研究者詳細 - 原田　俊太

論文 - 原田　俊太

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Effects of proton implantation into 4H-SiC substrate: Stacking faults in epilayer on the substrate 査読有り

Masashi Kato, Ohga Watanabe, Shunta Harada, Hitoshi Sakane

Materials Science in Semiconductor Processing 175 巻頁： 108264 - 108264 2024年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science in Semiconductor Processing

This study explored proton implantation into 4H-SiC substrates to suppress the expansion of single Shockley stacking faults (SSSFs), which is a source of bipolar degradation in 4H-SiC devices. While previous research has demonstrated the effectiveness of proton implantation in epitaxial layers, concerns about defect generation have persisted. Therefore, we implanted protons into 4H-SiC substrates, followed by epitaxial growth. Then, we fabricate PiN diodes using the epitaxial layer aiming to reduce SSSF expansion and enhance PiN diode reliability. The results indicate that proton implantation has no significant suppression effects on the SSSF expansion, coupled with the undesired induction of double Shockley stacking faults. Thus, proton implantation into the substrates does not enhance the reliability of 4H-SiC devices, emphasizing the need for further investigations into suppression mechanisms.

DOI： 10.1016/j.mssp.2024.108264

Scopus

Analysis of Macrostep Interaction via Carbon Diffusion Field in SiC Solution Growth 査読有り

Nakanishi, Y; Kutsukake, K; Dang, YF; Harada, S; Tagawa, M; Ujihara, T

JOURNAL OF CRYSTAL GROWTH 631 巻頁： 127609 - 127609 2024年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Crystal Growth

In the top-seeded solution growth (TSSG) method for SiC, control of macrostep development is crucial for improving the crystal quality. Dislocation conversion phenomena caused by macrosteps with a certain height on the crystal surface can reduce the dislocation density, while over-developed macrosteps bring macroscopic defects such as solvent inclusions. It is experimentally reported that solution flow direction to the step movement has a substantial impact on the macrostep development: parallel solution flow promotes and anti-parallel solution flow suppresses the increase of macrostep height. Our hypothesis is that this macrostep development is governed by the interaction between the macrosteps not by the instability of the density of the atomical steps. In this study, we constructed a computational fluid dynamic model of the boundary layer around macrosteps on the crystal surface, incorporating the solution flow on the boundary layer and consumption of the carbon solute by the macrostep movement quantitatively. The computational simulation reveals that the macrostep with position shift from the center of the adjacent macrosteps moves to the direction of the nearer macrostep under the parallel flow and moves to the farther macrostep under the antiparallel flow. These macrostep movements result in the bunching and debunching of the macrosteps. The mechanisms of macrostep movements demonstrated in this study will be useful for the precise control of macrostep height aiming to the reduction of the dislocation density during SiC solution growth.

DOI： 10.1016/j.jcrysgro.2024.127609

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Accelerating X-ray photoemission spectroscopy measurements using Bayesian super-resolution

Harada, S; Tsujimori, K; Nomoto, T; Ito, T

JAPANESE JOURNAL OF APPLIED PHYSICS 63 巻 ( 4 ) 2024年4月

Effects of proton implantation for expansion of basal plane dislocations in SiC toward suppression of bipolar degradation: review and perspective 査読有り

Kato, M; Harada, S; Sakane, H

JAPANESE JOURNAL OF APPLIED PHYSICS 63 巻 ( 2 ) 頁： 020804 - 020804 2024年2月

Effect of Solution Components on Solvent Inclusion in SiC Solution Growth 査読有り

Zhou, HQ; Miura, H; Fukami, Y; Dang, YF; Kutsukake, K; Harada, S; Tagawa, M; Ujihara, T

CRYSTAL GROWTH & DESIGN 24 巻 ( 4 ) 頁： 1806 - 1817 2024年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Crystal Growth and Design

In the solution growth method of silicon carbide, cellular structures and solvent inclusions are fatal defects. This study investigates the mechanism of how cosolvent chromium and additive aluminum influence the formation of cellular structures and inclusions via numerical simulations based on a phase field model. The simulation results indicate that introducing chromium into the solution increases the growth rate of the SiC crystals. The uneven distribution of chromium components near the macrostep edge is prone to trigger constitutional supersaturation, ultimately leading to cellular structures and inclusions. Constitutional supersaturation is more pronounced in solutions with a higher viscosity. Additionally, a small amount of additive aluminum increases the interfacial energy, enhancing the step stability by raising the potential barrier for curved steps and moderating step slopes. Experimental results demonstrate that a solution containing 40% chromium can increase the growth rate by three times compared to a pure Si solution. The Si0.59-Cr0.4-Al0.01 solution emerges as a promising candidate, maintaining a high growth rate while preserving step stability and effectively suppressing the development of cellular structures and inclusions.

DOI： 10.1021/acs.cgd.3c01476

Web of Science

Scopus

DNA修飾ナノ粒子の結晶化とX線小角散乱による構造解析

田川美穂, 張力東, 小島憧子, 鷲見隼人, 横森真麻, 太田昇, 関口博史, 原田俊太, 宇治原徹

日本結晶学会誌 65 巻 ( Supplement ) 頁： s19 - s19 2023年10月

Non-destructive identification of edge-component burgers vector of threading dislocations in SiC wafers by birefringence imaging 査読有り

Harada, S; Matsubara, Y; Murayama, K

DIAMOND AND RELATED MATERIALS 138 巻 2023年10月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Diamond and Related Materials

Non-destructive characterization of crystalline defects in SiC wafers is important for manufacturing high-performance SiC power devices with high productivity. The present study shows that the edge component of the Burgers vector can be identified by birefringence imaging under conditions deviating slightly from the crossed-Nicols condition and by calculation of the in-plane shear stress distribution. It is also found that the combination of birefringence observation and X-ray topography allows the discrimination of the family of threading screw dislocations. The present results will further the understanding of the relationship between defect structure and the properties of SiC power devices.

DOI： 10.1016/j.diamond.2023.110192

Web of Science

Scopus

Machine Learning for Semiconductor Process Simulation Described by Coupled Partial Differential Equations 査読有り

Sato, R; Kutsukake, K; Harada, S; Tagawa, M; Ujihara, T

ADVANCED THEORY AND SIMULATIONS 6 巻 ( 9 ) 2023年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Advanced Theory and Simulations

Technology computer-aided design (TCAD) simulation is an important tool for the development of semiconductor devices. Based on coupled partial differential equations (PDEs) for behaviors, TCAD can calculate objects such as impurities, point defects, and electronic carriers in semiconductors. However, over recent years semiconductor devices have become increasingly miniaturized and complicated, resulting in much longer calculation times for TCAD. Machine learning is one technology that may be used to overcome this simulation cost problem. In this study, a neural network architecture is proposed that considers the structure of the coupled PDEs. Features representing each concentration distribution of the calculation objects are extracted by convolution operations and their reaction is modeled by channel attention. The performance of the proposed architecture and of conventional neural network models is evaluated using a simulation dataset generated by 1D coupled PDEs that models the diffusion and reaction of vacancies and interstitial atoms. In addition, the advantage of the method is discussed through the analyses of error correlations of the two predictions and attention coefficients. The machine learning method developed in this study will be applicable to other physics described by coupled PDEs and is expected to speed up the computation of simulations in various fields.

DOI： 10.1002/adts.202300218

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Scopus

Numerical Modeling of the Cellular Structure Formation Process in SiC Solution Growth for Suppression of Solvent Inclusions 査読有り

Zhou, HQ; Miura, H; Dang, YF; Fukami, Y; Takemoto, H; Harada, S; Tagawa, M; Ujihara, T

CRYSTAL GROWTH & DESIGN 23 巻 ( 5 ) 頁： 3393 - 3401 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Crystal Growth and Design

For the solution growth of silicon carbide, solvent inclusions are significant technological issues, and methods to suppress the formation of solvent inclusions are investigated in this study. Experimental observations show that solvent inclusions are formed behind the cellular structures. A phase field model is used to reproduce the formation process of cellular structures and solvent inclusions. Simulation results indicate that slight perturbations of the step front can convert into cellular structures in the case of insufficient supply of carbon, and the overdeveloped cellular structures consequently result in solvent inclusions. Accordingly, several schemes can be suggested by the simulation model to suppress the formation of cellular structures by enhancing the carbon supply. By increasing the carbon diffusion coefficient, cellular structures can be suppressed. Moreover, the step height and the solution flow direction also play an important role in suppressing the cellular structures. This study provides a comprehensive understanding of the formation process of cellular structures and solvent inclusions. A growth process with a high diffusion coefficient and opposite solution flow to the step flow direction was proposed to suppress the formation of cellular structures. The proposed numerical model could be applied in other solution crystal growth methods.

DOI： 10.1021/acs.cgd.2c01512

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Scopus

Development of High-Resolution Nuclear Emulsion Plates for Synchrotron X-Ray Topography Observation of Large-Size Semiconductor Wafers 査読有り

Harada, S; Nishigaki, T; Kitagawa, N; Ishiji, K; Hanada, K; Tanaka, A; Morishima, K

JOURNAL OF ELECTRONIC MATERIALS 52 巻 ( 5 ) 頁： 2951 - 2956 2023年5月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Electronic Materials

Characterization of defects in semiconductor wafers is essential for the development and improvement of semiconductor devices, especially power devices. X-ray topography (XRT) using synchrotron radiation is a powerful methods used for defect characterization. To achieve detailed characterization of large-size semiconductor wafers by synchrotron XRT, we have developed nuclear emulsion plates reaching a high-resolution and wide dynamic range. We have shown that higher-resolution XRT images could be obtained using emulsions with smaller iodobromide crystals, and demonstrated clear observation of threading edge dislocations in a SiC epitaxial layer having small contrast. Furthermore, we demonstrated XRT image acquisition for almost all of a 150-mm SiC wafer with one plate. Our development will contribute to advances in electronic materials, especially in the field of power electronics, in which defect characterization is important for improving the performance and yield of devices.

DOI： 10.1007/s11664-023-10270-8

Web of Science

Scopus

Fluorescence Turn-on of Tetraphenylethylene Derivative by Transfer from Cyclodextrin to Liposomes, HeLa Cells, and E. coli

Masuda K., Omokawa R., Kawasaki R., Mise Y., Ooyama Y., Harada S., Shinoda W., Ikeda A.

Chemistry - A European Journal 29 巻 ( 10 ) 2023年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemistry - A European Journal

Herein, trimethyl-β-cyclodextrin (TMe-β-CDx) and γ-cyclodextrin (γ-CDx) could dissolve a tetraphenylethylene derivative (TPE−OH4) in water through high-speed vibration milling. The fluorescence intensity of the TMe-β-CDx−TPE−OH4 complex was much higher than that of the γ-CDx−TPE−OH4 complex, as the rotation of the central C=C double bond of TPE−OH4 after photoactivation was inhibited in a smaller TMe-β-CDx cavity in comparison with the γ-CDx cavity. In contrast, the fluorescence intensity of the γ-CDx−TPE−OH4 complex was very weak; nevertheless, it increased after the addition of liposomes due to the transfer of TPE−OH4 from the γ-CDx cavity to the lipid membrane as a “turn-on” phenomenon. Furthermore, to apply temperature sensor, it was demonstrated that the fluorescence intensity in the liposomes depended on the phase-transition temperature. By using the fluorescence turn-on phenomenon, TPE−OH4 could detect the presence of HeLa cells and E. coli by fluorescence.

DOI： 10.1002/chem.202203071

Scopus

Fluorescence Turn-on of Tetraphenylethylene Derivative by Transfer from Cyclodextrin to Liposomes, HeLa Cells, and E. coli

Masuda, K; Omokawa, R; Kawasaki, R; Mise, Y; Ooyama, Y; Harada, S; Shinoda, W; Ikeda, A

CHEMISTRY-A EUROPEAN JOURNAL 29 巻 ( 10 ) 2023年2月

Thermal conduction in titanium-chromium oxide natural superlattices with an ordered arrangement of nearly pristine interfaces 査読有り

Sugimoto, S; Kim, G; Takeuchi, T; Tagawa, M; Ujihara, T; Harada, S

JOURNAL OF ALLOYS AND COMPOUNDS 934 巻頁： 167915 2023年2月

担当区分：最終著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Alloys and Compounds

Thermal conduction was investigated in titanium-chromium oxide natural superlattices with an ordered arrangement of crystallographic shear planes, which were nearly pristine interfaces for thermal phonons. Thermal conductivity exhibited a clear maximum value at around 50 K, which indicates interface roughness as small as 20 pm based on the calculation of thermal conductivity by a modified Debye-Callaway model. With an ordered arrangement of nearly pristine interfaces at nanoscale, the wave contribution to phonon transport was estimated to be predominant at lower temperatures (less than 100 K) and as much as 30 % even at room temperature. We found that the interface roughness greatly influences the thermal conduction in natural superlattice systems, which may lead to variations in the reported value of thermal conductivity. We have demonstrated that the wave contribution of thermal conductivity become apparent in bulk crystal having nano scale periodic structure with pristine interfaces.

DOI： 10.1016/j.jallcom.2022.167915

Web of Science

Scopus

Suppression of partial dislocation glide motion during contraction of stacking faults in SiC epitaxial layers by hydrogen ion implantation 査読有り

Harada, S; Sakane, H; Mii, T; Kato, M

APPLIED PHYSICS EXPRESS 16 巻 ( 2 ) 頁： 021001 2023年2月

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Applied Physics Express

Bipolar degradation in SiC bipolar devices, in which stacking faults (SFs) expand to accommodate the movement of partial dislocations during forward bias application, is one of the critical problems impeding the widespread implementation of SiC power devices. Here we clearly demonstrate that the movement of partial dislocations can be suppressed by proton implantation, which has good compatibility with semiconductor processing, through investigation of the contraction behavior of SFs in SiC epitaxial layers subjected to proton implantation.

DOI： 10.35848/1882-0786/acb585

Web of Science

Scopus

Modeling-Based Design of the Control Pattern for Uniform Macrostep Morphology in Solution Growth of SiC 査読有り

Dang, YF; Liu, XB; Zhu, C; Fukami, Y; Ma, SY; Zhou, HQ; Liu, X; Kutsukake, K; Harada, S; Ujihara, T

CRYSTAL GROWTH & DESIGN 23 巻 ( 2 ) 頁： 1023 - 1032 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Crystal Growth and Design

In the solution growth of the SiC crystal, macrosteps with sufficient height on an off-axis substrate are required to reduce defects and achieve a high-quality grown layer. However, over-developed macrosteps can induce new defects and adversely affect the crystal quality. To better understand and control the behavior of macrosteps corresponding to the control parameters of the growth system, a simulation method that consists of a global two-dimensional computational fluid dynamic (CFD) model, a local three-dimensional CFD model near the growth front, and a kinetics model that describes the movement of macrosteps on the crystal surface is proposed. The simulation method is first applied to investigate the effect of the crystal rotation speed on macrostep morphology. Although the results indicate that a higher crystal rotation speed results in less step bunching, constantly rotating the crystal in one direction is demonstrated to be incapable of yielding a uniform macrostep distribution on the whole surface. Accordingly, a sophisticated control pattern is designed by periodically switching the flow direction underneath the crystal surface, where the proposed simulation method is critical to determine detailed control-parameter values. When the control pattern suggested by the simulation is used, a grown crystal with a uniform macrostep morphology and ideal step height on the whole surface is obtained in the practical experiment.

DOI： 10.1021/acs.cgd.2c01194

Web of Science

Scopus

Fluorescence Turn-on of Tetraphenylethylene Derivative by Transfer from Cyclodextrin to Liposomes, HeLa Cells, and E. coli

Masuda, K; Omokawa, R; Kawasaki, R; Mise, Y; Ooyama, Y; Harada, S; Shinoda, W; Ikeda, A

CHEMISTRY-A EUROPEAN JOURNAL 2023年1月

Analysis of carrier lifetime in a drift layer of 1.2-kV class 4H-SiC devices toward complete suppression of bipolar degradation 査読有り

Mii, T; Sakane, H; Harada, S; Kato, M

MATERIALS SCIENCE IN SEMICONDUCTOR PROCESSING 153 巻頁： 107126 2023年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Materials Science in Semiconductor Processing

We analyzed the carrier lifetime in a drift layer of 1.2 kV-class SiC p-n diodes to suppress bipolar degradation. According to the device simulation results, the required carrier lifetime in the drift layer was estimated to be shorter than 10 ns with a current density of 300 A/cm2 if the threshold hole density for the expansion of the stacking fault at the interface of the drift layer and substrate was 2 × 1016 cm−3. Numerical analysis revealed that to ensure a carrier lifetime shorter than 10 ns, the 1/e2 lifetime obtained by microwave photoconductivity decay (μ-PCD) measurements should be shorter than 7.2 ns. Experimental μ-PCD measurements showed that 1/e2 lifetimes obtained from the as-received epiwafer were much longer than 7.2 ns, and even after H+ implantation, high-temperature annealing, or electron irradiation, 1/e2 lifetimes were still long. Therefore, carrier lifetime control in the drift layer is not sufficient to suppress bipolar degradation, and a combination of carrier lifetime control with other methods is necessary for the fabrication of 1.2 kV-class SiC p-n diodes for the complete suppression of bipolar degradation at a current capacity of 300 A/cm2.

DOI： 10.1016/j.mssp.2022.107126

Web of Science

Scopus

Prediction of operating dynamics in floating-zone crystal growth using Gaussian mixture model 査読有り

R. Omae, S. Sumitani, Y. Tosa, S. Harada

Science and Technology of Advanced Materials: Methods 2 巻 ( 1 ) 頁： 294 - 301 2022年12月

非弾性Ｘ線散乱によるルチル型酸化チタンのフォノン分散測定査読有り

原田俊太, 小坂直輝, 筒井智嗣, 田中克志, 田川美穂, 宇治原徹

SPring-8/SACLA利用研究成果集 10 巻 ( 6 ) 頁： 521 - 523 2022年12月

担当区分：筆頭著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：公益財団法人高輝度光科学研究センター

ルチル型酸化チタンにおいて酸素欠損が生じると、酸素欠損を含む面欠陥が周期的に配列するシア構造と呼ばれる構造となることが知られている。このような面欠陥の周期配列によって生じる、フォノンの分散関係の変化を調べるために、本研究では比較のために、面欠陥の周期配列を含まないルチル型酸化チタンのフォノン分散を非弾性Ｘ線散乱によって測定した。(121)方向に沿ったフォノン分散測定の結果、40 meV 以下のエネルギー領域において３つのフォノンモードを観測することができた。

DOI： 10.18957/rr.10.6.521

CiNii Research

Suppression of stacking-fault expansion in 4H-SiC PiN diodes using proton implantation to solve bipolar degradation 査読有り

Kato, M; Watanabe, O; Mii, T; Sakane, H; Harada, S

SCIENTIFIC REPORTS 12 巻 ( 1 ) 頁： 18790 2022年11月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Scientific Reports

4H-SiC has been commercialized as a material for power semiconductor devices. However, the long-term reliability of 4H-SiC devices is a barrier to their widespread application, and the most important reliability issue in 4H-SiC devices is bipolar degradation. This degradation is caused by the expansion of single Shockley stacking-faults (1SSFs) from basal plane dislocations in the 4H-SiC crystal. Here, we present a method for suppressing the 1SSF expansion by proton implantation on a 4H-SiC epitaxial wafer. PiN diodes fabricated on a proton-implanted wafer show current–voltage characteristics similar to those of PiN diodes without proton implantation. In contrast, the expansion of 1SSFs is effectively suppressed in PiN diodes with proton implantation. Therefore, proton implantation into 4H-SiC epitaxial wafers is an effective method for suppressing bipolar degradation in 4H-SiC power-semiconductor devices while maintaining device performance. This result contributes to the development of highly reliable 4H-SiC devices.

DOI： 10.1038/s41598-022-23691-y

Web of Science

Scopus

PubMed

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