研究者詳細 - 原田　俊太

Advances in defect characterization techniques using polarized light observation in SiC wafers for power devices 招待有り査読有り Open Access

Harada, S; Murayama, K

JOURNAL OF CRYSTAL GROWTH 650 巻 2025年1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 Crystal Growth

This short review provides an overview of advancements in the characterization of defects in silicon carbide (SiC) wafers using polarized light observation. SiC, which has a wide bandgap and excellent thermal and electrical properties, is widely used in power devices. However, various defects such as threading screw dislocations (TSD), threading edge dislocations (TED), and basal plane dislocations (BPD) can significantly affect device performance and reliability. Polarized light observation offers a nondestructive method for visualizing these defects and analyzing the stress fields induced within the SiC crystal structure. This paper summarizes recent developments in this technique, including the application of analyzer rotation to enhance the contrast in defect visualization. Furthermore, the development of automated systems for rapid wafer evaluation is discussed, highlighting the role of polarized light observation in improving quality control and production efficiency in SiC power device manufacturing.

DOI： 10.1016/j.jcrysgro.2024.127982

Observation of point defect and carrier lifetime distributions in hydrogen or helium ion implanted SiC PiN diodes for suppression of bipolar degradation 査読有り

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

JAPANESE JOURNAL OF APPLIED PHYSICS 64 巻 ( 1 ) 2025年1月

偏光観察によるパワーデバイスSiC基板の結晶欠陥可視化招待有り査読有り

原田俊太, 村山健太

まてりあ 63 巻 ( 10 ) 頁： 687 - 694 2024年10月

The effects of polyethylene glycol on the nucleation and growth of DNA-functionalized gold nanoparticles crystals 招待有り査読有り

Shoko Kojima, Lidong Zhang, Chandan Kumar, Hayato Sumi, Norobu Ohta, Hiroshi Sekiguchi, Kentaro Tsuzuki, Shunta Harada, Toru Ujihara, Katsuo Tsukamoto, Miho Tagawa

Journal of Crystal Growth 640 巻頁： 127740 2024年8月

Suppression of stacking-fault expansion in 4H-SiC diodes by helium implantation 査読有り Open Access

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

APPLIED PHYSICS EXPRESS 17 巻 ( 8 ) 2024年8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：Applied Physics Express

Bipolar degradation is a critical problem in Silicon carbide devices, caused by the expansion of single Shockley stacking faults (1SSFs) from basal plane dislocations. This paper presents the effects of helium implantation on the suppression of 1SSFs expansion. The fabricated PiN diodes were analyzed using current-voltage characteristics and electroluminescence imaging. The results show that helium implantation can effectively suppress 1SSFs expansion without significantly degrading diode performance. We consider that this suppression is due to the pinning of dislocations by point defects introduced during helium implantation, and the reduction of carrier lifetime may also play a role in suppressing 1SSFs expansion.

DOI： 10.35848/1882-0786/ad6be5

Modulated crystallographic shear structure in titanium-chromium oxides: their structure and phonon-transport properties 査読有り

スペクトル超解像解析によるX線光電子分光測定時間の短縮招待有り査読有り

原田俊太

Isotope News 794 巻頁： 7 - 10 2024年8月

Harada, S; Hattori, T; Inden, M; Sugimoto, S; Ito, M; Tagawa, M; Ujihara, T

JOURNAL OF APPLIED CRYSTALLOGRAPHY 57 巻 ( Pt 4 ) 頁： 1212 - 1216 2024年8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 Applied Crystallography

Advancements in phonon engineering have propelled the study of heat conduction within nanostructures, focusing on the wave nature of phonons for thermal conductivity manipulation. This work investigates the annealing-induced structural transformation of titanium-chromium oxide crystals, highlighting a role in modulating thermal conductivity through the regularization of crystallographic shear (CS) plane spacing. Utilizing high-angle annular dark-field scanning transmission electron microscopy and selected-area electron diffraction, a transformation from disordered to ordered arrangements of CS planes was observed through annealing at high temperatures. The thermal conductivity increased following annealing. The variability observed in the spacing of CS planes before annealing implies that phonon Anderson localization might play a role in the changes in thermal conductivity.

DOI： 10.1107/S1600576724006381

熱輸送のスペクトル酸化チタン自然超格子結晶の構造と熱輸送特性招待有り査読有り

原田俊太

伝熱 63 巻頁： 40 - 45 2024年7月

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

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

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

混合ガウスモデルと強化学習を用いたFZ結晶成長の自動制御招待有り査読有り

原田俊太, 土佐祐介, 大前遼, 松本遼平, 炭谷翔悟

日本結晶成長学会誌 51 巻 ( 1 ) 頁： 4 2024年4月

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

Accelerating X-ray photoemission spectroscopy measurements using Bayesian super-resolution 査読有り Open Access

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

JAPANESE JOURNAL OF APPLIED PHYSICS 63 巻 ( 4 ) 2024年4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：Japanese Journal of Applied Physics

This study applies Bayesian super-resolution to X-ray photoelectron spectroscopy (XPS), achieving up to a 20-fold reduction in measurement time while preserving data quality. Traditional XPS, crucial for surface analysis, typically requires extensive measurement durations. Our methodology significantly accelerates the process, as demonstrated with glass and Polytetrafluoroethylene samples, where we reduced measurement times by up to 1/20th without compromising spectral accuracy. This approach decreases noise levels and retains spectral integrity, offering a highly efficient solution for XPS. This innovation is particularly valuable in material science, enabling rapid, reliable surface analysis.

DOI： 10.35848/1347-4065/ad3140

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

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

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

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

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

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