Akira Nakada

Development of nano-surgery system for cell organelles

A nano-surgery system has been developed for operation of minute organelles in a cell. such as chloroplast and mitochondria. For the operation, nano-pipettes, nano-manipulators, sample stage, and bellows pump were fabricated. It has been succeeded to prick a chromosphere in a plant cell and the membrane just under the nucleus of an animal cell with the tip of nano-pipette and to inject fluorescent dye into these organelles.

Wear reduction method for frictionally fast feeding piezoactuator

A new wear reduction method, which is based on a static friction without slipping, is developed for a frictionally fast feeding piezoactuator. This method is required for overcoming the problems related to the scattering of particles due to the use of a contact type actuator. Furthermore, wear reduction result in a frictionally driving actuator with a long-term stability for various applications, such as the electron beam inspection in the next-generation semiconductor industry.

Functional demonstration of the ability of a primary spermatogonium as a stem cell by tracing a single cell destiny in Xenopus laevis

In Xenopus, although primary spermatogonium (PG), the largest cell in the testis, is believed to be spermatogonial stem cell by histological observations, functional evidence has never been obtained. In the present study, we first indicated that culture of juvenile testis in a medium supplemented with follicle stimulating hormone resulted in no proliferation of PG. In this culture system, early secondary spermatogonia could undergo mitotic divisions with a concomitant decrease in their size, so that they became distinguishable in size from PG. Because the subcutaneous environment of juveniles permitted aggregates of the dissociated testicular cells to reconstruct the normal testis structure, we next inserted a genetically marked PG isolated from cultured testes into the aggregate and transplanted it subcutaneously. In this system, 73.9% of the aggregates contained a marked PG. When we observed the aggregates 12 weeks after transplantation, most aggregates (70.0%) contained marked PG that had self‐renewed. Among these, fully growing aggregates contained many spermatogenic cells at the later developmental stage. These results suggested that isolated PG from the cultured testes had the ability as stem cells, and that purification of the spermatogenic stem cells became reliable in Xenopus.

Highly Reliable Piezoelectric Actuator for Precision Stage System

A highly reliable nonresonant ultrasonic motor (NRUSM) made of cylindrical piezoelectric material is proposed in this paper. The high reliability is characterized by long lifetime and no outer gas in the vacuum environment, which are ensured by not using stack adhesives as the source of the gas emission. Positioning and tracking accuracy was better than below ±2 nm. The structural design is discussed in terms of the application to a high-speed high-precision stage system which has stable response to frequent biases without interference from resonant phenomena and the required mechanical strength.

Arbitrary pattern fabrication with a LCD reticle-free exposure method

We describe a newly developed technique that uses optical projection lithography with a liquid crystal display (LCD) in place of a conventional reticle, in order to minimize turn-around-time and production cost. Circuit pattern data, generated by a computer aided design (CAD) system, is transferred directly to a control computer. The control computer converts the data into an equivalent dot matrix representation of the design for use on a LCD. The LCD is placed in a conventional optical stepper. One feature of this system is the simplicity of the data management scheme which permits the data to be handled by a computer file directly; without any of the manual assistance normally needed in conventional reticle fabrication. It is a very convenient method to reverse reticle tone by changing the LCD mode; easy compared to a conventional reticle manufacturing process. The minimum resolution of this proposed system is very similar to conventional systems that use optical reticles. We have demonstrated that this LCD Reticle-Free Exposure Method has the potential of replacing conventional reticles in optical stepper lithography. This method is applicable for manufacturing devices with relatively large fabrication rules and low production quantities, such as System-in-Package applications.

Development of reticle-free exposure method with LCD projection image

Liquid crystal display (LCD) in place of the conventional reticles for optical projection lithography is proposed, in order to minimize the turn-around-time and production cost. The transmittance ratio between the two modes of the LCD, such as transparent and opaque ones, is approximately a several dozen depending on the wave length of the light source. In this study, the Nikon g-line stepper was modified to apply the LCD on its reticle stage. The minimum resolution of this proposal projection system is quite similar to the one of the conventional reticle method. The exposure time is approximately 10 times longer compared to the conventional method. It has been proven that the LCD has the potential to be replaced for the conventional reticles in the optical stepper lithography that is applicable for devices with relatively large fabrication rules and low production amount.

Slip-Free Driving Method for Nonresonant Piezoelectric Actuator

It is generally considered that in the ultrasonic motor the motion always slips and scratches. The nonresonant ultrasonic motor (NRUSM) expected for future precision stage systems should, however, overcome the difficulties of the wear of friction materials, which has been encountered in the use of conventional ultrasonic motors. The wear occurs by slipping and may be reduced by material selection. In this paper, we focus on the control method at actuation to prevent slipping. The advantages of NRUSM in the ability to control the drive frequency as well as the drive amplitude are shown, and this is effective in reducing wear and obtaining long-term stability. The drive frequency condition for no slippage under sinusoidal waveforms was calculated. The experimental results correspond to the theoretical calculated drive frequency. Because the resultant values of the frequencies are low for practical applications, we present the slip-free actuation method of using the new actuators driving waveform and time chart in order to drive the stage at constant accelerated motion.

Development of QTAT online electronic circuit patterning system

An arbitrary pattern exposure system has been developed by employing a liquid crystal display (LCD) with 1600 /spl times/ 1200 pixels for the formation of projection images in place of a conventional reticle. The minimum pattern size becomes 11.5 /spl mu/m, which corresponds to the aperture size of each pixel on the LCD. For the purpose of quick turnaround time (TAT), the exposure system was directly connected to the circuit design system with the transmission control protocol/internet protocol network. From the experimental results on patterning of a typical electronic circuit data with the area of 46/spl times/ 46 mm, it was confirmed that the TAT from the output of design data to the finish of the exposure becomes less than 28 min. By using this system, reduction of the production cost in the printed wiring boards fabrication is expected.

Development of nonresonant ultrasonic motor with sub-nanometer resolution

Precise positioning, which is the base technology for ultra-precise treatments, is highly essential in semiconductor LSI circuits, bio-cells, molecular sensors, and quantum devices. Conflicting performances, high-speed, long-stroke, and high-resolution have been achieved by using die nonresonant ultrasonic motor (NRUSM) controlled under the piezoelectric effect. One of the notable features of the NRUSM is do the frequency of the driving voltage can be varied in a wide range, which means the motion control of the NRUSM can be done by both the amplitude and frequency The maximum stage feed velocity is 140 mm/s with average acceleration of 2200 mm/s/sup 2/ in the 100 mm stroke under open-loop control. 100 nm step response with /spl plusmn/0.69 nm positioning accuracy is completed in 0.35 s under closed-loop control.

Development of vacuum environment compatible nano-probe system

In VLSI manufacturing, increase in the level of integration and functional improvement are essential. In order to achieve these objectives, semiconductor manufacturers are beginning to establish sub-0.1 /spl mu/m micro fabrication technologies. On the other hand, it is also necessary to compose the electrodes for operation tests of the VLSI. However, the size of electrodes available for such applications are currently on the order of 50*50 - 100* 100 /spl mu/m, which is a serious problem which must be overcome to accomplish the above-mentioned improvements in VLSI manufacturing. We have developed a new probe of which the tip diameter is 1 /spl mu/m or less. Also, we have succeeded in developing a new system that incorporates four sets of manipulators, which can accommodate the new probe and direct it to a desired location by observation with high resolution using a SEM (Scanning Electron Microscope).