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Author

Tetsu Tanaka

Other affiliations: NTT DoCoMo, Tokyo Medical and Dental University, Fujitsu  ...read more
Bio: Tetsu Tanaka is an academic researcher from Tohoku University. The author has contributed to research in topics: Wafer & Chip. The author has an hindex of 38, co-authored 406 publications receiving 10375 citations. Previous affiliations of Tetsu Tanaka include NTT DoCoMo & Tokyo Medical and Dental University.
Topics: Wafer, Chip, Wafer bonding, Interposer, Flip chip


Papers
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Proceedings ArticleDOI
15 Apr 2012
TL;DR: In this article, the thermo-mechanical reliability challenges induced by high-density Cu TSVs and metal micro-joining are discussed, and the influence of mechanical stress induced by Cu TSV and microbump-underill joining on device characteristics are evaluated.
Abstract: The thermo-mechanical reliability challenges induced by high-density Cu TSVs and metal micro-joining are discussed. Cu TSV with the diameter of 20-µm induced the maximum compressive stress of ∼1 GPa at the Si substrate adjacent to them after annealed at 300°C. Depart from Cu TSV, the stress/strain in Si substrate changed to tensile stress and finally going to zero, where the TSV pitch is larger than twice of TSV size. However, in high density Cu TSV array with small TSV pitch, the Si substrate within small TSV spacing keep large compressive stress, which will seriously affect the mobility in active Si area, and thus device characteristics. Also, these large compressive stress leads to not only extrusion and peeling of Cu TSV, but also die cracking. The thermo-mechanical stress was produced during the bonding using high-density metal bumps. CuSn bump of 20-µm size has induced compressive stress of 140MPa beneath Si wafer surface, and it penetrates deeper area with large stress value after the bonding. The drain current and electron mobility of n-MOSFET which was located 15µm distance from microbump are changed by ∼10 % due to the local tensile stress of 500 MPa induced by microbump. Electron mobility changed varying with the distance from microbump. Influences of mechanical stress induced by Cu TSVs and microbump-underill joining on device characteristics were also evaluated.

14 citations

Journal ArticleDOI
TL;DR: In this article, the influence of Cu diffusion at the backside surface of a thinned dynamic random access memory (DRAM) chip for 3-D integration on memory retention characteristics was electrically evaluated.
Abstract: The influence of Cu diffusion at the backside surface of a thinned dynamic random access memory (DRAM) chip for 3-D integration on memory retention characteristics was electrically evaluated. A DRAM test chip was bonded to a Si interposer at 300 °C for 2 min and thinned down to 30-μm thickness. The DRAM cell characteristics, which show 50% failure at 200 μs, were not degraded from the packaged sample (prethinning) even after chip bonding, chip thinning, and no-Cu postannealing for 30 min at 300 °C. Meanwhile, the DRAM cell array shows 50% failure at 70 μs after an intentional Cu diffusion from the backside surface for 30 min at 300 ° C. It means that Cu atoms at the back surface reach the Si-SiO2 interface of the front surface in active areas and cause functional failures such as increasing carrier recombination rate, consequently shortening retention time. However, the NMOS transistor characteristics show no significant change even after Cu diffusion. The on-current performance characterized by majority carriers is not an effective criterion to characterize sensitively the Cu contamination effect.

14 citations

Proceedings ArticleDOI
01 Dec 1998
TL;DR: In this paper, the impact of ultra-shallow junction and tilted channel implantation with respect to source/drain resistance (R/sub sd/), and short-channel effect (SCE) based on physical gate length and effective gate length (L/sub eff/) was discussed.
Abstract: The impact of ultra-shallow junction and tilted channel implantation (TCI) is discussed with respect to source/drain resistance (R/sub sd/), and short-channel effect (SCE) based on physical gate length (L/sub gate/) and effective gate length (L/sub eff/) We obtained the following results: (1) A shallower junction improves the SCE immunity for a given L/sub gate/, but not with respect to L/sub eff/ (2) The essential factor for the reduction of R/sub sd/ is not the sheet resistance (R/sub sheet/) of source/drain (S/D) extensions, but the junction tailing profile (3) TCI was found to be effective for increasing the current drive ability due to the reduced L/sub eff/ for a given off current (I/sub off/) (4) The effectiveness of TCI was confirmed by a CV L/sub eff/ extraction method (5) Encouraged by the above results, high-performance 01 /spl mu/m pMOSFETs were demonstrated using a 1 keV, B/sup +/ or BF/sub 2//sup +/ implantation and TCI technology The device achieved a high drive current (I/sub drive/) of 360 /spl mu/A//spl mu/m (@V/sub g/=V/sub d/=15 V, I/sub off/=1nA//spl mu/m)

14 citations

Proceedings ArticleDOI
03 Jul 2013
TL;DR: From in vivo experiments, the Si opto-neural probe with multiple optical waveguides and metal-cover is one of the most versatile tools for optogenetics and confirmed that light induced membrane current sink in locally stimulated area.
Abstract: We have developed a Si opt-neural probe with multiple waveguides and metal cover for highly accurate optical stimulation. This neural probe had 16 recording sites, three optical waveguides, and metal cover for suppressing light leakage. We evaluated electrochemical properties of the recording sites, and confirmed that the neural probe had suitable characteristics for neural recording. We also demonstrated the optical stimulation to the neurons expressing ChR2 using our probe. As a result, we succeeded multisite optical stimulation, and observed that no light leakage from the optical waveguides because of the metal cover. From in vivo experiments, we successfully recorded optically modulated local field potential using the fabricated Si neural probe with optical waveguides. Moreover, we applied current source density analysis to the recorded LFPs. As a result, we confirmed that light induced membrane current sink in locally stimulated area. Our Si opto-neural probe with multiple optical waveguides and metal-cover is one of the most versatile tools for optogenetics.

14 citations


Cited by
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Journal ArticleDOI
11 Jun 1998-Nature
TL;DR: The complete genome sequence of the best-characterized strain of Mycobacterium tuberculosis, H37Rv, has been determined and analysed in order to improve the understanding of the biology of this slow-growing pathogen and to help the conception of new prophylactic and therapeutic interventions.
Abstract: Countless millions of people have died from tuberculosis, a chronic infectious disease caused by the tubercle bacillus. The complete genome sequence of the best-characterized strain of Mycobacterium tuberculosis, H37Rv, has been determined and analysed in order to improve our understanding of the biology of this slow-growing pathogen and to help the conception of new prophylactic and therapeutic interventions. The genome comprises 4,411,529 base pairs, contains around 4,000 genes, and has a very high guanine + cytosine content that is reflected in the biased amino-acid content of the proteins. M. tuberculosis differs radically from other bacteria in that a very large portion of its coding capacity is devoted to the production of enzymes involved in lipogenesis and lipolysis, and to two new families of glycine-rich proteins with a repetitive structure that may represent a source of antigenic variation.

7,779 citations

Journal ArticleDOI
TL;DR: Antiinflammatory therapy targeting the interleukin‐1β innate immunity pathway with canakinumab at a dose of 150 mg every 3 months led to a significantly lower rate of recurrent cardiovascular events than placebo, independent of lipid‐level lowering.
Abstract: BackgroundExperimental and clinical data suggest that reducing inflammation without affecting lipid levels may reduce the risk of cardiovascular disease. Yet, the inflammatory hypothesis of atherothrombosis has remained unproved. MethodsWe conducted a randomized, double-blind trial of canakinumab, a therapeutic monoclonal antibody targeting interleukin-1β, involving 10,061 patients with previous myocardial infarction and a high-sensitivity C-reactive protein level of 2 mg or more per liter. The trial compared three doses of canakinumab (50 mg, 150 mg, and 300 mg, administered subcutaneously every 3 months) with placebo. The primary efficacy end point was nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. ResultsAt 48 months, the median reduction from baseline in the high-sensitivity C-reactive protein level was 26 percentage points greater in the group that received the 50-mg dose of canakinumab, 37 percentage points greater in the 150-mg group, and 41 percentage points greater in t...

5,660 citations

Journal ArticleDOI
31 Aug 2000-Nature
TL;DR: It is proposed that the size and complexity of the P. aeruginosa genome reflect an evolutionary adaptation permitting it to thrive in diverse environments and resist the effects of a variety of antimicrobial substances.
Abstract: Pseudomonas aeruginosa is a ubiquitous environmental bacterium that is one of the top three causes of opportunistic human infections. A major factor in its prominence as a pathogen is its intrinsic resistance to antibiotics and disinfectants. Here we report the complete sequence of P. aeruginosa strain PAO1. At 6.3 million base pairs, this is the largest bacterial genome sequenced, and the sequence provides insights into the basis of the versatility and intrinsic drug resistance of P. aeruginosa. Consistent with its larger genome size and environmental adaptability, P. aeruginosa contains the highest proportion of regulatory genes observed for a bacterial genome and a large number of genes involved in the catabolism, transport and efflux of organic compounds as well as four potential chemotaxis systems. We propose that the size and complexity of the P. aeruginosa genome reflect an evolutionary adaptation permitting it to thrive in diverse environments and resist the effects of a variety of antimicrobial substances.

4,220 citations