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Yoshimi S.,Dai Nippon Printing | Yoshimi S.,NMEMS Technology Research Organization | Fujimoto K.,Dai Nippon Printing | Fujimoto K.,NMEMS Technology Research Organization | And 9 more authors.
Proceedings - Electronic Components and Technology Conference | Year: 2013

A Silicon interposer with through silicon via (TSV) has become important key components of 3D integration. It is used as an intermediate carrier and a wiring device for IC components like logics, memories, sensors, and so on. Due to wiring with custom design on front and back side, a TSV interposer enables to adapt the fine pitch IO terminals of the mounted ICs to the IO geometries of the package level. However the key problem facing the TSV interposer is a cost issue. In this paper, TSV based interposer fabrication process for 3D packaging has been presented and the process uniformity with 300 mm wafer was evaluated for cost reduction and yield improvement. TSVs of 50 μm in diameter were formed on a 300 mm wafer of 500 μm in thickness by deep reactive ion etching (DRIE) process and the vias were isolated with SiO2 layer, followed by barrier/seed layers of Ti/Cu deposition. The TSVs were filled with solid Copper (Cu) using electroplating of optimized periodic pulse reverse (PPR) and chemical mechanical polishing (CMP) process also developed to remove the Cu overburden. For void free TSV interconnects and uniformity improvement, the Cu electroplating process was simulated with 300 mm wafer and developed with the simulation result. The process uniformity of Cu electroplating was equivalent to the simulation result and void free TSV interconnects were successfully formed. The RDL lines were formed on the TSV by Cu electroplating and the RDL lines were electrically isolated with the dielectric PBO film. The TSV interposer of 500 μm thickness has been fabricated successfully with MEMS processes and the vias were in good conductivity from the top to the bottom. The distribution of via etching process, via filling process and CMP process were evaluated and no significant failures were observed. The uniformity of the via etching process was less than 5 %. The distribution of Cu overburden thickness was less than 100 μm. The dishing amount of Cu via after CMP was less than 10 μm. The electric characteristics of RDL leakage current and via resistance were measured. The leakage current between RDL lines was about 10-9 A so that the RDL lines were electrically isolated. The average value of via resistances was 2.43 ohm and via resistances were normally distributed with tangible electric characteristics. The fabrication process of TSV based silicon interposer with 300 mm wafer by MEMS processes was successfully demonstrated in terms of mass production. © 2013 IEEE.

Zhu Q.S.,NMEMS Technology Research Organization | Zhu Q.S.,Japan National Institute of Advanced Industrial Science and Technology | Toda A.,Meltex Inc. | Zhang Y.,NMEMS Technology Research Organization | And 5 more authors.
International Journal of Electrochemical Science | Year: 2013

In this work, we presented a "bottom-up" and a "two-step" electrodeposition formulas for copper filling within high aspect through polymer holes (TPHs), which are needed for integrating flexible bio-micro-electro-mechanical system (bio-MEMS) sensors with conventional CMOS circuits. By using the "two-step" electrodeposition formula, a void-free copper filling is successfully realized for TPHs with the diameter of 20 μm and height of 125 μm in a common plating solution. The void-free filling effect was attributed to the preformed "V" profile after the first-step deposition. The filling time is reduced by about 80% than that of the "bottom-up" filling formula. The results suggest that the "two-step" deposition mode can be a potential solution to the long time of the through polymer holes filling. © 2013 by ESG.

Zhu Q.S.,NMEMS Technology Research Organization | Zhu Q.S.,Japan National Institute of Advanced Industrial Science and Technology | Toda A.,Meltex Inc. | Zhang Y.,NMEMS Technology Research Organization | And 5 more authors.
Journal of the Electrochemical Society | Year: 2014

In this work, the Cu electrodeposition was carried out for the filling of through silicon via (TSV) using an additive-free Cu electrolyte and periodic pulse reverse (PPR) current. It was attempted to understand the filling mechanism by PPR plating and then to explore a potential solution for void-free filling in easy electrolytes. The filling results showed that the void size was continually reduced as decreasing current density. A void-free filling was obtained at low current density. During the Cu growth process, a "V" shape filling structure occurred at the upper of the via and the ratio of this structure increased with the decrease of current density. The electrochemical analyzes results demonstrated that at low current density, the potential during forward deposition was more uniform along the depth, and during reverse pulse the potential difference between the shallow and deep location was larger than that at high current density. This result implied that at low current density the reverse pulse played a strong suppression effect that contributed to the "V" shape growth. A competitive growth model between the bottom reversed "V" structure and the upper "V" structure was proposed to explain the void-free filling mechanism in PPR plating process. © 2014 The Electrochemical Society. All rights reserved.

Morikawa Y.,ULVAC Inc. | Morikawa Y.,NMEMS Technology Research Organization | Sakuishi T.,ULVAC Inc. | Sakuishi T.,NMEMS Technology Research Organization | Suu K.,ULVAC Inc.
46th International Symposium on Microelectronics, IMAPS 2013 | Year: 2013

"2.5D silicon interposers" and "Hetero 3D stacked" technology for high-performance LSI are gathering the most attention from now on. These technologies can solve interconnection problems using TSV (Through Silicon Via) to electrically connect stacked each function devises. 2.5D and hetero-3D Si integration has great advantages over conventional 2D devices such as high packaging density, small wire length, high-speed operation, low power consumption, and high feasibility for parallel processing. But, the radical problem about the TSV production cost is not still solved. In particular, the demand to a new plating bath technology to shorten Cu plating time is expected. On the other hand, TSV isolation liner materials with lower cost for high frequency devices will be necessary in the future. "Scallop-free" etching process has developed for TSV fabrication [1]. As a result, the smooth-sidewall had proved shorten PVD process time [2]. At first, it investigated a cost correlation of taper-shape etching and Cu-ECP (electro-chemical plating) in this paper. And then, a polyurea film using a vapor deposition polymerization technology (which is Ulvac's FPF/PV large panel technology) tried introduction as isolation liner for next-generation high frequency device. And, it performed the film formation to a TSV pattern.

Tanaka J.,NMEMS Technology Research Organization | Imamoto H.,NMEMS Technology Research Organization | Seki T.,Omron Corporation | Oba M.,Omron Corporation
Proceedings of IEEE Sensors | Year: 2014

This paper describes the low power consumption wireless human detector which can monitor wide area. We have developed the S-shaped thermopile infrared sensor element by utilizing micro-electro-mechanical-systems (MEMS) technology. The developed thermopile infrared array sensor achieved high temperature resolution and fast response time. Number of human who exists in the detection area is simply detected by the human detection process using temperature outputs from the thermopile infrared array sensor. © 2014 IEEE.

Yamashita T.,NMEMS Technology Research Organization | Yamashita T.,Japan National Institute of Advanced Industrial Science and Technology | Zhang Y.,NMEMS Technology Research Organization | Zhang Y.,Japan National Institute of Advanced Industrial Science and Technology | And 6 more authors.
Proceedings of IEEE Sensors | Year: 2014

This paper presents a novel film based flexible clamp type current sensor for green wireless sensor networks fabricated by printed silver paste coil using the process technology in screen-printing as a low cost, simple, and rapid method. Since developed sensor has high flexibility, it can be used by winding the cable and drastically reduce the installation space. In addition, it can construct wireless sensor networks easily because wireless terminals can drive autonomously without external power supply by utilizing the secondary current generated in the coil of the sensor by electromagnetic induction. The sensor's output voltage changed linearly with variation of the value of primary current in the 0 to 100 A range. When the value of primary current was 100 A, the output voltage was 69 mV per 150 turns in the coil. Although the ambient temperature around the sensor was raised at 80°C due to heat evolved by the electric resistance of the coil, there was no almost variation of the voltage. This result indicates the practical applicability as the current sensor for electrical cables. © 2014 IEEE.

Shiraishi N.,NMEMS Technology Research Organization | Shiraishi N.,Tokyo University of Agriculture and Technology | Kimura M.,NMEMS Technology Research Organization | Kimura M.,Shinshu University | And 2 more authors.
Microelectronic Engineering | Year: 2014

We have developed and evaluated a PMMA-based gas sensor to realize a low-cost sensor network system for monitoring VOCs (volatile organic compounds). The PMMA-based gas sensor consists of a PMMA (poly methyl methacrylate) cantilever, a piezoelectric film of PVDF (polyvinylidene fluoride), and a thin film of PBD (polybutadiene). We began by investigating the influence of PBD coating of a dynamic property of the PMMA cantilever in a higher order resonance mode under atmospheric pressure at room temperature. The PBD-coated PMMA cantilever had a resonant frequency of 341 kHz and quality factor of 71 at the 4th flexural vibration mode. Next, we examined the change of resonance frequency in the presence of toluene vapor by setting up a gas sensor evaluation system equipped with a VOC dilution flow system, temperature-controlled chamber, oscillation circuit, and frequency counter. The resonant frequency shifted when the PMMA-based gas sensor was exposed to toluene vapor. The measured toluene sensitivity in the experiment was 0.02 Hz/ppm. © 2014 Elsevier B.V. All rights reserved.

Tomimatsu Y.,NMEMS Technology Research Organization | Takahashi H.,University of Tokyo | Kobayashi T.,Japan National Institute of Advanced Industrial Science and Technology | Matsumoto K.,University of Tokyo | And 3 more authors.
Proceedings of the 2013 IEEE 8th International Conference on Intelligent Sensors, Sensor Networks and Information Processing: Sensing the Future, ISSNIP 2013 | Year: 2013

This paper reports a wake-up switch using a piezoelectric differential pressure sensor in order to reduce the power consumption of a wireless sensor node. Air pressure change surrounding the sensor is detected by using a Pb(Zr, Ti)O3(PZT) thin film cantilever with the dimension of 1500 μm × 1000 μm × 2 μm. The sensor has high sensitivity with low power consumption due to its thin cantilever and low capacitance. The sensitivity was 2.4 mV/Pa from -30 Pa to 30 Pa. It was demonstrated that the fabricated sensor performed as a wake-up switch when pressure varies in 10 Pa with low power consumption. © 2013 IEEE.

Shiraishi N.,NMEMS Technology Research Organization | Shiraishi N.,Tokyo University of Agriculture and Technology | Ikehara T.,NMEMS Technology Research Organization | Ikehara T.,Japan National Institute of Advanced Industrial Science and Technology | And 5 more authors.
Sensors and Actuators, A: Physical | Year: 2013

We investigated the size and mode dependencies of the resonance frequencies and quality factors of PMMA (polymethyl methacrylate) and PC (polycarbonate) cantilevers under atmospheric pressure in order to obtain fundamental data for polymer-based VOC (volatile organic compound) sensors. PMMA cantilevers and PC cantilevers are fabricated by hot embossing, bonding, and polishing techniques. Variations in the vibration mode result in large variations in the resonance frequencies and quality factors of these cantilevers. The measured resonance frequencies correlated well with the theoretical undamped resonance frequency of a flexural-vibrating cantilever. The measured quality factors varied from 10 to more than 100, depending on the vibration mode. A higher mode tended to exhibit a higher quality factor. © 2013 Elsevier B.V.

Lu J.,Japan National Institute of Advanced Industrial Science and Technology | Okada H.,Japan National Institute of Advanced Industrial Science and Technology | Itoh T.,Japan National Institute of Advanced Industrial Science and Technology | Harada T.,NMEMS Technology Research Organization | Maeda R.,Japan National Institute of Advanced Industrial Science and Technology
IEEE Sensors Journal | Year: 2014

Pursuit of the lowest size-limit of wireless sensor nodes may not only reduce power consumption and production cost, but also enables its layout-free ubiquitous applications, i.e., in our green sensor networks to compress energy consumption through visibility and optimization. In this paper, we engaged in developing the world smallest wireless sensor node with ultralow power consumption from both electrical block integration and physical interconnection points-of-view. A customized IC for signal processing and data transmission, which has universal interface to sensors and power management capability, was designed and then fabricated by using 0.18 μm 1.8 V/3.3 V 1P6M logic process. By introducing buried bump interconnection technology, we have successfully obtained one of the world's smallest wireless sensor nodes, as small as 3.9 mm × 3.9 mm × 3.5 mm, for humidity and temperature monitoring. The sensor node also features an general purpose interface, available for analog and digital sensors, and the ultrasmall footprint of above sensor node enables its layout-free distribution or integration inside other remote sensing systems. Although the adopted antenna size was 2 cm × 5 cm, its flexibility enables free attach to any curved surfaces. Experimental results demonstrated that besides preferred ultralow power consumption and data transmission distance, configuration of above sensor nodes enables its easy assembly with stand-alone power source and flexible antenna for wide variety of applications. © 2001-2012 IEEE.

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