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Shuichi NAGASAWA Masamitsu TANAKA Naoki TAKEUCHI Yuki YAMANASHI Shigeyuki MIYAJIMA Fumihiro CHINA Taiki YAMAE Koki YAMAZAKI Yuta SOMEI Naonori SEGA Yoshinao MIZUGAKI Hiroaki MYOREN Hirotaka TERAI Mutsuo HIDAKA Nobuyuki YOSHIKAWA Akira FUJIMAKI
We developed a Nb 4-layer process for fabricating superconducting integrated circuits that involves using caldera planarization to increase the flexibility and reliability of the fabrication process. We call this process the planarized high-speed standard process (PHSTP). Planarization enables us to flexibly adjust most of the Nb and SiO2 film thicknesses; we can select reduced film thicknesses to obtain larger mutual coupling depending on the application. It also reduces the risk of intra-layer shorts due to etching residues at the step-edge regions. We describe the detailed process flows of the planarization for the Josephson junction layer and the evaluation of devices fabricated with PHSTP. The results indicated no short defects or degradation in junction characteristics and good agreement between designed and measured inductances and resistances. We also developed single-flux-quantum (SFQ) and adiabatic quantum-flux-parametron (AQFP) logic cell libraries and tested circuits fabricated with PHSTP. We found that the designed circuits operated correctly. The SFQ shift-registers fabricated using PHSTP showed a high yield. Numerical simulation results indicate that the AQFP gates with increased mutual coupling by the planarized layer structure increase the maximum interconnect length between gates.
Kentaro TOKORO Shunsuke SAITO Kensaku KANOMATA Masanori MIURA Bashir AHMMAD Shigeru KUBOTA Fumihiko HIROSE
We report room-temperature atomic layer deposition (ALD) of SnO2 using tetramethyltin (TMT) as a precursor and plasma-excited humidified argon as an oxidizing gas and investigate the saturation behaviors of these gases on SnO2-covered Si prisms by IR absorption spectroscopy to determine optimal precursor/oxidizer injection conditions. TMT is demonstrated to adsorb on the SnO2 surface by reacting with surface OH groups, which are regenerated by oxidizing the TMT-saturated surface by plasma-excited humidified argon. We provide a detailed discussion of the growth mechanism. We also report the RT ALD application to the RT TFT fabrication.
Hien Ba CHU Hiroshi SHIRAI Chien Dao NGOC
A simple approach is presented for designing an antipodal Vivaldi antenna in this paper. A new and better estimation of the low frequency end of the operational range is shown. Final dimensions of the antenna parameters are determined by using the High Frequency Structure Simulator (HFSS). The proposed antenna has a simple configuration but exhibits low return loss, good radiation characteristics, and high and flat gain in the operating ultra wideband frequency range (3.1-10.6 GHz). Lastly, the fabrication has been done along with the specification to confirm the properties by measurements.
Guolong CUI Lingjiang KONG Xiaobo YANG Jianyu YANG
This letter mainly deals with the multi-rank signal detecting problem against Spherically Invariant Random Vector (SIRV) background with Invariance theory. It is proved that generalized likelihood ratio test (GLRT), Rao test and Wald test are all the Uniformly Most Powerful Invariant (UMPI) detectors in SIRV distributions under a mild technical condition.
Ayako SAWADA Ryuzoh IKEDA Eiichi TAMIYA Taketoshi YOSHIDA Takashi OYABU Hidehito NANTO
We succeeded in isolating two formaldehyde-degrading fungi, the strains BDF001 and 002, from the rhizospheric soil of formaldehyde-exposed potted golden pothos (Epipremnum aureum), and from the formaldehyde-exposed cultivation soil without plants, respectively. Sequence analysis of the ITS-5.8S rDNA regions confirmed that both fungi were of the same species, Trichoderma virens. These two strains, however, obviously differed from each other in formaldehyde resistance and formaldehyde-degrading ability. The formaldehyde concentration allowing a growth during cultivation for 10 days for the strain BDF001 was up to 0.6%, and that for the strain BDF002 was up to 0.35%. The strain BDF001 showed a formaldehyde-degrading activity 2.3 times higher than that of the strain BDF002. Ranges of the possible growth pH and temperature in the presence of 0.21% formaldehyde were between 4 and 9, and around 25, respectively.
Takashi YAMAMOTO Yukiko IZUMI Naoyuki SUGIYAMA Kazuhiro YOSHIKAWA Hideki HASHIMOTO Yoshihiro SUGITA
We prepared HfO2 films by atomic layer deposition (ALD) on three kinds of silicon substrate surfaces (chemical oxide, HF-last surface and thermal oxide), and characterized their morphologies, structures, compositions, and crystallinities by physical analysis. The results revealed that the as-deposited HfO2 films consisted of nano-crystalline particles with a different crystalline system from that of the annealed films. The size of the nano-crystalline particles on the film on the chemical oxide was smaller than those on the other surfaces. The reason is thought to be the difference in OH concentration on the substrate surface. The predominant crystalline phases of all HfO2 films were monoclinic after annealing. Moreover, the film prepared on the chemical oxide had the smoothest surface after annealing. However, island structures with grain boundaries developed in the films on the other surfaces.
Kenichi KASAHARA Takahiro NUMAI Hideo KOSAKA Ichiro OGURA Kaori KURIHARA Mitsunori SUGIMOTO
The VSTEP concept and its practical application in the form of an LED-type pnpn-VSTEP demonstrating low power consumption through electro-photonic operational modes are both shown. Further, with focus primarily on the new laser-mode VSTEP with high-intensity light output and narrow optical beam divergence, the design features such as threshold gain and optical absorptivity, device fabrication, and characteristics are explained. The possibility of ultimate performance based mainly on electrical to optical power conversion efficiency, important from the application viewpoint of optical interconnection, are also discussed. Also, as two examples of functional optical interconnection achieved by VSTEP, serial-to-parallel data conversion and optical self-routing switches are shown. Finally, future opto-electronic technologies to be developed for two-dimensionally integrable surface-type optical semiconductor devices, including the VSTEP, are discussed.
Kenichi KASAHARA Takahiro NUMAI Hideo KOSAKA Ichiro OGURA Kaori KURIHARA Mitsunori SUGIMOTO
The VSTEP concept and its practical application in the form of an LED-type pnpn-VSTEP demonstrating low power consumption through electro-photonic operational modes are both shown. Further, with focus primarily on the new laser-mode VSTEP with high-intensity light output and narrow optical beam divergence, the design features such as threshold gain and optical absorptivity, device fabrication, and characteristics are explained. The possibility of ultimate performance based mainly on electrical to optical power conversion efficiency, important from the application viewpoint of optical interconnection, are also discussed. Also, as two examples of functional optical interconnection achieved by VSTEP, serial-to-parallel data conversion and optical self-routing switches are shown. Finally, future opto-electronic technologies to be developed for two-dimensionally integrable surface-type optical semiconductor devices, including the VSTEP, are discussed.