Yoshio Mita

The University of Tokyo | Todai · Department of Electrical Engineering and Information Systems

Liquid-phase transmission electron microscopy (LP-TEM) can be used with an electrochemical chip (e-chip) to observe electrochemical reactions in a liquid in situ. The design of electrodes on an e-chip fabricated using microelectromechanical system (MEMS) technology cannot be easily changed. Here, we report a newly designed e-chip and its fabricatio...

We have realized an infrared (IR) photodiode with silicon for the future beyond-VLSI photonics. Colloidal quantum dot (CQD) integration with Si is a simple process. We previously reported a PbS CQD/ZnO/Si hybrid IR photodiode. The device had an absorption peak at 1230 nm. To improve the quantum efficiency, we investigated the dose levels of Si subs...

We propose nonvolatile binary stable states based on microelectromechanical systems (MEMS). They may be used as MEMS memory, where the bistable memory is the buckling direction of a plate of a capacitor. The binary memory is switched by applying a voltage to the MEMS. Furthermore, we propose an Ising model by making a series of buckled MEMS. It is...

Investigating heterointerfaces with test structures is crucial for fabricating electronic and photonic devices. Recently, we proposed and developed a PbS colloidal quantum dot/ZnO/Si hybrid infrared detector for infrared-sensitive optoelectronic devices on silicon-based large-scale integrated circuits. The conventional circular transfer length meth...

Manufacturing of microsystems based on complex three-dimensional microstructures requires critical steps such as mass calibrations and integration process. However, such steps involve several manipulation steps which are not well controlled thus the fragile 3D microstructures could be damaged or destroyed. In this work, we have demonstrated an AFM...

We propose and demonstrate a drop-in test structure to visualize and measure the residual stress in the conformally deposited film. For reliable device process of microsystems (such as 3-D MEMS), the residual stress must be controlled through quantitative evaluation at each deposition step. A small drop-in test structure placed near the main sample...

Miniaturized mobile microrobots have opened new applications from biomedical to environmental fields. Among various types of microrobots, recent progress on highly performing planar type microrobots could offer a good compromise between the manufacturability and the functionality promising for practical applications. The remaining challenges are to...

Miniaturized and mobile liquid handling devices are essential elements to biological or clinical applications. This will innovate the conventional liquid handling methods such as manual or automated pipetting systems. Here, we propose the micro fractal pipette as the candidate device for this objective. It is made of epoxy polymer and printed by in...

Circularly polarized light in the vacuum ultraviolet (VUV) region is important for probing the structural and electronic properties of matter. Moreover, a circularly polarized VUV coherent light enables one to observe the dynamics of biomolecules and electron spins in solids. The development of a table-top technology to directly generate circularly...

We have developed a neutron imaging sensor based on an INTPIX4-SOI pixelated silicon device. Neutron irradiation tests are performed at several neutron facilities to investigate sensor’s responses for neutrons. Detection efficiency is measured to be around 1.5% for thermal neutrons. Upper bound of spatial resolution is evaluated to be 4.1±0.2μm in...

We have developed a neutron imaging sensor based on an INTPIX4-SOI pixelated silicon device. Neutron irradiation tests are performed at several neutron facilities to investigate sensor's responses for neutrons. Detection efficiency is measured to be around $1.5$\% for thermal neutrons. Upper bound of spatial resolution is evaluated to be $4.1 \pm 0...

Tunable coherent light sources operating in the vacuum ultraviolet (VUV) region in the 100–200-nm (6–12 eV) wavelength range have important spectroscopic applications in many research fields, including time-resolved angle-resolved photoemission spectroscopy. Recent advances in laser technology have enabled the upconversion of visible femtosecond la...

We propose a drop-in test structure chip to evaluate residual stress. The structure was applied to evaluate supercritical fluid deposition (SCFD) Cu film over atomic layer deposition (ALD) Ru/TiO 2 film. In an early development stage of such emerging technology, researchers make experiments with a small sample chip in a small chamber. Small chips m...

An on-chip micro-mechanical test structure is presented to investigate the tribological behavior of deep reactive ion etching (DRIE) sidewall surfaces of microelectromechanical systems (MEMS) devices. The proposed test structure is fabricated on silicon on insulator (SOI) wafer using a standard surface micromachine process. Test structure consists...

Tunable femtosecond light sources operating in the vacuum ultraviolet (VUV) region in the 100-200 nm (6-12 eV) wavelength range are of crucial importance for VUV spectroscopy, including time-resolved angle-resolved photoemission spectroscopy (ARPES). Recent advances in laser technology have enabled upconversion of visible lasers to the vacuum and e...

This paper reports an area-selective supercritical fluid deposition (SCFD) of Cu with supercritical CO2 and H2 reductant. We demonstrated an area-selective Cu SCFD on TiN pre-patterned over a SiO2 underlayer on Si substrate. Atomic force microscopy and Auger electron spectroscopy were employed to characterize the fabricated samples. Several SCFD ex...

We demonstrate a simple and practical method for generating tunable coherent vacuum ultraviolet light with an adequate intensity for spectroscopic application such as ARPES based on third harmonic generation in dielectric free-standing nanomembranes.

Tin dioxide (SnO2) enables us to detect various low concentration gases for the application of environment monitoring and healthcare. Therefore, a great number of research and development has been carried out. However, relationships between surface responsivity and the other properties such as device structure and fine structure have not been compl...

The rapid development of microfluidic technology has increased the demand for the integration of driving circuits in the microfluidic devices. We have proposed a novel on-chip electroosmotic (EOF) micropump integrated with a high-voltage (HV) generator. The HV (49.8 V) generator is based on a Dickson charge pump, which is fabricated on a silicon-on...

Tin dioxide (SnO2) is a useful material in order to achieve the measurement of low concentration gases for various application such as application of environment monitoring and healthcare. Therefore, SnO2-based gas sensing device has been researched. In this study, basic characteristics of SnO2-based gas sensing device was evaluated for the highly...

In this article, we propose a device with multiple small pores, which are locally integrated with individual electrodes. The application is particle measurement using Coulter's method, using the integrated local electrode on each pore. Coulter's particle counter can achieve high resolution measurement; however, the method had sensitivity and throug...

This paper presents the design, modeling, fabrication, and testing of a MEMS passive shock sensor to record multiple threshold events with robust latching mechanism using mass-spring assembly. The latch- ing part on a seismic mass enables the discrete latch positions depending on the applied external impact forces and stores the impact value over a...

Ideal microrobots are on the millimeter-scale with integrated actuators, power sources, sensors, and controllers. Numerous researchers are inspired by insects for the mechanical or electrical design of microrobots. Previously, the authors proposed and demonstrated microrobots that can replicate the tripod gait locomotion of an ant, the legs of whic...

A surface-normal optical modulator using electro-optic polymer embedded inside a 570-nm-thick silicon high-contrast-grating resonator is fabricated. With a voltage applied to silicon grating, we obtain >20% intensity modulation of the transmitted light at 30 MHz.

To make high-selective and sensitive gas sensors, embedding zeolite particle to MEMS structures is studied. However, if the zeolite is aggregated, the zeolite structures become fragile and fall off from large MEMS structures. In this paper, we propose covering the aggregated zeolite particle embedded in micro-trenches with thin crystalline zeolite...

MEMS post-process is now used to develop the ability of an LSI chip. In this paper, increasing of breakdown voltage of a standard CMOS LSI chip is mainly remarked. Especially, MEMS post-processed transistors are described. The technology enables us to use standard CMOS foundry-made transistors on a silicon-on-insulator (SOI) wafer. The key fabricat...

Near-infrared detectors by silicon based devices with large scale integration are very attractive for secure applications about image sensors. Beyond the silicon bandgap, we focus on PbS colloidal quantum dots (CQDs) and silicon integration. In this paper, we investigated fabrication processes of PbS CQDs and silicon hybrid IR detector. Temperature...

We propose a gate-array style easy configuration method for voltage photovoltaic cell for rapid prototyping of on-chip IoT system. Using the same design chips fabricated by standard CMOS process and only changing the mask pattern for post processes, we successfully achieved two type chips: one generates 68 V open circuit voltage output photovoltaic...

A novel on-chip integrated high-voltage generator is realized by our unique MEMS post-processing method with the standard CMOS process on a silicon-on-insulator (SOI). Foundry-made charge-pump elements with standard 5-V transistors on an SOI are isolated with deep reactive ion etching (DRIE) and isotropic etching. This method facilitated the succes...

We demonstrate a new operation mode of thermal gas sensor based on thermal capacity extraction with identification algorithm. The system is a silicon microstructure covered with zeolites operated at constant temperature while stimulated by heat pseudo-random sequence. The proposed detection principle is demonstrated at room temperature and atmosphe...

We propose a compensated mesh pattern filling method to achieve highly uniform wafer depth etching (over hundreds of microns) with a large-area opening (over centimeter). The mesh opening diameter is gradually changed between the center and the edge of a large etching area. Using such a design, the etching depth distribution depending on sidewall d...

In this paper, we address issues and solutions for micro-electro-mechanical-systems (MEMS) powering through semiconductor devices towards one-chip MEMS, especially those with microactuators that require high voltage (HV, which is more than 10 V, and is often over 100 V) for operation. We experimentally and theoretically demonstrated that the main r...

This paper presents a versatile chip-level wireless driving method for microelectromechanical system (MEMS) actuators. A MEMS actuator is integrated as an electrical component of a coupled LCR resonant circuit, and it rectifies the energy sent through an ultrahigh-frequency (UHF) radio frequency (RF) wave. Two types of actuators were remotely drive...

In this paper, an on-chip micro-mechanical test structure has been developed to investigate the frictional behavior of Deep- RIE sidewall contacting surfaces of single crystal silicon which is most widely used in micromechanical systems (MEMS). The test structure is fabricated on Silicon on Insulator (SOI) wafer using standard MEMS process. Two ort...

Field-effect transistor (FET)-based biosensors have a wide range of applications, and a bio-FET odorant sensor, based on insect (Sf21) cells expressing insect odorant receptors (ORs) with sensitivity and selectivity, has emerged. To fully realize the practical application of bio-FET odorant sensors, knowledge of the cell–device interface for effici...

This paper presents a new and simple method to noninvasively localize failure sites in an insulated-gate bipolar transistor (IGBT) module by using a magnetic probe. The method detects the magnetic field generated by leakage currents occurring at the broken gates of an IGBT module. In this method, not only an RF stimulus signal but also a dc bias vo...

A 30 V switching circuit with standard CMOS foundry-made transistors on a silicon-on-insulator (SOI) wafer is proposed.The key fabrication process is mesa isolation postprocessing that physically separates a series-connected transistor’s body so that we can apply independent substrate (body) voltages to each transistor. The process is a combination...

Semiconductor Devices have been, and continue to be, the core of the information society. Together with tiny and inexpensive sensors, huge amounts of physical data will be collected in cyber-systems and analyzed by artificial intelligence. In such cyber-physical system, large-scale, low-power, and reliable semiconductor devices should be integrated...

Since the 2000s, several countries have established micro- and nanofabrication platforms for the research and education community as national projects. By combining such platforms with VLSI multichip foundry services, various integrated devices, referred to as "CMOS-MEMS", can be realized without constructing an entire cleanroom. In this paper, we...

Since 2001, the departments of Electrical and Electronics and Information and Communication Electronics Engineering of Faculty of Engineering, the University of Tokyo (UTokyo) have jointly given a lecture on autonomous electronic information devices for undergraduate students. According to the on-line questionnaire, 80% of students in 2010-2012 rep...

Test structures were developed to visualize the progress of the dry release of a MEMS device fabricated by deep reactive ion etching (DRIE). Because of the high aspect ratio of DRIE MEMS devices, the undercut progress cannot be observed from the surface. Therefore, a destructive test i.e., a cross-sectional-view observation of a cleaved sample, has...

SnO2 thin films were sputter onto the surface of a Si wafer with oxide on top of it. The piezoresistive properties of the thin films was measured. In order to attain larger, gauge factor, the films are annealed in oxygen atmosphere in different temperature. The gauge factor was measured to be around negative 1-2 without heat treatment, and was impr...

New concept of microfabricated thermal resonant gas sensor comprising of a cantilever-like thermal device covered with a selective zeolite layer associated to heat feedback electronics is presented. Sensing principle exploits the thermal resonant frequency shift caused by mass variations upon gas adsorption in the zeolite layer; the proof-of-concep...

We propose a high-voltage switch driven by wavelength-modulated light, which is suitable for remote MEMS (especially electrostatic actuators) device operation. It is fabricated on an SOI wafer and consists of series-connected n-MOSFETs whose substrates are mesa-isolated, allowing the switch to endure a high voltage. The fabrication process requires...

It has been reported that an object can be suspended below a vibrating surface in air. We call this phenomenon ultrasonic suspension. When an object is suspended, a restoring force attracts the object horizontally to the center of the vibrating surface. Previously, characteristics of the forces acting vertically and horizontally were experimentally...