Prof. Nobuyoshi Koshida Profile

Prof. Nobuyoshi Koshida

Professor of Electronic Device Engineering at Tokyo Univ of Agriculture and Technology

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Author

Publications (13)

Proceedings Article | 27 June 2019 Paper

Development of massive parallel electron beam write system

Masayoshi Esashi, Hiroshi Miyaguchi, Akira Kojima, Naokatsu Ikegami, Nobuyoshi Koshida, Masanori Sugata, Hideyuki Ohyi

Proceedings Volume 11178, 111780B (2019) https://doi.org/10.1117/12.2532971

KEYWORDS: Electron beams, Prototyping, Photomasks, Electron beam lithography, Lithography, Optical systems, Optical fabrication, Display drivers, Silicon, Electrodes

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Proceedings Article | 21 March 2017 Presentation + Paper

Simulation analysis of a miniaturized electron optics of the massively parallel electron-beam direct-write (MPEBDW) for multi-column system

Akira Kojima, Naokatsu Ikegami, Hiroshi Miyaguchi, Takashi Yoshida, Ryutaro Suda, Shinya Yoshida, Masanori Muroyama, Kentaro Totsu, Masayoshi Esashi, Nobuyoshi Koshida

Proceedings Volume 10144, 101440L (2017) https://doi.org/10.1117/12.2257967

KEYWORDS: Electron beams, Objectives, Monochromatic aberrations, Finite element methods, Optical simulations, Silicon, Electrodes, Optical design, Prototyping, Geometrical optics, Lens design, Aberration correction, Distortion

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In this study, a simulation analysis of a miniaturized electron optics for the Multi-Column Massively Parallel Electron Beam Writing system is demonstrated. Analytical evaluation of space charge effect with prototype Massively Parallel Electron Beam Writing (MPEBW) system showed 2.86 nm blur in radius occurs on each beam with a convergence half angle of 3 mrad. The angle of each beam was increased to 10 mrad to reduce the space charge effect, the coulomb blur amount can be kept to less than 1 nm in radius. However, there was limitation to increasing the angle due to a spherical aberration. Since the beam current density from the electron emitter array in the prototype MPEBW system was 100 μA/cm²and the total beam current was 1μA with 100×100 array of 10μm square emitter, the influence of coulomb blur was small. By contrast, considerably increasing the number of beams and the beam current are planned in near future in MPEBW. The coulomb blur and other aberrations will not be controlled by merely adjusting the beam convergence angle. In order to increase total beam current, miniaturized electron optics have been designed for Multi-beam+Multi-column system. Reduction lens in the designed miniaturized electron optics with crossover free to reduce the influence of coulomb repulsion with narrow convergence half angle. Unlike conventional methods, the electron beams as principal rays do not intersect at one point, so even if the beam becomes extremely narrow, the coulomb repulsion effect does not increase at the crossover area. The reduction of the entire size of parallel beams in the designed electron optics was confirmed by simulation software. The simulation results showed that least confusion disk of 6.5 nm size was obtained at the beam convergence half angles of 3 mrad corresponding to the incident beam of ±0.1 mrad divergence angle. It showed that the miniaturized electron optics was suitable for 10 nm order EB writing. The crossover free electron optics of the miniaturized electron optics is possible due to dispersing the intersection points of the principal rays by a combination of a concentric electron optics and a tapered lens electrode of the reduction lens.

Proceedings Article | 22 March 2016 Paper

Development of a MEMS electrostatic condenser lens array for nc-Si surface electron emitters of the Massive Parallel Electron Beam Direct-Write system

A. Kojima, N. Ikegami, T. Yoshida, H. Miyaguchi, M. Muroyama, S. Yoshida, K. Totsu, N. Koshida, M. Esashi

Proceedings Volume 9777, 977712 (2016) https://doi.org/10.1117/12.2219338

KEYWORDS: Electron beams, Microelectromechanical systems, Electron beam lithography, Lithography, Silicon, Finite element methods, Optical simulations, Nanolithography, Prototyping, Optical systems, Electrodes, Objectives, Semiconducting wafers

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SPIE Journal Paper | 11 September 2015

Development of ballistic hot electron emitter and its applications to parallel processing: active-matrix massive direct-write lithography in vacuum and thin-film deposition in solutions

Nobuyoshi Koshida, Akira Kojima, Naokatsu Ikegami, Ryutaro Suda, Mamiko Yagi, Junichi Shirakashi, Hiroshi Miyaguchi, Masanori Muroyama, Shinya Yoshida, Kentaro Totsu, Masayoshi Esashi

JM3, Vol. 14, Issue 03, 031215, (September 2015) https://doi.org/10.1117/12.10.1117/1.JMM.14.3.031215

KEYWORDS: Silicon, Electrodes, Thin film deposition, Thin films, Lithography, Germanium, Metals, Printing, Semiconducting wafers, Copper

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Proceedings Article | 19 March 2015 Paper

Development of ballistic hot electron emitter and its applications to parallel processing: active-matrix massive direct-write lithography in vacuum and thin films deposition in solutions

N. Koshida, A. Kojima, N. Ikegami, R. Suda, M. Yagi, J. Shirakashi, T. Yoshida, Hiroshi Miyaguchi, Masanori Muroyama, H. Nishino, S. Yoshida, M. Sugata, Kentaro Totsu, M. Esashi

Proceedings Volume 9423, 942313 (2015) https://doi.org/10.1117/12.2085782

KEYWORDS: Silicon, Thin film deposition, Electrodes, Thin films, Lithography, Metals, Germanium, Semiconductors, Parallel processing, Ions

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Making the best use of the characteristic features in nanocrystalline Si (nc-Si) ballistic hot electron source, the alternative lithographic technology is presented based on the two approaches: physical excitation in vacuum and chemical reduction in solutions. The nc-Si cold cathode is a kind of metal-insulator-semiconductor (MIS) diode, composed of a thin metal film, an nc-Si layer, an n⁺-Si substrate, and an ohmic back contact. Under a biased condition, energetic electrons are uniformly and directionally emitted through the thin surface electrodes. In vacuum, this emitter is available for active-matrix drive massive parallel lithography. Arrayed 100×100 emitters (each size: 10×10 μm², pitch: 100 μm) are fabricated on silicon substrate by conventional planar process, and then every emitter is bonded with integrated complementary metal-oxide-semiconductor (CMOS) driver using through-silicon-via (TSV) interconnect technology. Electron multi-beams emitted from selected devices are focused by a micro-electro-mechanical system (MEMS) condenser lens array and introduced into an accelerating system with a demagnification factor of 100. The electron accelerating voltage is 5 kV. The designed size of each beam landing on the target is 10×10 nm² in square. Here we discuss the fabrication process of the emitter array with TSV holes, implementation of integrated ctive-matrix driver circuit, the bonding of these components, the construction of electron optics, and the overall operation in the exposure system including the correction of possible aberrations. The experimental results of this mask-less parallel pattern transfer are shown in terms of simple 1:1 projection and parallel lithography under an active-matrix drive scheme.

Another application is the use of this emitter as an active electrode supplying highly reducing electrons into solutions. A very small amount of metal-salt solutions is dripped onto the nc-Si emitter surface, and the emitter is driven without using any counter electrodes. After the emitter operation, thin metal (Cu, Ni, Co, and so on) and elemental semiconductors (Si and Ge) films are uniformly deposited on the emitting surface. Spectroscopic surface and compositional analyses indicate that there are no significant contaminations in deposited thin films. The implication is that ballistic hot electrons injected into solutions with appropriate kinetic energies induce preferential reduction of positive ions in solutions with no by-products followed by atom migration, nuclei formation, and the subsequent thin film growth. The availability of this technique for depositing thin SiGe films is also demonstrated by using a mixture solution. When patterned fine emission windows are formed on the emitter surface, metal and semiconductor wires array are directly deposited in parallel.

Proceedings Article | 28 March 2014 Paper

Massively parallel electron beam direct writing (MPEBDW) system based on micro-electro-mechanical system (MEMS)/nanocrystalineSi emitter array

A. Kojima, N. Ikegami, T. Yoshida, H. Miyaguchi, M. Muroyama, H. Nishino, S. Yoshida, M. Sugata, H. Ohyi, N. Koshida, M. Esashi

Proceedings Volume 9049, 904918 (2014) https://doi.org/10.1117/12.2046584

KEYWORDS: Electron beams, Lithography, Electrodes, Semiconducting wafers, Microelectromechanical systems, Silicon, Scanning electron microscopy, Monochromatic aberrations, Copper, Objectives

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Proceedings Article | 26 March 2013 Paper

Development of maskless electron-beam lithography using nc-Si electron-emitter array

A. Kojima, N. Ikegami, T. Yoshida, H. Miyaguchi, M. Muroyama, H. Nishino, S. Yoshida, M. Sugata, S. Cakir, H. Ohyi, N. Koshida, M. Esashi

Proceedings Volume 8680, 86800I (2013) https://doi.org/10.1117/12.2011553

KEYWORDS: Semiconducting wafers, Silicon, Electrodes, Lithography, Electron beams, Electron beam lithography, Microelectromechanical systems, Binary data, Prototyping, Nanowires

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This study demonstrated our prototyped Micro Electro Mechanical System (MEMS) electron emitter which is a nc-Si (nanocrystalline silicon) ballistic electron emitter array integrated with an active-matrix driving LSI for high-speed Massively Parallel Electron Beam Direct Writing (MPEBDW) system. The MPEBDW system consists of the multi-column, and each column provides multi-beam. Each column consists of emitter array, a MEMS condenser lens array, an MEMS anode array, a stigmator, three-stage deflectors to align and to scan the multi beams, and a reduction lens as an objective lens. The emitter array generates 100x100 electron beams with binary patterns. The pattern exposed on a target is stored in one of the duplicate memories in the active matrix LSI. After the emission, each electron beam is condensed into narrow beam in parallel to the axis of electron optics of the system with the condenser lens array. The electrons of the beams are accelerated and pass through the anode array. The stigmator and deflectors make fine adjustments to the position of the beams. The reduction lens in the final stage focuses all parallel beams on the surface of the target wafer. The lens reduces the electron image to 1%-10% in size. Electron source in this system is nc-Si ballistic surface electron emitter. The characteristics of the emitter of 1:1 projection of e-beam have been demonstrated in our previous work. We developed a Crestec Surface Electron emission Lithography (CSEL) for mass production of semiconductor devices. CSEL system is 1:1 electron projection lithography using surface electron emitter. In first report, we confirmed that a test bench of CSEL resolved below 30 nm pattern over 0.2 um square area. Practical resolution of the system is limited by the chromatic aberration. We also demonstrated the CSEL system exposed deep sub-micron pattern over full-field for practical use. As an interim report of our development of MPEBDW system, we evaluated characteristics of the emitter array integrated with an active-matrix driving LSI on the CSEL system in this study. The results of its performance as an electron source for massively parallel operation are described. The CSEL as an experimental set consisted of the emitter array and a stage as a collector electrode that is parallel to the surface of the emitters. An accelerating voltage of about -5 kV was applied to the surface of the emitter array with respect to the collector. The target wafer and the emitter array were set between two magnets. The two magnets generated vertical magnetic field of 0.5 T to the surface of the target wafer. A gap between the emitter array and the target wafer was adjusted to a focus length depending on electron trajectories in the electromagnetic field in the system. The emitter array projected 100x100 electron beams with binary patterns and a dots image of its original size on the target wafer. The certain array was examined in order to evaluate the property of the e-beam exposure.

SPIE Journal Paper | 9 August 2012 Open Access

Active-matrix nanocrystalline Si electron emitter array for massively parallel direct-write electron-beam system: first results of the performance evaluation

Naokatsu Ikegami, Nobuyoshi Koshida, Takashi Yoshida, Masayoshi Esashi, Akira Kojima, Hideyuki Ohyi

JM3, Vol. 11, Issue 3, 031406, (August 2012) https://doi.org/10.1117/12.10.1117/1.JMM.11.3.031406

KEYWORDS: Silicon, Prototyping, Electrodes, Semiconducting wafers, Photomasks, Lenses, Scanning electron microscopy, Raster graphics, Gold, Electron beams

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Proceedings Article | 21 March 2012 Paper

Active-matrix nc-Si electron emitter array for massively parallel direct-write electron-beam system

N. Ikegami, T. Yoshida, A. Kojima, H. Ohyi, N. Koshida, M. Esashi

Proceedings Volume 8323, 832312 (2012) https://doi.org/10.1117/12.916250

KEYWORDS: Silicon, Prototyping, Electrodes, Lenses, Semiconducting wafers, Raster graphics, Photomasks, Structural design, Scanning electron microscopy, Nanowires

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Proceedings Article | 4 April 2011 Paper

Fast and large-field electron-beam exposure by CSEL

A. Kojima, T. Ohta, H. Ohyi, N. Koshida

Proceedings Volume 7970, 79701R (2011) https://doi.org/10.1117/12.879279

KEYWORDS: Silicon, Semiconducting wafers, Electrodes, Lithography, Chromatic aberrations, Prototyping, Photomasks, Electron beam lithography, Imaging systems, Nanowires

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We have developed a Crestec Surface Electron emission Lithography (CSEL) for mass production of semiconductor devices. CSEL system is 1:1 electron projection lithography using surface electron emitter. In first report, we confirmed that a test bench of CSEL resolved below 30 nm pattern over 0.2 um square area. Practical resolution of the system is limited by the chromatic aberration. We improved the resolution of the prototype CSEL system by reducing the initial energy spread of electrons and/or by increasing the electric field intensity. An energy spread of emitted electrons of a nanosilicon planar ballistic electron emitter (PBE) is very small. After that, the prototype CSEL system exposed sub-micron patterns distributed over 3 mm square area in last report. In this study, we examine the prototype CSEL system exposed deep sub-micron pattern over full-field for practical use. The experimental column of the system is composed of the PBE and a stage as a collector electrode that is parallel to the electron source. An accelerating voltage of about -5 kV is applied to the electron source with respect to the collector. The target wafer and PBE are set between two magnets. The two magnets generate vertical magnetic field of 0.5 T to the surface of the target wafer. A gap between the electron source and the target wafer is adjusted to a focus length depending on electron trajectories in the electromagnetic field in the system. The electron source projects a patterned electron image on the target since the patterned mask was formed on the surface electrode of the electron source. The electrons are emitted from openings of the mask. When a pulsed bias voltage is applied to the electron source, the electron source emits a patterned surface electron beam. The beam strikes the resist film coated on the target wafer and make replica of the pattern. We indicate the system exposes line patterns of about 200 nm in width over large area. An advantage of CSEL is high resolution due to small chromatic aberration, and another advantage is potentially high throughput because the coulomb blur is small without any crossover in the electron optics. When we get sufficient current from the electron source the throughput can be more than 100 wafers/hour.

Proceedings Article | 3 April 2010 Paper

Surface electron emission lithography system based on a planar type Si nanowire array ballistic electron source

A. Kojima, T. Ohta, H. Ohyi, N. Koshida

Proceedings Volume 7637, 763712 (2010) https://doi.org/10.1117/12.846343

KEYWORDS: Silicon, Electrodes, Lithography, Semiconducting wafers, Metals, Prototyping, Photomasks, Semiconductors, Phonons, Nanowires

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In this paper we report on the development of a Surface Electron Emission Lithography system (SEL) for high resolution and high throughput Electron Beam (EB) lithography. The Parallel EB lithography is performed on a 1:1 prototype electron stepper. A planar type silicon nanowire array ballistic electron emitter (PBE) is employed as a patterned electron emitting mask in this system. The PBE has a metal / silicon nanowire array / semiconductor structure. The nanowire is composed of interconnected silicon nanocrystallites. When a bias voltage is applied to the nanowire, the electrons injected from semiconductor substrate are accelerated via cascade tunneling between silicon nanocrystallites, and emitted from metal surface electrode. The PBE exhibits properties originated from the ballistic transport in nanosilicon layer. The electrons are emitted with uniform intensity in the surface. The emission current is fluctuation-free and low sensitivity against an environmental atomosphere. The PBE projects the pattern on the target wafer in the electron optics of parallel electric and magnetic fields. If all emitted electrons have same initial velocity, they are focused at the same distance. The pattern of the mask on the PBE is reproduced on the target wafer at the distance of the n (n=1, 2, ...) cycle of the spiral trajectory of the electron. Practical resolution is limited by the chromatic aberration in this system. We can improve the resolution by reducing the initial energy spread and emission angle dispersion of the emitted electrons because of the characteristics of the ballistic electron emission from PBE. In this study, we confirmed that the submicron patterns is reproduced all over the area of 2.8 mm square. This homogeneity of exposure in the extended area results from the uniformity of nanowire array produced by self-organized chemical reaction process. This technique will be available to produce next generation MEMS with lower cost than that of optical stepper.

Proceedings Article | 18 March 2009 Paper

Sub-30-nm resolution parallel EB lithography based on a planar type Si nanowire array ballistic electron source

A. Kojima, H. Ohyi, N. Koshida

Proceedings Volume 7271, 72712N (2009) https://doi.org/10.1117/12.812933

KEYWORDS: Silicon, Lithography, Electrodes, Projection systems, Semiconducting wafers, Photomasks, Chromatic aberrations, Electron beam lithography, Magnetism, Nanowires

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Proceedings Article | 10 September 2007 Paper

N. Koshida, B. Gelloz

Proceedings Volume 6775, 67750N (2007) https://doi.org/10.1117/12.732812

KEYWORDS: Silicon, Electroluminescence, Ultrasonics, Photonic devices, Acoustics, Picosecond phenomena, Luminescence, Quantum efficiency, Excitons, Ultrasonography

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