Tetsu Tanaka

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.

MOSFET Nonvolatile Memory with High-Density Cobalt-Nanodots Floating Gate and $\hbox{HfO}_{\bf 2}$ High-k Blocking Dielectric

Abstract: We report high-performance MOSFET nonvolatile memory with high-density cobalt-nanodots (Co-NDs) floating gate (the density is as high as 4-5 × 1012 /cm 2 and the size is ~2 nm) and HfO2 high-k blocking dielectric. The device is fabricated using a gate-last process. A large memory window, high-speed program/erase (P/E), long retention time, and excellent endurance till 106 P/E cycles are obtained. In addition, the discrete Co-NDs make dual-bit operation successful. The high performance suggests that high work-function Co-NDs combined with high-k blocking dielectric have a potential as a next-generation nonvolatile-memory candidate.

Minimizing the local deformation induced around Cu-TSVs and CuSn/InAu-microbumps in high-density 3D-LSIs

Abstract: One of the most serious reliability issues, the local deformation produced in the stacked LSI die/wafer with respect to the die thickness and the sub-surface structures formed after several stress-relief methods are systematically and extensively studied. From the electron backscatter diffraction (EBSD) analysis, a more than one degree (>1°) of local misorientation is created in the stacked LSI Si around μ-bump region. This induces a large tensile stress above the μ-bump region and relatively small compressive stress in the bump-space region, which leads to an enhancement in the n-MOSFET mobility in the μ-bump region and decrease in mobility at bump-space region. As compared to CuSn system, the InAu μ-bump induced huge amount of tensile stress (> 300 MPa) in the stacked LSI die even for the bonding temperature of 200 °C. The groove structures or scratches found at the background surface after stress relief by plasma etching (PE) or Dry Polishing (DP) severely deteriorates the device characteristics after stacking, owing to the enhanced local deformation as against the stress relief method of chemical mechanical polishing (CMP). Even after 500 cycles of temperature cycle (TC) test, a 20 μm-width Cu-TSV array with 40- μm pitch values induces not only around −570 MPa of compressive stress in the stacked LSI die, but also a large variation in the induced stress values between different TSVs in the same array. For the LSI die/wafer thickness of anything less than 50 μm, the Young modulus (E) and Hardness (H) of the thinned die no longer behaves like a bulk single crystal Si, which severely increases the reliability risks in the highly integrated 3D-LSIs.

Self-Assembly Process for Chip-to-Wafer Three-Dimensional Integration

Abstract: We have proposed chip-to-wafer stacking for three-dimensional (3D) integration. To realize the chip-to-wafer 3D integration, five key technologies of through-Si interconnection and microbump formation, chip-to-wafer alignment, underfilling, and chip thinning were investigated. Three-layer stacked chips with a layer thickness of several tens microns were fabricated by using the key technologies. Each chip was serially and mechanically aligned and bonded onto a support LSI wafer. In addition, we newly introduce a stacking technique using self-assembly as a key process for advanced chip-to-wafer 3D integration. High-precision alignment with an accuracy of within 1 mum was obtained and stacking throughput can be dramatically improved by the self-assembly.

Characteristics of microwave oscillations induced by spin transfer torque in a ferromagnetic nanocontact magnetoresistive element

Abstract: We have investigated the microwave oscillations due to a spin transfer effect induced by direct current in ferromagnetic nanocontact magnetoresistive (NCMR) elements with a current-perpendicular-to-plane spin-valve structure consisting of an FeCo/FeCo–AlOx nano-oxide layer/FeCo multilayer for the reference/spacer/free layers, respectively. Characteristic microwave oscillations were observed in the NCMR elements at different magnetization states induced by the application of a spin-polarized current, which are considered to be related to the introduction of a ferromagnetic NC to spacer layer (large interlayer coupling) and the resonance concerning the stability of the magnetization states of the free and reference layers around the NCs. A marvelously narrow full width at half maximum (FWHM) of l0–20 MHz is observed under a high applied magnetic field where the reference layer magnetization is slightly off axis relative to the pinned direction. By contrast, a wider FWHM of 80–600 MHz is observed at the magn...

Die-Level 3-D Integration Technology for Rapid Prototyping of High-Performance Multifunctionality Hetero-Integrated Systems

Abstract: We proposed a die-level 3-D integration technology for rapid prototyping of high-performance multifunctionality hetero-integrated systems. Commercially available 2-D chips with different functions and sizes could be processed and integrated in die level. To realize the die-level 3-D integration, fine-sized backside through silicon via (TSV) and novel detachable technologies are developed. In this paper, we demonstrated a prototype 3-D stacked image sensor system using the die-level 3-D integration technology. Three different functional chips of CMOS image sensor, correlated double sampling, and analog-to-digital converter, which were fabricated by different technologies, were processed to form fine-sized backside Cu TSV of 5- μm diameter and metal microbumps in die level. Each chip was sequentially stacked after evaluating the basic function to form a known-good-die 3-D stacked system. The fundamental characteristics of each functional chip were successfully evaluated in the fabricated prototype 3-D stacked image sensor system.

Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence

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.

Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease

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...

Complete genome sequence of Pseudomonas aeruginosa PAO1, an opportunistic pathogen.

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.