Funding Program for Next Generation World-Leading Researchers (NEXT Program) granted by The Japan Society for the Promotion of Science (JSPS) initiated by The Council for Science and Technology Policy (CSTP)
Integrated MEMS Technology for Multi-functional Low Power Electronics
PI: Hiroshi Toshiyoshi, RCAST, The University of Tokyo
Integrated MEMS is a technology to assemble microscopic "machines" with electronic sensors and circuits by using the semiconductor micro fabrication technique. Integrated MEMS is expected to be an enabling power for the next generation high added value manufacturing technique as well as for the low power consumption technology. However, the R&Ds in the MEMS field are ensemble of vast wide range of case studies due to the lack of systematic design and production schemes. For this reason, this study focuses onto the standardization of the integrated MEMS such that we would have a technological perspective from the material level to the system.
FEM is a powerful tool for MEMS but is also difficult to co-solve with elecrical circuit for transient analysis due to a large number of data nodes. For this reason, we have newly developed a co-solving technique for integrated MEMS by using an equivalent circuit solve for the mechanical equatio of motion, which is now available from our homepage. Also, we have developed a version for Cadence Virtuoso, which is a defacto standard as a VLSI CAD.
Reference: T. Konishi, K. Machida, S. Maruyama, M. Mita, K. Masu, and H. Toshiyoshi, IEEE/ASME J. Microelectromech. Syst., vol. 22, no. 3, Jun. 2013, pp. 755-767.
As a multi-purpose process for integrated MEMS, we have developed a surface micromachining technique on a pre-fabricated LSI by using sputtered/electroplated metals. The process capability has been verified by demonstrating an electrostatic type power-gating switch that shuts down the unneeded electrical current flowing in an LSI. We also have demonstrated an RF-MEMS switch for wireless transmitters. Another demonstration has been made to prove an idea to use the MEMS electrostatic mechanism for logic operation such as NOT, NAND, NOR, XOR, and XNOR with a single cantilever beam.
Reference: M. Mita, M. Ataka, and H. Toshiyoshi, “Microelectromechanical XNOR and XOR logic devices,” IEICE Electronics Express, vol. 10, no. 8, 2013, pp. 1-12.
(This work was performed in collaboration with ISAS/JAXA.)
It would cost a lot if one place an order of VLSI wafer for himself. MEMS production facilities are also expensive to install. For these reasons, we used a wafer shuttle service operated by Japanese comapanies to share a wafer with plural users to save the cost. We also used the budget of this project to install the post-CMOS processing equipment in the lab such that our collaborator would share the MEMS processes.
Reference: NTT~AT (0.18, 0.35 and 0.6 um), VDEC Rohm (0.18 um), VDEC-Fenitec (0.6 um).
Cognitive wireless communication is a way to optimize the system (frequency, radiation patterns) by monitoring the traffic. In this work, we have developed a MEMS electrostatic tunable capacitor and used it in an 800 MHz band VCO (voltage Controlled Oscillator).
This work was performed in collaboration with Japan Radio Corporation.
Data: operation voltage 35V, capacitor range 0.55-0.73pF, control 1-4 bit, VCO quality factor 60, phase noise -101dBc/Hz.
Reference: K. Urayama, K. Akahori, N. Adachi, H. Fujita, and H. Toshiyoshi, "A Low Phase-Noise VCO for Multi-Band Transceiver using Fully Packaged MEMS Electrostatic Varactors," in Proc. 26th IEEE Int. Conf. on Micro Electro Mechanical Systems, Jan. 20-24, 2013, Taipei, Taiwan, pp. 737-740.
Application field of MEMS accelerometers would go beyond the smartphone hardware, and a lot of MEMS sensors would be used to monitor the events and persons to help our life. In this work, we have developed a MEMS accelerometer that could sense a wide range of acceleration including sub 1G to a few G's by using the integrated MEMS.
This work was performed in collaboration with NTT Advanced Technology Corporation and with Professor K. Masu's group with the Tokyo Institute of Technology.
Data: 0.35um CMOS, Vdd = 3.3V, acceleration range 0.5G - 6G, low Brownian noise of 11.7uG/Sqrt(Hz) due to high density material (plated gold).
Reference: T. Konishi, D. Yamane, T. Matsuhsima, K. Machida, K. Masu, and H. Toshiyoshi, "An arrayed accelerometer device of a wide range of detection for integrated CMOS-MEMS technology," Jpn. J. Appl. Phys., vol. 53, 027202, 2014, pp. 027202.1-027202.9.
A focus-less image projector can be constructed by using a MEMS optical scanner to spatially scan the collimated RGB beams from laser diodes. The identical optical can also be used as a laser range finder to measure the distance to the screen or to detect the object such as a user's hand inserted in front of the screen. We used this feature to create a new type of user-interactive display that could change the projected images by the viewer's physical motion.
This work was performed in collaboration with Stanley Electric Corporation.
Data: scanner drive voltage 40V, image VGA class, range 20-60cm, resolution 2cm.
Reference: Sungho Jeon, Hiroyuki Fujita, and Hiroshi Toshiyoshi, "A MEMS Interactive Laser Projection Display with a Built-in Laser Range Finder," in Proc. IEEE Int. Conf. on Optical MEMS and Nanophotonics (OMN 2013), Kanazawa, Japan, Aug. 18-22, 2013, pp. 21-22.
MEMS tunable light source is not limited to the optical fiber applications but also used in the medical field such as OCT (Optical Coherence Tomography). We have developed a fast optical MEMS scanner to sweep the wavelength of the OST system such that a motion picture can be captured.
This work was performed in collaboration with Santec Corporation.
Data: scanner operation voltage 70V, scanner resonance 70kHz, wavelength sweep 140kHz, center wavelength 1300nm, bandwidth 100nm, output power 20mW, OCT inspection depth 2mm, image resolution 5-10um, frame rate 50fps.
Reference: K. Isamoto, K. Totsuka, T. Sakai, T. Suzuki, A. Morosawa, C. Chong, H. Fujita, and H. Toshiyoshi, "High Speed MEMS Scanner Based Swept Source Laser for SS-OCT," IEEJ Trans. Sensors and Micromachines, vol. 132, no. 9, 2012, pp. 254-260. (in Japanese)
It is said that we will soon see a new era to produce a trillion of sensors a year for monitoring. This vast amount is equivalent to sensors distributed every 1 meter in the Tokyo downtown, considering the 13M population living in the 2,200km^2. Besides the MEMS sensor and wireless technologies, we will soon need a new scheme to supply energy to such small and many sensors without using wires or batteries.
Power consumption of VLSI is becoming smaller every year owing to the downsizing of the circuit patterns. New resource of power is also developed in the field of MEMS by harvesting from the natural vibrations such as winds and infrastructures. In addition to the work reported here, we also develop a new technique to integrate permanent electrical charge (electret) and to increase the capacity of the electrical energy storage. By year 2030, people might see a new world where the wireless sensor nodes of short distance (10 meters) are power-supplied by the MEMS energy harvesters.
This research is granted by the Japan Society for the Promotion of Science (JSPS) through the "Funding Program for Next Generation World-Leading Researchers (NEXT Program)," initiated by the Council for Science and Technology Policy (CSTP).