズムを支持していたからである.レーリー は,英国人による最初のアメリカ植民約100人(ノースカロラ イナの Roanoke 島に上陸,1585年)のなかに航海案内人,航 海図作成者としてトーマス・ハリオット(Harriott)を参加さ せた.ハリオットは数学と天文学と航海術の先生をレーリーの もとで務めていたのだが,数学の><の記号はハリオットに由 来し,天体望遠鏡を自作し(ガリレオと同じ頃)木星の周期測 定もした.鏡とレンズを自作できた.島に滞在中の彼に与えら れていた使命は,陸地の探検と土着民の言葉の調査であった が,自発の実験で,ガラス板についての光の屈折の法則を正確 に求めた.それは1602年のことで,スネルの仕事よりも19年 早い.彼はまた,球状の水滴に入る太陽光の通過の道を計算し て虹の角径も示した.よく知られているデカルトの虹の図解の 発表(1637年)より30年以上も前のことであった. ハリオットがケプラーの質問に答えている(1606年).デモ クリトス的真空を述べている.“密度の高い透明な連続帯とみ えるものは,光線の邪魔をする物質的部分と光を透す非物質的 部分(Vacuum)とで出来ている.光線がまっすぐにつき抜け ると見えても,それは多数の直線的部分の集合なのだ”これ はデモクリトスのアトミズムと同様な考えで,そのころアトミ ズム(Vacuum+Atom)は無神論とされていたので,ハリオ ットも監禁されたが,有罪人とはされなかった.思想家として の権威と名声を備えていたデカルトが,科学技術家ハリオット のことをとりあげていないのはどうしてかわからない. 近代のアトミズムで考えると,光子波の作用範囲を波長 l の 3 倍くらいとすると,原子径10-8 cm ほどのところを通り抜 ける時間は10-18秒より短い.原子核はふつうの光(可視光) とは反応しない.透明体を通り抜ける光の速さは真空中とは異 なるが桁が違うほどではない.