Showing papers by "Tetsu Tanaka published in 2022"

Room-Temperature Cu Direct Bonding Technology Enabling 3D Integration with Micro-LEDs

Abstract: This paper describes Cu direct bonding at room temperature for wearable micro-LED display. Still, the conventional bonding methods of micro-LEDs with solder micro-bumps have heat problems during bonding and difficulty achieving a narrow pitch. Using a unique method developed in this paper, it is possible to bond micro-LEDs to a 3D-IC chiplet without using the micro-bumps. Here, The 30 x 30 arrays of 0.1-mm-square blue micro-LEDs are assembled, bonded, and interconnected on a sapphire substrate through electroplated Cu, and successful emission from the blue micro-LEDs is confirmed. The bonding strength of the room-temperature Cu direct bonding with the micro-LEDs and a yield enhancement technique is also described. Finally, we emphasize the high potential of massively parallel chiplet self-assembly using liquid surface tension.

Enhancement of carrier mobility in metal-oxide semiconductor field-effect transistors using negative thermal expansion gate electrodes

Abstract: Strained-Si technology is crucial to improving the performance of metal-oxide-semiconductor field-effect transistors (MOSFETs). To introduce large strain into the channel, we proposed a structure for the negative thermal expansion gate electrode. In this study, we used manganese nitride as the gate material, which is a negative thermal expansion material. The fabricated MOSFETs with the manganese nitride gate showed a 10% increase in electron mobility compared to the MOSFET with the Al gate. The results show that the negative thermal expansion gate technology is promising as a technology booster for MOSFET scaling.

Accidental duodenal foreign body of toothbrush removed laparoscopically: a case report

Abstract: Foreign body ingestion is a common case in daily medical care, and it usually passes through the entire gastrointestinal tract naturally and is excreted in the feces. However, long and sharp foreign bodies may be difficult to pass naturally due to their shape. Here, we present a rare case of a duodenal foreign body, a toothbrush, that required laparoscopic surgical removal after a failed endoscopic attempt.A 51-year-old male with intellectual disability presented to our hospital due to fever. Initially, he was diagnosed with aspiration pneumonia by chest X-ray and blood examination. However, abdominal X-ray examination suggested a foreign body, and a computed tomography scan revealed a toothbrush in the duodenum. Therefore, upper gastrointestinal endoscopy was immediately attempted to remove it, but it could not be safely removed because the handle part of the toothbrush seemed deeply embedded in the duodenal mucosa. Therefore, this case was diagnosed as duodenal incarceration of the toothbrush, and it was removed by laparoscopic surgery. The operation was performed safely, and the patient's postoperative course was good without any complications. The extracted toothbrush was 15 cm in length.We experienced a rare case of a duodenal foreign body, which was a toothbrush. The duodenal foreign body was safely removed by laparoscopic surgery for the first time.

3D-stacked retinal prosthesis chip with binary image capture and edge detection functions for human visual restoration

Abstract: Retinal prosthesis is a promising treatment for vision degeneration. However, clinical experiments show that the patients can only recognize several grayscales at low resolution with electrical stimulation. This paper proposes a retinal prosthesis chip with binarization and edge detection functions to maximize the brightness difference and reduce redundant information. The binarization operation is designed as a column-parallel processing element for saving space. Moreover, the fill factor achieves 50.79% by separating the sensor and stimulator into different chips. Finally, the SPICE simulator verified the effectiveness of the proposed circuit, which achieves an FoM of 110nW/(frame·pixel).

Implementation of Light and Dark Adaptation Function for High QOL 3D-Stacked Artificial Retina Chip

Abstract: The increase in the number of visually impaired people has led to active research on artificial retinas. In our laboratory, we study a fully-implantable retinal prosthesis using a 3D-stacked artificial retina chip, which provides highly visible visual information with edge enhancement and binarization functions. However, since the visibility of objects can be significantly reduced when the ambient illumination is low, the light and dark adaptation (LDA) function is needed to provide the same visibility regardless of the ambient illumination. Conventional LDA functions have operability, comfort, and circuit area problems in these situations. In this study, we proposed a small-area LDA function circuit that provided visual information with high quality of life and evaluated a prototype circuit.

MO632: Impact of Diabetic Kidney Disease on Coronary Artery Plaque Progression

Abstract: The aim of this study was to evaluate the relationship between diabetic kidney disease (DKD) and change in coronary plaque volume in asymptomatic diabetes patients. In this prospective observational study, we analyzed 79 asymptomatic type 2 diabetes patients (age, 63.7 ± 8.1 years; male, 69.3%) without prior history of coronary artery disease who underwent serial 320-row computed tomography coronary angiography with an interscan interval of more than 24 months (median 37.7 months). Total coronary plaque volume was assessed at baseline and after 3 years, using QAngio CT (MEDIS) for vessel diameters greater than 1.5 mm in the three main branches. The primary endpoint was coronary plaque progression (PP), which was defined as the absolute change in coronary plaque volume during the 3 years. PP was compared among four groups, which were divided according to the presence or absence of DKD at baseline and after 3 years, as follows: Group 1 (no DKD at baseline, no DKD after 3 years), Group 2 (DKD at baseline, no DKD after 3 years), Group 3 (no DKD at baseline, DKD after 3 years), Group 4 (DKD at baseline, DKD after 3 years)]. DKD was defined as albuminuria >30 mg/g Cr or eGFR <60 mL/min/1.73 m2. We conducted univariate linear regression analysis to assess the association of DKD groups with PP. Plaque volumes were significantly greater in Group 4 than in Group 1 both at baseline and after 3 years (Table 1). PP was also significantly greater in Group 4 than in Group 1 (β-coefficient: 293.6, P < 0.01). Group 4 had greater PP compared with Group 1 after adjustment (β-coefficient: 181.6, P < 0.05). DKD may be an independent risk factor for coronary plaque progression in asymptomatic type 2 diabetic patients without a history of cardiovascular disease. Early therapeutic intervention in such patients may prevent the onset of coronary artery disease.

Electrochemical characterization of ZnO-based transparent materials as recording electrodes for neural probes in optogenetics

Abstract: In the elucidation of brain functions, neuroscience has garnered attention in the realization of brain-machine interfaces, deep brain stimulation, and artificial intelligence. Optogenetics is a biological technique used to control neural activities via optical stimulation. It is one of the most effective approaches used to investigate brain functions. This study proposed to employ the transparent recording electrode to enhance the performance of neural probes for optogenetics. Compared with conventional metal recording electrodes, the proposed transparent recording electrodes have the potential to obtain higher signal-to-noise ratios when placed over optical stimulation points. To develop transparent recording electrodes, we used ZnO-based materials with good biocompatibility and transparency for utilization as biomedical electrodes. Considering saline as one of the main components of living organisms, we investigated the fundamental electrochemical characteristics of ZnO-based electrodes in saline through electrochemical impedance spectroscopy and cyclic voltammetry. The results showed that nondoped ZnO and Al-doped ZnO, deposited by radio frequency magnetron sputtering, exhibited a broad potential window. An electrical double layer was found to strongly act on the interface between the electrodes and solution rather than a redox reaction. In addition, this study reports the effects of crystallization and dopant on the electrochemical characteristics of the ZnO-based electrodes. The transparent ZnO-based electrode developed herein is a promising candidate to enhance the performance of neural probes for optogenetics and can be effectively applied in biological devices.

Gapless Chip‐in‐Carrier Integration and Injectable Ag/AgCl‐Epoxy Reference Electrode for Bilayer Lipid Membrane Sensor

Abstract: There are emerging needs for bilayer lipid membrane (BLM) sensors utilizing the vastly and highly developed molecular recognition ability of membrane proteins, especially those combined with CMOS chips. However, this type of BLM sensor has barely been studied so far mainly because of two problems: (i) the difficulty of their fabrication processes resulting from chip‐carrier discontinuity, (ii) a skill‐dependent and manual fashion to form BLMs. Here, we introduce a gapless chip‐in‐carrier integration process utilizing parylene as a gap filler and a microfluidic packaging method with an injectable Ag/AgCl‐epoxy reference electrode. These methods allow for subsequent photolithography processes and later microfluidic‐based BLM formation where the surface continuity of a microchannel is crucial. As a proof‐of‐concept device, we fabricated chip‐in‐carrier assemblies with a dummy chip coupled with a microfluidic system for BLM formation compatible with simultaneous optical observation. With this device, we validated the capability to form BLMs by microfluidic technique and characterized the configuration of a formed BLM through the observation of fluorescent localization. This chip integration and microfluidic packaging scheme can provide a solution for the full implementation of CMOS ICs with BLM sensors and broaden the possibilities of practical applications in the engineering and medical fields. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

(Invited, Digital Presentation) Development of 3D-Stacked Artificial Retina Chip with 3DIC/TSV and Advanced Packaging Technology

Abstract: 3DIC/TSV is the most promising candidate for high-performance and low-power computing devices. They have many advantages such as short wiring length, small pin capacitances, high packing density, ultra-parallel operation. Among several types of 3D-IC technologies, multiple chips-to-wafer (MCtW) stacking can stack known-good chips fabricated with different technologies and sizes, leading to a true 3D heterogeneous system. We have developed a fully implantable retinal prosthesis with a 3D-stacked artificial retina (AR) chip. In the 3D-stacked AR chip, the photoreceptor chip and stimulus current generator with image processing circuits are vertically stacked and electrically connected by many TSVs. Furthermore, advanced packaging technology like FOWLP is being developed to implement multiple AR chips in a flexible substrate to obtain a wide viewing angle. This leads to small chip size, lightweight, large fill-factor, high resolution, and high quality of life patients.

Developing a Low-Temperature Flip-Chip Bonding Technology with In/Au Microbumps to Suppress the Thermal Load on Spintronics Devices

Abstract: Spin transfer torque magnetic random-access memory (STT-MRAM) with magnetic tunnel junction (MTJ) devices, which are among the spintronics devices, have many advantages, such as high programing speed and sufficient endurance. Therefore, currently, the spintronics devices are being thoroughly studied. However, they suffer from low thermal stability; thus, low-temperature integration and packaging technologies need to be developed. In this study, we applied In/Au microbumps, which have low bonding temperature and high thermal stability, to a flip-chip bonded STT-MRAM onto a Si interposer. No effect of the flip-chip bonding process on the STT-MRAM cell was observed. Investigation results indicated that low-temperature bonding technology with In/Au microbumps are promising for accelerating the integration of spintronics devices.

[A Case in Which Inferior Vena Cava Stent Placement Was Effective for Inferior Vena Cava Stenosis Due to Metastatic Liver Tumor].

Abstract: A 60s woman was diagnosed with cecal cancer with multiple liver metastases(final pathology was T4aN1M1[H1])and underwent ileocecal resection and D3 dissection. She did not wish for postoperative chemotherapy and surgical treatment of liver metastases. One and a half years after surgery, she developed extremity edema of lower legs and hypoalbuminemia, and she gained 20 kg. Contrast-enhanced CT showed stenosis of the inferior vena cava due to liver metastases, which was markedly improved the symptoms by placement of an inferior vena cava stent. Inferior vena cava stent placement is a minimally invasive treatment and can be an option as it can be expected to improve quality of life in some cases.

Direct fabrication of SU‐8 microchannel across an embedded chip for potentiometric bilayer lipid membrane sensor

Abstract: Membrane proteins play a critically important role, especially in molecular and cellular transport processes, which makes them the most prevalent drug targets and also to be a good sensing element for biosensing applications. However, the skill-dependent and manual fashion to form bilayer lipid membranes (BLMs) has limited their use for application purposes. Here, we introduce a fabrication technique of SU-8 microchannel suitable for microfluidic-based BLM formation and show a preliminary step of our ISFET-based BLM sensor. Making notches on the corners of a rectangular through-wafer hole etched in a silicon carrier substrate reduced the gap width between an embedded chip and the carrier as close as possible, leading to the gap depth of 4 μm. SU-8 microchannel on the chip-carrier assembly was directly fabricated by UV exposure through a bonded quartz lid and developing SU-8 through the fluidic ports drilled in the lid, without needing a sealing process typically causes an alignment mismatch or void formation. Finally, the capability to form BLMs was tested and proven by the successfully encapsulated fluorescent dye in microwells fabricated on the embedded chip. This paper is the first report of the successful formation of BLMs on a chip-in-carrier assembly by the microfluidic method.